大藤峡大坝蓄水对浔江鱼类群落的影响

2017年7月至2021年2月对浔江鱼类资源进行调查（每月调查一次），以定制刺网、虾笼和钓钩为主要作业网具，结合相对重要性指数、鱼类丰度生物量比较（ABC）曲线、相似性分析、非度量多维尺度分析、生态网络和零模型等分析方法，探讨广西大藤峡大坝蓄水对浔江鱼类群落的影响。调查期间共采集鱼类77种，隶属7目19科63属。卷口鱼（Ptychidio jordani）、赤眼鳟（Squaliobarbus curriculus）、鲤（Cyprinus carpio）、粗唇鮠（Leiocassis crassilabris）的相对重要性指数（IRI）值为850.59-2347.23，表明它们是浔江优势种。大藤峡大坝蓄水后浔江鱼类群落发生了一系列变化：（1）鱼类群落相似性聚类分析显示，各年度间鱼类群落相似度均大于59.73%，总体呈现出时间相隔越远群落相似性越低的趋势。此外，鱼类种类数由69种下降为51种；（2）浔江鱼类群落受干扰程度随着时间的推移而增加，鱼类丰度生物量比较曲线（ABC曲线） W值由0.052降至-0.004。此外，基于浔江鱼类所构建的生态网络集散节点数不断减少，结构趋向于简单化，生态网络稳定性减弱；（3）基于时间生态位研究结果表明鱼类种间竞争加剧，时间生态位重叠增幅最大的种对是罗非鱼sp-东方墨头鱼以及卷口鱼-鲫等生态习性相近鱼类。（4）基于时间生态位重叠指数构建的零模型结果揭示了浔江鱼类群落构建取决于环境因素，大坝蓄水后浔江鱼类群落向竞争主导的随机分布发展格局转变。综上所述，大藤峡大坝蓄水对浔江鱼类群落产生较大的影响，亟需采取相应的保护措施。研究为后续浔江鱼类资源的保护和恢复工作以及大藤峡大坝运行的建议提供理论基础。

Effects of impoundment of Datengxia Dam on fish community of the Xunjiang River

Fish resources were investigated once a month from July 2017 to February 2021, and the customized gill nets, shrimp cages and fishing hooks were used as the main operating tools, analysis methods such as Index of Relative Importance (IRI), Abundance Biomass comparison Curve (ABC), similarity percentages analysis (SIMPER), non metric multi-dimensional scaling (NMDS) ecological network, temporal niche and null models were use to explore the impact of the Datengxia Dam on the fish community in Xunjiang River, Guangxi Province. During the survey, a total of 77 fish species were collected, belonging to 7 orders, 19 families and 63 genera. The Index of Relative Importance values of Ptychidio jordani, Squiliobarbus curiculus, Cyprinus carpio and Leiocassis crassilabris were between 850.59 and 2347.23, which meant that they were the dominant species in Xunjiang River. The results showed that a series of changes have taken place in the fish community of Xunjiang River after the operation of this dam:(1) The similarity percentages analysis of fish community showed that the similarity of fish community was more than 59.73% in each year, and these similarity were lower with the time going by. Besides, the number of fish species has decreased from 69 to 51; (2) The disturbance of fish community in Xunjiang River increased with time. Firstly, the results of fish Abundance Biomass comparison Curve showed that the W value decreased from 0.052 to -0.004. Moreover, the number of ecological network nodes constructed based on fish in Xunjiang River was decreasing, the structure tended to be simplified, and the stability was weakening; (3) The results of temporal niche showed that competitions between fish species has intensified, and the species pairs with the largest increase in temporal niche overlap were tilapia and Garra orientalis, Ptychidio jordani and Carassius auratus; (4) The results of the null model constructed based on the time niche overlap index revealed that the construction of Xunjiang River fish community depended on the environmental factors. After the dam impoundment, fish community has changed to a random distribution development pattern dominated by competition. To sum up, the operation of Datengxia Dam had a great impact on the fish community in the Xunjiang River, and it is urgent to take corresponding protective measures. This study contributes to environmental protection and provides a theoretical basis for the follow-up work on the recovery of fish resources of Xunjiang River and suggestions on the operation of the Datengxia Dam.