青虾生长规律与群体组成的研究

报道了上海川沙县孙桥河道青虾的生长呈明显的阶段性,如雄虾的第一阶段（1990年6—11月）的生长方程为L_t=3.381-e~(-0.4943(t+0.1674)];第二阶段（1991年2—6月）的生长方程为L_t=6.57/(1+e~(2.1805-0.2787t);它们的拐点分别为2.07月龄和11.97月龄。渔获群体分析结果表明,月龄为0-15月,体长范围为1.30—6.58cm,体重范围为0.060—13.39g;一年出现两个群体,其中夏季群体生活期从当年7月至翌年10月,数量大,占群体数量80％以上;秋季群体生活期从当年9月至翌年12月,约占群体数量20％左右。群体中一般雄虾数量多于雌虾数量,月性比(?)在0.61—1.35之间变动。

Study on the growth and population compositions of freshwater shrimp (Mocrobraricfiiurn riippomnsfe)

The growth and population compositions of freshwater shrimp (Macrobranchium nipponensis) were studied in Sunqiao channels, Chuansha County, Shanghai Municipality. The growth period is devided into two evident stages. As an example of the increase of the length (Lt) of male shrimp, the growth equation is Lt=3.381-e0.4948(t+0.1674)](r=0.941) for the former stage and the infection point is at t= 2. 07 month age. For the latter stage, the growth is fitted to Logistic curve, with the equation of Lt=6.573/(1+e2.1086-0.2787t)(r= 0.970) and the infection point at t=11.07 month age. After analysing the catching population, we found that the month age ranges from O to 15, the range of the length and body weight is 1.30-6.58cm and 0.060-13.0g, respectively.There are two kinds of population in a year, namely the summer population which is from July to the next October, the autumn one from September to the next December. The population of the male shrimps is greater than that of the female shrimps. The monthly sex ratioranges from 0.61 to 1. 35.