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Observations on the ecology of deep-sea bottom-living fishes collected off northwest Africa (08°–27°N)
Prog. Oceanog. Vol. 9, pp. 185-244. © Pergamon Press Ltd. 1981. Printed in Great Britain
0079--6611/81/0301-0185505.00/0
Observations on the ecology of deep-sea bottom-Uving fishes collected off northwest Africa (08°--27°N) N.R. MERRETI'* and N.B. MARSHALLt
*Institute of Oceanographic Sciences, Wormley, Godalming, Surrey, U. K. t6, Park Lane, Saffron Walden, Essex, U.K. Abstract - - T h e ecology of bottom-living fishes was investigated from a series of collections off northwest Africa in the area 08°-27°N and 14°-300W from soundings of 261--6059 m. The variety of sampling gear included epibenthic sledges, a semi-balloon otter trawl, benthic traps and longlines. A total of 92 operations collected more than 4600 specimens of at least 148 species. The catches of both types of towed gear were shown to have a high degree of similarity, but sampled a different spectrum of species to the static baited gears. An overall consistency by latitude was found in the composition of the net catches. Despite possible indications of faunal boundaries at around 1100 m and 2100 m, the salient feature of an analysis of catch composition by sounding was the generally steady faunal change to a depth of about 3000 m. The only obvious discontinuity was evident at this level, beyond which the fish fauna was more uniform. This lack of marked species assemblages, characteristic of other regions, may result from the high primary productivity in the area. Features distinguishing the fish fauna of the area from that of the non-upwelling temperate western North Atlantic were found to be the smaller mean size of the dominant species, the abundance of bathygadine macrourids and the evident lack of the 'bigger-deeper' phenomenon. The relative density of fishes was estimated and shown to decrease by 2 orders of magnitude from the upper slope to 2000 m soundings. Below this the decline was less marked and relative densities of around 0.5 fish/1000 m z were maintained to at least 4000 m soundings. The abundance of slope fishes in the area was tentatively estimated to be greater than in the non-upwelling temperate western North Atlantic. Few species were abundant; only 25% were represented by more than 17 specimens. Yet the dominant family, the Macrouridae, was represented by 48% of the specimens and 18% of the species. A total of 14 species from 6 families, represented by 60 or more specimens, were examined in detail to provide information on vertical distribution, population structure, breeding biology and feeding. Niche availability and resource partitioning among cooccurring species of macrourids are briefly discussed. Station and species data are given, together with a note on the likely conspecificity of Coryphaenoides colon with C. zaniophorus.
CONTENTS Introduction Material and methods Sampling gear Treatment of samples Relative density of catch Statistical analysis of samples Limitation of sampling Results and discussion Catch analysis Analysis by latitude Analysis by sounding Analysis by species Relative density
186 187 190 192 192 193 194 196 196 196 197 201 206 185
186
N.R. MERRF"fTand N.B. MARSHAI.I
Species Account Synaphobranchidae - - Synaphobranchus kaupi Halosauridae - - Halosaurus (Halosaurichthys ) johnsonianus Macrouridae - - Trachyrincus trachyrincus
Bathygadus melanobranchus Coelorinchus coelorinchus coelorinchus Corvphaenoides (Lionurus ) carapinus Hymenocephalus italicus Nezumia aequalis Nezumia sclerorhynchus Nezurnia micronychodon Nezurnia duodecim Trachichthyidae - - Hoplostethus rnediterraneus Scorpaenidae - - Helicolenus dac~lopterus Cynoglossidae - - Symphurus nigricens Resource partitioning among macrourids Summary References Appendices Book Review INTRODUCTION
208 212 212 2/4 217 _[/
22(~ 22~ 221 224 22~ 226 22S 229 231 235 245
CONSIDERABLE ADVANCES in the study of organisms associated with the deep-sea floor have been made in recent years. Improved technology coupled with economic needs have b r o a d e n e d the scope, and increased the precision, of sampling this remote environment to encourage an extensive increase in scientific effort. Previously, knowledge of the zoogeographic and sounding distribution of fishes, their species assemblages and individual biolo,,v has largely been a byproduct of the systematic accounts of the major oceanographic expeditions. The increase in sampling intensity of deep-sea bottom-living fishes has allowed a shift in emphasis from such necessary systematic studies to preliminary ecological research. Much progress in this direction has been achieved in the western North Atlantic as a result of trawling surveys, of both a commercial (e.g. PECHENIK and TROYANOVSKII, 197(t: PODRAZHANSKAYA. 1971: SAVVATIMSKII, 1972: PARSONS, 1976) and a scientific nature (e.g. SCHROEDER, 1955: MARKLE and MUSICK, 1974: HAEDRICH, ROWE and POLLONI, 1975: MUSICK, WENNER and SEDBERRY, 1975: HAEDRICH and POLt,ONI, 1976: MUSICK, 1976: HAEDRICH and ROWE, 1077: SEDBERRY and MUS1CK, 1978), as well as through observations from submersibles (e.g. GRASSLE. SANDERS, HESSLER. ROWE and MCLELLAN, 1975: COHEN and PAWSON, 1977). Valuable complementary advances have been made in the Pacific. Time lapse photography of baits has been used to examine the role of benthic scavengers (e.g. ISAACS and SCHWARTZLOSE. 1975) and elaborate experimental trap systems used to investigate in situ respiration rates of fishes on the deep-sea floor (SMITH and HESSLER, 1974: SMITH, 1978). Recent effort in the eastern North Atlantic has been less prolific and largely dominated by exploratory commercial interest which has relied on trawling methods (e.g. MAURIN. 1968; WIllIAMS, 1968: GOI.OVAN, 1974: BAKKEN, [~AHN-JOHANNESSEN and GJOSAETER, 1975; BRIDGER, 1978). In addition various aspects of the ecology of deep-sea bottom-living fishes have
Ecologyof deep-sea bottom-livingfishes
187
been investigated also from trawl collections, such as zoogeography and sounding distribution (GOLOVAN, 1976: 1978), general biology (GOLOVAN and PAKHORUKOV, 1975: MARSHALL and MERRET'F, 1977; HUREAU, GEISTDOERFER and RANNOU, 1979), age and growth (RANNOU, 1973; 1976), reproduction (RANNOU, 1975: GEISTDOERFER, 1979), development (MERRETr, 1978) and feeding (GEISTDOERFER, 1973; 1975; DU BUIT, 1978; MACPHERSON, 1979). Sampling has also been carried out with traps and longlines. The former method has produced results on aspects of behaviour (GUENNEGAN and RANNOU, 1979), while research on zoogeography and sounding distribution (FORSTER, 1964; 1968; 1971) and feeding (CLARKEand MERRETT, 1972) have arisen from the latter. The present study arose from general biological interest in the upwelling region off northwest Africa. The samples were collected from upper slope to abyssal depths during a series of cruises within latitudes 08°-27°N spanning 8 years. A variety of aims were envisaged, of which the first is an assessment of the species diversity of the area by an assortment of samplers. Identification of specimens was facilitated by several systematic studies of previous collections in the region (KOEFOED, 1927; NYBELIN, 1957; IWAMOTO, 1970; BLACHE, CADENAT and STAUCH, 1970; MAUL, 1976) in conjunction with general taxonomic studies of selected groups. Possible variation of the catches by latitude is the next consideration, followed by an analys~s of the catches by sounding. Depth dependent faunal assemblages have been identified among fishes on both the Atlantic and Pacific slopes off America (HAEDRICH, ROWE, and POLLONI, 1975; DAY and PEARCY, 1968), which form a comparison with the situation prevailing in the area of high productivity off northwest Africa. While sampling limitations hamper inter-area comparisons of absolute catch abundance, several studies in the western North Atlantic have indicated a marked reduction in the relative density of fishes with depth (HAEDRICH, ROWE and POLLONI, 1975; MUSICK, 1976; HAEDRICH and ROWE, 1977; COHEN and PAWSON, 1977). This prompted a similar analysis among these 'Discovery' collections. Next, the abundant species are examined in more detail, centred on sounding distribution, population structure, breeding and diet. Finally, as species of the family Macrouridae dominate the samples, there is a discussion of their co-occurrence and resource partitioning. During the course of the study preliminary results were incorporated in a discussion of the existence of a benthopelagic fauna (MARSHALLand MERRETT, 1977). Also, some taxonomic problems arising from the collections have been considered separately (MARKLE and MERRETT, 1980; MERRETT, 1980).
MATERIALS AND METHODS The series of samples investigated were collected during eight cruises of RRS 'Discovery' over the period 1969-1977. Fifty-six stations were occupied in the area 08°59'-27°12'N and 14°51'-30°28'W in soundings of 261-6059 m, although most were concentrated in the slope waters off northwest Africa between 20°-27°N, east of 20°W (Fig. 1). More than one collecting gear was used on many of the stations. A total of 92 operations were carried out, 27 with an epibenthic sledge of 2.4 m2 mouth area, 24 with another epibenthic sledge of nearly 1.5 m" mouth area, 13 with a semi-balloon otter trawl of 13.7 m headline length, 3 with a rectangular midwater trawl of 8 m2 mouth-opening area, 16 by trap and 9 by longline. The full station data are given in Table 1.
188
N . R . MERRETr a n d N . B . MARSHAtA
TABLE 1. SYNOPSIS oFSTATION AND CATCH DATA (SEF.I'EX[ I~/)RGEAR NO[A FION5,
Fishing Duration
Position °N °W
Gear
Towed
2336-2336 2869-2869 3311-3311 2992-2921
2336 2869 3311 2956
30 30 30 311
4 2 3 I
6 2 4 I
3117 691/
25 33
16 21 4 3 -
154 263 10 18 -
I 7 t7 "~ I I
2 25 185 5 4 1
I 2 9 111 17 12 3 2 2 -
1 4 21 249 863 49
Station
Date
7090# 1 7091#1 71192# 1 7112#1 7810# 1 7811#1 7813#1 7814# I 7815#1 #2 7816#2
24.11.69 25. t 1.69 25.11.69 3(1, 1169
24°(11 ' 24°32 ' 25°117' 27o12 '
17°52 ' 18~'32' 19°11t' 15022 '
BN2.4 BN2.4 BN2.4 BN2.4
27.2.72 27,2.72 28.2.72 28.2.72 3.3,72
18°115.2 ' 18007.6 ' 18009.5 ' 18008.9 ' 111050.6 '
16°32.0 ' 16037.2 ' 16°38.11' 16038.2 ' 17025.5 '
BN2.4 3117-307 BN2.4 681-699 BLL 6111 (56 h o o k s ) T R A P B 578 T R A P B 612
3.3.72 4.3.72 4.3.72 4.3.72 5.3.72 5.3.72
10°50,1' 111°42.4 ' 111°44.2 , 10°43.4 ' 08°59.(I , 118058.7 '
17°25.4 ' 17~2.9' 17023.3' 17°32.2 ' 20019.8 ' 20o'20.3 ,
T R A P B 515 BN2.4 273-3119 BN2.4 271--32(I BLL 649 (57 h o o k s ) T R A P B 1153 BLL 1151 (55 h o o k s )
5.3.72 5.3.72 5.3.72 21.3.72 21.3.72 22.372 22.3.72 22,3.72 22.3.72 22.3.72 23.3.72 23.3.72 23.3.72 23.3.72 23.1t.72
08°59.() ' I18°59.(I ' 08°59.1' 21°29.6 ' 21033.0 ' 21°37.3 ' 21°39.5 ' 21°38.6 ' 21°37.9 ' 21038.3 ' 23°43.0 ' 23°42.0 ' 23°41.8 ' 23°41.6' 23°41.4 '
20°17.6 ' 20016.9 ' 2(I°16.3 , 17°39.1' 17052.4 ' 18°04.5 ' 17050.4 ' 17°5(I.3 ' 17°50.4 ' 17°51.9' 17°14.1' 17°14.6 ' 17°14.5 , 17°03.7 ' 17°04.1 '
TRAP TRAP BN2.4 BN2.4 BN2.4 BN2.4 TRAP BLL TRAP BLL TRAP TRAP BLI. TRAP TRAP
23.3,72
23°41.0 ,
17¢~14.7'
BL1,
632 (56 h o o k s )
23.3.72 24.3.72 24.3,72 25.3.72 25.3.72 25.3.72 25.3.72 25.3.72 26.3.72 26.3.72 26.3.72 26.3,72 19.7.72 21.7,72 23.7.72
23°43.3 ' 23051).5 ' 23°53,11 , 25°46.4 , 25°47.1' 25047.5 ' 25°45.0 ' 25043.6 ' 25049.5 ' 25051.7 ' 25°54.6 ' 25°54.3 ' 26°23.6 ' 25°26.11 ' 24°12.1 '
16°56.7 ' 17°05.9 ' 17~6.9' 15°57.1' 15°57.4 ' 15°58.2 ' 15°54.2 ' 15°47.9 ' 15°53,1' 16002.4 ' 15°51.8 ' 15°52.2 ' 14°51.1 ' 16°111.3' 17°07.1 ,
BN2.4 BN2.4 BN2.4 TRAP TRAP BId, BLL BN2.4 BN2.4 BN2.4 TRAP TRAP BN2.4 BN2.4 BN2.4
479-485 947.-958 1500-1504 929 976 985 (55 h o o k s ) 798 (55 h o o k s ) 486-559 933-1045 15(13-1518 1166 1102 7854,;34 890-811 1500-1521/
#5 7817#1 7822# 1 #2 #5 #6 #7 7838# 1 7839# I 7840# 1 7841#1 #2 #3 #4 7842# 1 #2 #3 7843# I #2 #3 7844# I 7845# 1 7846# I 7848# I #2 #3 7849# I 7851#I 7852# 1 7853# I 7854# 1 #2 7975 7984 799
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(Mins) Gear
Sounding (m) Range Mid-pt
~
B B
B B B B B B
B B
B B
1162 1164 12(1,'~1203 533-566 919-947 15(X1-1548 944 918 (55 h o o k s ) 898 947 (58 h o o k s ) 951 953 940 (56 h o o k s ) 614 623
. . . . . . . . . . .
~
~ ..........
~,4
Catch
Static
180 28(t 295 1811 291 296
44 47 150 330 143 3iX) 275
1203 549 933 1524
36 30 311 30 347 117 386 148 276 282
120
. . 1 1
285 228 15t) 482 952 1502
3(/ 32 31t 333 350 136 157
522 989 15111
311 29 32 31(1 23(1
814 85(1 1511/
.................
311 31t 31t
~. . . . . . . . . . . . .
~
~
....................
Spp.
...........
Nos
5 3 13 .
. I 14
3
3
14 15 4 1 2 4 3 1(1 7 14 1 4 6 7
291 153 7 1 4 6 12 121 19 85 3 22 25 12
~. . . . . . . . . . .
..........
~
189
Ecology of deep-sea bottom-living fishes
TABi.E 1 - - continued
Station
Date
7993 8001 8003 8012 8014 8020 8519#7 8521#1 #6 8524#1 #6 8528#1 8532#1 #6 8540#1 8682#5 8694#4 8930#I 8931#1 8932#2 8933#3 #4 9128#6 #10 9129#1 913l#1 #2 #3 #4 #9 #10 #11 #12 #17 9132#5 #7 9133#5 #7 9134#0 9540#0 9541#1 #3 #5 #6 #18 #19
23.7.72 24.7.72 25.7.72 26.7.72 27.7.72 27.7.72 23.6.74 25.6.74 26.6.74 28.6.74 28.6.74 2.7.74 5.7.74 5.7.74 10.7.74 7.2.75 9.2.75 30.10.75 31.10.75 31.10.75 1.ll.75 1.11.75 11.11.76 12.11.76 14.11.76 17.11.76 18.1!.76 18.11.76 18.11.76 19.11.76 19. l l . 7 6 20.11.76 20.11.76 21.11.76 24.11.76 24.11.76 25.11.76 26.11.76 26.11.76 14.4.77 15.4.77 15.4.77 16.4.77 16.4.77 18.4.77 18.4.77
* R M T closing nets
Position °N °W 24004.5 ' 22035.2 , 22°31.0 ' 20045.4 ' 20043.5 ' 20°45.l' 24002.2 , 20°46.9 ' 20"47.9' 2ff'45.5' 20044.3 ' 17038.7 ' 13047.8 ' 13048.2 ' 11015.9 ' 25033.6 ' 22°48.8 ' 25"00.5' 24058.8 , 24053.6 ' 24056.6 ' 24057.5 ' 24010.5 ' 24018.0 ' 23005.7 ' 20°17.2 ' 20014.8 ' 20010.6 ' 20008.5 ' 20018.3 ' 20°15. l' 20009.0 ' 20007.0 ' 20011.6 ' 20°50.1' 20058.8 ' 20057.5 ' 21009.0 ' 21054.6 ' 20055.8 ' 20007.0 ' 20008.1' 20016.8 , 20009.6 ' 20018.5 ' 20019.7 '
16°50.8 ' 17037.0 ' 17°20.6 ' 18002.2 , 17045.7 ' 17039.3 ' 16059.2 , 18053.4 ' 18053.4 , 22042.5 ' 22°44.4 ' 18"35.8' 18014.0 , 18"08.0' 18023.0 ' 16°40.1' 17042.4 , 16022.6 ' 16°3l.l ' 16054.7 ' 18'01.2' 17°57.1' 30°27. l' 30028.2 ' 27°58.7 , 2l°42.3 ' 21024.9' 21040.2 ' 21027.2' 21043.4 ' 2l°35.5 ' 2l°40.0 ' 21026.0' 21°37.0 ' 18°55.5' 18°59.1 ' 18013.7 ' 18°08.8 ' 18002.8 ' 18°09.6 ' 21025.3 ' 21°41.2 ' 21"30.9' 21"43.4' 21°41.2 ' 21°51.3 '
Gear
S oundi ng (m) Range Mid-pt
Hshing Duration (Mins) Gear Towed Static Spp.
BN2.4 BN2.4 BN2.4 BN2.4 BN2.4 BN2.4 BNI.5 BNI.5 BNI.5 BNI.5 BNI.5 BNI.5 BNI.5 BNI.5 BNI.5 BNI.5 BN1.5 OTSB 14 OTSBI4 OTSB14 OTSBI4 OTSBI4 BNI.5 BN1.5 BN1.5 OTSBI4 OTSBI4 OTSBI4 OTSBI4 BNI.5 BNI.5 BNI.5 BNI.5 RMT8 OTSB14 BNI.5 BNI.5 OTSBI4 BNI.5 BNI.5 BNI.5 BN1.5 OTSBI4 OTSB14 RMT8 RMT8
696--684 1457-1460 744-725 1238--1285 550-595 261-297 997-1037 3053--3058 3064--3070 4412--4412 4414-4416 3150-3155 3113-3119 2952-2958 3994-4005 3000-3000 1805-1807 501-520 955-1012 2344-2406 29802990 2962-2977 5726--5726 605%6059 5590--5590 4002--4007 3926--3927 3931-3935 386g-3879 4006-4015 3950-3952 3921-3921 3856-3861 3910-3995" 3089--3109 3083-3094 2112-2160 2130-2191 1942-1949 2005-2009 3850-3854 3910-3912 3936-3943 3929--3929 3790--4020* 3970-4044)*
30 31 30 30 29 33 47 36 31 98 76 33 39 54 37 146 32 30 64 60 60 70 10 50 42 62 54 77 115 39 43 37 39 192 82 60 47 40 36 36 34 32 86 74 360 360
690 1458 734 1261 572 279 1017 3055 3067 4412 4415 3153 3116 2955 3999 3000 1806 510 981 2375 2985 2984 5726 6059 5590 4004 3926 3933 3875 4010 3951 3921 3858 3149 3088 2136 2160 1945 2007 3852 391l 3939 3929
Nos
8 6 12 7 11 17 17 1
64 30 106 46 170 46O 269 1
1 1 4
2 2 6
1 7 4 14 24 7 6 3 1
1 9 8 241 376 8 9 3 1
5 5 3 2 1 2
19 12 7 2 2 2
l 7 II
l 18 24
4 12 3 1 1 1 6 5 1 2
9 34 4 2 1 l 45 6 1 2
190
N.R.
I
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MERRETf and N.B.
I
1
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MARSHALL
I
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~
b
r
210W
3 0 ¸¸
],,.,,
v
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CANA.~' ,S LL______~7112 ~
7853 7848 - 7849 _
~ :Z ~ - ~ _ _ _
_ _i~
8682_
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7092 . . . . . . . 8933 ~
25
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7846
:
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7
8
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5
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.................
7842 . . . . . . . . . . . . . . . . . .
3
0
~-~e932 . ~ ~
~
_ _ . L ~ 7 9 9 3 8 5 1 9
~
8003 ~ ~ - -
7845 ~f"--,-,--~.~ 7844 ~' ~7843 = ~ - . ~ ..... ~94 ~ - ~ - - - - ~ / _7841
8012 ~
~
9132 8521 8524 i o 9131 - - o 9541 - - ~ - - ~
--
-
.9128 _9129 8001
"'20
.
Z.
7991 ~ 7090
7975'
7854 ~~78,54
.......
-
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~
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~ 0
9133 9540
2
0 014
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78!.3 8528
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• t,, CAPE
--15
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VERDE I S
LEGEND •
0 -
o
501-
•
1001-
1500
•
1501-
2000
•
2001-
2500
2501-
3000
3001
--10N
500
- 3500
D
3501 - 4000
o
4001-
8540 . . . . . . . . . . . . . . . . . . 7817 . . . .
m
25
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4500
>5500
•
8532
1000
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7822 . . . . . . . . . . . . I
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Chart of the survey area with station positions indicated.by sounding range. (Arrows indicate the extent of the occurrence of strong upwelling throughout the year reported by W O O S T F R . B A ( ' K U N a n d M C L A I n , 1 9 7 6 ) .
FIG. 1.
Sampling gear The larger epibenthic sledge (BN2.4) was a forerunner of the smaller, radically modified sledge ( B N 1 . 5 ) described bv ALDRED, THURSTON, RICE and MORLEY (1976) and was superseded by the latl, ' du; ing the survey period. Both nets were designed to be general epibenthic samplers, although the BN2.4 had no blind to close off the fixed mouth opening and did not possess the elaborate acoustic telemetry or photographic facility of the later
Ecology of deep-sea bottom-livingfishes
191
design. A p a r t from the difference in the dimensions of the mouth opening of each net ( B N 2 . 4 : 2 . 4 m width x 0.8 m height vs. BN1.5:2.3 m width x 0.6 m height) the sampling efficiency of both was comparable, for they were constructed of the same combination of mesh sizes. Thus the body sections of both nets were made from 4.5 m m mesh, knotless terylene netting which was joined to codend sections of similar 1 m m mesh. Both nets t a p e r e d regularly to a diameter of 0.2 m and the whole underside and codend sections were protected by a coarse chafer net of about 10 m m mesh size. In each net the codend t e r m i n a t e d in a removable metal bucket. O t h e r similar features of importance in both nets were the double tickler chain slung across the frame anterior to the bottom edge of the net and the moulded polythene mesh covering the top and sides of the frame. The method of fishing the BN2.4 was also essentially the same as that given for the BN1.5 by ALDRED e t al. (1976), although a simple single pulse acoustic beacon was used to monitor the passage of the net in the manner described for trawling operations below. T h e semi-balloon trawl (OTSB 14), complete with " V " doors was obtained from the Marinovich Trawl C o m p a n y (Biloxi, Mississippi, U.S.A.). It was constructed of 4.4 cm stretch mesh body and 3.7 cm mesh intermediate and codend, with a 1.3 cm inner liner in the codend. Buoyancy on the headline was provided by 3 evenly spaced 25 cm CORNING glass spheres contained in polyethylene ' C a b l e m a t e ' cases. Each sphere gave a positive b u o y a n c y of 5.7 kg. Twentythree 13 × 15 cm plastic mud rollers were spaced evenly along the footrope (17 m), with three loops of 6 mm chain in between each set. A pair of sweeplines on each side separated the " V " doors by 8 m from the wing ends of the net. T h e height of the wing ends between headline and footrope was 1.5 m. The doors, each measuring 1.5 × 1 m and weighing 180 kg; were connected by bridles 50 m in length, through a swivel to the single trawl warp. T h e progress of the trawl throughout the tow was monitored from a 10 kHz acoustic beacon ( I O S T y p e H) mounted on a bracket attached to the sweepline, midway between the wing end and the door, on the leeward side of the net relative to the ship. In this orientation optimal signal strength of both the direct pulse from the pinger and that reflected from the seabed was obtained on the shipboard precision echo-sounder and displayed in real time on a M U F A X facsimile recorder. The arrival of the trawl on the seabed was observed on the facsimile display when the trace received directly from the pinger m e t the reflected pulse from the seabed and the two remained coincidental. Time on the b o t t o m was measured from this m o m e n t to that when the traces diverged once more after hauling began. The duration of the tow on the bottom was set in accordance with the sounding, from half an hour in 500 m to 1-2 hrs in 1000-4000 m (Table 1). If at any time in the duration of the tow the traces diverged, warp was paid out to settle the net on the sea floor once more. The ship speed was maintained at 2-2.5 knots (1.03-1.28 m/sec). The wing-end spread of the net was assumed to be 8.6 m, as 5/8 of the headline length while d o o r spread was estimated to be 13.3 m, on the assumption that the sweeplines were held at an angle of 17° to the direction of tow by the doors (J.P. BRIDGER, personal communication). United States Marine Fisheries Service data obtained from a similar size semiballoon trawl fitted with sweeplines of similar length and towed at a similar speed indicated that the m o u t h opened to a vertical height of 1.5-1.8 m with the footrope 0.6--0.9 m above the b o t t o m (F. WATHNE, personal communication). Experience has shown, however, that generally substrate and benthiq organisms as well as benthopelagic animals are collected, possibly as a result of uneven tension on the trawl transmitted through the warp. T h e b o t t o m traps used in the survey were of simple design and construction. Two kinds
192
N.R. MERRE'Frand N.B. MARSHALL
were used, one pyramidal in shape with a base length of 1.7 m and slant height of 1.5 m with 3 entrances (each 18 cm in diameter), the other rectangular, 0.6 x 0.4 × 0.4 m, with 2 entrances. The pyramidal traps were covered in galvanised wire netting (2.5 cm mesh). The base of one of these was covered in fine mesh fibre netting (2 cm stretched mesh) and the same materal was used to cover the rectangular trap. Each trap was baited with frozen mackerel and squid, and laid on polypropylene line (6 mm diameter) secured to a floating dhan buoy. Recovery was by means of a hydraulic M A R C O lobster power block after fishing times of 3--6.5 hr duration. T h e Iongline technique was developed from that described by FORSTER (1964). The groundline, of 6 m m diameter sisal (330 kg breaking load), was 500 m in length. Fifty or so snoods were attached to it at about 10 m intervals. Each snood was 1.5 m long with a snap-on connector at one end and a M U S T A D hook of incurved design on the other. They were made of plaited wire served with cotton thread (180 kg breaking load) with swivels incorporated 0.5 m from the hook. When shooting the longline, the ship lay-to and an 18 kg weight was attached to one end of the groundline and the latter paid paid out over the side, Baited snoods were clipped on as the groundline went out and finally the other end was connected both to a 9 kg weight and to the 6 m m polypropylene buoyline (960 kg breaking load). Five hundred metre lengths of buoyline were paid out until a scope of around 2:1 was reached, when the last length was secured to a dhan buoy. The M A R C O block was again used to haul the line.
Treatment of samples W h a t e v e r the collecting gear used, the fishes were sorted and fixed on board in 10~, seawater formalin, after preliminary identification. Ashore, the identities were confirmed and the appropriate measurements made for the species concerned (standard length (SL), total length (TL), head length (HL), gnathoproctal length (Gn.L. - - measured in a straight line from tip of lower jaw to anal opening) or snout to caudal origin - - see A p p e n d i x I), either by projection on a ruler, or by caliper, to the nearest millimetre. Body cavities were opened for gonad and alimentary examination. On microscopic examination, ovarian maturity was staged by a system of indices related to recognizable histological changes (MERRETT, 1971 - - see Table 2). Definitive stages in maturity of the testis were less easily recognized as some spermatozoa were present in almost all specimens, even m a n y of the apparently immature. Little additional evidence on the reproductive cycle could be provided by males, therefore, so the more precise staging of females was relied upon solely. Diets of the more abundant species were analysed largely from intestinal contents, necessitated by general possession of gas-filled swimbladders in these species often causing eversion of the stomach during ascent. Such analysis enabled a semi-quantitative appraisal of diet only.
Relative densi~ of catch This was estimated on the basis of area swept per tow for the epibenthic sledges and otter trawl, since all catches were considered to have been made while the net was in contact with the sea-floor (see Limitations of Sampling section). (Consequently all references to depths of capture are tacitly taken to be synonymous with the soundings fished - Cf. Species Account). The path width of the sledges was maintained by the frame of the net, while that of the trawl was taken to be the estimated wing end spread (8,6 m). The
Ecologyof deep-sea bottom-livingfishes
193
duration of the tow was timed from the arrival of the net on the bottom to the moment of lift off, observed from the M U F A X record. In this way, relative density (referred to in the Species Account simply as density) is expressed as the number of fish/1000 m 2.
TABLE2. STAGESINOVARIANMATURITY,MODIFIEDFROMMERRETT.1971
Immature virgin: Recovering spent: Yolk and chorion formation: Maturation of eggs:
Ovulation:
Spent:
Ovaries small, compact;yolk absent from oocytes. Ovaries somewhat flaccid, larger than Stage I; yolk absent fromoocytes. Ovaries firm, slightlyenlarged; yolk granules present and chorion layer forming around oocytes. Ovaries firm and distended. Eggs visible to the naked eye, opaque; yolk vesicles readily apparent, chorion fully formed. Ovaries distended to such an extent that the transparent eggs, enlarged by the uptake of liquid and freed from the chorion, are shed with or without slight pressure on the flanks. Ovaries extremely flaccid, either an enlarged but empty sac or shrunken with an enlarged central lumen.
(Stage I) (Stage VII/II) (Stage II)
(Stage III/V)
(Stage VI) (Stage VII)
Statistical analysis of samples Evaluation of the ecological data collected during this series of surveys necessitated some multivariate method of analysis. It was accepted that all such techniques now available are subject to some disadvantages. In the event, an ordination technique was chosen in which the similarities between samples, calculated in some way using the observed species abundance in each sample, could be used to provide a mapping of the samples onto some space of low dimensionality ( one or two). Obviously any such mapping would distort the inter-sample relationships to some extent, so an ordination method minimising this was chosen. Once the ordination was effected, the resulting plot of samples could be used to summarise the original data set. Hence samples with similar attributes would be close together on the ordination and dissimilar ones far apart. In this way patterns or clusters of samples could be discerned in the ordination space from which to classify the samples and hopefully to clarify the observed distributions of species within them. Initially, it was necessary to calculate a matrix of inter-sample similarity coefficients. Since these collections were obtained from a variety of non-quantitative samples it was considered inappropriate to use a quantitative similarity measure. Instead the J A C C A R D presence - absence index of similarity was chosen (JACCARD, 1912). A further complication was the large number of zeros in the original data matrix. Such heterogeneity is liable to produce misleading ordinations if the more common ordination method of principal
194
N.R. MERRETTandN.B. MARSHALl.
components is employed. FASHAM(1977) has shown by simulation techniques, however, that the method of nonmetric multidimensional scaling (KRUSKAL, 1964a and b) can cope with highly heterogeneous data sets such as these, so this method was used. Species, as well as samples, may be ordinated by the same technique, calculating a matrix of inter-species similarities before applying the nonmetric multidimensional scaling. Although both ordinations use the same data matrix, often they yield different sorts of information. Thus, as in this case, the sample ordination can often suggest determining factors for species distribution patterns, whereas the species ordination mainly defines species group or clusters of co-occurring species. Such divisions of species into groups using the two dimensional ordination plot was aided by the use of the minimum spanning tree (GOWER and ROSS, 1969). This tree was calculated from the similarity matrix and connected each species in such a way that its total length (measured in terms of species dissimilarities) was a minimum. In this way each species was connected to at least one other species with which it most often co-occurred. Thus, with the species points in the ordination connected up in the same order as in the minimum spanning tree, the resulting pattern could be used to help divide the ordination space into species groups. It also indicated the existence of such groups. For instance, if all the species were distributed evenly along a line then the minimum spanning tree would join all the species points up in a single chain to indicate that no groups could be defined.
