Recreational fisheries-related injuries and body size affect travel rate and post-release mortality in marine migrating coho salmon (Oncorhynchus kisutch)

Although many coho salmon (Oncorhynchus kisutch) caught in recreational fisheries are harvested, a substantial number of salmon are released after capture. Mortality rates of coho salmon released from recreational fisheries are largely unknown in the marine environment. This two-year study investigated factors associated with post-release mortality and travel rate of coho salmon in a marine recreational fishery in British Columbia, Canada. Adult coho salmon were recreationally angled in the marine environment, affixed with acoustic tags, and tracked during their return migration to natal spawning streams using a network of acoustic receivers. We found post-release mortality to the first point of detection (∼50 km from release) was 31.5% (95% CI: 26.1 – 37.4%; n = 279). Scale loss, eye damage, bleeding, and smaller body size of coho salmon were associated with increased odds of mortality. Scale loss and smaller body size were also associated with slower migration rate post-release. Air exposure up to five minutes was not found to be a driving factor in mortality or travel rate. These fishing-related injuries can cause immediate physiological and behavioural disturbances, increase vulnerability to predation, infection, and disease, and delay migration as the fish recovers. Smaller coho salmon may also be less capable of overcoming capture stress. Our study highlights the importance of quantifying mortality of wild fish in their natural environment, and we suggest that small changes to fishing practices (e.g., smaller hook sizes, less handling, etc.) could make large differences in release survival thus encouraging a more sustainable recreational fishery.