UC San Diego

The oceanographic conditions that define the Southern California Bight (SCB) dictate the distribution of prey resources and therefore the presence of mobile predators, such as Cuvier’s beaked whales (Ziphius cavirostris). Cuvier’s beaked whales are deep-diving odontocetes that spend a majority of their time foraging near the sea floor. Due to their cryptic behavior, little is known about how they respond to seasonal and interannual changes in their environment. This study utilizes passive acoustic data recorded from two sites within the SCB to explore the oceanographic conditions that Cuvier’s beaked whales appear to favor. Utilizing optimum multiparameter analysis, modeled temperature and salinity data are used to identify and quantify these source waters: the Pacific Subarctic Upper Water (PSUW), Pacific Equatorial Water (PEW), and the Eastern North Pacific Central Water (ENPCW). The interannual and seasonal variability in El Niño Southern Oscillation events and the fraction and vertical distribution of these three source waters may explain variability in Cuvier’s beaked whale presence. Mesoscale mixing was also investigated to explain variability in presence on a weekly or biweekly time scale. Cuvier’s beaked whale presence was highest during the winter and spring and decreased during the summer. These seasonal increases occurred at times of increased fractions of PEW in the undercurrent and decreased fractions of ENPCW in surface waters. On an interannual scale, years of increased presence occurred during El Niño events. These results establish a baseline understanding of the oceanographic characteristics that correlate with Cuvier’s beaked whale presence in the SCB. Furthering our knowledge of this elusive species is key to understanding how anthropogenic activities impact Cuvier’s beaked whales.