自然死亡率变化对黄海蓝点马鲛渔业管理的影响

传统的渔业资源评估方法对数据有一定的要求,而现有的许多渔业缺乏相关数据,造成了渔业评估和管理上的障碍。特别是自然死亡率,由于观测和计算的困难,研究中一般通过经验公式等方法进行假话,而不同来源的数据和估算方法的结果存在较大差异,可能导致在渔业资源评估和管理中很大的不确定性。本研究以蓝点马鲛（Scomberomorus niphonius）为例,利用MSE比较了22种基于有限数据的渔业管理规程（MP）,筛选出DCAC、SPMSY、curE75、minlenLopt1 4种对于M不确定性较为稳健的的管理方法,并针对不同年代的自然死亡率以及通过不同计算方法得出的自然死亡率对这4种MP进行了管理策略评价。结果表明：M自1980s至今的不同年代间有显著降低趋势,该变化对MP管理效果产生了较强影响。随着M降低,种群B>0.5BMSY的概率显著上升,而过度捕捞可能性在不同MP间有方向性的差异。M变化对对curE75、minlenLopt1的长期产量的影响较小,而对DCAC、SPMSY的AAVY<15%的可能性变化较大,即降低产量的波动。不同M估算方法的估计值相差不大,对MP管理影响不明显。综合结果来看,Cur75受自然死亡率不确定性影响较小,对于渔业资源的开发和保护两个方面有着最好的权衡,最适用于我国蓝点马鲛渔业的管理。

The impact of natural mortality variations on the performance of management procedures for Spanish mackerel (Scomberomorus niphonius) in the Yellow Sea, China

Natural mortality rate (M) is one of the essential parameters in fishery stock assessment, however, the estimation of M is commonly rough and the changes of M due to natural and anthropogenic impacts have long been ignored. The simplification of M estimation and the influence of M variations on the assessment and management of fisheries stocks have been less well understood. This study evaluated the impacts of the changes in natural mortality of Spanish mackerel (Scomberomorus niphonius) on their management strategies with data-limited methods. We tested the performances of a variety of management procedures (MPs) with the variations of M in mackerel stock using diverse estimation methods. The results of management strategies evaluation showed that four management procedures DCAC, SPMSY, curE75 and minlenLopt1 were more robust to the changes of M than others; however, their performance were substantially influenced by the significant decrease of M from the 1970s to 2017. Relative population biomass (measure as the probability of B>0.5B_MSY) increased significantly with the decrease of M, whereas the possibility of overfishing showed remarkable variations across MPs. The decrease of M had minor effects on the long-term yield of curE75 and minlenLopt1, and reduced the fluctuation of yield (measure as the probability of AAVY<15%) for DCAC, SPMSY. In general, the different methods for M estimation showed minor effects on the performance of MPs, whereas the temporal changes of M showed substantial influences. Considering the fishery status of Spanish mackerel in China, we recommended that curE75 has the best trade-off between fishery resources exploitation and conservation, and we also proposed the potentials and issues in their implementations.