Global trade of live aquatic products creates enormous economic benefits which also results in massive aquatic species introduced into novel ecosystems.However,there is little knowledge about the impact of aquatic alien species on ecosystems and management for these alien species is minimal.Here,we use Hypostomus plecostomus as a model system which is native to South and Central America and now is a common alien fish in South China.We conducted a field survey on H.plecostomus(n=46)to investigate the population traits in Dongjiang river which is a tributary of Pearl River.To assess its impact on nutrient dynamic in water body,we also performed a greenhouse experiment to compare the impacts between invasive fish H.plecostomus and native fish Cirrhinus molitorella on nitrogen(N)and phosphorus(P)dynamics in water bodies.We found that 1)the catch per unit effort of H.plecostomus was 15 kg – 20 kg in the survey site; 2)their weights vary between 4.9 g-448 g while lengths vary between 8.1 cm-37.3 cm; 3)The ratio of male and female was 3:2 and 30%fish had experienced early stage of gonad development; and 4)P concentration significantly decreased in H.plecostomus farming water than that in C.molitorella farming water,while N concentration did not differ between the water two species farmed.These results suggest that H.plecostomus has established its population in Dongjiang river and might has important impact on P dynamic in aquatic ecosystem which in turn significantly affects native ecosystem functions.