FISHERY BULLETIN: VOL. 84, NO. 4 



tern of migration is known, no estimates have been 

 made of the seasonal abundance of seals by region, 

 and thus total diet cannot be weighted by the sig- 

 nificance of each locality. 



Nonetheless, we are of the opinion that the lack 

 of estimates of local abundance of northern fur seals 

 may not be a major bias in our descriptions of diet 

 for the large coastal regions of the eastern North 

 Pacific (Fig. 10) and the eastern Bering Sea (Fig. 

 11). We reason that the sampling effort in the east- 

 ern North Pacific was extensive from December to 

 June, as indicated by the size of samples collected 

 by month and region (Figs. 4-9; see also Figure 2), 

 and may have largely reflected the seasonal changes 

 in relative abundance of seals during their coastal 

 migration. For the eastern Bering Sea, essentially 

 all samples were taken during July-October, which 

 was the time most seals resided there. 



The most general conclusion to be made about the 

 diet of coastal northern fur seals is that it consists 

 primarily of small schooling fish. Previous studies 

 have made the point that the diet consists of small 

 schooling fish and squid (Spalding 1964; Kajimura 

 1985; others). However, our findings suggest that 

 squid are no more important in the overall diet to 

 the seal than are the larger sized fish. In the coastal 

 regions of the eastern North Pacific the northern 

 fur seal's diet consists of 60% small schooling fish, 

 23% other fish, and 17% squid. When northern fur 

 seals arrive off the coast of southeastern Alaska to 

 California during winter, they feed on northern an- 

 chovy, Pacific herring, capelin, and Pacific saury. 

 When most northern fur seals arrive along the coast 

 of the Gulf of Alaska in spring, they eat capelin and 

 Pacific sand lance. These are fish <30 cm in length 

 (Table 2). Typically they are eaten whole whereas 

 larger fish are first broken into small pieces (Spald- 

 ing 1964). Walleye pollock is the primary food in the 

 eastern Bering Sea. It is a large fish as an adult 

 (Smith 1981), and these fish school. However, north- 

 ern fur seals feed mainly upon the juvenile stages, 

 i.e., <20 cm (McAlister and Perez 7 ). Thus, the diet 

 in this region consists up to 64% small schooling fish, 

 6% other fish, and 30% squid. 



On the Asian coast the diet of northern fur seals 

 also includes small schooling fishes such as mycto- 

 phiform fishes (lanternfishes), Pacific saury, Pacific 

 sand lance, and the Japanese anchovy, Engraulis 



Table 2. — Summary of the size range and general habitat of north- 

 ern fur seal prey. 1 A = anadromous; BC = British Columbia; 

 BER = eastern Bering Sea; CAL = California; GULF = Gulf of 

 Alaska; I = inshore; NS = near surface; O = offshore; ORE = 

 Oregon; S = schooling fish; WASH = Washington; WEST = 

 western Alaska. 



7 McAlister, W. B., and M. A. Perez. 1977. Ecosystem 

 dynamics— birds and marine mammals. Part 1: preliminary esti- 

 mates of pinniped-finfish relationships in the Bering Sea (final 

 report). In Environmental assessment of the Alaskan continen- 

 tal shelf, Annual Report 12, p. 342-371. U.S. Department of Com- 

 merce, Environmental Research Laboratory, Boulder, CO. 



'Data on average lengths of prey and ecology were compiled from Aki- 

 mushkin (1 963), Bakkala et al. (1 981 ), Baxter (1 967), Baxter and Duffy (1 974), 

 Carl (1964), Childress and Nygaard (1973), Childress et al. (1980), Fields 

 (1965), Fitch (1974), Fitch and Lavenberg (1968, 1971, 1975), Hart (1973), 

 lnada(1981), Miller and Lea (1976), Naitoetal. (1977), Niggol (1982), Pearcy 

 (1965), Pearcy et al. (1979), Smith (1981), Taka et al. (1980), and Wespestad 

 and Barton (1981). 



2 Total length for fish and dorsal mantle length for squid. The first number 

 in parentheses is the number of fur seal stomachs examined, and the second 

 number in parentheses is the number of prey specimens measured. These 

 data were derived from an analysis of the original unpublished 1 958-74 data. 



3 Maximum size of salmonids found at sea. Adults in freshwater are larger 

 (to 147 cm) depending upon species. 



4 Does not include size range of Moroteuthis (<140 cm) which has been taken 

 by northern fur seals, but rarely off North America. 



japonicus, in addition to walleye pollock and squid 

 (Taylor et al. 1955; Lander and Kajimura 1980). Of 

 interest is the fact that in recent years the Japanese 

 sardine, Sardinops melanosticta, has become more 

 important in the diet of northern fur seals off Asia 

 (Yoshida et al. 89 ; Yoshida and Baba 1011 ). This sar- 

 dine was depleted during the 1930's and 1940's and 



8 Yoshida, K., N. Okumoto, and N. Baba. 1979. Japanese 

 pelagic investigation on fur seals, 1978. Far Seas Fish. Res. Lab., 

 Shimizu, Jpn., Fur Seal Resour. Sect., Contrib. No. 41-9, 66 p. 



968 



