from a milk to a fish diet. Peterson 27 observed 

 that about 50 percent of the females and their 

 young departed from the rookery on the same 

 day, and that 10 percent of the pups left before 

 and 40 percent after the females. C. H. Fiscus 

 examined the stomach contents of two pups 

 collected by E. T. Lyons on 6 October 1961 

 from Polovina Rookery, St. Paul Island. The 

 stomach of a large female pup contained two 

 Pacific sandfish, Trichodon trichodon ; verte- 

 brae from three unidentified fish; one otolith 

 from a walleye pollock. Theragra chalco - 

 grammus; the remains of an invertebrate; 

 shell fragments from a mollusk; a trace of 

 seaweed; and 20 pebbles up to 6 by 10 mm. 

 in size. An acanthocephalan was found in the 

 ileocaecal junction of this animal. The stomach 

 of the other pup contained two gammarid am- 

 phipods. According to Abegglen, Roppel, John- 

 son, and Wilke, 28 the stomach of a male pup 

 taken 13 October 1961 from Polovina Rookery 

 contained about 30 gammarid amphipods and 

 the stomach of another collected on Little 

 Polovina Rookery 27 October 1961 contained 

 smelt (Osmeridae). Since milk was not found 

 in the stomachs examined by Fiscus and by 

 Abegglen et al., these pups had been weaned 

 or were feeding on marine animals between 

 nursings. 



The food of 20 pups (10 each from Zapadni 

 Reef and Northeast Point Rookeries) collected 

 on St. Paul Island 14- 15 November 1966 was 

 identified in the stomach contents and 1-g. 

 fecal samples from the small intestine of each 

 (table 34). The gastrointestinal tracts of nine 

 contained either marine organisms or para- 

 sites transmittable only by fish. The stomach 

 of one animal contained a fish otolith, the ap- 

 parent remains of the intestinal lining of fish 

 were found in four, nine contained milk, and 

 six were empty. Nine of the 20 fecal samples 

 contained marine organisms, indicating that 

 the pups had fed at sea before leaving St. Paul 

 Island (a similar ratio was noted among 

 15 pups collected off the coast of Washington 

 in January and February 1967). Fecal sam- 

 ples from three pups contained ascarids; one 

 sample also contained acanthocephalans. 29 Be- 

 cause ascarids and acanthocephalans require 

 fish as an intermediate host, these three pups 

 had obviously fed on fish. 



The theory that northern fur seal pups change 

 their diet abruptly from milk to fish and feed 



27 See footnote 17. 



2 8 Carl E. Abegglen, Alton Y. Roppel, Ancel M. John- 

 son, and Ford Wilke. 1961. Fur seal investigations, 

 Prlbilof Islands, Alaska. Report of field activities June- 

 November 1961. BCF Marine Mammal Biological Labora- 

 tory, Seattle, Wash., 149 pp. [Processed.] 



2 9 Acanthocephalans identified by M. C. Keyes. 



on fish for the first time upon leaving the 

 rookery islands in autumn has never been 

 investigated. A comparison of fecal material 

 and stomach contents from the same animal 

 has shown that the latter are not completely 

 reliable in establishing whether a pup has or 

 has not begun to feed on fish or squid (field 

 number 110, table 34). A fecal sample nega- 

 tive for marine organisms is also unreliable 

 because food passes through the animal rather 

 quickly. For example, nearly half the pups 

 taken off the coast of Washington in January 

 and February of 1967 had no remains of ma- 

 rine organisms in their stomachs. The stom- 

 achs of 9 of the 20 pups collected on St. Paul 

 Island in November of 1966 contained 62 to 

 1,290 ml. of milk. Pups that are nursing or 

 digesting a large meal of milk probably do not 

 forage. 



It is not possible to judge from this sample 

 of 20 stomachs how important to survival is the 

 feeding by nursing pups on marine organisms. 



RELATION OF FUR SEALS TO 

 COMMERCIAL FISHERIES 



Although the fur seal feeds on a variety of 

 commercially important species of fish and 

 cephalopods throughout its range, its effect on 

 commercially important species is impossible 

 to assess with present knowledge of ocean 

 ecology. 



Fur seals are occasionally caught in drift 

 gill nets used by the Bureau of Commercial 

 Fisheries in research on salmon; however, 

 they seldom damage the nets. Seals have 

 been observed taking salmon out of gill nets 

 (D. Craddock, Fishery Research Biologist, 

 BCF Biological Laboratory, Seattle, personal 

 communication, 28 September 1967). The ex- 

 perience of Japanese high-seas salmonfisher- 

 men is assumed to be similar to that of U.S. 

 research vessels fishing gill nets. 



Salmon have occurred in 6 percent of 1,001 

 stomachs collected off Washington since 1958, 

 and in 1 1 percent of the 570 stomachs con- 

 taining food. Since 1958, 1.5 percent (138) 

 of 9,364 stomachs from all areas contained 

 salmon. 



Damage to fishing gear and stocks of Pacific 

 halibut, Hippoglossus stenolepsis, is almost 

 nil. The damage reported by halibut fishermen 

 has been done by Steller sea lions Eumetopias 

 jubata (£. Best, Fishery Biologist, Inter- 

 national Halibut Commission, Seattle, Wash., 

 personal communication, 28 September 1967). 

 Pacific halibut have been found in only two fur 

 seal stomachs from thousands examined. Hali- 

 but weighing 5 pounds (2.2 kg.) or more (legal 

 size) are plentiful around the Pribilof Islands. 



45 



