###### Abstract  
Muskellunge are commonly stocked to maintain populations throughout much of North America. Poststocking survival is variable, and many jurisdictions are experimenting with stocking Muskellunge at advanced life stages (e.g., yearlings) or sizes to promote more consistent recruitment within populations. Yet, little is known about short-term poststocking behavior or survival of Muskellunge in natural lakes or if stocking larger fish results in improved poststocking survival. Radiotherapy was used to evaluate the behavior and survival of large (mean of 418 mm; standard error of 3.4) spring-stocked yearling Muskellunge in two northern Iowa natural lakes of varying biotic and abiotic complexity. Hatchery-reared Muskellunge were fitted with radio transmitters (\(n=10\)-\(15\) fish/lake), stocked in each lake with conspecifics, and tracked either daily or weekly up to 112 days poststocking. Telemetry data were used to evaluate dispersal and movement, depth and vegetation use, proximity to shore, and survival. In both lakes, fish dispersed rapidly from each stocking site. Movement among lakes was similar and peaked during the first week poststocking and declined thereafter. Muskellunge were frequently located in offshore habitats in both lakes, but both depth and vegetation use varied among lakes and weeks poststocking, with Muskellunge found in deeper, more vegetated habitats in the larger, more complex natural lake. Muskellunge in both systems had high poststocking survival (86.7-90.0%). The results of this study provide managers with more information regarding yearing Muskellunge poststocking behavior and survival and indicate that larger fish may be a suitable alternative for fisheries where high poststocking mortality may be acting as a bottleneck for maintaining quality Muskellunge fisheries. t 2024 9 2024  
in systems where emigration can contribute to high Muskellunge mortality rates [11; 12; 13] and/or where habitat degradation has limited Muskellunge natural recruitment [14]. Because of the complexity and variability within aquatic ecosystems, little can be done to enhance stocking survival once fish leave the confines of advanced husbandry. Accordingly, agencies have spent considerable time evaluating the intrinsic characteristics of rearing Muskellunge [15]. Culture practices such as rearing medium (i.e., line pond, trough or concrete raceways, earthen pond [16; 17; 18]) and Muskellunge diet (i.e., artificial or live forage) can significantly influence fish physical characteristics, such as the coloration, health, and size of reared Muskellunge [3; 19; 20; 21], which collectively have been associated with poor poststocking performance [3; 21]. Thus, agencies strive to mitigate these shortcomings via the inclusion of several rearing strategies within their culture procedures. Subsequently, nearly continuous research has been conducted with the intent to evaluate different hatchery products and their poststocking survival and contribution to wild populations. Collectively, these studies consistently document that Muskellunge size at stocking substantially influences poststocking survival, primarily through minimizing predation risks [22; 23; 15; 18; 24; 25; 26; 27; 28; 29; 30]. A better understanding of the influence of fish size and behavior of stocked Muskellunge may provide insight for improving the success of stocking. While the size at stocking relationship is well known among managers, there is little consensus on the size at which stocked Muskellunge may overcome most predation risks. Previous research has consistently identified that Muskellunge stocked \(>\) 200 mm have higher survival probabilities than their smaller stocked counterparts [4; 7; 18; 21; 23], but depending on stocking objectives, the interpretation of the success or failure of each stocked cohort is rather vague. Moreover, fish stockings are often assigned as a success or failure based on the manager's perception of the outcome and not in context to the fish's contribution to the overall fishery.