基于河流网络体尺度的皖河河源溪流鱼类群落的空间格局

Spatial variations in fish assemblages within the headwater streams of the Wanhe watershed: A river network-based approach

2013年7-8月对大别山皖河河源1～3级溪流的鱼类进行了调查,着重从河流网络体空间尺度研究了鱼类多样性及群落结构的空间格局,探讨了局域栖息地条件和支流空间位置对鱼类群落的影响.1～3级溪流间,鱼类物种数随溪流级别增大显著增多,但个体数无显著变化（P＞0.05）;长河、潜水和皖水3条支流间鱼类物种数和个体数均无显著差异（P＞0.05）。鱼类物种数受局域栖息地条件（海拔）和支流空间位置（河流级别和下游量级）的联合影响,但鱼类个体数仅受局域栖息地条件（海拔）的影响。不同溪流级别和不同支流间的群落结构均无显著差异（P＞0.05）。同物种数类似,鱼类群落结构也受局域过程（海拔）和空间过程（汇合量级和下游量级）的联合影响。本研究表明,总体上皖河河源溪流网络体中的鱼类群落是局域过程和空间过程联合作用的产物。因此,为合理保护和管理皖河河源的溪流鱼类物种,有必要兼顾局域栖息地条件与河流网络连通性的保护和恢复。

Identifying the patterns of how stream fish assemblages vary spatially and how environmental factors influence fish assemblages is critical for fish species conservation and management. We evaluated the spatial patterns in fish assemblages at a river-network scale and documented the correlations between fish assemblages and local habitat features and tributary spatial position using data collected from 94 segments within headwater streams （1 st-, 2nd-, and 3rd-order streams） of the Wanhe watershed at Dabie Mountain during July and August 2013. A total of 6 288 specimens representing 42 species, 13 families and 4 orders were collected, among which species of the family Cyprinidae comprised 52.38% of total species richness. Both local habitat （i.e., canopy cover, water temperature, conductivity, substrate size, and heterogeneity） and spatial position variables （i.e., stream order, link, downstream link, and confluence link） varied significantly with a decline in elevation. We observed significant variation in fish diversity, but not abundance, among the 1 st-, 2nd-, and 3rd-order streams with higher species richness occurring in higher ordered streams. However, there was no variation in species richness and abundance among the three tributaries （i.e., the Changhe, Wanshui, and Qianshui streams）. Both habitat （i.e., elevation） and spatial variables （i.e., stream order and downstream link） had a significant influence on fish species richness, but fish abundance was only influenced by local habitat （i.e., elevation）. There was substantial overlap in assemblage structures across the three ordered streams, and an obvious nested pattern was observed for assemblage structures from 3rd-order to 1 st-order streams in turn. Additionally, fish assemblage structures were affected by both habitat （i.e., elevation） and spatial variables （i.e., confluence and downstream links）. Our results suggest that local fish assemblages in the headwater streams of the Wanhe watershed are determined by both local and spatial processes. Thus, both local habitat conditions and river-network connectivity should be considered in combination when framing schemes for the conservation and management of fish species in this study area.