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Tuesday, January 30 • 4:20pm - 4:40pm
STURGEON, ESOCIDS & COREGONIDS: A Tool for Evaluating the Growth Potential Status of Muskellunge in Wisconsin Lakes

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AUTHORS. Timothy Parks, Timothy Simonson, Aaron Cole - Wisconsin Department of Natural Resources

ABSTRACT. Muskellunge fisheries in Wisconsin are largely managed for trophy angling opportunities. The development and maintenance of these trophy fisheries largely reliant on minimum length limit (MLL) harvest regulations, which are based on growth potential. It is often discouraging to assess and evaluate muskellunge growth potential, due to limited availability of accurate age and growth information. In response to this problem, our objective was to create a predictive growth potential model and provide a framework for biologists to identify predicted growth potential targets for individual lakes and then evaluate the current growth potential status using a tag-based alternative to traditional age-growth data. First, we modeled the relationships between lake characteristics and lake-specific asymptotic length estimated from cleithra-based growth trajectories. After selecting the most parsimonious model, we predicted lake-specific asymptotic lengths to be used as growth potential targets. These targets were then compared to tag-recapture estimates of asymptotic length, using the Fabens method. We found that our most parsimonious growth potential model showed lake area explaining 70% of cleithra-based asymptotic length. Over half of the tag-based asymptotic length estimates met or exceeded the asymptotic length targets that were predicted by lake area. Interestingly, all the predicted asymptotic length targets met or exceeded the current MLL regulations assigned to a lake, and only 80% of tag-based estimates met or exceeded these MLL regulations. The disparity between model-predicted and tag-recapture estimates of asymptotic length could represent numerous growth related factors (density-dependence, skewed sex-ratios, intra-population growth variation). Most importantly, our predictive model showed that lake surface area likely regulates muskellunge growth potential, since area typically sets the bounds for productivity of fish populations. This model has important management implications regarding growth assessments and development of MLL regulations for muskellunge.

Tuesday January 30, 2018 4:20pm - 4:40pm CST