基于环境DNA技术的赤水河秋季鱼类多样性分布特征

赤水河是长江上游少有的仍保持自然流态的大型一级支流，是长江鱼类重要的繁衍场和珍稀物种的保护地，摸清其鱼类多样性现状及鱼类群落结构特征对赤水河水生态恢复评估极为重要。于2021年9月对赤水河流域开展了鱼类多样性、分布及其特征调查，全流域共设置52个采样点，采用环境DNA技术采集并研究了赤水河鱼类的组成及其分布。结果显示通过环境DNA方法共调查到鱼类6目18科62属77种，包含16种长江特有鱼类。以鲤形目为主，占总数的87.87%。赤水河鱼类食性以杂食性和肉食性鱼类为主，群落结构上，处于下层水环境鱼类较多；赤水河鱼类优势种为宽鳍鱲(Y=0.205)、西昌华吸鳅(Y=0.085)、麦穗鱼(Y=0.068)、乌苏拟鲿(Y=0.033)、云南光唇鱼(Y=0.027);赤水河上游和下游鱼类群落(P<0.01)和Shannon-Wiener指数差异均显著(P<0.05)。海拔、流速、pH、电导率和温度是影响赤水河鱼类多样性的主要环境因素。为环境DNA技术在赤水河鱼类多样性调查中的应用提供了探索性研究，将有助于赤水河生物多样性的保护。

Distribution characteristics of autumn fish diversity in Chishui River based on environmental DNA metabarcoding technology

Chishui River, one of the first-level tributaries in the Yangtze River upstream, still maintain natural flow state and is an important breeding and protecting area for rare fish species. It is essential to understand the current status of diversity and community structure characteristics of fishes in the Chishui River for aquatic diversity conservation and ecological restoration. This study sampled 52 sites in the Chishui River in September 2021. Fish diversity was surveyed using environmental DNA metabarcoding (eDNA), with 12S rDNA Miseq high-throughput sequencing. The Shannon-Wiener index, Pielou index, and Simpson index of the upper, middle and lower reaches of the Chishui River were calculated. The dominant species of the fish community were determined by calculating occurrence frequency (fi) and dominance index (Y). Community diversity and species distribution characteristics were computed by Non-metric Multidimensional Scaling (NMDS) analysis, Adonis Permutation Multivariate Analysis of Variance (PerMANOVA) and analysis of Similarity (ANOSIM). A total of 77 fish species was found in the Chishui River, belonging to 6 orders, 18 families and 62 genera, among which 16 fish species endemic to the Yangtze River. Cypriniformes was the primary order, accounting for 87.87%. The mainly feeding habits were omnivorous and carnivorous in the Chishui River. In terms of community structure, more fish was found in the lower water environment. Zacco platypus, Sinogastromyzon sichangensis, Pseudorasbora parva, Pseudobagrus ussuriensis and Acrossocheilus yunnanensis were the dominant species in the Chishui River. The Shannon index showed significant differences between the upstream and downstream of the Chishui River (P<0.05). The fish community structure was also significantly different between the upstream and downstream communities (P<0.01). The number of fish species increased from upstream to downstream of the Chishui River. Altitude, velocity, pH, conductivity and temperature were main environmental factors in affecting fish diversity in the Chishui River. This study provides an exploratory assessment for applying eDNA technology to investigate fish diversity in the Chishui River, which will contribute to aquatic biodiversity conservation in river ecosystems.