Traditional summer habitat use by Southern Resident killer whales in the Salish Sea is linked to Fraser River Chinook salmon returns

Southern Resident killer whales (SRKW, Orcinus orca) are a small, endangered population of fish‐eating killer whales that inhabit coastal and inland waters of the western United States and British Columbia. SRKW have been in decline since 1995, with food availability, vessel disturbance, and polluta...

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Bibliographic Details
Published in:Marine mammal science 2023-07, Vol.39 (3), p.858-875
Main Authors: Stewart, Joshua D., Cogan, Jane, Durban, John W., Fearnbach, Holly, Ellifrit, David K., Malleson, Mark, Pinnow, Melisa, Balcomb, Kenneth C.
Format: Article
Language:English
Subjects:
Animal population
Aquatic mammals
Availability
Carnivorous animals
Catch per unit effort
Coastal waters
Endangered populations
Endangered species
Fish
Fish populations
Food
Food availability
food limitation
Food sources
Food supply
Freshwater fishes
generalized additive models
Habitat selection
Habitat utilization
Habitats
Inland waters
killer whale
Marine mammals
Oncorhynchus tshawytscha
Orcinus orca
predator–prey dynamics
Rivers
Salmon
Summer
Trends
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Summary:Southern Resident killer whales (SRKW, Orcinus orca) are a small, endangered population of fish‐eating killer whales that inhabit coastal and inland waters of the western United States and British Columbia. SRKW have been in decline since 1995, with food availability, vessel disturbance, and pollutants proposed as drivers of their decline. We used 17 years of sightings data from the SRKW core summer habitat in the Salish Sea to examine trends in presence of SRKW, and how these trends may be related to the availability of a key food source, Fraser River‐origin Chinook salmon. We found that SRKW occupancy has declined by more than 75%, in step with reduced average catch per unit effort (CPUE) of Fraser River Chinook salmon. J pod was present in the core summer habitat most often, followed by K and L pods. All three pods demonstrated declines in visitation to the core summer habitat from 2004 to 2020, and presence of SRKW was significantly related to annual average Fraser Chinook CPUE. Our findings suggest that declining Fraser River Chinook returns may be reaching a point where SRKW cannot reliably meet their energetic needs, driving them to forage in areas outside of their traditional core summer habitat.
ISSN:0824-0469
1748-7692
DOI:10.1111/mms.13012