Abstract:
NOAA's Pacific Marine Environmental Laboratory (PMEL) has been monitoring U.S. Navy SOund SUrveillance System (SOSUS) data from the northeast Pacific since 1991. Beginning in May 1995, additional hydrophone arrays were made available to PMEL for the study of underwater earthquakes, volcanoes, and whale acoustics. The addition of these data has made it possible for monitoring of low-frequency (60 Hz) whale calls over large areas of the north Pacific. Thirteen arrays in the north Pacific were grouped into five subregions: nearshore NE Pacific, offshore NE Pacific, central Aleutians, western Aleutians, and northwestern Pacific. SOSUS data were examined for the presence or absence of four different call types, two each from presumed blue (Balaenoptera musculus) and fin (B. Physalus) whales. The blue whale call types included the A--B pair [Thompson et al., Mar. Mamm. Sci. 12, 288--292 (1996)] and the two-part call described by Thompson and Friedl [Cetology 45, 1--19 (1982)]. Fin whale calls were divided into two groups based on the pattern and frequency content of the call series. Seasonal and geographic variation were found for all four call types.