Effect of bank type on fish biodiversity in the middle-lower reaches of East Tiaoxi River,China

Degradation of river ecosystems and loss of aquatic biodiversity are widespread and ongoing problems.Many government agencies and various stakeholders now consider river restoration an essential component of conservation and natural resource management.However,despite legal mandates,massive expenditure and the burgeoning industry in aquatic and riparian restoration,river ecosystems continue to deteriorate from anthropogenic effects.Furthermore,many restoration activities have failed in many parts of the world.Erosion of natural riverbanks by boat-generated waves is an increasingly serious problem on navigable rivers,particularly on the middle and estuarine reaches.To prevent boat-induced erosion and flooding,the construction of artificial banks using stone and concrete is now common practice in China.Hydro-morphological river restoration usually leads to habitat diversification,but the effects on fish,which have been frequently used to assess the ecological status of aquatic systems,have received little attention in China.A field survey was carried out to investigate the effect of riverbank restoration on fish biodiversity in the middle-lower reaches of the East Tiaoxi River and provide information useful for river restoration and watershed management.Four bank types-(A) natural bank with aquatic plants,(B) natural bank without aquatic plants,(C) constructed bank with aquatic plants and(D) constructed bank without aquatic plants-were compared.An intensive survey of fish communities,conducted in May 2009,yielded a total of 499 individuals,including 32 species belonging to 24 genera,10 families and seven orders.The fish fauna in the middle-lower reaches showed that the most species-rich order was Cypriniformes(24 species),followed by Perciformes(2),Cyprinodontiformes(2),Beloniformes(1),Clupeiformes(1),Siluriformes(1),Synbranchiformes(1).The most species-rich family was Cyprinidae,consisting of 22 species,and accounting for 68.75% of total species.Statistical analysis,using the Shannon-Wiener Index,demonstrated that natural banks,i.e.types A and B,had a significantly higher species richness level of distribution than those of type D.Likewise,Simpson′s Diversity Index was significantly higher in bank type D than type A;while the evenness of the fish community was significantly higher in bank type D than types A or C.Non-metric multi-dimensional scaling(NMDS) ordination showed that bank type D was distinct from bank types A,B and C,indicating that the fish community in bank type D was significantly different from bank types A,B and C.In addition,an analysis of similarities(ANOSIM) of the fish communities showed that bank type D was significantly different from bank types A and C.It also showed that the fish community of bank type A was significantly different from that of bank type C.These results suggested that the restoration of aquatic vegetation is crucial to the maintenance of fish diversity during river restoration.Aquatic vegetation improves water quality and,in addition,aquatic plants,such as floating plants and submerged macrophytes,provide habitats for other aquatic organisms.River restoration,which involves habitat creation,can positively affect the structure and diversity of fish communities,halt the progressive deterioration of freshwater ecosystems and sustain a valuable ecological resource for humans.