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In order to enhance the resources,some fishes were introduced into Xiangmoshan reservoir.The introduced fishes consisted of different ecotypes such as silver carp (Hypophthalmichthys molitrix (Cuvier et Valenciennes)),big head (Aristichthys nobilis (Richardso)) and lake herring (Coregonus clupeaformis (Mitchill)) that were plankton feeders,common carp (Cyprinus carpio Linnaeus) and crucian carp (Carassius auratus gibelio) belonging to the polyphagia,and also the non-native predator Walleye ((Stizostedion vitreum (Mitchill)) and big mouth (Silurus soldatovi meridonalis Chen),et al.Among there were not only the cool water fish Peled (Coregonus peled (Gmelin)),but also the warm water fish big mouth.The introduction of non-native fishes resulted in ecosystem changes of the reservoir and some native fishes had gone to decrease their population sizes or been in the condition of depopulation such as Opsariichthys uncirostris amurensis (Berg),Rhodeus sericeus (Pallas) and Silurus asotus (Linnaeus).The native common carp had disappeared after the introduction of non-native species.Roach (Rutilus rutilus lacustris (Pallas) had been thriven for one or two generations after its introduction and immeidiatly disappeared.Silver fish (Protosalanx hyalocranius (Abbott)),Lake herring (Coregonus clupeaformis (Mitchill)) and Walleye (Stizostedion vitreum (Mitchill)) died several years after the introduction,so most of the introduced species has passed out of existence.Via many years introduction of different fishes,composition of species and the structure of the population in the reservoir had been changed obviously.It was necessary to further estimate whether the ecosystem of the reservoir had been damaged.