Passive Acoustic Monitoring for Marine Mammals in the SOCAL Range Complex March 2017 – July 2018

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Passive acoustic monitoring was conducted in the Navy’s Southern California Range Complex from March 2017 to July 2018 to detect marine mammal and anthropogenic sounds. High-frequency Acoustic Recording Packages (HARPs) recorded sounds between 10 Hz and 100 kHz at three locations: northwest of San Clemente Island (1,300 m depth, site E), west of San Clemente Island (1,000 m depth, site H), and southwest of San Clemente Island (1,200 m depth, site N). In addition, an array of 9 HARPs, sampling at 20 kHz, was deployed in the San Diego Trough during the fall of 2017 to track baleen whale calls. One HARP from this array was analyzed for this report (1,051 m depth, site HP). While a typical southern California marine mammal assemblage is consistently detected in these recordings (Hildebrand et al., 2012), only a select sub-set of species including blue whales, fin whales, and beaked whales were analyzed for this report. The low-frequency ambient soundscape and the presence of Mid-Frequency Active (MFA) sonar and explosions were also analyzed.