Recreational Postrelease Mortality of Lake Trout in Lakes Superior and Huron

Abstract The effectiveness of fishing regulations that result in the release of some angler-caught fish depends on accurate knowledge of the postrelease mortality of those individuals. In the Laurentian Great Lakes, Lake Trout Salvelinus namaycush are a major component of recreational fisheries; across large regions of the lakes, they are managed with length limit and daily quota regulations assuming a 15% postrelease mortality rate. Due to concerns regarding the accuracy of that rate, we conducted a tagging study to estimate Lake Trout postrelease mortality in Lakes Superior and Huron, and we examined environmental and fishing factors that influenced the return rates of tagged fish. The basic study design was to compare tag return rates between two groups: (1) a treatment group comprising fish that were caught and released by anglers; and (2) a control group comprising fish that were caught via trap net and released. Tag return rates for the angler-caught group were evaluated in relation to depth of capture, surface temperature at release (ST), fishing method, anatomical hook site, play time, handling time, and barotrauma. Tag return rates for angler-caught fish declined significantly with increasing ST; the other factors’ effects on tag return rates were generally small. For Lake Superior, model-averaged (Akaike's information criterion) postrelease mortality estimates incorporating ST were 15.0% (SE = 5.6%) at STs less than 10°C, 42.6% (SE = 3.0%) at STs of 10–16°C, and 43.3% (SE = 3.6%) at STs greater than 16°C. Model-averaged estimates for Lake Huron were 52.5% (SE = 26.8%) at STs less than 10°C, 45.2% (SE = 14.0%) at STs of 10–16°C, and 76.4% (SE = 5.4%) at STs greater than 16°C. Based on these findings, alternative fishery management regulations that limit recreational catch-and-release angling of Lake Trout in the Great Lakes may be prudent. Current management policies based on an assumed 15% postrelease mortality are likely underestimating the total numbers of Lake Trout that are removed by recreational anglers. Received January 26, 2017; accepted April 29, 2017 Published online June 26, 2017