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Characterizing regime shifts in the marine environment   总被引:6,自引:0,他引:6  
Recent years have seen a plethora of studies reporting that ‘regime shifts’ have occurred in the North Atlantic and Pacific Oceans during the last century. In many cases, the criteria used to distinguish a regime shift have not been explicitly stated. In other cases, a formal definition has been proposed and the data set assessed against it. Developing a universal quantitative definition for identifying and distinguishing between purported climatic and ecological regime shifts has proved problematic as many authors have developed criteria that seem unique to the system under study. Consequently, they throw little light on the drivers of ecological regime shifts. Criteria used to define regime shifts are reviewed and on the basis of evidence from purported regime shifts, common characteristics in the speed and amplitude of the changes and the duration of quasi‐stable states are used to propose a more clearly defined set of criteria for defining climatic and ecological regime shifts. Causal drivers of regime shifts are explored using correlation analysis. Limitations of these methods are discussed.  相似文献
Climate change and the future for coral reef fishes   总被引:5,自引:0,他引:5  
Climate change will impact coral-reef fishes through effects on individual performance, trophic linkages, recruitment dynamics, population connectivity and other ecosystem processes. The most immediate impacts will be a loss of diversity and changes to fish community composition as a result of coral bleaching. Coral-dependent fishes suffer the most rapid population declines as coral is lost; however, many other species will exhibit long-term declines due to loss of settlement habitat and erosion of habitat structural complexity. Increased ocean temperature will affect the physiological performance and behaviour of coral reef fishes, especially during their early life history. Small temperature increases might favour larval development, but this could be counteracted by negative effects on adult reproduction. Already variable recruitment will become even more unpredictable. This will make optimal harvest strategies for coral reef fisheries more difficult to determine and populations more susceptible to overfishing. A substantial number of species could exhibit range shifts, with implications for extinction risk of small-range species near the margins of reef development. There are critical gaps in our knowledge of how climate change will affect tropical marine fishes. Predictions are often based on temperate examples, which may be inappropriate for tropical species. Improved projections of how ocean currents and primary productivity will change are needed to better predict how reef fish population dynamics and connectivity patterns will change. Finally, the potential for adaptation to climate change needs more attention. Many coral reef fishes have geographical ranges spanning a wide temperature gradient and some have short generation times. These characteristics are conducive to acclimation or local adaptation to climate change and provide hope that the more resilient species will persist if immediate action is taken to stabilize Earth's climate.  相似文献
Anthropogenic global warming has significantly influenced physical and biological processes at global and regional scales. The observed and anticipated changes in global climate present significant opportunities and challenges for societies and economies. We compare the vulnerability of 132 national economies to potential climate change impacts on their capture fisheries using an indicator-based approach. Countries in Central and Western Africa (e.g. Malawi, Guinea, Senegal, and Uganda), Peru and Colombia in north-western South America, and four tropical Asian countries (Bangladesh, Cambodia, Pakistan, and Yemen) were identified as most vulnerable. This vulnerability was due to the combined effect of predicted warming, the relative importance of fisheries to national economies and diets, and limited societal capacity to adapt to potential impacts and opportunities. Many vulnerable countries were also among the world's least developed countries whose inhabitants are among the world's poorest and twice as reliant on fish, which provides 27% of dietary protein compared to 13% in less vulnerable countries. These countries also produce 20% of the world's fish exports and are in greatest need of adaptation planning to maintain or enhance the contribution that fisheries can make to poverty reduction. Although the precise impacts and direction of climate-driven change for particular fish stocks and fisheries are uncertain, our analysis suggests they are likely to lead to either increased economic hardship or missed opportunities for development in countries that depend upon fisheries but lack the capacity to adapt.  相似文献
