基于渔获量平均营养级的西印度洋渔业资源利用评价

Evaluation of fishery resources utilization in the western Indian Ocean based on mean trophic levels

西印度洋是世界上重要的作业海域,评价渔业资源利用状态是实现其资源科学管理和可持续开发的重要基础。根据联合国粮农组织(FAO)提供的1950—2018年西印度洋海域渔获量数据,结合渔获种类的营养级(trophic level,TL),分析69年间西印度洋海域渔获物平均营养级(mean trophic level,MTL)和营养级平衡指数(fishing in balance index,FiB)的变动情况,以此评价渔业资源的开发利用情况。研究表明,1950—2018年西印度洋海域渔获量呈上升趋势,按其渔获量增长趋势可划分为1950—1982年、1983—2005年和2006—2018年3个阶段,其中长头小沙丁鱼(Sardinella longiceps)渔获量最高。渔获物MTL呈先下降后上升再稳定的变动趋势,按渔获量增长趋势划分的3个阶段,其MTL分别为3.49±0.14、3.71±0.06和3.71±0.03,高营养级渔获物(TL>3.25)的MTL分别为4.04±0.04、4.09±0.04和4.13±0.01,高营养级渔获物(TL>3.25)的平均营养级与总渔获物的平均营养级变化趋势相似。FiB指数总体呈现上升趋势,3个阶段的平均值分别为0.0998±0.1659、0.8041±0.1849和0.9782±0.0670。分析认为:1950—1982年西印度洋海域早期渔获量相对较低,并随着长头小沙丁鱼等低营养级渔获量的增加,MTL和FiB呈波动下降趋势;1983—2005年,随着高营养级渔获量的增加,MTL和FiB呈逐渐升高趋势;2006—2018年,MTL和FiB相对稳定处在一个高位值。研究表明,目前西印度洋海域渔业资源状况良好,生态系统结构和功能稳定,该海域仍具有较大的开发潜力。

The West Indian Ocean is an important fishing area in the world.The evaluation of fishery resources utilization is an important basis for scientific management and sustainable development of the resources.According to the FAO’s catch data from 1950 to 2018 and trophic level of fish species in the western Indian Ocean,the mean trophic level(MTL)of 69 years and fishing in the balance index(FiB)were analyzed to evaluate the development and utilization of fishery resources.The results showed that the catch showed an increasing trend from 1950 to 2018 in the western Indian Ocean,and the increasing trend could be divided into three stages including 1950-1982,1983-2005 and 2006-2018.The catch of small sardines was the highest in the species from the western Indian Ocean.The MTL of the catch decreased first,then increased,and then stabilized during 1950 to 2018.According to the above three phases,its average MTL were 3.49±0.14,3.71±0.06 and 3.71±0.03 respectively,and the high MTL of the catches(TL>3.25)were 4.04±0.04,4.09±0.04 and 4.13±0.01 respectively.It is found that the average trophic level fromthe high MTL(TL>3.25)catch and total catch show the similar changing trend(P<0.001).The FiB index showed an upward trend on the whole,and the mean FiB of three stages were 0.0998±0.1659,0.8041±0.1849 and 0.9782±0.0670 respectively.According to the analysis,the early catch was relatively low in the western Indian Ocean from 1950 to 1982,and the MTL and FiB showed a fluctuating decreasing trend with the increase of the catch of low trophic level such as sardines.From 1983 to 2005,with the increase of high trophic level catch,MTL and FiB showed a gradually increasing trend.From 2006 to 2018,MTL and FIB were relatively stable at a high value.The results show that the fishery resources in the western Indian Ocean are in good condition,the ecosystem structure and function are stable,and the resources of western Indian Ocean still have great development potential.