Reforming management of commercial fisheries in a small island territory     

Michael Harte  John Barton 《Marine Policy》2007

The Falkland Islands has successfully met many challenges in the management and development of its fisheries resources over the last 20 years. To meet a new set of challenges the current licensing system based on the allocation of non-transferable, variable duration licences to individual vessels is being replaced by a system of long-term individual transferable rights owned by Falkland Islanders. The anticipated gains are enhanced economic performance of the sector because fishing businesses have increased security and flexibility, rapid diversification from harvesting into value-added activities and increased international competitiveness as poorly performing companies sell rights to well performing companies. Implementing a rights-based regime in a small coastal state is challenging. Thin markets for rights, a desire to maintain local control of fishing rights, and a dependence on foreign direct investment in the fisheries sector are key considerations in the design of an effective and efficient management regime. Starting operation in 2006/07, the new rights-based management system provides a model for small coastal states or small industrial fisheries that previously had considered rights-based systems too complex to implement and administer, despite the inherent advantages of rights-based management.  相似文献   

Contaminants in the arctic marine environment: priorities for protection   总被引：1，自引：0，他引：1  

Macdonald  R. W.; Bewers  J. M. 《ICES Journal of Marine Science》1996,53(3):537-563

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中国海相盆地油气资源动态评价与有利勘探方向     

徐旭辉  陆建林  王保华  郑伦举  方成名  蔡芃睿  赵琳洁 《地学前缘》2022,29(6):73-83

中国海相盆地是油气大突破的重要领域。立足中国含油气盆地分析,通过全球超大陆旋回,认为元古代以来3个克拉通海相盆地总体经历了4个地史阶段,明确了海相层系原型盆地演化序列与并列迭加特点,总结梳理了3类原型4种控源模式,表明原型盆地决定了烃源岩发育的环境及分布模式,编制了三大盆地主要层系分类型烃源岩分布图,并明确了烃源岩特征;基于海相烃源岩生烃-排烃-滞留油气动态演化模式,建立了海相层系烃源岩有效性动态评价和“常规-非常规”一体化资源评价等方法技术体系。基于新方法计算了海相层系生排烃量和资源量,明晰了重点盆地油气资源潜力分布。提出了大于10亿t资源量区带15个、5~10亿t级区带13个,指出了下步海相层系勘探的重点领域和方向。  相似文献   

Characterisation of likelihood of gas hydrates occurrence in the South China Sea based on Bonferroni mean-based TOPSIS and fuzzy set theory     

《地学前缘(英文版)》2023,14(2):101513

The efficiency of gas hydrate production depends on the success of gas exploration and occurrence evaluation. The existing evaluation models are generally univariate and only applicable to certain geological settings. This study presents a holistic approach to evaluate the likelihood of gas hydrate occurrence by supplying an index for mapping gas hydrate levels with depth. The approach integrates a generalised TOPSIS method with the fuzzy set theory. An expedition of gas hydrate conducted in the Shenhu area of the South China Sea was adopted as a case study to assess the reliability of the proposed index. As a multivariate model, the proposed approach enables the capture of non-linearity associated with gas hydrates in its entirety. The magnitude of the strength of the influential factor varies substantially from one site to another across the Shenhu area. The results also show that no site achieves the highest likelihood ‘Level V’. These results are consistent with the gas saturation values obtained using Archie’s relationship. For example, at SH4 and SH7, the values of the likelihood index are the highest between 170–185 m and 150–165 m, respectively, and the observed saturation at these locations varies from 20% (SH4) to 43% (SH7). The proposed likelihood index yields a prominent ability to quantify the level of occurrence of gas hydrates with depth at different sites. It appears to be an efficient multicriteria system bound to improve the management of the gas production trial stage.  相似文献   

