Seasonal acoustic presence of fin and bowhead whales in relation to prey abundance and oceanographic environments in the southern Chukchi Sea

Abstract

To assess how seasonal and ice-associated whales differently respond to the Arctic climate changes, understanding the relationships among their presence and environmental conditions is necessary. We examined the seasonal acoustic presence of fin Balaenoptera physalus and bowhead whales Balaena mysticetus in relation to prey abundance and oceanographic conditions in the southern Chukchi Sea from July 2012 to July 2014 using passive and active acoustic methods. Oceanographic conditions obtained were water temperature, salinity and sea ice concentrations. Fin whale calls were detected from summer to fall, only in ice-free and high prey abundance period. Moreover, the call-detected period was longer in 2013 than 2012. In contrast, bowhead whale calls were mainly detected from fall to winter and in spring, during ice-free and ice-covered periods. The call presence of bowhead whales overlapped less frequently with that of fin whales in fall 2013 than 2012. The reason for the differences in their acoustic presence between these two years may be caused by higher water temperature and late sea-ice formation in 2013 compared to those in 2012. These results suggest that annual variations in the oceanographic conditions possibly affect the distribution of both species in the southern Chukchi Sea.