巢湖的太湖新银鱼食物组成分析

目的]为了分析巢湖银鱼产量变化的原因。方法]于2006年11月和2007年8月9、月在5个采样点分别进行调查,研究了巢湖的太湖新银鱼食物组成、生长指标,并结合历史资料分析了巢湖银鱼产量变化的原因。结果]结果表明,桡足类是太湖新银鱼的主要食物,在8月份食物中平均个数组成比例和出现率分别为66.32%±11.85%和100%,枝角类平均个数组成比例为27.77%±10.11%,出现率为100%,轮虫很少;在9月份食物中平均个数组成比例和出现率分别为57.86%±31.00%和87.18%,食物中枝角类平均个数组成比例为29.35%±28.06%,出现率为74.36%,轮虫极少。结论]随着富营养化加重、蓝藻频繁暴发,巢湖中浮游动物数量在不断减少,而鲚鱼数量的不断增加对银鱼产生巨大食物竞争。此外,巢湖的银鱼大量感染双线绦虫,大量感染寄生虫肯定会对银鱼的生长和繁殖产生不利影响。

Analysis of the Component of the Food for Neosalanx tangkahkeii taihuensis in Chaohu Lake

Objective] The changes of salangids output in Chaohu Lake was analyzed.Method] The samples from 5 sampling points were collected from November 2006 to August 2007 to survey the food component and the growth indicator of Neosalanx tangkahkeii taihuensis and combined with the historical data,the change of salangids output Chaohu Lake was analyzed.Results] The results showed that the copepods were a major food for Neosalanx tangkahkeii taihuensis in the Lake.In August,the average number of copepods in food composition and the proportion of emerging rate were 66.32%±11.85% and 100%,respectively;the average number of cladocera and the proportion of emerging rate were 27.77%±10.11% and 100%,respectively;and the rotifer was few.In September the average number of copepods in food composition and the proportion of emerging rates were 57.86%±31.00% and 87.18%,respectively;the average number of cladocera and the proportion of emerging rate were 29.35%±28.06% and 74.36%,respectively;and the rotifer was very few.Conclusion] With the increment of eutrophication and frequent outbreaks of cyanobacteria,the number of zooplankton in the Chaohu Lake was gradually declined and the huge competition of Coilia in food to salangids was being strengthened.In addition,the salangids infected with parasites in Chaohu Lake resulted in the negative impact on its growth and reproduction.