Changes in the trophic structure of fish demersal communities in West Africa in the three last decades
Changes in the trophic structure of fish demersal communities in West Africa in the three last decades
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DOI：
10.1051/alr:2004023
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发表时间：
2004-04-01
影响因子：
1.1
通讯作者：
Thiam, D
中科院分区：
文献类型：
--
作者：
Laurans, M;Gascuel, D;Thiam, D
西非海洋生态系统生产力非常高，维持着过去几十年快速发展的重要渔业。捕捞对石油开采资源影响的分析通常通过单一物种评估进行。在这项研究中，我们提出了一种补充方法，可以解释捕鱼对生态系统的一些影响。在几内亚和塞内加尔，渔业最近才发展起来，同时也进行了上岸和调查数据的收集。因此，数据收集从种群可被视为未开发的时期延伸到过度开发的情况。本案例研究的分析是为了检测生态系统结构因捕捞压力增加而发生的变化。为此，对底层鱼类群落的营养谱和平均营养水平的长期序列进行了检查。营养光谱显示底层群落生物量的分布或根据营养级别类别的商业渔获量。塞内加尔和几内亚生态系统的营养结构发生了一些实质性的、统计上显着的变化。特别是，高营养级的生物量减少，而低营养级的生物量表现出相对稳定或增加。这可能与“自上而下”的捕捞效应有关，因为对底层鱼类群落的较低营养级的捕食得到了释放。在塞内加尔，渔获量和底层群落生物量的平均营养水平显着下降。几内亚沿海底层生物量也出现了这种减少。这表明捕捞活动对生态系统的营养结构产生了影响，西非首次出现了“海洋食物网捕捞”效应。
West African marine ecosystems are very productive and sustain important fisheries that have developed rapidly in the last decades. The analysis of the fishing impact oil exploited resources is usually conducted through single-species assessments. In this study, we propose a complementary approach that enables to account for some ecosystem effects of fishing. In Guinea and Senegal, fisheries have developed relatively recently and at the same time, the collection of landings and surveys data has been carried out. In consequence, the data collection extends from a period where stocks Could be considered as non exploited to a situation of overexploitation. This case study is analysed in order to detect shifts in the ecosystem structure in response to increasing fishing pressure. To this aim, trophic spectra and long time series of mean trophic level are examined for demersal fish communities. Trophic spectra display either the distribution of the demersal community biomass or the commercial catches according to trophic level classes. Some substantial and statistically significant changes in the trophic structure of the Senegal and Guinea ecosystems were observed. In particular, the biomass of the high trophic levels decreased whereas the lower trophic levels displayed a relative stability or an increase. This could be linked to a "top-down" fishing effect due to a release of predation on the lower trophic levels of the demersal fish community. In Senegal, the mean trophic level decreased significantly for both the catches and the demersal community biomass. Such a decrease was also observed for the coastal demersal biomass in Guinea. This showed that fishing activities had an impact on the trophic structure of the ecosystem, and a "fishing down marine food web" effect was shown in West Africa for the first time.