By Dr. Holly Fearnbach, Marine Mammal Research Director
SR3 contributed to a research paper published this week titled “Traditional summer habitat use by Southern Resident killer whales in the Salish Sea is linked to Fraser River Chinook salmon returns”. Featured in Marine Mammal Science, this collaborative paper used 17 years of sighting data of endangered Southern Resident killer whales (SRKWs) to show that their use of historically preferred summer habitat in the transboundary waters of the Salish Sea has declined by more than 75 % between 2004 and 2020, correlating with a decline in Chinook salmon returns to the Fraser River in Canada. Finding enough food during the summer is essential so that they can fatten up before leaner winter months, and we are already seeing the effects of these changes. We have shown that the body condition of SRKWs, particularly J-pod, is also correlated with the abundance of Fraser River Chinook, with poorer body condition and survival in years with lower Chinook returns. Together, these findings emphasize the need to ensure sufficient Chinook salmon to support a viable population of SRKWs that regularly uses the Salish Sea, and the importance of limiting disturbance so that the whales can forage successfully during their increasingly limited time here. SR3 will continue to monitor the body condition of SRKWs throughout the year, to better understand seasonal changes in prey requirements and inform adaptive conservation measures by state and federal partners.
A young Southern resident killer whale chases a Chinook salmon in the Salish Sea near the San Juan Islands. Image obtained under NMFS research permit #19091. Photograph by Holly Fearnbach (SR3) and John Durban (formerly NOAA Fisheries).