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Summer distribution and ecological role of seabirds and marine mammals in the Norwegian and Greenland seas (June 1988)
Journal of Marine Systems, 3 (1992) 73-89
73
Elsevier Science Publishers B.V., Amsterdam
Summer distribution and ecological role of seabirds and marine mammals in the Norwegian and Greenland seas (June 1988) Claude R. Joiris
Laboratory for Ecotoxieology, Free University of Brussels (VUB), Pleinlaan, 2 B-1050 Brussels, Belgium (Received September 20, 1990; revised version accepted April 9, 1991)
ABSTRACT Joiris, C.R., 1992. Summer distribution and ecological role of seabirds and marine mammals in the Norwegian and Greenland seas. J. Mar. Syst., 3: 73-89. During the ARK V/2 expedition of RV Polarstern in the Norwegian and Greenland seas in June 1988, 380 half hour counts for marine vertebrates (seabirds, pinnipeds and cetaceans) were carried out. Results are presented as total numbers encountered and then converted into density and food intake.Mean food intake was 2.2 kg fresh weight per km2 per day for seabirds, with a higher value in Atlantic water (2.5) lower values in polar water and the pack ice (1.7 and 1.9), and an intermediate value at the ice edge. The main species were the alcids (1.5, primarily Little Auk, Alle alle and Briinnich's Guillemot, Uria Iomvia), the Fulmar, Fulmarus glacialis (0.5), and the Kittiwake, Rissa tridactyla (0.2). The ecological role of cetaceans was clearly lower, with a mean value of 0.2 and a maximum of 0.7 in Atlantic water (rough evaluation, due to the low number of contacts). The food intake by pinnipeds was 0.55 kg/km 2 day at the ice edge and 0.4 in the pack ice; they were mainly harp, Phoca groenlandica and hooded seals, Cystophora cristata, in one main concentration each and ringed seals, Phoca hispida, scattered on the pack. Data for July 1988 show a great similarity with these results, except for a lower density of alcids, which probably reflects that Little Auk, Briinnich's Guillemot and Common Guillemot, Uria aalge already had started to leave the region.
Introduction O u r k n o w l e d g e o f s e a b i r d s is g e n e r a l l y g o o d as far as t h e i r b r e e d i n g colonies a r e c o n c e r n e d (e.g. Croxall et al., 1984), b u t less is k n o w n a b o u t t h e i r d i s t r i b u t i o n at sea. Such d a t a , however, p r o v i d e i m p o r t a n t i n f o r m a t i o n , not only a b o u t t h e ecology o f seabirds, b u t also a b o u t t h e ecological s t r u c t u r e a n d t h e f u n c t i o n i n g o f the e c o s y s t e m s to which they b e l o n g (Joiris, 1978; Joiris et al., 1982). T h e b r e e d i n g p o p u l a t i o n s of the alcids a r o u n d the N o r w e g i a n a n d G r e e n l a n d seas a r e well studied a n d c o n c e r n (in millions o f pairs): 0.53 R a z o r bills, A k a torda, m a i n l y in I c e l a n d ; 2.5 C o m m o n G u i l l e m o t s , Uria aalge (of which 1.6 in I c e l a n d a n d 0.75 in B e a r Island); 4.9 Briinnich's; G u i l l e mots, U. Iomvia (2 in I c e l a n d , 1 in S p i t s b e r g e n , 1 in N o v a y a Z e m l y a a n d 0.75 in B e a r Island); 1.6
Little A u k s , Alle alle (1 in Spitsbergen); 0.12 Black G u i l l e m o t s , Cepphus grille a n d 4.3 Puffins, Fratercula arctica (3 in I c e l a n d a n d 1.3 in N o r way; N e t t l e s h i p a n d B i r k h e a d , 1985). P i n n i p e d s a r e m a i n l y r e p r e s e n t e d by the r i n g e d seal, Phoca hispida hispida (0.1 to 3 o b s e r v e d p e r k m 2 all zones o f t h e i r d i s t r i b u t i o n c o n s i d e r e d t o g e t h e r ; F r o s t a n d Lowry in R i d g w a y a n d H a r r i son, 1981), h o o d e d seal, Cystophora cristata (230,000 o b s e r v e d m o u l t i n g in t h e D e n m a r k Strait: R e e v e s a n d Ling in R i d g w a y a n d H a r r i s o n , 1981), b e a r d e d seal, Erignathus barbatus (300,000 for t h e w h o l e N o r t h A t l a n t i c region, including the N o r t h , W h i t e , Barents, K a r a a n d L a p t e v seas; B u r n s in R i d g w a y a n d H a r r i s o n , 1981) a n d h a r p seal, Phoca groenlandica (100,000 in t h e " W e s t Ice", t h e J a n M a y e n s e c t o r of t h e G r e e n l a n d Sea; R o n a l d a n d H e a l e y in R i d g w a y a n d H a r r i s o n , 1981; c o r r e s p o n d i n g to a n a n n u a l p u p p r o d u c t i o n
0924-7963/92/$05.00 © 1992 - Elsevier Science Publishers B.V. All rights reserved
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Fig. 1. Map showing the route of RV Polarstern during the ARK V / 2 expedition in the Norwegian and Greenland seas, June 6 till July 4, 1988. The dots represent the position of the counts of seabirds and marine mammals. Each dot represents two successive half an hour counts. The limit between the main zones is also shown (see text) between Atlantic water (ATL. W) and Polar water (POLAR W.), between open water ad pack ice (broken line).
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SEABIRDS AND MARINE MAMMALS IN NORWEGIAN AND G R E E N L A N D SEAS
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Fig. 2. N u m b e r s of Fulmars. Fulmarus glacialis, dark morph, observed per half hour, as a function of the seawater temperature
(°c). of about 30,000; Anonymous, 1990). The walrus, Odobenus rosmarus, is present in small numbers with "no more than a few hundred individuals" for the East Greenland and Spitsbergen populations (Hay in Ridgway and Harrison, 1981). Among the large cetaceans, the sperm whale, Physeter macrocephalus, shows a very extensive distribution; in the North Atlantic an estimated population of 190,000 individuals are present, of which 60,000 are males (only males are present north of 45-50°N; Rice in Ridgway and Harrison, 1989). The bottlenose whale Hyperoodon ampullatus is considered as depleted in the North Atlantic (Mead in Ridgway and Harrison, 1989). The baleen whales are mainly the minke whale, Balaenoptera acurostrata (110,000 in the North East Atlantic: Stewart and Leatherwood in Ridgway and Harrison, 1985). The aim of this study was to determine the summer distribution at sea of seabirds and marine mammals in the North East Atlantic ocean and their ecological role in terms of food intake. Material and methods
I participated in the ARK V / 2 expedition of the German icebreaking RV Polarstern in the Norwegian and Greenland seas, from June 6 till July 4, 1988 (Fig. 1). Counts were carried out from the bridge, 17 m above sea level, during standard half hour periods, without any width limit. A total of 380 half hour counts were devoted to counting the higher
trophic levels, when the ship was moving, but the difference between a moving and a stationary ship sometimes becomes very tiny in the closed pack. In order to calculate densities, seabirds transect counts are often limited to a fixed width (300 m). I, however, considered that some species (e.g. Storm Petrel, alcids sitting on the water) could not be quantitatively detected as far as 300 m away from the ship and that other species can be detected at much larger distances (e.g. Gannet). In the case of marine mammals, the 300 m transect could not be applied for evident reasons. This is why I decided to count seabirds and marine mammals during transects with unlimited width. The actual width of the covered area was evaluated for each species on the basis of existing specific conversion factors (Crossin, 1974; Wiens et al., 1978; Bourne, 1982; Diamond et al., 1986) and personal experience (Joiris, 1989, 1991; Joiris and Tahon, 1991). These factors take mainly into account the conspicuousness of the different species, depending on colour pattern, size and fizz. In order not to correct for other local factors such as light conditions, state of the sea, etc., the conversion was not applied on every count separately, but on the mean (or median) value for a complete zone. Problems in the determination of densities of seabirds are the existence of "followers" accompanying the ship, sometimes for long periods, and the possible movements of birds, e.g. between the breeding place and feeding grounds or from one
76
C.R. JO1RIS
sity (see Wiens et al., 1978). Only the third type of observations concern birds really belonging to the zone where they were encountered and were translated into density, knowing the ship's speed
zone to another (migration). Such data cannot be expressed as density; they are not influenced by the speed of the ship and cannot be extrapolated without causing a large overestimate of the denTABLE 1