Limitations of sampling The stations comprising the overall survey (Fig. 1) resulted from 8 cruises of 'Discovery', each of which contributed varying amounts of sampling effort (2-39 samples/cruise). The total effort was fortuitously divided into two periods by the types of gear used. On the 1969-72 cruises (52 samples), which took place during November, February-March and July, the only towed gear employed was the non-closing epibenthic sledge (BN2.4). In addition, all the static, baited gear (BLL and TB) fished was used during the earlier 1972 cruise only. Sampling during this period was concentrated in the midslope regions. In contrast, during 1974-77 when 40 samples were collected in June-July, February, OctoberNovember and April, the only gears employed were the mouth-closing epibenthic sledge (BN 1.5) and the much larger, but non-closing, otter trawl (OTSB 14). The majority of these samples were collected from soundings deeper than the slope-rise break which is close to 3000 m soundings in this area (see Table I). Furthermore, only 2 localities were revisited and sampled for seasonal variation (in degree square 20°N: 21°W (c. 4000 m sounding) and 20°N: 18°W (c. 2000 m). Hence this series of surveys comprises mostly non-seasonal spot samples, from which comparisons can only be made with tacit understanding of the imposed constraints. Certain deep-sea bottom collections have been utilized to estimate the abundance of various representatives of benthic megafauna (e.g. SCHROEDER, 1955, HAEDRICH, ROWE and POLLONI, 1975; MUSlCK, 1976; HAEDRICH and ROWE, 1977), The general limitations of such sampling and measurements of abundance were reviewed by HAEDRICH, ROWE and POLLONI(1975). They concluded that, while reasonable qualitative samples of the dominant species were obtained by trawling, the results provided an underestimate of absolute abundance. Their value was mainly in relative comparisons between samples in which the same net was used. In full agreement with these conclusions, estimates of relative density for the towed gears used during the 'Discovery' surveys have been made for bathymetric comparison within the overall study only,
Ecologyof deep-sea bottom-livingfishes
195
In detail, many of the limitations of sampling are common to all towed gears used in these surveys. While the arrival and departure time of the gear on the sea-bed was accurately known from the acoustic record and gross departures during tows were similarly monitored and allowed for, minor deviations may not have been observed. Photographic evidence has confirmed such skipping over the bottom with the epibenthic sledges (lOS unpublished data). This may result from towing speed fluctuations, which themselves may affect the catching power of the gear, especially in the case of the otter trawl. The scope of the warp (length of wire out to sounding) during fishing was variable, in the case of the OTSB 14 from 1.2-2.6, owing to the effect of surface conditions and/or current shear in the water column. Differing scope and set of the ship relative to the net rendered it impossible to determine the precise position of the net on the bottom. The sounding in which the net fished could thus only be determined from the ship's sounder, which in slope areas under adverse conditions may have recorded a depth somewhat different to the actual soundings fished. (Hence, in the Species Account the mid-point of the sounding range fished is taken as the measure of depth - - s e e Table 1). As a hydrodynamic sampler the otter trawl is subject to several anomalous factors. Door and wing end spread was not monitored while fishing, neither was headline height. Thus the effective dimensions of the net could only be estimated, although it was designed to spread approximately 2/3 of its headline measurement (=9.1 m) (S.J. MARINOVICH personal communication). Other available estimates vary, however, despite their being obtained from semi-balloon trawls of similar size and apparently rigged in the same way. For instance, MIDDLETON (unpublished report, Virginia Institute of Marine Science) measured the wing end spread of a 13.7 m OTSB 14 with 1.8 m leg-lines attached to 1.5 m x 1.0 m steel 'V' doors by readings from transducers mounted at the wing ends. At 2.5 kts the value he obtained was 6.7 m. On the other hand visual underwater observations on a similarly rigged net of the same dimensions gave a door spread of 9.75-10.4 m at about 2 kts (F. WATHNE, personal communication). Assuming the angle of the legs to diverge by 17° from the direction of tow, then the wing end spread is calculated to be 8.7-9.3 m. This is close to the value of 8.6 m, used here, derived from the factor of 5/8 of the headline length, which has been found to be the average spread under tow of most types of trawl measured (J.P. BRIDGER, personal communication). The latter value differs little in proportion from that used by BULLIS and CUMMINS (1963) on which HAEDRICH and HENDERSON (1974) based their calculations. The accuracy of this factor is probably well within limitations imposed by immeasureable variables. By fishing the OTSB 14 on a single warp, the bridles from the swivel to the doors may deflect some species from the path of the net, while the doors themselves and the sweeplines may have an opposite, herding effect. Other possibilities are the leakage of small specimens through the mesh and differential avoidance patterns. For instance in estuarine conditions the catching efficiency (percentage of fish in the path of a trawl captured) of selected species by a 6.1 m otter trawl was found to be species dependent and yet not to exceed 50%, with a standard error of 9-58% of the mean estimate (KJELSONand JOHNSON,1978). Another unaccountable variable for all non-closing nets is the depth at which specimens are collected. Evidence of the occurrence of adults of benthopelagic species far above the sea-floor and mesopelagic species close to it has been reviewed in a recent discussion on the trophic relations of slope-dwelling fishes (MARSHALLand MERRETI', 1977; see also SMITH, WHITE, LAVER, McCONNAUCHEY and MEADOR, 1979). Both the BN2.4 and the OTSB 14 collected midwater fishes in small numbers. Yet, while no check was possible on
196
N.R. MERRE'rr and N.B. MARSHALl
benthopelagic species being caught in midwater, the catches of the BN1.5 were used by analogy to assess the amount of contamination from truly midwater species. At Stns 9131 and 9541 where the OTSB 14 and BN1.5 were both fished on several occasions in soundings of around 4000 m, the OTSB 14 collected Serrivomer, nemichthyids, bathylagids, gonostomatids, searsiids, myctophids, cetomimids, ceratioids and melamphaids in small numbers in all hauls. None was collected in the BNI.5, with its blind to keep the entrance closed other than when the frame is in contact with the bottom. No comparable test was available in slope waters but, as the OTSB 14 catches of similar midwater species was not conspicuously greater over the slope, it was decided to discount all from consideration. RESULTS AND DISCUSSION
Catch analysis The total collection comprised 4671 specimens representing at least 148 species from 42 families. The overall catch data are given in Appendix I, together with the length and sounding range of capture for each species. Most species were not abundant. Only 25% were represented by more than 17 specimens (Fig. 2). While it was to be expected that the majority of specimens and species should have been collected by the more widely used towed gear, it is evident that these sampled a different spectrum of species from the static baited gear. This was demonstrated by analysis of the total number of benthic samples (78) containing the 68 species which occurred in more than one sample with the 2-dimensional ordination plot, interpreted by means of the minimum spanning tree method (see Appendix II). This separated the collections into 2 groups and also indicated, with only one exception, that the catches of the towed gears alone had a high degree of similarity and so could be considered compatible (Fig. 3). Although the total catch from traps and Ionglines constituted only about 2% of the overall collection, these gears attracted a disproportionately large number of elasmobranchs (71-77% trap and longline catch) relative to the sample taken by the nets ( < l % net catch), to account largely for the sampling dissimilarity. A total of 132 species were collected exclusively by the towed gears, and 8 species (Myxine sp. nov., Etmopterus princeps, Centrophorus granulosus, C. squamosus, Centroscymnus cryptacanthus, Scymnodon ringens, Deania profundorum and Uroconger vicinus) by baited gear alone. Eight species also (Centroscymnus coelolepis,
Deania calcea, Raja nidarosiensis, Synaphobranchus kaupi, Simenchelys parasitica, Mora moro, Trachyrincus trachyrincus and Helicolenus dactylopterus) were common to the catches of both methods of sampling. The limitation of even the relatively large otter trawl in efficiently sampling large and active species such as squaloids is amply demonstrated by these results, caused possibly by the effect of the converging bridles ahead of the net (see above).
Analysis by latitude Two of the most likely identifiable factors influencing the distribution of species throughout the survey area are latitude and sounding. To investigate these a 2-dimensional ordination of inter-sample similarities was obtained from 54 stations, sampled with towed gears only, and 61 species (Fig. 4 and Appendix II). From this the first (vertical) ordina-
Ecologyof deep-seabottom-livingfishes
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Analysis by sounding One dimensional ordination of 54 stations and 61 species (see Appendix II) shows a generally close correlation between the haul composition of the towed gears and the sounding sampled (Fig. 5). With few exceptions (one notably from Stn 8521# 1 where one specimen of an unusual species, C. (Chalinura) leptolepis, was the only catch), the catch composition altered steadily with sounding to around 3000 m. The lack of stepwise
N.R. MERRETTand N.B. MARSHALl.
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Fl~i 3. A 2-dimensional ordination of the inter-sample similarities obtained from 82 stations (sampled with various gears) and 68 species• The minimum spanning tree linkages were used to divide the stations into two groups showing the general distinction between the catch compositions of towed and static gear. distribution shallower than 3003 m is indicative of continuous, rather than intermittent, faunal change. Such results contrast with those from slope surveys carried out on both the east and west coasts o f North America where bathymetric faunal discontinuities were apparent ( D A Y and PEARCY, 1968 - - fish; HAEDRICH, ROWE and POLLONI, 1975 - echinoderms, arthropods and fish; MUStCK, 1976 - - fish; GARDINER and HAEDRICH, 1978 - - mainly echinoderms but also includes fish). In view o f these findings, the same intersample similarity matrix used in the ordination was subjected to a single linkage cluster analysis to provide a more direct comparison with those from another region of the North Atlantic. This facilitated close, but not exact, c o m p a r i s o n with the results of HAEDRICH, ROWEand POLLONI (1975) from the northwest Atlantic, south of N e w England. These authors used a slightly different clustering strategy and similarity measure to those available to us, yet the methods are sufficiently close for preliminary comparison. The catch composition of stations from south of N e w England clustered into 3 markedly dissimilar groups (Fig. 6a). The clustering divided the slope into
Ecology of deep-sea bottom-livingfishes
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FIG.4. A 2-dimensional ordinationof the inter-sample similaritiesobtained from 54 stations (sampled by towed gear only) and 61 species. The first (vertical)ordinationaxis can be identifiedwith sounding,but no correlationis apparent between latitude and the second (horizontal)ordinationaxis. shallow (141-285 m), middle (393--1095 m) and deep (1270-1928 m) faunal zones, whether all taxa were considered or fish alone. Five clusters occur among the northwest African data at an arbitrarily chosen similarity level of 3.5 (Fig. 6b). Two of these (279-1017 m (15 samples) and 1203-2160 m (4 samples)) loosely correspond to the middle and deep clusters of HAEDRICH, ROWE and POLLONI (1975). (Comparison between the two studies of any shallow zonation is precluded by the upper sounding limit of 279 m off northwest Africa). A third cluster (2136--4004 m (17 samples)) lies beyond the sampling range of HAEDRICH, ROWE and POLLONI (1975), but is in general agreement with the results of GARDINER and HAEDRICH (1978), also from south of New England. They found that little zonation occurred below 3000 m. The remaining two clusters in the northwest African data, at around 1500 m (3 samples) and between 2007-4010 m (2 samples), arise from limited catches of unusual species and probably can be considered artefacts. The clustering of samples indicated by the above analysis has been superimposed on the 1 dimensional ordination plot (Fig. 5). It should not be implied that the 3 main clusters, which incidentally incorporate only 66% of the samples, necessarily substantiate the existence of conspicuous faunal zonation. For instance, over the comparable sounding
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range there is a much greater degree of overall similarity in the cluster analysis of the northwest African samples. Moreover, the stalk lengths between adjoining clusters in the African data are much shorter than their counterparts in HAEDRICH, ROWE and POLLONI's (1975) analysis, which might indicate a greater inter-cluster similarity although such a difference could be a function of the clustering method. It is clear that these preliminary results require confirmation, but the suggestion is that, while zonation may be found shallower than about 3000 m, faunal discontinuities on the northwest African slope are less trenchant than in the temperate western North Atlantic. If this conclusion does reflect the true situation off northwest Africa, it may well be that the recent study of NICHOLS and ROWE (1977) highlights the prime cause. In a survey of the infaunal macrobenthos off Cap Blanc, Spanish Sahara, in which organic carbon and nitrogen measurements were also made, they show that "faunal communities reflect the high primary productivity in the water column (about twice that off the northeast United States) by maintaining a high biomass as depth of water (to 1830 m) and distance from the shore increase." Further they indicate that the offshore upwelling province may produce as much as or more than the near shore province. Confirmation is given by THIEL (1979; in press) at least in the 500-2000 m sounding range, by meiofaunal densities and chloroplastic pigment equivalents in the sediment which indicate high levels of organic sedimentation. Such trends may well be reflected in a reduced pressure for resource partitioning in the fish fauna which obscure marked zonation.
Ecology of deep-sea bottom-living fishes
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Analysis by species For this examination the data were selected to provide maximum information on the interrelationships of species. The more abundant species to occur in more than 2 samples from the towed gears were chosen, while the catches selected contained 1 or more representatives of at least 2 chosen species. The resultin&2 dimensional ordination of 40 species from 44 stations (see Appendix II) using the minimum spanning tree method sheds new light on the data from that given by the one dimensional ordination by sounding. Judged on the number of linkages and their separation distances, and remembering also that cross-overs indicate a third dimensional plane, two main groups can be distinguished (Fig. 7). Group I comprises the majority of species. Those of group II are more remote, with more tenuous interrelationships. Indication of this division has already been made by the change in slope in the one dimensional ordination (Fig. 5). The general orientation of the 2 dimensional ordination denotes a trend among the species which can be recognized as a bathymetric relationship, when the sounding distributions of species are plotted in JPO 9:4 - B
202
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approximately the same arrangements as indicated by the minimum spanning tree (Fig. 7). The two major groups comprise co-occurring species with related down-slope distributions (Fig. 8). Acknowledging the overlap in the bathymetric ranges of the species comprising the groups, the members of group I are essentially the upper and mid-slope fauna. Species of group II occupy the lower slope and continental rise. There is perhaps some indication of zonation among these more abundant species with possible discontinuities at around I000 m and 2000 m in concurrence with the groupings tentatively suggested by the single linkage cluster analysis of a wider spectrum of species and stations (Fig. 8). Notable among the members of group I are three species, Aldrovandia affinis, Bathypterois dubius and Gadomus longifilis, isolated from the rest (group IA - - Fig. 8). Moreover, the three samples containing these species together, from 1502-1510 m, form a distinct group in the above cluster analysis separating at the 0.5 similarity level (Fig. 6b). From the limited data available this separation may be attributable to the particularly restricted bathymetric ranges of A. affinis and G. longifilis, It is evident from Fig. 8 that a trend towards the extension of bathymetric range exists among progressively deeper-living species. A similar trend has been observed among slope fishes off the western United States (DAY and PEARCY, 1968).
Ecologyof deep-sea bottom-livingfishes
203
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GOLOVAN (1978) presented data on the composition and distribution of slope fishes collected from northwest Africa (0°-36°N - - equator to Gibraltar), augmented by a review o f the reported species from the area. The present results contrast somewhat with GOLOVAN's results from a broader latitudinal range. His findings indicate that transitional zones of species composition in soundings of 200-500 m and 2000-2600 m demarcate the slope fauna. This bathyal zone is subdivided by a further transitional zone in 1000-1300 m soundings. From the 120 species included in the upper zone, the most characteristic
t
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204
N.R. MERRETT and N.B. MARSHALL
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16 Echelus pachyrhynchus 36 Ventrifossa occidentalis 38 Symphurus nigr icens ~4 Uroconger vicinus 12 Coelorinchus c o e l o r i n c h u s 7 Bothysolea profundicota 25 Hymenocepholus italicus 2 4 Hoplostethus mediterraneus 23 HaJosaur us ovenii 40 Trachyscorpaea cristulata 10 Chaunax pictus 35 Scorpaena maderensis 9 Helicolenu s dact ylopterus 27 Laemanema laureysi 39 Trachyrinc us t r a c h y r i n c u s 3l Nezurnia aequalis 37 Synaphobranchus kaupi 19 Nezumia micronychodon 6 Bathygadus melanobr anchus 11 Cor yphaenoides zaniophor us 8 Cynoglossus cadenati 2 Alepocephalus rostrotus 33 Nezumia sclerorhynchus 21 Halosaurichthys ]ohnsonianus 30 Notocanthus bonapar tei 26 ~eptoderma rnocrops 20 dalosourichthys guentheri 32 ~lezu rnia duodecirn 15 )icrolene intronigra 4 1
18 13 29 28 22 5 3 17 34
Aldrovandia affinis Gadomus Iongifilis Coryphaenoides g0ntheri Bathyonus sp. C.(L ionurus)carapinus Halosaur opsis macrochir Bathypterois Iongipes Bathytyphlops sewelli Conocara salmoneo Rinoctes nasutus
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F'I~; ~. Sounding ranges of species used in the 2-dimension ordination of inter-species similarities in Fig. 7. Species are arranged in the approximate order given by the minimum spanning tree linkages. Grouping in Fig. 7 indicated on the right.
GOLOVAN considered to be 3 scyliorhinid, 11 squaloid, 6 searsiid, 4 congrid, 5 morid, 14 macrourid and 3 trachichthyid species. He placed a further 101 species in the lower zone, among which alepocephalids displayed the greatest diversity and biomass (e.g. see GOLOVAN, 1974). The dominant families in the 150 or so species from the present series of surveys are the Macrouridae, represented by 26 species, the Alepocephalidae, (12), the Ophidiidae (9), Squalidae, Halosauridae and Chlorophthalmidae (8 each), and Synaphobranchidae (6). In terms of the most abundant species considered in the 2 dimensional ordination above (Fig. 7), all species in group I, apart from A. affinis and G. longifilis in group IA, were encountered by 1000 m soundings. A single member of group II, Bathyonus sp., had an
Ecologyof deep-sea bottom-livingfishes
205
upper limit of distribution shallower than 1000 m soundings. So, macrourids dominated with 10 species represented, followed by halosaurs and scorpaenids (3), and alepocephalids, ophidiids and cynoglossids (2). In group II only Halosauropsis macrochir, C. (Coryphaenoides) gfintheri and C. (Lionurus) carapinus occurred within the 1300-2600 m zone designated by GOLOVAN (1978). The contrast in relative dominance of the Macrouridae and Alepocephalidae between the two studies is notable, especially from the lower slope. Gear selectivity and the latitudinal ranges sampled ((08°-) 18°--27°N versus 0°-36°N) may largely account for these differences (see below). GOLOVAN (1978) pointed out that there is a regular decrease in bottom temperature over the slope from north to south. This affects not only vertical but geographic distribution. South of Cape Verde (14°45'N) the vertical limit of the transition between upper and lower bathyal zones is displaced upwards as a result of upwelling. The present collections were concentrated to the north of Cap Blance (20°46'N - - Fig. 1), so it is unlikely that this feature should have been revealed. In this connection it is notable that, among fishes of the shelf and upper slope (to about 600 m soundings), MAURIN (1968) "recognized a faunal boundary at the approximate latitude of Cap Blanc. This separated essentially tropical species from those of a more northerly fauna. It is of interest to compare the species composition from the region of upwelling in the eastern North Atlantic with that from the non-upwelling area of the temperate western side of the North Atlantic. COHEN and PAWSON (1977) state that the species diversity of the benthic slope fish fauna of the latter area is 100 or more species. Furthermore, they point out that more species are seen or photographed from submersibles than are caught in trawls. This observation and the results of the literature review by GOLOVAN (1978) indicate that the 150 or so species collected in our survey must fall considerably short of the total. Hence, the species diversity off northwest Africa is likely to be about twice that from a similar sounding range in the temperate western North Atlantic, a trend found commonly between tropical and temperate communities from other marine habitats (cf. MOORE, 1972). Another difference between the two areas is evident in the mean size of the dominant species collected in medium-sized nets. Those species from the northwest African regions are generally smaller than their counterparts in the temperate western North Atlantic. For instance, there are 11 species centred in the upper 2000 m soundings (Group I - - Fig. 8 and Appendix I) represented by >100 specimens in our collections (Synaphobranchus kaupi (169 specimens), Halosaurichthys johnsonianus (523), Bathygadus melanobranchus (407), Hymenocephalus italicus (293), Nezumia aequalis (381), N. sclerorhynchus (101), N. micronychodon (163), N. duodecim (427), Hoplostethus mediterraneus (430), Helicolenus dactylopterus (170), Symphurus nigricens (174)). In contrast, the dominant species in the upper 2000 m of slope in the temperate western North Atlantic are evidently (also in phylogenetic order) Synaphobranchus kaupi, Alepocephalus agassizii GOODE and BEAN, 1883, Phycis chesteri GOODE and BEAN, 1878, Merluccius albidus (MITCHILL, 1818), Dicrolene intronigra, Lepophidium cervinum (GOODE and BEAN,. 1886), Coryphaenoides rupestris GUNNERUS, 1765, Nezumia bairdii (GOODE and BEAN, 1877), Antimora rostrata GI]NTHER, 1878, Lycenchelys verilli (GOODE and BEAN, 1877), Helicolenus dactylopterus, Citharichthys arctifrons GOODE, 1880, and Glyptocephalus cynoglossus (LINNAEUS, 1758) (MARKLE and MUSICK, 1974; HAEDRICH, ROWE, and POLLONI, 1975; MUSICK, WENNER and SEDBURY, 1975). Thus the species composition of the dominant forms in the western North Atlantic is largely different, in addition to the larger mean size attained. It is notable that the bathygadine group of
206
N.R. MERRETTandN.B. MARSHALL
macrourids, which are abundant in the upwelling region, are absent in the temperate zone. T h e r e is a more trenchant difference between the two regions in the fauna from soundings greater than 2000 m. Coryphaenoides (Nematonurus) armatus is the dominant species of the continental rise in the temperate North Atlantic (MUSICK, WENNER and SEDBURY, 1975; COHEN and PAWSON, 1977), constituting as much as 80% of the fish biomass there (HAEDRICH and ROWE, 1977). The species was represented by only 4 specimens in these collections from the upwelling region. Although the dominant species below 2000 m off northwest Africa C. (Lionurus) carapinus (62 specimens) seems to occupy a similar niche in both areas (cf. HAEDRICH and POLLONI, 1976), there appears to be no counterpart of the large and ranging C. (N.) armatus. Hence, in the northwest African area it would seem that the 'bigger--deeper' phenomenon (MUSICK, 1976: HAEDR1CH and ROWE, 1977), in which mean fish size increases with sounding, does not apply. Possibly its absence may be correlated with the same selective pressures which cause the predominance of small fish on the slope. In his study of metabolism by in situ measurement, SMITH (1978) showed that C. (N.) armatus is a species adapted to the deep-sea by having a low metabolic rate and storing sufficient energy to exist for extended periods without eating. Thus by analogy large size may be adaptive to other food-limited conditions, such as occurs cyclically in regions of marked seasonality. For instance, in the temperate western North Atlantic large mean size with sufficient nutrient storage capacity to tide fish over periods of food shortage could be expected at all depths. Conversely, if conditions remained similar throughout the year with uniformly high productivity, selection may favour species of a small mean size with a smaller capacity for nutrient storage which otherwise have a greater competitive ability to exclude C. (N.) armatus on the continental rise. Conditions such as these apparently prevail off northwest Africa, at least between 20°-25°N where the majority of our samples were collected and where strong upwelling occurs throughout the year (WOOSTER, BACKUN and MCLAIN, 1976).
Relative density Estimation of the relative density of fishes from these collections provides a basis for comparing abundance from different bathymetric levels of the area surveyed (see Limitations o f sampling). The results in terms of relative abundance per 1000 m e are given in Fig. 9, for the epibenthic sledges and otter trawl respectively. The catches on the upper slope were close to I00 fish/1000 m'-', but they declined exponentially with depth to about two orders of magnitude lower in soundings of around 2000 m. Deeper than 2000 m the decrease in relative density was less marked and was maintained around 0.5/1000 m 2 at least to 4000 m soundings. (The high catch per unit effort in 5700 m from the BN1.5 can be explained from the capture of a single fish from a tow of very short duration - - Table 1). Such a decrease in relative abundance is in general agreement with trawling results and submersible observations from the middle Atlantic slope of the USA (HAEDRICH, ROWE and POLLONI, 1975; MUSICK, 1976: HAEDRICH and ROWE, 1977; COHEN and PAWSON, 1977). This inverse correlation between abundance and depth agrees with patterns indicated by the macrofauna (ROWE, POLLONI and HORNER, 1974) and to a lesser degree by the meiofauna (THIEL, 1975). Despite earlier remarks (p. 194) on the danger of comparing estimates of absolute abundance from one area to another when collected by different gear, there is reason here to draw some tentative conclusions by analogy with results from the western North
207
Ecology of deep-sea bottom-living fishes
v
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FIG. 9. Relative density of total catches made by the towed gears plotted against the mid-point of the sounding
range sampled.
Atlantic. HAEDRICH, ROWE and POLLONI (1975 - - Table 7) show that more individuals are seen from submersibles than are caught by nets. At around 1000 m the estimate of abundance calculated from photographs was two and six times greater than that estimated from catches o f a 12.2 m and a 4.8 m semi-balloon trawl, respectively. With this in mind, the abundance o f fish down the slope off northwest Africa (Fig. 9) is found to be much the same as that calculated from photographic series taken from a submersible by HAEDRICH and ROWE (1977 - - Table 1) in 497-278 m soundings in the temperate western North Atlantic. H e n c e , it is probably safe to assume that slope fishes off northwest Africa are m o r e abundant than in the latter area, and that the greater productivity induced by upweiling along the African coast is responsible for this difference. Regrettably the fresh weight o f catches was not recorded in the present survey with which to compare biomass from the two areas.
208
N.R. MERRETrand N.B. MARSHALl.
Although not comparable with the results from the towed gear, catch per unit effort has been calculated for the longline operations on the basis of catch per hook hour (Table 3). O v e r the 9 operations (55-58 hooks/operation) the mean catch was found to be 0.04 fish per hook hour weighing 0.15 kg per hook hour. T A B L E 3. C A T C H PER UNIT EFFORT (kg AND NUMBERS/HOOK HOL1R} FOR BOVI'OM LONGI.INE OPERATIONS
Stn. 7813# 1 7843#3 7817# 1 7849# 1 7841#2 7842#3 7841#4 7841#3 7822#2
~ 601 632 649 798 918 94(1 947 985 1151
6 56 56 57 55 55 56 58 55 55
~ .=_. ~ E
Catch WI.
No.
180 150 150 157 117 120 148 136 143
13.1 13.5 12.11 47.0 27.5 33.4 311.5 4.7
10 3 5 12 5 0 13 6 1
~ ,~ !).08 0. Ii1 [).()8 0.33 0.26 o.23 IL24 0.04
6 ,-
0.116 I).112 0.04 11.08 0.115 11.119 0.115 (].ill
Species account Some ecological aspects of the relatively abundant species were examined. Those species represented by 60 or more individuals were chosen and totalled 14 only of the 148 species collected. Consequently, one species each of the families Synaphobranchidae, Halosauridae, Trachichthyidae, Scorpaenidae and Cynogiossidae are considered here, together with 9 species of the family Macrouridae. All but one of these are slope dwellers, the majority being most abundant in soundings of less than 1000 m.
SYNAPHOBRANCHIDAE
Synaphobranchus kaupi According to the submersible observations of COHEN and PAWSON ( 1 9 7 7 ) S. kaupi is a benthopelagic species which swims above or along the bottom or may hover at any angle, head up or down. It has a capacity to reverse its forward swimming rapidly, which led them to conclude that it may easily avoid capture by towed nets. Such evasion might explain the fact that S. kaupi was never very abundant in catches (maximum density 6 fishtl000 m" - Fig. 11), although it was the most ubiquitous slope-dwelling species collected. Yet the greater relative abundance of this species to the north, collected with the same gear (IOS unpublished data), suggests that these values probably reflect true proportional abundance. A total of 169 specimens were taken in 21 samples spanning a range of 482-2160 m (Appendix I and Fig. 11). From the same general sampling area GOLOVAN (1978) reported this species from the range 90101700 m. On the western side of the Atlantic, HAEDRICH, ROWE and POLLON111975) found S. kaupi to be most abundant in soundings
209
Ecology of deep-sea bottom-living fishes
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FI(; l 1. Sounding distribution (shaded) of some of the more abundant species sampled on the slope by towed gears ( ---, indicates OTSB 14 samples). Relative density indicated as in Fig. 10, o f 3 9 3 - 1 0 9 5 m and it was also the top ranking species observed by MARKLE and MUSICK (1974) at 900 m. From the present results its abundance is apparently not concentrated in any part of its vertical range. It is generally less abundant, h o w e v e r , than on the slope to the north o f the Canaries off M o r o c c o (IOS unpublished data). The samples reported here c o v e r the size range 91-605 m m SL and length-frequency analysis suggests a 5 - p e a k e d distribution (Fig. 12). Most s p e c i m e n s were in the 200-300 m m SL size range and found to
Ecologyof deep-sea bottom-livingfishes
211
be sexually immature. Beyond occasional observations, however, gonad examination was not undertaken for this species. Preliminary investigation of the diet of S. kaupi was made from 14 stomach contents (Table 4). As previously noted it feeds largely on pelagic items (MARSHALL and MERRETT, 1977) which agrees with findings from collections made o f f t h e eastern United States by MUSICK, WENNER and SEDBERRY (1975) and SEDBERRY and MUSICK (1978). Fish remains were the main component and occurred in 71% of the stomachs. Identification of these remains was possible in only 2 instances. One was a myctophid, while the other was the skull of Macrorhamphosus scolopax. The latter occurred in a sample from 952 m sounding in which a free adult of this species was also taken. In addition, some of the fish remains were parts of larger individuals than apparently could be eaten whole by the predator. Such occurrences suggest a scavenging role in this species (cf. CLARKE and MERRETT, 1972). Crustacean remains, mainly decapod, were the next most abundant food item found in 29% of the stomachs. Squid were almost as abundant, apparently Rossia type (N. MacLEOD personal communication), found in 21% of stomachs. One stomach contained chaetognath remains. Synaphobranchus kaupi
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FIG. 12. Synaphobranchuskaupi (Standard) length-frequencydistributionof the total sample (n = 167).
2 l -~
N.R. MERRE'rr and N.B. MARSHAI.I
HALOSAURIDAE
Halosaurus ( Halosaurichthys ) johnsonianus This species was the most abundant halosaur in the collections (523 - - Appendix I). although largely due to its presence in high density at 2 of the 8 stations at which it was sampled (27 and 100 fish/1000 m'). Its depth distribution indicated that it is a mid-slope species, most abundant around 1000 m but extending from 690-1524 m soundings (Fig. 11). The overall size range was 67-174 mm Gn.L. and the length-frequency distribution suggests at least 2 major peaks (Fig. 13). No size-depth dependence was evident throughout the sounding range. The population was largely immature and the onset of ovarian maturity (stage I1) apparently occurs at around 105-110 mm Gn,L. Running ripe females (stage VI) were found in the 120-130 mm Gn.L. group and a spent female in the 125-130 mm group, giving an indication that this is the approximate size of first maturity. The overall sex ratio shows a preponderance of females (ld' : 2.3 !0). Accepting the inadequacy of seasonal coverage, it is notable that the running ripe (stage VI) and recovering spent (stage VII/II) fish were all caught in June. An indication of the feeding strategy was gained from the analysis of 5 stomach contents of fish within the range of 100-120 mm Gn.L. and noted in MARSHAl, It and MERRETr (1977). This indicated that copepods were the dominant prey (in 3 stomachs), while a m p h i p o d s and polychaetes were found in one stomach each (Table 4). No sediment was found in the alimentary tracts. MACROURIDAE
Trach vrincus trachyrincus The collections contain 98 specimens of this species, distributed in soundings of 4821017 m (Appendix I, Fig. 10). In catches off northwest Africa, GOLOVAN (1978) found that the lower limit of distribution of this species varied somewhat with latitude, but had an overall range of 450-1700 m. GEISTDOERFER (1975) gives 400--1500 m as the vertical range for this species in the eastern North Atlantic, including the area in question. Although never abundant among the 'Discovery" samples T. trachyrincus occurred in densities of 1-7 fish/1000 m" from 550-950 m. The overall size range was 7-155 mm HL. T w o peaks are apparent in the length-frequency distribution: one of sexually indeterminate adolescents (30-40 mm H L ) and another broader one of adults (80-110 mm H L - Fig. 14). T h e r e was no evidence of any size-depth dependency from the samples. The sex ratio of the adults examined was 1 ~ : 1.4 9. No ripe females were found, but the indication from the 30 females examined was that onset of ovarian maturity occurred at about 71-75 m m H L , while the smallest recovering spent female showed that spawning had taken place by 106-110 m m HL. T h e diet of T. trachyrincus was investigated mainly from examination of intestinal contents and noted by MARSHALL and MERRE'rr (1977). O f the 16 fish examined (79155 m m H L ) the stomach contents of only 3 were intact, owing to eversion under pressure from the expanding swimbladder. In terms of presence or absence, crustaceans (69%), polychaetes (44%), fish (38%) and squid (31%) were the dominant food organisms (Table 4). Sediment occurred in 44% of the intestines examined which, together with the relative
Ecology of deep-sea bottom-living fishes
213
Ha Iosa ur us ('Ha Iosa uric ht hys ) j o h nso n ia n us
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LENGTH
GROUPStSmm)
FIG. 13.
Halosaurus (Halosaurichthys)johnsonianus.
(Gnathoproctal)
length-frequency
sample,
w i t h s e x e s a n d o v a r i a n m a t u r i t y s t a g e s i n d i c a t e d ( n = 523. " U n s h a d e d a r e a = s e x u a l l y i n d e t e r m i n a t e -
distribution of the total
specimens).
abundance of polychaetes, confirmed the extent of benthic foraging in T. trachyrincus. Thus these results suggest that the marked preference for pelagic food claimed by GEISTDOERFER (1975) and MARSHALL and MERRETT (1977) requires modification to emphasise the mixed nature of the diet indicated by MCLELLAN (1977) and MACPHERSON (1979).
214
N.R. MERRETT and N.B. MARSHALL
Trochytincus
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trachyrincus
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GROUPSC10mm)
Trachyrincustrachyrincus(Head) length-frequency distribution of the total sample, with sexes indicated (n = 98. Unshaded area as in Fig. 13).
Bathygadus melanobranchus T h o u g h one of the most numerous species in the collections (407 - - Appendix I), B. melanobranchus occurred in only 7 catches. This may be attributable to the narrow depth range it was found to occupy (734-1017 m), yet within this it was caught in densities of up to 21 fish/1000 m" (Fig. 10). GOLOVAN (1978) also found this species to have restricted vertical range in the area (500-1200 m from 09°-3 I°N), which contrasts superficially with that given for the Atlantic as a whole (450-2600 m) by MARSHALl, (1973), but he points out that it is centred in 700-1400 m. The overall size range in the 'Discovery" samples was 7-84 m m HL. As might be expected from its restricted sounding range, there was no suggestion of a size-depth relation. The major peak in the length-frequency distribution (45-63 m m H L - - Fig. 15) is dominated by males (3.36 : 19), accounted for by a disporportionately large number from one haul (7.76 : 1 ?). The sexes are discernible macroscopically by 30 mm H L and the earliest sign of ovarian maturation (stage II) was o b s e r v e d by 51 m m HL, while the smallest spent, fish were observed in the 57-60 mm H E .croup. The spent females were collected in March. The prominence of the mysid, Gnathophausia zoea WILLEMOES-SUHM, 1875, and chaetognaths in the intestines of B. melanobranchus from these samples has been noted previously (MARSHALLand MERRETT, 1977 - - Table 1). The results of the examination of a further 18 fishes have now been added to the 23 already reported (Table 4). The d o m i n a n c e of G. zoea remained unaltered and was present in 51% of the fish examined. Up to 3 G. zoea per stomach were found and all were in the carapace length range 20-23 m m . C o p e p o d s were the second most frequent food item (46%,) found and the mean abundance in stomachs containing them (11) was 5.5. Overall chaetognaths were found to be of rather lesser importance (in 22% of fish examined). The low percentage of intestines
215
Ecology of deep-sea bottom-living fishes
containing sediment coupled with the pelagic nature of the identified prey serves to confirm the pelagic feeding pattern already indicated of bathygadines in general (e.g. MARSHALL and BOURNE, 1964; OKAMURA, 1970; MCLELLAN, 1977) and B. melanobranchus in particular (GEISTDOERFER, 1975; MARSHALL and MERRETI', 1977). There was no evidence to suggest that the composition of the diet altered with the size of predator over the size range examined (22--64 mm HL).
Bathygadus
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l q o 15. Bathygadus melanobranchus. (Head) length-frequency distribution of the total sample, with sexes and ovarian maturity stages indicated. (n = 402. Unshaded area as in Fig. 13).
216
N.R.
MERRETTand
N.B.
MARSHAL[.
