Passive Acoustic Monitoring for Marine Mammals in the SOCAL Range Complex April 2020–2021 and Abundance and Density Estimates from CalCOFI Visual Surveys 2004–2021

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Passive acoustic monitoring was conducted in the Navy’s Southern California Range Complex from April 2020 to 2021 to detect marine mammal and anthropogenic sounds. High-frequency Acoustic Recording Packages (HARPs) recorded sounds between 10 Hz and 100 kHz at four locations: two west of San Clemente Island (1,300 m depth, site E and 1,100 m depth, site H) and two southwest of San Clemente Island (1,300 m depth, site N and 1,200 m depth, site U). With the offshore expansion of the SOCAL range, future noise monitoring will be improved by the deployment of a recorder west of San Nicolas Island (site SN). This new site will replace site U, which is located in the Mexican Exclusive Economic Zone where instrument deployment is difficult.