Total numbers of seabirds and marine m a m m a l s observed in the Norwegian and Greenland seas in June 1988 (each count = half an hour) species
zone water temperature (°C, mean) number of counts
atlantic water 7,4 34
polar water 1,4 72
ice edge - 0,6 108
pack ice - 0,9 166
total
380
Fulmarus glacialis (dark) Fulmarus glacialis (light) Sula bassana Catharacta skua Stercorarius pomarinus St. parasiticus St. longicaudus Pagophila eburnea Larus hyperboreus L. glaucoides L. marinus L. fuscus L. argentatus Rissa tridactyla * Xema sabini Rhodostethia rosea Sterna paradisaea Alca torda Uria aalge Uria lomvia Alle alle Cepphus grylle Fratercula arctica
Fulmar (dark) Fulmar (light) Gannet Great Skua Pomarine Skua Arctic Skua Long-tailed Skua Ivory Gull Glaucous Gull Iceland Gull Great Black-backed Gull Lesser Black-backed Gull Herring Gull Kittiwake * Sabine's Gull Ross's Gull Arctic Tern Razorbill C o m m o n Guillemot Briinnich's Guillemot Little A u k Black Guillemot Puffin £ birds
21 922 5 4 7 8 0 0 1 0 22 125 10 690 0 0 167 206 241 20 9 0 278 2736
437 493 0 3 2 3 0 2 14 0 2 2 0 651 0 0 2 13 74 723 1846 10 64 4341
477 522 0 0 1 2 8 59 16 1 0 2 0 372 1 0 5 0 1 2037 8889 38 11 12442
420 646 0 0 2 2 15 301 50 5 4 2 0 151 1 1 4 0 0 92 3511 29 7 5243
1355 2583 5 7 12 15 23 362 81 6 28 131 10 1864 2 1 178 219 36 2872 14255 77 360 24762
Delphinus delphis Orcinus orca Physeter macrocephalus Hyperoodon ampullatus Balaenoptera acurostrata
common dolphin killer whale sperm whale northern bottlenose whale minke whale large whale sp. £ cetaceans
3 3 0 0 2 0 10
0 0 0 0 0 2 0
0 0 2 1 1 0 4
0 0 0 0 0 0 0
3 3 2 1 3 2 14
Odobenus rosmarus Phoca hispida Phoca groenlandica Halichoerus grypus Erignathus barbatus Cystophora cristata
walrus ringed seal harp seal grey seal bearded seal hooded seal Y pinnipeds
0 0 0 0 0 0 0
0 0 0 0 0 1 1
0 19 136 01 0 316 472
2 t05 5 0 2 116 230
2 124 141 1 2 433 703
Ursus maritimus
ice bear
0
0
0
2
2
* Without taking into account an important concentration of Kittiwakes off Iceland (see text.)
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Fulmarus glacialis, dark morph. Four classes: nihil; 1-5; 6-25; 26-125 birds per hour (see legend Fig. 1).
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Fig. 3. Map showing the distribution of the Fulmar,
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C.R. JOIRIS
and evaluating the width of the transect actually surveyed. This concerns birds sitting on the water or showing local movements: no correction was introduced for locally flying birds (see Burnham et al., 1980). The results are interpreted as a function of the main water masses, which have been defined by their salinity and temperature and which correspond to differences in ecological structure (Joiris, 1978; Joiris et al., 1982); in this study the available information was water temperature and our own data on the ice cover. Four main zones were defined: - Atlantic water: > 4.9°C (mean 7.4°; maximum 8.7°); - polar open water: < 4.9°C (mean 1.4°; min -1.4°; max 4.1°); the front between Atlantic and Polar water was detected by a jump in water temperature from 4.1 to 4.9°C; - ice edge: in open water, with visible pack ice (at distances less than 15 km) or in the pack ice, with visible ice edge (less than 5 km) or marginal ice zone with low density of ice floes; - pack ice: ice floes or closed pack. Results
and
present at the ice edge, in polar water and in the pack ice. The light morph, also encountered in each zone, showed the highest density in Atlantic water, where it represented 30% of the avifauna (Figs. 2-5). - Ivory Gulls, Pagophila eburnea, were, as expected, encountered at the ice edge and in the pack ice (Fig. 6). Some groups, however, seemed to j o i n - - o r even p r e c e e d - - t h e ship at intervals varying between hours and days, so that the resuits presented here probably overestimate their actual density. - The distribution of the Kittiwake, Rissa tridactyla, reflects its presence in all zones, with a maximum density in Atlantic water, without taking into account two important coastal concentrations of 500 and 2500 individuals, respectively, off Iceland (stations 3 and 4; these results are included neither in the tables nor calculations). A similar situation was noted again in the same region in July 1988 (Joiris and Tahon, 1991). - Two Sabine's Gulls, Xema sabini, were observed, one adult at station 28 and a sub-adult at station 53. - An adult Ross's Gull, Rhodostethia rosea, was observed at stations 178 to 180, on June 18, in company of a group of 21 Ivory Gulls and 3 Kittiwakes, and exhibited high aggressivity against the latter. - The Common Guillemot, Uria aalge, was clearly bound to Atlantic water and, to a lower extent, present in adjacent polar water (Figs. 7 and 8).
discussion
Comments on selected species." (see Table 1 and Figs. 2 to 13) The Fulmar, Fulmarus glacialis, was encountered in all zones. The dark morph was mainly -
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Fig. 4. Numbers of Fulmar, Fulmarus glacialis, light morph, observed per half hour, as a function of the seawater temperature.
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Fig. 6. N u m b e r s of Ivory Gulls, Pagophila eburnea, observed per half hour, as a function of the seawater temperature.
The Brtinnich's Guillemot, Uria lomvia, was observed in high density at the ice edge and in Polar water (Figs. 9 and 10). The Little Auk showed densities as high as 82 per count at the ice edge (for a total of 115 birds per count) and, to a lesser extent, in polar water and the pack ice (Figs. 11 and 12). It was the most abundant species in the whole region and formed more than 50% of the avifauna in three of the four zones: Polar water, ice edge and pack ice. A significant part of all counted alcids were moving, mainly along an East-West axis between their breeding colonies in Spitsbergen or Bear Island and their feeding grounds and were not included in the calculations because they repre-
sent a flux rather than a density and, from the ecological point of view, do not belong to the zones they fly across. This was mainly the case for Common Guillemot (241 local birds, 600 moving in Atlantic water), Briinnich's Guillemot (respectively 20 and 504 across Atlantic water; 723 and 638 in Polar water), Little Auk (1846 and 785 in Polar water) and Black Guillemot (64 local, 22 moving across Polar water). These results do fit with observations in a similar zone by Meltofte (1972) and Melhum (1989). From a quantitative point of view, we compared our summer data with the observations of Brown (1984) in February-March 1982 in the
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Fig. 7. N u m b e r s of C o m m o n Guillemots, Uria aalge, observed per half hour, as a function of the seawater temperature.
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Fig. 8. Map showing the distribution of the Common Guillemot, Uria aalge. Four classes: nihil; 1-5; 6-25; 26-125 birds per hour (see legend Fig. 1).
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C.R. JO]RXS
same region. He counted lower numbers of Fulmars: 0.4 to 1 birds per km, with maxima of 2 to 4 off the coasts of Spitsbergen, Iceland and Norway. The density of Ivory Gull was comparable, with 0.1 and 0.3 birds per km in the northern zone and off Jan Mayen. Numbers of Kittiwake were comparable in the southern regions (0.8 per kin), but lower in the northern polar water (0.010.1). Numbers of Guillemots were much lower in February-April: he noted almost no Guillemot in polar water with maxima of 0.1 to 0.5 off the coasts, while our June figures show mean values of 1 bird per km in polar water and 1.7 at the ice edge. The distribution of Little Auk was similar, with 1.4-0.6 birds per km in February-March (0.15-0.54 in July) but higher values in the South: 0-0.8 and even 2.5 North of the Faeroes (0.01 in Atlantic water in July). This comparison shows that the results obtained by Brown (1984) are basically similar to our's, the main differences in distribution reflecting differences between late winter distribution in February-March versus summer distribution in June. In July 1973, a transect between Norway and Spitsbergen showed important concentrations of seabirds (Kittiwake, Razorbill, Little Auk and Guillemots) near the breeding colonies (Byrkjedal et al., 1974). The importance of such concentrations, however, was enhanced by the fact that main breeding colonies were approached during a very short, two-day trip: Flug6y (Norway), Bear Island and S6rkapp (Spitsbergen).
