太湖鲫鱼数量变化的规律及与环境间关系的分析

The changes of catches of Carassius auratus and relationship with environment in Lake Taihu,China

通过食物组成分析和渔获物组成调查,并结合历年渔获量统计和环境监测资料,研究了太湖鲫鱼数量变化的规律、机制及与环境间的相互关系．渔获物调查和渔获量统计资料均表明:近年鲫鱼数量不断增加,已成为太湖仅次于鲚鱼的重要鱼类．2004年渔获物调查中,鲫鱼占鱼类总重量的8．40％±2．69％,占鲤、鲫鱼渔获量的65．08％±15．47％;历年渔获量统计显示,1952-1998年鲤、鲫鱼渔获量相对稳定在1010．1±367．2 t、占鱼类总量8．89％±5．33％,1999年上升达到2547．4t、占9．45％,2000年达到3708．7t,占12．18％;年龄组成分析表明,鲫鱼低龄化趋势在加剧．食性分析表明:在7-12月,微囊藻占鲫鱼食物体积的83．65％-93．99％．分析认为:太湖鲫鱼以微囊藻为主要食物;富营养化加重为其提供了充足饵料,实施禁渔期、禁渔区等措施使其繁殖得到保障,捕捞强度过高导致其年龄组成低龄化、个体小型化．而太湖鲫鱼以蓝藻为主要食物,可能对蓝藻有抑制作用．

Based on the analysis of food content and the survey of the composition in fish catches and the data of fish catches in Lake Taihu, the amount changes of catches of Carassius auratus Linnaeus and Their Mutual Relationship with Environment were studied. The results of the survey of fish composition in 2004 and the statistics data of fish catches from 1952 to 2004 showed that： Within recent years, the catches of Carassius auratus Linnaeus had been increasing and had become the second dominant fishes following Coilia ectenes taihuensis Yen et Lin. The analysis of age structure showed that the percentage of 0 ^＋ fishes increased and the average fish body size decreased. For example, the percentage of 0^＋ Carassius auratus Linnaeus had been increasing according to the trend of y = 19. 154e^0.0566x（y means the percentage of 0^＋ fishes % , x means time a）. And the average body length had been decreasing according to the trend of y = 115.45e^-0.0312x （y means body size era, x means time a）. The results of food content analysis showed that ： the percentage of blue-algae accounted for about 83.65 % - 93.99% of food volume of Carassius auratus Linnaeus. Under the conditions of eutrophication in Lake Taihu, Carassius auratus Linnaeus mainly fed on blue-algae ; eutrophication resulted in the increasing of blue-algae which could be eaten by the fish. The measures of protecting fishes were carried out to ensure the fish propagating, In addition, the trend of percentage of low age fishes increasing and the trend of body size of the fishes decreasing were caused by over-fishing. Carassius auratus Linnaeus might restrain blue-algae increasing because it mainly fed on blue-algae.