Temporal and geographic patterns in the occurrence and distribution of minke whale (Balaenoptera acutorostrata) boings in the central and western North Pacific.

Abstract

Minke whales are elusive and difficult to study using visual methods. The source of the “boing” sound was recently linked to North Pacific minke whales, allowing passive acoustics to be used to study this species. The seasonal occurrence of minke whales was examined using data collected at the Station ALOHA Cabled Observatory, an ocean bottom hydrophone 100 km north of Oahu. Preliminary analysis of data collected between February and June 2007 indicates that boings occur during all of these months, peaking in early April. No diurnal variation was evident. Towed hydrophone‐array surveys were conducted in the offshore waters of the islands of Oahu, Kauai and Ni’ihau (February 2005) and off Guam and the Northern Mariana Islands (January–April 2007). Although rarely observed visually, the prevalence of boings detected in these areas indicates that minke whales are common. Distribution patterns from both studies suggest that minke whales prefer deep but not the deepest waters. Boings recorded from Guam and the Northern Mariana Islands appear to be more similar to the “central” boing (which includes the Hawaiian Islands) than the “eastern” boing [which includes those recorded east of 138°W, Rankin and Barlow (2005)]. This has important implications for North Pacific minke whale stock structure.