Fisheries Research 51 (2001) 403±412
Estimating the abundance of Patagonian tooth®sh Dissostichus eleginoides using baited cameras: a preliminary study C. Yaua, M.A. Collinsa,*, P.M. Bagleya, I. Eversonb, C.P. Nolanc, I.G. Priedea a
Department of Zoology, University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, UK b British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK c Falkland Islands Government Fisheries Department, Stanley, Falkland Islands, Spain
Abstract The Patagonian tooth®sh Dissostichus eleginoides has been the object of a rapidly expanding longline ®shery in the Southern Ocean. Little is known about the biology of D. eleginoides and traditional methods of estimating stock size using trawling techniques have proved ineffective because the adult ®sh are found in deep waters on the continental slope at depths of 700±2500 m. During September 1997, a preliminary study was undertaken using arrival times at an autonomous baited camera vehicle, the Aberdeen University Deep Ocean Submersible (AUDOS), to estimate the abundance and size of tooth®sh in waters around South Georgia (SG) and the Falkland Islands (FI). These are the ®rst attempts at estimating the abundance of tooth®sh that are independent of catch data from the commercial ®shery. # 2001 Elsevier Science B.V. All rights reserved. Keywords: Tooth®sh; Dissostichus eleginoides; Abundance; Stock size; Baited camera
1. Introduction The Patagonian tooth®sh, Dissostichus eleginoides Smitt, 1898, is a commercially important species caught with longlines in the Southern Ocean. It belongs to the family Nototheniidae, the so-called Antarctic cods. It is distributed around the southern coast of Chile, the Patagonian shelf, and the subAntarctic islands of Kerguelen, South Georgia, and Macquarie at depths of 70±2500 m (DeWitt et al., 1990; Kock et al., 1985; Kock, 1992). The biology of tooth®sh is poorly known, but it is thought to be a relatively long-lived benthopelagic or midwater species. In the Patagonian area spawning of the large pelagic eggs (diameters of 4.3±4.7 mm) is *
Corresponding author. Tel.: 44-1224-272278; fax: 44-1224-272396. E-mail address:
[email protected] (M.A. Collins).
believed to take place on the continental slope at about 500 m depth, with hatching occurring between August and November (Kock, 1993). The juveniles probably remain pelagic for a year until they reach 15±20 cm TL when they become demersal (Kellermann, 1990). Sub-adult ®sh (<50 cm TL) are frequently caught in trawls as an incidental bycatch on the Patagonian shelf (Des Clers et al., 1996), particularly in the squid ®shery for Loligo gahi (pers. obs.), though the adults are con®ned to the deeper waters of the continental slope. Sexual maturity in the females is reached at a size of 90±100 cm TL (9±12 years), whereas males mature at 64±94 cm TL (7±11 years) (DeWitt et al., 1990; Zhivov and Krivoruchko, 1990). Adults may attain total lengths in excess of 220 cm (Falkland Islands Government (FIG), 1998, unpublished data). A commercial longline ®shery for tooth®sh began around South Georgia in 1989, prior to which tooth®sh were caught mainly as a bycatch in trawls. Between
0165-7836/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 5 - 7 8 3 6 ( 0 1 ) 0 0 2 6 4 - 8
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1988 and 1989, Soviet vessels reported catches of 4136 t of tooth®sh, and 8311 t in the subsequent year (CCAMLR, 1998). As a consequence of these high catches, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) established annual total allowable catches of around 3000 t for South Georgia (CCAMLR Subarea 48.3). A more recent licensed longline ®shery has operated in the Falkland Islands Outer Conservation Zone (FOCZ) since 1994, with catches of nearly 3000 t in 1994 and 1995 (Falkland Islands Government, 1997). The longliners use either the Spanish system or an automated system baited with sardines or squid, usually ®shing at depths of 1000±2000 m. In order to manage the tooth®sh stocks effectively, an accurate estimate of abundance is essential. Concern has been expressed about the ability of the tooth®sh stocks to withstand high catch levels. Previous attempts at modelling the population dynamics of tooth®sh have been based on ®shery catch and effort data. However, the very high variability in the catch per unit effort between vessels targeting tooth®sh has meant that conventional assessment methods using depletion models are proving dif®cult to apply (see
Des Clers et al., 1996). Traditional methods of estimating stock size using trawl swept area techniques are fraught with dif®culties owing to rough topography and the depths at which tooth®sh are found. Therefore, alternative methods of assessment must now be considered. Priede and Merrett (1996) demonstrated that the mean ®rst arrival time of scavenging ®sh to bait could be used to obtain an estimate of abundance. This method, however, requires knowledge of both current velocity and ®sh swimming speed, as well as an understanding of the spatial distribution of the species. The Aberdeen University Deep Ocean Submersible (AUDOS) is an autonomous lander that has been used to investigate the biology and behaviour of deep-sea ®sh in the North Paci®c and Atlantic Oceans (Armstrong et al., 1991; Armstrong et al., 1992; Collins et al., 1998). The aim of the present study was to test the feasibility of using the AUDOS to estimate the abundance of tooth®sh around South Georgia and the Falkland Islands independent of ®shery data. Fish tracking was also undertaken in the Falkland Islands in an attempt to determine swimming speeds of tooth®sh necessary for calculating abundance.
