Food contents of the eastern gray whale Eschrichtius robustus Lilljeborg, 1861 in the Mechigmensky bay of the Bering Sea

Abstract

Food compositions in 82 individuals of the gray whale Eschrichtius robustus from Mechigmen Bay in the Bering Sea were analyzed in 2007–2009. Animals of 12 taxonomic groups were revealed in the food boluses of whales; amphipods and polychaetes prevailed by biomass and frequency of occurrence. The average specific biomass of amphipods was 54.2–71.7% and the frequency of occurrence reached 96.3–100%; those of polychaetes were 19.5–37.2 and 85.2–100%, respectively. The comparison of the feeding of E. robustus in 2007–2009 and 1998–1999 displayed that the taxonomic composition of the eaten animals remained the same, but the sizes of the groups changed. In 2007–2009, 68 species of amphipods were recorded in the whale stomachs; the input to biomass was counted for six species, Anonyx nugax (31.7%), Ampelisca macrocephala (22.3%), Psammonyx kurilicus (15.3%), Ampelisca eschrichti (9.1%), Hippomedon denticulatus orientalis (4.3%), and Pontoporeia femorata (4.6%). As in 1998–1999, the first two species prevailed. In percentage terms, the greatest portion of the whale bolus was based on most abundant benthic species.