Reports of whale entanglements in fishing gear have steadily increased in US West Coast waters, with Dungeness crab fishing gear implicated in many entanglements. Managers, researchers, fishermen, and the environmental community in Oregon are concerned about this situation because whale entanglements threaten both whale populations and the stability of the crab fishery and coastal communities. The third straight record-breaking year of entanglements occurred in 2016, with deaths of federally protected humpback, gray and blue whales off the coasts of California, Oregon and Washington. The Oregon Whale Entanglement Working Group (OWEWG) formed in 2017, tasked with developing options to reduce entanglement risk. The group members identified that a lack of information and understanding of whale distribution in Oregon waters was a significant knowledge gap of high priority.
To fill this knowledge gap, we have teamed up with the United States Coast Guard (USCG) helicopter divisions in Oregon to conduct repeat surveys along the Oregon coast four times a month for two years (Fig. 1). We are also asking ocean users of all types (i.e., fishermen, scientists, USCG, tug boat captains) to become citizen scientists and collect opportunistic whale sightings data using the mobile app Whale Alert. Additionally, we participate in multiple interdisciplinary vessel-based research cruises off the Oregon coast to conduct marine mammal surveys and collect data on whale sightings.
Habitat and phenology of rorqual whales off the Oregon coast
Using these rich datasets, we have been able to describe the habitat use and distribution patterns of rorqual whales (blue, fin, and humpback whales) off the Oregon coast. In the first phase of the OPAL project, we analyzed year-round whale occurrence data (2016–2021, 177 survey days, 754 groups observed) with state-of-the-art statistical modeling approaches to describe where we expect whales to be under certain environmental conditions.
We demonstrated (1) an increase in rorqual numbers over the last three decades over the continental shelf off Oregon, (2) differences in timing of migration and habitat preferences across humpback, blue, and fin whales, and (3) predictable relationships between rorqual whale distribution and dynamic ocean conditions indicative of upwelling and frontal zones. This study has been accepted for publication in Frontiers in Marine Science and provides up-to-date predictions of rorqual whale densities at a fine spatio-temporal scale that will facilitate targeted management of human activities in Oregon (Fig. 2).
Co-occurrence between whales and fishing activity:
We collaborated with the Oregon Department of Fish and Wildlife to identify patterns of co-occurrence between commercial Dungeness crab fishing gear and rorqual whales, hence assessing the spatio-temporal variations in entanglement risk over the last decade. This second phase of the OPAL project identified the times and places when exposure to entanglement risk was the highest, using the year-round predictions of rorqual whale habitat use generated in phase one and maps of fishing effort compiled from logbooks (Fig. 3). With this information, managers can make informed and discrete decisions about fishing effort to maximize effectiveness at protecting whales while also minimizing burdens to fishermen.
Population segments and residency patternsAdditionally, when aggregations of humpback whales are observed during USCG helicopter surveys, we frequently muster a boat-based field team to head to that location and collect important whale photo-identification data and small tissue biopsy samples for genetic analysis. These data allow us to assign individual whales to Distinct
Bringing in the prey
Spatial distribution patterns of marine predators are non-random within the ocean’s patchy preyscape, and they are often highly correlated with distribution of their targeted prey. In parallel to our modeling efforts, we are also analyzing the relationships between oceanographic variables, prey availability, and whale distribution to improve the assessment of co-occurrence between whales and anthropogenic activities.
To understand relationships between environment, prey, and whale predators, we are analyzing (1) oceanographic conditions, (2) krill density, caloric content, and swarm structure (Fig. 4), and (3) marine mammal distribution data. These observations are collected synchronously during NOAA/NWFSC NCC cruises conducted between Crescent City, California and La Push, Washington aboard the NOAA Ship Bell M. Shimada each February/March, May and September.
Oregon State University Marine Mammal Institute
Oregon Department of Fish and Wildlife
Oregon Sea Grant
Derville, S., Barlow, D. R., Hayslip, C. E., & Torres, L. G. (2022). Seasonal, Annual, and Decadal Distribution of Three Rorqual Whale Species Relative to Dynamic Ocean Conditions Off Oregon, USA. Frontiers in Marine Science, 9, 868566. https://doi.org/10.3389/fmars.2022.868566
Derville, S., Buell, T. V., Corbett, K. C., Hayslip, C., & Torres, L. G. (2023). Exposure of whales to entanglement risk in Dungeness crab fishing gear in Oregon, USA, reveals distinctive spatio-temporal and climatic patterns. Biological Conservation, 281, 109989, https://doi.org/10.1016/j.biocon.2023.109989
We are conducting surveys for whales aboard USCG helicopters to increase our understanding of whale distribution and habitat use patterns in Oregon waters. We will use these data to assess entanglement risk with fishing gear to inform management decisions.