Fig. 1. Positions of AUDOS deployments around South Georgia, September 1997.
Table 1 AUDOS station information and results around South Georgia, September 1997 Deployment
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Date set Latitude S Longitude W Depth (m)
7 September 1997 53819.130 41856.660 1039
8 September 1997 53831.240 40820.460 1149
10 September 1997 53846.020 41859.070 1000
11 September 1997 53817.670 42812.030 747
13 September 1997 53835.200 37859.240 1000
14 September 1997 53840.560 38859.620 1000 (failed)
16 September 1997 54812.620 36827.000 269 (no visibility)
17 September 1997 53845.080 35859.800 1100
18 September 1997 54814.940 35815.830 775
19 September 1997 54830.940 35806.120 1487
20 September 1997 54859.900 34806.940 1525 (failed)
21 September 1997 55825.380 34855.270 625
22 September 1997 55809.110 36821.200 1143
23 September 1997 55802.620 36859.650 1275
D. eleginoides Number photographed First arrival time (min)
1 614
2 87
3 165
8 31
1 225
± ±
± ±
4 22
0 ±
1 438
± ±
6 196
4 164
5 114
18 0 0
4 1 0
43 1 0
27 0 4
± ± ±
± ± ±
44 0 0
33 0 3
28 1 0
± ± ±
24 4 0
37 1 0
20 3 0
P. formosa (maximum per frame) 3 P. santolla (maximum per frame) 0 P. spinosissima (maximum per frame) 0
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2. Materials and methods The AUDOS was deployed on 18 occasions around South Georgia in September 1997 from the F.V. ``Argos Galicia'', a commercial stern trawler chartered for a scienti®c ground®sh survey of the area (Fig. 1, Table 1). These deployments were located at random around the 1000 m isobath. A further nine deployments were made in the FOCZ in known tooth®sh longlining grounds from the Falklands Fishery Protection Vessel M.V. ``Cordella'' in October 1997 (Fig. 2, Table 2). 2.1. The AUDOS For the South Georgia work a simpli®ed version of the AUDOS (see Bagley and Priede, 1997) was used.
The basic AUDOS consisted of an aluminium (Grade HE 30) frame onto which were mounted a deep-sea camera (Ocean Instrumentation), an acoustic doppler current metre (Sensortec), and twin acoustic releases (Mors). Buoyancy was provided by glass spheres (Benthos Inc. 17) attached to a mooring line. A dhan buoy incorporating a VHF radio (Novatech), satellite beacon (SIS) and a large pink ¯ag were attached to the end of the mooring to aid location and recovery. Ballast, in the form of scrap chain, was used to anchor the AUDOS. The ballast was attached to an aluminium (non-marine grade) cross graduated at 10 cm intervals, which provided calibration for the photographs. Telltale ribbons attached to the ends of the cross also provided a qualitative indicator of current speeds in the photographs. For ®sh tracking deployments in
Fig. 2. Positions of AUDOS deployments in the FOCZ, October 1997.
