金沙江下游支流大汶溪鱼类资源现状与保护对策

Current Situation and Protection of Fish Resources in Dawen Stream in the Lower Reach of Jinsha River

2011年7月至2013年3月对金沙江下游支流大汶溪进行了6次鱼类资源调查，共设3个采样点，每次调查时间为10～15 d。结果表明，大汶溪共采集到鱼类3目、8科、28属、41种，其中长江上游特有鱼类8种；大汶溪上游以齐口裂腹鱼[ Schizothorax （ Schizothorax） prenanti]、短体副鳅（ Paracobitis potanini）和短须裂腹鱼[ Schizothorax （ Schizothorax） wangchiachii]为优势种，中游以齐口裂腹鱼、短体副鳅为优势种，下游以鲫（ Carassius auratus）、宽鳍鱲（ Zacco platypus）、蛇鮈（ Saurogobio dabryi）为优势种，不同江段的渔获物组成存在差异；主要捕捞对象齐口裂腹鱼平均体重低于80 g、起捕规格小于10 g，存在过度捕捞现象。大汶溪鱼类多样性指数较高，Shannon-Weiner多样性指数（H）、Wilhm改进指数（H′）、Simpson优势度指数（C）、Pielou均匀度指数（E）分别为1．683～2．785、1．116～2．789、0．6597～0．9016、0．2831～0．4762，但整体上低于金沙江绥江段，该江段此4项指数分别为3．230、2.893、0．9421和0．4681。向家坝水电站淹没成库以及过度捕捞对大汶溪鱼类资源形成威胁，需要加强鱼类生态保护措施。

Dawen Stream is the important tributary in the lower reach of the Jinsha River and it is inhabited by many fish species endemic to the upper Yangtze River.However, the cofferdam closure of Xiangjiaba hydropower station in December 2008 and subsequent filling of Xiangjiaba Reservoir （ 354 m in October 2012 , 370 m in July 2013 ） has significantly altered the ecosystem and fish habitat of Dawen Stream.The original condition （ baseline ） of the fishery resource in Dawen Stream was described using data collected from July 2011 to March 2013, with the assis-tance of personnel from the Agricultural Bureau of Suijiang County, Yunnan Province.Results provide a scientifi-cally based reference point for the conservation of fish resources in Dawen Stream.Surveys of fish catches in Dawen Stream were conducted at Qingshui （ upper reach） , Banli （ middle reach） and Tianbazi （ lower reach） six times during the study period.Each survey lasted 10 to 15 days.Fish catches were collected mainly by gill nets, hooks and electric fishing devices.Species, body length and body weight were recorded and samples of each species were preserved with 10%formalin for laboratory analysis.A total of 41 fish species, belonging to 3 orders, 8 families and 28 genera, were collected and included 8 species endemic to the upper Yangtze River.There were three domi-nant species [ Schizothorax （ Schizothorax） prenanti, Paracobitis potanini and Schizothorax （ Schizothorax） wangchi-achii] in the upper reaches of the Dawen Stream, two dominant species [ Schizothorax （ Schizothorax） prenanti and Paracobitis potanini] in the middle reaches,three dominant species （ Carassius auratus,Zacco platypus and Sauro-gobio dabryi） in the lower reaches.The composition of fish catches among different sections of the stream varied, and the number of fish species gradually increased from the upper reaches to the lower reaches.The average weight of the main species Schizothorax （ Schizothorax） prenanti was less than 80 g,and the first capture standard weight was less than 10 g, indicating serious overfishing in Dawen Stream.The biodiversity index of the fish community was generally high, but lower overall than the index of the Suijiang section of the Jinsha River.In conclusion, the fish resources in the Dawen Stream are threatened by the impoundment created by Xiangjiaba Dam and by overfis-hing.There is an urgent need to protect the endemic fishery resource in Dawen Stream.Based on results from this investigation, several protection measures are suggested：establishment of fish breeding conservation areas, regula-tion of fish catches to reduce resource utilization, strengthened fishery resource administration and implementation of mitigation measures to reduce the ecological impacts of the altered hydrology of Dawen Stream.