The Characteristics of the Feeding Aggregation Formed by Humpback Whales, Megaptera novaeangliae (Borowski, 1781), in Senyavin Strait, off the Eastern Chukotka Coast, According to Photo-Identification Data

This study provides the first description of the feeding aggregation recently formed by humpback whales in the Senyavin Strait, off eastern Chukotka. A total of 143 individuals were identified during the two summer and fall seasons of 2017 and 2018. More than half of the whales recorded in the first year were encountered again in the following year. The spatial distribution of feeding whales varied substantially between years, which may be explained by a shift in prey use. The structure of the feeding aggregation remained relatively stable, with a slightly higher number of new animals observed in the 2018 season. The estimated size of the aggregation was from 84 (±1.5) to 90 (±6.4) individuals in 2017 and from 105 (±3.7) to 109 (±6.2) individuals in 2018. A comparison of the whale photographs we took with the catalogues from other feeding grounds yielded matches with individuals recorded from the Chukchi Sea, Gulf of Anadyr, and waters off the Commander Islands and the eastern Aleutian Islands. Among the breeding grounds, matches were found only with catalogues of images collected from the waters off the Hawaiian Islands. Thus, we hypothesize that the feeding aggregation in the Senyavin Strait is relatively stable between seasons and within one season. There is some exchange of individuals with some other feeding grounds. This aggregation is formed mainly by whales of the Hawaiian subpopulation.