On the issue of food consumption by Okhotsk Sea killer whales

Abstract

The results are presented on the daily and annual food consumption by killer whales with year-round keeping in net enclosures in Srednyaya Bay. The diet consisted of two species of fish: pink salmon and herring. For females, the daily fish consumption varied from 9 to 50.9 kg with an average of 32.6 kg, for males from 6 to 45.1 kg with an average of 34.1 kg. The annual minimum amount of fish for keeping one young individual in captivity ranges from 11.5 to 12.1 tons of pink salmon, which corresponds to energy requirements of 15.9 Gcal/year for females and 16.7 Gcal/year for males. An increase in the required amount of food for an animal with a decrease in water temperature was established. Based on the results of the factual material on nutrition, the annual consumption of a group of ten killer whales of different ages found in natural conditions was calculated. This value in terms of pink salmon is estimated at 200 tons of feed per year. The theoretical calculation of the annual consumption of various species of aquatic organisms by killer whales is presented. Based on the results of research and analysis of modern literature sources in comparison with historical data on the feeding of killer whales, it was proposed not to divide this species in the Sea of Okhotsk into “mammal-eating” and “fish-eating” ecotypes. In our opinion, the manifestation of different types of behavior (resident type, transit type) in killer whales should be considered, depending on climatic conditions and the availability of food objects. In hunting grounds, the resident type predominates in killer whales, which changes to a transit type of behavior when changing the feeding area or seasonal migration.