楠溪江鱼类资源调查及物种多样性分析

为探究楠溪江鱼类资源现状,于2013-2014年在楠溪江6个江段共设置24个采样点,对鱼类资源进行了3次调查,每次调查时间为15~20 d。结果表明,楠溪江共采集到鱼类9目、22科、56属、65种,其中鲤形目种类最多,共3科、31属、35种,占采集种类数的53.8%。楠溪江鱼类主要以宽鳍鱲(Zacco platypus)和温州光唇鱼(Acrossocheilus wenchowensis)为优势种,相对多度分别为21.45和10.17,部分江段也以凤鲚(Coilia mystus)、盎堂拟鲿(Pseudobagrus ondon)、泥鳅(Misgurnus anguillicaudatus)、小鳈(Sarcocheilichys parvus)、沙塘鳢(Odontobutis obscura)为优势种,不同江段的渔获物组成有所差异;主要捕捞对象为定居性鱼类鲤(Cyprinus carpio)、鲫(Carassius auratus)、温州光唇鱼、宽鳍鱲、唇鱼骨(Hemibarbus labeo)、鮻(Liza haematocheila)、凤鲚、盎堂拟鲿、沙塘鳢(Odontobutis obscura)和花鲈(Lateolabrax japonicus),但鱼类捕捞规格较小,存在过度捕捞现象。楠溪江下游感潮河段与其它5个调查河段的相似性较低(0.288~0.356),属轻度相似;北溪水库与其它江段的相似性略低(0.333~0.537),其它江段达中度相似(0.615~0.737)。楠溪江鱼类多样性指数较高,Shannon-Weiner指数为2.178~2.956,Wilhm改进指数为2.207~3.009,其中北溪水库、下游河口感潮江段的鱼类多样性指数略低;Simpson优势度指数为0.7813~0.9338,Pielou均匀度指数为0.2848~0.6008。研究表明,楠溪江感潮河段及北溪水库的鱼类生物多样性低于其它干支流河段。受过度捕捞、水利水电工程梯级闸坝建设、河道采砂、环境污染等影响,楠溪江鱼类资源处于衰退之中,需要加强鱼类生态保护措施。

Fish Resource Investigation and Species Diversity Analysis of Nanxi River in Zhejiang Province

The Nanxi River is located in the lower Oujiang River and runs through Yongjia County, Zhejiang Province. It is an important water source, has a famous national tourist resort and provides the primary fishery for Yongjia County. However, overfishing, environmental contamination, sand excavation from river channels and hydropower projects, constructed from 2001 to 2014, seriously threaten the fishery resources in Nanxi River. To determine the status of fishery resources in Nanxi River, three field investigations were conducted: December 22, 2013 to January 10, 2014; March 27 to April 10, 2014 and July 16 to August 5, 2014. Twenty-four sampling sites were set in six river sections: four river sections on the main stem( Beixi Reservoir, Dayuanxi, Dananxi, Nanxi ) and two tributary sections(Yantanxi and Xiaonanxi). Fish samples were collected using gill nets, cages, stationary lift nets, stationary fishing gear and fishhook. Species, body length and weight of all fish collected were determined on site. The total Nanxi River catch included 65 fish species from 56 genera, 22 families and 9 orders, with the absolute dominance by Cypriniformes (35 species, 31 genera and 3 families), accounting for 53.8% of the total species. Species composition and number varied with river section; the number of species collected by section were 31, 38, 52, 29, 32 and 34, respectively for Beixi Reservoir, Dayuanxi, Dananxi, Nanxi, Yantanxi and Xiaonanxi. Zacco platypus and Acrossocheilus wenchowensis were the dominant species at all sampling sites with relative abundances of 21.45% and 10.17%, respectively. Coilia mystus, Pseudobagrus ondon, Misgurnus anguillicaudatus, Sarcocheilichys parvus and Odontobutis obscura were dominant at some sampling sites. Nonmigratory fish species were the primary target for fishing and included Cyprinus carpio, Carassius auratus, Acrossocheilus wenchowensis, Zacco platypus, Hemibarbus labeo, Liza haematocheila, Coilia mystus, Pseudobagrus ondon, Odontobutis obscura and Lateolabrax japonicus. However, the size of individuals collected was small, indicating overfishing in the Nanxi River. The fish community of the lower Nanxi River and estuary displayed low similarity (0.288-0.356) with the other sections. The fish community of Beixi Reservoir were of higher similarity (0.333-0.537) with the four riverine sections and the four riverine sections were moderately similar (0.615-0.737). For the Nanxi River fish community, the Shannon-Weiner diversity index, Wilhelm index, Simpson dominance index and Pielou evenness index were, respectively: 2.178-2.956, 2.207-3.009, 0.7813-0.9338 and 0.2848-0.6008. Fish biodiversity in the lower Nanxi River and Beixi reservoir was lower than in the four riverine sections. The fishery resource in Nanxi River is in serious decline, so conservation and ecological restoration measures should be taken to protect and restore fish populations in Nanxi River.