When compared with own data obtained in the same region in July 1988 (table 3), similarities are noted in the distribution and the density of the different species. The main exceptions are the Kittiwake and the alcids (mainly Little Auk and Bdinnich's Guillemot, but also Common Guillemot), with much lower numbers in July than in June: this observation may reflect the fact that they already had started leaving the most northern part of their summer feeding grounds at the end of the breeding season. - Very low numbers of cetaceans were noted, basically belonging to the species already noted during earlier cruises in the region (e.g. Joiris and Tahon, 1987) and again in July 1988 (Joiris and Tahon, 1991): killer whale, Orcinus orca, sperm whale, Physeter rnacrocephalus, northern bottlenose whale, Hyperoodon ampullatus, and minke whale, Balaenoptera acurostrata. - 700 pinnipeds were encountered, mainly represented by 430 hooded seals Cystophora cristata, of which 313 at stations 319 to 329 (175 at 320 and 100 at 321), 140 harp seals Phoca groenlandica at the ice edge (110 at station 216: adults and juveniles of almost the same size as the adults, white with dark spots on the back; 23 adults at station 212 and 2 at 213), and 125 ringed seals Phoca hispida with a more scattered distribution on the pack (Fig. 13). An adult walrus Odobenus rosmarus was sleeping on a small ice floe at station 88 and one individual was noted at station 199.
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Fig. 9. Numbers of Briinnich's Guillemots, Uria lomvia, observed per half hour, as a function of the seawater temperature.
SEABIRDS AND MARINE MAMMALSIN NORWEGIANAND GREENLANDSEAS
83
TABLE 2 Calculated ingestion rate by seabirds and marine mammals in the Norwegian and Greenland seas in June 1988, in kg fresh weight/km2.day; values lower than 0.005 were omitted atlantic water 12.5
polar water 12.5
ice edge 12.5
pack ice 4.5
mean
0.02 0.77 0.01 0.01 0.01 0.01 0.00 0.00 0.00 0.04 0.12 0.01 0.40 0.04 0.29 0.43 0.03 0.00 0.00 0.28 2.47
0.19 0.19 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.18 0.00 0.01 0.06 0.57 0.46 0.00 0.03 1.71
0.14 0.14 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.00 0.00 0.00 0.07 0.00 0.00 0.00 1.07 1.46 0.01 0.00 2.91
0.22 0.31 0.00 0.00 0.00 0.00 0.01 O.10 0.04 0.00 0.00 0.00 0.05 0.00 0.00 0.00 0.09 1.04 0.02 0.00 1.89
0.14 0.35 0.00 0.00 0.00 0.00 0.00 0.03 0.02 0.01 0.03 0.00 0.17 0.01 0.07 0.12 0.44 0.74 0.01 0.08 2.24
75 4000 3000 6500 35000
0.02 0.18 0.00 0.11 0.38 0.69
0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.12 0.02 0.00 0.15
0.00 0.00 0.00 0.00 0.00 0.00
0.01 0.04 0.03 0.03 0.09 0.21
0.2 0.3 0.3 0.5 0.2
1000 50 125 200 125
0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.01 0.21 0.00 0.00 0.55
0.02 0.15 0.01 0.01 0.21 0.40
0.00 0.04 0.06 0.00 0.13 0.24
0.2
400
0.00
0.00
0.00
0.01
0.00
3.15
1.71
3.61
2.30
2.69
mean ship's speed (knots species
specific conversion factor *
Fullmarus glacialis (dark) Fulrnarus glacialis (light) Sula bassana Stercorarius skua St. Pomarinus St. parasiticus St. longicaudus Pagophila eburnea Larus hyperboreus L. marinus L. fuscus L. argentatus Rissa tridactyla * * Sterna paradissea Alca torda Uria aalge Uria lornvia Alle alle Cepphus grylle Fratercula arctica birds * *
2.4 2.0 1.6 2.8 3.0 3.2 3.4 2.0 2.4 2.8 2.4 2.4 2.2 2.2 3.6 3.6 3.6 4.0 3.8 3.6
Delphinus delphis Orcinus orca Hyperoodon ampullatus Balaenoptera acurostrata large whale sp X cetaceans
0.6 0.3 0.3 0.2 0.2
Odobenus rosmams Phoca hispida Phoca groenlandica Erignathus barbatus Cystophora cristata pinnipeds Ursus maritimus
biomass (kg)
0.70 0.80 3.00 1.40 0.90 0.50 0.30 0.50 1.50 1.60 0.75 1.10 0.42 0.11 0.72 1.00 0.92 0.16 0.41 0.46
total
* see text ** without taking into account an important concentration of Fulmars and Kittiwakes off Iceland (see text).
-
T h e p o l a r b e a r Ursus m a r i t i m u s
was encoun-
Food intake
t e r e d t w i c e , at s t a t i o n s 68 a n d 303. A t h i r d i n d i v i d u a l , n o t i c e d at s t a t i o n 189 o u t o f t h e c o u n t i n g p e r i o d , w a s n o t i n c l u d e d in t h e r e s u l t s .
Seabird and marine
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p r e s s e d as n u m b e r s p e r c o u n t ( p e r h a l f h o u r ; s e e
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Fig. 10. Map showing the distribution of the Briinnich's Guillemot, Uria lomvia. Four classes: nihil; 1-10; 11-100; 100 birds per hour (see legend fig. 1).
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i
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SEABIRDS AND MARINE MAMMALS IN NORWEGIAN AND GREENLAND SEAS
85
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2 water temperature (°C)
Fig. 11. Numbers of Little Auks, Alle alle, observed per half hour, as a function of the seawater temperature.
Table 1). They are then converted into densities by using a specific conversion factor reflecting at which distance animals could be detected and the average ship's speed in the different geographical zones. The density (numbers/km 2) is then translated into daily food ingestion by the equation I = 0,191.W 0"723"N
(1)
where I is the ingestion in kg fresh weight/km 2 day, W the individual biomass in kg and N the density in numbers per km 2. This equation is derived (Schneider et al., 1987) from the allometric formula of Lasiewski and Dawson (1967) for the standard metabolic rate (SMR), a conversion factor of 2.8 SMR for calculation of the daily food requirement (Kooyman et al., 1982) and conversion factors of 1.33 for a 75% assimilation efficiency and of 6.37 k J / g fresh weight. The equation was established for seabirds, but the equivalent allometric relation for mammals (Q = 70.W 0"7325, kcal/day)was considered similar enough to apply the same equation (1) to all homeotherms. Other equations such as food requirement = 4% of W/day, or the daily requirements already calculated for minke and fin whales (Lockyer, 1981) also provide values of the same order of magnitude.
The calculated food intake (Tables 2 and 3) by seabirds represents about 2.2 kg fw/km 2 day, with a higher value (2.5) for Atlantic water, intermediate at the ice edge (2.9) and lower in the pack and Polar water (1.9 and 1.7). The role of cetaceans was clearly smaller, with a mean value of 0.2 kg/km 2 day and a maximum of 0.7 in Atlantic water. This conclusion, however, depends on low numbers of individuals with an important biomass and therefore represents only a very rough evaluation. The food intake by pinnipeds was 0.2 kg/km 2 day; they were mainly harp and hooded seals at the ice edge, and hooded and ringed seals on the pack ice. The June 1988 results are of the same order of magnitude as the data obtained in the same region in July 1988; the main differences, as already discussed about the numbers (Table 3), being the presence of alcids in clearly higher numbers in June than in July. As a consequence, the comparison between Antarctic and Arctic ecosystems (Joiris and Tahon, 1991) also remains valid.
