Diet of Beluga Whales in Alaska from Stomach Contents, March to November

At least five stocks of beluga whales (Delphinapterus leucas), are found in Alaska waters: Beaufort Sea, eastern Chukchi Sea, eastern Bering Sea, Bristol Bay, and Cook Inlet. The two northernmost stocks (Beaufort Sea and eastern Chukchi Sea) are highly migratory; the two southernmost stocks (Bristol Bay and Cook Inlet) are nonmigratory. Little is known about the seasonal movements and distribution of the eastern Bering Sea stock. Beluga populations in Alaska are thought to be stable or increasing, except for the Cook Inlet stock which is listed as endangered under the Endangered Species Act.

We analyzed stomach contents from beluga whales collected between the months of March and November taken in subsistence harvests, from belugas found dead, and from belugas collected for research. We describe prey species and their percent frequency of occurrence as well as potential biases from the seasonality of prey relative to the timing of sampling, and differential feeding and digestion. Diet was highly variable among stocks.

The predominant fish species of the Beaufort Sea stock was Arctic cod, Boreogadus saida, although shrimp and smoothskin octopus, Benthoctopus leioderma were found more frequently. Although the eastern Chukchi Sea stock ate more saffron cod, Eleginus gracilis than Arctic cod, shrimp and echiurids were more prevalent than fish. The eastern Bering Sea stock had the most diverse diet. Dominant fish species included saffron cod, rainbow smelt, Osmerus mordax, several species of sculpin (Family Cottidae) and flatfish (Family Pleuronectidae), and Arctic cod.

Dominant invertebrates included shrimp, with polychaetes, isopods, bivalves, amphipods, and echiurids. Pacific salmon, Oncorhynchus spp., predominated over cod in Bristol Bay and Cook Inlet beluga stocks, and invertebrates appeared to be less prevalent prey. In Bristol Bay, smelt were also eaten more often than cod, while in Cook Inlet cod were eaten more often than smelt. Invertebrates were common in the diet of all Alaska beluga stocks and shrimp (mostly from the family Crangonidae) were the most prevalent.

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Lori T. Quakenbush, Robert S. Suydam, Anna L. Bryan, Lloyd F. Lowry, Kathryn J. Frost, and Barbara A. Mahoney. Published in Marine Fisheries Review 77(1).