淀山湖刀鲚的生物学参数估算及其相对单位补充量渔获量

Estimation of biological parameters and yield per recruitment for Coilia nasustaihuensis in Dianshan Lake,Shanghai,China

刀鲚是淀山湖水域内资源丰度最高的鱼类,在该湖泊的生态系统中处于重要地位.本文根据2010年7月至2011年8月在淀山湖水域采集的3107尾刀鲚的长度频率数据,利用ELEFAN I技术对刀鲚的生长和死亡参数进行估算,并根据Beverton-Holt动态综合模型评估刀鲚资源变动趋势.结果表明:von Bertalanffy生长方程描述的刀鲚生长参数为L∞=35.70cm,k=0.54,t0=-0.48 a,体质量的生长拐点年龄为1.37 a.采用Pauly经验公式估算出刀鲚的自然死亡系数M=0.872.采用长度变换渔获曲线法估算刀鲚的总死亡系数Z=2.121,捕捞死亡系数F=1.249,当前开发率E=0.589,表明资源已处于过度开发状态.根据Beverton-Holt动态综合模型,建议最适的开捕体长应为21.42 cm,对应开捕年龄为1.22 a.

Coilia nasustaihuensis is the most abundant species in Dianshan Lake and plays an mlportant role in the lake ecosystem. From July 2010 to August 2011, a total of 3107 samples of C. nasustaihuensis were collected from Dianshan Lake. Based on length data of these samples, ELEFAN I technique was employed to estimate growth and mortality parameters, and the Beverton-Holt dynamic model was used to evaluate the population dynamics trend for C. nasustaihuensis. Growth of this species was described using a yon Bertalanffy model, and the estimated parameters were L∞ =35.70 cm, k=0. 54, and to =-0.48 a. The turning point for body mass growth curve of the stock was situated at t = 1.37 a. Natural mortality coefficient M was then estimated using Pauly＇ s empirical equation and found to be 0. 872. Length-converted catch curves were used to estimate the total mortality coefficient Z, which was found to be 2. 121. Accordingly, the fishing mortality coefficient （F） was equal to 1. 249, and the current exploitation rate was 0. 589, suggesting the stock was over-exploited. According to the Beverton-Holt dynamic model, the minimum capture size for C. nasustaihuensis should be 21.42 cm （ age 1.22 years）.