Conservation translocation – reintroducing fish into their former native range - is a management strategy widely used to facilitate population recovery. However, fish species exhibit variable responses to translocation efforts, emphasizing the need to learn from past successes and failures to improve future conservation outcomes. In Ohio, the bluebreast darter (Nothonotus camurus), variegate darter (Etheostoma variatum), and Tippecanoe darter (N. tippecanoe) have been reintroduced to eight rivers via annual translocation events since 2016, 2020, and 2018, respectively. Despite consistent relocation efforts, these species have shown different reestablishment outcomes. Specifically, the Tippecanoe and bluebreast darters have dramatically flourished, while variegate darters have displayed a low population growth rate. While many factors influence translocation success, species-level differences such as life history traits may play a pivotal role due to their influence on survival and reproduction. To investigate this, we examined how variation in body size - a key life history trait influencing fecundity, lifespan, and energetic requirements - predicts population growth rate since translocation. We hypothesize that the smaller body sizes of Tippecanoe and bluebreast darters confers ecological advantages such as earlier maturation and shorter generations times, that facilitate rapid population growth compared to the larger-bodied variegate darter. This study highlights the critical link between life history traits and translocation outcomes, providing evidence that body size is a valuable predictor for reintroduction success. By establishing this connection, our findings offer a simple and practical tool for natural resource managers to design more effective conservation translocations.