Coastal observations and satellite tracking of migrations of killer whales and belugas in the Sea of Okhotsk in summer-autumn period of 2018

In July-August 2018, coastal observations of marine mammals were conducted at the mouth of the Tyvlinka River (Yekaterina Bay, Sakhalin Gulf) in the Sea of Okhotsk, Khabarovsk region. In total, 40 killer whale encounters were recorded, against 68 killer whale encounters during the same period in 2015. On the coastal strip from the mouth of the Tyvlinka River to Cape Litke there are three rookeries of true seals (largha and lakhtak), with a total number of about 300 individuals. During the period of field observations, two cases of killer whale attacks on seals were recorded. Satellite beacons were installed on three killer whales and on two belugas. These beacons made possible to monitor subsequent migrations of tagged animals during summer-autumn period of 2018. Two killer whales, tagged in the Akademiya Bay and the Konstantin Bay in August, remained in the area of Shantar Archipelago during the salmon run, then in late August - early September they moved to the open waters of the Okhotsk Sea to the area where fishery vessels harvested the demersal fish species. Female killer whale tagged in the Sakhalin Gulf migrated to the northern part of the Okhotsk Sea to the Shelikhova Bay and the Penzhinskaya Bay, and almost repeated in calendar dates and positions the track of another female killer whale that was tagged in the summer 2015. The average speed of killer whales ranged from 4.3 km/h to 8.6 km/h. Belugas are more attached to their habitats in the Sakhalin Gulf. One of tagged belugas remained in the Gulf of Sakhalin, the other passed through the Nevelskoy Strait in October and went into the Sea of Japan. The average speed of beluga whales was two to three times lower than in killer whales and ranged from 1.7 km/h to 2.5 km/h.

killer whale Orcinus orca, beluga whale Delphinus leucas, true seals, abundance, satellite tagging, summer-autumn migrations

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