Coastal fishery resources in South and Southeast Asia: analysis of stock declines and trophic (ecosystem) dynamics
2003
Garces, L.R. | Silvestre, G.T.
Based on resource analyses resulting from an 8-countries regional collaborative research effort (which has collated data from over 20,600 research trawl survey hauls across the South and Southeast Asian region), substantive degradation and overfishing of coastal fish stocks in the areas covered by the studies have been noted. The population analyses indicate that catch rates and (hence) resource biomass have declined to 8-31% of original ("baseline") biomass levels in the fishery areas studied. The exploitation ratios (E) of the most abundant species confirm the trend of massive resource biomass decline. It is noted that a considerable number of species are exploited beyond the optimum range, resulting in mean E`s of the multispecies resource mix also being beyond the optimum range. The massive decline in resource biomass (due to excessive fishing pressure) has led to substantive changes in species composition of the coastal fishery resources. Evident trends in species composition changes sites covered by the analyses indicate that larger, more valuable species (e.g., groupers, snappers, sharks and rays) high up in the food chain have declined in relative abundance. Comparatively, small species and generalists (e.g., triggerfish, cardinal fishes, squids/octopus) low in the food chain have increased in relative abundance. These trends in species composition changes may indicate recruitment and ecosystem overfishing due to the excessive fishing effort in these areas. Preliminary Trophic models of coastal fishing systems constructed using Ecopath for areas covered by the resource/ecosystem analyses included 11 to 40 groups with mean trophic levels ranging from 2.61 to 3.25.
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