Top predators strongly impact the structure of ecosystems through the top-down cascading effects on prey species. Killer whales (Orcinus orca), the top predators in marine ecosystems, are increasing their presence in the Arctic following the ice cover loss. The impact of killer whales on marine ecosystems differs dramatically across ecotypes: resident' R-type killer whales feed mostly on large fish, while transient' T-type whales feed mostly on marine mammals. We analyze the differences in geographical distribution of killer whale ecotypes in the western North Pacific in order to predict the potential effects of climate change on their range and the consequential impact on Arctic ecosystems. We show that R-type whales prevail in the coastal waters of eastern Kamchatka, Commander and Kuril Islands and in the central Okhotsk Sea, while T-type whales dominate the coastal waters of Chukotka and the coastal Okhotsk Sea. The most prominent difference between these areas is depth: in the regions where R-type whales prevail, deep waters occur close to shore, while the regions dominated by T-type whales are represented by wide shallows covered with ice in winter. We propose several hypotheses to explain this large-scale segregation, including distribution of prey species and ice cover. Habitat preferences suggest that range expansion in the Arctic induced by climate change will likely involve mostly T-type killer whales and consequently increase the predation pressure on marine mammals to a greater extent than on fish stocks. This should be considered in further studies and prediction models highlighting Arctic marine ecosystems change.
1.Moscow MV Lomonosov State Univ, Fac Biol, Moscow 119234, Russia 2.RAS, Severtsov Inst Ecol & Evolut, Moscow 119071, Russia 3.St Petersburg State Univ, Fac Biol, St Petersburg 199034, Russia 4.Univ Queensland, Sch Vet Sci, Brisbane, Qld, Australia 5.RAS, FEB, Pacific Inst Geog, Kamchatka Branch, Petropavlovsk Kamchatski 683024, Russia 6.Whale & Dolphin Conservat, Bridport DT6 5DD, Dorset, England
Recommended Citation:
Filatova, Olga A.,Shpak, Olga V.,Ivkovich, Tatiana V.,et al. Large-scale habitat segregation of fish-eating and mammal-eating killer whales (Orcinus orca) in the western North Pacific[J]. POLAR BIOLOGY,2019-01-01,42(5):931-941