珠江水系鱼类群落多样性空间分布格局

珠江是我国南方第一大河,是我国重要淡水渔业生产基地和水生生物资源基因库。珠江鱼类在维持生物多样性、提供鱼类种质资源方面举足轻重。但是到目前为止,关于其鱼类空间分布格局的研究甚少。特别是近几十年来各种水工建设和过度捕捞使得渔业资源急剧衰退,鱼类空间分布的研究显得尤为重要。2015年对珠江全流域13个站位进行了全面调查,共采集渔获物10119尾,隶属于94种72属17科。鲤科鱼类占显著优势,其次种类较多的依次为鲿科、鳅科。采用非度量多维标度排序(NMDS)方法对鱼类群落空间分布特征进行了分析,结果表明珠江鱼类被划分为3个类群,即以餐、南方拟餐、黄颡鱼等小型鱼类为主的中上游类群、以赤眼鳟、鲮鱼、广东鲂等中型鱼类为主的中下游类群和以罗非鱼为主的重要支流类群。同时发现中下游物种多样性高,上游及河口江段多样性低的格局。采用冗余分析方法(RDA)分析了鱼类多样性与环境因子的关系,发现年均气温、降雨量、年均径流量、河流宽度与透明度是珠江水系河流鱼类群落结构差异的主要影响因子,其中年均气温是影响鱼类群落分布的最关键因子之一。与历史资料对比后发现,珠江鱼类种类明显减少、空间分布也发生了巨大改变。研究是珠江水系野生渔业资源长期调查的一部分,研究结果将对渔业资源的多样性保护和可持续利用具有指导意义。

Spatial patterns of fish diversity and distribution in the Pearl River

The Pearl River, which is 2400 km long and flows into the South China Sea, is the longest river in subtropical southern China. The warm humid climate of the region, which promotes high species diversity, has resulted in significant aquatic biodiversity and the development of lucrative commercial fisheries. Nevertheless, studies on the spatial distribution of fish communities in the Pearl River system are limited, especially, considering the decline in global fishery resources due to numerous anthropogenic stressors, such as overfishing, dam construction, introduction of invasive species, and climate change. Thus, studies on the spatial distribution of fish species in the Pearl River are urgently needed. This study investigated the spatial patterns of fish diversity and distribution in the Pearl River Basin based on an investigation of 13 sample sites. A total of 10,119 individual fishes were collected during the study period, comprising 94 taxa representing 17 families and 72 genera. The Cyprinidae family, representing 49 taxa, accounted for 52% of the total number of fish species collected. Cyprinidae were the dominant family in the Pearl River, followed by Bagridae (7%; seven species) and Cobitidae (4%; four species). Non-metric multidimensional scaling (NMDS) was applied to the collected data and three separate groups were identified. The spatial variation in upstream fish assemblages differed significantly from that in downstream assemblages (P < 0.05), although clustering and diversity showed a significant spatial autocorrelation. A significantly high species diversity was recorded in the Pearl River, but low species diversity existed in the up and downstream reaches. Redundancy analysis was used to describe the relationship between the diversity patterns of fish species and associated environmental factors. Temperature, precipitation, water discharge, river width, and water chemistry play important roles in species diversity, with the average annual temperature accounting for the largest proportion of variance. A comparison with historical data for the Pearl River revealed a dramatic decline in fish species and a significant change in the spatial distribution of fish communities. Currently, the most serious threat to the ecology of the Pearl River network is the invasion of alien species. For example, non-native tilapia are now widely distributed in most of the Pearl River system, even surviving in the cooler, upper reaches of the Nanpanjiang River. In the Hongshuihe, Beijiang, and Dongjiang Rivers, tilapia is the dominant species recorded and has frequently been collected in the middle and lower reaches of the Pearl River. The present study is part of a long-term investigation into the wild fishery resources of the Pearl River. Therefore, understanding the processes outlined in this study will assist in the conservation of fish community diversity, which is critical to the success and sustainability of commercial fisheries in the Pearl River. Regularized discriminant analysis (RDA) is used by ecologists to relate a dataset (Y) of response variables (such as species abundance) to a second dataset (X) of explanatory variables (often environmental factors) and consistently outperformed other statistical tests using all the data in this study.