A study of common minke and Bryde's whales was conducted in the western North Pacific in the 2000 and 2001 summer seasons to estimate prey selection of cetaceans as this is an important parameter in ecosystem models. Whale sighting and sampling surveys and prey surveys using quantitative echosounder and mid-water trawl were carried out concurrently in the study. Biomasses of Japanese anchovy, walleye pollock and krill, which were major prey species of common minke and Bryde's whales, were estimated using an echosounder. The results suggested that common minke whale showed prey selection for Japanese anchovy while they seemed to avoid krill in both the offshore and coastal regions and walleye pollock in the continental shelf region. Selection for shoaling pelagic fish was similar to that in the eastern North Atlantic. Bryde's whale showed selection for Japanese
The stomach contents of 150 Dall's porpoises collected during 6 surveys in the Sea of Japan and Sea of Okhotsk around Hokkaido in 1988 to 1996 were examined. A total of 49 prey types, including 29 species, were identified. Epipelagic prey items were found in samples collected during midday, and mesopelagic and some benthopelagic prey species were found in samples collected in the morning. Although the size range of prey was great, most prey were small. The dominant prey species switched in both seas from the late 1980s to the early 1990s as the Sardinops melanostictus (Japanese pilchard) populations in the both seas declined. In the Sea of Japan, the diet of Dall's porpoises switched to ~heragra chalcogramma (walleye pollock), and in the Sea of Okhotsk, their diet switched to Engraulis japonicus (Japanese anchovy) and Berryteuthis magister (magistrate armhook squid). The utilization of new prey species did not always coincide with the fluctuation in catch statistics for the prey in local fisheries. Dall's porpoises fed on many benthopelagic prey species when epipelagic prey species were not available, suggesting that epipelagic prey species are the preferred prey. The vertical distribution of prey presumably affects prey selection.
We examined the stomach contents of 26 Baird's beaked whales caught off the coast of Japan by small‐type coastal whalers. The main prey for these whales was rat‐tails and hakes in the western North Pacific. Pollock and squids were also important food in the whales collected from the southern Sea of Okhotsk. The prey species found in the stomachs of the whales were almost identical to those caught in bottom‐trawl nets at depths greater than about 1000 m in the western North Pacific, which suggests that the Baird's beaked whale forages for prey at depths of about 1000 m or more. Baird's beaked whales in the western North Pacific migrate to waters of 1000–3000 m in depth, where demersal fish are abundant. This implies that Baird's beaked whales migrate to waters where demersal fish, especially rat‐tails and hakes, are abundant. Although there is limited information on the feeding habits of ziphiid whales, they are generally thought to prefer squid. The present data suggest that demersal fish are also important prey for ziphiid whales.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.