1. Captive propagation can lead to phenotypic change in fish populations, but the broader community-level consequences of captive phenotypes remain largely unknown. 2. Here we investigate the degree to which captive propagation alters the phenotypes and ecological roles of fish stocked into wild communities. We focus on captive propagation of western mosquitofish (Gambusia affinis) for biocontrol, which represents one of the largest-scale production efforts for any fish released into the wild. 3. Captive propagation in...