肖四海湖五种渔具的鳜渔获结构特征及其对鳜资源的影响

为评估不同渔具对鳜资源的影响,于2007年5月和12月对长江中游浅水湖泊肖四海湖刺网、延绳钓、网簖、电拖网和电捕仪5种渔具捕获的鳜渔获物结构特征进行了调查分析.结果发现,共采集鳜样本359尾,全长分布范围为92 ～600 mm,优势全长集中于251～350 mm;体质量分布范围为10～3 380 g,优势体质量集中于300 ～500 g.种群由5个年龄组构成,2～3龄为优势龄组,占总数的74.6％.刺网、延绳钓和网簖对鳜有较强的捕捞选择性,网目大小为80 mm和100 mm刺网的鳜渔获物中2龄及以上成熟个体占总数的93.3％,个体平均体质量466 g,“标鳜”(0.4 ～0.75 kg)个体占总数量的57.0％;延绳钓捕获的鳜渔获物中2龄及以上成熟个体占总数的86.9％,“标鳜”个体占总数量的43.5％;网簖捕获的鳜渔获物中90％以上为1龄的未成熟个体.电拖网和电捕仪捕获的鳜全长范围明显较大,其渔获物以1龄和2龄个体为主.综合分析表明,刺网适于作为鳜捕捞的主要渔具,延绳钓可以作为一种鳜捕捞的辅助渔具.网簖对鳜补充群体有较大危害,不适于作为鳜的捕捞网具.电拖网和电捕仪均属于违法渔具,对鳜资源危害巨大,应该加大监管力度,严禁使用.

The catch structure characteristics of Siniperca chuatsi captured by five fishing gears and its impact on Siniperca chuatsi resources in Xiaosihai Lake

Mandarin fish Siniperca chuatsi is one of the most important piscivorous fish in freshwater ecosystem, and their natural resources in the Yangtze lakes have declined dramatically due to overfishing and eutrophication. The unreasonable use of fishing gears is often considered to be an important factor leading to overfishing. In this study, the catch structure characteristics of S. chuatsi captured by five fishing gears in a shallow lake(Xiaosihai Lake)along the middle reaches of the Yangtze River in 2007 were investigated and analyzed to explore the potential impact of the five fishing gears on the resource of S. chuatsi, and also provide basic data for fisheries management. The results indicated that a total of 359 samples of S. chuatsi were collected and the total length ranged from 92 to 600 mm. The dominant length ranged from 251 to 350 mm, accounting for 61. 0% of the total. The age structure of our collected samples contained 5 age groups ranging from 1 to 5, and most individuals were 2-3 years old accounting for 74. 6% of the total. Gill net, longline fishing and weir had strong fishing selectivity on S. chuatsi. The mature individuals with 2-year-old or above in S. chuatsi catches captured by gill net with 80 and 100 mm meshes accounted for 93. 3%. The average body weight of S. chuatsi captured by gill net was 466 g, and among them 57% individuals met the demand of "the standard S. chuatsi"(0. 4-0. 75 kg/ind. , having the best market price per kilogram). The mature individuals with 2-year-old or above in S. chuatsi catches captured by longline fishing accounted for 86. 9%, and the individuals of "the standard S. chuatsi" accounted for 43. 5% of the total. 90% of the S. chuatsi catches captured by weir were immature individuals under 1-year-old, which meant that weir was harmful to the recruitment population of S. chuatsi. The ranges of the total length of catches captured by electronic trawl-net and electric catching instrument were clearly higher, which indicated that the two fishing gears had little fishing selectivity on S. chuatsi. Their catches were dominated by 1- and 2-year old individuals, which may impact the population structural stability of S. chuatsi. Comparative analysis showed that gill net and longline fishing were good for sustainable utilization of S. chuatsi resources, and their catches could gain better economic benefit. So gill net(mesh should not be less than 100 mm.)was suitable to be the main fishing gear to fish S. chuatsi, and longline fishing could be an auxiliary fishing gear to fish S. chuatsi due to its low fishing efficiency. Weir was harmful to the recruitment population of S. chuatsi, so it was not suitable to fish S. chuatsi. The electronic trawl-net and electric catching instruments were both illegal fishing gears, which were extremely harmful to fisheries resources. Therefore, supervision work should be intensified so as to forbid the illegal use of these two gears.