Table 2.— Size offish and frequency of occurrence of fishes and cephalopods found in the stomachs of Pacific white-sided dolphin , Dall's 

 porpoise, and northern fur seal' collected off California and Washington, 1964-72. 



3142 



3 



Squid. Abraliopsis sp.^ 



Squid. Octopoleuthis sp.^'^ 



Squid. Gonatidae 



Squid. Gonatus sp. 



Squid. Gonatopsis borealis^ 



Squid, Onychoteuthis borealijaponicus^ 



Squid, Chiroteuthis sp.^ 



Squid, Cranchiidae^ 



Pelagic octopus, Ocythoe tuberculata^ 



'A complete list of prey species of the northern fur seal appears in North Pacific Fur Seal Commission Reports on Investigations, 1962, 1969, 1971, 1975. 



^Length measurement of Chinook salmon and sablefish is standard length, other measurements are total length. The numbers in parentheses indicate sample size. 



^Northern fur seal in association with Pacific white-sided dolphin. 



"Northern fur seal in association with Dall's porpoise. 



^Identified for the first time as prey of the Pacific white- sided dolphin. 



'Identified for the first time as prey of the Dal! s porpoise 



11 



9 



11 



11 



2 



11 



3 

 3 



squid beaks, bone fragments, and otoliths, which 

 were found in the fundic (or pyloric) stomach and 

 the duodenal ampulla, all undigested or 

 semidigested food items were found in the fore- 

 stomach. Stomach volumes were highly variable 

 depending on the time of day the animal was col- 

 lected and the digestibility of the species offish or 

 squid ingested. Of 30 dolphin taken off California, 

 those taken before 1000 h averaged more than 

 twice the volume of food in their stomachs than 

 those taken after 1000 h. 



During the course of pelagic fur seal research, 

 thousands of seal stomachs have been examined 

 by the authors. The stomach containing the most 

 food was from a 17-yr-old male collected in the 

 eastern Bering Sea at 1330 h, 9 August 1968. The 

 animal had consumed 13 walleye pollock, 

 Theragra chalcogramma, and 4 squid, Ber- 

 ryteuthis magister. The contents weighed 9.8 kg 

 (9,175 cm^ volume representing 7.2% of body 



weight) with walleye pollock composing 80% 

 (7,340 cm^) of the total stomach volume. The 

 stomach of an adult female fur seal contained food 

 weighing 5.9 kg (5,565 cm^ volume representing 

 13.1% of body weight). This 15-yr-old animal was 

 collected at 0645 h on 19 April 1964 off California 

 and had fed on 31 Pacific whiting. 



The energy requirements of the northern fur 

 seal are poorly knowoi. Keyes (1968) reported that 

 seal and other pinnipeds kept in captivity sub- 

 sisted well on 6-12% of body weight daily, with 

 vitamin supplements. Studies indicate possibly 

 higher daily consumption rates among growing 

 immature animals. Sergeant (1969) summarized 

 the feeding rates per day of several captive ceta- 

 ceans including two dolphin which consumed 7.9% 

 of their body weight in herring and mackerel and a 

 porpoise that consumed 11.3% of its body weight of 

 mackerel. Ridgway (1972) reported food require- 

 ments in captive animals equalled 7-8% of body 



956 