Acknowledgements I am very grateful to the Alfred Wegener Institute for Polar Research (Bremerhaven) and
86
c.R. JOIRIS
TABLE 3 Synopsis of the main results obtained in the Norwegian and Greenland seas in June and July 1988 (numbers per 1/2 hour; food ingestion in kg fresh weight/kmZ.day)
species
zone atlantic water
polar water
ice edge
pack ice
mean
A. Numbers June 1988 Fulmarus glacialis (dark) Fulmarus glacialis (light) Pdgophila eburnea Rissa tridactyla * Uria aalge Uria lomvia Alle alle birds * cetaceans pinnipeds
0.6 27.1 0.0 20.3 7.1 0.6 0.3 80.5 0.29 0.00
6.1 6.9 0.0 9.0 1.0 10.0 25.6 60.3 0.00 0.01
4.4 4.8 0.6 3.4 0.0 18.9 82.3 115.2 0.04 4.37
2.5 3.9 1.8 0.9 0.0 0.6 21.1 31.6 0.00 1.39
3.4 10.7 0.6 8.4 2.0 7.5 32.3 71.9 0.08 1.44
Numbers July 1988 (**) Fulmarus glacialis (dark) Fulmarus glacialis (light) * Pagophila eburnea Rissa tridactyla * Uria aalge Uria lornvia Alle alle birds * cetaceans E pinnipeds
1.4 23.2 0.0 3.2 0.8 0.7 0.0 32.6 0.10 0.00
1.0 20.8 0.0 5.2 0.6 10.3 1.2 39.6 0.07 0.04
3.7 3.1 0.0 1.5 0.0 1.8 3.5 14.2 0.07 12.13
2.1 2.0 0.6 0.3 0.0 0.1 1.0 6.4 0.00 0.44
2.1 12.3 0.2 2.6 0.4 3.2 1.4 23.2 0.00 3.13
B. Food intake June 1988 Fulmarus glacialis (dark) Fulmarus glacialis (light) Pagophila eburnea Rissa tridactyla * Uria aalge Uria lomvia Alle alle birds * E cetaceans E pinnipeds Ursus maritimus total
0.02 0.77 0.00 0.40 0.43 0.03 0.00 2.47 0.69 0.00 0.00 3.15
0.19 0.19 0.00 0.18 0.06 0.57 0.46 1,71 0,00 0,00 0,00 1.71
0.14 0.14 0.01 0.07 0.00 1.07 1.46 2.91 0.15 0.55 0.00 3.61
0.22 0.31 0.10 0,05 0.00 0.09 1.04 1.89 0.00 0.40 0.01 2.30
0.14 0.35 0.03 0.17 0.12 0.44 0.74 2.24 0.21 0.24 0.00 2.69
Food intake July 1988 (**) Fulmarus glacialis (dark) Fulmarus glacialis (light) * Pagophila eburnea Rissa tridactyla * Uria aalge Uria loravia Alle alle E birds * ~, cetaceans pinnipeds Ursus maritimus total *
0.06 0.94 0.00 0.09 0.06 0.05 0.00 1.40 0.67 0.00 0.00 2.07
0.04 0.84 0.00 0.14 0.05 0.82 0.03 0.95 0.34 0.01 0.00 1.30
0.20 0.15 0.00 0.05 0.00 0.18 0.11 0.73 0.19 2.36 0.00 3.28
0.11 0.10 0.02 0.01 0.00 0.01 0.03 0.28 0.00 0.12 0.00 0.40
0.10 0.51 0.01 0.07 0.03 0.27 0.04 1.09 0.30 0.62 0.00 2.01
* Without taking into account an important concentration of Fulmars and Kittiwakes off Iceland (see text). ** Joiris and Tahon, 1991.
65c
=
-
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i~ ~ ' .
---------..__I__ 0 o
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,_/,
0o
i00
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-V
J
80°
75 o
70 °
~,~0o65 ?.o
Fig. 12. Map showing the distribution of the Little Auk, Alle alle. Three classes: nihil; 1-5; 6-25; 26-125 birds per hour (see legend Fig. 1).
70 °
75 c
80°
I00
oo
"~
88
C.R. JOIRIS
30. 25. 20.
& 15. 10. 5,
• 00
-2
0000
o
;,
1'o
water temperature (°C)
Fig. 13. Numbers of ringed seals. Phoca hipida, observed per half hour, as a function of seawater temperature.
the chief scientist J. Meincke for the invitation on board RV Polarstern. Other costs were funded by the Belgian National Science Foundation (NFWO). References Anonymous, 1990. Report of the working group on harp and hooded seals. ICES. C.M. 1990/Assess: 8.25 pps. Bourne, W.R.P., 1982. The manner in which wind drift leads to seabird movements along the east coast of Scotland. Ibis, 124: 81-88. Brown, R.G.B., 1984. Seabirds in the Greenland, Barents and Norwegian Seas, February-April 1982. Polar Res., 2: 1-18. Burnham, K.P., Anderson, D.R. and Laake, JL. 1980. Estimation of density from line transect sampling of biological populations. Wildl. Monogr., 72. Byrkjedal, I., Alendal, E. and Lindberg, O.F. 1974. Counts of sea-birds between Norway and Spitsbergen in the summer 1973. Nor. Polarinst. Arbok, 1974: 265-269. Crossin, R.S., 1974. The storm petrels (Hydrobatidae). In: W.B. King (Editor), Pelagic studies of seabirds in the central and eastern North Pacific Ocean. Smithsonian Contrib. Zool, 158: 154-205. Croxall, J.P., Evans, P.G.H. and Schreiber, R.W. (Editors) 1984. Status and conservaton of the world's seabirds. ICBP tech. publ. No. 2, 778 pp. Diamond, A.W., Gaston, A.J. and Brown, R.G.B. 1986. Converting P1ROP counts of seabirds at sea to absolute densities. Can. Wildl. Serv, Prog. Notes, No. 164, 21 pp. Joiris, C., 1978. Seabirds recorded in the northern North Sea in July: the ecological implications of their distribution. Gerfaut, 68: 419-440. Joiris, C., Billen, G., Lancelot, C., Daro, M.H., Mommaerts, J.P., Bertels, A., Bossicart, M., Nijs, J. and Hecq, J.H., 1982. A budget of carbon cycling in the Belgian coastal zone: relative roles of zooplankton, bacterioplankton and
benthos in the utilization of primary production. Neth. J.Sea Res., 16: 260-275. Joiris, C. and Tahon, J., 1987. Distribution of seabirds and cetaceans in the N.E. Atlantic and Arctic oceans. Eur. Cetacean Soc. 1987, pp. 28-29. Joiris, C.R., 1989. Seabirds in the North Sea: distribution and ecological role. ICES, CM. 1989/N:8. 7 pp. Joiris, C.R., 1991. Spring distribution of seabirds and marine mammals in the Weddell Sea, Antarctica. Polar Biol., in press. Joiris, C.R. and Tahon, J., 1991. Distribution and ecological role of seabirds and marine mammals in the Norwegian and Greenland seas (July 1988). Acad. R. Sci. Outre-Mer., in press. Kooyman, G.L., Davis, R.W., CroxaU, J.P. and Costa, D.P., 1982. Diving depths and energy requirements of King Penguins. Science, 217: 726-727. Lasiewski, R.C. and Dawson, W.R., 1967. A re-examination of the relation between standard metabolic rate and body weight in birds. Condor, 69: 13-23. Lockyer, C., 1981. Growth and energy budgets of large baleen whales from the southern hemisphere. In: Mammals in the seas, FAO Fisheries Series, Rome 5, vol. 3: 379-487. Melhum, F., 1989. Summer distribution of seabirds in northern Greenland and Barents Seas. Nor. Polarinst. Spr., 191, 56 pp. Meltofte, H., 1972. Ornithological observations in the Norwegian Sea, the Greenland Sea and NE Greenland, JulyAugust 1972. Dansk Ornithol. Foren. Tidsskr, 66: 108-112. Nettleship, D.N. and Birkhead, T.R. 1985. The Atlantic Alcidae. Academic Press, London, 574 pp. Ridgway, S.H. and Harrison R.J. (Editors), 1981. Handbook of Marine Mammals, vols. 1 & 2. Academic Press, London. 235 and 359 pp. Ridgway, S.H. and Harrison, R.J. (Editors), 1985. Handbook of Marine Mammals vol. 3. Academic Press, London, 362 PP. Ridgway, S.H. and Harrison R.J. (Editors), 1989. Handbook
SEABIRDS A ND M A R I N E MAMMALS IN N O R W E G I A N AND G R E E N L A N D SEAS
of Marine Mammals, vol. 4. Academic Press, London, 442 PP. Schneider, D.C., Hunt Jr. G.L and Powers, K.D., 1987. Energy flux to pelagic birds: Bering Sea and Nortwest Atlantic. In: J.P. Croxall (Editors), Seabirds: Feeding Ecology and Role in Marine Ecosystems. Cambridge University Press, pp. 259-277.
89
Wiens, J.A., Heinemann, D. and Hoffman, W., 1978. Community structure, distribution and inter-relationships of marine birds in the Gulf of Alaska. Final rep. Principal lnvestig., vol. 3. Boulder, Colorado, NOAA.
