Changes in fish resources 5 years after implementation of the 10-year fishing ban in the Chishui River, the first river with a complete fishing ban in the Yangtze River Basin

Abstract Background To rehabilitate the depleted fish resources of the Yangtze River Basin, China, a 10-year fishing ban has been implemented. This national initiative has attracted worldwide attention. The present study aimed to explore the ecological process and recovery effectiveness of this complete fishing ban in the Chishui River, the first river where the fishing ban was enacted in the Yangtze River Basin. Changes in fish resources were analyzed based on investigations conducted 5 years before (2012–2016) and 5 years after (2017–2021) the implementation of the fishing ban in four reaches along the longitudinal gradient. Results A total of 140 fish species, including 127 native and 13 exotic species, were collected during the study period. The number of fish species as well as the diversity indices showed no significant temporal changes. However, 11 native species that had disappeared for many years appeared again after the fishing ban. The occurrence rates of some key protected species, Procypris rabaudi , Acipenser dabryanus , Euchiloglanis davidi and Myxocyprinus asiaticus , increased after the fishing ban, while Coreius guichenoti , Percocypris pingi , Onychostoma angustistomata and Leptobotia rubrilabris showed no obvious recovery. The fish assemblage structure in nearly all reaches (except the headwater) showed significant temporal changes with an increase in the relative abundance of larger body-sized species. The population structure of most dominant species improved greatly with the mean standard length and the mean body weight as well as the proportion of larger-sized individuals clearly increasing. In addition, the density of fishes changed dramatically with the catch per unit effort (CPUE) increasing by 140–210% for different study reaches. Conclusions The present study confirmed that the complete fishing closure is an effective measure to facilitate fish resources recovery. These results provide valuable references for evaluating the effectiveness of the 10-year fishing ban policy in the entire Yangtze River.