Seasonal variations in the call presence of bearded seals in relation to sea ice in the southern Chukchi Sea

Abstract

The seasonal habitat use of bearded seals is important information in terms of conservation of this species. However, their distribution outside the breeding season has not been well documented. We investigated seasonal variations in the call occurrence of bearded seals by using passive acoustic monitoring in the southern Chukchi Sea, which has some of the greatest benthic biomass in the Pacific sector of the Arctic Ocean. Underwater sounds were recorded between 2012 and 2015. Calls of bearded seals were detected from mid-September or early October to the end of each recording period (mid-May 2013, early March 2014, and mid-June 2015). Two peaks in call occurrence were noted; the first peak occurred during the open-water periods in November, and the second peak occurred during ice-covered periods. This suggest that bearded seals utilize the southern Chukchi Sea not only for the breeding site but also for the autumn foraging site. We could complement the information about the southward autumn migration pattern of bearded seals, and the southern Chukchi Sea was suggested as the south limit of bearded seals' autumn distribution. Additionally, their vocal activity during autumn in this site was suggested to have some role in social interaction. Our results indicated that the southern Chukchi Sea would be an important monitoring site for understanding the habitat use and the vocal activity of bearded seals, especially outside the breeding season.