73
Elsevier Science Publishers B.V., Amsterdam
Summer distribution and ecological role of seabirds and marine mammals in the Norwegian and Greenland seas (June 1988) Claude R. Joiris
Laboratory for Ecotoxieology, Free University of Brussels (VUB), Pleinlaan, 2 B-1050 Brussels, Belgium (Received September 20, 1990; revised version accepted April 9, 1991)
ABSTRACT Joiris, C.R., 1992. Summer distribution and ecological role of seabirds and marine mammals in the Norwegian and Greenland seas. J. Mar. Syst., 3: 73-89. During the ARK V/2 expedition of RV Polarstern in the Norwegian and Greenland seas in June 1988, 380 half hour counts for marine vertebrates (seabirds, pinnipeds and cetaceans) were carried out. Results are presented as total numbers encountered and then converted into density and food intake.Mean food intake was 2.2 kg fresh weight per km2 per day for seabirds, with a higher value in Atlantic water (2.5) lower values in polar water and the pack ice (1.7 and 1.9), and an intermediate value at the ice edge. The main species were the alcids (1.5, primarily Little Auk, Alle alle and Briinnich's Guillemot, Uria Iomvia), the Fulmar, Fulmarus glacialis (0.5), and the Kittiwake, Rissa tridactyla (0.2). The ecological role of cetaceans was clearly lower, with a mean value of 0.2 and a maximum of 0.7 in Atlantic water (rough evaluation, due to the low number of contacts). The food intake by pinnipeds was 0.55 kg/km 2 day at the ice edge and 0.4 in the pack ice; they were mainly harp, Phoca groenlandica and hooded seals, Cystophora cristata, in one main concentration each and ringed seals, Phoca hispida, scattered on the pack. Data for July 1988 show a great similarity with these results, except for a lower density of alcids, which probably reflects that Little Auk, Briinnich's Guillemot and Common Guillemot, Uria aalge already had started to leave the region.
Introduction O u r k n o w l e d g e o f s e a b i r d s is g e n e r a l l y g o o d as far as t h e i r b r e e d i n g colonies a r e c o n c e r n e d (e.g. Croxall et al., 1984), b u t less is k n o w n a b o u t t h e i r d i s t r i b u t i o n at sea. Such d a t a , however, p r o v i d e i m p o r t a n t i n f o r m a t i o n , not only a b o u t t h e ecology o f seabirds, b u t also a b o u t t h e ecological s t r u c t u r e a n d t h e f u n c t i o n i n g o f the e c o s y s t e m s to which they b e l o n g (Joiris, 1978; Joiris et al., 1982). T h e b r e e d i n g p o p u l a t i o n s of the alcids a r o u n d the N o r w e g i a n a n d G r e e n l a n d seas a r e well studied a n d c o n c e r n (in millions o f pairs): 0.53 R a z o r bills, A k a torda, m a i n l y in I c e l a n d ; 2.5 C o m m o n G u i l l e m o t s , Uria aalge (of which 1.6 in I c e l a n d a n d 0.75 in B e a r Island); 4.9 Briinnich's; G u i l l e mots, U. Iomvia (2 in I c e l a n d , 1 in S p i t s b e r g e n , 1 in N o v a y a Z e m l y a a n d 0.75 in B e a r Island); 1.6
Little A u k s , Alle alle (1 in Spitsbergen); 0.12 Black G u i l l e m o t s , Cepphus grille a n d 4.3 Puffins, Fratercula arctica (3 in I c e l a n d a n d 1.3 in N o r way; N e t t l e s h i p a n d B i r k h e a d , 1985). P i n n i p e d s a r e m a i n l y r e p r e s e n t e d by the r i n g e d seal, Phoca hispida hispida (0.1 to 3 o b s e r v e d p e r k m 2 all zones o f t h e i r d i s t r i b u t i o n c o n s i d e r e d t o g e t h e r ; F r o s t a n d Lowry in R i d g w a y a n d H a r r i son, 1981), h o o d e d seal, Cystophora cristata (230,000 o b s e r v e d m o u l t i n g in t h e D e n m a r k Strait: R e e v e s a n d Ling in R i d g w a y a n d H a r r i s o n , 1981), b e a r d e d seal, Erignathus barbatus (300,000 for t h e w h o l e N o r t h A t l a n t i c region, including the N o r t h , W h i t e , Barents, K a r a a n d L a p t e v seas; B u r n s in R i d g w a y a n d H a r r i s o n , 1981) a n d h a r p seal, Phoca groenlandica (100,000 in t h e " W e s t Ice", t h e J a n M a y e n s e c t o r of t h e G r e e n l a n d Sea; R o n a l d a n d H e a l e y in R i d g w a y a n d H a r r i s o n , 1981; c o r r e s p o n d i n g to a n a n n u a l p u p p r o d u c t i o n
0924-7963/92/$05.00 © 1992 - Elsevier Science Publishers B.V. All rights reserved
,~.:.,e '5
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POLAR.W
[ [ [ [
0o
June
June 30
10 °
Jr
July 3
J~
80 °
380
75 o
70 °
65 °
Fig. 1. Map showing the route of RV Polarstern during the ARK V / 2 expedition in the Norwegian and Greenland seas, June 6 till July 4, 1988. The dots represent the position of the counts of seabirds and marine mammals. Each dot represents two successive half an hour counts. The limit between the main zones is also shown (see text) between Atlantic water (ATL. W) and Polar water (POLAR W.), between open water ad pack ice (broken line).
65o
70 °
75 °
80 °
I0 °
SEABIRDS AND MARINE MAMMALS IN NORWEGIAN AND G R E E N L A N D SEAS
75
8070~
•
6oi 50i
•
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E
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•
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4 6 water temperature (°C)
8
10
Fig. 2. N u m b e r s of Fulmars. Fulmarus glacialis, dark morph, observed per half hour, as a function of the seawater temperature
(°c). of about 30,000; Anonymous, 1990). The walrus, Odobenus rosmarus, is present in small numbers with "no more than a few hundred individuals" for the East Greenland and Spitsbergen populations (Hay in Ridgway and Harrison, 1981). Among the large cetaceans, the sperm whale, Physeter macrocephalus, shows a very extensive distribution; in the North Atlantic an estimated population of 190,000 individuals are present, of which 60,000 are males (only males are present north of 45-50°N; Rice in Ridgway and Harrison, 1989). The bottlenose whale Hyperoodon ampullatus is considered as depleted in the North Atlantic (Mead in Ridgway and Harrison, 1989). The baleen whales are mainly the minke whale, Balaenoptera acurostrata (110,000 in the North East Atlantic: Stewart and Leatherwood in Ridgway and Harrison, 1985). The aim of this study was to determine the summer distribution at sea of seabirds and marine mammals in the North East Atlantic ocean and their ecological role in terms of food intake. Material and methods
I participated in the ARK V / 2 expedition of the German icebreaking RV Polarstern in the Norwegian and Greenland seas, from June 6 till July 4, 1988 (Fig. 1). Counts were carried out from the bridge, 17 m above sea level, during standard half hour periods, without any width limit. A total of 380 half hour counts were devoted to counting the higher
trophic levels, when the ship was moving, but the difference between a moving and a stationary ship sometimes becomes very tiny in the closed pack. In order to calculate densities, seabirds transect counts are often limited to a fixed width (300 m). I, however, considered that some species (e.g. Storm Petrel, alcids sitting on the water) could not be quantitatively detected as far as 300 m away from the ship and that other species can be detected at much larger distances (e.g. Gannet). In the case of marine mammals, the 300 m transect could not be applied for evident reasons. This is why I decided to count seabirds and marine mammals during transects with unlimited width. The actual width of the covered area was evaluated for each species on the basis of existing specific conversion factors (Crossin, 1974; Wiens et al., 1978; Bourne, 1982; Diamond et al., 1986) and personal experience (Joiris, 1989, 1991; Joiris and Tahon, 1991). These factors take mainly into account the conspicuousness of the different species, depending on colour pattern, size and fizz. In order not to correct for other local factors such as light conditions, state of the sea, etc., the conversion was not applied on every count separately, but on the mean (or median) value for a complete zone. Problems in the determination of densities of seabirds are the existence of "followers" accompanying the ship, sometimes for long periods, and the possible movements of birds, e.g. between the breeding place and feeding grounds or from one
76
C.R. JO1RIS
sity (see Wiens et al., 1978). Only the third type of observations concern birds really belonging to the zone where they were encountered and were translated into density, knowing the ship's speed
zone to another (migration). Such data cannot be expressed as density; they are not influenced by the speed of the ship and cannot be extrapolated without causing a large overestimate of the denTABLE 1
Total numbers of seabirds and marine m a m m a l s observed in the Norwegian and Greenland seas in June 1988 (each count = half an hour) species
zone water temperature (°C, mean) number of counts
atlantic water 7,4 34
polar water 1,4 72
ice edge - 0,6 108
pack ice - 0,9 166
total
380
Fulmarus glacialis (dark) Fulmarus glacialis (light) Sula bassana Catharacta skua Stercorarius pomarinus St. parasiticus St. longicaudus Pagophila eburnea Larus hyperboreus L. glaucoides L. marinus L. fuscus L. argentatus Rissa tridactyla * Xema sabini Rhodostethia rosea Sterna paradisaea Alca torda Uria aalge Uria lomvia Alle alle Cepphus grylle Fratercula arctica
Fulmar (dark) Fulmar (light) Gannet Great Skua Pomarine Skua Arctic Skua Long-tailed Skua Ivory Gull Glaucous Gull Iceland Gull Great Black-backed Gull Lesser Black-backed Gull Herring Gull Kittiwake * Sabine's Gull Ross's Gull Arctic Tern Razorbill C o m m o n Guillemot Briinnich's Guillemot Little A u k Black Guillemot Puffin £ birds
21 922 5 4 7 8 0 0 1 0 22 125 10 690 0 0 167 206 241 20 9 0 278 2736
437 493 0 3 2 3 0 2 14 0 2 2 0 651 0 0 2 13 74 723 1846 10 64 4341
477 522 0 0 1 2 8 59 16 1 0 2 0 372 1 0 5 0 1 2037 8889 38 11 12442
420 646 0 0 2 2 15 301 50 5 4 2 0 151 1 1 4 0 0 92 3511 29 7 5243
1355 2583 5 7 12 15 23 362 81 6 28 131 10 1864 2 1 178 219 36 2872 14255 77 360 24762
Delphinus delphis Orcinus orca Physeter macrocephalus Hyperoodon ampullatus Balaenoptera acurostrata
common dolphin killer whale sperm whale northern bottlenose whale minke whale large whale sp. £ cetaceans
3 3 0 0 2 0 10
0 0 0 0 0 2 0
0 0 2 1 1 0 4
0 0 0 0 0 0 0
3 3 2 1 3 2 14
Odobenus rosmarus Phoca hispida Phoca groenlandica Halichoerus grypus Erignathus barbatus Cystophora cristata
walrus ringed seal harp seal grey seal bearded seal hooded seal Y pinnipeds
0 0 0 0 0 0 0
0 0 0 0 0 1 1
0 19 136 01 0 316 472
2 t05 5 0 2 116 230
2 124 141 1 2 433 703
Ursus maritimus
ice bear
0
0
0
2
2
* Without taking into account an important concentration of Kittiwakes off Iceland (see text.)
