Fin whale (Balaenoptera physalus) song pattern in the southern Chukchi Sea

Abstract

The number of migrating fin whales (Balaenoptera physalus) appears to be increasing in the Pacific Arctic after changes in the marine ecosystem and recovering from depletion by commercial whaling. Fin whale songs are sequences of sounds produced repeatedly, and they may be used for population structure assessments. However, little is known about song types and population structures in the Pacific Arctic. We recorded fin whale songs using a fixed passive acoustic monitoring system from July 2012 to June 2015 in the southern Chukchi Sea. We randomly selected one hour of data from each week of the study period and measured the inter-pulse intervals (IPIs) of the songs. Songs were detected from August to November 2012–2014. All songs had a sequence of doublets with two IPIs (10.5 and 19.6 s), and they were similar to previously reported songs of whales from the eastern North Pacific in 2001–2013 but differed from those of whales from the Bering Sea and northeastern Chukchi Sea in 2007–2010. These results suggest that one group of fin whales migrated to the southern Chukchi Sea from the eastern North Pacific in 2012–2014, or the song changed. Comparing songs from different areas of the Pacific Arctic during the same years will reveal whether this group dispersed in this area.