水电梯级开发进程中澜沧江干流鱼类群落演变特征

澜沧江水能资源丰富,水电梯级开发盛行。研究结合历史数据搜集和现状调查,通过对比分析,揭示了水电梯级开发进程对澜沧江干流鱼类群落影响及其机制。结果表明,梯级水电站建设进程中,澜沧江渔业产量逐步增加,与水电装机容量呈极显著正相关关系(r=0.936,P<0.01),截至目前,已增长了约8倍,达到53930 t;鱼类多样性在水电开发初期因土著鱼类的消失而明显下降,但随着外来鱼类进入鱼类多样性水平出现回升。鱼类多样性指数DG-F在梯级开发之前(<1990)、之后(2008—2013)与当前(2018—2019)分别为0.67、0.47和0.67。在水电梯级开发进程中,鱼类生境类型由急流型为主逐渐演变为了以缓流型为主,产卵类型由以产沉性卵为主逐渐演变为了以产粘性卵为主,植食性、滤食性营养类型鱼类占比逐渐增加。水电站建设后,河流流速变缓、营养物质沉降富集为浮游植物生长繁殖提供了适宜的静水条件和丰富的物质基础,促进了鱼类生物量增加。生态环境变化协同外来鱼类胁迫导致鱼类生态类型发生变异。本研究初步为水电梯级开发生态环境效应评估和鱼类多样性保护提供了理论基础。

Succession of fish community in the mainstream of Lancang River during cascade hydropower development

Due to rich hydropower resources, Lancang River has been intensively dammed for hydropower production. In this study, we investigated variations of fish communities in the mainstream of Lancang River during cascade hydropower development and explored the underlying mechanisms by collecting historical data and conducting field surveys. The results demonstrated that, as cascade hydropower developed, fishing production gradually increased and exhibited a significantly positive relationship with installed hydropower capacity (r=0.936, P<0.01), which has increased by approximately eight times until now, reaching 53930 ton. However, fish diversity significantly decreased at the beginning of hydropower development due to the disappear of native fish, but then recovered to the initial level due to exotic fish invasion. The fish diversity index of D_G-F was 0.67, 0.47 and 0.67 before 1990, 2008-2013, and 2018-2019, respectively. During cascade hydropower development, the main ecological types of fish gradually changed from riffle to slow current, and from demersal eggs to adhesive eggs; the proportion of herbivorous and filter feeder also gradually increased. After hydropower dam constructions, the flow velocity decrease and nutrient settlement created favorable conditions for phytoplankton proliferations, which contributed to fish abundance increase. The change of ecological environment and stress from invasive fish caused the shift of fish ecological types. This study will benefit the evaluation of ecological impacts of hydropower exploitation and fish diversity protection in dammed rivers.