Deployment
1
2
3
4
5
6
7
8
9
Date set Latitude S Longitude W Depth (m)
10 October 1997 54826.260 55829.760 900
10 October 1997 54825.910 55811.630 1148
10 October 1997 54841.650 55819.290 1442
11 October 1997 54835.350 55810.140 1116
11 October 1997 54820.070 55811.590 1735
12 October 1997 54823.800 55830.130 1179
13 October 1997 54825.770 55818.960 1212
14 October 1997 54825.940 55824.560 1048
17 October 1997 48836.300 57809.990 1047
D. eleginoides Number photographed First arrival times (min)
1 23
13 38
19 58
9 132
11 18
8 84
15 38
6 106
13 37
P. spinosissima (maximum per frame) P. formosa(maximum per frame)
0 0
2 0
0 5
0 1
0 1
0 2
0 1
0 0
0 0
C. Yau et al. / Fisheries Research 51 (2001) 403±412
Table 2 AUDOS station information and results from Falkland Islands Outer Conservation Zone, October 1997
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408
C. Yau et al. / Fisheries Research 51 (2001) 403±412
Falklands waters, three arms fold down from the main frame to support the hydrophones used for triangulating ®sh position. Code-activated transponders (CATs) (see Bagley, 1992) were inserted into the bait so that ®sh swallowing the bait could be located every minute, and the direction and speed of the ®sh could then be determined. The bait used consisted of squid (Illex argentinus) and either an ice®sh or myctophids; these were tied onto the graduated cross positioned 2.5 m below the camera.
The camera was loaded with Ektachrome 200 ASA colour reversal ®lm and was set on a 1 min time lapse. Small strips of ®lm were developed on board ship using developing kits (Chrome 3-Bath); the remainder of the ®lm was developed in UK (Kenton Film Laboratories). Following processing, the ®lm was viewed on a micro®lm viewer. The ®eld of view obtained from the photographs covered a mean area of 4.3 m2. Fauna were identi®ed using relevant texts (Norman, 1937; Peden and Anderson, 1978; Macpherson, 1988; Gon and Heemstra, 1990). Total lengths (TLs) of ®sh were measured when they were level with the graduated cross or when they were on the sea¯oor. 2.3. Abundance estimations The model developed by Priede and Merrett (1996) for estimating ®sh abundance from arrival times at a baited camera assumes that the ®sh are evenly distributed across the ground and are not gregarious. The distance from which the ®rst ®sh was attracted to the bait (r) is then estimated from the current speed and the ®sh swimming speed tarr
1=Vw
1=Vf
(1)
where r is the distance of the fish from the bait (m), tarr the first arrival time at bait (s), Vw the current velocity (m sÿ1) and Vf the fish swimming velocity (m sÿ1). The area occupied by an individual ®sh is assumed to be a hexagon (of radius equal to r), so that Aindiv 12
3 r 2 30:5 2:589r 2
n
(2)
1 Aindiv
(3)
Substituting Eqs. (1) and (2) into Eq. (3): n
1=Vf
1=Vw 2 2 2:598tarr
(4)
Hence n
2.2. Photographic analysis
r
The abundance of fish (n mÿ2) is then
0:3849
1=Vf
1=Vw 2 2 tarr
(5)
The results will be sensitive to variations in current speed and swimming speed. It is also important to make repeated deployments in order to obtain an average first time of arrival of animals in any location.
