非洲沿海国家海洋渔业资源开发利用现状

根据联合国粮农组织提供的1950-2015年非洲渔获生产统计数据，结合Fishbase提供的相关鱼种营养级（Trophic level, TL）以及Sea Around Us Project Database提供的海洋无脊椎动物营养级，探讨了1950-2015年北非、东非、南非、中非和西非的沿海国家渔获物平均营养级（Mean trophic level, MTL）的变化情况，以此来判定非洲沿海国海洋渔业资源的开发利用现状。结果表明：非洲沿海国家的海洋渔业资源开采大致经历开发不足、快速开发、过度开发阶段，1984-1991年，北非地区的海洋渔业资源遭到一定程度的破坏，高营养级渔业资源渔获量减少了33.5%，MTL由3.44降低到3.25；东非地区渔获量较其他4个区域低，目前，大部分鱼类资源处于充分捕捞利用状态；南非地区在21世纪初发生“捕捞降低海洋食物网”现象，2004-2015年，MTL恢复小幅上升趋势，渔业均衡指数（Fishing-in-balance index, FIB）趋于平稳；2013-2015年，中非地区的MTL与FIB均呈下降趋势，说明产量的增加速度不足以弥补营养级的降低，生态系统结构功能开始遭到破坏；1950-2015年，西非地区的渔获量不断增加，从上世纪60年代开始，过度捕捞现象愈加严重，低营养级鱼类数量占比呈先减少后增加趋势，2001-2012年，MTL波动下降，FIB平稳变化，说明MTL的下降由产量的增加而抵消。21世纪以来，部分北非、南非与西非沿海国家加强了资源管理，渔业资源状况有所好转。研究认为：渔获物平均营养级的下降主要由过度捕捞引起，非洲国家的管理不力加重了过度捕捞现象，建议非洲各国尽快建立起基于渔获物统计的海洋渔业资源实时监测系统，以便掌握捕捞活动下的鱼类群落结构的变动情况。

Evaluation Utilization State of Marine Fishery Resources of Africa

Evaluation utilization state of marine fishery resources of Africa is of great significance in promoting the sustainable development of fisheries in Africa and the cooperation between China and Africa. Based on the capture production data provided by Food and Agriculture Organization of the United Nations, integrating with trophic level of related fish species collected from Fishbase and trophic level of invertebrate provided by Sea Around Us Project database, in order to estimate fluctuations in the mean trophic level (MTL) of catch and the state of fishery resources of African coastal countries from 1950 to 2015. Results showed that the exploitation of marine fishery resources in African coastal countries has generally experienced the stages of underdevelopment, rapid development and over-exploitation. From 1984 to 1991, the marine fishery resources in North Africa have been damaged to a certain extent, the capture production of high-grade trophic fishery resources decreased by 33.5%, MTL decreased from the peak value 3.44 to 3.25; The catch of East Africa has been relatively low for a long time, nowadays, most of the fish resources are fully exploited. Fisheries in South Africa followed the phenomenon of ‘fishing down marine food webs’ in the early 21st century, MTL first went through a fluctuation growth trend during the period 1950-1996, then a relatively slow decreasing process during the period 1997-2004, and afterwards MTL recovered slight increasing trend, Fishing-in-balance index (FIB) kept steady from 2004 to 2015; MTL and FIB of Middle Africa declined in volatility in recent 3 years，indicated that the rate of increase in production is not sufficient to compensate for the reduction in the trophic level, and the structure and function of the ecosystem begins to be destroyed; The capture production in West Africa continued to increase in the past 66 years, overfishing has become more and more serious since the 1960s and led to a growth trend of the proportion of low trophic level fish. From 2001 to 2012, FIB was almost constant and between 1.2 and 1.4, MTL decreased fluctuatingly. When we compute MTL based on time-series of data that exclude trophic levels lower than 3.25(3.25MTL) so that to eliminate herbivores, detrivores and planktivores whose biomass trends to vary widely in response to environment factors. 3.25MTL showed a rising trend, suggesting that the decline of MTL was offset by the increase of production, overfishing led to an increase in the number of low and middle trophic fish in the sea area. Since the 21st century, some North African, South African and West African coastal countries have strengthened their fishery resources management and protection. The reduction in MTL indicates that the structure and function of the marine ecosystem has been destroyed, as changes in MTL are mainly caused by overfishing. We recommend that each country should establish a monitoring system which based on the capture production data to better assess the dynamic change of resources under fishing activities.