Abstract
The National Marine Fisheries Service Southwest Fisheries Science Center (SWFSC) conducted a dedicated acoustic survey for cetaceans throughout the California Current off the U.S. West Coast in August and September 2016. The survey, Passive Acoustics Survey of Cetacean Abundance Levels (PASCAL), was conducted from the NOAA R/V Bell M. Shimada (hereafter Shimada). The Shimada is quieter vessel than the older survey vessels used in previous large scale cetacean and ecosystem assessment surveys allowing for improved acoustic data collection. Focal study species were beaked whales (family Ziphiidae), sperm whales (Physeter macrocephalus), and dwarf and pygmy sperm whales (genus Kogia). These species are difficult to survey visually due to their cryptic behavior. Consequently, population abundance estimates from visual line-transect data, collected during past large-scale cetacean assessment surveys, have poor precision. Mesoplodon beaked whale visual encounter rates have typically been so low during visual surveys that their abundance was assessed as a clade. Following recent advancements in acoustic sensing technology (Griffiths and Barlow 2015; 2016), the primary objective for PASCAL was to conduct a large scale acoustic survey to obtain improved data for estimating population size for these species throughout the California Current study area off the U.S. West Coast.