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Monday, January 25 • 11:20am - 11:40am
Lake Trout Hooking Mortality in Lakes Superior and Huron

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AUTHORS: Shawn P. Sitar*, Michigan Department of Natural Resources; James E. Johnson, Michigan Department of Natural Resources-retired; Ji X. He, Michigan Department of Natural Resources

ABSTRACT: Lake trout compose a key component of recreational fisheries in the upper Great Lakes and are managed with length regulations. In some areas and years, recreational length limit regulations require anglers to release non-legal sized lake trout. Furthermore, stock assessment models that estimate harvest quotas for lake trout need to account for recreational catch-release mortality. Currently, these models use 15% hooking mortality which was based on the only Great Lakes study conducted in the 1980s. In that study, no lake trout were caught below 50 m and in Lake Superior, anglers frequently catch lake trout deeper, and these fish may experience barotrauma. There is concern among managers and scientists that the 15 % hooking mortality estimate may be too low. In this study, we estimated hooking mortality using mark-recapture data by comparing differential tag return rates between trapnet-caught (control) and angler-caught (treatment) and released lake trout. Furthermore, key factors that may influence hooking mortality were also measured for angler-tagged fish. These included barotrauma symptoms, fish condition at release, water temperature, depth of capture, hook location, and fishing method. During 2010-2013, 2,300 trap net caught (control group) and 1,800 angler-caught (treatment group) lake trout were tagged and released in southern Lake Superior. In west-central Lake Huron, 1,670 trap net caught and 930 angler-caught were tagged and released. Tag recapture data were accumulated between 2010 and 2015. Tag return rates were lower for angler-tagged than trap net-tagged lake in both Lake Superior and Lake Huron. We estimated overall hooking mortality to be more than double that of the 15% rate previously reported. Furthermore, tag returns rates were lower for higher water temperatures and we measured a positive relationship between water temperature and hooking mortality rate. Based partly on these findings, Lake Huron managers decided to minimize use of length-based regulations.

Monday January 25, 2016 11:20am - 11:40am EST
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