Nutrient enrichment alters life-history traits of non-native fish Pterygoplichthys spp. in sub-tropical rivers

Nutrient enrichment caused by anthropogenic activities can positively affect biological invasions as novel species can utilize additional resources in the ecosystem for population persistence. Although the effect of resource availability on plant invasions has been well-documented, the impact of nutrient enrichment on fish invasions remains unexplored. In this study, field investigations were conducted to examine the impact of nutrient enrichment on the maturity and reproduction of the invasive detritivorous fish Pterygoplichthys spp. A pair-wise greenhouse experiment was carried out to test the impact of nutrient enrichment on the performance of Pterygoplichthys spp. and the native fish Cirrhinus molitorella. Female Pterygoplichthys spp. matured at a larger size when total phosphorus concentration increased, while mean size and age at maturity of males increased with an increase in total nitrogen. Furthermore, total phosphorus concentrations were significantly lower when Pterygoplichthys spp. were present relative to those trials with C. molitorella. Eutrophication provides empty niches, which may facilitate the invasion of non-native and hypoxia tolerant fish. Thus Pterygoplichthys spp. may adjust their life-history traits to maximize fitness in eutrophic ecosystems. They might also benefit from nutrient enrichment due to their abilities to utilize phosphorus. These adaptive responses may help this non-native hybrid swarm to colonize and spread in their introduced range. These findings are instructive for understanding the relationship between biogeochemical changes and fish invasions, which will aid in minimizing the risk of biological invasions when developing management strategies in polluted ecosystems.