Abundance of Non-Native Fish Species Varies Among Subtropical Reservoirs with Different Water Quality, Depths, and Ages

Dam construction facilitates the colonization of non-native fish species by altering the hydrological environment and increasing nutrient concentrations, while usually declining the richness of native fish species. The invasion of non-native fish species in subtropical reservoirs has become widespread in China; thus, research on the introduction of non-native fish species and their relationship with the environment remains urgently needed. In this study, we seasonally investigated fish communities across four reservoirs with different ages and nutrient levels in Fujian, China, examining the dominance, catch per unit effort (CPUE), and their relationships with environmental factors for native and non-native fish species. Two of the four reservoirs are 65 years old and the other two are six years old. We sampled a total of twenty-eight fish species, including six non-native species, and we found that each reservoir had non-native species, which became dominant species or important species in fish assemblage. However, the dominance and abundance of non-native species were higher in two high-nutrient-level reservoirs compared to the other two reservoirs. Both the native and non-native species’ CPUEs were positively correlated with total nitrogen concentrations and negatively correlated with water transparency. The CPUE of non-native fish species significantly increased with water depth. The CPUE of non-native species in old reservoirs was significantly lower than that in the young reservoirs. Our results suggested that a higher total nitrogen concentration and lower water depth promoted the population expansion of non-native species in subtropical reservoirs, and lower nutrient levels reduced the abundance of non-native species in those older reservoirs.