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Tuesday, January 30 • 4:00pm - 4:20pm
STURGEON, ESOCIDS & COREGONIDS: Adult Muskellunge Growth and Annual Survival in Escanaba Lake, WI 1956-2015

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AUTHORS. Stephanie L. Shaw, Greg G. Sass - Office of Applied Science, Wisconsin Department of Natural Resources; Lawrence D. Eslinger, Bureau of Fisheries Management, Wisconsin Dept. of Natural Resources

ABSTRACT. Muskellunge, Esox masquinongy, are a popular sport fish in Wisconsin and throughout the extent of their native and introduced range. Muskellunge tend to naturally occur at relatively low density in most populations and are now an almost exclusive catch-and-release fishery, which can make estimation of growth and annual survival of adults difficult to obtain. We used the long term dataset (1956-2015) from Escanaba Lake, Wisconsin to evaluate sex-specific growth of adults (von Bertalanffy model). Capture-recapture data of adult muskellunge from spring fyke net surveys and angler harvest was used in a live-dead Burnham model in Program MARK to estimate apparent annual survival by sex and over time. Finally, we evaluated changes in survival over time in comparison to the changes in angler behavior and exploitation that have occurred in the Escanaba Lake muskellunge fishery, 1956–2015. Since 1956, 1,112 Muskellunge have been sampled in Escanaba Lake. The most likely von Bertalanffy model (?AIC 0.0) suggested an L_8 parameter that differed by sex (L_8 male=98.3 cm; L_8 female=114.5 cm) with a shared k (0.22) and t_0 (-1.2). All other models were implausible (?AIC > 80.0). Apparent annual survival (S) of adult muskellunge from 1956-2015 (no difference by sex, no change over time) was 0.8 (SE ± 0.01; upper and lower 95% CI 0.82 – 0.78). Annual survival of males (S_male = 0.78; SE ± 0.013) was lower than that estimated for females (S_female = 0.81; SE ± 0.015). The most likely model suggested that annual survival, and the probability of fyke net capture of adult muskellunge in Escanaba lake has changed over time (?AIC 0.0), while all other models were implausible (?AIC > 90.0). Changes in annual survival over time can be attributed to changes in angler behavior from levels of relatively high exploitation from the mid-1950s to the 1980s, followed by a shift to lower levels of exploitation in the 1990s, and then to a primarily catch-and-release fishery from the mid-2000s to present. Because of the predominantly catch-and-release nature of muskellunge fisheries, determination of vital statistics such as annual survival and maximum growth potential are critical to managing these fisheries.

Tuesday January 30, 2018 4:00pm - 4:20pm CST