Table 6. — Seasonal occurrences of principal prey (N^4) of harbor seals from the Kodiak 

 Island area and Prince William Sound. [No. = Occurrences of prey; % = Percentage and 

 95% confidence limits.] 



foraging effort and conserve energy compared 

 with selection of more solitary species (Smith and 

 Gaskin 1974). 



The major differences in prey utilization be- 

 tween Prince William Sound and Kodiak are not 

 readily explainable. However, water depths and 

 topography for the two areas are considerably dif- 

 ferent (U.S. Department of Commerce^). Kodiak 

 waters have considerable shallow shelf area, par- 

 ticularly east and south of the Island, and Prince 

 William Sound generally has a rocky, precipitous 

 coast and deep waters reaching 740 m. These 

 features may influence prey composition, abun- 

 dance, and availability to harbor seals. 



Differential utilization of certain prey by season 

 appeared to be explained by availability in most 

 instances. Salmon occurred in stomachs of seals 

 from both Kodiak and Prince William Sound only 

 during the summer. In both areas salmon are only 

 available in quantity in nearshore waters during 

 this period. The apparent increases during spring 

 in utilization of herring in Prince William Sound 

 and capelin in the Kodiak area probably reflected 

 nearshore distribution associated with spawning 

 in these species (Hart 1973; Jangaard 1974). In the 

 Kodiak area. Pacific sand lance were utilized to 

 a greater extent during fall. No reason is known 

 for this. 



Six of the 10, top-ranked prey; walleye pollock, 

 Pacific herring. Pacific cod, flatfishes, shrimps, 

 and salmon are either currently harvested com- 

 mercially or may be harvested in the near future 

 (North Pacific Fishery Management Council^). Of 



particular interest is the possibility of increased 

 harvests of walleye pollock which was the top- 

 ranked prey of harbor seals accounting for about 

 21% of both total occurrences and volumes of food 

 items. Sergeant (1976) believed that fisheries 

 could compete with natural predators and cause 

 their populations to stabilize at levels well below 

 those existing prior to the fishery. 



Harbor seals are present on the Copper River 

 Delta from May through September. The results of 

 this study and those of Imler and Sarber (1947) 

 indicated that eulachon was the dominant prey 

 from late May to mid-July. Nothing is known 

 about feeding during late summer and fall when 

 eulachon are not present. 



Although specialized feeding on shrimps by 

 newly weaned harbor seal pups was reported by 

 Havinga (1933), Fisher (1952), and Bigg (1973), 

 small fishes were the primary food of young seals 

 <1 yr old collected during this study. 



During this study several sampling problems 

 and prey identification biases became apparent. 

 Distinct geographic and seasonal variations in 

 prey utilization were found to occur and because of 

 this it was difficult to determine if a completely 

 representative sample was obtained. Also, our 

 sampling was restricted to nearshore waters. If a 

 significant amount of feeding took place offshore 

 and availability and composition of potential prey 

 was different there, the results of this study would 

 not be totally representative. In addition, the 

 probability of detecting and identifying various 



^U.S. Department of Commerce, NOAA, Nautical Charts 

 No. 8556 and 16700. 



"North Pacific Fishery Management Council. 1978. Fish- 

 ery management plan for the Gulf of Alaska groundfish fishery 

 during 1978. Unpubl. manuscr, 220 p. North Pacific Fishery 

 Management Council, PO, Box 3136 DT, Anchorage, AK 99510. 



548 



