Eleventh Global Studies Conference

Abstract

This project shows the utility of using opportunistic small-boat, based dual-frequency (50, 200 kHz) digitally-recorded commercial hydro-acoustics to examine blue (Balaenoptera musculus), humpback (Megaptera novaeangliae), and gray (Eschrichtius robustus) whale diving behavior in relation to prey. Data were gathered opportunistically during sighting, photo-ID, and tagging surveys done from a 5.9 m boat from June to October 2010-2015 in the Eastern North Pacific. A total of seventy-two cases (on forty-four different days) were identified with apparent whale tracks visible on the records (most clearly on the fifty kHz) and in sixty-six of these cases (92%) we could identify apparent prey patches on either or both the fifty and 200 kHz. In two instances whale tracks matched well to dive records from archival tags attached to one of the whales in the sighting. While past work has been done on whale diving and feeding behavior from observations and tags coupled with prey data quantified with research-grade echo-sounders, this has rarely been studied using a small commercial system to simultaneously detect whale and prey behavior from a small platform. This opportunistic approach yielded insightful differences of whale behavior in relation to prey.