长江下游浅水湖泊石臼湖鱼类资源现状及变化趋势

根据2012-2013年对石臼湖水质和鱼类资源开展的2次调查数据,研究石臼湖水质、鱼类资源现状及演变趋势。采用水质单因子评价方法、营养状态质量指数,结合经济合作与发展OECO富营养湖泊判断标准,研究石臼湖、姑溪河、塘沟河、清水河的水质和富营养化状况;通过商业捕捞的渔获物调查,收集石臼湖和姑溪河鱼类资源数据,分析河网区鱼类种类组成、渔获物结构等渔业资源现状。结果表明,石臼湖及毗邻水域存在一定程度的水污染,且湖区受水量变化影响低于河流区,总体水质状况符合地表水环境质量Ⅲ~Ⅳ类,为富营养状态。石臼湖分布鱼类110种,2012-2013年共调查到54种;其中,石臼湖38种,固城湖33种,姑溪河51种。石臼湖、固城湖和姑溪河主要经济鱼类(数量和重量均超过1%的种类)分别有13、11和9种。石臼湖鱼类主要以鲤Cyprinus(Cyprinus)carpio]、鲫(Carassius auratus)、鲇(Silurus asotus)等适应静、缓流生境的鱼类为主,并以歺又鱼(Hemiculter leucisculus)、鲫、棒花鱼(Abbotina rivularis)等小型鱼类或小规格个体鱼类(1 000 g)为主;湖区天然渔业资源呈衰退趋势,由于和长江下游干流相通,姑溪河鱼类种类数高于湖区,但其生物量远低于湖区;渔业资源的分布状况与水质状况无明显相关性,与河湖的连通性有关;受枯水期水量偏少、上游和周边来水污染以及高密度水产养殖的影响,石臼湖水质出现氮、磷和有机污染物超标等问题。宜采取源头控污、限制养殖、渔民转产以及人工增殖等措施,保护石臼湖水质,恢复天然渔业资源。

Status and Trend of Fishery Resources and Water Quality in Shijiu Lake on the Lower Yangtze River

The shallow lakes in the middle and lower Yangtze River basin form a unique, complex ecosystem connected with the Yangtze River and it supports many fish species that migrate between lakes and rivers. Shijiu Lake, located in the lower reaches of Shuiyang River, flows into Yangtze River in Dangtu County of Anhui Province and is connected to the Sancha, Tanggou, Yunliang and Guxi Rivers. In this study, the status and trend of water quality and fishery resources in Shijiu Lake and adjacent rivers were investigated in 2012-2013. The water quality status and trophic status of Shijiu Lake and the Guxi, Tanggou and Qingshui Rivers were evaluated by combining single factor evaluation with the Nutrient Quality Index (NQI) and lake eutrophication standards as proposed by the Organization for Economic Cooperation and Development (OECD). The species composition, community structure and fishery resource status were evaluated in the river-lake network, especially in Shijiu lake and Guxi river, by analyzing data from commercial fishing and data collected in this investigation. Field investigation of fishery resources in Shijiu Lake and adjacent waters was carried out from September to October, 2012, and from December 2012 to January 2013. All fish were identified, body length and body weight measured and specimens were preserved in 8% formalin for further laboratory analysis. The water quality status of Shijiu Lake and adjacent waters are Class III-IV according to the Surface Water Environment Quality Standard and Shijiu Lake and Guxi River are eutrophic. The total fishery resource in Shijiu Lake consists of 110 species, according to data collected previously, and 54 species were found during the 2012-2013 field investigation; 38 species in Shijiu Lake, 33 in Gucheng Lake and 51 in the Guxi River. The primary fish species by both number and weight (>1% of the fish caught) included 13, 11 and 9 species, respectively, in Shijiu Lake, Gucheng Lake and Guxi River. The species in Shijiu Lake were mostly those that prefer static and slow water, such as Cyprinus (Cyprinus) carpio Linnaeus, Carassius auratus (Linnaeus) and Silurus asotus Linnaeus and smaller species (<1000 g) such as Hemiculter leucisculus (Basilewsky), Carassius auratus (Linnaeus) and Abbotina rivularis (Basilewsky). The fishery resources in Shijiu Lake and adjacent waters are tending toward degradation and, while the fish species richness was higher in Guxi River than in the lake, the biomass was far lower. The distribution of fish species in the lake was not related to spatial variation of water quality, but the aquatic system is being affected by its connection with the Yangtze River. The decreased water volume in Shijiu Lake during the dry season is exacerbating the problems of excessive inputs of nitrogen, phosphorus and organic pollutants, upstream runoff and high density aquaculture. To protect the water quality and restore the fishery resources in Shijiu Lake, pollution sources must be controlled and the scale of aquaculture restricted by implementing artificial breeding programs.