基于渔获量平均营养级的东印度洋渔业资源可持续利用评价

渔业资源可持续利用是渔业经济可持续发展的基础。本文根据联合国粮农组织提供的1950?2018年东印度洋渔业生产统计数据，结合Fishbase提供的相关鱼种的营养级，探讨了69年间东印度洋渔获量平均营养级(MTL)以及营养级平衡指数的长期变化趋势，以此来判定其渔业资源可持续利用状况。研究认为，1950?2018年东印度洋渔获量呈现稳步增长趋势，其中云鲥(Tenualosa ilisha)、鲱鱼(Clupea pallasi)、印度鲭(Rastrelliger kanagurta)为重要渔获种类，其累计年产量占总产量的比重均在10%以上。MTL变动大致可分3个阶段:1950?1974年渔获MTL总体处在高位，其值范围为3.39～3.71，平均值为3.60±0.07，期间年渔获量呈现稳定的增长趋势，平均年增长率为6.4%；1975?1999年渔获MTL呈现波动，其值范围为3.21～3.51，平均值为3.35±0.08，期间年渔获量呈现稳定的小幅度增长趋势，平均年增长率为4.8%；2000?2018年渔获MTL年间波动较小，其值为3.31～3.43，平均值为3.38±0.03，期间年渔获量呈现缓慢稳定的增长趋势，平均年增长率为1.6%。3个阶段的平均营养级平衡指数分别为0.59±0.22、0.94±0.14、1.25±0.04，其值呈现稳定的增长趋势且年间变化幅度越来越小，说明其群落结构越来越趋稳定。渔业资源的开发利用程度增加，而MTL下降程度较小，营养级平衡指数呈现上升趋势，说明渔获量的增加能够弥补MTL的下降；且仅统计营养级大于3.25的种类时，1950?1974年、1975?1999年、2000?2018年3个阶段的MTL平均值分别为4.16±0.04、4.18±0.04、4.19±0.03，呈现小幅稳定增长的趋势，表明高营养级种群渔业资源未受到破坏。研究认为，东印度洋海洋生态系统稳定，高营养级种群渔业资源处于未充分开发状态。

Evaluation of sustainable utilization of fishery resources in the Eastern Indian Ocean based on the mean trophic level

The sustainable utilization of fishery resources is the basis of resources exploitation. Based on the statistical data of catches in the East Indian Ocean from 1950 to 2018 provided by the food and agriculture organization of the united nations, and combined with the trophic level (TL) of relevant fish species provided by Fishbase, the changes of mean trophic level (MTL) and fishing-in-balance (FiB) index of catch in the East Indian Ocean during 69 years, so as to determine the sustainable utilization of fishery resources in the Eastern Indian Ocean were discussed in this paper. The results showed that the catches in the East Indian Ocean showed a steady increasing trend from 1950 to 2018. The catches of Tenualosa ilisha, Clupea pallasi and Rastrelliger kanagurta were the important catch species in the East Indian Ocean from 1950 to 2018, and their cumulative annual yield accounted for more than 10% of the total catch. The variation of MTL could be divided into three stages: from 1950 to 1974, the MTL was high and its value range was 3.39?3.71 with the average of 3.60±0.07, the annual catch showed a steady increase trend, the average annual growth rate was 6.4%; from 1975 to 1999 the annual MTL fluctuated from 3.21 to 3.51 with an average of 3.35±0.08, the annual catch showed a small and steady increase trend, the average annual growth rate was 4.8%; during 2000 to 2018, the annual MTL from 2000 to 2018 was 3.31?3.43, with an average of 3.38±0.03, and the annual catch showed a slow and steady increasing trend, with an average annual growth rate of 1.6%. The mean FiB index of the three stages was 0.59±0.22, 0.94±0.14 and 1.25±0.04, respectively. The value of FiB index showed a steady increasing trend and the range of annual variation was smaller, which indicated that the community structure in the East Indian Ocean was becoming more and more stable. The degree of development and utilization of fishery resources increased, while the decline in MTL was small, and the FiB index showed an upward trend, indicating that the increase in fish catches could make up for the decrease of MTL; and when only populations with TL greater than 3.25 were counted, the average MTL values of 1950?1974, 1975?1999, and 2000?2018 were 4.16±0.04, 4.18±0.04, and 4.19±0.03, respectively, showing a small and stable increase trend, indicating that the fishery resources of the high-trophic population were not damaged. It is concluded that the marine ecosystem of East Indian Ocean is stable and the fishery resources are under-exploited.