taken near the Aleutian Islands and Passes, the principal prey 

 appear to be the Atka mackerel and capelin. If seals are taken 

 beyond the shelf over deep water, the forage species will likely 

 be oceanic squids of the family Gonatidae or deepsea smelts of 

 the family Bathylagidae. Fur seals taken over the shelf are 

 likely to be feeding on walleye pollock, Pacific herring, and 

 Greenland turbot. The principal forage species utilized by fur 

 seals in the eastern Bering Sea are shown in Table 3. 



Walleye pollock. — Walleye pollock has been among the 

 leading prey species (Fig. 28) during the 7 yr that fur seals were 

 collected in the eastern Bering Sea (Niggol et al. 1960"; Fiscus 

 et al. 1964, 1965; Fiscus and Kajimura 1965; Marine Mammal 

 Biological Laboratory 1970; Kajimura et al. 1974 16 ; and Kaji- 

 mura and Sanger 1975' 7 ). The walleye pollock occurs as the 

 leading prey species when fur seals are collected on the shelf or 

 near the shelf edge. This fish was also the most frequently 

 eaten prey of fur seals as reported by Lucas (1899). 



Walleye pollock are widely distributed over the continental 

 shelf in the eastern Bering Sea, forming schools near bottom 

 during daylight and then dispersing into the water column at 

 night (Smith 1981). Smith also reported that the seasonal 

 movements of walleye pollock show that the shelf populations 

 retreat to deep water along the outer shelf edge in winter. They 



"Niggol, K., C. H. Fiscus, T. P. O'Brien, and F. Wilke. I960. Pelagic fur seal in- 

 vestigations—Alaska 1960. Unpubl. rep., 60 p. U.S. Fish Wildl. Serv., Mar. Mam- 

 mal Biol. Lab., Seattle, Wash. (Avail. Natl. Mar. Mammal Lab., Northwest and 

 Alaska Fish. Cent., Natl. Mar. Fish. Serv., NOAA, 7600 Sand Point Way NE., 

 Seattle, WA 981 15.) 



"Kajimura, H., G. Sanger, andC. H. Fiscus. 1974. Part 5. Pelagic, Bering Sea. 

 In Marine Mammal Division, Fur seal investigations, 1973, p. 31-47, 71-95. Un- 

 publ. rep. Northwest and Alaska Fish. Cent., Natl. Mar. Fish. Serv., NOAA, 7600 

 Sand Point Way NE., Seattle, WA 981 15. 



"Kajimura, H., and G. Sanger. 1975. Pan 5. Pelagic— Bering Sea. In Marine 

 Mammal Division, Fur seal investigations, 1974, p. 38-54, 102-122. Unpubl. rep. 

 Northwest and Alaska Fish. Cent., Natl. Mar. Fish. Serv., NOAA, 7600 Sand 

 Point Way NE., Seattle, WA 981 15. 



move to the spawning areas along the outer shelf west and 

 northwest of Unimak Island in spring and to the outer and 

 central shelf in summer. In 1973 and 1974 when sampling was 

 limited to an area around the Pribilof Islands, walleye pollock 

 (and gadids which were most likely walleye pollock) were the 

 leading forage species of fur seals, contributing 82 and 86% of 

 the total stomach content volume. Fur seals forage on species 

 other than walleye pollock when taken nearer the Aleutian Is- 

 lands and the Aleutian Passes or beyond the shelf over deep 

 water. 



Walleye pollock is the most important demersal fish popula- 

 tion in the eastern Bering Sea in terms of biomass and landings 

 in the fishery and is the most abundant and most frequently 

 occurring species in the eastern Bering Sea. Its biomass from 

 the 1975 survey was estimated at 2.4 million metric tons (t) or 

 41% of the total fauna available to the trawl gear. Total bio- 

 mass for all species was estimated at 5.9 million t (Pereyra et 

 al. footnote 13). Various estimates of absolute population size 

 of eastern Bering Sea walleye pollock based on research sur- 

 veys, commercial fisheries catch data, and model estimates are 

 shown in Table 1 1 . This semipelagic fish is also the target of 

 the largest single species fishery in the North Pacific Ocean, 

 where the commercial catch peaked at more than 1.8 million t 

 in 1972 and exceeded more than 1.2 million t in 1970 through 

 1976 (Table 12). 



This species has a wide distribution extending from central 

 California northward through the Bering Sea, Sea of Okhotsk, 

 and the Sea of Japan (Hart 1973). Not only is it abundant in 

 the Bering Sea (Fig. 29), it is also reported abundant at times 

 near Kodiak Island. An 80 km long school of spawning walleye 

 pollock (one to several kilometers wide and 75 m deep) was 

 sighted on the west side of Shelikof Strait by the NMFS survey 

 vessel Miller Freeman in mid-March 1980 (Fitzgerald 1980). 



A 1975 NMFS trawl survey of the eastern Bering Sea found 

 fish density highest in the area north of Unimak Island (sub- 

 area 2) of all subareas sampled. The presence of a large bio- 



^ 



t * 



* * * + t 



*****%£. ?T~^~r Pribilof Is. 



f v* 



Bering Sea 





^ 



?+ + 



Figure 28. — Locations where 503 northern fur seals were collected whose stomachs contained walleye pollock, 1958-74. 



22 



