New technical report on marine mammal distribution in Southern California

Posted on February 20, 2015

Distribution and Demographics of Marine Mammals in SOCAL  through Photo-Identification, Genetics and Satellite Telemetry

Authors: Erin A. Falcone and Gregory S. Schorr

Abstract: This report summarizes data collected during small-vessel surveys for cetaceans in the Southern California Bight (SCB), with a focus on the Southern California Offshore Range Complex (SCORE), from June 2010-January 2014. Detailed annual progress reports were prepared after each survey year through 2013 and are available online through the Naval Postgraduate School. This final report emphasizes analyses that combine data across study years, particularly with respect to two focal species: Cuvier's beaked (Ziphius cavirostris, Zc) and fin (Balaenoptera physalus, Bp) whales. 18 cetacean species were encountered in surveys based at SCORE, and several previously documented seasonal trends in species occurrence were confirmed. Bp were sighted in every month surveyed, Zc in all but one, suggesting both are present year-round. Preliminary mark-recapture abundance estimates from photo-identification data suggest both species have local populations in the low hundreds. Both photo-identification and telemetry data suggest Zc exhibit a degree of basin-specific site fidelity within the SCB. Many Bp also appear to preferentially remain within the SCB year-round, with increased use of nearshore waters in fall and winter. A subset of 688 hours of Zc diving behavior from periods without Mid-Frequency Active Sonar use in the area showed that the behavior of these whales was similar to that of the larger dataset (including sonar exposure), and confirms previous observations that Zc here appear to forage less often than whales in other regions, and that sonar exposure is unlikely to be the primary driver of these regional differences, though some exposures may cause foraging disruption. Future research will seek to further elucidate the relationship between behavioral patterns and sonar use in the area.

For immediate access to this report, please visit NPS-OC-14-005CR