65 c
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Fulmarus glacialis, dark morph. Four classes: nihil; 1-5; 6-25; 26-125 birds per hour (see legend Fig. 1).
tO° W ~
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Fig. 3. Map showing the distribution of the Fulmar,
70 °
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78
C.R. JOIRIS
and evaluating the width of the transect actually surveyed. This concerns birds sitting on the water or showing local movements: no correction was introduced for locally flying birds (see Burnham et al., 1980). The results are interpreted as a function of the main water masses, which have been defined by their salinity and temperature and which correspond to differences in ecological structure (Joiris, 1978; Joiris et al., 1982); in this study the available information was water temperature and our own data on the ice cover. Four main zones were defined: - Atlantic water: > 4.9°C (mean 7.4°; maximum 8.7°); - polar open water: < 4.9°C (mean 1.4°; min -1.4°; max 4.1°); the front between Atlantic and Polar water was detected by a jump in water temperature from 4.1 to 4.9°C; - ice edge: in open water, with visible pack ice (at distances less than 15 km) or in the pack ice, with visible ice edge (less than 5 km) or marginal ice zone with low density of ice floes; - pack ice: ice floes or closed pack. Results
and
present at the ice edge, in polar water and in the pack ice. The light morph, also encountered in each zone, showed the highest density in Atlantic water, where it represented 30% of the avifauna (Figs. 2-5). - Ivory Gulls, Pagophila eburnea, were, as expected, encountered at the ice edge and in the pack ice (Fig. 6). Some groups, however, seemed to j o i n - - o r even p r e c e e d - - t h e ship at intervals varying between hours and days, so that the resuits presented here probably overestimate their actual density. - The distribution of the Kittiwake, Rissa tridactyla, reflects its presence in all zones, with a maximum density in Atlantic water, without taking into account two important coastal concentrations of 500 and 2500 individuals, respectively, off Iceland (stations 3 and 4; these results are included neither in the tables nor calculations). A similar situation was noted again in the same region in July 1988 (Joiris and Tahon, 1991). - Two Sabine's Gulls, Xema sabini, were observed, one adult at station 28 and a sub-adult at station 53. - An adult Ross's Gull, Rhodostethia rosea, was observed at stations 178 to 180, on June 18, in company of a group of 21 Ivory Gulls and 3 Kittiwakes, and exhibited high aggressivity against the latter. - The Common Guillemot, Uria aalge, was clearly bound to Atlantic water and, to a lower extent, present in adjacent polar water (Figs. 7 and 8).
discussion
Comments on selected species." (see Table 1 and Figs. 2 to 13) The Fulmar, Fulmarus glacialis, was encountered in all zones. The dark morph was mainly -
200. 1801
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.
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Fig. 4. Numbers of Fulmar, Fulmarus glacialis, light morph, observed per half hour, as a function of the seawater temperature.
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Fig. 5. M a p showing the d i s t r i b u t i o n o f the E u ] m a r ,
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water temperature (°C)
Fig. 6. N u m b e r s of Ivory Gulls, Pagophila eburnea, observed per half hour, as a function of the seawater temperature.
The Brtinnich's Guillemot, Uria lomvia, was observed in high density at the ice edge and in Polar water (Figs. 9 and 10). The Little Auk showed densities as high as 82 per count at the ice edge (for a total of 115 birds per count) and, to a lesser extent, in polar water and the pack ice (Figs. 11 and 12). It was the most abundant species in the whole region and formed more than 50% of the avifauna in three of the four zones: Polar water, ice edge and pack ice. A significant part of all counted alcids were moving, mainly along an East-West axis between their breeding colonies in Spitsbergen or Bear Island and their feeding grounds and were not included in the calculations because they repre-
sent a flux rather than a density and, from the ecological point of view, do not belong to the zones they fly across. This was mainly the case for Common Guillemot (241 local birds, 600 moving in Atlantic water), Briinnich's Guillemot (respectively 20 and 504 across Atlantic water; 723 and 638 in Polar water), Little Auk (1846 and 785 in Polar water) and Black Guillemot (64 local, 22 moving across Polar water). These results do fit with observations in a similar zone by Meltofte (1972) and Melhum (1989). From a quantitative point of view, we compared our summer data with the observations of Brown (1984) in February-March 1982 in the
s° 1 J:z
70.
6oi 5o!
"6 E
40J
(.9
20~
E E
l OJ
8
30~ eO
0'
a
•O
1'0
2 water temperature (°C)
Fig. 7. N u m b e r s of C o m m o n Guillemots, Uria aalge, observed per half hour, as a function of the seawater temperature.
65 °
_
IOOw
Jr
..---_ - __2"
-
-
-
-/
10 0
OO
_~
-t-
0o
"~0°
÷ F
80 °
75 o
70 °
Fig. 8. Map showing the distribution of the Common Guillemot, Uria aalge. Four classes: nihil; 1-5; 6-25; 26-125 birds per hour (see legend Fig. 1).
ee"
°o.-~-
°
.oo/
]o
65 °
"
o¢
g
Z
m m Z
©
Z
Z
Z ©
>
>
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_=
82
C.R. JO]RXS
same region. He counted lower numbers of Fulmars: 0.4 to 1 birds per km, with maxima of 2 to 4 off the coasts of Spitsbergen, Iceland and Norway. The density of Ivory Gull was comparable, with 0.1 and 0.3 birds per km in the northern zone and off Jan Mayen. Numbers of Kittiwake were comparable in the southern regions (0.8 per kin), but lower in the northern polar water (0.010.1). Numbers of Guillemots were much lower in February-April: he noted almost no Guillemot in polar water with maxima of 0.1 to 0.5 off the coasts, while our June figures show mean values of 1 bird per km in polar water and 1.7 at the ice edge. The distribution of Little Auk was similar, with 1.4-0.6 birds per km in February-March (0.15-0.54 in July) but higher values in the South: 0-0.8 and even 2.5 North of the Faeroes (0.01 in Atlantic water in July). This comparison shows that the results obtained by Brown (1984) are basically similar to our's, the main differences in distribution reflecting differences between late winter distribution in February-March versus summer distribution in June. In July 1973, a transect between Norway and Spitsbergen showed important concentrations of seabirds (Kittiwake, Razorbill, Little Auk and Guillemots) near the breeding colonies (Byrkjedal et al., 1974). The importance of such concentrations, however, was enhanced by the fact that main breeding colonies were approached during a very short, two-day trip: Flug6y (Norway), Bear Island and S6rkapp (Spitsbergen).