Coelorinchus coelorinchus coelorinchus
A total of 66 C. c. coelorinchus were collected from 6 stations, although 59 of these were caught at only 2. The maximum density encountered was 10 fish/1000 m" (Fig. 10). All catches were made on the upper slope within the range 279--572 m, somewhat shallower than the 320-1100 m range reported by GOLOVAN (1978) from 18°-31°N. The overall size range 13--69 mm HL, (Appendix I) lacked any indication of a size-depth dependence. The sex ratio from all the samples was close to parity, namely 1 Q : 1.26. In the total collection there was a peak which consisted of juvenile sexually indeterminate specimens, 12-27 mm HL (Fig. 16). A secondary peak of males and immature females (stage I) occurred between 30 and 39 mm HL. Maturing females were found above this size, with 2 recovering spent individuals in the 42-45 mm HL group to indicate that breeding takes place at least by this size. Such evidence as there is on seasonality of gonad maturation suggests that breeding occurs in the early part of the year, from females obtained with maturing ovaries (stage Ill/V) in February-March and only immature (stage I) or recovering spent (stage VII/II) females in July. An insight into the diet of this species resulted from the analysis of intestinal contents of 2 specimens (Table 4). The mixed food found, ostracods and amphipods in both with, in addition, polychaete and fish remains in one each contrasts somewhat with the benthic diet reported by GEISTDOERFER(1975) (see MARSHALL and MERRETT, 1977). The epifaunal nature of the diet has also been reported by MACPHERSON (1979) for this species in the western Mediterranean.
Coelorinchus coelorinchus coelorlnchus
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FI(;. 16, Coelorinchus coelorinchus coe/orinch~. (Head) length-frequency distribution of the total sample, with sexes and ovarian maturity stages indicated (n = 65. Unshaded area as in Fig. 13).
Ecology of deep-sea bottom-living fishes
217
Coryphaenoides (Lionurus) carapinus This species was widespread, but not abundant, in catches from soundings below 2000 m, with 62 specimens collected from 16 stations (range 1524-4004 m, Appendix I). The maximum density per 1000 m 2 was 1.5 from 3911 m sounding, although a subsidiary peak of 1.1 fish/1000 m" occurred in 2136 m. This may be compared with the depth range of 1200-2800 m for the species in the western North Atlantic, off sourthern New England (39°N), with a maximum density of 2.4 fish/1000 m" in 1768--1960 m (HAEDRICH and POLLONI, 1976). The size range found off northwest Africa was 12-54 mm HL (Appendix I). Many of the specimens were badly damaged in the net, so that little information could be obtained from an overall examination of sex and gonad maturity. A length-frequency analysis indicated an abundance peak at 36-45 mm HL (Fig. 17). These specimens were all captured from soundings of around 4000 m, while those fish of head length <21 mm were caught shallower at soundings <3000 m. This suggestion of a size-depth relationship corroborates the more substantial data of HAEDRICH and POLLONI (1976). Earlier in their life history the pelagic larvae of this genus undergo an ontogenetic migration down from the near-surface waters of the open ocean to the sea floor (MERRETI', 1978). No intestinal examination was attempted because of the high proportion of damaged individuals. HAEDRICH and POLLONI(1976), however examined the diet of a large sample of this species and found that it relied more on truly benthic animals than do other Coryphaenoides and had a preference for amphipods and ophiuroids. Cot yp hoe
noides
( L i o n u r u s ) c a r a p i n us
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GROUPS(3mm)
FIG. 17. Coryphaenoides (Lionurus) carapinus. (Head) length-frequency distribution of the total sample (n = 52).
Hymenocephalus italicus Six samples only contained the total 293 specimens collected throughout the surveys from a sounding range of 291--690 m (Appendix I). To the south, in the Gulf of Guinea, IWAMOTO (1970) found H. italicus restricted to soundings shallower than 500 m, although to the north of the present area along the northwest African slope (27°-31°N), GOLOVAN (1978) recorded it from a much broader range (340-1400 m). Maximum densities of 24 and JPO 9:4 - O
2 18
N.R. MERRETrand N.B. MARSHAt,L
26 fish/1000 m ~ occurred in the two 'Discovery' catches containing most fish (Fig. 10). The overall size range was 8-36 mm H L and the length-frequency distribution was unimodal (Fig. 18). The majority of juveniles occurred in the shallower of the two numerous catches (296 m sounding, Fig. 10), but some were also present in deeper tows. So, there is a need for further evidence on any possible size-depth relationship. The sexes could be reliably distinguished by the 16-18 mm H L group and showed a preponderence of females in the total collection (16 : 1.5 9 ) by 18-20 mm H L these females had entered their first oogenic cycle (Fig. 18), yet no female examined had ovaries in advance of the growth phase (Ill/V) of maturation. Most samples were collected in March, but both the July and October collections had representatives in the stage III/V condition. The diet of this species was investigated from the stomach contents of 4 and intestinal contents of 9 individuals in the size range 19-29 mm H L (MARSHALL and MERRETT, 1977 and Table 4). Crustaceans - - copepods, euphausiids and decapods - - were the most abundant organisms in these fishes. The euphausiids present were of particular interest in that Hymenocephalus
italicus
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Ecology of deep-sea bottom-living fishes
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they were identifiable as Euphausia hanseni Z I M M E R , 1915 and Nemato~:elis megalops ( G . O . SARS, 1883), both mesopelagic diurnal migrators. This preference for pelagic food was noted by MARSHALL and MERRE'IT (1977), confirming the results of a larger sample given by GEISTDOERFER (1975). Both MACPHERSON (1979) and MCLELLAN (1977) presented similar evidence.
Nezumia aequalis As one of the more common macrourids caught, N. aequalis was represented by 381 individuals from the sounding range 307-1524 m, although it was centred in the upper slope region, 307-950 m (Appendix I and Fig. 11). The overall range compares favourably with that given by GOLOVAN (1978) of 320-1620 m from the overlapping area 09°-3 I°N. In the 'Discovery' collections it was present in 15 samples, with a maximum density of 33 fish/1000 m ~ from 550 m sounding (Fig. 19). The total size range was 11-56 mm HL, with a broad peak in length frequency distribution at 20-40 mm H L (Fig. 19). The juvenile elements of the population (<20 mm HL) were not numerous and were present in samples down to 1000 m, indicating a lack of marked size-depth dependence. Among adults, the overall sex ratio was close to parity, 19 : 1.4<3. Females were entering their first oogenic cycle by 22-24 mm HL. While none was found to be in a running ripe condition, the smallest recovering spent fish (stage VII/II) was in the 38--40 mm H L group which indicates at least 2 maturation cycles in the life history. Females in the growth phase of maturation (III/V) were present in samples from February through to October giving little evidence of marked spawning seasonality. MARSHALL and MERRETT (1977) in summarizing their observations on the diet of 44 specimens concluded, in agreement with GEISTDOERFER (1975) and MACPHERSON (1979) that this species depended on a mixed diet of pelagic and benthic organisms. Their data, excluding pooled intestinal contents from 30 specimens, is presented in detail in Table 4 together with the analysis of a further 38 specimens. Copepods (in 90% of the fish examined) and polychaetes (54%) were the most frequently found food items, followed by mysids (21%) and amphipods (15%). The mean number of copepods from stomachs in which they were found was 12.5.
Nezumia sclerorhynchus Whereas this species was present in only four samples, a single catch yielded 85 of the total of 101 specimens (Appendix I). This catch (23 fish/1000 m 2) was made in a sounding of 690 m (Fig. 20), which coincided with the centre of abundance of the species as a whole of 457-731 m given by MARSHALL and IWAMOTO (1973b) and at 500-800 m for Mediterranean representatives by RANNOU (1976). The present data show the sounding range to be 522-1203 m. The overall size range is 16-50 mm H L with 3 peaks in the lengthfrequency distribution at 16-20, 26-36 and around 42-50 mm HL. This distribution in general agrees with an analysis of a larger sample from the Mediterranean by RANNOU (1976). He established a growth curve on the basis of otolith readings, which implies that the peaks in the present data correspond to fish of around 7, 10 and 20+ years old. The few sexually determined specimens suggested that sexual maturity might be attained at 3040 mm H L (Fig. 20), corresponding to 11-20 years old (RANNOU, 1976). The largest specimen caught (50 mm HL) was the only one in a recovering spent condition. Stomach contents could only be found in 12 specimens and analysis of these is given in Table 4. Copepods were found in 6 specimens with a mean number per stomach of 1.3.
221
Ecology of deep-sea bottom-living fishes
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Polychaetes were the next most frequently occurring organism (4 specimens). Small though the sample is, it is evident that N. sclerorhynchus has a mixed diet of benthic and pelagic prey which is in agreement with the extensive survey undertaken by GEISTDOERFER (1975).
Nezumia micronychodon One thundred and sixty three individuals occurred in 7 samples collected between 549-1261 m soundings (Appendix I and Fig. 11). This corresponds with the depth range of the species from the Gulf of Guinea (IWAMOTO, 1970), although GOLOVAN(1978) caught N. micronychodon at 22°N off the northwest African slope in 1620 m. The highest densities in the 'Discovery' collections, however, were in the 2 shallowest catches, in 549 and 572 m (22 and 16 fish/1000 m" respectively) where the majority of juveniles occurred. With a size range of 23--66 mm HL this was the largest Nezumia species encountered. The length-frequency distribution was composed of a large peak of immature unsexed fish (24-32 mm HL) (Fig. 21). Onset of ovarian maturation was not apparent until 44-46 mm
222
N.R. MERRE'VI"and N.B. MARSHALL Nezumia s c l e r o r h y n c h u s
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HL and no fish in the growth phase (Ill/V) were caught. Three of the 4 largest fish caught were recovering spent females. The sex ratio among the sexed fish showed a preponderance of females, 1 c~ : 3.6 9. The diet of N. micronychodon was investigated from the stomach and/or intestinal contents of 30 specimens, which included the 6 reported by MARSHALLand MERREI~ (1977). Overall the species depended largely on polychaetes (90%) and a variety of small crustaceans (Table 4). Sediment, both free and in the form of faecal pellets, was present in 90% of the fishes investigated, to indicate a dependence on infaunal prey. Larger specimens, however, evidently process a greater amount of substrate than do the smaller ones, as they contained relatively more sediment and a higher proportion of polychaetes, usually small tubicolous forms. Specimens of less than 30-40 mm HL fed more on epibenthic organisms. Their diet was largely crustacean and dominated by copepods. The copepods were practically all Aetidopsis carinata BRADFORD, 1969 and were all males, which is unusual because the species is known almost exclusively from females captured in midwater (H. S.J. ROE, personal communication).
Nezumia duodecim The presence of N. duodecim in these collections extends the known range of the species from the Gulf of Guinea northward to 24°N on the northwest African slope (see IWAMOTO,
223
Ecologyof deep-sea bottom-livingfishes
1970). It was the most numerous macrourid collected, although it occurred in only 4 samples (Appendix I). Its abundance was due to a single catch of a density of 103 fish/1000 m 2 from a sounding of 933 m (Fig. 11). Its sounding range of 690-1261 m was somewhat d e e p e r than its occurrence in the Gulf of Guinea (329-960 m, IWAMOTO, 1970). T h e size range sampled was 8-48 mm HL, which embraced a large proportion of immature fish. T h e length-frequency distribution indicates a major peak of immature specimens (20-34 mm H L ) and a secondary one (36-44 mm HL) containing maturing females (Fig. 22). A m o n g adults the sex ratio was found to be 19 : 1.3~. Evidently the onset of ovarian maturity occurs at a size of 30 mm HL, while one female of 44 mm H L was in the recovering spent condition (VII/II). T h e diet of this species has been analysed from the intestinal contents of 60 specimens (Table 4). As in other Nezumia species examined copepods (80%) and polychaetes (62%) were present in the highest proportions in specimens examined. Indeed, the 45 undamaged stomachs investigated contained a mean number of copepods of 69. Considering the diet as a whole, including the small amount of fish remains, it is clear that N. °duodecim, like the majority of macrourines, depends on a mixed diet of benthic and pelagic organisms (see MARSHALL and MERRETF, 1977). 40 ~
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224
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TRACHICHTHYIDAE
Hoplostethus mediterraneus This species has been shown to be widespread along the northwest African slope (MAURIN, 1968). In the 'Discovery' surveys 430 H. mediterraneus were sampled from 11 stations on the upper slope (279-981 m) (Appendix I). Maximum densities (up to 47 fish/1000 m 2) were recorded from 279-522 m soundings (Fig. 10), which coincides approximately with the centre of abundance of 320--457 m for the species given by WOODS and SONODA (1973). Also from the northwest African slope (17°-33°N), GOLOVAN (1978) reports the depth range of this species as 350-950 m. The 'Discovery' samples contained mostly juvenile fish, which accounted for the two peaks in the length-frequency distribution (Fig. 23). No size relation with depth, however, was reflected in the results. Sex was
225
Ecology of deep-sea bottom-living fishes
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226
N.R. MERRETrand N.B. MARSHALL
determinable in specimens of >70 mm SL, but only 10 were found to be sexually mature of which 8 were recovering spent females. First maturity is probably attained, therefore, within the range 70-150 mm SL (Fig. 23). MARSHALL and MERRE'Iq" (1977) summarized the feeding habits of 23 specimens over the size range 51-242 mm SL. Analysis of a further 4 specimens have now been added (Table 4), leaving the conclusions unaltered that crustaceans are the primary prey of this species. Identifiable crustacean remains of natant decapods were present in 37% of fish examined. The occasional remains of echinoids (4%), polychaetes (4%) and fish (7%) indicated that the diet of H. mediterraneus is mixed.
SCORPAENIDAE
Helicolenus dactylopterus The only abundant scorpaenid in the catches, H. dactylopterus occurred in 8 samples with a total of 170 specimens (Appendix I). It occurred over the sounding range 279981 m, although it was more abundant from around 500 m to the top of the range, where the maximum density of 17 fish/1000 m 2 was recorded (Fig. 10). MAURIN (1968) reported this species to be widespread over the upper slope (220--642 m) in the northwest African area and GOLOVAN (1978) corroborates this with catches from the same region (21°-32°N) in soundings of 500-800 m. On the western side of the Atlantic, HAEDRICH,ROWE and POLLONI (1975) mention this species as a dominant organism in the depth zone 141285 m. The overall size range in the 'Discovery' collections was 29-345 mm SL, but the samples were dominated by the smaller, sexually immature specimens, indicated in the multi-peaked length-frequency distribution (Fig. 24). From those fish with distinguishable gonads, it was evident that ovarian maturity is initiated within the range 130-180 mm SL. No females were caught with ovaries in advance of the growth phase of maturation (Ill/V). The stomach contents of 7 specimens and the intestinal contents of 80 were examined and summarized by MARSHALL and MERRETT (1977, Table 1). The results indicate that H. dactylopterus is a highly selective benthic feeder. The ophiuroid, Ophiacantha abyssicola SARS, 1871, was present in 92% of specimens examined (Table 4). Minimal quantities of Crustacea, fish and Pyrosoma were also found. CYNOGLOSSIDAE
Symphurus nigricens This was the only flatfish caught in abundance and that is due to a single large catch of 165 individuals (45 fish/1000 m2). It was collected in only 3 other samples to give a total of 174 (Appendix I). The sounding range was 279--482 m and the abundant catch came from the shallowest sample (Fig. 10). This was at 20*N, which extends the range indicated by MAURIN (1968) by some 10-15 degrees to the south. The size range collected was 29-107 mm SL (Fig. 25). The length-frequency distribution has 3 peaks with evidence of a fourth at the lower size limit sampled. More detailed examination of this species was not undertaken.
227
Ecology of deep-sea bottom-living fishes
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228
N.R. MERRETFand N.B. MARSHALL
Resource partitioning among macrourids A salient feature of the overall collections is the relative dominance of the family Macrouridae in both numbers of species and their abundance. Macrourids comprised 18% of the species (26 spp.) and 48% of individuals (2240 specimens). The number of species is 3 short of the number given by GOLOVAN (1978) in his review of the northwest African slope fauna from the equator to 36°N. Only 21 species are common to both lists, however, indicating that a total of at least 34 macrourid species occurs in the area. While discussing the zoogeography of the macrourid fauna of the eastern Atlantic, IWAMOTO (1970) pointed out the greater diversity of the family to the north of the Gulf of Guinea. He reported only 16 species from the Gulf of Guinea. Ten species are common to both his collection and this one, which supports his view that the macrourid fauna of the Gulf of Guinea is somewhat different from its counterpart in the eastern North Atlantic. T h e depth ranges of the majority of macrourid species (18 out of 26) occurred in soundings shallower than 1600 m (see Appendix I). With such a rich diversity occupying moderately narrow depth limits, there is a high degree of co-occurrence. Indeed, no species was collected consistently in isolation from others, and it was far more usual for several species to be sampled together. The maintenance of such an association of closely related species prompts consideration of niche availability in the community. Evidently greater overlap occurs in the diets of macrourids than is found among shallow water demersal fish (PEARCY and AMBLER, 1974; MACPHERSON, 1979), which may be taken to support the contention of GRASSLE and SANDERS (1973) that in general a lower degree of competitive exclusion exists among deep-sea species. The relative success of representatives of three subfamilies of the Macrouridae in the area serves to reduce likely dietary overlap, with the widely divergent feeding patterns of trachyrhynchines and bathygadines on the one hand and macrourines on the other (MARSHALLand BOURNE, 1964; OKAMURA, 1970; GEISTDOERFER. 1975; MARSHALL and MERRETI', 1977: MCLELLAN. 1977). Confirmation of this is evident from Table 4, where the diets of the macrourids are compared with the other species investigated here. The emphasis on largely pelagic prey by B. melanobranchus contrasts with the feeding pattern of all but one macrourine, H. italicus. Yet the mean size of H. italicus is smaller and its food preferences are somewhat different. In this area at least, T. trachyrincus has a diet apparently intermediate between such pelagic feeders and the majority of macrourines examined, with their more evenly mixed diets of pelagic and benthic prey. (The latter, while largely composed of organisms of strictly unknown origin being representatives of groups with both pelagic and benthic forms, is substantiated here on the basis of the co-occurrence of sediment in the guts of the predators - - Table 4). Trachyrincus trachyrincus is relatively less dependent on benthic food and generally eats larger and more active pelagic prey. It also grows to a larger mean size than do the macrourines examined. The four sympatric species of Nezumia (N. aequalis, N. duodecim, N. micronychodon and N. sclerorhynchus) constituted the largest sample and provide an insight into ways in which competition may be lessened. Adult N. micronychodon, the largest of the local Nezumia and the species with the most gill rakers, processes more ooze for small organisms than do the other 3 species. Smaller specimens, up to about 30-40 mm HL, rely on a broad spectrum of epibenthic crustaceans (Table 4 and see p. 222). But larger specimens change their feeding to more benthic foraging for small tubicoious polychaetes not evidently preyed upon by other local Nezumia species. Despite the similarity in diet of the other
Ecologyof
deep-sea bottom-living
fishes
229
three species, the available data suggest that minor differences in centres of abundance (cf. Fig. 14 - N. aequalis c. 5OO-6CKlm, N. sclerorhynchus c. 700 m and N. duodecim c. 700900 m) may reduce competition. Even with this preliminary evidence, therefore, it is possible to observe indications of niche separation in the trophic relations of macrourids from the northwest African slope. SUMMARY General biological interest in the upwelling region off northwest Africa instigated an examination of the ecology of bottom-living fishes from the upper slope to abyssal depths. The investigation centred around a series of cruises during 1969-1977. Samples were collected from the area 08”-27”N and 14”-3o”W in soundings of 261-6059 m. A variety of gear was used. A total of 92 operations were carried out with an epibenthic sledge of 2.4 m2 mouth area (27), another of nearly 1.5 m2 mouth area (24), a semi-balloon otter trawl of 13.7 m headline length (13), a rectangular midwater trawl of 8 m* mouth area (3) baited pyramidal traps of 1.7 m base length (16) and a Xl-hook longline (9). The total collection comprised 4671 specimens representing at least 148 species from 42 families. The family Macrouridae dominated the catches, being represented by48% of the specimens and 18% of the species. Most species were not abundant. Only 25% were represented by more than 17 specimens. Evidently the towed gears sampled a different spectrum of species from the static baited gears. The catches of the towed gears alone were shown to have a high degree of similarity and so are considered compatible. Although the total catch from the traps and longlines constituted only about 2% of the overall collection, these gears attracted a disproportionately large number of elasmobranchs (77% trap and longline catch) relative to the sample taken by the nets (cl%), to account largely for the sampling dissimilarity. A total of 132 species were collected exclusively by towed gears and 8 species by baited gears alone. Only 8 species were common to the catches of both methods of sampling. The composition of the catches by towed gears was analysed by latitude. The results indicated homogeneity among the samples throughout the area surveyed, to enable comparison of all catches by sounding and by species. A generally close correlation was observed between haul composition of towed gears and sounding sampled. The composition of the catches altered steadily with sounding to depths of around 3000 m, with the lack of obvious fauna1 boundaries as the salient feature. In this respect, these results contrast with trenchant fauna1 bathymetric discontinuities found among slope surveys from both east and west coasts of North America. It is acknowledged that there are possible indications of discontinuities at around 1100 m and 2100 m, however, which do broadly coincide with the limits of the deep species assemblages (1270-1928 m) observed off southern New England by HAEDRICH, Row and POLLONI (1975). Nevertheless, marked zonation may be obscured by a reduced pressure for resource partitioning in the fish fauna off northwest Africa as a result of the high primary productivity, particularly offshore, in the area. Below 3000 m soundings the composition of the fauna was evidently more uniform. An examination of the interrelationships of species distinguished 2 main groups. The majority of species are slope-dwelling forms and constituted the first group. The second group have broader sounding ranges which, with one exception, extended beyond the slope-rise break.
230
N.R. MERRE1"rand N.B. MARSrlAUL
Comparison of this upwelling region with the non-upwelling habitat of the temperate western North Atlantic suggested that the species diversity off northwest Africa was about double that in the latter area. Furthermore, the mean size of the dominant species collected in medium-sized nets in soundings of less than 2000 m was smaller from the upwelling region. Species composition differed also, for the bathygadine macrourids, dominant in the upwelling area, were absent from the temperate North Atlantic. Deeper than 2000 m a marked difference was the apparent absence of a large, wide ranging macrourid or comparable fish in the upwelling zone, counterpart to C. ( N e m a t o n u r u s ) a r m a t u s in the non-upwelling area. This lack of evidence of the 'bigger-deeper' phenom e n o n among fishes is possibly explained by the situation of high productivity throughout the year favouring selection of species of small mean size with less need for nutrient storage. Estimation of the relative density of fishes provided a basis for comparing abundance from different bathymetric levels of the area surveyed. The catches on the upper slope were close to 100 fish/1000 m", but they declined exponentially with depth to about 2 orders of magnitude lower in soundings of around 2000 m. D e e p e r than 2000 m the decrease in relative density was tess marked and was maintained around 0.5/1000 m" at least to 4000 m soundings. Such a decrease in relative abundance is in general agreement with trawling results and submersible observations from the middle Atlantic coast of North America. Although not comparable with the results of the towed gear, catch per unit effort was calculated for the longline operations on the basis of catch per hook hour. Over the 9 operations the mean catch was 0.04 fish per hook hour weighing 0.15 kg per hook hour. It was noted that the estimate of density of fish from off northwest Africa was approximately equal to that calculated from a photographic series taken from a submersible in the temperate western North Atlantic. Estimates from such a series have been shown to be about two to six times greater than those generated by catches of nets roughly similar in size to those used in the present survey. While accepting the tacit danger of comparing estimates of absolute abundance from one area to another when collected by different gear, the present evidence indicated a greater abundance of slope fishes off northwest Africa, probably sustained by greater productivity induced by upweUing. A total of 14 species, represented by 60 or more individuals, were examined in detail. O n e species each of the families Synaphobranchidae, Halosauridae, Trachichthyidae, Scorpaenidae and Cynoglossidae, together with 9 species of the family Macrouridae were considered. All but one of these are slope dwellers and the majority were most abundant in soundings of less than 1000 m. The evidence provided information in varying detail on vertical distribution, population structure, breeding biology and feeding. The relative dominance of the family Macrouridae, both in species richness and diversity, prompted discussion of niche availability in the community and comments on resource partitioning among these co-occurring species.
Acknowledgements - - Many people have helped us, either directly or indirectly,during the preparation of this
paper. We thank them all and apoiogiseto any that we may have inadvertentlyomitted from this acknowledgement. In the course of identifying the samples the following have kindly provided specialist identificationsof particular species: M.E. ANDERSON(Virginia Institute of Marine Science)and A.P. ANDRIYASHEV(Zoological Institute, Leningrad) - - Zoarcidae; J. BLACHE(Musrum National d'Histoire Naturelle, Paris) -- Synapho-
Ecology of deep-sea bottom-living fishes
231
branchidae; L.J.V. CAMPAGNO(Tiburon Center for Environmental Studies) - - Scyliorhinidae and Squalidae, D.M. COHEN (National Marine Hsheries Service, Systematics Laboratory, Washington ) - - Macrouridae; A,W. EBELING (University of California) --Stephanoberycidae; the late C.L. Hunns (Scripps Institution of Oceanography) and B. FERNHOLM(Roskilde Universitetscenter) - - Myxinidae; T. IWAMOTO(California Academy of Sciences) - - Macrouridae; G. K~EF~ (Institut fiir Seefischerei, Hamburg) - - Squalidae; D.F. MARKLE (Huntsman Marine Laboratory, Canada) - - Alepocephalidae; J.G. NIELSEN (Universitets Zoologisk Museum, Copenhagen) - - Ophidiidae and Aphyonidae; M. STEHMANN(Institut for Scefischerei, Hamburg)-Rajidae. We are indebted to J.P. BRIDGER (Ministry of Agriculture, Fisheries and Food, Directorate of Fisheries Research, Lowestoft), S.J. MARINOVICH,(Marinovich Trawl Company Inc.), K.J. SULAK(Virginia Institute of Marine Science) and F. WA'n~NE (National Marine Fisheries Service, Northwest Fisheries Center, Seattle) for contributing valuable information on the behaviour under tow of trawls in general and the OTSB 14 in particular. M.J.R. FASHAM (Institute of Oceanographic Sciences) generously provided considerable help with the statistical treatment of the data and also carded out the computations. A.C. WHEELEa (British Museum (Natural History)) faciliated the X-radiography of squaloid sharks for identification purposes. D. CHAIN (9, North View, London SW19) and Mrs R.A. RUSSELL(IOS) kindly assisted in the preliminary analysis of intestinal contents, while A.L. RICE, H.S.J. ROE and M.H. THURSTON(IOS) afforded specialist identifications of dietry crustaceans. We are grateful to Mrs R.A. RUSSELLfor preparing the illustrations and general assistance, as well as to other colleagues at IOS, together with the Captain and crew of RRS 'Discovery', for their help in the collection of samples. J.R. BADCOCKand P.M. DAVID (IOS) kindly read the manuscript and offered much helpful advice during the course of the study. REFERENCES ALDRED, R.G., M.H. THURSTON,A.L. RICEand D.R. MORLEY(1976) An acoustically monitored opening and closing epibenthic sledge. Deep-Sea Research, 23, 167-174. BAKKEN,E., J. LAHN-JOHANNESSENand J. GJOSAETER(1975) Demersal fish on the continental slope offNorway. Saetrykk av Fiskets Gang, (34), 557-565. BLACHE, J., J. CADENATand A. STAUCH (1970) CI6s de d6termination des poissons de mer signal6s dans I'Atlantique Orientale (entre le 20e parall~le N.et le 15e parall~le S.). Faune Tropicale, 18, 1--479. BRIDGER, J.P. (1978) New deep-water trawling grounds to the west of Britain. Laboratory Leaflets, MAFF Directorate of Fisheries Research, Lowestofi, (41), 40pp. BULHS, H.R., JR. and R. CUMMINS,JR. (1963) Another look at the royal shrimp resource. Proceedings of the Gulf and Caribbean Fisheries Institute, 15th annual session, pp. 9-12. CLARKE, M.R. and N.R. ME~tRETT(1972) The significance of squid, whale and other remains from the stomachs of bottom-living deep-sea fish. Journal of the Marine Biological Association of the United Kingdom, 52, 599-603. COHEN, D.M. and D.L. PAWSON(1977) Observations from the DSRV Alvin on populations of benthic fishes and selected larger invertebrates in and near DWD-106. Baseline Report of Environmental Conditions in Deepwater Dumpsite 106. U.S. Department of Commerce, NOAA, Dumpsite Evaluation Report 77-1, 2, Biological Characteristics. DAY, D.S. and W.G. PEARC¥ (1968) Species associations of benthic fishes on the continental shelf and slope off Oregon. Journal of the Fisheries Research Board, Canada, 25, 2665--2675. Du BUIT, M-H. (1978) Alimentation de quelques poissons t616ost6ens de profondeur dans la zone du seuil de Wyville Thomson. Oceanologica Acta, I, 129-134. FASHAM, M.J.R. (1977) A comparison of nonmetric multidimensional scaling, principal components and reciprocal averaging for the ordination of simulated coenoclines, and coenoplanes. Ecology, 58, 551-561. FERNHOLM, B. (In press) A new species of hagfish of the genus Myxine, with notes on other eastern Atlantic myxinids. Journal ofFish Biology. FORSTER, G.R. (1964) Line-fishing on the continental slope. Journal of the Marine BioiogicalAssociation of the United Kingdom, 44, 277-284. FORSTER, G.R. (1968) Line-fishing on the continental slope: II. Journal of the Marine Biological Association of
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Aden, with observations on their population density, diversity and habits. Bulletin of the Museum of Comparative Zoology, Harvard, 132, (2), 22.5-244. MARSHALL, N.B. (1973) Family Macrouridae. In: Fishes of the western North Atlantic, D.M. COHEN, editor-inchief. Memoir, Sears Foundationfor Marine Research, (1), part 6, 496--665. MARSHALL,N.B. and T. IWAMOTO(1973a) Genus Coryphaenoides Gunnerus 1765. In: N.B. MARSHALL,Family Macrouridae. In: Fishes of the western North Atlantic, D.M. COHEN, editor-in-chief. Memoir, Sears Foundation for Marine Research, (1), part 6, 565-580. MARSHALL, N.B. and T. IWAMOTO(1973b) Genus Nezumia Jordan 1904. In: N.B. MARSHALL,Family Macrouridae. In: Fishes of the Western North Atlantic, D.M. COHEN, editor-in-chief. Memoir, Sears Foundationfor Marine Research, (1), part 6, 624--649. MARSHALL, N.B. and N.R. MERRETr (1977) The existence of a benthopelagic fauna in the deep-sea. In: A Voyage of Discovery. George Deacon 70th Anniversary Volume, M.V. ANGEL, editor, pp. 483-497, Supplement to Deep-Sea Research, 24. MAUL, G.E. (1976) The fishes taken in bottom trawls by R.V. "Meteor" during the 1967 Seamounts Cruises in the Northeast Atlantic. "Meteor" Forschungs-Ergebnisse, Reihe D, (22), 1-69. MAURIN, C. (1968) I~.cologie ichthyologique des fonds chalutables Atlantiques (de la Baie Ib~ro-Marocaine a la Mauritanie) et de la M6diterran~e occidentale. Revue des Travaux de rlnstitut des Pdches Maritimes, 32 (1), 5-147. MCLELLAN, T. (1977) feeding strategies of the macrourids. Deep-Sea Research, 24, 1019-1036. MERRETT, N.R. (1971) Aspects of the biology of billfish (Istiophoridae) from the equatorial western Indian Ocean. Journal of Zoology, London, 163,351-395. MERRETT, N.R. (1978) On the identity and pelagic occurrence of larval and juvenile stages of rattail fishes (Family Macrouridae) from 6(Y'N, 20°W and 53°N, 2ff'W. Deep-Sea Research, 25, 147-160. MERRE'rr, N.R. (1980) Bathytyphlops sewelli (Pisces, Chlorophthalmidae) a senior synonym of B. azorensis, from the eastern North Atlantic with notes on its biology. Zoological Journal of the Linnean Society, 68, 99-109. MOORE, H.B. (1972) Aspects of stress in the tropical marine environment. Advances in Marine Biology, 10, 217-269. MUSICK, J.A., C.A. WENNERand G.R. SEDBERRV(1975) Archibenthic and abyssobenthic fishes of deep water dumpsite 106 and the adjacent area. U.S. Department of Commerce, NOAA Dumpsite Evaluation Report, 75-1,229-269. MUS1CK, J.A. (1976) Patterns in the community structure of demersal fishes on the continental slope and rise of the western North Atlantic. In: Book of Abstracts of papers presented at Joint Oceanographic Assembly, Edinburgh, U.K. 13-14 September 1976. FAO: Rome, 1976. NICHOLS, J. and G.T. ROWE (1977) Infaunal macrobenthos off Cap Blanc, Spanish Sahara. Journal of Marine Research, 35, (3), 525-536. NYBELIN, O. (1957) Deep-sea bottom-fishes. Report of the Swedish Deep Sea Expedition, 2, Zoology (20), 247-345. OKAMURA,O. (1970) Studies on the macrouroid fishes of Japan. Morphology, ecology and phylogeny. Report of the Usa Marine Biological Station, Kochi University, 17, 1-179. PARSONS, L.S. (1976) Distribution and relative abundance of roundnose, roughhead and common grenadiers in the northwest Atlantic. International Commission for the Northwest Atlantic Fisheries, Selected Papers, (1), 73-88. PEARCY, W.G. and J.W. AMBLER (1974) Food habits of deep-sea macrourid fishes of the Oregon (2oast. Deep-Sea Research, 21,745-759. PECHENIK, L.N. and F.M. TROYANOVSKI1(1970) Syv' eraya baza tralovogo rybolovstva na materikovom sklone Severhoi Atlantiki. Murmansk: Murmanskoe Knizhuse Izdatel'stvo. (English translation: Trawling resources on the North Atlantic continental slope. Jerusalem: Israel Program for Scientific Translations, 1971, 71 pp). PODRAZHANSKAYA,S.G. (1971) Feeding and migrations of the roundnose grenadier, Macrourus rupestris, in the northwest Atlantic and Iceland waters. International Commission for the Northwest Atlantic Fisheries, Redbook, Part 3, 1971, 115-123. RANNOU, M. (1973) l~tude de la croissance de Coelorhynchus coelorhynchus (T616ost6ens, Gadiformes). Bulletin du Musdum National d'Histoire Naturelle, Paris, 3e s~rie, (160) l~cologie g6n6rale 16, 273-281. RANNOU, M. (1975) Donn~es nouvelles sur l'activit6 reproductrice cycliques des poissons benthique bathyaux et abyssaux. Compte rendu hebdomadaire des seances de l'Academie des Sciences, Paris, 281, S6rie D, 10231025. JPO
9:4
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APPENDIX I
Species list and capture stations, including observed size and sounding ranges. MYXINIDAE: 1. Myxine sp. nov. FERNHOLM, in press. 7841#3 (1), 7843#1 (1), 7843#2 (13), 7848#1 (1), 7848# 2 (1). Total: 17 SL range: 260-522 mm. Sounding range: 614-976 m. SCYLIORHINIDAE: 2. Galeuspolli CADENAT, 1959.7816#5 (1), 8930#1 (22), 8931#1 (1). Total: 24 TL range: 248-470 mm. Sounding range: 296-981 m. 3. Apristurusprofundorum (GOODE and BEAN, 1896). 7852#1 (1). Total: 1 TL: 148 mm. Sounding: 989 m. SQUALIDAE: 4. Etmopterus princeps COLLE'Iq', 1904. 7822# 1 (4), 7822#6 (1). Total: 5 TL range: 550--655 mm. Sounding range: 1153-1164 m. 5. Centrophorus granulosus BLOCH and SCHNEIDER, 1801. 7813#1 (2), 7811#1 (1), 7817#1 (3), 7841#4 (1), 7848#3 (1), 7849#1 (6). Total: 14 TL range: 840-1240 mm. Sounding range: 578-985 m. 6. C. squamosus (BONNATERRE, 1788). 7813#1 (6), 7814#1 (16), 7843#3 (1), 7849#1 (1). Total: 24 TL range: 390-1205 mm. Sounding range: 578-798 m. 7. Centroscymnus coelolepis (BOCAGE and CAPELLO, 1864). 7822#2 (1), 7822#5 (1), 7822#6 (1), 8932#2 (1). Total: 4 TL range: 680-850 mm. Sounding range: 1151-2375 m. 8. C. cryptacanthus REGAN, 1906.7813#1 (1), 7822#6 (2), 7848#3 (2). Total: 5 TL range: 660-1035 ram. Sounding range: 601-1164 m. 9. Scymnodon ringens BOCAGE and CAPELLO, 1864. 7843#3 (1). Total: 1 TL: 660 mm. Sounding: 632 m. 10. Deania calcea (LOWE, 1839). 7814#1 (1), 7841#2 (3), 7841#4 (12), 7848#3 (1), 8931#1 (1). Total: 18 TL range: 640-935 mm. Sounding range: 578-985 m. 11. D. profundorum (SMITH and RADCLIFFE, 1912). 7813#1 (1). Total: 1 TL: 750 mm. Sounding: 601 m. RAJIDAE: 12. Raja straeleni POLL, 1951. 7810#1 (3), 7811#1 (1). Total: 4 TL range: 155-290 mm. Sounding range: 307-690 m. 13. R. nidarosiensis STORM, 1881. 7841#2 (1), 8931#1 (1). Total: 2 TL range: 14t30-1820 mm. Sounding range: 918-981 m. 14. Raja sp. 9133#7 (1). Total: 1 TL: 583 mm. Sounding: 2160 m. HYDROLAGIDAE: 15. Hydrolagusmirabilis (COLLETI', 1904). 7839#1 (2), 7845#1 (1), 8003 (1), 8931#1 (2). Total: 6 L t range: 68-360 ram. Sounding range: 734-981 m. 16. H. alberti BIGELOW and SCHROEDER, 1951. 7839#1 (1). 235
236
N.R, MERREVrandN.B. MARSHAIJ
Total: 1 Lt: 540 mm. Sounding: 933 m. RHINOCHIMAERIDAE: 17. Harriotta raleighana GOODE and BEAN, 1895. 7853#1 (1), 9132#5 (1). Total: 2 L ~range: 375-534 mm, Sounding range: 1510-3149 m. XENOCONGRIDAE: 18. Echelus pachyrhynchus (VAILLANT, 18881. 7810# 1 (2), 7816#5 (1), 8020 (34). Total: 37 SL range: 92-515 mm. Sounding range: 279-307 m. 19. Myrophis plumbeus (COPE, 1871). 8020 (1). Total: 1 SL: 221mm. Sounding: 279 m. NETTASTOMATIDAE: 20. Nettastoma melanurum RAFINESQUE, 1810. 7851# 1 ( 1), 8930# 1 (1). Total: 2 SL range: 375 a.40 mm. Sounding range: 510-522 m. 21. Veneficaproboscidea (VAILLANT, 1888). 9132#5 (I). Total: 1 SL: c. 900 mm. Sounding: 3149 m. CONGRIDAE: 22. Coloconger cadenati KANAZAWA, 1961. 7815#2 (2), 7817# 1 (2). Total: 4 SL range: 397-515 mm. Sounding range: 612--649 m. 23. Uroconger vicinus VAILLANT, 1888. 7810#1 (5), 7816#5 (5), 7975 (2), 8014 (l), 8020 (1). Total: 14 SL range: 130-305 mm. Sounding range: 279-814 m 24. Bathycongrus africanus (POLL, 1953). 7845 # 1 (1), 7852 # 1 ( 1). Total: 2 SL range: 190-197 mm. Sounding range: 952-989 m. 25. Ariosoma balearicum (DELAROCHE, 18091. 7811#1 (2). Total: 2 SL range: 329-340 mm. Sounding: 690 m. 26. Bathyuroconger vicinus (VAILLANT, 1888). 8931 # 1 ( 1 ). Total: 1 S L : 2 6 8 m m . Sounding: 981m. 27. Pseudophichthyssplendens (LEA, 1913). 8931 # 1 (3). Total: 3 SL range: 278-345 mm. Sounding: 981 m. SYNAPHOBRANCHIDAE: 28. Synaphobranchus kaupi JOHNSON, 1862. 7822#7 (4), 7838#1 (1), 7839#1 (2), 7840# 1 (20), 7841#3 (2), 7844# I (2), 7845# 1 (10), 7846#1 (2), 7851#1 (8), 7852#1 (8), 7975 (11), 7984 (5), 7991 (3), 7993 (1), 8001 (12), 8003 (3), 8014 (1), 8519#7 (141, 8694#4 (3), 8931#1 (55), 9133#7 (2). Total: 169 SL range: 91--605 mm. Sounding range: 482-2160 m. 29. S. (Histiobranchus) bathybius (GUNTHER, 1877). 9131#1T' (1), 9541# 18~ (1). Total: 2 SL range: 476-1280mm. Depth range~: 3974-4036 m. 30. Haptenchelys texis ROBINS and MARTIN, 1976. 8528# 1 (2), 8682#5 (21, 8933#3 (1), 9133#7 (1). Total: 6 SL range: 183-455 mm. Sounding range: 2160-3153 m. 3 I. llyophis brunneus GILBERT, 1892. 8001 (1), 8519#7 (1). Total: 2 SL range: 432--482 mm. Sounding range: 1017-1458 m. 32. Nettodarus sp. (sensu BLACHE, MAUL and SALDANHA, 1970). 7816#2 (1), 7816#5 (2). Total: 3 SL range: 83-100 mm. Sounding range: 291-296 m. 33. Simenchelysparasitica GOODE and BEAN, 1879.7848#2 (3), 7854#2 (3), 8001 (11 ). Total: 17 SL range: 218-351mm. Sounding range: 976-1458 m. HALOSAURIDAE: 34. Halosaurus (Halosaurus) ovenii JOHNSON, 1863. 7851#1 (11, 7993 (1), 8014 (1), 8931#1 (5).