3. Results Numbers and ®rst arrival times of tooth®sh and several species of crabs from South Georgia (SG) and the Falkland Islands (FI) are given in Tables 1 and 2. Some problems with camera failure were encountered during the South Georgia cruise, so that only 13 of these deployments were successful. The shallowest deployment made at South Georgia was at 269 m within the entrance to Cumberland Bay and did not form part of the survey; moreover, the extremely high suspended sediment load in the water column made analysis of this particular ®lm impossible. Current and temperature measurements were obtained from SG1 to SG5. However, the current metre was damaged during SG6, which meant ensuing current data were unusable, although the current metre still recorded temperature every minute for the remainder of the cruise. Current data obtained while the current metre was functional had a mean velocity of 0.089 m sÿ1 in the Shag Rocks area of South Georgia. Much higher current velocities were evident around the Falkland Islands. In addition to tooth®sh, the principal species attracted to the bait were stone crabs of the family Lithodidae, hag®sh (Myxine spp. Ð con®ned to the FI deployments only), grenadiers (Macrourus spp.), blue hake (Antimora rostrata), liparid ®sh (Careproctus spp.), and the decapod prawn Thymops birsteini. Only
C. Yau et al. / Fisheries Research 51 (2001) 403±412
the stone crabs, grenadiers and blue hake were photographed actually taking the bait. Full details of the scavenging fauna around the Falkland Islands are given in Collins et al. (1999). 3.1. Toothfish Tooth®sh were photographed during all of the successful deployments except at SG9 at 775 m depth
409
(Tables 1 and 2). A maximum of 19 individuals was observed during the course of any one deployment in the Falklands, but only a maximum of six tooth®sh was counted from any South Georgia deployment. Individual tooth®sh could sometimes be identi®ed by patterns of scars and spots on their dorsal surface. The maximum number of tooth®sh together in any frame was two. The mean ®rst arrival time of tooth®sh was 237 min in South Georgia, whereas in the FOCZ this
Fig. 3. Length±frequency distributions of toothfish, D. eleginoides, measured from: (a) trawl samples from the groundfish survey at South Georgia; (b) AUDOS photographs from South Georgia; (c) AUDOS photographs from the Falkland Islands.
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C. Yau et al. / Fisheries Research 51 (2001) 403±412
was briefer at 59 min. Arrival times of subsequent individuals were well separated, suggesting that tooth®sh were probably solitary in habit and did not form aggregations. Tooth®sh were de®nitely attracted to the bait but did not appear to show further interest after arrival. Some individuals were observed circling around and swimming under the cross, but were never seen to investigate closely or attempt to take the bait. Consequently, tracking of tooth®sh was not accomplished and no swimming speeds could be determined. When tooth®sh did appear, they frequently remained in the frame for only 1 min. Less commonly an individual remained for more than one frame, up to a maximum duration of 12 min (FI3). Individual tooth®sh did not appear to make repeated visits to the bait. Tooth®sh caught by trawl during the ground®sh survey had a mean TL of 537 mm
S:D: 132 mm and ranged in size from 260±1100 mm (Fig. 3a). Of the 39 tooth®sh encountered at SG with AUDOS, the TL of only 19 individuals could be measured. A mean TL of 648 mm was obtained
S:D: 135 mm, range 464±935 mm (Fig. 3b). Mean TLs of tooth®sh from SG compared between trawl samples and AUDOS photographs were highly signi®cantly different (at P < 0:001). A total of 93 tooth®sh was seen in the FI deployments but the total lengths of only 55 ®sh could be measured, as the whole ®sh had to be within the photograph. The mean TL of ®sh observed in the FOCZ was 781 mm
S:D: 123 mm, range 520± 1174 mm (Fig. 3c). Mean TL of tooth®sh were signi®cantly different between SG and FI AUDOS specimens (at P < 0:001). 3.2. Lithodid crabs The most abundant and frequently encountered species in the SG deployments were the lithodid or stone crabs. Three species could be distinguished from the photographs, these have been putatively identi®ed in the absence of reference specimens as Paralomis formosa,ParalomisspinosissimaandParalithodessantolla (based on descriptions from Macpherson, 1988). The most common species was P. formosa which occurred in every successful South Georgia deployment, with a maximum number per frame of 44 individuals (SG8). Arrival times of this species were at times rapid (5±
