Monitoring and invasion risk assessment of exotic fishes in the Pearl River Basin based on environmental DNA metabarcoding technology

The Pearl River Basin is one of the most aquatic biodiversity-rich regions in China. In recent years, however, biological invasions by alien species have posed severe challenges to its native biodiversity, making early warning crucial for prevention and control. This study monitored the current distribution of alien fish species and assessed their invasion risk in the Pearl River Basin using environmental DNA (eDNA) metabarcoding. A total of 19 sampling sites were established across the Dongjiang, Xijiang, and Beijiang River, and surveys were conducted in January and July 2022. Alien fish diversity was analyzed based on eDNA metabarcoding, and invasion risks were assessed under current and future climate conditions using the Aquatic Species Invasiveness Screening Kit (AS-ISK). In total, 16 alien fish species were detected, with 14, 13, and 15 species recorded in the Dongjiang, Xijiang, and Beijiang River, respectively. Compared with historical records, the number of alien fish species in each river section has increased. Risk assessment indicated that under current climate scenarios, 10 alien fish species pose high invasion risks and 6 pose medium risks. Under climate change scenarios, Oreochromis aureus shifted from high to medium risk, while the risk levels of the other species remained unchanged. These results suggest that the Pearl River Basin faces considerable invasion pressure from alien aquatic species. Alien fish generally exhibit broader environmental tolerance, greater adaptive capacity, and higher reproductive potential than native species, highlighting the urgent need to enhance scientific prevention and control measures. This study provides a novel approach for monitoring and early warning of alien fish species and offers a scientific basis for the conservation and management of aquatic biological resources in the Pearl River Basin.