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Total: 8 Gn. L range: 94--254 mm. Sounding ranga: 522-981 m. 35. H (Halosaurichthys) johnsonianus VAILLANT, 1888. 7811#1 (3), 7839#1 (332), 7840#1 (2), 7845#1 (25), 7984 (11), 8012 (11), 8519#7 (136), 8931#1 (3). Total: 523 Gn. L range: 67-174 mm. Sounding range: 690--1524 m. 36. H. (Halosaurichthys) guentheri GOODE and BEAN, 1896. 7811#1 (1), 7839#1 (49), 7845#1 (4), 8519#7 (4). Total: 58 Gn. L range: 68-165 mm. Sounding range: 690-1017m. 37. Halosauropsis macrochir (GONTHER, 1878). 7090 (2), 7091 (1), 7092 (2), 8682#5 (1), 8932#2 (2), 8933#3 (2), 8933#4 (1), 9132#5 (5), 9133#7 (1). Total: 17 Gn. L range: 114-280 mm. Sounding range: 2160-3311 m. 38. Aldrovandia affinis (GONTHER, 1877). 7846# 1 (3), 7853# 1 (4), 7991 (1). Total: 8 Gn. L range: 62-147 mm. Sounding range: 1502-1510 m. 39. A. phalacra (VAILLANT, 1888). 7853#1 (9), 8694#4 (1). Total. 10 Gn. L range: 78-121mm. Sounding range: 1510-1806 m. 40. A. gracilis GOODE and BEAN, 1896.7822#7 (3), 7853#1 (1). Total: 4 Gn. L range: 60-82 mm. Sounding range: 1203-1510 m. 41. A. rostrata (GUNTHER, 1878). 7112 (1). Total: 1 Gn. L: 96mm. Sounding: 2956 m. LIPOGENYIDAE: 42. Lipogenys gillii GOODE and BEAN, 1895. 7984 (1). Total: 1 Gn. L:38 mm. Sounding: 850 m. NOTACANTHIDAE: 43. Notacanthus bonapartei RlSSO, 1840. 7840#1 (2), 7845#1 (1), 7984 (1), 8519#7 (2), 8931#1 (8), 9134#0 (1). Total: 15 Gn. L range: 36-160 mm. Sounding range: 850-1945 m. 44. N. chemnitzi BLOCH, 1788. 8931#1 (3). Total: 3 Gn L range: 94-117 mm. Sounding: 981 m. 45. Polyacanthonotus (Gnathonotacanthus) africanus (GILCHRIST and VON BONDE, 1924). 7853#1 (5), 8519#7 (1). Total: 6 Gn. L range: 35-71 mm. Sounding range: 1017-1510 m. GONOSTOMATIDAE: 46. Yarella blackfordi GOODE and BEAN, 1896.7811#1 (6). Total: 6 SL range: 109-178 mm. Sounding: 690 m. ALEPOCEPHALIDAE: 47. Alepocephalus agassizii GOODE and BEAN, 1883. 7840# 1 (3). Total: 3 SL range: 225-380 mm. Sounding: 1524 m. 48. A. bairdii GOODE and BEAN, 1879.8931#1 (2). Total: 2 SL range: 299-362 mm. Sounding: 981 m. 49. A. rostratus RlSSO, 1820. 7811#1 (8), 7839#1 (6), 8519#7(2), 8931#1 (18). Total: 34 SL range: 111-420 mm. Sounding range: 690-1017 m. 50. Bellocia koefoedi (PARR, 1951). 8528#1 (2), 8682#5 (1), 8933#4 (1), 9132#5 (3), 9133#7 (1). Total: 8 SL range: 88-395 mm. Sounding range: 2160-3153 m. 51. Conocara salmonea (GILL and TOWNSEND, 1897). 9131#2 (2), 9131#172 (3), 9541#5 (2), 9541#192 (1). Total: 8 SL range: 110--473 mm. Depth/sounding2 range: 3910--4040 m. 52. C. murrayi (KOEFOED, 1927). 8932#2 (1). Total: 1 SL: 107 mm. Sounding: 2375 m.
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N.R. IVIERRETI"and N.B. MARSHALL
53. Rinoctes nasutus KOEFOED, 1927.9131#3 (2), 9131#4 (1), 9131#17' (3), 9541#5 (3). Total: 9 SL range: 121-181 mm. Sounding range: 3875-3995 m. 54. Bathytroctes microlepis GCINTHER, 1878.9133#7 (1). Total: 1 SL: 275 mm. Sounding: 2160 m. 55. Talismania mekistonema SULAK, 1975. 7853# 1 (1). Total: 1 SL: 182 mm. Sounding: 1510 m. 56. T. antillarum GOODE and BEAN, 1895. 7845#1 (4). Total: 4 SL range: 32-42 mm. Sounding: 952 m. 57. Leptoderma macrops VAILLANT, 1886. 7839#1 (6), 7840#1 (1), 7845#1 (5), 7846#1 (1), 8519#7 (6). Total: 19 SL range: 61-113 mm. Sounding range: 933-1524 m. 58. Xenodermichthys copie GILL, 1884. 7811#1 (4), 7838#1 (1), 7839#1 (1), 7844#1 (2), 7845#1 (1), 8003 (1), 8931#1 (6). Total: 16 SL range: 51-165 mm. Sounding range: 482-981 m. Unidentified alepocephalids. 7840#1 (1), 7993 (1). Total: 2 SL range: 23-24 mm. Sounding range: 690-1524 m. CHLOROPHTHALMIDAE: 59. Chlorophthalmus agassizi BONAPARTE, 1840.7810#1 (1), 7816#5 (1), 8020 (3). Total: 5 SL range: 52-162 mm. Sounding range: 279-307 m. 60. Parasudisfraser-brunneri (POLL, 1953). 7816#2 (2), 7816#5 (3). Total: 5 SL range: 141-185 mm. Sounding range: 291-296 m. 61. Bathypterois (Bathypterois) dubius VAILLANT, 1888. 7846#1 (1), 7853# 1 (l), 7991 (3), 8001 (2), 8012 (11), 8519#7 (3), 8931#1 (7). Total: 28 SL range: 69-193 mm. Sounding range: 981-1510 m. 62. B. (Bathycygnus) longipes GUNTHER, 1878. 7092 (1), 8682#5 (1), 8933#4 (1), 9131#1 (1), 9541#5 (1), 9541#6 (1). Total: 6 SL range: 134-166 mm. Sounding range: 2984-4004 m. 63. B. (Benthosaurus) grallator (GOODE and BEAN, 1886). 8932#2 (1). Total: 1 SL: 368mm. Sounding: 2375 m. 64. Ipnops murrayi GI3NTHER, 1878. 9131 # 10 (1). Total: 1 SL: 115 mm. Sounding: 3951m. 65. Bathymicrops regis HJORT and KOEFOED, 1912.8524#6 (2), 9128#/6 (1). Total: 3 SL range: 82-105 mm, Sounding range: 4415-5726 m. 66. Bathytyphlopssewelli (NORMAN, 1939). 7092 (1), 8933#3 (2), 9131#10 (1), 9541#6 (2). Total: 6 SL range: 146--282 mm. Sounding range: 2985-3951 m. SYNODONTIDAE: 67. Bathysaurus ferox GCINTHER, 1878.8932#2 (1), 9133#7 (6). Total: 7 SL range: 450-505 mm. Sounding range: 2160-2375 m. 68. B. mollis GCINTHER, 1878.9131#2 (1). Total: 1 S1:435 mm. Sounding:3926 m. ATELEOPODIDAE: 69. Guentherus altivelis OSORIO, 1917. 7810# 1 (1). Total: 1 SL: 144 mm. Sounding:307 m. LOPHIIDAE: 70. Lophius piscatorius LINNAEUS, 1758.7810# 1 (1). Total: 1 SL: 188 mm. Sounding:307 m.
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CHAUNACIDAE: 71. Chaunaxpictus LOWE, 1846. 7810#1 (1), 7811#1 (1), 7816#5 (5), 8014 (2), 8930#1 (2), 8931#1 (1). Total: 12 SL range: 38-206 mm. Sounding range: 296-981 m. OGCOCEPHALIDAE: 72. Dibranchus atlanticus PETERS, 1875. 7816#5 (14), 7822//7 (3), 7838//1 (2). Total: 19 SL range: 39-103 mm. Sounding range: 296-1203 m. MORIDAE: 73. Mora moro (RlSSO, 1810). 7848//3 (2), 7849#1 (5), 7852//1 (1). Total: 8 SL range: 435--640 mm. Sounding range: 798-989 m. 74. Laemonema laureysi POLL, 1953. 7810//1 (33), 7811//1 (1), 7844//1 (1), 8014 (1), 8930//1 (1). Total: 37 SL range: 78-235 mm. Sounding range: 307--690 m. 75. Brosmiculus imberbis VAILLANT, 1888. 7811//1 (1), 8020 (1). Total: 2 SL range: 72-109 ram. Sounding range: 279--690 m. 76. Physiculus huloti POLL, 1953. 7810//1 (1), 7816//2 (1), 7816//5 (1). Total: 3 SL: 51 mm. Sounding range: 291-307 m. 77. P. dalwigki KAUP, 1858. 8020 (6). Total: 6 SL range: 55-114 mm. Sounding: 279 m. MERLUCCIIDAE: 78. Merluccius atlanticus (LINNAEUS, 1758). 8930# 1 (1). Total: 1 SL: 350mm. Sounding: 510 m. OPHIDIIDAE: 79. Bathyonus sp. 7090 (1), 7811//1 (3), 8933//3 (2), 9131//1 (5), 9131#2 (4), 9131//3 (1), 9131//9 (2), 9131//172 (7), 9541//5 (15), 9541//6 (1), 9541//192 (1). Total: 42 SL range: 40-226 ram. Depth/Sounding 2 range: 690-4040 m. 80. Dicrolene intronigra GOODE and BEAN, 1882. 7811//1 (2), 7822//7 (1), 7839//1 (8), 7840//1 (4), 8001 (2), 8012 (4), 8519//7 (2), 8694//4 (1). Total: 24 SL range: 46-285 mm. Sounding range: 690-1806 m. 81. Monomitopus metriostoma (VAILLANT, 1888). 7811//1 (7), 7839//1 (21), 8012 (1). Total: 29 SL range: 75-140 mm. Sounding range: 690-1261 m. 82. Ophidion rochei MOLLER, 1845. 8020 (2). Total: 2 SL range: 110-150 mm. Sounding: 279 m. 83. Penopus microphthalmus (VAILLANT, 1888). 9132//5 (1). Total: 1 SL: 155 mm. Sounding: 3149 m. 84. Bassozetus sp. 9132//5 (2), 9133//7 (1). Total: 3 SL range: 155-250 ram. Sounding range: 2160-3149 m. 85. Holomycteronus sp. 9132//5 (1). Total: 1 SL: > 275 ram. Sounding: 3149 m. 86. Porogadus sp. 7090 (1), 8528//1 (1), 9132//5 (1), 9133#5 (2), 9540//1 (1). Total: 6 SL range: 72-156 ram. Sounding range: 2007-3153 m. 87. Acanthonus armatus GONTHER, 1878.9133//7 (1). Total: 1 SL: 395 mm. Sounding: 2160 m. APHYONIDAE: 88. Aphyonus gelatinosus GONTHER, 1878.7991 (1). Total: 1 SL: 109 mm. Sounding: 1510m. 89. A. rassi NIELSEN, 1975. 8524#1 (2). Total: 2 SL range: 24--60 mm. Sounding: 4412 m.
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90. Barathronus parfaiti (VAILLANT, 1888). 9131 # 172 (1). Total: 1 SL: 72 mm. Depth 2 range: 3910-3995 m. 91. Nybelinia eriksoni (NYBELIN, 1957). 8682#5 (1). Total: 1 SL: 55 ram. Sounding: 3000 m. ZOARCIDAE: 92. Lycenchelys crassiceps ROULE, 1919.9133#7 (2). Total: 2 SL range: 435-515 mm. Sounding: 2160 m. 93. Melanostigma atlanticum KOEFOED, 1952. 7838#l (6), 7844#1 (1), 7853#1 (1), 8003 (3). Total: 11 SL range: 58-94 mm. Sounding range: 482-1510 m. 94. Pachycaraobesa ZUGMAYER,1911. 9131#1 (1). Total: 1 SL:345 mm. Sounding: 4004 m. MACROURIDAE: 95. Trachyrincus trachyrincus (RISSO, 1810). 7811#1 (11), 7838#1 (23), 7839#1 (10), 7841#2 (1), 7844#1 (1), 7845#1 (5), 7993 (1), 8003 (13), 8014 (7), 8519#7 (3), 8930#1 (8), 8931#1 (15). Total: 98 H L range: 7-155 mm. Sounding range: 482-1017 m. 96. Gadomus arcuatus (GOODE and BEAN, 1886). 7852#1 (1). Total: 1 H L : 4 6 m m . Sounding: 989 m. 97. G. longifilis (GOODE and BEAN, 1886). 7853# 1 (53), 7991 (2). Total: 55 H L range: 2 A, 43 mm. Sounding: 1510 m. 98. Bathygadusfavosus GOODE and BEAN, 1886. 7853#1 (3), 7991 (l). Total: 4 H L range: 29-87 mm. Sounding range: 1510-1512 m. 99. B. melanobranchus VAILLANT, 1888. 7839#1 (40), 7845#1 (76), 7852#1 (4), 7984 (4), 8003 (5), 8519#7 (90), 8931#1 (188). Total: 407 H L range: 7--84 mm. Sounding range: 734-1017 m. 100. Coelorinchus coelorinchus coelorinchus (Rlsso, 1810). 7810#1 (28), 7816#5 (2), 7844#1 (1), 8014 (2), 8020 (31), 8930#1 (2). Total: 66 HL range: 13--69 mm. Sounding range: 279-572 m. 101. C. occa (GOODE and BEAN, 1885). 7822#7 (1), 7840#1 (1), 7853#1 (1), 7991 (1). Total: 4 H L range: 31-112 mm. Sounding range: 1203-1524 m. 102. Coryphaenoides (Coryphaenoides) giintheri (VAILLANT, 1888), 7840#1 (8), 8694#4 (3), 9133#5 (2), 9133#7 (16), 9134#0 (1). Total: 30 HL range: 19-59 mm. Sounding range: 1524-2160 m. 103. C. (C.) zaniophorus (VAILLANT, 1888). 7845-#1 (4), 8003 (2), 8519#7 (1), 8931#1 (13), 8932#2 (1). Total: 21 H L range: 42--88 mm. Sounding range: 734-2375 m. (The 13 specimens of Coryphaenoides from Stn. 8931#1 call into question the validity of C. colon MARSHALL and IWAMOTO (1973a). All bear the characters of a fully scaled snout, an interorbital width <20% HL (15.2-20.7% HL) and a thick and fleshy barbel, which identify them as colon or zaniophorus from the key given by MARSHALL and IWAMOTO (1973a). Beyond that, the two species are distinguished by the length of the snout and horizonal diameter of the orbit relative to the head length. In colon the snout length is approximately equal to the orbit diameter both of which are 26-33% HL. In zaniophorus, on the other hand, the snout length (25% HL in type specimen) is conspicuously less than the horizontal diameter of the orbit (35%). Based on these characters, 8 specimens (60.2-87.6 mm HL) conform to the
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measurements given for colon (snout length 26.2-29.4% HL, orbit diam. 29.133.7% HL). The remaining 5 specimens (41.6-63.4 mm HL), however, agree more closely with the proportions given for zaniophorus (snout length 27.5-30.2% HL, orbit diam. 34.4-36.4% HL). A plot of these values gives a general indication that smaller specimens have the proportions of zaniophorus and the larger ones of colon. Allometric variation within a single species is a more tenable explanation of this situation than the co-occurrence of 2 such closely related species in the same sample, which in addition would be the first record of C. colon in the eastern North Atlantic. We therefore conclude that the likelihood is that C. colon will be found to be conspecific with C. zaniophorus. ) 104. C. (C.) macrocephalus MAUL, 1951. 8932#2 (1). Total: 1 HL: 215 mm. Sounding: 2375 m. 105. C. (Coryphaenoides) sp. A. 7840#1 (2), 9133#5 (2), 9134#0 (1). Total: 5 H L range: 35-106 mm. Sounding range: 1524-2136 m. 106. C. (Nematonurus) armatus (HECTOR, 1875). 8682#5 (1), 8933#3 (1), 9131#4 (1), 9132#5 (1). Total: 4 HL range: 85-137 mm. Sounding range: 2985-3875 m. 107. C. (Chalinura) leptolepis GONTHER, 1877. 8521#1 (1), 9131#17" (1), 9132#5 (1). Total: 3 HL range: 65-124 mm. Depth/Sounding ~ range: 3055-3995 m. 108. C. (C.)profundicola (NYBELIN, 1957). 9131#1 (1), 9131#2 (2), 9541#5 (3), 9541#6 (1). Total: 7 HL range: 66-111 mm. Sounding range: 3926-4004 m. 109. C. (C.) mediterranea (GIGLIOLI, 1893). 7853#1 (1). Total: 1 HL: 76 mm. Sounding: 1510 m. 110. C. (Lionurus) carapinus GOODE and BEAN, 1883. 7090 (2), 7091 (1), 8528#1 (1), 8540#1 (1), 8682#5 (2), 9131#1 (11), 9131#2 (3), 9131#3 (4), 9131#12 (1), 9131#17 z (2), 9132#5 (7), 9133#5 (3), 9541#1 (1), 9541#3 (1), 9541#5 (21), 9541#6 (1). Total: 62 HL range: 12-54 mm. Depth/Sounding ~ range: 1524--4004 m. Unid.Coryphaenoides sp. 9540# 1 (1). Total: 1 HL: 21 mm. Sounding: 2007 m. 111. Hymenocephalus italicus GIGIOLI, 1884. 7816#2 (14), 7816#5 (136), 7844#1 (80), 7851#1 (31), 7993 (13), 8930#1 (19). Total: 293 HL range: 8-36 mm. Sounding range: 291--690 m. 112. Cetonurusglobiceps (VAILLANT, 1888). 7822#7 (1), 7840#1 (1), 7853#1 (2). Total: 4 H L range: 15-105 mm. Sounding range: 1203-1524 m. 113. Trachonurus villosus (GONTHER, 1877). 7822#7 (2). Total: 2 H L range: 46-80 mm. Sounding: 1203 m. 114. Sphagemacrurus hirundo (COLLE'rr, 1896). 7853#1 (2). Total: 2 H L range: 30-32 mm. Sounding: 1510 m. 115. Nezumia aequalis (GONTHER, 1887). 7810#1 (29), 7811#1 (9), 7838#1 (109), 7839#1 (28), 7840#1 (1), 7844#1 (15), 7845#1 (14), 7852#1 (3), 7975 (1), 7993 (5), 8003 (35), 8014 (80), 8519#7 (1), 8930#1 (28), 8931#1 (23). Total: 381 H L range: 11-56 mm. Sounding range: 307-1524 m. 116. N. sclerorhynchus (VALENCIENNES, 1838). 7811#1 (85), 7822#7 (5), 7851#1 (8), 7984 (3). Total: 101 H L range: 16-50 ram. Sounding range: 522-1203 m.
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117. N. micronychodon IWAMOTO, 1970. 7811#1 (1), 7838#1 (73), 7839#1 (14), 7993 (5), 8003 (18), 8012 (1), 8014 (51). Total: 163 H L range: 23--66 mm. Sounding range: 549-1261 m. 118. N. duodecim IWAMOTO, 1970.7811#1 (73), 7839#1 (341), 8012 (12), 8519#7 (1). Total: 427 HL range: 8-48 mm. Sounding range: 690-1261 m. Unid. Nezumia sp. 7811#1 (10), 7838#1 (6), 7840#1 (1), 7993 (8), 8003 (2), 8014 (9), 8020 (12), 8931# 1 (6). Total: 54 H L range: 7-22 mm. Sounding range: 279-1524 m. 119. Ventrifossa occidentalis (GOODE and BEAN, 1885). 7810# t (13), 7816#5 (5), 8020 (5). Total: 23 H L range: 34--64 mm. Sounding range: 279-307 m. Unid. macrourids 7838#1 (8), 8020 (12), 9134#0 (1). Total: 21 H L range: <12-35 mm. Sounding range: 279-1945 m. 120. Lyconus sp. 8931#1 (1). Total: 1 SL:380mm. Sounding: 981m. STEPHANOBERYCIDAE: 121. Malacosarcus sp. 8933#3 (1). Total: 1 S L : 4 0 m m . Sounding:2985 m. TRACHICHTHYIDAE: 122. Hoplostethus mediterraneus CUVIER, 1829. 7838#1 (15), 7844#1 (156), 7845#1 (1), 7851#1 (58), 7975 (8), 7993 (27), 8003 (20), 8014 (7), 8020 (80), 8930#1 (57), 8931#1 (1). Total: 430 SL range: 13-242 mm. Sounding range: 279-981 m. 123. H. cadenati QUERO, 1974. 7811#1 (29), 7816#5 (1), 8003 (2). Total: 32 SL range: 94-169 mm. Sounding range: 296--734 m. ANOPLOGASTERIDAE: 124. Anoplogaster cornuta (VALENCIENNES, 1833). 8519#7 ( 1). Total: 1 SL: 115 mm. Sounding: 1017m. ZEIDAE: 125. Cyttus roseus (LOWE, 1843). 7851#1 (4). Total: 4 SL range: 105-153 mm. Sounding:522 m. 126. C. hololepis GOODE and BEAN, 1895. 7816#2 (1). Total: 1 SL: 53 mm. Sounding: 291m. MACRORHAMPHOSIDAE: 127. Macrorhamphosus scolopax (LINNAEUS, 1758). 7845# 1 (1). Total: 1 S L : 9 9 m m . Sounding:952 m. SCORPAENIDAE: 128. Scorpaena maderensis VALENCIENNES, 1883. 7838#1 (2), 7839#1 (1), 7851#1 (1), 8003 (1), 8014 (3). Total: 8 SL range: 35-385 mm. Sounding range: 522-933 m. 129. S. elongata CADENAT,1945.8020 (3). Total: 3 SL range: 139-169 mm. Sounding: 279 m. 130. S. normani CADENAT,1945.7810#1 (3), 8020 (1). Total: 4 SL range: 84-99 mm. Sounding range: 279-307 m. 131. Helicolenus dactylopterus (DELAROCHE, 1809). 7810#1 (9), 7811#1 (1), 7843#3 (1), 7844#1 (7), 7851#1 (4), 8020 (62), 8930#1 (80), 8931#1 (6). Total: 170 SL range: 29-345 mm. Sounding range: 279-981 m.
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132. Trachyscopaea cristulata echinata (KOEHLER, 1896). 7844#1 (13), 8519#7 (1), 8930#1 (3), 8931#1 (6). Total: 23 SL range: 32-340 mm. Sounding range: 482-1017 m. COq'TUNCULIDAE: 133. Cottunculus thomsoni (GONTHER, 1882). 8001 (2). Total: 2 SL range: 61-267 ram. Sounding: 1458 m. 134. Cottunculoidessubspinosus (JENSEN, 1902). 7840# 1 (2). Total: 2 SL range: 48-52 mm. Sounding: 1524 m. APOGONIDAE: 135. Epigonus denticulatus DIEUZEIDE, 1950. 7844#1 (3), 7993 (2), 8930#1 (15), Total: 20 SL range: 19-114 mm. Sounding range: 482-690 m. 136. E. pandionis (GOODE and BEAN, 1881). 7816#5 (3). Total: 3 SL range: 86-123 mm. Sounding: 296 m. 137. Synagrops microlepis NORMAN, 1935. 7816#2 (1). Total: 1 SL: 116mm. Sounding: 291m. BRAMIDAE: 138. Brama brama (BONNATERRE, 1788). 8020 (2). Total: 2 SL range: 255-330 mm. Sounding: 279 m. PERCOPHIDAE: 139. Bembrops heterurus (MIRANDA-RIBEIRO, 1915). 7816#5 (1). Total: 1 SL: 176 mm. Sounding: 296 m. GOBIIDAE: 140. Gobius angolensis NORMAN, 1935. 8020 (3). Total: 3 SL range: 57-77 ram. Sounding: 279 m. Unid. gobiids 8020 (11). Total: 11 SL range: 14-31 ram. Sounding: 279 m. GEMPYLIDAE: 141. Nesiarchus nasutus JOHNSON, 1862.9133#7 (1). Total: 1 SL: 685 mm. Sounding: 2160 m. BOTHIDAE: 142. Chascanopsetta lugubris ALCOCK, 1894.7816#5 (1). Total: 1 SL: 131mm. Sounding: 296 m. SOLEIDAE: 143. Synaptura lusitanica (CAPELLO, 1868). 7839#1 (1). Total: 1 SL: 124 mm. Sounding: 933 m. 144. Bathysoleapolli (CHABANAUD, 1950). 7844# 1 (6). Total: 6 SL range: 60-153 mm. Sounding: 482 m.145. B. profundicola (VAILLArCr, 1888). 7810#1 (15), 7838#1 (2), 8014 (5), 8020 (25), 8930# 1 (2). Total: 49 SL range: 22-149 mm. Sounding range: 279-572 m. Unid. Bathysolea sp. 8012 (6). Total: 6 SL range: 19-30 mm. Sounding: 1261 m. Unid. juvenile soleids 7816#2 (2), 7838#1 (1). Total: 3 SL: 25 mm. Sounding range: 291-549 m. CYNOGLOSSIDAE: 146. Cynoglossus cadenatiCHABANAUD, 1947. 7811 # 1 (4), 7851# 1 (5). Total: 9 SL range: 53--67 mm. Sounding range: 522-690 m.
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N.R. MERRETrand N.B. MARSHALL
147. Symphurus nigricens RAFINESQUE. 1810. 7816#2 (3), 7816#5 (3), 7844#1 (3), 8020 (165). Total: 174 SL range: 29-107 mm. Sounding range: 279-482 m. 148. S. normani CHABANAUD, 1950.7810#1 (9), Total: 9 SL range: 47-104 mm. Sounding: 307 m. APPENDIX II
Stations and species (numbered according to list in Appendix 1) used in similarity matrices (a) 78 stations and 68 species used in the 2-dimensional ordination of intersample similarities (Fig. 3). Stations 7090# 1. 7091 # 1. 7092# 1,7 112# 1, 7810# I, 78 l 1# 1, 78 t3# 1.7814# 1,7815 #2, 7816#2, 7816#5, 7817# 1. 7822# 1,7822#2, 7822#5, 7822#6, 7822#7, 7838# 1,7839# 1, 7840# 1,7841#2, 7841#3,7841 #4, 7843#1, 7843#2, 7843#3, 7844#1,7845#1, 7846# 1, 7848# 1, 7848#2, 7848#3, 7849#1, 7851# 1,7852# 1,7853# 1,7854#2, 7975. 7984, 7991. 7993, 8001, 8003, 8012, 8014, 8020.8519#7,8521 # I, 8524# l, 8524#6, 8528# 1, 8540# 1, 8682#5, 8694#4, 8930# 1, 8931# 1, 8932#2, 8933#3, 8933#4,9128#6,9131 # 1,9131 #2, 9131#3, 9131#4, 9131#9, 9131#10, 913l#12, 9131#17, 9132#5, 9133#5, 9133#7, 9134#0, 9540#0, 9541 # 1,9541 #3. 9541 #5,9541 #6, 9541# 19. Species 1 , 5 , 6 , 7 , 8 , 10, 15, 18,22.23,25,28,31,33,34,35,36,37,38,43,45,49,50,51, 53, 57, 59, 61, 62, 65, 66, 67, 71,73, 74, 79,80, 86, 95, 97, 98, 99, 100, 102,103, 104, 106, 107, 110, 111,115,116, 117, 118, 119, 122,123, 127, 128, 130. 131,132,133. 134. 135,145,146, 147. (b) 54 stations and 61 species used in the 2-dimensional ordination of intersample similarities (Fig. 4), the l-dimensional ordination of inter-sample similarities (Fig. 5) and the single linkage cluster analysis (Fig. 6b). Stations 7090# 1,7091 # 1,7092#1,7810# 1,7811 # l. 7816#2. 7816#5, 7822#7, 7838# 1, 7839# 1, 7840# 1, 7844# 1, 7845 # 1,7846# l, 7851 # 1, 7852# 1, 7853 # 1,7975, 7984, 7991. 7993, 8001, 8003, 8012, 8014, 8020.8519 # 7,8521 # l, 8528 # 1,8540# 1,8682 #5. 8694 #4, 8930#1,8931#1,8932#2, 8933#3, 8933#4, 9131#1, 9131#2, 9131#3, 9131#4, 9131#9. 9131#10, 9131#12, 9131#17. 9132#5, 9133#5, 9133#7. 9134#0, 9540#0. 9541#1, 9541 #3, 9541#5, 9541#6. Species 7, 10, 15.18, 23, 28, 31,33, 34.35, 36, 37, 38, 43, 45, 49, 50, 51,53, 57, 59, 61,62, 66, 67, 7 l, 73, 74, 79, 80, 86, 95, 97, 98, 99. 100. 102,103,104, 106, 107, 110, 11 I, 115, 116, 117, 118, 119, 122, 123,127, 128, 130, 131,132, 133, 134, 135,145,146. 147. (c) 44 stations and 40 species used in the 2-dimensional ordinations of interspecies similarities (Fig. 7). Stations 7090#1,7091# 1,7092# 1. 7810# 1,78l l # l. 7816#2. 7816#5. 7822#7, 7838# 1, 7839# 1, 7840# 1, 7844# 1, 7845# 1,7846# 1,7851 # 1, 7852# 1,7853# 1,7975, 7984, 7991, 7993, 8001, 8003, 8012, 8014, 8020, 8519#7. 8682#5, 8694#4, 8930# 1,8931 # 1, 8932#2, 8933#3, 8933#4, 9131#1, 9131#2, 913l#3, 9131#17, 9132#5, 9133#5, 9133#7, 9134#0, 9541 #5,9541 #6. Species 18,.23, 28, 34, 35, 36, 37, 38, 43, 49, 51.53, 57, 61, 62, 66, 71,74, 79, 80, 95, 97, 99, 100, 102,103,110, 111. 115,116. 117, 118, 119, 122, 128. 131,132,145,146, 147.
