黄海南部和东海小黄鱼资源动态的比较

Comparative population dynamics of small yellow croaker Larimichthys polyactis in Southern Yellow Sea and East China Sea

根据2006—2007年底拖网调查资料,利用体长频率法估算了黄海南部和东海小黄鱼Larimichthys polyactis种群的生长、死亡参数,比较了两海域小黄鱼资源变动的空间特征差异,并利用动态综合模型分析了小黄鱼资源的利用状况。结果表明:黄海南部和东海小黄鱼种群渔获年龄主要为0~1+a,以当龄鱼(0 a)为主;平均极限体长(L∞)分别为226.47、257.25 mm,平均生长速度(K)分别为0.39/a、0.43/a,理论生长起点年龄(t0)分别为-0.80 a、-0.31 a;总死亡系数(Z)分别为1.81/a、3.05/a,捕捞死亡系数(F)分别为1.42/a、2.62/a,东海种群的捕捞强度大于黄海南部种群。渔获概率分析显示:黄海南部种群渔获概率为25%、50%和75%的选择体长分别为103.6、112.4、121.2 mm,东海种群分别为110.5、122.4、130.5 mm,东海种群的开捕体长稍大于黄海南部种群。动态综合模式分析表明,黄海南部种群资源利用参考点E0.1(单位补充量渔获量曲线初始斜率为10%时的开发率)、E50%(资源量为初始资源量50%时的对应开发率)、E max(最大产量时的对应开发率)分别为0.560、0.386和0.649,东海种群分别为0.563、0.356和0.669,当前开发率已经超过了目标参考点E0.1,资源处于过度利用状态。

Growth parameters( L ∞ and K) and mortality coefficients( Z,M and F) of small yellow croaker Larimichthys polyactis populations were estimated in the coastal waters of Southern Yellow Sea( SYS) and East China Sea( ECS) from January 2006 to December 2007 by length distribution data collected by trawl survey. The current exploitation status and rational utilization of the small yellow croaker resources were evaluated by target reference point calculated through modified Beverton-Holt dynamic pool model. The Bhattacharya's analysis revealed that the age composition of the small yellow croaker was 0 year and 1+year,dominated by the group of 0 year. Fitting the von Bertalanffy growth function to these data showed asymptotic length( L ∞) of 226. 47 mm and 257. 25 mm,curvature parameter( K) of 0. 39 and 0. 43 per year,and initial condition parameter,( t 0) of-0. 80 a and-0. 31 a for the SYS and ECS population,respectively. Total mortality coefficients was found to be 1. 81 per year in SYS and 3. 05 per year in ECS population,fishing mortality coefficients 1. 42 per year in SYS population and 2. 62 per year in ECS population,higher capture intensity in ECS population than that in the SYS population. The estimated length at different probability of capture was found to be L 0. 50 = 112. 4 mm,L 0. 25 = 103. 6 mm,and L 0. 75 = 121. 2 mm in the SYS population and L 0. 50 = 122. 4 mm,L 0. 25 = 110. 5 mm,and L 0. 75 = 130. 5 mm in ECS population,higher in the ECS than that in the SYS. Dynamic pool models showed that the small yellow croaker population in the SYS had prevailing E 0. 1( developing rate at 10% of the initial increment,0. 560),E 50%( developing rate at 50% of the initial increment,0. 386) and E max( developing rate at the maximal yield,0. 649),and that the small yellow croaker population showed in E 0. 1 of 0. 563,E 50% of 0. 356 and E max of 0. 669 in the ECS,indicating that the stock was overexploited due to above prevailing E 0. 1.