A MODULAR STRATEGY FOR RECOVERY AND MANAGEMENT OF BIOMASS YIELDS IN LARGE MARINE ECOSYSTEMS

摘要

During the decade since the 1992 United Nations Conference on Environment and Development, considerable movement has been made by international organizations engaged in ocean affairs to move nations toward adopting ecosystem-based assessment and management strategies. The 191 nations, including 82 heads of state, participating in the 2002 World Summit on Sustainable Development in Johannesburg agreed to a plan of implementation (POI) that encourages nations to apply the ecosystem approach to marine resource assessment and management practices by 2010, and maintain or restore fish stocks to levels that can produce maximum sustainable yield levels by 2015. To achieve these targets will require an improved understanding and assessment of the effects of physical, biological and human forcing causing changes in biomass yields of large marine ecosystems (LMEs). An international financial mechanism, the Global Environment Facility (GEF), is assisting developing countries in meeting the Summit targets by supporting LME assessment and management projects. Of the 29 LMEs for which published case study information is available for analyses of principal forces driving changes in biomass yields, fishing effort was the primary forcing mechanism in 14 LMEs; climate forcing was the principal factor in 13 LMEs, eutrophication in one case and the data were inconclusive in another. Fishing effort was a secondary driver of change in biomass yields in the LMEs driven by climate forcing. Mitigating actions for reducing fishing effort to promote recovery of lost biomass yield is proving successful in one case study. Actions for improving forecasts of oceanographic conditions affecting fish stocks are underway in four GEF supported LME projects (e.g. Humboldt Current, Canary Current, Guinea Current, Benguela Current); measures to assess and manage excessive fishing effort are planned for 8 LME projects, eutrophication reduction and control in another, and 6 LMEs with relatively stable decadal biomass yields appear suitable for mandating precautionary total allowable catch (TAC) levels. The GEF-LME projects include countries that contributed to 45% of global marine biomass yields in 1999.