| As the important part of natural resources,marine fishery resources play a critical role in supporting human well-being,from global food security to economic and social development.Global marine fisheries supply the world with approximately 80 million tonnes of protein and micronutrient rich food for human consumption per year,and these fisheries also provide employment and income for human society.Marine fisheries provide full-time and part-time jobs to an estimated 260 million people,and a large fraction of these are fishers engaged in small-scale fisheries.In addition,marine fisheries support global economies with an estimated gross revenues of US$ 80-85 billion annually.With the improved technology and increasing demand,marine fisheries have undergone significant changes over the past 60 years with rapid geographical and bathymetric expansion.High fishing intensity has resulted in up to one-third of global fisheries being overexploited or collapsed.Many of the world's fish stocks are depleted indicate that marine ecosystem is facing a severe test.Fishery sustainability has been commonly evaluated all over the world to ensure a continuous contribution of fisheries to the global food security,economic and social development.Based on the landing data in 1950-2010 and the trophic information of relevant species,we evaluated the status of marine fisheries in the FAO fishing areas and coastal states of Atlantic,Pacific and Indian Oceans,and further evaluated the mechanism of changes in mean trophic level of fisheries landings(MTL).Using price information obtained from Sea Around Us project database,we analyzed the catch trends and approximate thresholds of sustainable fishing for fished stocks to estimate the potential loss of catch and revenue of global fisheries as a result of overexploitation.In addition,we integrated marine fishery development with social,economic and environmental factors.Specifically,we examined how economic prosperity and population growth affected the sustainability of marine ecosystems,and assessed fisheries vulnerability to climate change.This study aims to provide a scientific basis for a better understanding of the status of global marine fisheries.The results were summarized as follows:(1)Evaluation on sustainable utilization of marine resources in the FAO fishing areas of Atlantic,Pacific and Indian Oceans.The global MTL declined at a rate of 0.057 per decade during 1955-1986,and the mechanism of change in MTL belonged to the “fishing through” pattern.Regional analysis showed that the descending trends of MTL showed in 10 of 14 FAO fishing areas,of which Northwest Atlantic,Northeast Atlantic,Southwest Atlantic and Southwest Pacific had the “fishing-down” phenomenon,and MTL decreased at a rate of 0.24(during 1965-2010),0.064(during 1969-1992),0.12(during 1996-2010)and 0.16(during 2000-2010)per decade respectively.Eastern Central Atlantic,Southeast Atlantic,Eastern Indian Ocean,Northwest Pacific,Eastern Central Pacific and Southeast Pacific had the “fishing-through” phenomenon,and MTL decreased at a rate of 0.040(during 1982-2010),0.18(during 1950-1963),0.08(during 1952-1987),0.17(during 1963-1988),0.065(during 1964-2010)and 0.18(during 1952-1985)per decade respectively.No decrease in the MTL did not necessarily indicate that fisheries have been properly managed.Western Central Atlantic,Western Indian Ocean,Northeast Pacific and Western Central Pacific all had increasing trend of MTL,but for the Western Central Atlantic,lower trophic level catches showed a strong declining trend since 1984 and upper trophic level catches also gradually decreased from 1998 to 2010.A declining trend of lower trophic level catches was also observed in the Northeast Pacific since 1987.MTL in the Southeast Atlantic Ocean almost stable since 1972,but both upper and lower trophic level catches significantly declined,fisheries development pattern in this area belonged to “increase to overfishing” scenario.In addition,the recovery trend of MTL may be accompanied by decreasing catches of lower trophic level species.Specifically,MTL for the global,Northeast Atlantic and Northwest Pacific Oceans reversed to a clear and steady upward trend after experiencing a significant decline,but lower trophic level catches in these areas all significantly declined.MTL may be affected by the behavior of fishermen and market.When fishing efforts transfer to invertebrates with a high trophic level such as cephalopods,“fishing-down” effect tended to be masked.We concluded that MTL used as an indicator to measure fishery sustainability can benefit from a full consideration of both upper and lower trophic level species and masking effects of community structure and exploitation history.(2)Evaluation on sustainable utilization of marine resources in global coastal states.The phenomenon of “fishing down marine food webs” occurred in 43 of 75 states.Specifically,27 states belonged to “fishing-through” pattern,and 16 states occurred “fishing-down” scenario.In terms of geographic distribution of the 43 coastal states that showed evidence of substantial declining of MTL,15 states located in Europe,of which United Kingdom,Belgium,Germany,Denmark,Netherlands,Poland,Finland,Sweden,France and Ireland had the “fishing-down” phenomenon,while Portugal,Spain,Iceland,Norway and Russia had the “fishing-through” phenomenon.Six states located in North America,of which Canada and Costa Rica had the “fishing-down” phenomenon,while US,Mexico,Bahamas and Greenland had the “fishing-through” phenomenon.Seven states located in South America,of which Uruguay and Argentina had the “fishing-down” phenomenon,while Columbia,Ecuador,Chile,Peru and Venezuela had the “fishing-through” phenomenon.In Africa,only South Africa,Liberia,Cameroon and Egypt showed evidence of descending trends of MTL,and all of them belonged to “fishing-through” scenario.In Asia,MTL in Japan,South Korea,China,Malaysia,India,Saudi Arabia,Yemen,Oman and Sri Lanka all exhibited a significant downward trend,but only Japan occurred “fishing-down” pattern.Two states located in Oceania,of which Australia had a significant “fishing-through” effect,and New Zealand had a “fishing-down” phenomenon.The sign of recovery in MTL were occurred in 20 states,but were generally accompanied by significantly decreased catches of traditional low trophic level species.In particular,11 states showed significant declining catches of lower trophic levels,there were located in Europe(Portugal,Spain,Sweden,Russia,Iceland,Norway and Netherlands),South Africa(Chile and Ecuador),and Asia(Japan and South Korea).Globally,states which had “fishing down” signs or showed declining catches of lower trophic level during the recovery period were mostly classified as developed states with low undernourishment.In contrast,states with increasing trends in MTL or occurrence of “fishing through” scenario with continuous increased catch of both upper and lower trophic levels of species were mostly classified as developing states with high undernourishment.Sustaining the contribution of seafood to the world food security requires that both developed countries and developing countries govern their resources effective in the face of increasing pressure from international trade.