Many of the world’s fish stocks are depleted as a result of overexploitation, pollution and habitat loss. The 2002 World Summit on Sustainable Development (WSSD) sets a target for fisheries to maintain or restore stocks to levels that can produce the maximum sustainable yield (MSY) by 2015. We assessed the global stock status and found that 68% were at or above the MSY level in 2008 and that the 2015 target is unlikely to be met. We compiled data for eight indicators to evaluate the sustainability of fisheries and the gap to meet the WSSD target. These indicators show that the overall condition of global fisheries is declining, long‐term benefits are being compromised, and pressures on fisheries are increasing despite fisheries policy and management actions being taken by coastal States. We develop a bio‐economic model to estimate the costs and benefits of restoring overfished stocks. Our results show that the global fishing capacity needs to be cut by 36–43% from the 2008 level, resulting in the loss of employment of 12–15 million fishers and costing US$96–358 billion for buybacks. On the other hand, meeting the WSSD goal will increase annual fishery production by 16.5 million tonnes, annual rent by US$32 billion and improve biodiversity and functioning of marine ecosystems. However, progress towards rebuilding has been hindered by an unwillingness or inability to accept the short‐term socio‐economic consequences associated with rebuilding fisheries. Thus, there is a pressing need for integration of rebuilding plans into national political and economic decision‐making.
Trends in landings from global shelf areas (excluding the Arctic/Antarctic) for 1950-94 are expressed per shelf surface of FAO Statistical Areas in four categories: "shelfdependent" species (demersal fish plus commercial benthic invertebrates), "shelf-associated" species (small-medium sized pelagics and neritic squids), and "deep-water" and "oceanic" species; largely focusing on the first two categories. Geographical variation for shelf-dependent resources is explained by dividing FAO Statistical Areas into three categories: Arcto-boreal regions in the northern hemisphere, with five-year mean fishery production peaking at 2.1-2.7 tons per km 2 ; from the Antarctic convergence to south-boreal latitudes, with production peaking at 0.5-2.2 tons per km 2 , and tropical/subtropical shelves, peaking at 0.4-0.9 tons per km 2 (except for the Central East Atlantic). For zoogeographically similar areas, overall production levels for shelf-dependent resources have generally reached similar peak values and declined recently in areas with long histories of fishing. For several areas, especially in the tropics, production peaked in the last five-year period considered, 1990-94, but further potential for shelf-dependent species is considered limited. A low limit for shelf-dependent resources in the tropics of <1 tons per km 2 reflects peak production well inside 200 m, despite local highly productive coastal ecosystems. Mediterranean shelf-dependent production was at tropical/sub-tropical levels in the 1960s but has increased through the 43-year time series to 2.4 tons per km 2 , similar to north-boreal shelves. As for other inland seas, this increase probably represents, at least in part, nutrient runoff effects on marine production. The upper limit for shelf-associated resources is more variable than for shelf-dependent resources and may be an index of biological productivity. Production of small-medium pelagic fish is considered loosely correlated with shelf-dependent production, and in Arctoboreal regions may be dependent on nutrients from shelf water mixing, while high shelf pelagic production is confined to upwelling regimes. Globally, the recent rate of production increase for oceanic and deep-water species exceeds that for shelf resources, pointing to the recent diversion of effort to offshore areas. The apparent difference in shelf-dependent production in similar North and South temperate areas is suggested to be due to a greater "land effect", roughly estimated at some 1.00-1.5 tons per km 2 for comparable levels of production of small pelagics. This difference is postulated as due to increased nutrient runoff and/or larval retention on northern than the more exposed southern hemisphere shelves, and an analogy is drawn between effects of excessive "natural eutrophication" and that due to anthropogenic causes. Although nutrients may constrain local production, resources closely linked to continental shelves are overfished or potentially so, and recovery will only be achievable by better management. One estimate derived...
Fishery ecosystems are complex and influenced by various drivers that operate and interact at different levels and over multiple scales. Here, we propose a holistic methodology to determine the key mechanisms of fisheries, trophodynamics, and environmental drivers of marine ecosystems, using a multilevel model fitted to data on global catch, effort, trophic level, primary production, and temperature for 130 ecosystems from 1950 to 2012. The model describes the spatial‐temporal dynamics of world fisheries very well with a pseudo R2 = 0.75 and estimates the effects of key drivers of fishery production. The results demonstrate the integrative operation of bottom‐up and top‐down regulated trophic interactions at the global level and great variations in their relative importance among different types of ecosystem. The estimation of key drivers’ effects on marine ecosystems provides practical mechanisms for informed ecosystem‐based fisheries management to achieve the sustainable objectives that are consistent with the needs of specific fisheries.
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