自然死亡和亲体补充关系对黄鳍金枪鱼资源评估的影响

黄鳍金枪鱼（Thunnus albacares）是全球经济和生态价值最重要的鱼类之一,其资源养护和管理受到各方的高度关注。本文依据年龄结构产量模型研究了印度洋黄鳍金枪鱼的资源状态,着重探讨了其生活史特征的不确定性对资源评估结果的影响。研究结果显示,1960−1985年间印度洋黄鳍金枪鱼资源量保持相对稳定,之后开始逐渐下降,相应的捕捞死亡系数也在2010年之后迅速增加,目前其种群可能存在过度捕捞（F₂₀₂₀/F_MSY>1,SSB₂₀₂₀/SSB_MSY<1）。印度洋黄鳍金枪鱼的资源评估结果对自然死亡系数（M）和亲体−补充量关系陡度参数（h）的改变较为敏感。当h增大时,SSB_MSY和初始SSB（即SSB₀）的变化较大,分别减少了约25.53万t和34.04万t;F₂₀₂₀/F_MSY减小了1.15。当M增大时,F₂₀₂₀/F_MSY、SSB_MSY、SSB₀均减小。综上所述,今后应重视印度洋黄鳍金枪鱼资源的开发程度,重视其资源养护管理,同时充分了解黄鳍金枪鱼的生活史特征,提高自然死亡系数和陡度参数估算的准确性,以期为印度洋黄鳍金枪鱼的资源评估和渔业管理提供更准确的信息,实现该渔业的长期可持续发展。

Influence of natural mortality and stock-recruitment relationship on yellowfin tuna (Thunnus albacares) stock assessment

Yellowfin tuna (Thunnus albacares) is one of the most important fishes with great global economic and ecological value, and its conservation and management have received much concerns. The stock status of yellowfin tuna in the Indian Ocean based on the age-structured assessment program model is evaluated in this study, focusing on the uncertainties of its life history characteristics on the stock assessment results. The results show that the resources of yellowfin tuna in the Indian Ocean remained relatively stable from 1960 to 1985 and then declined gradually, while the fishing mortality coefficient F increased rapidly after 2010. This stock in 2020 may be overfished, since the estimated F₂₀₂₀ was greater than F_MSY (F that could attain maximum sustainable yield MSY), while spawning stock biomass, SSB₂₀₂₀ was less than SSB_MSY. Sensitivity analysis was also conducted to evaluate the uncertainties of stock assessment. Two important life history characteristics, natural mortality M and steepness of spawning-stock relationship h, were analyzed for their influence on the estimates of F, SSB and biological reference points. When h was set to 0.7, 0.8, and 0.9, SSB_MSY and SSB₀ (the unfished SSB) reduced by about 255 300 t and 340 400 t; and F₂₀₂₀/F_MSY gradually decreased (from 2.88 to 2.21 and 1.73). When the M was set to M₁ (0.963, 0.663, 0.548, 0.493, 0.463, 0.446) and M₂ (1.068, 0.735, 0.608, 0.547, 0.514, 0.495) respectively, the larger M₂ leads to lower SSB and F₂₀₂₀/F_MSY. In summary, the conservation and management of Indian Ocean yellowfin tuna should be tightened in the future to achieve long-term sustainable development of this fishery. The life history characteristics of yellowfin tuna should be fully understood, especially M and h estimation should be improved, to provide more accurate information for stock assessment and fisheries management for Indian Ocean yellowfin tuna.