Foolnotes ~Snout to caudal origin ~RMT8--benthopelagic capture
0079--6611/81/0301-0185505.00/0
Observations on the ecology of deep-sea bottom-Uving fishes collected off northwest Africa (08°--27°N) N.R. MERRETI'* and N.B. MARSHALLt
*Institute of Oceanographic Sciences, Wormley, Godalming, Surrey, U. K. t6, Park Lane, Saffron Walden, Essex, U.K. Abstract - - T h e ecology of bottom-living fishes was investigated from a series of collections off northwest Africa in the area 08°-27°N and 14°-300W from soundings of 261--6059 m. The variety of sampling gear included epibenthic sledges, a semi-balloon otter trawl, benthic traps and longlines. A total of 92 operations collected more than 4600 specimens of at least 148 species. The catches of both types of towed gear were shown to have a high degree of similarity, but sampled a different spectrum of species to the static baited gears. An overall consistency by latitude was found in the composition of the net catches. Despite possible indications of faunal boundaries at around 1100 m and 2100 m, the salient feature of an analysis of catch composition by sounding was the generally steady faunal change to a depth of about 3000 m. The only obvious discontinuity was evident at this level, beyond which the fish fauna was more uniform. This lack of marked species assemblages, characteristic of other regions, may result from the high primary productivity in the area. Features distinguishing the fish fauna of the area from that of the non-upwelling temperate western North Atlantic were found to be the smaller mean size of the dominant species, the abundance of bathygadine macrourids and the evident lack of the 'bigger-deeper' phenomenon. The relative density of fishes was estimated and shown to decrease by 2 orders of magnitude from the upper slope to 2000 m soundings. Below this the decline was less marked and relative densities of around 0.5 fish/1000 m z were maintained to at least 4000 m soundings. The abundance of slope fishes in the area was tentatively estimated to be greater than in the non-upwelling temperate western North Atlantic. Few species were abundant; only 25% were represented by more than 17 specimens. Yet the dominant family, the Macrouridae, was represented by 48% of the specimens and 18% of the species. A total of 14 species from 6 families, represented by 60 or more specimens, were examined in detail to provide information on vertical distribution, population structure, breeding biology and feeding. Niche availability and resource partitioning among cooccurring species of macrourids are briefly discussed. Station and species data are given, together with a note on the likely conspecificity of Coryphaenoides colon with C. zaniophorus.
CONTENTS Introduction Material and methods Sampling gear Treatment of samples Relative density of catch Statistical analysis of samples Limitation of sampling Results and discussion Catch analysis Analysis by latitude Analysis by sounding Analysis by species Relative density
186 187 190 192 192 193 194 196 196 196 197 201 206 185
186
N.R. MERRF"fTand N.B. MARSHAI.I
Species Account Synaphobranchidae - - Synaphobranchus kaupi Halosauridae - - Halosaurus (Halosaurichthys ) johnsonianus Macrouridae - - Trachyrincus trachyrincus
Bathygadus melanobranchus Coelorinchus coelorinchus coelorinchus Corvphaenoides (Lionurus ) carapinus Hymenocephalus italicus Nezumia aequalis Nezumia sclerorhynchus Nezurnia micronychodon Nezurnia duodecim Trachichthyidae - - Hoplostethus rnediterraneus Scorpaenidae - - Helicolenus dac~lopterus Cynoglossidae - - Symphurus nigricens Resource partitioning among macrourids Summary References Appendices Book Review INTRODUCTION
208 212 212 2/4 217 _[/
22(~ 22~ 221 224 22~ 226 22S 229 231 235 245
CONSIDERABLE ADVANCES in the study of organisms associated with the deep-sea floor have been made in recent years. Improved technology coupled with economic needs have b r o a d e n e d the scope, and increased the precision, of sampling this remote environment to encourage an extensive increase in scientific effort. Previously, knowledge of the zoogeographic and sounding distribution of fishes, their species assemblages and individual biolo,,v has largely been a byproduct of the systematic accounts of the major oceanographic expeditions. The increase in sampling intensity of deep-sea bottom-living fishes has allowed a shift in emphasis from such necessary systematic studies to preliminary ecological research. Much progress in this direction has been achieved in the western North Atlantic as a result of trawling surveys, of both a commercial (e.g. PECHENIK and TROYANOVSKII, 197(t: PODRAZHANSKAYA. 1971: SAVVATIMSKII, 1972: PARSONS, 1976) and a scientific nature (e.g. SCHROEDER, 1955: MARKLE and MUSICK, 1974: HAEDRICH, ROWE and POLLONI, 1975: MUSICK, WENNER and SEDBERRY, 1975: HAEDRICH and POLt,ONI, 1976: MUSICK, 1976: HAEDRICH and ROWE, 1077: SEDBERRY and MUS1CK, 1978), as well as through observations from submersibles (e.g. GRASSLE. SANDERS, HESSLER. ROWE and MCLELLAN, 1975: COHEN and PAWSON, 1977). Valuable complementary advances have been made in the Pacific. Time lapse photography of baits has been used to examine the role of benthic scavengers (e.g. ISAACS and SCHWARTZLOSE. 1975) and elaborate experimental trap systems used to investigate in situ respiration rates of fishes on the deep-sea floor (SMITH and HESSLER, 1974: SMITH, 1978). Recent effort in the eastern North Atlantic has been less prolific and largely dominated by exploratory commercial interest which has relied on trawling methods (e.g. MAURIN. 1968; WIllIAMS, 1968: GOI.OVAN, 1974: BAKKEN, [~AHN-JOHANNESSEN and GJOSAETER, 1975; BRIDGER, 1978). In addition various aspects of the ecology of deep-sea bottom-living fishes have
Ecologyof deep-sea bottom-livingfishes
187
been investigated also from trawl collections, such as zoogeography and sounding distribution (GOLOVAN, 1976: 1978), general biology (GOLOVAN and PAKHORUKOV, 1975: MARSHALL and MERRET'F, 1977; HUREAU, GEISTDOERFER and RANNOU, 1979), age and growth (RANNOU, 1973; 1976), reproduction (RANNOU, 1975: GEISTDOERFER, 1979), development (MERRETr, 1978) and feeding (GEISTDOERFER, 1973; 1975; DU BUIT, 1978; MACPHERSON, 1979). Sampling has also been carried out with traps and longlines. The former method has produced results on aspects of behaviour (GUENNEGAN and RANNOU, 1979), while research on zoogeography and sounding distribution (FORSTER, 1964; 1968; 1971) and feeding (CLARKEand MERRETT, 1972) have arisen from the latter. The present study arose from general biological interest in the upwelling region off northwest Africa. The samples were collected from upper slope to abyssal depths during a series of cruises within latitudes 08°-27°N spanning 8 years. A variety of aims were envisaged, of which the first is an assessment of the species diversity of the area by an assortment of samplers. Identification of specimens was facilitated by several systematic studies of previous collections in the region (KOEFOED, 1927; NYBELIN, 1957; IWAMOTO, 1970; BLACHE, CADENAT and STAUCH, 1970; MAUL, 1976) in conjunction with general taxonomic studies of selected groups. Possible variation of the catches by latitude is the next consideration, followed by an analys~s of the catches by sounding. Depth dependent faunal assemblages have been identified among fishes on both the Atlantic and Pacific slopes off America (HAEDRICH, ROWE, and POLLONI, 1975; DAY and PEARCY, 1968), which form a comparison with the situation prevailing in the area of high productivity off northwest Africa. While sampling limitations hamper inter-area comparisons of absolute catch abundance, several studies in the western North Atlantic have indicated a marked reduction in the relative density of fishes with depth (HAEDRICH, ROWE and POLLONI, 1975; MUSICK, 1976; HAEDRICH and ROWE, 1977; COHEN and PAWSON, 1977). This prompted a similar analysis among these 'Discovery' collections. Next, the abundant species are examined in more detail, centred on sounding distribution, population structure, breeding and diet. Finally, as species of the family Macrouridae dominate the samples, there is a discussion of their co-occurrence and resource partitioning. During the course of the study preliminary results were incorporated in a discussion of the existence of a benthopelagic fauna (MARSHALLand MERRETT, 1977). Also, some taxonomic problems arising from the collections have been considered separately (MARKLE and MERRETT, 1980; MERRETT, 1980).
MATERIALS AND METHODS The series of samples investigated were collected during eight cruises of RRS 'Discovery' over the period 1969-1977. Fifty-six stations were occupied in the area 08°59'-27°12'N and 14°51'-30°28'W in soundings of 261-6059 m, although most were concentrated in the slope waters off northwest Africa between 20°-27°N, east of 20°W (Fig. 1). More than one collecting gear was used on many of the stations. A total of 92 operations were carried out, 27 with an epibenthic sledge of 2.4 m2 mouth area, 24 with another epibenthic sledge of nearly 1.5 m" mouth area, 13 with a semi-balloon otter trawl of 13.7 m headline length, 3 with a rectangular midwater trawl of 8 m2 mouth-opening area, 16 by trap and 9 by longline. The full station data are given in Table 1.
188
N . R . MERRETr a n d N . B . MARSHAtA
TABLE 1. SYNOPSIS oFSTATION AND CATCH DATA (SEF.I'EX[ I~/)RGEAR NO[A FION5,
Fishing Duration
Position °N °W
Gear
Towed
2336-2336 2869-2869 3311-3311 2992-2921
2336 2869 3311 2956
30 30 30 311
4 2 3 I
6 2 4 I
3117 691/
25 33
16 21 4 3 -
154 263 10 18 -
I 7 t7 "~ I I
2 25 185 5 4 1
I 2 9 111 17 12 3 2 2 -
1 4 21 249 863 49
Station
Date
7090# 1 7091#1 71192# 1 7112#1 7810# 1 7811#1 7813#1 7814# I 7815#1 #2 7816#2
24.11.69 25. t 1.69 25.11.69 3(1, 1169
24°(11 ' 24°32 ' 25°117' 27o12 '
17°52 ' 18~'32' 19°11t' 15022 '
BN2.4 BN2.4 BN2.4 BN2.4
27.2.72 27,2.72 28.2.72 28.2.72 3.3,72
18°115.2 ' 18007.6 ' 18009.5 ' 18008.9 ' 111050.6 '
16°32.0 ' 16037.2 ' 16°38.11' 16038.2 ' 17025.5 '
BN2.4 3117-307 BN2.4 681-699 BLL 6111 (56 h o o k s ) T R A P B 578 T R A P B 612
3.3.72 4.3.72 4.3.72 4.3.72 5.3.72 5.3.72
10°50,1' 111°42.4 ' 111°44.2 , 10°43.4 ' 08°59.(I , 118058.7 '
17°25.4 ' 17~2.9' 17023.3' 17°32.2 ' 20019.8 ' 20o'20.3 ,
T R A P B 515 BN2.4 273-3119 BN2.4 271--32(I BLL 649 (57 h o o k s ) T R A P B 1153 BLL 1151 (55 h o o k s )
5.3.72 5.3.72 5.3.72 21.3.72 21.3.72 22.372 22.3.72 22,3.72 22.3.72 22.3.72 23.3.72 23.3.72 23.3.72 23.3.72 23.1t.72
08°59.() ' I18°59.(I ' 08°59.1' 21°29.6 ' 21033.0 ' 21°37.3 ' 21°39.5 ' 21°38.6 ' 21°37.9 ' 21038.3 ' 23°43.0 ' 23°42.0 ' 23°41.8 ' 23°41.6' 23°41.4 '
20°17.6 ' 20016.9 ' 2(I°16.3 , 17°39.1' 17052.4 ' 18°04.5 ' 17050.4 ' 17°5(I.3 ' 17°50.4 ' 17°51.9' 17°14.1' 17°14.6 ' 17°14.5 , 17°03.7 ' 17°04.1 '
TRAP TRAP BN2.4 BN2.4 BN2.4 BN2.4 TRAP BLL TRAP BLL TRAP TRAP BLI. TRAP TRAP
23.3,72
23°41.0 ,
17¢~14.7'
BL1,
632 (56 h o o k s )
23.3.72 24.3.72 24.3,72 25.3.72 25.3.72 25.3.72 25.3.72 25.3.72 26.3.72 26.3.72 26.3.72 26.3,72 19.7.72 21.7,72 23.7.72
23°43.3 ' 23051).5 ' 23°53,11 , 25°46.4 , 25°47.1' 25047.5 ' 25°45.0 ' 25043.6 ' 25049.5 ' 25051.7 ' 25°54.6 ' 25°54.3 ' 26°23.6 ' 25°26.11 ' 24°12.1 '
16°56.7 ' 17°05.9 ' 17~6.9' 15°57.1' 15°57.4 ' 15°58.2 ' 15°54.2 ' 15°47.9 ' 15°53,1' 16002.4 ' 15°51.8 ' 15°52.2 ' 14°51.1 ' 16°111.3' 17°07.1 ,
BN2.4 BN2.4 BN2.4 TRAP TRAP BId, BLL BN2.4 BN2.4 BN2.4 TRAP TRAP BN2.4 BN2.4 BN2.4
479-485 947.-958 1500-1504 929 976 985 (55 h o o k s ) 798 (55 h o o k s ) 486-559 933-1045 15(13-1518 1166 1102 7854,;34 890-811 1500-1521/
#5 7817#1 7822# 1 #2 #5 #6 #7 7838# 1 7839# I 7840# 1 7841#1 #2 #3 #4 7842# 1 #2 #3 7843# I #2 #3 7844# I 7845# 1 7846# I 7848# I #2 #3 7849# I 7851#I 7852# 1 7853# I 7854# 1 #2 7975 7984 799
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(Mins) Gear
Sounding (m) Range Mid-pt
~
B B
B B B B B B
B B
B B
1162 1164 12(1,'~1203 533-566 919-947 15(X1-1548 944 918 (55 h o o k s ) 898 947 (58 h o o k s ) 951 953 940 (56 h o o k s ) 614 623
. . . . . . . . . . .
~
~ ..........
~,4
Catch
Static
180 28(t 295 1811 291 296
44 47 150 330 143 3iX) 275
1203 549 933 1524
36 30 311 30 347 117 386 148 276 282
120
. . 1 1
285 228 15t) 482 952 1502
3(/ 32 31t 333 350 136 157
522 989 15111
311 29 32 31(1 23(1
814 85(1 1511/
.................
311 31t 31t
~. . . . . . . . . . . . .
~
~
....................
Spp.
...........
Nos
5 3 13 .
. I 14
3
3
14 15 4 1 2 4 3 1(1 7 14 1 4 6 7
291 153 7 1 4 6 12 121 19 85 3 22 25 12
~. . . . . . . . . . .
..........
~
189
Ecology of deep-sea bottom-living fishes
TABi.E 1 - - continued
Station
Date
7993 8001 8003 8012 8014 8020 8519#7 8521#1 #6 8524#1 #6 8528#1 8532#1 #6 8540#1 8682#5 8694#4 8930#I 8931#1 8932#2 8933#3 #4 9128#6 #10 9129#1 913l#1 #2 #3 #4 #9 #10 #11 #12 #17 9132#5 #7 9133#5 #7 9134#0 9540#0 9541#1 #3 #5 #6 #18 #19
23.7.72 24.7.72 25.7.72 26.7.72 27.7.72 27.7.72 23.6.74 25.6.74 26.6.74 28.6.74 28.6.74 2.7.74 5.7.74 5.7.74 10.7.74 7.2.75 9.2.75 30.10.75 31.10.75 31.10.75 1.ll.75 1.11.75 11.11.76 12.11.76 14.11.76 17.11.76 18.1!.76 18.11.76 18.11.76 19.11.76 19. l l . 7 6 20.11.76 20.11.76 21.11.76 24.11.76 24.11.76 25.11.76 26.11.76 26.11.76 14.4.77 15.4.77 15.4.77 16.4.77 16.4.77 18.4.77 18.4.77
* R M T closing nets
Position °N °W 24004.5 ' 22035.2 , 22°31.0 ' 20045.4 ' 20043.5 ' 20°45.l' 24002.2 , 20°46.9 ' 20"47.9' 2ff'45.5' 20044.3 ' 17038.7 ' 13047.8 ' 13048.2 ' 11015.9 ' 25033.6 ' 22°48.8 ' 25"00.5' 24058.8 , 24053.6 ' 24056.6 ' 24057.5 ' 24010.5 ' 24018.0 ' 23005.7 ' 20°17.2 ' 20014.8 ' 20010.6 ' 20008.5 ' 20018.3 ' 20°15. l' 20009.0 ' 20007.0 ' 20011.6 ' 20°50.1' 20058.8 ' 20057.5 ' 21009.0 ' 21054.6 ' 20055.8 ' 20007.0 ' 20008.1' 20016.8 , 20009.6 ' 20018.5 ' 20019.7 '
16°50.8 ' 17037.0 ' 17°20.6 ' 18002.2 , 17045.7 ' 17039.3 ' 16059.2 , 18053.4 ' 18053.4 , 22042.5 ' 22°44.4 ' 18"35.8' 18014.0 , 18"08.0' 18023.0 ' 16°40.1' 17042.4 , 16022.6 ' 16°3l.l ' 16054.7 ' 18'01.2' 17°57.1' 30°27. l' 30028.2 ' 27°58.7 , 2l°42.3 ' 21024.9' 21040.2 ' 21027.2' 21043.4 ' 2l°35.5 ' 2l°40.0 ' 21026.0' 21°37.0 ' 18°55.5' 18°59.1 ' 18013.7 ' 18°08.8 ' 18002.8 ' 18°09.6 ' 21025.3 ' 21°41.2 ' 21"30.9' 21"43.4' 21°41.2 ' 21°51.3 '
Gear
S oundi ng (m) Range Mid-pt
Hshing Duration (Mins) Gear Towed Static Spp.
BN2.4 BN2.4 BN2.4 BN2.4 BN2.4 BN2.4 BNI.5 BNI.5 BNI.5 BNI.5 BNI.5 BNI.5 BNI.5 BNI.5 BNI.5 BNI.5 BN1.5 OTSB 14 OTSBI4 OTSB14 OTSBI4 OTSBI4 BNI.5 BN1.5 BN1.5 OTSBI4 OTSBI4 OTSBI4 OTSBI4 BNI.5 BNI.5 BNI.5 BNI.5 RMT8 OTSB14 BNI.5 BNI.5 OTSBI4 BNI.5 BNI.5 BNI.5 BN1.5 OTSBI4 OTSB14 RMT8 RMT8
696--684 1457-1460 744-725 1238--1285 550-595 261-297 997-1037 3053--3058 3064--3070 4412--4412 4414-4416 3150-3155 3113-3119 2952-2958 3994-4005 3000-3000 1805-1807 501-520 955-1012 2344-2406 29802990 2962-2977 5726--5726 605%6059 5590--5590 4002--4007 3926--3927 3931-3935 386g-3879 4006-4015 3950-3952 3921-3921 3856-3861 3910-3995" 3089--3109 3083-3094 2112-2160 2130-2191 1942-1949 2005-2009 3850-3854 3910-3912 3936-3943 3929--3929 3790--4020* 3970-4044)*
30 31 30 30 29 33 47 36 31 98 76 33 39 54 37 146 32 30 64 60 60 70 10 50 42 62 54 77 115 39 43 37 39 192 82 60 47 40 36 36 34 32 86 74 360 360
690 1458 734 1261 572 279 1017 3055 3067 4412 4415 3153 3116 2955 3999 3000 1806 510 981 2375 2985 2984 5726 6059 5590 4004 3926 3933 3875 4010 3951 3921 3858 3149 3088 2136 2160 1945 2007 3852 391l 3939 3929
Nos
8 6 12 7 11 17 17 1
64 30 106 46 170 46O 269 1
1 1 4
2 2 6
1 7 4 14 24 7 6 3 1
1 9 8 241 376 8 9 3 1
5 5 3 2 1 2
19 12 7 2 2 2
l 7 II
l 18 24
4 12 3 1 1 1 6 5 1 2
9 34 4 2 1 l 45 6 1 2
190
N.R.
I
I
i
i
I
MERRETf and N.B.
I
1
I
MARSHALL
I
'
~
b
r
210W
3 0 ¸¸
],,.,,
v
/
CANA.~' ,S LL______~7112 ~
7853 7848 - 7849 _
~ :Z ~ - ~ _ _ _
_ _i~
8682_
__
7092 . . . . . . . 8933 ~
25
__
7846
:
~
~
.
~
. . . . . . . . . . . . .
~
5
-----
-
__
-
E
~
_
_
-
-
7
8
.
5
2
--
! '~
.
4 ~
.................
7842 . . . . . . . . . . . . . . . . . .
3
0
~-~e932 . ~ ~
~
_ _ . L ~ 7 9 9 3 8 5 1 9
~
8003 ~ ~ - -
7845 ~f"--,-,--~.~ 7844 ~' ~7843 = ~ - . ~ ..... ~94 ~ - ~ - - - - ~ / _7841
8012 ~
~
9132 8521 8524 i o 9131 - - o 9541 - - ~ - - ~
--
-
.9128 _9129 8001
"'20
.
Z.
7991 ~ 7090
7975'
7854 ~~78,54
.......
-
-
~
~
~
~
I ~
.
.
~ ~
_
.
~ 0
9133 9540
2
0 014
d
78!.3 8528
'
• t,, CAPE
--15
/
VERDE I S
LEGEND •
0 -
o
501-
•
1001-
1500
•
1501-
2000
•
2001-
2500
2501-
3000
3001
--10N
500
- 3500
D
3501 - 4000
o
4001-
8540 . . . . . . . . . . . . . . . . . . 7817 . . . .
m
25
I
,
t
L
o
4500
>5500
•
8532
1000
I
1
7822 . . . . . . . . . . . . I
L
I
1
1
I
t
L
i
L
5 I
I
Chart of the survey area with station positions indicated.by sounding range. (Arrows indicate the extent of the occurrence of strong upwelling throughout the year reported by W O O S T F R . B A ( ' K U N a n d M C L A I n , 1 9 7 6 ) .
FIG. 1.
Sampling gear The larger epibenthic sledge (BN2.4) was a forerunner of the smaller, radically modified sledge ( B N 1 . 5 ) described bv ALDRED, THURSTON, RICE and MORLEY (1976) and was superseded by the latl, ' du; ing the survey period. Both nets were designed to be general epibenthic samplers, although the BN2.4 had no blind to close off the fixed mouth opening and did not possess the elaborate acoustic telemetry or photographic facility of the later
Ecology of deep-sea bottom-livingfishes
191
design. A p a r t from the difference in the dimensions of the mouth opening of each net ( B N 2 . 4 : 2 . 4 m width x 0.8 m height vs. BN1.5:2.3 m width x 0.6 m height) the sampling efficiency of both was comparable, for they were constructed of the same combination of mesh sizes. Thus the body sections of both nets were made from 4.5 m m mesh, knotless terylene netting which was joined to codend sections of similar 1 m m mesh. Both nets t a p e r e d regularly to a diameter of 0.2 m and the whole underside and codend sections were protected by a coarse chafer net of about 10 m m mesh size. In each net the codend t e r m i n a t e d in a removable metal bucket. O t h e r similar features of importance in both nets were the double tickler chain slung across the frame anterior to the bottom edge of the net and the moulded polythene mesh covering the top and sides of the frame. The method of fishing the BN2.4 was also essentially the same as that given for the BN1.5 by ALDRED e t al. (1976), although a simple single pulse acoustic beacon was used to monitor the passage of the net in the manner described for trawling operations below. T h e semi-balloon trawl (OTSB 14), complete with " V " doors was obtained from the Marinovich Trawl C o m p a n y (Biloxi, Mississippi, U.S.A.). It was constructed of 4.4 cm stretch mesh body and 3.7 cm mesh intermediate and codend, with a 1.3 cm inner liner in the codend. Buoyancy on the headline was provided by 3 evenly spaced 25 cm CORNING glass spheres contained in polyethylene ' C a b l e m a t e ' cases. Each sphere gave a positive b u o y a n c y of 5.7 kg. Twentythree 13 × 15 cm plastic mud rollers were spaced evenly along the footrope (17 m), with three loops of 6 mm chain in between each set. A pair of sweeplines on each side separated the " V " doors by 8 m from the wing ends of the net. T h e height of the wing ends between headline and footrope was 1.5 m. The doors, each measuring 1.5 × 1 m and weighing 180 kg; were connected by bridles 50 m in length, through a swivel to the single trawl warp. T h e progress of the trawl throughout the tow was monitored from a 10 kHz acoustic beacon ( I O S T y p e H) mounted on a bracket attached to the sweepline, midway between the wing end and the door, on the leeward side of the net relative to the ship. In this orientation optimal signal strength of both the direct pulse from the pinger and that reflected from the seabed was obtained on the shipboard precision echo-sounder and displayed in real time on a M U F A X facsimile recorder. The arrival of the trawl on the seabed was observed on the facsimile display when the trace received directly from the pinger m e t the reflected pulse from the seabed and the two remained coincidental. Time on the b o t t o m was measured from this m o m e n t to that when the traces diverged once more after hauling began. The duration of the tow on the bottom was set in accordance with the sounding, from half an hour in 500 m to 1-2 hrs in 1000-4000 m (Table 1). If at any time in the duration of the tow the traces diverged, warp was paid out to settle the net on the sea floor once more. The ship speed was maintained at 2-2.5 knots (1.03-1.28 m/sec). The wing-end spread of the net was assumed to be 8.6 m, as 5/8 of the headline length while d o o r spread was estimated to be 13.3 m, on the assumption that the sweeplines were held at an angle of 17° to the direction of tow by the doors (J.P. BRIDGER, personal communication). United States Marine Fisheries Service data obtained from a similar size semiballoon trawl fitted with sweeplines of similar length and towed at a similar speed indicated that the m o u t h opened to a vertical height of 1.5-1.8 m with the footrope 0.6--0.9 m above the b o t t o m (F. WATHNE, personal communication). Experience has shown, however, that generally substrate and benthiq organisms as well as benthopelagic animals are collected, possibly as a result of uneven tension on the trawl transmitted through the warp. T h e b o t t o m traps used in the survey were of simple design and construction. Two kinds
192
N.R. MERRE'Frand N.B. MARSHALL
were used, one pyramidal in shape with a base length of 1.7 m and slant height of 1.5 m with 3 entrances (each 18 cm in diameter), the other rectangular, 0.6 x 0.4 × 0.4 m, with 2 entrances. The pyramidal traps were covered in galvanised wire netting (2.5 cm mesh). The base of one of these was covered in fine mesh fibre netting (2 cm stretched mesh) and the same materal was used to cover the rectangular trap. Each trap was baited with frozen mackerel and squid, and laid on polypropylene line (6 mm diameter) secured to a floating dhan buoy. Recovery was by means of a hydraulic M A R C O lobster power block after fishing times of 3--6.5 hr duration. T h e Iongline technique was developed from that described by FORSTER (1964). The groundline, of 6 m m diameter sisal (330 kg breaking load), was 500 m in length. Fifty or so snoods were attached to it at about 10 m intervals. Each snood was 1.5 m long with a snap-on connector at one end and a M U S T A D hook of incurved design on the other. They were made of plaited wire served with cotton thread (180 kg breaking load) with swivels incorporated 0.5 m from the hook. When shooting the longline, the ship lay-to and an 18 kg weight was attached to one end of the groundline and the latter paid paid out over the side, Baited snoods were clipped on as the groundline went out and finally the other end was connected both to a 9 kg weight and to the 6 m m polypropylene buoyline (960 kg breaking load). Five hundred metre lengths of buoyline were paid out until a scope of around 2:1 was reached, when the last length was secured to a dhan buoy. The M A R C O block was again used to haul the line.
Treatment of samples W h a t e v e r the collecting gear used, the fishes were sorted and fixed on board in 10~, seawater formalin, after preliminary identification. Ashore, the identities were confirmed and the appropriate measurements made for the species concerned (standard length (SL), total length (TL), head length (HL), gnathoproctal length (Gn.L. - - measured in a straight line from tip of lower jaw to anal opening) or snout to caudal origin - - see A p p e n d i x I), either by projection on a ruler, or by caliper, to the nearest millimetre. Body cavities were opened for gonad and alimentary examination. On microscopic examination, ovarian maturity was staged by a system of indices related to recognizable histological changes (MERRETT, 1971 - - see Table 2). Definitive stages in maturity of the testis were less easily recognized as some spermatozoa were present in almost all specimens, even m a n y of the apparently immature. Little additional evidence on the reproductive cycle could be provided by males, therefore, so the more precise staging of females was relied upon solely. Diets of the more abundant species were analysed largely from intestinal contents, necessitated by general possession of gas-filled swimbladders in these species often causing eversion of the stomach during ascent. Such analysis enabled a semi-quantitative appraisal of diet only.
Relative densi~ of catch This was estimated on the basis of area swept per tow for the epibenthic sledges and otter trawl, since all catches were considered to have been made while the net was in contact with the sea-floor (see Limitations of Sampling section). (Consequently all references to depths of capture are tacitly taken to be synonymous with the soundings fished - Cf. Species Account). The path width of the sledges was maintained by the frame of the net, while that of the trawl was taken to be the estimated wing end spread (8,6 m). The
Ecologyof deep-sea bottom-livingfishes
193
duration of the tow was timed from the arrival of the net on the bottom to the moment of lift off, observed from the M U F A X record. In this way, relative density (referred to in the Species Account simply as density) is expressed as the number of fish/1000 m 2.
TABLE2. STAGESINOVARIANMATURITY,MODIFIEDFROMMERRETT.1971
Immature virgin: Recovering spent: Yolk and chorion formation: Maturation of eggs:
Ovulation:
Spent:
Ovaries small, compact;yolk absent from oocytes. Ovaries somewhat flaccid, larger than Stage I; yolk absent fromoocytes. Ovaries firm, slightlyenlarged; yolk granules present and chorion layer forming around oocytes. Ovaries firm and distended. Eggs visible to the naked eye, opaque; yolk vesicles readily apparent, chorion fully formed. Ovaries distended to such an extent that the transparent eggs, enlarged by the uptake of liquid and freed from the chorion, are shed with or without slight pressure on the flanks. Ovaries extremely flaccid, either an enlarged but empty sac or shrunken with an enlarged central lumen.
(Stage I) (Stage VII/II) (Stage II)
(Stage III/V)
(Stage VI) (Stage VII)
Statistical analysis of samples Evaluation of the ecological data collected during this series of surveys necessitated some multivariate method of analysis. It was accepted that all such techniques now available are subject to some disadvantages. In the event, an ordination technique was chosen in which the similarities between samples, calculated in some way using the observed species abundance in each sample, could be used to provide a mapping of the samples onto some space of low dimensionality ( one or two). Obviously any such mapping would distort the inter-sample relationships to some extent, so an ordination method minimising this was chosen. Once the ordination was effected, the resulting plot of samples could be used to summarise the original data set. Hence samples with similar attributes would be close together on the ordination and dissimilar ones far apart. In this way patterns or clusters of samples could be discerned in the ordination space from which to classify the samples and hopefully to clarify the observed distributions of species within them. Initially, it was necessary to calculate a matrix of inter-sample similarity coefficients. Since these collections were obtained from a variety of non-quantitative samples it was considered inappropriate to use a quantitative similarity measure. Instead the J A C C A R D presence - absence index of similarity was chosen (JACCARD, 1912). A further complication was the large number of zeros in the original data matrix. Such heterogeneity is liable to produce misleading ordinations if the more common ordination method of principal
194
N.R. MERRETTandN.B. MARSHALl.
components is employed. FASHAM(1977) has shown by simulation techniques, however, that the method of nonmetric multidimensional scaling (KRUSKAL, 1964a and b) can cope with highly heterogeneous data sets such as these, so this method was used. Species, as well as samples, may be ordinated by the same technique, calculating a matrix of inter-species similarities before applying the nonmetric multidimensional scaling. Although both ordinations use the same data matrix, often they yield different sorts of information. Thus, as in this case, the sample ordination can often suggest determining factors for species distribution patterns, whereas the species ordination mainly defines species group or clusters of co-occurring species. Such divisions of species into groups using the two dimensional ordination plot was aided by the use of the minimum spanning tree (GOWER and ROSS, 1969). This tree was calculated from the similarity matrix and connected each species in such a way that its total length (measured in terms of species dissimilarities) was a minimum. In this way each species was connected to at least one other species with which it most often co-occurred. Thus, with the species points in the ordination connected up in the same order as in the minimum spanning tree, the resulting pattern could be used to help divide the ordination space into species groups. It also indicated the existence of such groups. For instance, if all the species were distributed evenly along a line then the minimum spanning tree would join all the species points up in a single chain to indicate that no groups could be defined.
