Dietary studies on baleen whales in the North Pacific

Abstract

Nine baleen and 32 toothed whale species are distributed in the North Pacific. It is important to understand their feeding ecology, because cetaceans are top predators in the marine ecosystem and play an important role in the food web. In JARPN surveys (The Japanese Whale Research Program under Special Permit in the North Pacific) from 1994 to 1999, 498 minke whales were caught as samples. And in the JARPN 11 survey of 2000, 40 minke whales and 43 Bryde's whales were sampled in the western North Pacific from May to September of these years. A total of 538 minke whales and 43 Bryde's whales sampled were analyzed their forestomach contents. Sixteen prey species, consisting of 1 copepod, 4 euphausiids, 1 squid and 10 fishes, were identified from the forestomach contents of these minke whales. Four prey species consisting 1 euphausiids and 3 fishes, were identified from Bryde's whales. These results suggest that there are direct and/or indirect competition between minke and Bryde's whales and various types of fisheries to take fishes such as Pacific saury and skipjack tuna in the western North Pacific from spring to autumn.