(3)Estimation of catch and revenue losses resulting from overexploitation in the global marine fisheries.About 35% of stocks in the global marine ocean have or had suffered from overexploitation at present.The global catch losses amounted to 332.8 million tonnes over 1950-2010,resulting in a direct economic loss of US$ 298.9 billion(in 2005 constant US$).Summing over the whole study period of 1950-2010 for each fishing area,Southeast Pacific was the first fishing area to register significant losses of about 115.07 million tonnes,followed by Southeast Atlantic,Northwest Atlantic and Northwest Pacific for losses of 62.16,50.44 and 48.24 million tonnes,respectively.In contrast,Southwest Pacific,Western and Eastern Indian Ocean did not suffer serious loss to overfishing with the overall potential loss being only about 0.96,0.35 and 0.41 million tonnes respectively.By estimate the potential revenue lost due to overfishing in each fishing areas from 1950 to 2010,results showed that Northwest Atlantic,Southeast Pacific,Northwest Pacific,Southeast Atlantic,and Northeast Atlantic reached $96.6,$56.1,$39.6,$38.3 and $17.6 billion,respectively.In contrast,the estimated loss in revenue for Southwest Pacific and Indian Ocean were relatively low,only between $0.4-3.2 billion.Lost revenue in other fishing areas ranged from $5.0 million to $10.7 million.Different components of community structure had very different exploitation status.Summing over the whole 14 fishing areas,we found that small-medium pelagcis ranked the 1st with a weight of 265.04 million tonnes.Followed by demersal fishes,invertebrates,and oceanic & deep-water resources,at 43.05,20.53,and 4.22 million tonnes respectively.The geographic expansion of overfishing not only showed serial depletion of world's fishery resources,but also reflected recent trends towards sustainability can stabilize or reverse catch losses.Reduction of global fishing capacity and improvement in fishery management are needed if the long-term sustainability of marine fisheries in the world is to be achieved.(4)Effects of social economic structure on global fisheries sustainability.We used the Environmental Kuznets Curve(EKC)theory to investigate the ecological consequences of economic prosperity and population growth by conducting cross-national time-series analyses(1970–2010)of 122 nations.The results showed that the EEZ catch,%PPR,and L index values increased and MTL decreased as economic growth increased in the early stages of economic development.However,EEZ catch,%PPR,and L index declined gradually after GDP per capita reached $15,000,$14,000,and $19,000 respectively,and MTL increased steadily once GDP per capita exceeded $20,000.These relationships suggest that increased affluence lead to reduced impact on marine ecosystem,which support ecological modernization theorists and the EKC hypothesis.Human population size had a significant and positive effect on EEZ catch,%PPR,and L index,and a clear negative relationship with MTL.Specifically,a doubling of human population caused an increase in the %PPR of 17.1% and L index of 0.0254,and a decline in the MTL of 0.176;and 1% increase in human population resulted in a 0.744% increase in EEZ catch.This is an expected outcome following the logic that the larger a nation's population the greater its impact on marine ecosystems.Most of the world's nations felt to the left side of EKC curve.This implies that economic growth in nations is likely to escalate ecosystem degradation globally.However,GDP per capita in some nations have passed the EKC curve threshold,where further development tends to halt the ecosystem-degradation trend.These results highlight the importance of considering social and economic factors in developing sustainable fisheries management policy.(5)Vulnerability to impacts of climate change on marine fisheries and food security.This study first systematically assessed the comparative magnitude and distribution of potential food security impacts of climate disturbance at a global scale,and highlight the contribution of marine fisheries to national food security.Our analysis suggested that country-level vulnerability to marine fisheries-related food security risks as a result of changing climate closely paralleled the national development status,with developing countries in Africa,Asia,Oceania,and South America appeared to be most vulnerable.The high vulnerability were mainly due to their greater nutritional dependence on fish and fewer available resources to invest in climate adaptation.The contribution of marine fisheries to domestic food security varied considerably among the highly vulnerable countries.Specifically,African countries(Cape Verde,Gambia,Guinea,Guinea Bissau,Liberia,Madagascar,Mauritania,Mozambique and Senegal),Asian countries(Indonesia,Maldives,Philippines and Thailand),Oceanian countries(Fiji,Samoa,Solomon Islands and Vanuatu)and South America(Guyana)were mainly dependent on marine fishery to meet human demands for fish and fishery products.In contrast,fishery imports made the largest contribution to the supply of fish for human consumption in Cote d'Ivoire,Nigeria,and Togo.Inland fisheries constituted the greatest proportion of total fish production in Cambodia,Democratic Republic of Congo and Tanzania.Aquaculture made the largest proportion of total fish supply in Bangladesh,Egypt,and Vietnam.For the 27 countries that were identified as most vulnerable to climate-induced changes in marine fisheries,more than two-thirds of them depended on domestic marine fisheries as a main source of fish supply.Developing appropriate adaptation policies and management plans to reduce the impacts of changing climate is of great importance to sustain food security in these highly vulnerable and heavy marine fisheries-dependent countries. |
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