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Objective: Natural dispersal or unauthorized introductions of nonnative predatory sport fish can undermine native species conservation and other fisheries management objectives. The use of reproductively sterile triploid fish may provide a lower risk stocking option (i.e., genetic and reproductive containment) for diversifying angling opportunities while possibly reducing angler motivation to illegally transplant fish. Management interest in triploid Walleye Sander vitreus is growing, and these fish are currently stocked by several fisheries agencies. However, little is known about the poststocking growth, body condition, and survival of triploid Walleye—information that is important for calibrating expectations and guiding policy regarding their use. Methods: We compared the age‐specific size, body condition, and survival of subadult (i.e., ages 0–3) triploid Walleye to those of normal diploid conspecifics in two eastern Colorado reservoirs. Paired stockings of triploid and diploid Walleye occurred over 3 years. Both fry and fingerlings were stocked each year. Result: Triploids were generally smaller in length (6.6% smaller on average) and weight (20.6% smaller) compared to diploids across all age‐classes. Despite being smaller, triploids had similar body condition relative to diploids. On average, the survival of triploids from spring stocking to their first fall was 6.3× lower than that of diploids, but no differences in survival were observed beyond this early life stage. This pattern was consistent across cohorts and reservoirs. Conclusion: The present work provides a foundation for future studies that are designed to clarify patterns of survival from spring to the first fall by accounting for size at stocking and natural‐origin fish and studies that are planned to assess the poststocking performance of triploid Walleye independent of diploids. Impact statementBalancing recreational fisheries management with native species conservation efforts can be challenging, especially in cases where anglers highly value nonnative predators. The practice of stocking sterile fish is an emerging management approach aimed at addressing concerns about introducing or maintaining existing populations of predatory fish outside of their native range. While artificially induced triploidy is among the most common methods for producing sterile fish, little is known about how triploid fish grow and survive in the wild, information that is crucial for decision making regarding their use. In this study, we provide some of the first information regarding the size, body condition, and survival of triploid Walleye relative to normal, diploid Walleye in the wild. Our findings will aid managers in making decisions regarding the use of triploid Walleyes in their programs. [ABSTRACT FROM AUTHOR]

Altering food web structure has been shown to influence mercury (Hg) concentrations in sport fish. Here, we describe a whole-system manipulation designed to assess the effectiveness of stocking relatively high-quality, low-Hg prey (rainbow trout, Oncorhynchus mykiss) as a means of increasing northern pike (Esox lucius) growth to reduce Hg concentrations. A replicated pond experiment served as a reference for the lake experiment and provided information to parameterize bioenergetics simulations. Results indicate that stocking relatively high-quality, low-Hg prey is a rapid and effective method to reduce sport fish Hg concentrations by up to 50% through an increase in individual northern pike biomass. Large northern pike, the fish that tend to be the most contaminated, were affected most by the manipulation. The observed declines in northern pike Hg concentrations indicate that stocking might be used to reduce Hg concentrations in sport fish prior to harvest. However, after 1 year, northern pike Hg concentrations rebounded, suggesting that reductions would be temporary without continuous stocking. Thus, perhaps the most effective method of perpetually reducing sport fish Hg concentrations would be to manage for the development of a naturally reproducing forage fish population with relatively high energy content and low Hg concentrations. On a demontre que la modification du reseau alimentaire influence les concentrations de mercure (Hg) chez les poissons d'interet sportif. Nous decrivons ici une manipulation a l'echelle du systeme entier destinee a evaluer l'efficacite d'un empoissonnement de truites arc-en-ciel (Oncorhynchus mykiss) de qualite relativement elevee se nourrissant de proies a faible teneur en Hg comme moyen d' augmenter la croissance des grands brochets (Esox lucius) afin de reduire leur concentration de Hg. Une experience conduite en double en etang a servi de temoin pour l'experience en lac et a fourni les renseignements necessaires pour determiner les parametres des simulations bioenergetiques. Les resultats indiquent que l' empoissonnement de poissons de qualite relativement elevee et a proies a faible teneur en Hg est une methode rapide et efficace de reduire les concentrations de Hg chez les poissons sportifs de jusqu'a 50 %, par le moyen d'une augmentation de la biomasse individuelle des grands brochets. Les grands brochets de taille superieure, soit les poissons qui ont tendance a etre le plus contamines, sont les plus affectes par la manipulation. Les declins observes dans les concentrations d'Hg chez le grand brochet indiquent que l'empoissonnement peut servir a reduire les concentrations d'Hg chez les poissons sportifs avant la recolte. Cependant, apres une annee, les concentrations d'Hg chez le grand brochet remontent, indiquant que les reductions seraient temporaires sans un empoissonnement continu. Ainsi, la methode la plus efficace de reduire de maniere permanente les concentrations d'Hg chez les poissons sportifs serait peut-etre d'amenager l'etablissement d'une population de poissons fourrage a relativement fort contenu energetique et a faible concentration d'Hg qui se reproduirait naturellement. [Traduit par la Redaction], Introduction Mercury (Hg) contamination in fish is a worldwide concern to human and ecosystem health (Bodaly et al. 1993; Johnston et al. 2003; Kamman et al. 2005). Recently, the potential [...]