Muskellunge Esox masquinongy management programs often rely on stocking to create and maintain populations. In many instances, a native and nearby stocking source is unavailable or a genetically suitable brood source is unclear. Genetic differences among stocks of Muskellunge may influence survival and growth when introduced into novel environments. Consequently, the selection of a suitable brood source can be difficult and possibly critical to the success of Muskellunge stocking programs. We examined differences in long-term survival and growth among introduced Muskellunge stocks from the Ohio and upper Mississippi River drainages and a mixed-origin Illinois broodstock population in three Illinois reservoirs. Catch per unit effort (CPUE) from spring modified-fyke netting suggested that the upper Mississippi River drainage stock at ages 3 and 4 persisted at lower relative abundance compared to conspecifics; however, low lake- and stock-specific catches of older ages precluded robust CPUE comparisons among stocks. Apparent survival, estimated from mark-recapture data with the Cormack-Jolly-Seber open population model, differed among stocks I-year poststocking, with the upper Mississippi River drainage stock exhibiting markedly lower survival compared to conspecifics. Annual variation in survival to age 1.5 was related to water temperature at stocking, fish size at stocking, first winter temperatures, and first summer temperatures. However, survival did not differ among stocks for Muskellunge age 2 and older, indicating that important factors structuring long-term survival exert their effects most strongly in the first year poststocking. Despite overall low survival of Muskellunge from the upper Mississippi River drainage, males that survived exhibited a slight growth advantage compared to conspecifics. No growth advantage was observed for upper Mississippi River drainage stock females. Our findings suggest that stock selection in addition to environmental conditions can influence survival of introduced Muskellunge and subsequent contribution to the fishery.
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