Limitations of sampling The stations comprising the overall survey (Fig. 1) resulted from 8 cruises of 'Discovery', each of which contributed varying amounts of sampling effort (2-39 samples/cruise). The total effort was fortuitously divided into two periods by the types of gear used. On the 1969-72 cruises (52 samples), which took place during November, February-March and July, the only towed gear employed was the non-closing epibenthic sledge (BN2.4). In addition, all the static, baited gear (BLL and TB) fished was used during the earlier 1972 cruise only. Sampling during this period was concentrated in the midslope regions. In contrast, during 1974-77 when 40 samples were collected in June-July, February, OctoberNovember and April, the only gears employed were the mouth-closing epibenthic sledge (BN 1.5) and the much larger, but non-closing, otter trawl (OTSB 14). The majority of these samples were collected from soundings deeper than the slope-rise break which is close to 3000 m soundings in this area (see Table I). Furthermore, only 2 localities were revisited and sampled for seasonal variation (in degree square 20°N: 21°W (c. 4000 m sounding) and 20°N: 18°W (c. 2000 m). Hence this series of surveys comprises mostly non-seasonal spot samples, from which comparisons can only be made with tacit understanding of the imposed constraints. Certain deep-sea bottom collections have been utilized to estimate the abundance of various representatives of benthic megafauna (e.g. SCHROEDER, 1955, HAEDRICH, ROWE and POLLONI, 1975; MUSlCK, 1976; HAEDRICH and ROWE, 1977), The general limitations of such sampling and measurements of abundance were reviewed by HAEDRICH, ROWE and POLLONI(1975). They concluded that, while reasonable qualitative samples of the dominant species were obtained by trawling, the results provided an underestimate of absolute abundance. Their value was mainly in relative comparisons between samples in which the same net was used. In full agreement with these conclusions, estimates of relative density for the towed gears used during the 'Discovery' surveys have been made for bathymetric comparison within the overall study only,
Ecologyof deep-sea bottom-livingfishes
195
In detail, many of the limitations of sampling are common to all towed gears used in these surveys. While the arrival and departure time of the gear on the sea-bed was accurately known from the acoustic record and gross departures during tows were similarly monitored and allowed for, minor deviations may not have been observed. Photographic evidence has confirmed such skipping over the bottom with the epibenthic sledges (lOS unpublished data). This may result from towing speed fluctuations, which themselves may affect the catching power of the gear, especially in the case of the otter trawl. The scope of the warp (length of wire out to sounding) during fishing was variable, in the case of the OTSB 14 from 1.2-2.6, owing to the effect of surface conditions and/or current shear in the water column. Differing scope and set of the ship relative to the net rendered it impossible to determine the precise position of the net on the bottom. The sounding in which the net fished could thus only be determined from the ship's sounder, which in slope areas under adverse conditions may have recorded a depth somewhat different to the actual soundings fished. (Hence, in the Species Account the mid-point of the sounding range fished is taken as the measure of depth - - s e e Table 1). As a hydrodynamic sampler the otter trawl is subject to several anomalous factors. Door and wing end spread was not monitored while fishing, neither was headline height. Thus the effective dimensions of the net could only be estimated, although it was designed to spread approximately 2/3 of its headline measurement (=9.1 m) (S.J. MARINOVICH personal communication). Other available estimates vary, however, despite their being obtained from semi-balloon trawls of similar size and apparently rigged in the same way. For instance, MIDDLETON (unpublished report, Virginia Institute of Marine Science) measured the wing end spread of a 13.7 m OTSB 14 with 1.8 m leg-lines attached to 1.5 m x 1.0 m steel 'V' doors by readings from transducers mounted at the wing ends. At 2.5 kts the value he obtained was 6.7 m. On the other hand visual underwater observations on a similarly rigged net of the same dimensions gave a door spread of 9.75-10.4 m at about 2 kts (F. WATHNE, personal communication). Assuming the angle of the legs to diverge by 17° from the direction of tow, then the wing end spread is calculated to be 8.7-9.3 m. This is close to the value of 8.6 m, used here, derived from the factor of 5/8 of the headline length, which has been found to be the average spread under tow of most types of trawl measured (J.P. BRIDGER, personal communication). The latter value differs little in proportion from that used by BULLIS and CUMMINS (1963) on which HAEDRICH and HENDERSON (1974) based their calculations. The accuracy of this factor is probably well within limitations imposed by immeasureable variables. By fishing the OTSB 14 on a single warp, the bridles from the swivel to the doors may deflect some species from the path of the net, while the doors themselves and the sweeplines may have an opposite, herding effect. Other possibilities are the leakage of small specimens through the mesh and differential avoidance patterns. For instance in estuarine conditions the catching efficiency (percentage of fish in the path of a trawl captured) of selected species by a 6.1 m otter trawl was found to be species dependent and yet not to exceed 50%, with a standard error of 9-58% of the mean estimate (KJELSONand JOHNSON,1978). Another unaccountable variable for all non-closing nets is the depth at which specimens are collected. Evidence of the occurrence of adults of benthopelagic species far above the sea-floor and mesopelagic species close to it has been reviewed in a recent discussion on the trophic relations of slope-dwelling fishes (MARSHALLand MERRETI', 1977; see also SMITH, WHITE, LAVER, McCONNAUCHEY and MEADOR, 1979). Both the BN2.4 and the OTSB 14 collected midwater fishes in small numbers. Yet, while no check was possible on
196
N.R. MERRE'rr and N.B. MARSHALl
benthopelagic species being caught in midwater, the catches of the BN1.5 were used by analogy to assess the amount of contamination from truly midwater species. At Stns 9131 and 9541 where the OTSB 14 and BN1.5 were both fished on several occasions in soundings of around 4000 m, the OTSB 14 collected Serrivomer, nemichthyids, bathylagids, gonostomatids, searsiids, myctophids, cetomimids, ceratioids and melamphaids in small numbers in all hauls. None was collected in the BNI.5, with its blind to keep the entrance closed other than when the frame is in contact with the bottom. No comparable test was available in slope waters but, as the OTSB 14 catches of similar midwater species was not conspicuously greater over the slope, it was decided to discount all from consideration. RESULTS AND DISCUSSION
Catch analysis The total collection comprised 4671 specimens representing at least 148 species from 42 families. The overall catch data are given in Appendix I, together with the length and sounding range of capture for each species. Most species were not abundant. Only 25% were represented by more than 17 specimens (Fig. 2). While it was to be expected that the majority of specimens and species should have been collected by the more widely used towed gear, it is evident that these sampled a different spectrum of species from the static baited gear. This was demonstrated by analysis of the total number of benthic samples (78) containing the 68 species which occurred in more than one sample with the 2-dimensional ordination plot, interpreted by means of the minimum spanning tree method (see Appendix II). This separated the collections into 2 groups and also indicated, with only one exception, that the catches of the towed gears alone had a high degree of similarity and so could be considered compatible (Fig. 3). Although the total catch from traps and Ionglines constituted only about 2% of the overall collection, these gears attracted a disproportionately large number of elasmobranchs (71-77% trap and longline catch) relative to the sample taken by the nets ( < l % net catch), to account largely for the sampling dissimilarity. A total of 132 species were collected exclusively by the towed gears, and 8 species (Myxine sp. nov., Etmopterus princeps, Centrophorus granulosus, C. squamosus, Centroscymnus cryptacanthus, Scymnodon ringens, Deania profundorum and Uroconger vicinus) by baited gear alone. Eight species also (Centroscymnus coelolepis,
Deania calcea, Raja nidarosiensis, Synaphobranchus kaupi, Simenchelys parasitica, Mora moro, Trachyrincus trachyrincus and Helicolenus dactylopterus) were common to the catches of both methods of sampling. The limitation of even the relatively large otter trawl in efficiently sampling large and active species such as squaloids is amply demonstrated by these results, caused possibly by the effect of the converging bridles ahead of the net (see above).
Analysis by latitude Two of the most likely identifiable factors influencing the distribution of species throughout the survey area are latitude and sounding. To investigate these a 2-dimensional ordination of inter-sample similarities was obtained from 54 stations, sampled with towed gears only, and 61 species (Fig. 4 and Appendix II). From this the first (vertical) ordina-
Ecologyof deep-seabottom-livingfishes
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FIG.2. Histogramof speciesabundance. tion axis can be identified with sounding. Generally, shallow stations have the highest positive scores on the vertical axis, while deep stations have the greatest negative ones. The scatter of stations, indicated by symbols denoting latitude ranges in the figure signifies that the second (horizontal) ordination axis, however, has no apparent correlation with latitude. This excludes the need for further consideration of latitude as an important influential factor in the area. It follows, therefore, that to investigate the influence of sounding sampled on distribution it will only be necessary to carry out a 1-dimensional ordination of inter-sample similarities.
Analysis by sounding One dimensional ordination of 54 stations and 61 species (see Appendix II) shows a generally close correlation between the haul composition of the towed gears and the sounding sampled (Fig. 5). With few exceptions (one notably from Stn 8521# 1 where one specimen of an unusual species, C. (Chalinura) leptolepis, was the only catch), the catch composition altered steadily with sounding to around 3000 m. The lack of stepwise
N.R. MERRETTand N.B. MARSHALl.
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Fl~i 3. A 2-dimensional ordination of the inter-sample similarities obtained from 82 stations (sampled with various gears) and 68 species• The minimum spanning tree linkages were used to divide the stations into two groups showing the general distinction between the catch compositions of towed and static gear. distribution shallower than 3003 m is indicative of continuous, rather than intermittent, faunal change. Such results contrast with those from slope surveys carried out on both the east and west coasts o f North America where bathymetric faunal discontinuities were apparent ( D A Y and PEARCY, 1968 - - fish; HAEDRICH, ROWE and POLLONI, 1975 - echinoderms, arthropods and fish; MUStCK, 1976 - - fish; GARDINER and HAEDRICH, 1978 - - mainly echinoderms but also includes fish). In view o f these findings, the same intersample similarity matrix used in the ordination was subjected to a single linkage cluster analysis to provide a more direct comparison with those from another region of the North Atlantic. This facilitated close, but not exact, c o m p a r i s o n with the results of HAEDRICH, ROWEand POLLONI (1975) from the northwest Atlantic, south of N e w England. These authors used a slightly different clustering strategy and similarity measure to those available to us, yet the methods are sufficiently close for preliminary comparison. The catch composition of stations from south of N e w England clustered into 3 markedly dissimilar groups (Fig. 6a). The clustering divided the slope into
Ecology of deep-sea bottom-livingfishes
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FIG.4. A 2-dimensional ordinationof the inter-sample similaritiesobtained from 54 stations (sampled by towed gear only) and 61 species. The first (vertical)ordinationaxis can be identifiedwith sounding,but no correlationis apparent between latitude and the second (horizontal)ordinationaxis. shallow (141-285 m), middle (393--1095 m) and deep (1270-1928 m) faunal zones, whether all taxa were considered or fish alone. Five clusters occur among the northwest African data at an arbitrarily chosen similarity level of 3.5 (Fig. 6b). Two of these (279-1017 m (15 samples) and 1203-2160 m (4 samples)) loosely correspond to the middle and deep clusters of HAEDRICH, ROWE and POLLONI (1975). (Comparison between the two studies of any shallow zonation is precluded by the upper sounding limit of 279 m off northwest Africa). A third cluster (2136--4004 m (17 samples)) lies beyond the sampling range of HAEDRICH, ROWE and POLLONI (1975), but is in general agreement with the results of GARDINER and HAEDRICH (1978), also from south of New England. They found that little zonation occurred below 3000 m. The remaining two clusters in the northwest African data, at around 1500 m (3 samples) and between 2007-4010 m (2 samples), arise from limited catches of unusual species and probably can be considered artefacts. The clustering of samples indicated by the above analysis has been superimposed on the 1 dimensional ordination plot (Fig. 5). It should not be implied that the 3 main clusters, which incidentally incorporate only 66% of the samples, necessarily substantiate the existence of conspicuous faunal zonation. For instance, over the comparable sounding
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range there is a much greater degree of overall similarity in the cluster analysis of the northwest African samples. Moreover, the stalk lengths between adjoining clusters in the African data are much shorter than their counterparts in HAEDRICH, ROWE and POLLONI's (1975) analysis, which might indicate a greater inter-cluster similarity although such a difference could be a function of the clustering method. It is clear that these preliminary results require confirmation, but the suggestion is that, while zonation may be found shallower than about 3000 m, faunal discontinuities on the northwest African slope are less trenchant than in the temperate western North Atlantic. If this conclusion does reflect the true situation off northwest Africa, it may well be that the recent study of NICHOLS and ROWE (1977) highlights the prime cause. In a survey of the infaunal macrobenthos off Cap Blanc, Spanish Sahara, in which organic carbon and nitrogen measurements were also made, they show that "faunal communities reflect the high primary productivity in the water column (about twice that off the northeast United States) by maintaining a high biomass as depth of water (to 1830 m) and distance from the shore increase." Further they indicate that the offshore upwelling province may produce as much as or more than the near shore province. Confirmation is given by THIEL (1979; in press) at least in the 500-2000 m sounding range, by meiofaunal densities and chloroplastic pigment equivalents in the sediment which indicate high levels of organic sedimentation. Such trends may well be reflected in a reduced pressure for resource partitioning in the fish fauna which obscure marked zonation.
Ecology of deep-sea bottom-living fishes
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FtG. 6a. Dendrogram from a cluster analysis based on data for all taxa (fish, echinoderms, arthropods, coelenterates, polychaetes and molluscs) collected from south of New England by a 4.8m semi-balloon trawl. The column to the left is the mean depth of each station. Canyon stations are marked thus • . The between-samples measure of overlap is percentage similarity and the clustering strategy is unweighted pair-group. (Redrawn from HAEDRICH, ROWE and POLLONI, 1975).
Analysis by species For this examination the data were selected to provide maximum information on the interrelationships of species. The more abundant species to occur in more than 2 samples from the towed gears were chosen, while the catches selected contained 1 or more representatives of at least 2 chosen species. The resultin&2 dimensional ordination of 40 species from 44 stations (see Appendix II) using the minimum spanning tree method sheds new light on the data from that given by the one dimensional ordination by sounding. Judged on the number of linkages and their separation distances, and remembering also that cross-overs indicate a third dimensional plane, two main groups can be distinguished (Fig. 7). Group I comprises the majority of species. Those of group II are more remote, with more tenuous interrelationships. Indication of this division has already been made by the change in slope in the one dimensional ordination (Fig. 5). The general orientation of the 2 dimensional ordination denotes a trend among the species which can be recognized as a bathymetric relationship, when the sounding distributions of species are plotted in JPO 9:4 - B
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Fl¢; 6b. Oendrogram from a cluster analysis of the same inter-sample similarity matrix as used in the I- and 2-dimensional ordinations in Figs. 4 and 5. The column to the left gives the midpoint of the sounding range sampled. Between samples measure of overlap is Jaccard coefficient presence/absence and clustering strategy is single linkage.
approximately the same arrangements as indicated by the minimum spanning tree (Fig. 7). The two major groups comprise co-occurring species with related down-slope distributions (Fig. 8). Acknowledging the overlap in the bathymetric ranges of the species comprising the groups, the members of group I are essentially the upper and mid-slope fauna. Species of group II occupy the lower slope and continental rise. There is perhaps some indication of zonation among these more abundant species with possible discontinuities at around I000 m and 2000 m in concurrence with the groupings tentatively suggested by the single linkage cluster analysis of a wider spectrum of species and stations (Fig. 8). Notable among the members of group I are three species, Aldrovandia affinis, Bathypterois dubius and Gadomus longifilis, isolated from the rest (group IA - - Fig. 8). Moreover, the three samples containing these species together, from 1502-1510 m, form a distinct group in the above cluster analysis separating at the 0.5 similarity level (Fig. 6b). From the limited data available this separation may be attributable to the particularly restricted bathymetric ranges of A. affinis and G. longifilis, It is evident from Fig. 8 that a trend towards the extension of bathymetric range exists among progressively deeper-living species. A similar trend has been observed among slope fishes off the western United States (DAY and PEARCY, 1968).
Ecologyof deep-sea bottom-livingfishes
203
2'0 34
17
5
3 1'0 2
22 8
I J
1.
-,!0
/
33
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FI(~. 7. A 2-dimensional ordination of inter-species similarities obtained from 44 stations (sampled by towed gear only) a n d 40 species. T h e m i n i m u m spanning tree linkages have been included to indicate grouping a m o n g the species. T h e numbering of species is given in Fig. 8.
GOLOVAN (1978) presented data on the composition and distribution of slope fishes collected from northwest Africa (0°-36°N - - equator to Gibraltar), augmented by a review o f the reported species from the area. The present results contrast somewhat with GOLOVAN's results from a broader latitudinal range. His findings indicate that transitional zones of species composition in soundings of 200-500 m and 2000-2600 m demarcate the slope fauna. This bathyal zone is subdivided by a further transitional zone in 1000-1300 m soundings. From the 120 species included in the upper zone, the most characteristic
t
2.0
204
N.R. MERRETT and N.B. MARSHALL
S o u n d i n g Ronge{M)
N9
0
1000
2000
3000
4000
16 Echelus pachyrhynchus 36 Ventrifossa occidentalis 38 Symphurus nigr icens ~4 Uroconger vicinus 12 Coelorinchus c o e l o r i n c h u s 7 Bothysolea profundicota 25 Hymenocepholus italicus 2 4 Hoplostethus mediterraneus 23 HaJosaur us ovenii 40 Trachyscorpaea cristulata 10 Chaunax pictus 35 Scorpaena maderensis 9 Helicolenu s dact ylopterus 27 Laemanema laureysi 39 Trachyrinc us t r a c h y r i n c u s 3l Nezurnia aequalis 37 Synaphobranchus kaupi 19 Nezumia micronychodon 6 Bathygadus melanobr anchus 11 Cor yphaenoides zaniophor us 8 Cynoglossus cadenati 2 Alepocephalus rostrotus 33 Nezumia sclerorhynchus 21 Halosaurichthys ]ohnsonianus 30 Notocanthus bonapar tei 26 ~eptoderma rnocrops 20 dalosourichthys guentheri 32 ~lezu rnia duodecirn 15 )icrolene intronigra 4 1
18 13 29 28 22 5 3 17 34
Aldrovandia affinis Gadomus Iongifilis Coryphaenoides g0ntheri Bathyonus sp. C.(L ionurus)carapinus Halosaur opsis macrochir Bathypterois Iongipes Bathytyphlops sewelli Conocara salmoneo Rinoctes nasutus
Ia
II i
m
F'I~; ~. Sounding ranges of species used in the 2-dimension ordination of inter-species similarities in Fig. 7. Species are arranged in the approximate order given by the minimum spanning tree linkages. Grouping in Fig. 7 indicated on the right.
GOLOVAN considered to be 3 scyliorhinid, 11 squaloid, 6 searsiid, 4 congrid, 5 morid, 14 macrourid and 3 trachichthyid species. He placed a further 101 species in the lower zone, among which alepocephalids displayed the greatest diversity and biomass (e.g. see GOLOVAN, 1974). The dominant families in the 150 or so species from the present series of surveys are the Macrouridae, represented by 26 species, the Alepocephalidae, (12), the Ophidiidae (9), Squalidae, Halosauridae and Chlorophthalmidae (8 each), and Synaphobranchidae (6). In terms of the most abundant species considered in the 2 dimensional ordination above (Fig. 7), all species in group I, apart from A. affinis and G. longifilis in group IA, were encountered by 1000 m soundings. A single member of group II, Bathyonus sp., had an
Ecologyof deep-sea bottom-livingfishes
205
upper limit of distribution shallower than 1000 m soundings. So, macrourids dominated with 10 species represented, followed by halosaurs and scorpaenids (3), and alepocephalids, ophidiids and cynoglossids (2). In group II only Halosauropsis macrochir, C. (Coryphaenoides) gfintheri and C. (Lionurus) carapinus occurred within the 1300-2600 m zone designated by GOLOVAN (1978). The contrast in relative dominance of the Macrouridae and Alepocephalidae between the two studies is notable, especially from the lower slope. Gear selectivity and the latitudinal ranges sampled ((08°-) 18°--27°N versus 0°-36°N) may largely account for these differences (see below). GOLOVAN (1978) pointed out that there is a regular decrease in bottom temperature over the slope from north to south. This affects not only vertical but geographic distribution. South of Cape Verde (14°45'N) the vertical limit of the transition between upper and lower bathyal zones is displaced upwards as a result of upwelling. The present collections were concentrated to the north of Cap Blance (20°46'N - - Fig. 1), so it is unlikely that this feature should have been revealed. In this connection it is notable that, among fishes of the shelf and upper slope (to about 600 m soundings), MAURIN (1968) "recognized a faunal boundary at the approximate latitude of Cap Blanc. This separated essentially tropical species from those of a more northerly fauna. It is of interest to compare the species composition from the region of upwelling in the eastern North Atlantic with that from the non-upwelling area of the temperate western side of the North Atlantic. COHEN and PAWSON (1977) state that the species diversity of the benthic slope fish fauna of the latter area is 100 or more species. Furthermore, they point out that more species are seen or photographed from submersibles than are caught in trawls. This observation and the results of the literature review by GOLOVAN (1978) indicate that the 150 or so species collected in our survey must fall considerably short of the total. Hence, the species diversity off northwest Africa is likely to be about twice that from a similar sounding range in the temperate western North Atlantic, a trend found commonly between tropical and temperate communities from other marine habitats (cf. MOORE, 1972). Another difference between the two areas is evident in the mean size of the dominant species collected in medium-sized nets. Those species from the northwest African regions are generally smaller than their counterparts in the temperate western North Atlantic. For instance, there are 11 species centred in the upper 2000 m soundings (Group I - - Fig. 8 and Appendix I) represented by >100 specimens in our collections (Synaphobranchus kaupi (169 specimens), Halosaurichthys johnsonianus (523), Bathygadus melanobranchus (407), Hymenocephalus italicus (293), Nezumia aequalis (381), N. sclerorhynchus (101), N. micronychodon (163), N. duodecim (427), Hoplostethus mediterraneus (430), Helicolenus dactylopterus (170), Symphurus nigricens (174)). In contrast, the dominant species in the upper 2000 m of slope in the temperate western North Atlantic are evidently (also in phylogenetic order) Synaphobranchus kaupi, Alepocephalus agassizii GOODE and BEAN, 1883, Phycis chesteri GOODE and BEAN, 1878, Merluccius albidus (MITCHILL, 1818), Dicrolene intronigra, Lepophidium cervinum (GOODE and BEAN,. 1886), Coryphaenoides rupestris GUNNERUS, 1765, Nezumia bairdii (GOODE and BEAN, 1877), Antimora rostrata GI]NTHER, 1878, Lycenchelys verilli (GOODE and BEAN, 1877), Helicolenus dactylopterus, Citharichthys arctifrons GOODE, 1880, and Glyptocephalus cynoglossus (LINNAEUS, 1758) (MARKLE and MUSICK, 1974; HAEDRICH, ROWE, and POLLONI, 1975; MUSICK, WENNER and SEDBURY, 1975). Thus the species composition of the dominant forms in the western North Atlantic is largely different, in addition to the larger mean size attained. It is notable that the bathygadine group of
206
N.R. MERRETTandN.B. MARSHALL
macrourids, which are abundant in the upwelling region, are absent in the temperate zone. T h e r e is a more trenchant difference between the two regions in the fauna from soundings greater than 2000 m. Coryphaenoides (Nematonurus) armatus is the dominant species of the continental rise in the temperate North Atlantic (MUSICK, WENNER and SEDBURY, 1975; COHEN and PAWSON, 1977), constituting as much as 80% of the fish biomass there (HAEDRICH and ROWE, 1977). The species was represented by only 4 specimens in these collections from the upwelling region. Although the dominant species below 2000 m off northwest Africa C. (Lionurus) carapinus (62 specimens) seems to occupy a similar niche in both areas (cf. HAEDRICH and POLLONI, 1976), there appears to be no counterpart of the large and ranging C. (N.) armatus. Hence, in the northwest African area it would seem that the 'bigger--deeper' phenomenon (MUSICK, 1976: HAEDR1CH and ROWE, 1977), in which mean fish size increases with sounding, does not apply. Possibly its absence may be correlated with the same selective pressures which cause the predominance of small fish on the slope. In his study of metabolism by in situ measurement, SMITH (1978) showed that C. (N.) armatus is a species adapted to the deep-sea by having a low metabolic rate and storing sufficient energy to exist for extended periods without eating. Thus by analogy large size may be adaptive to other food-limited conditions, such as occurs cyclically in regions of marked seasonality. For instance, in the temperate western North Atlantic large mean size with sufficient nutrient storage capacity to tide fish over periods of food shortage could be expected at all depths. Conversely, if conditions remained similar throughout the year with uniformly high productivity, selection may favour species of a small mean size with a smaller capacity for nutrient storage which otherwise have a greater competitive ability to exclude C. (N.) armatus on the continental rise. Conditions such as these apparently prevail off northwest Africa, at least between 20°-25°N where the majority of our samples were collected and where strong upwelling occurs throughout the year (WOOSTER, BACKUN and MCLAIN, 1976).
Relative density Estimation of the relative density of fishes from these collections provides a basis for comparing abundance from different bathymetric levels of the area surveyed (see Limitations o f sampling). The results in terms of relative abundance per 1000 m e are given in Fig. 9, for the epibenthic sledges and otter trawl respectively. The catches on the upper slope were close to I00 fish/1000 m'-', but they declined exponentially with depth to about two orders of magnitude lower in soundings of around 2000 m. Deeper than 2000 m the decrease in relative density was less marked and was maintained around 0.5/1000 m 2 at least to 4000 m soundings. (The high catch per unit effort in 5700 m from the BN1.5 can be explained from the capture of a single fish from a tow of very short duration - - Table 1). Such a decrease in relative abundance is in general agreement with trawling results and submersible observations from the middle Atlantic slope of the USA (HAEDRICH, ROWE and POLLONI, 1975; MUSICK, 1976: HAEDRICH and ROWE, 1977; COHEN and PAWSON, 1977). This inverse correlation between abundance and depth agrees with patterns indicated by the macrofauna (ROWE, POLLONI and HORNER, 1974) and to a lesser degree by the meiofauna (THIEL, 1975). Despite earlier remarks (p. 194) on the danger of comparing estimates of absolute abundance from one area to another when collected by different gear, there is reason here to draw some tentative conclusions by analogy with results from the western North
207
Ecology of deep-sea bottom-living fishes
v
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FIG. 9. Relative density of total catches made by the towed gears plotted against the mid-point of the sounding
range sampled.
Atlantic. HAEDRICH, ROWE and POLLONI (1975 - - Table 7) show that more individuals are seen from submersibles than are caught by nets. At around 1000 m the estimate of abundance calculated from photographs was two and six times greater than that estimated from catches o f a 12.2 m and a 4.8 m semi-balloon trawl, respectively. With this in mind, the abundance o f fish down the slope off northwest Africa (Fig. 9) is found to be much the same as that calculated from photographic series taken from a submersible by HAEDRICH and ROWE (1977 - - Table 1) in 497-278 m soundings in the temperate western North Atlantic. H e n c e , it is probably safe to assume that slope fishes off northwest Africa are m o r e abundant than in the latter area, and that the greater productivity induced by upweiling along the African coast is responsible for this difference. Regrettably the fresh weight o f catches was not recorded in the present survey with which to compare biomass from the two areas.
208
N.R. MERRETrand N.B. MARSHALl.
Although not comparable with the results from the towed gear, catch per unit effort has been calculated for the longline operations on the basis of catch per hook hour (Table 3). O v e r the 9 operations (55-58 hooks/operation) the mean catch was found to be 0.04 fish per hook hour weighing 0.15 kg per hook hour. T A B L E 3. C A T C H PER UNIT EFFORT (kg AND NUMBERS/HOOK HOL1R} FOR BOVI'OM LONGI.INE OPERATIONS
Stn. 7813# 1 7843#3 7817# 1 7849# 1 7841#2 7842#3 7841#4 7841#3 7822#2
~ 601 632 649 798 918 94(1 947 985 1151
6 56 56 57 55 55 56 58 55 55
~ .=_. ~ E
Catch WI.
No.
180 150 150 157 117 120 148 136 143
13.1 13.5 12.11 47.0 27.5 33.4 311.5 4.7
10 3 5 12 5 0 13 6 1
~ ,~ !).08 0. Ii1 [).()8 0.33 0.26 o.23 IL24 0.04
6 ,-
0.116 I).112 0.04 11.08 0.115 11.119 0.115 (].ill
Species account Some ecological aspects of the relatively abundant species were examined. Those species represented by 60 or more individuals were chosen and totalled 14 only of the 148 species collected. Consequently, one species each of the families Synaphobranchidae, Halosauridae, Trachichthyidae, Scorpaenidae and Cynogiossidae are considered here, together with 9 species of the family Macrouridae. All but one of these are slope dwellers, the majority being most abundant in soundings of less than 1000 m.
SYNAPHOBRANCHIDAE
Synaphobranchus kaupi According to the submersible observations of COHEN and PAWSON ( 1 9 7 7 ) S. kaupi is a benthopelagic species which swims above or along the bottom or may hover at any angle, head up or down. It has a capacity to reverse its forward swimming rapidly, which led them to conclude that it may easily avoid capture by towed nets. Such evasion might explain the fact that S. kaupi was never very abundant in catches (maximum density 6 fishtl000 m" - Fig. 11), although it was the most ubiquitous slope-dwelling species collected. Yet the greater relative abundance of this species to the north, collected with the same gear (IOS unpublished data), suggests that these values probably reflect true proportional abundance. A total of 169 specimens were taken in 21 samples spanning a range of 482-2160 m (Appendix I and Fig. 11). From the same general sampling area GOLOVAN (1978) reported this species from the range 90101700 m. On the western side of the Atlantic, HAEDRICH, ROWE and POLLON111975) found S. kaupi to be most abundant in soundings
209
Ecology of deep-sea bottom-living fishes
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FI(; l 1. Sounding distribution (shaded) of some of the more abundant species sampled on the slope by towed gears ( ---, indicates OTSB 14 samples). Relative density indicated as in Fig. 10, o f 3 9 3 - 1 0 9 5 m and it was also the top ranking species observed by MARKLE and MUSICK (1974) at 900 m. From the present results its abundance is apparently not concentrated in any part of its vertical range. It is generally less abundant, h o w e v e r , than on the slope to the north o f the Canaries off M o r o c c o (IOS unpublished data). The samples reported here c o v e r the size range 91-605 m m SL and length-frequency analysis suggests a 5 - p e a k e d distribution (Fig. 12). Most s p e c i m e n s were in the 200-300 m m SL size range and found to
Ecologyof deep-sea bottom-livingfishes
211
be sexually immature. Beyond occasional observations, however, gonad examination was not undertaken for this species. Preliminary investigation of the diet of S. kaupi was made from 14 stomach contents (Table 4). As previously noted it feeds largely on pelagic items (MARSHALL and MERRETT, 1977) which agrees with findings from collections made o f f t h e eastern United States by MUSICK, WENNER and SEDBERRY (1975) and SEDBERRY and MUSICK (1978). Fish remains were the main component and occurred in 71% of the stomachs. Identification of these remains was possible in only 2 instances. One was a myctophid, while the other was the skull of Macrorhamphosus scolopax. The latter occurred in a sample from 952 m sounding in which a free adult of this species was also taken. In addition, some of the fish remains were parts of larger individuals than apparently could be eaten whole by the predator. Such occurrences suggest a scavenging role in this species (cf. CLARKE and MERRETT, 1972). Crustacean remains, mainly decapod, were the next most abundant food item found in 29% of the stomachs. Squid were almost as abundant, apparently Rossia type (N. MacLEOD personal communication), found in 21% of stomachs. One stomach contained chaetognath remains. Synaphobranchus kaupi
20
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FIG. 12. Synaphobranchuskaupi (Standard) length-frequencydistributionof the total sample (n = 167).
2 l -~
N.R. MERRE'rr and N.B. MARSHAI.I
HALOSAURIDAE
Halosaurus ( Halosaurichthys ) johnsonianus This species was the most abundant halosaur in the collections (523 - - Appendix I). although largely due to its presence in high density at 2 of the 8 stations at which it was sampled (27 and 100 fish/1000 m'). Its depth distribution indicated that it is a mid-slope species, most abundant around 1000 m but extending from 690-1524 m soundings (Fig. 11). The overall size range was 67-174 mm Gn.L. and the length-frequency distribution suggests at least 2 major peaks (Fig. 13). No size-depth dependence was evident throughout the sounding range. The population was largely immature and the onset of ovarian maturity (stage I1) apparently occurs at around 105-110 mm Gn,L. Running ripe females (stage VI) were found in the 120-130 mm Gn.L. group and a spent female in the 125-130 mm group, giving an indication that this is the approximate size of first maturity. The overall sex ratio shows a preponderance of females (ld' : 2.3 !0). Accepting the inadequacy of seasonal coverage, it is notable that the running ripe (stage VI) and recovering spent (stage VII/II) fish were all caught in June. An indication of the feeding strategy was gained from the analysis of 5 stomach contents of fish within the range of 100-120 mm Gn.L. and noted in MARSHAl, It and MERRETr (1977). This indicated that copepods were the dominant prey (in 3 stomachs), while a m p h i p o d s and polychaetes were found in one stomach each (Table 4). No sediment was found in the alimentary tracts. MACROURIDAE
Trach vrincus trachyrincus The collections contain 98 specimens of this species, distributed in soundings of 4821017 m (Appendix I, Fig. 10). In catches off northwest Africa, GOLOVAN (1978) found that the lower limit of distribution of this species varied somewhat with latitude, but had an overall range of 450-1700 m. GEISTDOERFER (1975) gives 400--1500 m as the vertical range for this species in the eastern North Atlantic, including the area in question. Although never abundant among the 'Discovery" samples T. trachyrincus occurred in densities of 1-7 fish/1000 m" from 550-950 m. The overall size range was 7-155 mm HL. T w o peaks are apparent in the length-frequency distribution: one of sexually indeterminate adolescents (30-40 mm H L ) and another broader one of adults (80-110 mm H L - Fig. 14). T h e r e was no evidence of any size-depth dependency from the samples. The sex ratio of the adults examined was 1 ~ : 1.4 9. No ripe females were found, but the indication from the 30 females examined was that onset of ovarian maturity occurred at about 71-75 m m H L , while the smallest recovering spent female showed that spawning had taken place by 106-110 m m HL. T h e diet of T. trachyrincus was investigated mainly from examination of intestinal contents and noted by MARSHALL and MERRE'rr (1977). O f the 16 fish examined (79155 m m H L ) the stomach contents of only 3 were intact, owing to eversion under pressure from the expanding swimbladder. In terms of presence or absence, crustaceans (69%), polychaetes (44%), fish (38%) and squid (31%) were the dominant food organisms (Table 4). Sediment occurred in 44% of the intestines examined which, together with the relative
Ecology of deep-sea bottom-living fishes
213
Ha Iosa ur us ('Ha Iosa uric ht hys ) j o h nso n ia n us
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LENGTH
GROUPStSmm)
FIG. 13.
Halosaurus (Halosaurichthys)johnsonianus.
(Gnathoproctal)
length-frequency
sample,
w i t h s e x e s a n d o v a r i a n m a t u r i t y s t a g e s i n d i c a t e d ( n = 523. " U n s h a d e d a r e a = s e x u a l l y i n d e t e r m i n a t e -
distribution of the total
specimens).
abundance of polychaetes, confirmed the extent of benthic foraging in T. trachyrincus. Thus these results suggest that the marked preference for pelagic food claimed by GEISTDOERFER (1975) and MARSHALL and MERRETT (1977) requires modification to emphasise the mixed nature of the diet indicated by MCLELLAN (1977) and MACPHERSON (1979).
