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Salmon Steward: Winter 2021
Forage fish in B.C. waters play a key role for juvenile salmon survival in the Salish Sea. Forage fish, primarily herring, not only represent an essential food source for juvenile salmon, but also feed harbour seals – which effectively reduces predation pressures on salmon. But many Salish Sea populations of forage fish have declined, likely contributing to decreasing survival rates of young salmon.
The Salish Sea was once a highly productive place for salmon. But starting in the 1970s, marine survival rates for Chinook, Coho and Steelhead plummeted. Despite major conservation efforts, salmon have not recovered. Some populations have dropped by 90 per cent.
The Salish Sea Marine Survival Project (SSMSP), a research collaboration co-led by the Pacific Salmon Foundation, identified two primary sets of factors impacting the survival of young Chinook, Coho and Steelhead in the Salish Sea – and both are linked to forage fish. Firstly, the research prioritized climate-driven changes to the salmon food supply – such as decreases in forage fish populations. Secondly, the project determined that a dramatic increase in salmon predators, such as harbour seals, is reducing juvenile salmon survivability.
(Photo credit to Matt Hagen): Teams conduct estuary research during the Salish Sea Marine Survival Project.
“PSF’s Marine Science Program, together with many partners, are transforming the landmark SSMSP findings into salmon conservation efforts,” says Dr. Isobel Pearsall, director of the Marine Science Program. “Given the clear link between juvenile salmon survival and the marine food web, many of our projects specifically target forage fish and their habitat.”
Several PSF-led projects are addressing the emerging challenges surrounding forage fish. The Resilient Coasts for Salmon initiative, for instance, enhances the naturalization of shorelines around the east coast of Vancouver Island. Forage fish rely on healthy shorelines for survival, but manmade structures such as dykes, seawalls and jetties degrade key habitat like spawning beaches. This project will boost retention of forage fish habitat.
Another key effort is PSF’s Nearshore and Estuary Program, which is restoring estuaries surrounding the Strait of Georgia. Some forage fish, such as Pacific herring, spawn en masse in marine vegetation like eelgrass and kelp. Under the program, a Climate Adaptation Strategy is being developed to protect forage fish and other species that rely on nearshore habitat.
PSF is also supporting major projects led by partner groups.