渤海湾盆地南堡凹陷滩海潜山裂缝特征及其形成机制     

兰朝利  廖保方  王志坤  刘丹江  杨明慧  崔志员 《地质学报》2015,89(2):252-261

裂缝是渤海湾盆地南堡凹陷滩海碳酸盐岩潜山储层的主要储集空间之一,其发育与否制约着南堡凹陷潜山油气藏成藏与产量。应用成像测井、镜下观察、岩心描述以及露头考察资料研究了南堡凹陷滩海碳酸盐岩潜山裂缝特征,并探讨了裂缝控制因素与形成机制。南堡凹陷滩海潜山裂缝以构造缝为主,裂缝比较发育,以微—窄缝(主要为5~50μm)为主。控制南堡凹陷滩海潜山裂缝发育的因素主要为拉张断陷作用与古风化作用,前者形成与正断层伴生的构造缝,后者形成非构造缝,包括风化缝、层面缝、溶塌碎裂缝,主要分布在古岩溶垂直渗流带内。构造缝形成经历了前始新世挤压、沙河街阶-东营阶拉伸断陷以及馆陶阶以来的走滑拉张三个过程,但有效的开启裂缝主要形成于沙河街阶-东营阶的拉伸断陷时期。  相似文献   

Thermal regimes in a large upland salmon river: a simple model to identify the influence of landscape controls and climate change on maximum temperatures   总被引：1，自引：1，他引：0  

Markus Hrachowitz  C. Soulsby  C. Imholt  I. A. Malcolm  D. Tetzlaff 《水文研究》2010,24(23):3374-3391

Temperature observations at 25 sites in the 2000 km² Dee catchment in NE Scotland were used, in conjunction with geographic information system (GIS) analysis, to identify dominant landscape controls on mean monthly maximum stream temperatures. Maximum winter stream temperatures are mainly controlled by elevation, catchment area and hill shading, whereas the maximum temperatures in summer are driven by more complex interactions, which include the influence of riparian forest cover and distance to coast. Multiple linear regression was used to estimate the catchment‐wide distribution of mean weekly maximum stream temperatures for the hottest week of the 2‐year observation period. The results suggested the streams most sensitive to high temperatures are small upland streams at exposed locations without any forest cover and relatively far inland, while lowland streams with riparian forest cover at locations closer to the coast exhibit a moderated thermal regime. Under current conditions, all streams provide a suitable thermal habitat for both, Atlantic salmon and brown trout. Using two climate change scenarios assuming 2·5 and 4 °C air temperature increases, respectively, temperature‐sensitive zones of the stream network were identified, which could potentially have an adverse effect on the thermal habitat of Atlantic salmon and brown trout. Analysis showed that the extension of riparian forests into headwater streams has the potential to moderate changes in temperature under climate change. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Contribution of intercepted subsurface flow to road runoff and sediment transport in a logging‐disturbed tropical catchment     

J. N. Negishi  R. C. Sidle  A. D. Ziegler  S. Noguchi  N. Abdul Rahim 《地球表面变化过程与地形》2008,33(8):1174-1191

Hydrological and sediment fluxes were monitored for a 1 yr period in a tropical headwater catchment where a 3 yr old logging road caused substantial Hortonian overland flow (HOF) and intercepted subsurface flow (ISSF). On a 51·5 m road section, ISSF became an increasingly important component of total road runoff, up to more than 90% for large storms. The proportion of ISSF contributed by road cuts along more or less planar slopes compared with ISSF from a zero‐order basin (convergent slopes) truncated by the road declined with increasing rainfall. During the monitored storms that generated ISSF along the road, on average, 28% of sediment export and 79% of runoff from the road section were directly attributable to ISSF. Estimates of total sediment export from the road surface (170 t ha^?1 yr^?1) and suspended sediment export from the logging‐disturbed catchment (4 t ha^?1 yr^?1) were exceptionally high despite 3 yr of recovery. ISSF caused not only additional road‐generated sediment export, but also exacerbated HOF‐driven erosion by creating a poor foundation for vegetation recovery on the road surface. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

地层因素对陆相沉积储层特征的控制(英文)   总被引：50，自引：2，他引：48  

Timothy A.Cross 《地学前缘》2000,(4)