190 min, mean ®rst arrival time 44 min) compared with P. santolla (mean ®rst arrival of 132 min) and P. spinosissima (mean ®rst arrival of 359 min). 4. Discussion The mean ®rst arrival times of tooth®sh to the bait at 59 and 237 min for FI and SG deployments, respectively, imply low abundances, particularly around South Georgia. It is likely that tooth®sh had arrived earlier but were not photographed either because of the 1 min interval between frames, or because the ®sh were outside of the ®eld of view. In many of the frames with tooth®sh present, only part of the individual was visible with usually just the head or the tail in view. The absence of current meter and ®sh swimming speed data, coupled with doubts about the ®rst arrival times of the tooth®sh, mean that we are not able to make a realistic estimation of abundance. However, using data obtained from South Georgia, where there was a mean ®rst arrival time of 237 min, an approximated swimming speed of 0.324 m sÿ1 (0.5 bodylength sÿ1), and current speed of 0.089 m sÿ1; substituting these values into Eq. (5) gives us 0.4 tooth®sh kmÿ2. Similarly, applying data from the Falkland Islands, with a mean ®rst arrival time of 59 min, a swimming speed of 0.39 m sÿ1 (0.5 body-length sÿ1) and an estimated current speed of 0.25 m sÿ1, results in an estimate of 1.32 tooth®sh kmÿ2. These are probably unrealistically low values of abundance and clearly require further revision, especially given the amount of commercial catches of tooth®sh achieved by longliners in both areas. Since abundance is proportional to the reciprocal of the square of arrival time, a doubling of the arrival time produces a fourfold decline in the abundance estimate. From the photographic evidence, tooth®sh stayed only brie¯y at the bait and it is possible that earlier arrivals had been missed. The difference in arrival times between the two areas may re¯ect the fact that we were operating on known ®shing grounds in the FOCZ. The lack of interest shown by the tooth®sh in the bait after arrival is curious. It contrasts with the behaviour of other scavenging ®shes, such as the grenadiers Coryphaenoides armatus and C. yaquinae in the North Atlantic and North Paci®c (Priede and Smith, 1986; Priede et al., 1990; Armstrong et al.,
C. Yau et al. / Fisheries Research 51 (2001) 403±412
1992; Smith et al., 1992; Priede et al., 1994a,b; Collins et al., 1998). The squid bait used was the short-®n squid, I. argentinus, which is the same bait usually employed by longliners in the commercial ®shery. Closer interest in the bait was shown by the grenadiers and A. rostrata which were observed taking the squid. There must have been a detectable difference (to a tooth®sh) between pieces of squid on longline hooks and the con®guration of bait on a cross; or perhaps some trigger such as motion of the bait is required in order to elicit a response from tooth®sh. It is also likely that the ¯ash used for taking the photographs discouraged tooth®sh from taking the bait. The mean size of tooth®sh (648 mm TL), as measured from the South Georgia photographs, was larger than that obtained from trawl samples during the ground®sh survey (537 mm mean TL). This was perhaps expected since the trawls were carried out at shallower depths (<300 m) where juveniles were more abundant. In order to estimate the abundance of P. formosa around South Georgia, the mean current velocity of 0.089 m sÿ1 obtained from Shag Rocks was used to represent all of South Georgia. A mean walking speed of 0.016 m sÿ1 was calculated by measuring the maximum distance traversed by individual crabs
n 10 in consecutive frames of the photographs averaged over several deployments. Applying these values into Eq. (5) results in a rough approximation of 300 crabs kmÿ2. The results show that P. formosa is a common scavenging species around South Georgia that probably occurs in higher numbers than previous exploratory trawl surveys had suggested (e.g. Basson and Hoggarth, 1994). Marked ¯uctuations in crab numbers observed in the course of some deployments implied a clumped distribution of P. formosa, though further investigations would be required to clarify this. There were insuf®cient data available on the walking speeds of P. spinosissima and P. santolla to estimate their abundance, but the longer ®rst arrival times for these species suggested a much lower density than for P. formosa. P. spinosissima has been the focus of attention as a potential species for commercial exploitation around South Georgia (Basson and Hoggarth, 1994; LoÂpez-AbellaÂn and BalguerõÂas, 1994) and exploratory ®shing resulted in a catch of 299 t during 1992±1993 (CCAMLR, 1998). An important ®shery already exists along the southern coast of Chile for the larger P. santolla (Campodonico, 1983).
