Ice-related Strandings of Killer Whales at Shore in the Southern Okhotsk Sea

Abstract

Killer whales are extensively distributed throughout the world’s oceans and migrate to areas where there is seasonal and year-round sea ice. Even at the southern tip of the Okhotsk Sea, the lowest latitudes where the offshore formation sea ice exists, killer whales are commonly observed during the winter months. At least eight ice-related strandings at the shore of killer whales occurred in Etorofu Island, Hokkaido, and southern Sakhalin between 1925 and 2016. These strandings were observed roughly once per decade. All stranding events occurred with drift ice floe, and not in fast ice. The thickness and density of sea ice floes were different among the events, e.g., from a primary ice floe to a separated front mass or small ice floe fragment in geologi- cal scale or from a large ice cake to brash ice debris. Until the 1970s, the response of the locals was food consumption of whale meat; however, rescue efforts were attempted for three cases in the 21st century. Introduction