NEAR-VESSEL SEABIRD AGGREGATIONS IN THE WINTER TRAWL FISHERY OF POLLOCK IN THE OKHOTSK SEA

Abstract

At least 12 seabird species aggregated permanently around the vessels of pollock trawl fishery in the Okhotsk Sea in January-April, 2015. They were attracted by the fish processing waste and small-sized fish falling from trawls. Fulmars dominated in all fishery districts except the East-Sakhalin subzone (their number was 68.9 % of all birds, on average), they were the most abundant at southwestern Kamchatka. The secondary abundant group of species was large-sized white-headed gulls of Larus genus (31.0 %), mostly slaty-backed gull. Species composition of aggregations and number of the birds were quite dynamic in space and time, but the largest and the most diverse aggregations were observed in the Kamchatka-Kuril fishery district where many seabirds wintered in the Pacific waters. The largest aggregation in this subzone had up to 23,000 ind. around one separate vessel, so hundreds of thousands birds may gather in the area of a trawling fleet operation. Size and species composition of the near-vessel aggregations are determined by biotopic preferences of the species and weather conditions. The pollock trawl fishery is regarded as a powerful factor of the seabirds habitat in the Okhotsk Sea, and the catching and processing waste is a reliable food base for huge bird community, particularly important in winter season.