A new study by University of Victoria (UVic) and Pacific Salmon Foundation (PSF) scientists has uncovered what adult Chinook salmon in the Salish Sea are eating—and revealed diet can differ according to region.
The study, led by UVic PhD student Wesley Greentree and published recently in Fisheries Oceanography , analyzed the contents of salmon stomachs to assess salmon diet. Greentree found that year-round, herring are the most important food for adult Chinook salmon throughout the Salish Sea. Anchovy were often found in stomachs collected near Howe Sound and sand lance were important in Victoria and Sidney.
Greentree also found seasonal differences in diet, with Chinook salmon consuming a higher diversity of prey in the winter as compared to the summer. Crustaceans became a more important food source in the winter in Sooke, and lanternfish became more common in the stomachs of salmon in Campbell River and Victoria.
"The boundaries that we found between different fish communities align closely with oceanographic features that divide the Salish Sea," Greentree says. "For example, we suspect anchovy are taking advantage of freshwater from the Fraser and Squamish rivers flowing into the Strait of Georgia, and that strong tides near Campbell River and Victoria are pulling lanternfish closer to the surface, where salmon can eat them."
Conventional surveys of salmon prey can be difficult and expensive. By analyzing the stomach contents of salmon caught by recreational anglers, Greentree was able to easily and inexpensively gain a comprehensive look at what salmon eat in different areas and throughout the seasons.
"Our findings provide fisheries scientists with a better understanding of regional differences in the food chain in the Salish Sea. This knowledge can support decisions such as the designation of protected areas," says Greentree. "Our study also provides a baseline that can be used to monitor change in salmon diet and the Salish Sea food chain as ocean conditions continue to shift due to climate change."
The salmon stomachs analyzed in this study were collected through the Adult Salmon Diet Program , a community science initiative led by UVic biologist and Liber Ero Chair for Fisheries Research Francis Juanes and PSF biologist Will Duguid. Since 2017, more than 250 recreational anglers have submitted the guts of their catches and researchers have analyzed more than 7,000 salmon stomachs to date.
