Marine Mammal Acoustic monitoring and habitat investigation, Southern California offshore region

Abstract

The echolocation clicks of five dolphin species found off southern California are described and the use of clicks for species classification is investigated. Spectral and temporal properties are analyzed for the echolocation clicks from short-beaked common, long-beaked common, Risso's, Pacific white-sided and bottlenose dolphins. Two of the species exhibit unique spectral peaks and notches when the complete click is analyzed. A nested ANOVA analysis indicates that spectral peaks and notches occurring between 24 and 35 kHz are distinct between the two species and exhibit low variation within each species. Also, two subgroups are distinguished within Pacific white sided dolphin recordings, possibly representing two overlapping populations in the region. Bottlenose and common dolphin clicks do not exhibit consistent patterns of spectral peaks or notches. Visual and acoustic line-transect surveys during four CalCOFI cruises (July 2006 -- April 2007) were conducted to understand cetacean ecology and habitat. The most commonly sighted mysticetes were blue, fin, gray and sperm whales;most commonly sighted odontocetes were short-beaked common dolphins and Dall's porpoise. By integrating CalCOFI environmental and cetacean data, ecological models for cetacean habitat in the region off southern California can be developed to improve predictive models for their presence in the SCORE range.