The Dynamics of the Community of True Seals (Phocidae) in Piltun Bay, Sakhalin Island, During the Ice-Free Seasons of 1999 and 2014–2016

Abstract

The on-shore haul-out of phocid seals located in the mouth of Piltun Bay (northeastern Sakhalin Island) has been studied and the number of seals on it during the ice-free season was estimated. Currently, it is the largest mixed-species on-shore haul-out on the northeastern Sakhalin coast. In the summer and autumn, three species of ice-bound seals feed in the adjacent waters: the bearded seal, ringed seal, and spotted seal. In 1999 and 2014–2017, the total observation time amounted to 630 days, during which 3361 counts of seals were made. The seasonal dynamics of the number of seals on shore are characterized by three consecutive periods with peak values (June–July, August–September, and October), each coinciding in time with the runs of anadromous fish through the bay mouth. In 1999, the number of seals was statistically significantly different from those recorded in 2014–2017; in 2014, it differed from the value in the season of 2016. In 1999, the median of the total number was significantly lower than in any of the seasons from 2014 to 2017.