关键词: 非洲沿海国家, 可持续利用, 渔获物平均营养级, 渔获统计

Abstract:

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.

Key words: African coastal states, sustainable utilization, mean trophic level, fishery statistics