411
For future work, a video camera capable of operating at low light levels would be preferred. This would avoid the use of an intense ¯ash and may overcome ¯ash-induced bait shyness by the tooth®sh. The quality of the video camera images may be poorer, but as a consequence of the experience gained from the present study it would be possible to distinguish tooth®sh from other scavenging ®sh species. Furthermore, short-term deployments of 2±3 h would be feasible, so that many deployments could be made in a short period. Ideally, future work should be undertaken outside of the commercial season to avoid the in¯uence of the large amount of bait deployed from longliners operating concurrently in the survey area. It would still be necessary to track tooth®sh in order to determine swimming speeds. If other factors such as the position of the bait are important, these can be modi®ed between deployments as video images could be reviewed immediately after the vehicle is recovered. 5. Conclusion It is not certain whether the difference in the calculated tooth®sh abundance between Falklands waters and South Georgia is signi®cant. A higher density of tooth®sh was calculated in the FOCZ, even though commercial longliners were ®shing close by at the same time. Clearly, further work is required to determine if this difference is a real feature, perhaps resulting from the longer period of commercial longlining that has occurred around South Georgia. Heavy exploitation around South Georgia may also be re¯ected by a low abundance estimate owing to reduced motivation by tooth®sh to scavenge if plentiful food (in the form of longlining bait) is available. The present study has shown that it is feasible to attempt an estimate of tooth®sh abundance using a baited camera system such as AUDOS, however, the paucity of information on the behaviour of tooth®sh meant that this preliminary study only had limited success. A planned cruise to South Georgia in 2000 that includes a follow-up AUDOS survey should incorporate the necessary modi®cations and allow us to revise the estimate of Patagonian tooth®sh abundance.
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Acknowledgements Dr. Phil Bagley and Steve Addison (University of Aberdeen) provided technical expertise on the AUDOS. Thanks to the crews of the F.V. ``Argos Galicia'' and the M.V. ``Cordella'' for their assistance in the handling of AUDOS. Dr. Nigel Merrett and Martin White assisted in species identi®cations. Crag Jones (Marine Resources Assessment Group, Imperial College, London), Dave Currie (Scantron), Adam Cockwell (Argos Ltd.), and Joost Pompert (FIG Fisheries Department) provided logistic support. This work was funded by Falkland Islands Government, the Government of South Georgia, NERC Grant GR3/ 10162, and EU MAST-3 CT950010 project ALIPOR. References Armstrong, J.D., Priede, I.G., Smith, K.L., 1991. Temporal change in foraging behaviour of the fish Coryphaenoides (Nematonurus) yaquinae in the central North Pacific. Mar. Ecol. Prog. Ser. 76, 195±199. Armstrong, J.D., Bagley, P.M., Priede, I.G., 1992. Photographic and acoustic tracking observations of the behaviour of the grenadier Coryphaenoides (Nematonurus) armatus, the eel Synaphobranchus bathybius, and other abyssal demersal fish in the North Atlantic Ocean. Mar. Biol. 112, 535±544. Bagley, P.M., 1992. A code-activated transponder for the individual identification and tracking of deep-sea fish. In: Priede, I.G., Swift, S.W. (Eds.), Wildlife Telemetry. Ellis Horwood, Chichester, pp. 111±119. Bagley, P.M., Priede, I.G., 1997. An autonomous free-fall acoustic tracking system for investigation of fish behaviour at abyssal depths. Aquat. Living Resour. 10, 67±74. Basson, M., Hoggarth, D.D., 1994. Management and assessment options for the crab fishery around South Georgia. CCAMLR Sci. 1, 193±202. Campodonico, G.I., 1983. Research on the biology and fishery of the Chilean southern king crab and the false king crab prospects and problems. Can. Transl. Fish. Aquat. Sci. 4970, 30. CCAMLR, 1998. CCAMLR Statistical Bulletin, Vol. 10. Fisheries data 1988±1997, SB/1998/10. Collins, M.A., Priede, I.G., Addison, S., Smith, A., Bagley, P.M., 1998. Acoustic tracking of the dispersal of organic matter by scavenging fishes in the deep-sea. Hydrobiologia 371±372, 181±186. Collins, M.A., Yau, C., Nolan, C.P., Bagley, P.M., Priede, I.G., 1999. Behavioural observations on the scavenging fauna of the Patagonian slope. J. Mar. Biol. Ass. UK, 79, 963±970. Des Clers, S., Nolan, C.P., Baranowski, R., Pompert, J., 1996. Preliminary stock assessment of the Patagonian toothfish longline fishery around the Falkland Islands. J. Fish Biol. 49 (Suppl. A), 145±156.