A major mid-1980s shift in ecological structure of significant portions of the Southern Ocean was partially due to the serial depletion of fish by intensive industrial fishing, rather than solely to climate factors as previously hypothesized. Over a brief period (1969–1973), several finfish stocks were on average reduced to <50%, and finally (mid-1980s) to <20%, of original size. Despite management actions, few stocks have recovered and some are still declining. Most affected species exhibit K-selected life-history patterns, and before exploitation presumably fluctuated in accordance with infrequent strong year classes, as is true of such fish elsewhere. A climate regime, the Southern Annular Mode, once oscillated between two states, but has remained in its 'positive mode' since the time of the fish extraction. This may have increased finfish vulnerability to exploitation. As breeding stocks decreased, we hypothesize that availability of annually produced juvenile fish fed upon by upper-level predators remained low. Correlations between predator populations and fish biomass in predator foraging areas indicate that southern elephant seal Mirounga leonina , Antarctic fur seal Arctocephalus gazella , gentoo penguin Pygoscelis papua , macaroni penguin Eudyptes chrysolphus and 'imperial' shag Phalacrocorax spp. – all feeding extensively on these fish, and monitored at Marion, Crozet, Kerguelen, Heard, South Georgia, South Orkney and South Shetland Islands, where fishing was concentrated – declined simultaneously during the two periods of heavy fishing. These patterns indicate the past importance of demersal fish as prey in Antarctic marine systems, but determining these interactions' ecological mechanisms may now be impossible.  相似文献
秘鲁鳀资源变动及与海洋环境要素的关系研究进展   总被引:2,自引:0,他引:2  
秘鲁鳀(Engraulis ringens)是一种小型中上层鱼类.作为重要的商业性鱼类之一,秘鲁鳀的捕捞产业曾形成了世界上最大的单鱼种渔业,但其产量的年间差异非常大,上升流流场结构变化是其产量变化的重要影响因素.上升流对秘鲁鳀捕捞量的作用机制可归纳为低纬度的地理位置、适宜的水温结构、低溶解氧、高能量传递效率的食物网以及复杂的海洋环境要素变化五个方面.秘鲁鳀渔业生物学的多个方面都显著地受到了海洋环境变化的影响.此外,与气候相关的大尺度海洋生态系统周期性变化(regime shift)也影响到了秘鲁鳀的资源变动.本研究认为,今后在加强对长时间尺度生态系统周期性变化的研究同时,也应注重结合海洋环境变化、捕捞因素及种群的内部动力过程这三者之间的关系,结合基于个体的海洋动力学,建立秘鲁鳀资源评估及预测的模型,为合理开发和管理提供基础.  相似文献
捕捞压力和气候变化对东海马面纯渔获量的影响   总被引:2,自引:0,他引:2  
为了研究捕捞压力和气候变化对东海马面纯(Navodon spp.)渔获量的影响,对1976年~2006年的东海马面纯渔获量进行了分析。东海马面纯渔获量可划分成因捕捞效应所产生的趋势变化和因气候变动所导致的渔获量变动,前者可用Fox模型来拟合。Fox模型拟合结果显示,东海马面纯渔获量与捕捞努力量显著相关(P〈0.01)。移除捕捞压力增长引起的变化趋势后,其渔获量变动与热带气旋影响指数、东海海表温度、东海冬季季风和黄海夏季季风呈显著正偏相关(P〈0.03),与热带气旋影响指数、黄海冬季季风及长江流域和东海沿岸降雨呈显著负偏相关(P〈0.03)。根据捕捞努力量和气候变量对东海马面纯渔获量进行拟合,结果显示,拟合的渔获量与实际渔获量显著相关(R=0.91,P〈0.01),说明捕捞压力和气候变化显著影响东海马面纯渔获量的变动。此外,由于未来气候的变化,东海马面鲍渔获量可能出现更大波动。  相似文献
气候变化对世界主要渔业资源波动影响的研究进展   总被引:2,自引:0,他引:2  
最近几十年来,极端反常天气纷现世界各地,凸显出严峻的全球气候变化问题:高强度的降雨,严重的洪水,干旱和热浪,南极上空臭氧空洞年扩大.  相似文献
Interdecadal variations in Japanese sardine and ocean/climate   总被引:1,自引:1,他引:2  
Relations between the long-term variations in numbers of Japanese sardine and in ocean/climate were studied. We examined long-term records of the spring air temperature on the north-western coast of North America (ATNA; 40–50°N, 130–110°W) reconstructed from tree rings, and the sardine catch records inferred from documents dating from 1600 to 1990. High sardine catches occurred eight times in this period, and each high catch continued for 7–45 years. We found a significant difference in mean ATNAs between the abundant and poor catch periods: high (low) catch occurred in periods of high (low) ATNA. ATNA was negatively correlated with spring sea-surface temperature east of Japan (SSTJ; 36–40°N, 150–160°E), where the sardine possibly migrate north-eastward, a relation which was confirmed from 1940 to 1990. In years when the Aleutian Low Pressure System (AL) shifted south-east and intensified, the westerly wind was strong east of Japan along the south-western edge of the AL, resulting in low SSTJ; a warm south-westerly wind blows in the west coast of North America along the south-eastern edge of the AL. If we assume that this relation between ATNA and SSTJ can be extended back to the 1600s, high (low) catches occur in the period when SSTJ is low (high). This relation between sardine catch and SSTJ is consistent with previous studies based on data from after 1900. The present results suggest that long-term variations in Japanese sardine are related to interdecadal North Pacific ocean/climate variability.  相似文献
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