在相同沉积相和沉积环境中 ,沉积记录中作为地层位置函数的不同尺度的地层学与沉积学性质的变化是有序的并可以预测。诸多沉积学和地层学性质 ,从孔隙度、渗透率到地质体的规模和非均质性对于储集性能和产能都是重要的。地层导致的上述性质的变化与由于原始沉积环境的差异产生的变化同等重要。运用地层观点对沉积物某种或多种性质变化进行分析 ,表明这些变化具有规律性并有向一些界限呈单向变化的趋势。与此对照 ,运用对时间和地层位置并不敏感的“相”对这些性质进行分析会发现数值具明显的非相关离散特征。因此 ,仅根据沉积环境或相组成对储集性能进行评价会造成预测的准确性和精确性变差。由此 ,文中提出了能够提高储层表征准确性和精确性的一种新的分析思路 ,即运用地层观点评价相的诸多性质。上述原理可用陆相地层中的一些实例加以说明。以河道砂岩储层为例 ,在地层剖面上 ,随着可容纳空间与沉积物补给的比值 (A/S)的增大 ,槽状交错层组的厚度和层的厚度向上增大 ,孔隙度、渗透率、保存下来的河道的宽度、连续性和连通程度降低 ,而底形多样性、相的分异性、相的保存程度和非均质性增加。这些性质所表现出来的单向变化趋势多数是由于作为A/S值函数的原始地貌单元的保存程度的变化而产生的。同时 ,地  相似文献   

铜官山矿田金矿床类型和构造控矿作用分析   总被引：1，自引：0，他引：1  

万仁虎 《地质力学学报》2004,10(2):122-128

铜官山矿田是我国著名的铜矿田和铜产地之一,近年来又相继发现了一批金矿床,属于与铜矿床具有成因联系的共生金矿床,主要有铁帽型和硫化物型。本文主要阐述金矿床的类型、地质特征及构造控矿作用。认为该区硫铁矿亚型和铁帽亚型金矿床均属于与燕山期中性-中酸性侵入岩具有成因联系的岩浆热液型矿床,只是氧化、剥蚀与保存条件不同而以不同类型出露。金矿体的产状严格受铜官山倒转背斜不同部位地层岩石的产状及其层间断裂的控制。   相似文献   

Process inference from topographic fractal characteristics in the tectonically active Northwest Himalaya,India     

Ramendra Sahoo  R.N. Singh  Vikrant Jain 《地球表面变化过程与地形》2020,45(14):3572-3591

Topography evolves under the coupled effect of exogenic and endogenic governing factors, and their scale-(in)variant dynamics. This results in a self-affine topography across a finite range, with a characteristic fractal dimension. Fractal analysis has been used to classify geological terrains having distinct litho-tectonic settings. However, process-based understanding of the fractal behaviour of a natural landscape is still limited. The current study aims to substantiate and expand upon the present knowledge of topographic response to the complex actions of the governing factors using fractal characteristics. We examined the association between the litho-tectonic, climatic settings and the fractal characteristics of the topography in the tectonically active Northwest Himalaya. Our analysis was carried out in three separate sectors having diverse litho-tectonic settings. We used the roughness–length method to calculate the fractal parameters (fractal dimension, D; ordinate intercept, q). The Higher and the Lesser Himalaya were found to be characterized by low D and high q, while the tectonically active Sub Himalaya was found to have moderate D and low q. The southernmost foreland alluvial plains were characterized by high D and low q. Clusters of the fractal parameters were found to be consistent in spatial pattern across the three sectors. Our results showed that the geological–geomorphological settings and the associated processes (e.g. uplift, erosion and diffusion) can be well inferred using the fractal characteristics of the topography. Further, our results implied first-order control of lithology in sustaining and shaping the topographic geometry (both its amplitude and texture) in the tectonically active Northwest Himalaya. The spatial distribution of the fractal parameters also suggested the secondary control of tectonic uplift and, to a much lesser extent, mean annual rainfall on the topographic geometry. These results collectively point to the role of complex actions of the governing factors in the landscape evolution process. © 2020 John Wiley & Sons, Ltd.  相似文献