214
N.R. MERRETT and N.B. MARSHALL
Trochytincus
15
trachyrincus
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GROUPSC10mm)
Trachyrincustrachyrincus(Head) length-frequency distribution of the total sample, with sexes indicated (n = 98. Unshaded area as in Fig. 13).
Bathygadus melanobranchus T h o u g h one of the most numerous species in the collections (407 - - Appendix I), B. melanobranchus occurred in only 7 catches. This may be attributable to the narrow depth range it was found to occupy (734-1017 m), yet within this it was caught in densities of up to 21 fish/1000 m" (Fig. 10). GOLOVAN (1978) also found this species to have restricted vertical range in the area (500-1200 m from 09°-3 I°N), which contrasts superficially with that given for the Atlantic as a whole (450-2600 m) by MARSHALl, (1973), but he points out that it is centred in 700-1400 m. The overall size range in the 'Discovery" samples was 7-84 m m HL. As might be expected from its restricted sounding range, there was no suggestion of a size-depth relation. The major peak in the length-frequency distribution (45-63 m m H L - - Fig. 15) is dominated by males (3.36 : 19), accounted for by a disporportionately large number from one haul (7.76 : 1 ?). The sexes are discernible macroscopically by 30 mm H L and the earliest sign of ovarian maturation (stage II) was o b s e r v e d by 51 m m HL, while the smallest spent, fish were observed in the 57-60 mm H E .croup. The spent females were collected in March. The prominence of the mysid, Gnathophausia zoea WILLEMOES-SUHM, 1875, and chaetognaths in the intestines of B. melanobranchus from these samples has been noted previously (MARSHALLand MERRETT, 1977 - - Table 1). The results of the examination of a further 18 fishes have now been added to the 23 already reported (Table 4). The d o m i n a n c e of G. zoea remained unaltered and was present in 51% of the fish examined. Up to 3 G. zoea per stomach were found and all were in the carapace length range 20-23 m m . C o p e p o d s were the second most frequent food item (46%,) found and the mean abundance in stomachs containing them (11) was 5.5. Overall chaetognaths were found to be of rather lesser importance (in 22% of fish examined). The low percentage of intestines
215
Ecology of deep-sea bottom-living fishes
containing sediment coupled with the pelagic nature of the identified prey serves to confirm the pelagic feeding pattern already indicated of bathygadines in general (e.g. MARSHALL and BOURNE, 1964; OKAMURA, 1970; MCLELLAN, 1977) and B. melanobranchus in particular (GEISTDOERFER, 1975; MARSHALL and MERRETI', 1977). There was no evidence to suggest that the composition of the diet altered with the size of predator over the size range examined (22--64 mm HL).
Bathygadus
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GROUPS(3mm)
l q o 15. Bathygadus melanobranchus. (Head) length-frequency distribution of the total sample, with sexes and ovarian maturity stages indicated. (n = 402. Unshaded area as in Fig. 13).
216
N.R.
MERRETTand
N.B.
MARSHAL[.
Coelorinchus coelorinchus coelorinchus
A total of 66 C. c. coelorinchus were collected from 6 stations, although 59 of these were caught at only 2. The maximum density encountered was 10 fish/1000 m" (Fig. 10). All catches were made on the upper slope within the range 279--572 m, somewhat shallower than the 320-1100 m range reported by GOLOVAN (1978) from 18°-31°N. The overall size range 13--69 mm HL, (Appendix I) lacked any indication of a size-depth dependence. The sex ratio from all the samples was close to parity, namely 1 Q : 1.26. In the total collection there was a peak which consisted of juvenile sexually indeterminate specimens, 12-27 mm HL (Fig. 16). A secondary peak of males and immature females (stage I) occurred between 30 and 39 mm HL. Maturing females were found above this size, with 2 recovering spent individuals in the 42-45 mm HL group to indicate that breeding takes place at least by this size. Such evidence as there is on seasonality of gonad maturation suggests that breeding occurs in the early part of the year, from females obtained with maturing ovaries (stage Ill/V) in February-March and only immature (stage I) or recovering spent (stage VII/II) females in July. An insight into the diet of this species resulted from the analysis of intestinal contents of 2 specimens (Table 4). The mixed food found, ostracods and amphipods in both with, in addition, polychaete and fish remains in one each contrasts somewhat with the benthic diet reported by GEISTDOERFER(1975) (see MARSHALL and MERRETT, 1977). The epifaunal nature of the diet has also been reported by MACPHERSON (1979) for this species in the western Mediterranean.
Coelorinchus coelorinchus coelorlnchus
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Ecology of deep-sea bottom-living fishes
217
Coryphaenoides (Lionurus) carapinus This species was widespread, but not abundant, in catches from soundings below 2000 m, with 62 specimens collected from 16 stations (range 1524-4004 m, Appendix I). The maximum density per 1000 m 2 was 1.5 from 3911 m sounding, although a subsidiary peak of 1.1 fish/1000 m" occurred in 2136 m. This may be compared with the depth range of 1200-2800 m for the species in the western North Atlantic, off sourthern New England (39°N), with a maximum density of 2.4 fish/1000 m" in 1768--1960 m (HAEDRICH and POLLONI, 1976). The size range found off northwest Africa was 12-54 mm HL (Appendix I). Many of the specimens were badly damaged in the net, so that little information could be obtained from an overall examination of sex and gonad maturity. A length-frequency analysis indicated an abundance peak at 36-45 mm HL (Fig. 17). These specimens were all captured from soundings of around 4000 m, while those fish of head length <21 mm were caught shallower at soundings <3000 m. This suggestion of a size-depth relationship corroborates the more substantial data of HAEDRICH and POLLONI (1976). Earlier in their life history the pelagic larvae of this genus undergo an ontogenetic migration down from the near-surface waters of the open ocean to the sea floor (MERRETI', 1978). No intestinal examination was attempted because of the high proportion of damaged individuals. HAEDRICH and POLLONI(1976), however examined the diet of a large sample of this species and found that it relied more on truly benthic animals than do other Coryphaenoides and had a preference for amphipods and ophiuroids. Cot yp hoe
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Hymenocephalus italicus Six samples only contained the total 293 specimens collected throughout the surveys from a sounding range of 291--690 m (Appendix I). To the south, in the Gulf of Guinea, IWAMOTO (1970) found H. italicus restricted to soundings shallower than 500 m, although to the north of the present area along the northwest African slope (27°-31°N), GOLOVAN (1978) recorded it from a much broader range (340-1400 m). Maximum densities of 24 and JPO 9:4 - O
2 18
N.R. MERRETrand N.B. MARSHAt,L
26 fish/1000 m ~ occurred in the two 'Discovery' catches containing most fish (Fig. 10). The overall size range was 8-36 mm H L and the length-frequency distribution was unimodal (Fig. 18). The majority of juveniles occurred in the shallower of the two numerous catches (296 m sounding, Fig. 10), but some were also present in deeper tows. So, there is a need for further evidence on any possible size-depth relationship. The sexes could be reliably distinguished by the 16-18 mm H L group and showed a preponderence of females in the total collection (16 : 1.5 9 ) by 18-20 mm H L these females had entered their first oogenic cycle (Fig. 18), yet no female examined had ovaries in advance of the growth phase (Ill/V) of maturation. Most samples were collected in March, but both the July and October collections had representatives in the stage III/V condition. The diet of this species was investigated from the stomach contents of 4 and intestinal contents of 9 individuals in the size range 19-29 mm H L (MARSHALL and MERRETT, 1977 and Table 4). Crustaceans - - copepods, euphausiids and decapods - - were the most abundant organisms in these fishes. The euphausiids present were of particular interest in that Hymenocephalus
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Ecology of deep-sea bottom-living fishes
219
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they were identifiable as Euphausia hanseni Z I M M E R , 1915 and Nemato~:elis megalops ( G . O . SARS, 1883), both mesopelagic diurnal migrators. This preference for pelagic food was noted by MARSHALL and MERRE'IT (1977), confirming the results of a larger sample given by GEISTDOERFER (1975). Both MACPHERSON (1979) and MCLELLAN (1977) presented similar evidence.
Nezumia aequalis As one of the more common macrourids caught, N. aequalis was represented by 381 individuals from the sounding range 307-1524 m, although it was centred in the upper slope region, 307-950 m (Appendix I and Fig. 11). The overall range compares favourably with that given by GOLOVAN (1978) of 320-1620 m from the overlapping area 09°-3 I°N. In the 'Discovery' collections it was present in 15 samples, with a maximum density of 33 fish/1000 m ~ from 550 m sounding (Fig. 19). The total size range was 11-56 mm HL, with a broad peak in length frequency distribution at 20-40 mm H L (Fig. 19). The juvenile elements of the population (<20 mm HL) were not numerous and were present in samples down to 1000 m, indicating a lack of marked size-depth dependence. Among adults, the overall sex ratio was close to parity, 19 : 1.4<3. Females were entering their first oogenic cycle by 22-24 mm HL. While none was found to be in a running ripe condition, the smallest recovering spent fish (stage VII/II) was in the 38--40 mm H L group which indicates at least 2 maturation cycles in the life history. Females in the growth phase of maturation (III/V) were present in samples from February through to October giving little evidence of marked spawning seasonality. MARSHALL and MERRETT (1977) in summarizing their observations on the diet of 44 specimens concluded, in agreement with GEISTDOERFER (1975) and MACPHERSON (1979) that this species depended on a mixed diet of pelagic and benthic organisms. Their data, excluding pooled intestinal contents from 30 specimens, is presented in detail in Table 4 together with the analysis of a further 38 specimens. Copepods (in 90% of the fish examined) and polychaetes (54%) were the most frequently found food items, followed by mysids (21%) and amphipods (15%). The mean number of copepods from stomachs in which they were found was 12.5.
Nezumia sclerorhynchus Whereas this species was present in only four samples, a single catch yielded 85 of the total of 101 specimens (Appendix I). This catch (23 fish/1000 m 2) was made in a sounding of 690 m (Fig. 20), which coincided with the centre of abundance of the species as a whole of 457-731 m given by MARSHALL and IWAMOTO (1973b) and at 500-800 m for Mediterranean representatives by RANNOU (1976). The present data show the sounding range to be 522-1203 m. The overall size range is 16-50 mm H L with 3 peaks in the lengthfrequency distribution at 16-20, 26-36 and around 42-50 mm HL. This distribution in general agrees with an analysis of a larger sample from the Mediterranean by RANNOU (1976). He established a growth curve on the basis of otolith readings, which implies that the peaks in the present data correspond to fish of around 7, 10 and 20+ years old. The few sexually determined specimens suggested that sexual maturity might be attained at 3040 mm H L (Fig. 20), corresponding to 11-20 years old (RANNOU, 1976). The largest specimen caught (50 mm HL) was the only one in a recovering spent condition. Stomach contents could only be found in 12 specimens and analysis of these is given in Table 4. Copepods were found in 6 specimens with a mean number per stomach of 1.3.
221
Ecology of deep-sea bottom-living fishes
Nezumia
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Polychaetes were the next most frequently occurring organism (4 specimens). Small though the sample is, it is evident that N. sclerorhynchus has a mixed diet of benthic and pelagic prey which is in agreement with the extensive survey undertaken by GEISTDOERFER (1975).
Nezumia micronychodon One thundred and sixty three individuals occurred in 7 samples collected between 549-1261 m soundings (Appendix I and Fig. 11). This corresponds with the depth range of the species from the Gulf of Guinea (IWAMOTO, 1970), although GOLOVAN(1978) caught N. micronychodon at 22°N off the northwest African slope in 1620 m. The highest densities in the 'Discovery' collections, however, were in the 2 shallowest catches, in 549 and 572 m (22 and 16 fish/1000 m" respectively) where the majority of juveniles occurred. With a size range of 23--66 mm HL this was the largest Nezumia species encountered. The length-frequency distribution was composed of a large peak of immature unsexed fish (24-32 mm HL) (Fig. 21). Onset of ovarian maturation was not apparent until 44-46 mm
222
N.R. MERRE'VI"and N.B. MARSHALL Nezumia s c l e r o r h y n c h u s
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HL and no fish in the growth phase (Ill/V) were caught. Three of the 4 largest fish caught were recovering spent females. The sex ratio among the sexed fish showed a preponderance of females, 1 c~ : 3.6 9. The diet of N. micronychodon was investigated from the stomach and/or intestinal contents of 30 specimens, which included the 6 reported by MARSHALLand MERREI~ (1977). Overall the species depended largely on polychaetes (90%) and a variety of small crustaceans (Table 4). Sediment, both free and in the form of faecal pellets, was present in 90% of the fishes investigated, to indicate a dependence on infaunal prey. Larger specimens, however, evidently process a greater amount of substrate than do the smaller ones, as they contained relatively more sediment and a higher proportion of polychaetes, usually small tubicolous forms. Specimens of less than 30-40 mm HL fed more on epibenthic organisms. Their diet was largely crustacean and dominated by copepods. The copepods were practically all Aetidopsis carinata BRADFORD, 1969 and were all males, which is unusual because the species is known almost exclusively from females captured in midwater (H. S.J. ROE, personal communication).
Nezumia duodecim The presence of N. duodecim in these collections extends the known range of the species from the Gulf of Guinea northward to 24°N on the northwest African slope (see IWAMOTO,
223
Ecologyof deep-sea bottom-livingfishes
1970). It was the most numerous macrourid collected, although it occurred in only 4 samples (Appendix I). Its abundance was due to a single catch of a density of 103 fish/1000 m 2 from a sounding of 933 m (Fig. 11). Its sounding range of 690-1261 m was somewhat d e e p e r than its occurrence in the Gulf of Guinea (329-960 m, IWAMOTO, 1970). T h e size range sampled was 8-48 mm HL, which embraced a large proportion of immature fish. T h e length-frequency distribution indicates a major peak of immature specimens (20-34 mm H L ) and a secondary one (36-44 mm HL) containing maturing females (Fig. 22). A m o n g adults the sex ratio was found to be 19 : 1.3~. Evidently the onset of ovarian maturity occurs at a size of 30 mm HL, while one female of 44 mm H L was in the recovering spent condition (VII/II). T h e diet of this species has been analysed from the intestinal contents of 60 specimens (Table 4). As in other Nezumia species examined copepods (80%) and polychaetes (62%) were present in the highest proportions in specimens examined. Indeed, the 45 undamaged stomachs investigated contained a mean number of copepods of 69. Considering the diet as a whole, including the small amount of fish remains, it is clear that N. °duodecim, like the majority of macrourines, depends on a mixed diet of benthic and pelagic organisms (see MARSHALL and MERRETF, 1977). 40 ~
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224
N . R . M E R R E I q ' a n d N . B . MARSHALL
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TRACHICHTHYIDAE
Hoplostethus mediterraneus This species has been shown to be widespread along the northwest African slope (MAURIN, 1968). In the 'Discovery' surveys 430 H. mediterraneus were sampled from 11 stations on the upper slope (279-981 m) (Appendix I). Maximum densities (up to 47 fish/1000 m 2) were recorded from 279-522 m soundings (Fig. 10), which coincides approximately with the centre of abundance of 320--457 m for the species given by WOODS and SONODA (1973). Also from the northwest African slope (17°-33°N), GOLOVAN (1978) reports the depth range of this species as 350-950 m. The 'Discovery' samples contained mostly juvenile fish, which accounted for the two peaks in the length-frequency distribution (Fig. 23). No size relation with depth, however, was reflected in the results. Sex was
225
Ecology of deep-sea bottom-living fishes
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226
N.R. MERRETrand N.B. MARSHALL
determinable in specimens of >70 mm SL, but only 10 were found to be sexually mature of which 8 were recovering spent females. First maturity is probably attained, therefore, within the range 70-150 mm SL (Fig. 23). MARSHALL and MERRE'Iq" (1977) summarized the feeding habits of 23 specimens over the size range 51-242 mm SL. Analysis of a further 4 specimens have now been added (Table 4), leaving the conclusions unaltered that crustaceans are the primary prey of this species. Identifiable crustacean remains of natant decapods were present in 37% of fish examined. The occasional remains of echinoids (4%), polychaetes (4%) and fish (7%) indicated that the diet of H. mediterraneus is mixed.
SCORPAENIDAE
Helicolenus dactylopterus The only abundant scorpaenid in the catches, H. dactylopterus occurred in 8 samples with a total of 170 specimens (Appendix I). It occurred over the sounding range 279981 m, although it was more abundant from around 500 m to the top of the range, where the maximum density of 17 fish/1000 m 2 was recorded (Fig. 10). MAURIN (1968) reported this species to be widespread over the upper slope (220--642 m) in the northwest African area and GOLOVAN (1978) corroborates this with catches from the same region (21°-32°N) in soundings of 500-800 m. On the western side of the Atlantic, HAEDRICH,ROWE and POLLONI (1975) mention this species as a dominant organism in the depth zone 141285 m. The overall size range in the 'Discovery' collections was 29-345 mm SL, but the samples were dominated by the smaller, sexually immature specimens, indicated in the multi-peaked length-frequency distribution (Fig. 24). From those fish with distinguishable gonads, it was evident that ovarian maturity is initiated within the range 130-180 mm SL. No females were caught with ovaries in advance of the growth phase of maturation (Ill/V). The stomach contents of 7 specimens and the intestinal contents of 80 were examined and summarized by MARSHALL and MERRETT (1977, Table 1). The results indicate that H. dactylopterus is a highly selective benthic feeder. The ophiuroid, Ophiacantha abyssicola SARS, 1871, was present in 92% of specimens examined (Table 4). Minimal quantities of Crustacea, fish and Pyrosoma were also found. CYNOGLOSSIDAE
Symphurus nigricens This was the only flatfish caught in abundance and that is due to a single large catch of 165 individuals (45 fish/1000 m2). It was collected in only 3 other samples to give a total of 174 (Appendix I). The sounding range was 279--482 m and the abundant catch came from the shallowest sample (Fig. 10). This was at 20*N, which extends the range indicated by MAURIN (1968) by some 10-15 degrees to the south. The size range collected was 29-107 mm SL (Fig. 25). The length-frequency distribution has 3 peaks with evidence of a fourth at the lower size limit sampled. More detailed examination of this species was not undertaken.
227
Ecology of deep-sea bottom-living fishes
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228
N.R. MERRETFand N.B. MARSHALL
Resource partitioning among macrourids A salient feature of the overall collections is the relative dominance of the family Macrouridae in both numbers of species and their abundance. Macrourids comprised 18% of the species (26 spp.) and 48% of individuals (2240 specimens). The number of species is 3 short of the number given by GOLOVAN (1978) in his review of the northwest African slope fauna from the equator to 36°N. Only 21 species are common to both lists, however, indicating that a total of at least 34 macrourid species occurs in the area. While discussing the zoogeography of the macrourid fauna of the eastern Atlantic, IWAMOTO (1970) pointed out the greater diversity of the family to the north of the Gulf of Guinea. He reported only 16 species from the Gulf of Guinea. Ten species are common to both his collection and this one, which supports his view that the macrourid fauna of the Gulf of Guinea is somewhat different from its counterpart in the eastern North Atlantic. T h e depth ranges of the majority of macrourid species (18 out of 26) occurred in soundings shallower than 1600 m (see Appendix I). With such a rich diversity occupying moderately narrow depth limits, there is a high degree of co-occurrence. Indeed, no species was collected consistently in isolation from others, and it was far more usual for several species to be sampled together. The maintenance of such an association of closely related species prompts consideration of niche availability in the community. Evidently greater overlap occurs in the diets of macrourids than is found among shallow water demersal fish (PEARCY and AMBLER, 1974; MACPHERSON, 1979), which may be taken to support the contention of GRASSLE and SANDERS (1973) that in general a lower degree of competitive exclusion exists among deep-sea species. The relative success of representatives of three subfamilies of the Macrouridae in the area serves to reduce likely dietary overlap, with the widely divergent feeding patterns of trachyrhynchines and bathygadines on the one hand and macrourines on the other (MARSHALLand BOURNE, 1964; OKAMURA, 1970; GEISTDOERFER. 1975; MARSHALL and MERRETI', 1977: MCLELLAN. 1977). Confirmation of this is evident from Table 4, where the diets of the macrourids are compared with the other species investigated here. The emphasis on largely pelagic prey by B. melanobranchus contrasts with the feeding pattern of all but one macrourine, H. italicus. Yet the mean size of H. italicus is smaller and its food preferences are somewhat different. In this area at least, T. trachyrincus has a diet apparently intermediate between such pelagic feeders and the majority of macrourines examined, with their more evenly mixed diets of pelagic and benthic prey. (The latter, while largely composed of organisms of strictly unknown origin being representatives of groups with both pelagic and benthic forms, is substantiated here on the basis of the co-occurrence of sediment in the guts of the predators - - Table 4). Trachyrincus trachyrincus is relatively less dependent on benthic food and generally eats larger and more active pelagic prey. It also grows to a larger mean size than do the macrourines examined. The four sympatric species of Nezumia (N. aequalis, N. duodecim, N. micronychodon and N. sclerorhynchus) constituted the largest sample and provide an insight into ways in which competition may be lessened. Adult N. micronychodon, the largest of the local Nezumia and the species with the most gill rakers, processes more ooze for small organisms than do the other 3 species. Smaller specimens, up to about 30-40 mm HL, rely on a broad spectrum of epibenthic crustaceans (Table 4 and see p. 222). But larger specimens change their feeding to more benthic foraging for small tubicoious polychaetes not evidently preyed upon by other local Nezumia species. Despite the similarity in diet of the other
Ecologyof
deep-sea bottom-living
fishes
229
three species, the available data suggest that minor differences in centres of abundance (cf. Fig. 14 - N. aequalis c. 5OO-6CKlm, N. sclerorhynchus c. 700 m and N. duodecim c. 700900 m) may reduce competition. Even with this preliminary evidence, therefore, it is possible to observe indications of niche separation in the trophic relations of macrourids from the northwest African slope. SUMMARY General biological interest in the upwelling region off northwest Africa instigated an examination of the ecology of bottom-living fishes from the upper slope to abyssal depths. The investigation centred around a series of cruises during 1969-1977. Samples were collected from the area 08”-27”N and 14”-3o”W in soundings of 261-6059 m. A variety of gear was used. A total of 92 operations were carried out with an epibenthic sledge of 2.4 m2 mouth area (27), another of nearly 1.5 m2 mouth area (24), a semi-balloon otter trawl of 13.7 m headline length (13), a rectangular midwater trawl of 8 m* mouth area (3) baited pyramidal traps of 1.7 m base length (16) and a Xl-hook longline (9). The total collection comprised 4671 specimens representing at least 148 species from 42 families. The family Macrouridae dominated the catches, being represented by48% of the specimens and 18% of the species. Most species were not abundant. Only 25% were represented by more than 17 specimens. Evidently the towed gears sampled a different spectrum of species from the static baited gears. The catches of the towed gears alone were shown to have a high degree of similarity and so are considered compatible. Although the total catch from the traps and longlines constituted only about 2% of the overall collection, these gears attracted a disproportionately large number of elasmobranchs (77% trap and longline catch) relative to the sample taken by the nets (cl%), to account largely for the sampling dissimilarity. A total of 132 species were collected exclusively by towed gears and 8 species by baited gears alone. Only 8 species were common to the catches of both methods of sampling. The composition of the catches by towed gears was analysed by latitude. The results indicated homogeneity among the samples throughout the area surveyed, to enable comparison of all catches by sounding and by species. A generally close correlation was observed between haul composition of towed gears and sounding sampled. The composition of the catches altered steadily with sounding to depths of around 3000 m, with the lack of obvious fauna1 boundaries as the salient feature. In this respect, these results contrast with trenchant fauna1 bathymetric discontinuities found among slope surveys from both east and west coasts of North America. It is acknowledged that there are possible indications of discontinuities at around 1100 m and 2100 m, however, which do broadly coincide with the limits of the deep species assemblages (1270-1928 m) observed off southern New England by HAEDRICH, Row and POLLONI (1975). Nevertheless, marked zonation may be obscured by a reduced pressure for resource partitioning in the fish fauna off northwest Africa as a result of the high primary productivity, particularly offshore, in the area. Below 3000 m soundings the composition of the fauna was evidently more uniform. An examination of the interrelationships of species distinguished 2 main groups. The majority of species are slope-dwelling forms and constituted the first group. The second group have broader sounding ranges which, with one exception, extended beyond the slope-rise break.
230
N.R. MERRE1"rand N.B. MARSrlAUL
Comparison of this upwelling region with the non-upwelling habitat of the temperate western North Atlantic suggested that the species diversity off northwest Africa was about double that in the latter area. Furthermore, the mean size of the dominant species collected in medium-sized nets in soundings of less than 2000 m was smaller from the upwelling region. Species composition differed also, for the bathygadine macrourids, dominant in the upwelling area, were absent from the temperate North Atlantic. Deeper than 2000 m a marked difference was the apparent absence of a large, wide ranging macrourid or comparable fish in the upwelling zone, counterpart to C. ( N e m a t o n u r u s ) a r m a t u s in the non-upwelling area. This lack of evidence of the 'bigger-deeper' phenom e n o n among fishes is possibly explained by the situation of high productivity throughout the year favouring selection of species of small mean size with less need for nutrient storage. Estimation of the relative density of fishes provided a basis for comparing abundance from different bathymetric levels of the area surveyed. The catches on the upper slope were close to 100 fish/1000 m", but they declined exponentially with depth to about 2 orders of magnitude lower in soundings of around 2000 m. D e e p e r than 2000 m the decrease in relative density was tess marked and was maintained around 0.5/1000 m" at least to 4000 m soundings. Such a decrease in relative abundance is in general agreement with trawling results and submersible observations from the middle Atlantic coast of North America. Although not comparable with the results of the towed gear, catch per unit effort was calculated for the longline operations on the basis of catch per hook hour. Over the 9 operations the mean catch was 0.04 fish per hook hour weighing 0.15 kg per hook hour. It was noted that the estimate of density of fish from off northwest Africa was approximately equal to that calculated from a photographic series taken from a submersible in the temperate western North Atlantic. Estimates from such a series have been shown to be about two to six times greater than those generated by catches of nets roughly similar in size to those used in the present survey. While accepting the tacit danger of comparing estimates of absolute abundance from one area to another when collected by different gear, the present evidence indicated a greater abundance of slope fishes off northwest Africa, probably sustained by greater productivity induced by upweUing. A total of 14 species, represented by 60 or more individuals, were examined in detail. O n e species each of the families Synaphobranchidae, Halosauridae, Trachichthyidae, Scorpaenidae and Cynoglossidae, together with 9 species of the family Macrouridae were considered. All but one of these are slope dwellers and the majority were most abundant in soundings of less than 1000 m. The evidence provided information in varying detail on vertical distribution, population structure, breeding biology and feeding. The relative dominance of the family Macrouridae, both in species richness and diversity, prompted discussion of niche availability in the community and comments on resource partitioning among these co-occurring species.
Acknowledgements - - Many people have helped us, either directly or indirectly,during the preparation of this
paper. We thank them all and apoiogiseto any that we may have inadvertentlyomitted from this acknowledgement. In the course of identifying the samples the following have kindly provided specialist identificationsof particular species: M.E. ANDERSON(Virginia Institute of Marine Science)and A.P. ANDRIYASHEV(Zoological Institute, Leningrad) - - Zoarcidae; J. BLACHE(Musrum National d'Histoire Naturelle, Paris) -- Synapho-
Ecology of deep-sea bottom-living fishes
231
branchidae; L.J.V. CAMPAGNO(Tiburon Center for Environmental Studies) - - Scyliorhinidae and Squalidae, D.M. COHEN (National Marine Hsheries Service, Systematics Laboratory, Washington ) - - Macrouridae; A,W. EBELING (University of California) --Stephanoberycidae; the late C.L. Hunns (Scripps Institution of Oceanography) and B. FERNHOLM(Roskilde Universitetscenter) - - Myxinidae; T. IWAMOTO(California Academy of Sciences) - - Macrouridae; G. K~EF~ (Institut fiir Seefischerei, Hamburg) - - Squalidae; D.F. MARKLE (Huntsman Marine Laboratory, Canada) - - Alepocephalidae; J.G. NIELSEN (Universitets Zoologisk Museum, Copenhagen) - - Ophidiidae and Aphyonidae; M. STEHMANN(Institut for Scefischerei, Hamburg)-Rajidae. We are indebted to J.P. BRIDGER (Ministry of Agriculture, Fisheries and Food, Directorate of Fisheries Research, Lowestoft), S.J. MARINOVICH,(Marinovich Trawl Company Inc.), K.J. SULAK(Virginia Institute of Marine Science) and F. WA'n~NE (National Marine Fisheries Service, Northwest Fisheries Center, Seattle) for contributing valuable information on the behaviour under tow of trawls in general and the OTSB 14 in particular. M.J.R. FASHAM (Institute of Oceanographic Sciences) generously provided considerable help with the statistical treatment of the data and also carded out the computations. A.C. WHEELEa (British Museum (Natural History)) faciliated the X-radiography of squaloid sharks for identification purposes. D. CHAIN (9, North View, London SW19) and Mrs R.A. RUSSELL(IOS) kindly assisted in the preliminary analysis of intestinal contents, while A.L. RICE, H.S.J. ROE and M.H. THURSTON(IOS) afforded specialist identifications of dietry crustaceans. We are grateful to Mrs R.A. RUSSELLfor preparing the illustrations and general assistance, as well as to other colleagues at IOS, together with the Captain and crew of RRS 'Discovery', for their help in the collection of samples. J.R. BADCOCKand P.M. DAVID (IOS) kindly read the manuscript and offered much helpful advice during the course of the study. REFERENCES ALDRED, R.G., M.H. THURSTON,A.L. RICEand D.R. MORLEY(1976) An acoustically monitored opening and closing epibenthic sledge. Deep-Sea Research, 23, 167-174. BAKKEN,E., J. LAHN-JOHANNESSENand J. GJOSAETER(1975) Demersal fish on the continental slope offNorway. Saetrykk av Fiskets Gang, (34), 557-565. BLACHE, J., J. CADENATand A. STAUCH (1970) CI6s de d6termination des poissons de mer signal6s dans I'Atlantique Orientale (entre le 20e parall~le N.et le 15e parall~le S.). Faune Tropicale, 18, 1--479. BRIDGER, J.P. (1978) New deep-water trawling grounds to the west of Britain. Laboratory Leaflets, MAFF Directorate of Fisheries Research, Lowestofi, (41), 40pp. BULHS, H.R., JR. and R. CUMMINS,JR. (1963) Another look at the royal shrimp resource. Proceedings of the Gulf and Caribbean Fisheries Institute, 15th annual session, pp. 9-12. CLARKE, M.R. and N.R. ME~tRETT(1972) The significance of squid, whale and other remains from the stomachs of bottom-living deep-sea fish. Journal of the Marine Biological Association of the United Kingdom, 52, 599-603. COHEN, D.M. and D.L. PAWSON(1977) Observations from the DSRV Alvin on populations of benthic fishes and selected larger invertebrates in and near DWD-106. Baseline Report of Environmental Conditions in Deepwater Dumpsite 106. U.S. Department of Commerce, NOAA, Dumpsite Evaluation Report 77-1, 2, Biological Characteristics. DAY, D.S. and W.G. PEARC¥ (1968) Species associations of benthic fishes on the continental shelf and slope off Oregon. Journal of the Fisheries Research Board, Canada, 25, 2665--2675. Du BUIT, M-H. (1978) Alimentation de quelques poissons t616ost6ens de profondeur dans la zone du seuil de Wyville Thomson. Oceanologica Acta, I, 129-134. FASHAM, M.J.R. (1977) A comparison of nonmetric multidimensional scaling, principal components and reciprocal averaging for the ordination of simulated coenoclines, and coenoplanes. Ecology, 58, 551-561. FERNHOLM, B. (In press) A new species of hagfish of the genus Myxine, with notes on other eastern Atlantic myxinids. Journal ofFish Biology. FORSTER, G.R. (1964) Line-fishing on the continental slope. Journal of the Marine BioiogicalAssociation of the United Kingdom, 44, 277-284. FORSTER, G.R. (1968) Line-fishing on the continental slope: II. Journal of the Marine Biological Association of
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APPENDIX I
Species list and capture stations, including observed size and sounding ranges. MYXINIDAE: 1. Myxine sp. nov. FERNHOLM, in press. 7841#3 (1), 7843#1 (1), 7843#2 (13), 7848#1 (1), 7848# 2 (1). Total: 17 SL range: 260-522 mm. Sounding range: 614-976 m. SCYLIORHINIDAE: 2. Galeuspolli CADENAT, 1959.7816#5 (1), 8930#1 (22), 8931#1 (1). Total: 24 TL range: 248-470 mm. Sounding range: 296-981 m. 3. Apristurusprofundorum (GOODE and BEAN, 1896). 7852#1 (1). Total: 1 TL: 148 mm. Sounding: 989 m. SQUALIDAE: 4. Etmopterus princeps COLLE'Iq', 1904. 7822# 1 (4), 7822#6 (1). Total: 5 TL range: 550--655 mm. Sounding range: 1153-1164 m. 5. Centrophorus granulosus BLOCH and SCHNEIDER, 1801. 7813#1 (2), 7811#1 (1), 7817#1 (3), 7841#4 (1), 7848#3 (1), 7849#1 (6). Total: 14 TL range: 840-1240 mm. Sounding range: 578-985 m. 6. C. squamosus (BONNATERRE, 1788). 7813#1 (6), 7814#1 (16), 7843#3 (1), 7849#1 (1). Total: 24 TL range: 390-1205 mm. Sounding range: 578-798 m. 7. Centroscymnus coelolepis (BOCAGE and CAPELLO, 1864). 7822#2 (1), 7822#5 (1), 7822#6 (1), 8932#2 (1). Total: 4 TL range: 680-850 mm. Sounding range: 1151-2375 m. 8. C. cryptacanthus REGAN, 1906.7813#1 (1), 7822#6 (2), 7848#3 (2). Total: 5 TL range: 660-1035 ram. Sounding range: 601-1164 m. 9. Scymnodon ringens BOCAGE and CAPELLO, 1864. 7843#3 (1). Total: 1 TL: 660 mm. Sounding: 632 m. 10. Deania calcea (LOWE, 1839). 7814#1 (1), 7841#2 (3), 7841#4 (12), 7848#3 (1), 8931#1 (1). Total: 18 TL range: 640-935 mm. Sounding range: 578-985 m. 11. D. profundorum (SMITH and RADCLIFFE, 1912). 7813#1 (1). Total: 1 TL: 750 mm. Sounding: 601 m. RAJIDAE: 12. Raja straeleni POLL, 1951. 7810#1 (3), 7811#1 (1). Total: 4 TL range: 155-290 mm. Sounding range: 307-690 m. 13. R. nidarosiensis STORM, 1881. 7841#2 (1), 8931#1 (1). Total: 2 TL range: 14t30-1820 mm. Sounding range: 918-981 m. 14. Raja sp. 9133#7 (1). Total: 1 TL: 583 mm. Sounding: 2160 m. HYDROLAGIDAE: 15. Hydrolagusmirabilis (COLLETI', 1904). 7839#1 (2), 7845#1 (1), 8003 (1), 8931#1 (2). Total: 6 L t range: 68-360 ram. Sounding range: 734-981 m. 16. H. alberti BIGELOW and SCHROEDER, 1951. 7839#1 (1). 235
236
N.R, MERREVrandN.B. MARSHAIJ
Total: 1 Lt: 540 mm. Sounding: 933 m. RHINOCHIMAERIDAE: 17. Harriotta raleighana GOODE and BEAN, 1895. 7853#1 (1), 9132#5 (1). Total: 2 L ~range: 375-534 mm, Sounding range: 1510-3149 m. XENOCONGRIDAE: 18. Echelus pachyrhynchus (VAILLANT, 18881. 7810# 1 (2), 7816#5 (1), 8020 (34). Total: 37 SL range: 92-515 mm. Sounding range: 279-307 m. 19. Myrophis plumbeus (COPE, 1871). 8020 (1). Total: 1 SL: 221mm. Sounding: 279 m. NETTASTOMATIDAE: 20. Nettastoma melanurum RAFINESQUE, 1810. 7851# 1 ( 1), 8930# 1 (1). Total: 2 SL range: 375 a.40 mm. Sounding range: 510-522 m. 21. Veneficaproboscidea (VAILLANT, 1888). 9132#5 (I). Total: 1 SL: c. 900 mm. Sounding: 3149 m. CONGRIDAE: 22. Coloconger cadenati KANAZAWA, 1961. 7815#2 (2), 7817# 1 (2). Total: 4 SL range: 397-515 mm. Sounding range: 612--649 m. 23. Uroconger vicinus VAILLANT, 1888. 7810#1 (5), 7816#5 (5), 7975 (2), 8014 (l), 8020 (1). Total: 14 SL range: 130-305 mm. Sounding range: 279-814 m 24. Bathycongrus africanus (POLL, 1953). 7845 # 1 (1), 7852 # 1 ( 1). Total: 2 SL range: 190-197 mm. Sounding range: 952-989 m. 25. Ariosoma balearicum (DELAROCHE, 18091. 7811#1 (2). Total: 2 SL range: 329-340 mm. Sounding: 690 m. 26. Bathyuroconger vicinus (VAILLANT, 1888). 8931 # 1 ( 1 ). Total: 1 S L : 2 6 8 m m . Sounding: 981m. 27. Pseudophichthyssplendens (LEA, 1913). 8931 # 1 (3). Total: 3 SL range: 278-345 mm. Sounding: 981 m. SYNAPHOBRANCHIDAE: 28. Synaphobranchus kaupi JOHNSON, 1862. 7822#7 (4), 7838#1 (1), 7839#1 (2), 7840# 1 (20), 7841#3 (2), 7844# I (2), 7845# 1 (10), 7846#1 (2), 7851#1 (8), 7852#1 (8), 7975 (11), 7984 (5), 7991 (3), 7993 (1), 8001 (12), 8003 (3), 8014 (1), 8519#7 (141, 8694#4 (3), 8931#1 (55), 9133#7 (2). Total: 169 SL range: 91--605 mm. Sounding range: 482-2160 m. 29. S. (Histiobranchus) bathybius (GUNTHER, 1877). 9131#1T' (1), 9541# 18~ (1). Total: 2 SL range: 476-1280mm. Depth range~: 3974-4036 m. 30. Haptenchelys texis ROBINS and MARTIN, 1976. 8528# 1 (2), 8682#5 (21, 8933#3 (1), 9133#7 (1). Total: 6 SL range: 183-455 mm. Sounding range: 2160-3153 m. 3 I. llyophis brunneus GILBERT, 1892. 8001 (1), 8519#7 (1). Total: 2 SL range: 432--482 mm. Sounding range: 1017-1458 m. 32. Nettodarus sp. (sensu BLACHE, MAUL and SALDANHA, 1970). 7816#2 (1), 7816#5 (2). Total: 3 SL range: 83-100 mm. Sounding range: 291-296 m. 33. Simenchelysparasitica GOODE and BEAN, 1879.7848#2 (3), 7854#2 (3), 8001 (11 ). Total: 17 SL range: 218-351mm. Sounding range: 976-1458 m. HALOSAURIDAE: 34. Halosaurus (Halosaurus) ovenii JOHNSON, 1863. 7851#1 (11, 7993 (1), 8014 (1), 8931#1 (5).