When compared with own data obtained in the same region in July 1988 (table 3), similarities are noted in the distribution and the density of the different species. The main exceptions are the Kittiwake and the alcids (mainly Little Auk and Bdinnich's Guillemot, but also Common Guillemot), with much lower numbers in July than in June: this observation may reflect the fact that they already had started leaving the most northern part of their summer feeding grounds at the end of the breeding season. - Very low numbers of cetaceans were noted, basically belonging to the species already noted during earlier cruises in the region (e.g. Joiris and Tahon, 1987) and again in July 1988 (Joiris and Tahon, 1991): killer whale, Orcinus orca, sperm whale, Physeter rnacrocephalus, northern bottlenose whale, Hyperoodon ampullatus, and minke whale, Balaenoptera acurostrata. - 700 pinnipeds were encountered, mainly represented by 430 hooded seals Cystophora cristata, of which 313 at stations 319 to 329 (175 at 320 and 100 at 321), 140 harp seals Phoca groenlandica at the ice edge (110 at station 216: adults and juveniles of almost the same size as the adults, white with dark spots on the back; 23 adults at station 212 and 2 at 213), and 125 ringed seals Phoca hispida with a more scattered distribution on the pack (Fig. 13). An adult walrus Odobenus rosmarus was sleeping on a small ice floe at station 88 and one individual was noted at station 199.
250. ~-
.
•
200. 150. 100.
5 9 •~ E
:2
50.
• • , I.... 4dl
,
t1~
% •
0.
~
ca
2
o
,;
;
;
lO
water temperature (°C)
Fig. 9. Numbers of Briinnich's Guillemots, Uria lomvia, observed per half hour, as a function of the seawater temperature.
SEABIRDS AND MARINE MAMMALSIN NORWEGIANAND GREENLANDSEAS
83
TABLE 2 Calculated ingestion rate by seabirds and marine mammals in the Norwegian and Greenland seas in June 1988, in kg fresh weight/km2.day; values lower than 0.005 were omitted atlantic water 12.5
polar water 12.5
ice edge 12.5
pack ice 4.5
mean
0.02 0.77 0.01 0.01 0.01 0.01 0.00 0.00 0.00 0.04 0.12 0.01 0.40 0.04 0.29 0.43 0.03 0.00 0.00 0.28 2.47
0.19 0.19 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.18 0.00 0.01 0.06 0.57 0.46 0.00 0.03 1.71
0.14 0.14 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.00 0.00 0.00 0.07 0.00 0.00 0.00 1.07 1.46 0.01 0.00 2.91
0.22 0.31 0.00 0.00 0.00 0.00 0.01 O.10 0.04 0.00 0.00 0.00 0.05 0.00 0.00 0.00 0.09 1.04 0.02 0.00 1.89
0.14 0.35 0.00 0.00 0.00 0.00 0.00 0.03 0.02 0.01 0.03 0.00 0.17 0.01 0.07 0.12 0.44 0.74 0.01 0.08 2.24
75 4000 3000 6500 35000
0.02 0.18 0.00 0.11 0.38 0.69
0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.12 0.02 0.00 0.15
0.00 0.00 0.00 0.00 0.00 0.00
0.01 0.04 0.03 0.03 0.09 0.21
0.2 0.3 0.3 0.5 0.2
1000 50 125 200 125
0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.01 0.21 0.00 0.00 0.55
0.02 0.15 0.01 0.01 0.21 0.40
0.00 0.04 0.06 0.00 0.13 0.24
0.2
400
0.00
0.00
0.00
0.01
0.00
3.15
1.71
3.61
2.30
2.69
mean ship's speed (knots species
specific conversion factor *
Fullmarus glacialis (dark) Fulrnarus glacialis (light) Sula bassana Stercorarius skua St. Pomarinus St. parasiticus St. longicaudus Pagophila eburnea Larus hyperboreus L. marinus L. fuscus L. argentatus Rissa tridactyla * * Sterna paradissea Alca torda Uria aalge Uria lornvia Alle alle Cepphus grylle Fratercula arctica birds * *
2.4 2.0 1.6 2.8 3.0 3.2 3.4 2.0 2.4 2.8 2.4 2.4 2.2 2.2 3.6 3.6 3.6 4.0 3.8 3.6
Delphinus delphis Orcinus orca Hyperoodon ampullatus Balaenoptera acurostrata large whale sp X cetaceans
0.6 0.3 0.3 0.2 0.2
Odobenus rosmams Phoca hispida Phoca groenlandica Erignathus barbatus Cystophora cristata pinnipeds Ursus maritimus
biomass (kg)
0.70 0.80 3.00 1.40 0.90 0.50 0.30 0.50 1.50 1.60 0.75 1.10 0.42 0.11 0.72 1.00 0.92 0.16 0.41 0.46
total
* see text ** without taking into account an important concentration of Fulmars and Kittiwakes off Iceland (see text).
-
T h e p o l a r b e a r Ursus m a r i t i m u s
was encoun-
Food intake
t e r e d t w i c e , at s t a t i o n s 68 a n d 303. A t h i r d i n d i v i d u a l , n o t i c e d at s t a t i o n 189 o u t o f t h e c o u n t i n g p e r i o d , w a s n o t i n c l u d e d in t h e r e s u l t s .
Seabird and marine
mammal
c o u n t s a r e ex-
p r e s s e d as n u m b e r s p e r c o u n t ( p e r h a l f h o u r ; s e e
65 c
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-
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__
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~
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/
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.
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~
~O ~ t-
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\ 8o°
\ 7s o
70 °
Fig. 10. Map showing the distribution of the Briinnich's Guillemot, Uria lomvia. Four classes: nihil; 1-10; 11-100; 100 birds per hour (see legend fig. 1).
_
i
7s°/
8o°/
0o
65 °
SEABIRDS AND MARINE MAMMALS IN NORWEGIAN AND GREENLAND SEAS
85
2000, 1800, ~1600, 1400,
~ 1200 1000 v
800
<
600
=
400~
OoO
• •
2001 Am
0
00
2 water temperature (°C)
Fig. 11. Numbers of Little Auks, Alle alle, observed per half hour, as a function of the seawater temperature.
Table 1). They are then converted into densities by using a specific conversion factor reflecting at which distance animals could be detected and the average ship's speed in the different geographical zones. The density (numbers/km 2) is then translated into daily food ingestion by the equation I = 0,191.W 0"723"N
(1)
where I is the ingestion in kg fresh weight/km 2 day, W the individual biomass in kg and N the density in numbers per km 2. This equation is derived (Schneider et al., 1987) from the allometric formula of Lasiewski and Dawson (1967) for the standard metabolic rate (SMR), a conversion factor of 2.8 SMR for calculation of the daily food requirement (Kooyman et al., 1982) and conversion factors of 1.33 for a 75% assimilation efficiency and of 6.37 k J / g fresh weight. The equation was established for seabirds, but the equivalent allometric relation for mammals (Q = 70.W 0"7325, kcal/day)was considered similar enough to apply the same equation (1) to all homeotherms. Other equations such as food requirement = 4% of W/day, or the daily requirements already calculated for minke and fin whales (Lockyer, 1981) also provide values of the same order of magnitude.
The calculated food intake (Tables 2 and 3) by seabirds represents about 2.2 kg fw/km 2 day, with a higher value (2.5) for Atlantic water, intermediate at the ice edge (2.9) and lower in the pack and Polar water (1.9 and 1.7). The role of cetaceans was clearly smaller, with a mean value of 0.2 kg/km 2 day and a maximum of 0.7 in Atlantic water. This conclusion, however, depends on low numbers of individuals with an important biomass and therefore represents only a very rough evaluation. The food intake by pinnipeds was 0.2 kg/km 2 day; they were mainly harp and hooded seals at the ice edge, and hooded and ringed seals on the pack ice. The June 1988 results are of the same order of magnitude as the data obtained in the same region in July 1988; the main differences, as already discussed about the numbers (Table 3), being the presence of alcids in clearly higher numbers in June than in July. As a consequence, the comparison between Antarctic and Arctic ecosystems (Joiris and Tahon, 1991) also remains valid.
