OOS 42-2 - Harnessing passive acoustic monitoring to describe spatiotemporal distribution of toothed whales in the northern California Current

Odontocetes play an important ecological role as apex predators within the California Current System (CCS), a cold water current spanning approximately 30° of latitude, from British Columbia, Canada, to Baja California, Mexico. The CCS is characterized by high rates of upwelling and biological productivity, providing rich foraging conditions for several odontocete species, including representatives from the dolphin and beaked whale families, and sperm whales. The northern CCS is uniquely situated near additional nutrient inputs, such as the Juan de Fuca eddy and freshwater plumes from the Columbia River. These multiple sources combine to feed a constant nutrient supply, sustaining long-term blooms and maintaining the northern CCS as a favorable ecosystem for odontocetes.

Newport, Oregon, is located adjacent to both the Juan de Fuca eddy and the Columbia River outlet, and is the seat of Oregon State University’s marine laboratories. There have been few long-term, systematic studies of odontocetes in Oregon waters, with existing data largely being one-off, opportunistic records. The Holistic Assessment of Living marine organisms off Oregon (HALO) Project — a multidisciplinary collaboration between Oregon State University and Cornell University — seeks to address this data gap via quarterly visual surveys and year-round passive acoustic monitoring. Since October 2021, Rockhopper acoustic recording units have been deployed at three sites along the Newport Hydrographic (NH) line, collecting passive acoustic data along a depth gradient spanning the continental shelf (300 m), continental shelf break (730 m), and abyssal plains (2,860 m). These study sites are expected to encompass habitats suitable to all of the odontocete species which inhabit this region, but little is known about how these species make use of these habitats.

Using long-term spectral averages and machine learning methods, such as supervised clustering, across one year of semi-continuous acoustic data (October 2021 to January 2023), odontocete signals will be detected and classified to species (i.e., Cuvier's and Blainville’s beaked whales; sperm whales; Northern right whale dolphins; Pacific white-sided dolphins) and three general groups (i.e., beaked whales; sperm whales; delphinids). Spatiotemporal distribution of odontocete species across the three bathymetric sites will be described on fine temporal scales and related to oceanographic conditions to identify drivers of variability in distribution and activity. These results will expand our knowledge of odontocete ecology and provide insights applicable for ecosystem managers, informing conservation efforts.