Investigating fine scale frequency characteristics of Northeast Pacific blue whale B calls

Abstract

Passive acoustic monitoring is an effective tool for delineating population structure of blue whales (Balaenoptera musculus). Globally, there are at least nine regionally distinct blue whale songs, with at least two distinct groups within the North Pacific Ocean: the Northeast Pacific (NEP) and central or western Pacific populations. Investigation of the fine-scale frequency characteristics of the NEP blue whale song B unit was conducted from passive acoustic data collected between 2010 and 2013. Data were collected at two low latitude, putative breeding sites at Palmyra Atoll and the Hawaiian Islands and three higher latitude, feeding locations: off southern California, off Washington state, and in the Gulf of Alaska. Frequency measurements were extracted along the entire contour of B calls using a custom feature extraction tool in MATLAB. Data from these two different geographic and life-stage regions were compared to investigate possible fine-scale song separation within the larger region. At least two different variants of B unit were found and their geographic and temporal occurrence will be discussed.