东苕溪中下游河岸类型对鱼类多样性的影响

河流修复工程被美国《科学》杂志列入2000年最具发展潜力的六大领域之一，河流修复工程对水生生态系统的影响也成为各国科学家的研究热点。本文以东苕溪中下游河段为对象，研究4种不同河岸类型（自然河岸 水生植物（A）、自然河岸 无水生植物（B）、人工河岸 水生植物（C）、人工河岸 无水生植物（D））对鱼类生物多样性的影响。本次调查共采集鱼类标本499尾，经鉴定为32种，隶属于7目10科24属。鱼类生物多样性结果显示A、B的物种丰度和Shannon-Wiener指数与D存在显著差异（P<0.05）； A的优势度指数与D存在显著性差异（P<0.05）； A、C的均匀度与D存在显著性差异。鱼类群落NMDS排序与相似性分析（ANOSIM）显示D与A、B、C能完全分开，且D与A、C存在显著性差异（P<0.05），其中A与C存在显著性差异。因此，河流修复工程中水生植被的恢复对于水生生物多样性的维持至关重要，且恢复水生植被的河流修复工程会减少该工程对鱼类群落结构和生物多样的负面影响。

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.