Inland fisheries are vitally important for food security in many parts of the world; however, many are threatened by overexploitation. Harvesting can have strong impacts on fishes, driving declines in abundance, and occasionally, changing life history traits. Much of our current understanding of these phenomena is shaped by studies conducted decades or centuries after the onset of fishing. Newly established fisheries provide an opportunity to understand a critical, and often overlooked early phase in a fisheries development. In this study, we analyzed temporal trends in catch data and life history traits of the cyprinid fish Rastrineobola argentea, now the target of a growing artisanal fishery in Lake Nabugabo, Uganda. Our goal was to quantify the expansion of this fishery and test for coincident changes in the demographic and life history parameters of R. argentea. First, we found that the R. argentea fishery intensified and became more selective over the past decade. Second, abundance of R. argentea (fishery-independent CPUE) in the lake decreased by ~98.3% between 2008 and 2019. Finally, we observed a significant increase in egg volume, and in the ovary weight of some individuals (body weight <0.2 g). Although we found no difference in length at maturity, fecundity, clutch volume and ovary weight for some individuals (body mass > 0.2 g), given the declines in abundance, we believe that overexploitation may be occurring. This fishery provides food security and employment for ~22 million people in the region and so it is critical to monitor changes in abundance.