Sablefish are on the menu for southern resident killer whales, but at what cost?

The Southern Resident killer whale (SRKW) population is declining, with prey availability predicted to be the largest threat to their recovery. Decreasing quality and quantity of Chinook salmon have forced SRKWs to turn to alternative prey sources. One alternative is the sablefish, a lipid-dense groundfish found along the continental slope of British Columbia. I created a bioenergetics model to compare the foraging effort required for SRKWs to pursue sablefish instead of Chinook salmon. The model assessed the distribution, depth, body mass, and lipid density of both prey species and the daily energy requirements, cost of transport, and aerobic dive limits of SRKWs. The model found that SRKWs would need to consume more Chinook than sablefish to meet their daily energy requirements, but there was no significant different in SRKW foraging efforts when pursuing either species. These results indicate that sablefish are a viable prey alternative to SRKWs if Chinook salmon are unavailable. The management of commercial sablefish fisheries may change if SRKW or Chinook populations continue to decline.