The Comparative Study On Fish Community Structure In He-wang-miao Oxbow And Tian-e-zhou Oxbow,Yangtze River

He-wang-miao Oxbow located in Jianli section of the Yangtze River is open old-course of the Yangtze River,the Oxbow was approved as Neophocaena asiaeorientalis asiaeorientalis reserve in 2014.Tian-e-zhou Oxbow located near Shishou City in Hubei Province is separate from the main channel of Yangtze River.The Lipotes vexillifer reserve was found in 1992 and carried out ex-situ conservation for Neophocaena asiaeorientalis asiaeorientalis.Fish resources study about He-wang-miao Oxbow is lack of.The fish resources survey was carried out in He-wang-miao Oxbow at April,June,August,September and December 2016 in order to understand the characteristic of fish community and resource of the forage fish of finless porpoise.In order to the construction and management of finless porpoise ex-situ nature reserves,analyzing the difference of fish community structure between He-wang-miao Oxbow and Tian-e-zhou Oxbow by comparing with the difference of fish species composition,diversity index and dominant small-sized fish species.The main results were as follows:1.A total of 42 species were collected in He-wang-miao Oxbow,belonging to 6 orders,12 families,and 42 genera.The catch species most in autumn,have 29 species.Followed by summer,28 species and 23 species of winter,the spring was fewest only 18 kinds.Species of seasonal variations consist with CPUE.Based on value of IRI in whole year,there were 5 dominant species in He-wang-miao Oxbow,which were Carassius auratus,Hemiculter bleekeri,Pseudobrama simony,Culter alburnus and Hemiculter leucisculus.The dominant species have change at different seasons.Cyprinus carpio,Cultrichthys erythropterus and Siniperca chuats dominated in spring.Cultrichthys erythropterus dominated in summer.Xenocypris argentea and Hypophthalmichthys molitrix dominated in autumn.Xenocypris argentea,Ctenopharyngodon idellus and Saurogobio dabryi dominated in winter.Divided four seasons into A and B two groups with the mumber of fish species.Group A including spring and winter,Group B including summer and autumn.Found fish community structure present seasonal fluctuations in He-wang-miao Oxbow,the major reason for seasonal fluctuations is specise composition and variation of abundance of fish species which adapted to flowing water environment,such as Hemiculter bleekeri and Xenocypris argentea.2.A total of 23 small-sized fish species were collected in He-wang-miao Oxbow and 22 small-sized fish species were collected in Tian-e-zhou Oxbow.Carassius auratus,Hemiculter bleekeri,Pseudobrama simony and Hemiculter leucisculus dominated in He-wang-miao Oxbow,while Xenocypris davidi,Hemiculter leucisculus,Coilia brachygnathus and Carassius auratus dominated in Tian-e-zhou Oxbow.The Shannon-wiener diversity index,Simpson dominance index,Pielous evenness index and Margalef richness index of fish in He-wang-miao Oxbow were 1.98,0.78,0.52 and 4.71,while 2.33,0.85,0.64 and 4.66 in Tian-e-zhou Oxbow.The result of Abundance Biomass Comparison(ABC)curves indicate He-wang-miao Oxbow was suffered high disturbance and Tian-e-zhou Oxbow was suffered moderate disturbance.The fish community structure has high similarity between He-wang-miao Oxbow and Tian-e-zhou Oxbow.The value of Bray-Curtis is 21.99%.Hemiculter bleekeri,Xenocypris davidi,Coilia brachygnathus,Hemiculter leucisculus,Pseudobrama simony,Carassius auratus and Squalidus argentatus are major species caused fish community structure differences between He-wang-miao Oxbow and Tian-e-zhou Oxbow.The main reason for the differences of fish community structure between He-wang-miao Oxbow and Tian-e-zhou Oxbow were fishing pressure,connectivity of Yangtze River and Oxbow,enhancement and releasing.To increase the small-sized fish resources and ensure finless porpoise have enough forage fish.We suggest strengthening the fishing moratorium in He-wang-miao Oxbow,increasing the small-sized fishes by adoption of fries reproduced in mainstream of Yangtze River by filling with river flows and improving habitat to provide good breeding grounds for the lake resident fishes in Tian-e-zhou Oxbow.