DeWitt, H., Heemstra, P.C., Gon, O., 1990. Nototheniidae. In: Gon, O., Heemstra, P.C. (Eds.), Fishes of the Southern Ocean. J.L.B. Smith Institute of Ichthyology, Grahamstown, pp. 279±331. Falkland Islands Government, 1997. Fisheries Statistics, Vol. 1. Fisheries Department, 75 pp. Gon, O., Heemstra, P.C., 1990. Fishes of the Southern Ocean. J.L.B. Smith Institute of Ichthyology, Grahamstown, 462 pp. Kellermann, A., 1990. Catalogue of early life stages of Antarctic notothenioid fishes. Berichte Polarforschung 67, 45±136. Kock, K.-H., 1992. Antarctic Fish and Fisheries. Cambridge University Press, Cambridge, 359 pp. Kock, K.-H., 1993. The early life history and the onset of scale formation in the Patagonian toothfish, Dissostichus eleginoides Smitt, 1898. Document WG-FSA-93/14, CCAMLR, Hobart, Australia, 11 pp. Kock, K.-H., Duhamel, G., Hureau, J.-C., 1985. Biology and Status of Exploited Antarctic Fish Stocks: A Review. Biological Investigations of Antarctic Systems and Stocks (BIOMASS) Scientific Series 6. SCAR and SCOR, Scott Polar Research Institute, Cambridge, UK. LoÂpez-AbellaÂn, L.J., BalguerõÂas, E., 1994. On the presence of Paralomis spinosissima and Paralomis formosa in catches taken during the Spanish Survey Antartida 8611. CCAMLR Sci. 1, 165±173. Macpherson, E., 1988. Revision of the family Lithodidae Samouelle, 1819 (Crustacea, Decapoda, Anomura) in the Atlantic Ocean. MonografõÂas de ZoologõÂa Marina 2, 9±153. Norman, J.R., 1937. Coast fishes. II. The Patagonian region. Discovery Rep. 16, 1±150. Peden, A.E., Anderson, M.E., 1978. A systematic review of the fish genus Lycodapus (Zoarcidae) with descriptions of two new species. Can. J. Zool. 56, 1925±1961. Priede, I.G., Merrett, N.R., 1996. Estimation of abundance of abyssal demersal fishes; a comparison of data from trawls and baited cameras. J. Fish Biol. 49 (Suppl. A), 207±216. Priede, I.G., Smith, K.L., 1986. Behaviour of the abyssal grenadier Coryphaenoides yaquinae, monitored using ingestible acoustic transmitters in the Pacific Ocean. J. Fish Biol. 29, 199±206. Priede, I.G., Smith, K.L., Armstrong, J.D., 1990. Foraging behaviour of abyssal grenadier fish: inferences from acoustic tagging and tracking in the North Pacific Ocean. Deep-Sea Res. 37 (1), 81±101. Priede, I.G., Bagley, P.M., Smith, A., Creasey, S., Merrett, N.R., 1994a. Scavenging deep demersal fishes of the Porcupine Seabight, north-east Atlantic: observations by baited camera, trap and trawl. J. Mar. Biol. Assoc. UK 74, 481±498. Priede, I.G., Bagley, P.M., Smith, K.L., 1994b. Seasonal change in activity of abyssal demersal scavenging grenadiers Coryphaenoides (Nematonurus) armatus in the eastern Pacific Ocean. Limnol. Oceanogr. 39 (2), 279±285. Smith, K.L., Kaufmann, R.S., Edelman, J.L., Baldwin, R.J., 1992. Abyssopelagic fauna in the central North Pacific: comparison of acoustic detection and trawl and baited trap collections to 5800 m. Deep-Sea Res. 39 (3±4), 659±685. Zhivov, V.V., Krivoruchko, V.M., 1990. On the biology of the Patagonian toothfish, Dissostichus eleginoides, of the Antarctic Part of the Atlantic. J. Ichthyol. 30 (7), 142±146.