OREGON STATE UNIVERSITY
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Investigators: Dr. Leigh Torres, Dr. Holger Klinck, Craig Hayslip, Dr. Kim Bernard, Marissa Garcia, Dr. Dawn Barlow, Rachel Kaplan, Will Kennerley
The Holistic Assessment of Living marine resources off Oregon (HALO) project headed out on its first voyage in October 2021 aboard the R/V Pacific Storm. Researchers conducted visual surveys for cetaceans (whales and dolphins) along the Newport Hydrographic (NH) Line and deployed three Rockhopper acoustic recording units to continually collect sound information, listening for cetaceans nearby. The HALO team revisits the NH line on a 24-hour trip once per quarter and repeat the visual survey, recovering and redeploying the acoustic recorders every six months.
The goals of our project are to (a) improve our understanding of the interactions between year-round cetacean occurrence patterns and oceanographic conditions, and (b) assess how changing ocean conditions may impact these patterns and interactions.Since the 1960s, researchers have conducted oceanographic studies in Oregon waters along the NH Line. Despite a strong oceanographic understanding of the area, there is a gap in knowledge of year-round cetacean distribution in Oregon waters. We join the legacy of other researchers who have collected samples, conducted surveys, and developed an oceanographic record of this area.
The Rockhopper is an acoustic recording unit developed by Cornell’s K. Lisa Yang Center for Conservation Bioacoustics (pictured below), used to listen for and record the sounds of marine mammals, which regularly produce species-specific sounds underwater. Cetaceans are known to produce sounds ranging from infrasonic (< 20 Hz; e.g., blue whales) to ultrasonic (>20 kHz; e.g., beaked whales). The Rockhoppers are programmed to record frequencies in the 10 Hz to 150 kHz range, covering the frequency range of all known marine animal sounds. During a typical 6-month deployment, each unit will collect approximately 9 TB of acoustic data!
The HALO project includes three Rockhopper units deployed off Newport, Oregon, along the NH Line: on the continental shelf (20 nm offshore), at the shelf break (45 nm offshore), and on the abyssal plain (65 nm offshore). These deployment locations represent very different environments with different oceanographic conditions.
We conduct visual surveys for cetaceans using standardized distance sampling, which is a common approach to estimate cetacean distribution and density. During our surveys, we record the survey conditions (i.e., wind speed, swell height, rain, fog) as these environmental factors affect our ability to detect cetaceans. We constantly record our trackline using a GPS, travel at a standard speed, and have two observers surveying with binoculars and naked eye for cetaceans. This consistency allows us to record and compare “absence data”, which is just as important as presence data because it tells us where the animals are not. When we make a cetacean sighting, we record the distance and bearing to the sighting, which allows us to calculate the location of the animal, based on the position of the research vessel and the height of the observer above the water. We document the species and group size, and take photos to help with identification efforts.
Simultaneously, a trained observer surveys for seabirds, recording the species, group size, behavior, and flight height of all birds that pass within 300 meters of the research vessel trackline.
We use a 120 kHz split-beam echosounder to map the prey distributions and densities during HALO surveys aboard the R/V. Pacific Storm. So, while we use passive acoustics to listen to whales, we use active acoustics to see their prey. The 120 kHz frequency is optimal for targeting krill, the dominant prey group of many whale species off the Oregon Coast. Krill tend to form dense aggregations that we can identify from active acoustic data. Once we have identified krill aggregations, we can determine their exact locations in three-dimensional space (latitude, longitude, and depth within the water column) and time, and we can match whale presence with prey presence.
Beyond that, the active acoustics can also tell us what depth the prey are at and even the shape and density of their aggregations. From there, we can start to identify the types of prey aggregation formations that different whale species target.
Blogs:
Collaborators:
K. Lisa Yang Center for Conservation Bioacoustics, Cornell University
Zooplankton Ecology Lab, Oregon State University
Seabird Oceanography Lab, Oregon State University
Whale Habitat, Ecology, and Telemetry Lab, Oregon State University
Marine Mammal Institute, Oregon State University
Funding:
OSU Marine Mammal Institute Gray Whale License Plate Funds
