Abstract:

The NOAA Southwest Fisheries Science Center conducted a 3-month (8 March--9 June 1997) Sperm Whale Abundance and Population Structure (SWAPS97) cruise to visually and acoustically survey sperm whales in the northeast Pacific. A custom-designed towed hydrophone array system was deployed to detect and determine bearings to sperm whale ``clicks.'' However, this system also proved effective in detecting and recording songs of humpback whales. Additionally, sonobuoys were deployed regularly throughout the cruise to monitor and record baleen whales' sounds. The timing and location of these surveys corresponded well with the northbound migration of humpback whales from known tropical breeding areas to northern latitude feeding areas and resulted in numerous (~130) detections of singing humpback whales. Most of these detections occurred in pelagic waters (i.e., away from breeding areas), indicating that humpback whales sing during their northward migration. Of greater interest were clusters of detections 400--600 miles off the coast of California. It is possible these detections correspond to animals migrating north from the Revillagigedo Islands, Mexico. Data on singing humpback whales collected during the SWAPS97 cruise will be summarized, and implications regarding the biology and management of humpback whale populations will be discussed. [Work supported by NOAA/NMFS and ONR.]