The Salish Sea's salmon are adapting to a changing environment, and it's fascinating to see how. Researchers at the University of Victoria are analyzing the stomach contents of chinook salmon, revealing a flexible diet that varies by location and season. While herring is the primary food source, chinook salmon also consume anchovy, lantern fish, and small crustaceans.
What makes this study particularly intriguing is the insight it provides into the regional differences in the food chain. For instance, northern anchovies are now present year-round in areas like Howe Sound, a significant shift from a decade ago. Pacific sand lance, a favorite prey of humpback whales, is also making an appearance in chinook caught around Victoria and Sidney.
The research, led by PhD student Wesley Greentree, highlights the importance of understanding these regional variations. By sharing this knowledge with the Department of Fisheries and Oceans, scientists can make informed decisions about protected areas and conservation efforts. Greentree emphasizes the study's role in providing a baseline to monitor changes in salmon diet and the Salish Sea food chain as ocean conditions shift due to climate change.
One of the most fascinating aspects of this study is the seasonal variation in diet. Chinook salmon consume a higher diversity of prey in the winter compared to the summer. Crustaceans like shrimp and krill become essential food sources in the winter for salmon caught near Sooke, while lantern fish, which glow blue-green due to their light-producing organs, are more common in the stomachs of salmon in Campbell River and Victoria.
The data also reveal interesting patterns in the summer diets of chinook salmon in four areas of the Salish Sea. The Strait of Georgia has the fullest stomachs, dominated by herring. Howe Sound has a nearly equal split between herring and anchovy. Haro Strait has a nearly even split between herring and sand lance. The Strait of Juan de Fuca has the least full summer stomachs, comprising about 70% herring.
The study's findings align closely with oceanographic features that divide the Salish Sea. Pacific anchovies, for example, are taking advantage of freshwater from the Fraser and Squamish rivers flowing into the Strait of Georgia. Strong tides near Campbell River and Victoria are pulling lantern fish closer to the surface, where salmon can eat them.
This research is a testament to the importance of citizen science and community engagement. More than 250 recreational anglers have contributed samples, helping researchers analyze more than 7,000 salmon stomachs. The program, known as the B.C. Adult Salmon Diet Program, has been running since 2017 and has provided valuable insights into the feeding ecology of adult chinook salmon for the first time since the 1960s.
The study also highlights the interconnectedness of the ecosystem. Rick Hakinen, a long-time contributor to the Adult Salmon Diet Program, emphasizes the importance of understanding the entire ecosystem that supports salmon survival. His involvement in the Pacific Salmon Foundation's Bottlenecks to Survival Program, which uses PIT Tags for permanent identification of salmon, further underscores the importance of tracking salmon from release to their spawning rivers.
In conclusion, the Salish Sea's salmon are adapting to a changing environment, and this study provides a fascinating glimpse into their flexible diets and the regional variations that exist. By understanding these changes, we can better protect and conserve these iconic fish and the ecosystems they support.
