柳江鱼类群落结构及多样性研究

PATTERN OF FISH ASSEMBLAGE STRUCTURE AND DIVERSITY IN LIUJIANG RIVER

为了解柳江鱼类群落结构、多样性及其与环境因子的关系,2018年7月和12月在柳江9个江段(榕江、从江、融安、柳城、象州、永福、鹿寨、河池和宜州)开展鱼类和环境调查。共采集鱼类36474尾,隶属于5目20科80属115种;其中,鲤科鱼类最多(68种),占59.13%。Shannon-Wiener多样性指数、Simpson指数、Pielou均匀度指数和Margalef丰富度指数的变化范围分别为2.13—3.12、0.81—0.93、0.58—0.80和4.65—7.18。鱼类优势种以银Squalidus argentatus、大眼华鳊Sinibrama macrops、胡Microphysogobio chenhsienensis、银鲴Xenocypris macrolepis和南方拟䱗Pseudohemiculter dispar等小型鱼类为主。丰度/生物量比较曲线表明,宜州、榕江、鹿寨、柳城、象州和融安江段鱼类群落受到中度或严重干扰,河池、从江和永福鱼类群落结构相对稳定。采用非度量多维标度排序(NMDS)方法对鱼类群落的时空分布特征进行分析,将鱼类划分为3个类群:柳江上游的从江-榕江类群,洛清江支流的永福-鹿寨类群,柳江中下游及龙江支流的融安-柳城-象州-河池宜州类群。采用典范对应分析(CCA)分析鱼类群落与环境因子的关系,发现河宽、海拔和pH是柳江鱼类群落结构差异的主要影响因子。与历史资料相比,柳江鱼类群落结构发生显著变化,经济鱼类占比减少,鱼类个体呈现小型化和低龄化。建议从以下几个方面加强柳江鱼类多样性保护:加强执法力度,严厉打击偷捕、电捕等非法行为;对主要经济鱼类开展增殖放流;恢复河流的连通性;对流域珍稀特有鱼类进行监测、救护和繁育。

Liujiang River is the second largest tributary of Xijiang River in the Pearl River.It has rich species diversity and complex habitat types,which play an important role in maintaining the biodiversity of the basin.In aquatic ecosystems,fish species richness and assemblages have been recognized as one of the most sensitive and reliable indicators for ecosystem processes and function.Maintaining fish diversity is the basis of the sustainable development of fisheries.To understand the diversity of fish community structure and its relationship with environmental factors in the Liujiang River,fish and environmental surveys were conducted in 9 sections of Liujiang River(Rongjiang,Congjiang,Rong’an,Liucheng,Xiangzhou,Yongfu,Luzhai,Hechi,and Yizhou)in both July and December 2018.A total of 36474 individuals belonging to 115 species,80 genera,20 families,and 5 orders were collected,among which,Cyprinidae was the most abundant with 68 species,accounting for 59.13%.Shannon-Wiener diversity index,Simpson index,Pielou evenness index,and Margalef richness index ranged from 2.13 to 3.12,0.81 to 0.93,0.58 to 0.80,and 4.65 to 7.18,respectively.The fish diversity was relatively rich,the fish richness was high,and the individual distribution was relative uniform.The dominant fish species were small fishes,such as Squalidus argentatus,Sinibrama macrops,Microphysogobio chenhsienensis,Xenocypris macrolepis,Pseudohemiculter dispar.The abundance/biomass comparison curve showed that the fish communities in Yizhou,Rongjiang,Luzhai,Liucheng,Xiangzhou,and Rong’an were moderately or seriously disturbed,and there were relatively stable in Hechi,Congjiang,and Yongfu.The spatial and temporal distribution characteristics of fish communities were analyzed by non-metric multidimensional scale sorting(NMDS),and the fish communities were divided into three groups:Congjiang-Rongjiang group in the upper reaches of the Liujiang River,Yongfu-Luzhai group in the tributaries of the Luoqing River,and Rong’an-Liucheng-Xiangzhou-Hechi-Yizhou group in the middle and lower reaches of the Liujiang River and the tributaries of the Longjiang River.Canonical correspondence analysis(CCA)was used to analyze the relationship between the fish community and environmental factors.It was found that river width,altitude,and pH were the main impact factors of fish community structure in the Liujiang River.Compared with the historical data,the fish community structure in the Liujiang River has been changed significantly,the proportion of economic fish has decreased,and the fish individuals have become smaller and younger.In addition,the Liujiang River was threatened by alien aquatic species invasion.There are several ways to strengthen the protection of fish diversity in Liujiang River such as strengthen law enforcement,crack down on illegal activities such as poaching and electric fishing;released the economic fish;restoration of river connectivity;to monitor,rescue and breed the rare and endemic fish in the basin.