Diversity and composition of fish in the mainstream of national nature reserve of rare and endemic fish in the upper Yangtze River

The composition and distribution of fish was investigated in Yibin,Hejiang and Jiangjin section of the mainstream of National nature reserve of rare and endemic fish in the upper Yangtze river for 4 times during September to November of 2010,May to July and September to November of 2011 and May to July of 2012.27836 fish samples belonging to 7 orders,17 families,111 species were collected.In these species,27 species were endemic to the upper reaches of the Yangtze River,45 species were those that spawn drifting eggs and 6 species were exotic fish.85,91 and 91 species were found in Yibin,Hejiang and Jiangjin section respectively.The Jaccard' s similarity indices were 69.23% between Yibin and Hejiang section,71.70% between Hejiang and Jiangjin section,and 77.78% between Yibin and Jiangjin section.Coreius heterodon,Silurus meridionalis,Rhinogobio ventralis and Coreius guichenoti were the main commercial species captured in the reserve area,and the fish which spawn drifting eggs accounted for 66.35% of weight of fishery catches.The Shannon-Wiener diversity index of Jiangjin section was the highest in every survey,Yibin section was middle and Hejiang section was the lowest.However,there was no significant difference of the Shannon-Wiener diversity index among the three sections(P0.05).Compared with the historical data,the current fish resources in the upper mainstream of the Yangtze River decreased obviously,thus the protection measures of fish in the Yangtze River should be urgently enhanced.