principal occurrences of this fish in fur seal stomachs were 

 from an area south and west of St. George Island near the 

 shelf edge and north of St. Paul Island. One fur seal collected 

 at lat. 58°03 'N, long. 169°47 'W on 24 August 1963 contained 

 500 individual juveniles of this species while another seal col- 

 lected in the same general vicinity (lat. 58°03'N, long. 

 169°50'W) contained 98 individuals indicating the possibility 

 that this area is a nursery ground for this species. The size of 

 these fish ranged in length from 45 to 60 mm (tip of snout to 

 end of hypural plate) for 14 specimens. 



Among the 20 most common fish species in the eastern Ber- 

 ing Sea (based on research trawl surveys), Greenland turbot 

 ranked second in frequency of occurrence. This fish occurred 

 in 78% of the stations fished in 1975 (Pereyra et al. footnote 

 13). In ichthyoplankton surveys the larvae of this species was 

 the third most abundant flatfish larvae caught. The larvae 

 were large, ranging in length from 16 to 22 mm and were pri- 

 marily taken from the Aleutian Islands northwestward to 

 north of St. George Island (Waldron and Vinter footnote 14). 



In the eastern Bering Sea, adult Greenland turbot are con- 

 sidered deepwater flounders that mainly occupy continental 

 slope waters whereas juveniles generally occupy the shelf area. 

 Bakkala et al. (1979) reported that the highest trawl survey 

 catches for this species occurred northwest of the Pribilof 

 Islands. 



The Greenland turbot is an amphiboreal species occurring in 

 the North Atlantic and North Pacific Oceans. In the North 

 Pacific Ocean, adults generally occur primarily in the northern 

 portion of the species' range, in deep waters of the Pacific 

 Ocean from Baja California, Mexico, to Honshu Island, 

 Japan, through the Okhotsk and Bering Seas (Hubbs and Wili- 

 movsky 1964; Hart 1973). Relatively few adults have been 

 taken by trawl fisheries in the warmer portions of its range. 



DISCUSSION AND SUMMARY 



Although northern fur seals feed on a variety of fishes and 

 squids throughout their range, evidence presented on the 

 abundance and distribution of the principal prey species sug- 

 gests that fur seals are opportunistic feeders preying on the 

 most available species in the area. The principal prey species 

 for this study were selected based on the percentage of total 

 stomach content volume (fourth largest) by month for each of 

 the seven collection areas. 



In examining the variety of prey consumed by fur seals through- 

 out the eastern Pacific range, about 53 species of fish and 10 

 species of squid have been identified from the stomachs of fur 

 seals. From this total, about 14 species of fish and 6 species of 

 squid are considered the principal prey of fur seals. The list of 

 principal prey species of fur seals in each of these areas, as 

 based on percentage of total stomach content volume, gener- 

 ally does not change over time even though the ranking by vol- 

 ume within this list may change. Some species are important in 

 more than one area. Some are fished commercially while 

 others are not of commercial importance but are important 

 forage food for many other predators including fishes, sea- 

 birds, and other marine mammals. 



The predominance of single food items in the stomachs of 

 fur seals may reflect the availability and abundance of fish- 

 squid species more than it reflects the selection or preference 

 of one particular species over another. It is obvious that the 

 prey that fur seals are observed to eat is selected from a larger 



group of species based on size. Some selection may also occur 

 on the basis of factors such as taste and texture; however, 

 these factors can only be studied through experimentation. 

 The important point is that within the set of species known to 

 occur in the fur seal diet the available evidence points to op- 

 portunistic feeding. 



Location is also important in considering diet of fur seals, as 

 prey species generally differ in abundance from area to area 

 (north-south; inshore-offshore) and seasonally. The migratory 

 patterns of forage species must also be considered since they 

 may be available to fur seals only at certain times of the year. 

 For example, off Washington, Pacific whiting migrate into the 

 area in the spring and become available to fur seals. Generally 

 speaking, the migration of fur seals is probably not influenced 

 by the movement of migratory fishes on which they feed al- 

 though the evolution of fur seal migration may have resulted 

 from preference to feed upon selected prey species. There is no 

 documentation concerning this subject. Taylor et al. (1955) 

 and NPFSC reports (North Pacific Fur Seal Commission 1962, 

 1969, 1971, 1975, 1980) have shown that a small percentage of 

 Pribilof Island fur seals intermingle with Asian seals, an indi- 

 cation that food is probably not a major factor in the migra- 

 tion of fur seals. Local movement and distribution is probably 

 simply a result of the abundance of the forage species in the 

 area. Fur seals move to and feed in areas where food is abun- 

 dant and depart in search of other areas of concentrated prey 

 when it becomes scarce. 



Northern fur seals occupy the subarctic waters of the North 

 Pacific Ocean southward to the California-Mexican border 

 (lat. 32°N) in the eastern Pacific and to about the middle of 

 Honshu Island (lat. 36°N), Japan, in the western Pacific. In 

 the eastern Pacific, the Pribilof Island population (the major 

 breeding islands) numbers about 1.3 million animals or nearly 

 80% of the world population of this species. The U.S.S.R. 

 controls the breeding islands used by the remaining fur seals 

 (population of about 485,000) in the western Pacific. 



The eastern Pacific populations of northern fur seals are 

 found throughout their range from California to the Bering 

 Sea in nearly all months of the year with few exceptions and 

 with peak abundance varying by time and area. Most of the 

 Pribilof Island fur seals spend about half the year at sea 

 (November through May-June) and the remainder on and 

 around the islands during the breeding season. Fur seals are 

 most frequently seen in greatest numbers along the continental 

 shelf and slope throughout their range primarily because of 

 abundant food resources in this area. Fur seals feed on a vari- 

 ety of fishes and squids throughout their range and as a gen- 

 eral rule, smaller schooling fishes are usually the principal for- 

 age species over the continental shelf region and oceanic squids 

 are important over deepwater areas seaward of the continental 

 shelf and slope. 



Fur seals feed primarily at night, perhaps due to the fact that 

 many forage species rise toward the surface after dark and 

 become readily available to fur seals which feed primarily in 

 the epipelagic and mesopelagic zones. In the majority of fur 

 seal stomachs examined, the total volume of food in stomachs 

 is generally highest in fur seals collected soon after daylight, 

 generally diminishes by mid-afternoon and increases again 

 towards dusk as the seals resume their feeding activities. Fur 

 seals usually swallow the smaller prey whole below the surface 

 and bring the larger prey to the surface where they first break 

 them into smaller pieces. 



31 



