The impact of dams on the population viability of a migratory fish in the Yangtze River, China

Abstract

Abstract The global diversity of freshwater fish has been greatly reduced as a result of human alteration. In the Yangtze River, China, the species composition has changed hugely owing to dam construction and overfishing. However, insufficient data have prevented the status of several fish species being evaluated, including that of largemouth bronze gudgeon (Coreius guichenoti), which is a commercially important endemic species. This study describes the effects of the Xiangjia Dam on populations of C. guichenoti. A multivariate autoregressive state‐space model was applied to catch per unit effort data derived from drifting gill nets deployed in the mid‐channel before (2005–2012) and after (2013–2018) the construction of the dam. The analysis indicated that the mean instantaneous population growth rate of the population was −0.252 over the entire period and that the growth rates of both total and local populations have declined. Before the impoundment, the probability of population extinction was close to 1, which was the result of overfishing. After impoundment, the probability of extinction became 1 at all sites, and the time until quasi‐extinction has decreased. Based on the Euler–Lotka equation, the reproductive parameter (á) has declined by more than 95%. The results show that the population of C. guichenoti in the upper Yangtze is almost certain to become extinct under the current conditions because of the Xiangjiaba Dam blocking migration routes. To protect this population, conservation measures, such as hatchery supplementation, the removal of small hydropower stations in the tributaries and the relocation of fish, are required.