Baleen whale acoustic activity in the North Pacific: historical analysis and current occurrence

• Main Author: Stafford, Kathleen M.
• Other Authors: Oceanography (OC), Naval Postgraduate School (U.S.), Graduate School of Engineering and Applied Science (GSEAS), Office of the Chief of Naval Operations (U.S.), Oceanography
• Format: Report
• Language: unknown
• Published: Monterey, California. Naval Postgraduate School 2007
• Subjects: Gulf of Alaska; Pacific; baleen whale; baleen whales; Alaska
• Online Access: https://hdl.handle.net/10945/699

Unclassified historic acoustic data were used to examine long time scale changes in the seasonal and geographic occurrence of large whales in the Pacific and to correlate these changes with oceanographic variables such as sea surface temperature, chlorophyll a, etc. Distribution of northeastern Pacific blue whales (as indicated by the numbers of their calls), while insignificantly related to SST, did show a clear seasonal pattern both to chl a concentration (negative) and to the mixed layer depth (positive). It was speculated that the negative correlation with chl a might be due to a lag from primary to secondary productivity: as phytoplankton are eaten by zooplankton (which in turn become available to whales), the overall amount of chl a decreases. It is recommended that in collaboration with other agencies hydrophones be deployed in the northeastern Gulf of Alaska to provide current information on the occurrence of vocally active whale species, including low frequency baleen whales and higher frequency odontocetes. A likely time might be during the Northern Edge 2008 exercise in Prince William Sound. Meanwhile, a new efficient, low-power, low-cost recorder that can be easily deployed, in an array with other instruments or independently, from a mid-size vessel is being developed. N00024-02-D-6602.