Acknowledgements I am very grateful to the Alfred Wegener Institute for Polar Research (Bremerhaven) and
86
c.R. JOIRIS
TABLE 3 Synopsis of the main results obtained in the Norwegian and Greenland seas in June and July 1988 (numbers per 1/2 hour; food ingestion in kg fresh weight/kmZ.day)
species
zone atlantic water
polar water
ice edge
pack ice
mean
A. Numbers June 1988 Fulmarus glacialis (dark) Fulmarus glacialis (light) Pdgophila eburnea Rissa tridactyla * Uria aalge Uria lomvia Alle alle birds * cetaceans pinnipeds
0.6 27.1 0.0 20.3 7.1 0.6 0.3 80.5 0.29 0.00
6.1 6.9 0.0 9.0 1.0 10.0 25.6 60.3 0.00 0.01
4.4 4.8 0.6 3.4 0.0 18.9 82.3 115.2 0.04 4.37
2.5 3.9 1.8 0.9 0.0 0.6 21.1 31.6 0.00 1.39
3.4 10.7 0.6 8.4 2.0 7.5 32.3 71.9 0.08 1.44
Numbers July 1988 (**) Fulmarus glacialis (dark) Fulmarus glacialis (light) * Pagophila eburnea Rissa tridactyla * Uria aalge Uria lornvia Alle alle birds * cetaceans E pinnipeds
1.4 23.2 0.0 3.2 0.8 0.7 0.0 32.6 0.10 0.00
1.0 20.8 0.0 5.2 0.6 10.3 1.2 39.6 0.07 0.04
3.7 3.1 0.0 1.5 0.0 1.8 3.5 14.2 0.07 12.13
2.1 2.0 0.6 0.3 0.0 0.1 1.0 6.4 0.00 0.44
2.1 12.3 0.2 2.6 0.4 3.2 1.4 23.2 0.00 3.13
B. Food intake June 1988 Fulmarus glacialis (dark) Fulmarus glacialis (light) Pagophila eburnea Rissa tridactyla * Uria aalge Uria lomvia Alle alle birds * E cetaceans E pinnipeds Ursus maritimus total
0.02 0.77 0.00 0.40 0.43 0.03 0.00 2.47 0.69 0.00 0.00 3.15
0.19 0.19 0.00 0.18 0.06 0.57 0.46 1,71 0,00 0,00 0,00 1.71
0.14 0.14 0.01 0.07 0.00 1.07 1.46 2.91 0.15 0.55 0.00 3.61
0.22 0.31 0.10 0,05 0.00 0.09 1.04 1.89 0.00 0.40 0.01 2.30
0.14 0.35 0.03 0.17 0.12 0.44 0.74 2.24 0.21 0.24 0.00 2.69
Food intake July 1988 (**) Fulmarus glacialis (dark) Fulmarus glacialis (light) * Pagophila eburnea Rissa tridactyla * Uria aalge Uria loravia Alle alle E birds * ~, cetaceans pinnipeds Ursus maritimus total *
0.06 0.94 0.00 0.09 0.06 0.05 0.00 1.40 0.67 0.00 0.00 2.07
0.04 0.84 0.00 0.14 0.05 0.82 0.03 0.95 0.34 0.01 0.00 1.30
0.20 0.15 0.00 0.05 0.00 0.18 0.11 0.73 0.19 2.36 0.00 3.28
0.11 0.10 0.02 0.01 0.00 0.01 0.03 0.28 0.00 0.12 0.00 0.40
0.10 0.51 0.01 0.07 0.03 0.27 0.04 1.09 0.30 0.62 0.00 2.01
* Without taking into account an important concentration of Fulmars and Kittiwakes off Iceland (see text). ** Joiris and Tahon, 1991.
65c
=
-
10o W
i~ ~ ' .
---------..__I__ 0 o
"iI ~
,_/,
0o
i00
÷
-V
J
80°
75 o
70 °
~,~0o65 ?.o
Fig. 12. Map showing the distribution of the Little Auk, Alle alle. Three classes: nihil; 1-5; 6-25; 26-125 birds per hour (see legend Fig. 1).
70 °
75 c
80°
I00
oo
"~
88
C.R. JOIRIS
30. 25. 20.
& 15. 10. 5,
• 00
-2
0000
o
;,
1'o
water temperature (°C)
Fig. 13. Numbers of ringed seals. Phoca hipida, observed per half hour, as a function of seawater temperature.
the chief scientist J. Meincke for the invitation on board RV Polarstern. Other costs were funded by the Belgian National Science Foundation (NFWO). References Anonymous, 1990. Report of the working group on harp and hooded seals. ICES. C.M. 1990/Assess: 8.25 pps. Bourne, W.R.P., 1982. The manner in which wind drift leads to seabird movements along the east coast of Scotland. Ibis, 124: 81-88. Brown, R.G.B., 1984. Seabirds in the Greenland, Barents and Norwegian Seas, February-April 1982. Polar Res., 2: 1-18. Burnham, K.P., Anderson, D.R. and Laake, JL. 1980. Estimation of density from line transect sampling of biological populations. Wildl. Monogr., 72. Byrkjedal, I., Alendal, E. and Lindberg, O.F. 1974. Counts of sea-birds between Norway and Spitsbergen in the summer 1973. Nor. Polarinst. Arbok, 1974: 265-269. Crossin, R.S., 1974. The storm petrels (Hydrobatidae). In: W.B. King (Editor), Pelagic studies of seabirds in the central and eastern North Pacific Ocean. Smithsonian Contrib. Zool, 158: 154-205. Croxall, J.P., Evans, P.G.H. and Schreiber, R.W. (Editors) 1984. Status and conservaton of the world's seabirds. ICBP tech. publ. No. 2, 778 pp. Diamond, A.W., Gaston, A.J. and Brown, R.G.B. 1986. Converting P1ROP counts of seabirds at sea to absolute densities. Can. Wildl. Serv, Prog. Notes, No. 164, 21 pp. Joiris, C., 1978. Seabirds recorded in the northern North Sea in July: the ecological implications of their distribution. Gerfaut, 68: 419-440. Joiris, C., Billen, G., Lancelot, C., Daro, M.H., Mommaerts, J.P., Bertels, A., Bossicart, M., Nijs, J. and Hecq, J.H., 1982. A budget of carbon cycling in the Belgian coastal zone: relative roles of zooplankton, bacterioplankton and
benthos in the utilization of primary production. Neth. J.Sea Res., 16: 260-275. Joiris, C. and Tahon, J., 1987. Distribution of seabirds and cetaceans in the N.E. Atlantic and Arctic oceans. Eur. Cetacean Soc. 1987, pp. 28-29. Joiris, C.R., 1989. Seabirds in the North Sea: distribution and ecological role. ICES, CM. 1989/N:8. 7 pp. Joiris, C.R., 1991. Spring distribution of seabirds and marine mammals in the Weddell Sea, Antarctica. Polar Biol., in press. Joiris, C.R. and Tahon, J., 1991. Distribution and ecological role of seabirds and marine mammals in the Norwegian and Greenland seas (July 1988). Acad. R. Sci. Outre-Mer., in press. Kooyman, G.L., Davis, R.W., CroxaU, J.P. and Costa, D.P., 1982. Diving depths and energy requirements of King Penguins. Science, 217: 726-727. Lasiewski, R.C. and Dawson, W.R., 1967. A re-examination of the relation between standard metabolic rate and body weight in birds. Condor, 69: 13-23. Lockyer, C., 1981. Growth and energy budgets of large baleen whales from the southern hemisphere. In: Mammals in the seas, FAO Fisheries Series, Rome 5, vol. 3: 379-487. Melhum, F., 1989. Summer distribution of seabirds in northern Greenland and Barents Seas. Nor. Polarinst. Spr., 191, 56 pp. Meltofte, H., 1972. Ornithological observations in the Norwegian Sea, the Greenland Sea and NE Greenland, JulyAugust 1972. Dansk Ornithol. Foren. Tidsskr, 66: 108-112. Nettleship, D.N. and Birkhead, T.R. 1985. The Atlantic Alcidae. Academic Press, London, 574 pp. Ridgway, S.H. and Harrison R.J. (Editors), 1981. Handbook of Marine Mammals, vols. 1 & 2. Academic Press, London. 235 and 359 pp. Ridgway, S.H. and Harrison, R.J. (Editors), 1985. Handbook of Marine Mammals vol. 3. Academic Press, London, 362 PP. Ridgway, S.H. and Harrison R.J. (Editors), 1989. Handbook
SEABIRDS A ND M A R I N E MAMMALS IN N O R W E G I A N AND G R E E N L A N D SEAS
of Marine Mammals, vol. 4. Academic Press, London, 442 PP. Schneider, D.C., Hunt Jr. G.L and Powers, K.D., 1987. Energy flux to pelagic birds: Bering Sea and Nortwest Atlantic. In: J.P. Croxall (Editors), Seabirds: Feeding Ecology and Role in Marine Ecosystems. Cambridge University Press, pp. 259-277.
89
Wiens, J.A., Heinemann, D. and Hoffman, W., 1978. Community structure, distribution and inter-relationships of marine birds in the Gulf of Alaska. Final rep. Principal lnvestig., vol. 3. Boulder, Colorado, NOAA.