Increasing invasion risk from the northward expansion of largemouth bass (micropterus salmoides) in china under multiple influences

The introduction of non-native aquatic species to develop aquaculture may inadvertently cause substantial adverse ecological impacts. Largemouth bass (Micropterus salmoides) is farmed with high production across a wide range of territory in China, yet is among the "world's worst invaders". Despite its extensive cultivation, the potential spawning area (PSA) of largemouth bass in China's natural waterbodies has hitherto not been systematically assessed. This paper statistically analyzes aquaculture production (1983-2020) and distribution records (literature, media, field) of largemouth bass in China. In addition, water temperature requirements which support vital life-history processes of largemouth bass were investigated and its PSA (1970-2010) in China was simulated based on environmental suitability curves. The results show that 90.3% of the provinces in mainland China farmed largemouth bass, with production increasing from 126,374 t in 2003 to 619,519 t in 2020, an average annual increase in production of 9.8%. From 1970 to 2010, the PSA of largemouth bass expanded by 183.7 km from the Pearl Basin to the high latitude watersheds in northern China (P < 0.001). Largemouth bass can spawn in the Niulan and Gan Rivers in the Yangtze Basin and pose an invasion risk to the entire Basin regardless of habitat fragmentation. Analysis shows that multiple influences including aquaculture escapement, climate change and reduced fishing pressure combine to increase the invasive risk of largemouth bass in the Yangtze Basin. Currently, 17 exotic aquatic species used for aquaculture have become established in the waters of southern China alone, highlighting the necessity to assess PSA and formulate both specific and generalized management countermeasures to mitigate the ecological risks posed by exotic cultured fish.