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Total: 8 Gn. L range: 94--254 mm. Sounding ranga: 522-981 m. 35. H (Halosaurichthys) johnsonianus VAILLANT, 1888. 7811#1 (3), 7839#1 (332), 7840#1 (2), 7845#1 (25), 7984 (11), 8012 (11), 8519#7 (136), 8931#1 (3). Total: 523 Gn. L range: 67-174 mm. Sounding range: 690--1524 m. 36. H. (Halosaurichthys) guentheri GOODE and BEAN, 1896. 7811#1 (1), 7839#1 (49), 7845#1 (4), 8519#7 (4). Total: 58 Gn. L range: 68-165 mm. Sounding range: 690-1017m. 37. Halosauropsis macrochir (GONTHER, 1878). 7090 (2), 7091 (1), 7092 (2), 8682#5 (1), 8932#2 (2), 8933#3 (2), 8933#4 (1), 9132#5 (5), 9133#7 (1). Total: 17 Gn. L range: 114-280 mm. Sounding range: 2160-3311 m. 38. Aldrovandia affinis (GONTHER, 1877). 7846# 1 (3), 7853# 1 (4), 7991 (1). Total: 8 Gn. L range: 62-147 mm. Sounding range: 1502-1510 m. 39. A. phalacra (VAILLANT, 1888). 7853#1 (9), 8694#4 (1). Total. 10 Gn. L range: 78-121mm. Sounding range: 1510-1806 m. 40. A. gracilis GOODE and BEAN, 1896.7822#7 (3), 7853#1 (1). Total: 4 Gn. L range: 60-82 mm. Sounding range: 1203-1510 m. 41. A. rostrata (GUNTHER, 1878). 7112 (1). Total: 1 Gn. L: 96mm. Sounding: 2956 m. LIPOGENYIDAE: 42. Lipogenys gillii GOODE and BEAN, 1895. 7984 (1). Total: 1 Gn. L:38 mm. Sounding: 850 m. NOTACANTHIDAE: 43. Notacanthus bonapartei RlSSO, 1840. 7840#1 (2), 7845#1 (1), 7984 (1), 8519#7 (2), 8931#1 (8), 9134#0 (1). Total: 15 Gn. L range: 36-160 mm. Sounding range: 850-1945 m. 44. N. chemnitzi BLOCH, 1788. 8931#1 (3). Total: 3 Gn L range: 94-117 mm. Sounding: 981 m. 45. Polyacanthonotus (Gnathonotacanthus) africanus (GILCHRIST and VON BONDE, 1924). 7853#1 (5), 8519#7 (1). Total: 6 Gn. L range: 35-71 mm. Sounding range: 1017-1510 m. GONOSTOMATIDAE: 46. Yarella blackfordi GOODE and BEAN, 1896.7811#1 (6). Total: 6 SL range: 109-178 mm. Sounding: 690 m. ALEPOCEPHALIDAE: 47. Alepocephalus agassizii GOODE and BEAN, 1883. 7840# 1 (3). Total: 3 SL range: 225-380 mm. Sounding: 1524 m. 48. A. bairdii GOODE and BEAN, 1879.8931#1 (2). Total: 2 SL range: 299-362 mm. Sounding: 981 m. 49. A. rostratus RlSSO, 1820. 7811#1 (8), 7839#1 (6), 8519#7(2), 8931#1 (18). Total: 34 SL range: 111-420 mm. Sounding range: 690-1017 m. 50. Bellocia koefoedi (PARR, 1951). 8528#1 (2), 8682#5 (1), 8933#4 (1), 9132#5 (3), 9133#7 (1). Total: 8 SL range: 88-395 mm. Sounding range: 2160-3153 m. 51. Conocara salmonea (GILL and TOWNSEND, 1897). 9131#2 (2), 9131#172 (3), 9541#5 (2), 9541#192 (1). Total: 8 SL range: 110--473 mm. Depth/sounding2 range: 3910--4040 m. 52. C. murrayi (KOEFOED, 1927). 8932#2 (1). Total: 1 SL: 107 mm. Sounding: 2375 m.
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N.R. IVIERRETI"and N.B. MARSHALL
53. Rinoctes nasutus KOEFOED, 1927.9131#3 (2), 9131#4 (1), 9131#17' (3), 9541#5 (3). Total: 9 SL range: 121-181 mm. Sounding range: 3875-3995 m. 54. Bathytroctes microlepis GCINTHER, 1878.9133#7 (1). Total: 1 SL: 275 mm. Sounding: 2160 m. 55. Talismania mekistonema SULAK, 1975. 7853# 1 (1). Total: 1 SL: 182 mm. Sounding: 1510 m. 56. T. antillarum GOODE and BEAN, 1895. 7845#1 (4). Total: 4 SL range: 32-42 mm. Sounding: 952 m. 57. Leptoderma macrops VAILLANT, 1886. 7839#1 (6), 7840#1 (1), 7845#1 (5), 7846#1 (1), 8519#7 (6). Total: 19 SL range: 61-113 mm. Sounding range: 933-1524 m. 58. Xenodermichthys copie GILL, 1884. 7811#1 (4), 7838#1 (1), 7839#1 (1), 7844#1 (2), 7845#1 (1), 8003 (1), 8931#1 (6). Total: 16 SL range: 51-165 mm. Sounding range: 482-981 m. Unidentified alepocephalids. 7840#1 (1), 7993 (1). Total: 2 SL range: 23-24 mm. Sounding range: 690-1524 m. CHLOROPHTHALMIDAE: 59. Chlorophthalmus agassizi BONAPARTE, 1840.7810#1 (1), 7816#5 (1), 8020 (3). Total: 5 SL range: 52-162 mm. Sounding range: 279-307 m. 60. Parasudisfraser-brunneri (POLL, 1953). 7816#2 (2), 7816#5 (3). Total: 5 SL range: 141-185 mm. Sounding range: 291-296 m. 61. Bathypterois (Bathypterois) dubius VAILLANT, 1888. 7846#1 (1), 7853# 1 (l), 7991 (3), 8001 (2), 8012 (11), 8519#7 (3), 8931#1 (7). Total: 28 SL range: 69-193 mm. Sounding range: 981-1510 m. 62. B. (Bathycygnus) longipes GUNTHER, 1878. 7092 (1), 8682#5 (1), 8933#4 (1), 9131#1 (1), 9541#5 (1), 9541#6 (1). Total: 6 SL range: 134-166 mm. Sounding range: 2984-4004 m. 63. B. (Benthosaurus) grallator (GOODE and BEAN, 1886). 8932#2 (1). Total: 1 SL: 368mm. Sounding: 2375 m. 64. Ipnops murrayi GI3NTHER, 1878. 9131 # 10 (1). Total: 1 SL: 115 mm. Sounding: 3951m. 65. Bathymicrops regis HJORT and KOEFOED, 1912.8524#6 (2), 9128#/6 (1). Total: 3 SL range: 82-105 mm, Sounding range: 4415-5726 m. 66. Bathytyphlopssewelli (NORMAN, 1939). 7092 (1), 8933#3 (2), 9131#10 (1), 9541#6 (2). Total: 6 SL range: 146--282 mm. Sounding range: 2985-3951 m. SYNODONTIDAE: 67. Bathysaurus ferox GCINTHER, 1878.8932#2 (1), 9133#7 (6). Total: 7 SL range: 450-505 mm. Sounding range: 2160-2375 m. 68. B. mollis GCINTHER, 1878.9131#2 (1). Total: 1 S1:435 mm. Sounding:3926 m. ATELEOPODIDAE: 69. Guentherus altivelis OSORIO, 1917. 7810# 1 (1). Total: 1 SL: 144 mm. Sounding:307 m. LOPHIIDAE: 70. Lophius piscatorius LINNAEUS, 1758.7810# 1 (1). Total: 1 SL: 188 mm. Sounding:307 m.
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CHAUNACIDAE: 71. Chaunaxpictus LOWE, 1846. 7810#1 (1), 7811#1 (1), 7816#5 (5), 8014 (2), 8930#1 (2), 8931#1 (1). Total: 12 SL range: 38-206 mm. Sounding range: 296-981 m. OGCOCEPHALIDAE: 72. Dibranchus atlanticus PETERS, 1875. 7816#5 (14), 7822//7 (3), 7838//1 (2). Total: 19 SL range: 39-103 mm. Sounding range: 296-1203 m. MORIDAE: 73. Mora moro (RlSSO, 1810). 7848//3 (2), 7849#1 (5), 7852//1 (1). Total: 8 SL range: 435--640 mm. Sounding range: 798-989 m. 74. Laemonema laureysi POLL, 1953. 7810//1 (33), 7811//1 (1), 7844//1 (1), 8014 (1), 8930//1 (1). Total: 37 SL range: 78-235 mm. Sounding range: 307--690 m. 75. Brosmiculus imberbis VAILLANT, 1888. 7811//1 (1), 8020 (1). Total: 2 SL range: 72-109 ram. Sounding range: 279--690 m. 76. Physiculus huloti POLL, 1953. 7810//1 (1), 7816//2 (1), 7816//5 (1). Total: 3 SL: 51 mm. Sounding range: 291-307 m. 77. P. dalwigki KAUP, 1858. 8020 (6). Total: 6 SL range: 55-114 mm. Sounding: 279 m. MERLUCCIIDAE: 78. Merluccius atlanticus (LINNAEUS, 1758). 8930# 1 (1). Total: 1 SL: 350mm. Sounding: 510 m. OPHIDIIDAE: 79. Bathyonus sp. 7090 (1), 7811//1 (3), 8933//3 (2), 9131//1 (5), 9131#2 (4), 9131//3 (1), 9131//9 (2), 9131//172 (7), 9541//5 (15), 9541//6 (1), 9541//192 (1). Total: 42 SL range: 40-226 ram. Depth/Sounding 2 range: 690-4040 m. 80. Dicrolene intronigra GOODE and BEAN, 1882. 7811//1 (2), 7822//7 (1), 7839//1 (8), 7840//1 (4), 8001 (2), 8012 (4), 8519//7 (2), 8694//4 (1). Total: 24 SL range: 46-285 mm. Sounding range: 690-1806 m. 81. Monomitopus metriostoma (VAILLANT, 1888). 7811//1 (7), 7839//1 (21), 8012 (1). Total: 29 SL range: 75-140 mm. Sounding range: 690-1261 m. 82. Ophidion rochei MOLLER, 1845. 8020 (2). Total: 2 SL range: 110-150 mm. Sounding: 279 m. 83. Penopus microphthalmus (VAILLANT, 1888). 9132//5 (1). Total: 1 SL: 155 mm. Sounding: 3149 m. 84. Bassozetus sp. 9132//5 (2), 9133//7 (1). Total: 3 SL range: 155-250 ram. Sounding range: 2160-3149 m. 85. Holomycteronus sp. 9132//5 (1). Total: 1 SL: > 275 ram. Sounding: 3149 m. 86. Porogadus sp. 7090 (1), 8528//1 (1), 9132//5 (1), 9133#5 (2), 9540//1 (1). Total: 6 SL range: 72-156 ram. Sounding range: 2007-3153 m. 87. Acanthonus armatus GONTHER, 1878.9133//7 (1). Total: 1 SL: 395 mm. Sounding: 2160 m. APHYONIDAE: 88. Aphyonus gelatinosus GONTHER, 1878.7991 (1). Total: 1 SL: 109 mm. Sounding: 1510m. 89. A. rassi NIELSEN, 1975. 8524#1 (2). Total: 2 SL range: 24--60 mm. Sounding: 4412 m.
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90. Barathronus parfaiti (VAILLANT, 1888). 9131 # 172 (1). Total: 1 SL: 72 mm. Depth 2 range: 3910-3995 m. 91. Nybelinia eriksoni (NYBELIN, 1957). 8682#5 (1). Total: 1 SL: 55 ram. Sounding: 3000 m. ZOARCIDAE: 92. Lycenchelys crassiceps ROULE, 1919.9133#7 (2). Total: 2 SL range: 435-515 mm. Sounding: 2160 m. 93. Melanostigma atlanticum KOEFOED, 1952. 7838#l (6), 7844#1 (1), 7853#1 (1), 8003 (3). Total: 11 SL range: 58-94 mm. Sounding range: 482-1510 m. 94. Pachycaraobesa ZUGMAYER,1911. 9131#1 (1). Total: 1 SL:345 mm. Sounding: 4004 m. MACROURIDAE: 95. Trachyrincus trachyrincus (RISSO, 1810). 7811#1 (11), 7838#1 (23), 7839#1 (10), 7841#2 (1), 7844#1 (1), 7845#1 (5), 7993 (1), 8003 (13), 8014 (7), 8519#7 (3), 8930#1 (8), 8931#1 (15). Total: 98 H L range: 7-155 mm. Sounding range: 482-1017 m. 96. Gadomus arcuatus (GOODE and BEAN, 1886). 7852#1 (1). Total: 1 H L : 4 6 m m . Sounding: 989 m. 97. G. longifilis (GOODE and BEAN, 1886). 7853# 1 (53), 7991 (2). Total: 55 H L range: 2 A, 43 mm. Sounding: 1510 m. 98. Bathygadusfavosus GOODE and BEAN, 1886. 7853#1 (3), 7991 (l). Total: 4 H L range: 29-87 mm. Sounding range: 1510-1512 m. 99. B. melanobranchus VAILLANT, 1888. 7839#1 (40), 7845#1 (76), 7852#1 (4), 7984 (4), 8003 (5), 8519#7 (90), 8931#1 (188). Total: 407 H L range: 7--84 mm. Sounding range: 734-1017 m. 100. Coelorinchus coelorinchus coelorinchus (Rlsso, 1810). 7810#1 (28), 7816#5 (2), 7844#1 (1), 8014 (2), 8020 (31), 8930#1 (2). Total: 66 HL range: 13--69 mm. Sounding range: 279-572 m. 101. C. occa (GOODE and BEAN, 1885). 7822#7 (1), 7840#1 (1), 7853#1 (1), 7991 (1). Total: 4 H L range: 31-112 mm. Sounding range: 1203-1524 m. 102. Coryphaenoides (Coryphaenoides) giintheri (VAILLANT, 1888), 7840#1 (8), 8694#4 (3), 9133#5 (2), 9133#7 (16), 9134#0 (1). Total: 30 HL range: 19-59 mm. Sounding range: 1524-2160 m. 103. C. (C.) zaniophorus (VAILLANT, 1888). 7845-#1 (4), 8003 (2), 8519#7 (1), 8931#1 (13), 8932#2 (1). Total: 21 H L range: 42--88 mm. Sounding range: 734-2375 m. (The 13 specimens of Coryphaenoides from Stn. 8931#1 call into question the validity of C. colon MARSHALL and IWAMOTO (1973a). All bear the characters of a fully scaled snout, an interorbital width <20% HL (15.2-20.7% HL) and a thick and fleshy barbel, which identify them as colon or zaniophorus from the key given by MARSHALL and IWAMOTO (1973a). Beyond that, the two species are distinguished by the length of the snout and horizonal diameter of the orbit relative to the head length. In colon the snout length is approximately equal to the orbit diameter both of which are 26-33% HL. In zaniophorus, on the other hand, the snout length (25% HL in type specimen) is conspicuously less than the horizontal diameter of the orbit (35%). Based on these characters, 8 specimens (60.2-87.6 mm HL) conform to the
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measurements given for colon (snout length 26.2-29.4% HL, orbit diam. 29.133.7% HL). The remaining 5 specimens (41.6-63.4 mm HL), however, agree more closely with the proportions given for zaniophorus (snout length 27.5-30.2% HL, orbit diam. 34.4-36.4% HL). A plot of these values gives a general indication that smaller specimens have the proportions of zaniophorus and the larger ones of colon. Allometric variation within a single species is a more tenable explanation of this situation than the co-occurrence of 2 such closely related species in the same sample, which in addition would be the first record of C. colon in the eastern North Atlantic. We therefore conclude that the likelihood is that C. colon will be found to be conspecific with C. zaniophorus. ) 104. C. (C.) macrocephalus MAUL, 1951. 8932#2 (1). Total: 1 HL: 215 mm. Sounding: 2375 m. 105. C. (Coryphaenoides) sp. A. 7840#1 (2), 9133#5 (2), 9134#0 (1). Total: 5 H L range: 35-106 mm. Sounding range: 1524-2136 m. 106. C. (Nematonurus) armatus (HECTOR, 1875). 8682#5 (1), 8933#3 (1), 9131#4 (1), 9132#5 (1). Total: 4 HL range: 85-137 mm. Sounding range: 2985-3875 m. 107. C. (Chalinura) leptolepis GONTHER, 1877. 8521#1 (1), 9131#17" (1), 9132#5 (1). Total: 3 HL range: 65-124 mm. Depth/Sounding ~ range: 3055-3995 m. 108. C. (C.)profundicola (NYBELIN, 1957). 9131#1 (1), 9131#2 (2), 9541#5 (3), 9541#6 (1). Total: 7 HL range: 66-111 mm. Sounding range: 3926-4004 m. 109. C. (C.) mediterranea (GIGLIOLI, 1893). 7853#1 (1). Total: 1 HL: 76 mm. Sounding: 1510 m. 110. C. (Lionurus) carapinus GOODE and BEAN, 1883. 7090 (2), 7091 (1), 8528#1 (1), 8540#1 (1), 8682#5 (2), 9131#1 (11), 9131#2 (3), 9131#3 (4), 9131#12 (1), 9131#17 z (2), 9132#5 (7), 9133#5 (3), 9541#1 (1), 9541#3 (1), 9541#5 (21), 9541#6 (1). Total: 62 HL range: 12-54 mm. Depth/Sounding ~ range: 1524--4004 m. Unid.Coryphaenoides sp. 9540# 1 (1). Total: 1 HL: 21 mm. Sounding: 2007 m. 111. Hymenocephalus italicus GIGIOLI, 1884. 7816#2 (14), 7816#5 (136), 7844#1 (80), 7851#1 (31), 7993 (13), 8930#1 (19). Total: 293 HL range: 8-36 mm. Sounding range: 291--690 m. 112. Cetonurusglobiceps (VAILLANT, 1888). 7822#7 (1), 7840#1 (1), 7853#1 (2). Total: 4 H L range: 15-105 mm. Sounding range: 1203-1524 m. 113. Trachonurus villosus (GONTHER, 1877). 7822#7 (2). Total: 2 H L range: 46-80 mm. Sounding: 1203 m. 114. Sphagemacrurus hirundo (COLLE'rr, 1896). 7853#1 (2). Total: 2 H L range: 30-32 mm. Sounding: 1510 m. 115. Nezumia aequalis (GONTHER, 1887). 7810#1 (29), 7811#1 (9), 7838#1 (109), 7839#1 (28), 7840#1 (1), 7844#1 (15), 7845#1 (14), 7852#1 (3), 7975 (1), 7993 (5), 8003 (35), 8014 (80), 8519#7 (1), 8930#1 (28), 8931#1 (23). Total: 381 H L range: 11-56 mm. Sounding range: 307-1524 m. 116. N. sclerorhynchus (VALENCIENNES, 1838). 7811#1 (85), 7822#7 (5), 7851#1 (8), 7984 (3). Total: 101 H L range: 16-50 ram. Sounding range: 522-1203 m.
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117. N. micronychodon IWAMOTO, 1970. 7811#1 (1), 7838#1 (73), 7839#1 (14), 7993 (5), 8003 (18), 8012 (1), 8014 (51). Total: 163 H L range: 23--66 mm. Sounding range: 549-1261 m. 118. N. duodecim IWAMOTO, 1970.7811#1 (73), 7839#1 (341), 8012 (12), 8519#7 (1). Total: 427 HL range: 8-48 mm. Sounding range: 690-1261 m. Unid. Nezumia sp. 7811#1 (10), 7838#1 (6), 7840#1 (1), 7993 (8), 8003 (2), 8014 (9), 8020 (12), 8931# 1 (6). Total: 54 H L range: 7-22 mm. Sounding range: 279-1524 m. 119. Ventrifossa occidentalis (GOODE and BEAN, 1885). 7810# t (13), 7816#5 (5), 8020 (5). Total: 23 H L range: 34--64 mm. Sounding range: 279-307 m. Unid. macrourids 7838#1 (8), 8020 (12), 9134#0 (1). Total: 21 H L range: <12-35 mm. Sounding range: 279-1945 m. 120. Lyconus sp. 8931#1 (1). Total: 1 SL:380mm. Sounding: 981m. STEPHANOBERYCIDAE: 121. Malacosarcus sp. 8933#3 (1). Total: 1 S L : 4 0 m m . Sounding:2985 m. TRACHICHTHYIDAE: 122. Hoplostethus mediterraneus CUVIER, 1829. 7838#1 (15), 7844#1 (156), 7845#1 (1), 7851#1 (58), 7975 (8), 7993 (27), 8003 (20), 8014 (7), 8020 (80), 8930#1 (57), 8931#1 (1). Total: 430 SL range: 13-242 mm. Sounding range: 279-981 m. 123. H. cadenati QUERO, 1974. 7811#1 (29), 7816#5 (1), 8003 (2). Total: 32 SL range: 94-169 mm. Sounding range: 296--734 m. ANOPLOGASTERIDAE: 124. Anoplogaster cornuta (VALENCIENNES, 1833). 8519#7 ( 1). Total: 1 SL: 115 mm. Sounding: 1017m. ZEIDAE: 125. Cyttus roseus (LOWE, 1843). 7851#1 (4). Total: 4 SL range: 105-153 mm. Sounding:522 m. 126. C. hololepis GOODE and BEAN, 1895. 7816#2 (1). Total: 1 SL: 53 mm. Sounding: 291m. MACRORHAMPHOSIDAE: 127. Macrorhamphosus scolopax (LINNAEUS, 1758). 7845# 1 (1). Total: 1 S L : 9 9 m m . Sounding:952 m. SCORPAENIDAE: 128. Scorpaena maderensis VALENCIENNES, 1883. 7838#1 (2), 7839#1 (1), 7851#1 (1), 8003 (1), 8014 (3). Total: 8 SL range: 35-385 mm. Sounding range: 522-933 m. 129. S. elongata CADENAT,1945.8020 (3). Total: 3 SL range: 139-169 mm. Sounding: 279 m. 130. S. normani CADENAT,1945.7810#1 (3), 8020 (1). Total: 4 SL range: 84-99 mm. Sounding range: 279-307 m. 131. Helicolenus dactylopterus (DELAROCHE, 1809). 7810#1 (9), 7811#1 (1), 7843#3 (1), 7844#1 (7), 7851#1 (4), 8020 (62), 8930#1 (80), 8931#1 (6). Total: 170 SL range: 29-345 mm. Sounding range: 279-981 m.
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132. Trachyscopaea cristulata echinata (KOEHLER, 1896). 7844#1 (13), 8519#7 (1), 8930#1 (3), 8931#1 (6). Total: 23 SL range: 32-340 mm. Sounding range: 482-1017 m. COq'TUNCULIDAE: 133. Cottunculus thomsoni (GONTHER, 1882). 8001 (2). Total: 2 SL range: 61-267 ram. Sounding: 1458 m. 134. Cottunculoidessubspinosus (JENSEN, 1902). 7840# 1 (2). Total: 2 SL range: 48-52 mm. Sounding: 1524 m. APOGONIDAE: 135. Epigonus denticulatus DIEUZEIDE, 1950. 7844#1 (3), 7993 (2), 8930#1 (15), Total: 20 SL range: 19-114 mm. Sounding range: 482-690 m. 136. E. pandionis (GOODE and BEAN, 1881). 7816#5 (3). Total: 3 SL range: 86-123 mm. Sounding: 296 m. 137. Synagrops microlepis NORMAN, 1935. 7816#2 (1). Total: 1 SL: 116mm. Sounding: 291m. BRAMIDAE: 138. Brama brama (BONNATERRE, 1788). 8020 (2). Total: 2 SL range: 255-330 mm. Sounding: 279 m. PERCOPHIDAE: 139. Bembrops heterurus (MIRANDA-RIBEIRO, 1915). 7816#5 (1). Total: 1 SL: 176 mm. Sounding: 296 m. GOBIIDAE: 140. Gobius angolensis NORMAN, 1935. 8020 (3). Total: 3 SL range: 57-77 ram. Sounding: 279 m. Unid. gobiids 8020 (11). Total: 11 SL range: 14-31 ram. Sounding: 279 m. GEMPYLIDAE: 141. Nesiarchus nasutus JOHNSON, 1862.9133#7 (1). Total: 1 SL: 685 mm. Sounding: 2160 m. BOTHIDAE: 142. Chascanopsetta lugubris ALCOCK, 1894.7816#5 (1). Total: 1 SL: 131mm. Sounding: 296 m. SOLEIDAE: 143. Synaptura lusitanica (CAPELLO, 1868). 7839#1 (1). Total: 1 SL: 124 mm. Sounding: 933 m. 144. Bathysoleapolli (CHABANAUD, 1950). 7844# 1 (6). Total: 6 SL range: 60-153 mm. Sounding: 482 m.145. B. profundicola (VAILLArCr, 1888). 7810#1 (15), 7838#1 (2), 8014 (5), 8020 (25), 8930# 1 (2). Total: 49 SL range: 22-149 mm. Sounding range: 279-572 m. Unid. Bathysolea sp. 8012 (6). Total: 6 SL range: 19-30 mm. Sounding: 1261 m. Unid. juvenile soleids 7816#2 (2), 7838#1 (1). Total: 3 SL: 25 mm. Sounding range: 291-549 m. CYNOGLOSSIDAE: 146. Cynoglossus cadenatiCHABANAUD, 1947. 7811 # 1 (4), 7851# 1 (5). Total: 9 SL range: 53--67 mm. Sounding range: 522-690 m.
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N.R. MERRETrand N.B. MARSHALL
147. Symphurus nigricens RAFINESQUE. 1810. 7816#2 (3), 7816#5 (3), 7844#1 (3), 8020 (165). Total: 174 SL range: 29-107 mm. Sounding range: 279-482 m. 148. S. normani CHABANAUD, 1950.7810#1 (9), Total: 9 SL range: 47-104 mm. Sounding: 307 m. APPENDIX II
Stations and species (numbered according to list in Appendix 1) used in similarity matrices (a) 78 stations and 68 species used in the 2-dimensional ordination of intersample similarities (Fig. 3). Stations 7090# 1. 7091 # 1. 7092# 1,7 112# 1, 7810# I, 78 l 1# 1, 78 t3# 1.7814# 1,7815 #2, 7816#2, 7816#5, 7817# 1. 7822# 1,7822#2, 7822#5, 7822#6, 7822#7, 7838# 1,7839# 1, 7840# 1,7841#2, 7841#3,7841 #4, 7843#1, 7843#2, 7843#3, 7844#1,7845#1, 7846# 1, 7848# 1, 7848#2, 7848#3, 7849#1, 7851# 1,7852# 1,7853# 1,7854#2, 7975. 7984, 7991. 7993, 8001, 8003, 8012, 8014, 8020.8519#7,8521 # I, 8524# l, 8524#6, 8528# 1, 8540# 1, 8682#5, 8694#4, 8930# 1, 8931# 1, 8932#2, 8933#3, 8933#4,9128#6,9131 # 1,9131 #2, 9131#3, 9131#4, 9131#9, 9131#10, 913l#12, 9131#17, 9132#5, 9133#5, 9133#7, 9134#0, 9540#0, 9541 # 1,9541 #3. 9541 #5,9541 #6, 9541# 19. Species 1 , 5 , 6 , 7 , 8 , 10, 15, 18,22.23,25,28,31,33,34,35,36,37,38,43,45,49,50,51, 53, 57, 59, 61, 62, 65, 66, 67, 71,73, 74, 79,80, 86, 95, 97, 98, 99, 100, 102,103, 104, 106, 107, 110, 111,115,116, 117, 118, 119, 122,123, 127, 128, 130. 131,132,133. 134. 135,145,146, 147. (b) 54 stations and 61 species used in the 2-dimensional ordination of intersample similarities (Fig. 4), the l-dimensional ordination of inter-sample similarities (Fig. 5) and the single linkage cluster analysis (Fig. 6b). Stations 7090# 1,7091 # 1,7092#1,7810# 1,7811 # l. 7816#2. 7816#5, 7822#7, 7838# 1, 7839# 1, 7840# 1, 7844# 1, 7845 # 1,7846# l, 7851 # 1, 7852# 1, 7853 # 1,7975, 7984, 7991. 7993, 8001, 8003, 8012, 8014, 8020.8519 # 7,8521 # l, 8528 # 1,8540# 1,8682 #5. 8694 #4, 8930#1,8931#1,8932#2, 8933#3, 8933#4, 9131#1, 9131#2, 9131#3, 9131#4, 9131#9. 9131#10, 9131#12, 9131#17. 9132#5, 9133#5, 9133#7. 9134#0, 9540#0. 9541#1, 9541 #3, 9541#5, 9541#6. Species 7, 10, 15.18, 23, 28, 31,33, 34.35, 36, 37, 38, 43, 45, 49, 50, 51,53, 57, 59, 61,62, 66, 67, 7 l, 73, 74, 79, 80, 86, 95, 97, 98, 99. 100. 102,103,104, 106, 107, 110, 11 I, 115, 116, 117, 118, 119, 122, 123,127, 128, 130, 131,132, 133, 134, 135,145,146. 147. (c) 44 stations and 40 species used in the 2-dimensional ordinations of interspecies similarities (Fig. 7). Stations 7090#1,7091# 1,7092# 1. 7810# 1,78l l # l. 7816#2. 7816#5. 7822#7, 7838# 1, 7839# 1, 7840# 1, 7844# 1, 7845# 1,7846# 1,7851 # 1, 7852# 1,7853# 1,7975, 7984, 7991, 7993, 8001, 8003, 8012, 8014, 8020, 8519#7. 8682#5, 8694#4, 8930# 1,8931 # 1, 8932#2, 8933#3, 8933#4, 9131#1, 9131#2, 913l#3, 9131#17, 9132#5, 9133#5, 9133#7, 9134#0, 9541 #5,9541 #6. Species 18,.23, 28, 34, 35, 36, 37, 38, 43, 49, 51.53, 57, 61, 62, 66, 71,74, 79, 80, 95, 97, 99, 100, 102,103,110, 111. 115,116. 117, 118, 119, 122, 128. 131,132,145,146, 147.
Foolnotes ~Snout to caudal origin ~RMT8--benthopelagic capture