应用世代分析法估算鱼类自然死亡率的初步研究

A Preliminary Study on the Estimation of Natural Mortality Using Cohort Analysis Method

根据已开发鱼类种群的自然死亡率(M)在鱼类资源评估中的重要作用,讨论了1种应用实际种群分析(VPA)(亦即世代分析方法)估算鱼类自然死亡率的方法。文中假设了捕捞努力量(E)已知和未知2种情况,并同时求出了其他种群参数,如可捕系数,补充量等。在蒙特卡罗模拟分析中,假设了4种模拟渔业(管理良好的渔业,掠夺式渔业,恢复性渔业和稳定性渔业)对该方法进行了验证。并将von-Bertalanffy生长方程(VBGF)引入VPA模型来估算鱼类的自然死亡率。当C V等于20%时,在4种模拟渔业中鱼类各龄自然死亡率(Ma)的EP均小于10%。在已知单位捕捞努力量渔获量数据时,计算北大西洋长鳍金枪鱼(Thunnus alalunga)的M等于0.119,这个结果比先前假定的值(0.3)小,但考虑到该鱼种所承受的高的捕捞压力作者认为该估计值是合理的。

Catch-at-age data combined with and without the auxiliary information of effort data were used to calculate natural mortality rate （M） and the other population parameters such as catchability and recruitment. The method used in the paper was the standard statistical virtual population analysis （VPA） model. Monte Carlo simulation data were used to test this method under four fishery scenarios （good contrast, oneway trip, recovery and status quo）. When supposing M varied with age, the von-Bertalanffy growth function （VBGF） was introduced into the statistical VPA model. When the CVs were 10% the EPs of the estimated Ma were lower than 10% for the four simulated fisheries. The method was also applied to the published data of North Atlantic albacore （ Thunnus alalunga ）, and the estimated M was 0. 119, which was lower than previously assumed （0.3） and may be viable in view of the high fishing effort imposed on the species.