450 



Fishery Bulletin 104(3) 



son 



70 

 60 

 50 

 40 

 30 



20 



A St. George island 



i\ 



iL 



Gonatid Gb-Bm Gm-Gm Northern Pacific 



group I smoothlongue herring 



Pacific Pacific 



salmon sand lace 



Walleye 

 pollock 



B St. Paul Island 



:_di 



JZL 



Gonatid 

 group I 



Gm-Gm Northern Pacific 



smoothtongue herring 



Prey species 



Pacific Pacific 



salmon sand face 



Walfeye 

 poflock 



Figure 2 



Percent frequency of occurrence (FO'i) of primary prey species (FO^^S^) recovered 

 from northern fur seal iCallorhinus ursinus) scats and spews collected from rookeries 

 on (A) St. George Island and (B) St. Paul Island, Pribilof Islands, Alaska during the 

 breeding season (late July-September), 1990-2000. Gonatid group I includes E. tinro, 

 G. herryi, G. onyx, and G. pyros. 



Overlap between age classes of 

 pollock consumed by northern 

 fur seals and pollock caught by 

 the commercial trawl fishery 



The percent overlap between age classes of walleye pol- 

 lock caught by the commercial trawl fishery and those 

 consumed by northern fur seals varied between sample 

 types for both islands. Minimal overlap was observed 

 between age classes of pollock found in St. George 

 Island and St. Paul Island scats and those taken by 

 the commercial trawl fishery (St. George Island=15.5%; 

 St. Paul Island=4.1%, Fig. 3). However, the percent- 

 age of overlap between age classes of pollock found 

 in St. George Island and St. Paul Island spews and 

 the age classes of pollock taken in commercial trawls 

 was considerable (St. George Island=94.6%; St. Paul 

 Island=89.6%, Fig. 3). 



Discussion 



Northern fur seal diet studies conducted since the 1980s 

 have primarily used scat samples to determine prey spe- 

 cies and size. Despite the presence of spews on rookery 

 and haul-out beaches, only Kiyota et al. (1999) has 

 utilized spews to study northern fur seal diet. Kiyota 

 et al. (1999) examined spews and scats collected from 

 haul-outs (subadult male dominated) and found differ- 

 ences in the prey remains recovered between sample 

 types. We compared the diet of adult female northern 

 fur seals using scats and spews collected from rookeries 

 on the Pribilof Islands over an eleven-year period. We 

 observed differences in the percent frequency of occur- 

 rence (Fig. 2) and the estimated age or size (Figs. 3 and 

 4) of prey between scats and spews. Additionally, the 

 degree of overlap between age classes of walleye pollock 

 consumed by northern fur seals and those caught in 



