Benefits of stocking fewer but larger individuals with implications for native fish recovery

Artificial propagation is commonly used to reduce extinction risk for native, imperiled fish species. Thus, identifying stocking strategies that most effectively augment adult abundance a critical aspect of successful adaptive management. The threatened June sucker ( Chasmistes liorus) , endemic Utah Lake, UT, USA, experienced major declines in following extensive ecosystem degredation. Over 800 000 were stocked from hatcheries, grow-out ponds, and refuge populations 1990–2019 across range sizes seasons. Here, we evaluated post-stocking survival using Cormack–Jolly–Seber model with three covariates: size at stocking, origin, season. Survival was positively correlated evidence possible size-selective predation threshold between 200 300 mm, spring appeared produce higher rates than summer or fall. We also compared cost benefit hatchery-origin different sizes, finding fewer but larger (age-2) individuals more cost-effective smaller (age-1) individuals. Our results highlight operational changes can help maximize the efficacy native hatchery programs.