Genetic structure of Octopus vulgaris around the Iberian Peninsula and Canary Islands as indicated by microsatellite DNA variation   总被引：2，自引：0，他引：2  

Cabranes  C.; Fernandez-Rueda  P.; Martinez  J. L. 《ICES Journal of Marine Science》2008,65(1):12-16

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Positive feedback fishery: Population consequences of ‘crab-tiling’ on the green crab Carcinus maenas     

E.V. Sheehan  R.C. Thompson  R.A. Coleman  M.J. Attrill 《Journal of Sea Research》2008,60(4):303-309

Collection of marine invertebrates for use as fishing bait is a substantial activity in many parts of the world, often with unknown ecological consequences. As new fisheries develop, it is critical for environmental managers to have high quality ecological information regarding the potential impacts, in order to develop sound management strategies. Crab-tiling is a largely unregulated and un-researched fishery, which operates commercially in the south-west UK. The target species is the green crab Carcinus maenas. Those crabs which are pre-ecdysis and have a carapace width greater than 40 mm are collected to be sold to recreational anglers as bait. Collection involves laying artificial structures on intertidal sandflats and mudflats in estuaries. Crabs use these structures as refugia and are collected during low tide. However, the effect that this fishery has on populations of C. maenas is not known. The impact of crab-tiling on C. maenas population structure was determined by sampling crabs from tiled estuaries and non-tiled estuaries using baited drop-nets. A spatially and temporarily replicated, balanced design was used to compare crab abundance, sizes and sex ratios between estuaries. Typically, fisheries are associated with a reduction in the abundance of the target species. Crab-tiling, however, significantly increased C. maenas abundance. This was thought to be a result of the extra habitat in tiled estuaries, which probably provides protection from natural predators, such as birds and fish. Although crabs were more abundant in tiled estuaries than non-tiled estuaries, the overall percentage of reproductively active crabs in non-tiled estuaries was greater than in tiled estuaries. As with most exploited fisheries stocks, crabs in exploited (tiled) estuaries tended to be smaller, with a modal carapace width of 20–29 mm rather than 30–39 mm in non-tiled estuaries. The sex ratio of crabs however; was not significantly different between tiled and non-tiled estuaries. These results illustrate the potential to manage fished populations using habitat provision to mitigate the effects of fishing pressure.  相似文献   

皱纹盘鲍野生与养殖群体微卫星标记遗传变异研究   总被引：9，自引：3，他引：6  

束靖  李琪  于瑞海  田传远 《中国海洋大学学报(自然科学版)》2008,38(1):52-58

采用7个微卫星标记对辽宁大连、山东烟台、荣城、崂山和胶南5个皱纹盘鲍养殖群体,以及山东长岛、荣城、日本岩手、韩国仁川4个皱纹盘鲍野生群体进行了群体遗传多样性与遗传分化的研究.结果表明,从等位基因数与杂合度上分析,养殖群体(N=8.0～9.4,He=0.754～0.787)遗传多样性显著低于野生群体(N=11.3～15.0,He=0.821～0.866);等位基因频率分布揭示出野生群体中一些稀有等位基因在养殖群体中有所丢失;亲鲍选用数量少与性别比例不均衡可能是产生养殖群体中遗传多样性显著减少的原因.通过对等位基因频率比较分析,5个养殖群体之间以及养殖群体与野生群体之间观察到显著差异的Fst与Rst值,野生群体之间日本群体Fst与Rst值与其他3个野生群体差异显著,群体间存在遗传分化;养殖群体间遗传距离与地理距离不相关,可能是皱纹盘鲍育苗过程中亲鲍和苗种频繁交流所造成的结果;日本群体与其他3个野生群体间存在显著遗传分化与皱纹盘鲍短暂的浮游期与有限的扩散能力有关.  相似文献   

Influencing factors for formation of urban and rural spatial structure in metropolis fringe area—Taking Shuangliu County of Chengdu in China as a case   总被引：1，自引：0，他引：1  

Kaiyong Wang  Xiaolu Gao  Tian Chen 《中国地理科学(英文版)》2008,18(3):224-234

With rapid urbanization process, the pace of urban sprawl has been quickened and most metropolises have experienced expansions in leaps and bounds in suburbanization, which has greatly changed the urban and rural spatial structure of the metropolis fringe area. In this paper, Shuangliu County is taken as a case, since it is a typical fringe area of Chengdu Metropolis. Based on Landsat TM images of Chengdu City and Shuangliu County obtained in 1985, 2000 and 2004, characteristics of urban and rural spatial structure in Shuangliu County were analyzed, such as core-periphery spatial structure and some obvious integration trends. Then the influencing factors for the formation of urban and rural spatial structure were identified, including some natural, social, economic and political factors. According to the discussion of this paper, Shuangliu County is undergoing a key transition and reform period. Its formation of urban and rural spatial structure was affected not only by such common factors as the location, natural background, industrial transition, migration, etc., but also by some unique factors such as city planning and policy guidance, which played an important role in accelerating its uneven spatial structure. The understanding of the role of the influencing factors would be useful for carrying out spatial management and development planning of metropolis fringe area.  相似文献   

江苏省环太湖地区土地利用结构演变与驱动力分析   总被引：6，自引：0，他引：6  

李闽  孙在宏  杨素静  乔伟峰 《地球信息科学学报》2008,10(2):136-141

本文以江苏省环太湖地区为研究区域,以1996～2007年快速发展时期为研究时段,对这一特定时空的土地利用结构变化及其驱动机制进行研究。文章以大量数据为基础,分析了区域内土地利用结构动态度、信息熵和均衡度。1996年以来,江苏省环太湖地区用地结构调整即以趋向均衡的速度逐渐变缓。从2004年开始,江苏省环太湖地区用地结构趋向合理、均衡化发展。文章揭示了土地利用结构与经济发展驱动因素、农业集约化因素、城市化因素、人口因素、政策因素这五个因素有关。  相似文献   

北京防震历史经验与汶川地震灾后城镇选址重建   总被引：5，自引：2，他引：3  

毛锋  马金锋  周文生 《地球信息科学学报》2008,10(4):503-510

5.12汶川8.0级地震使灾区蒙受了巨大的生命和财产损失,地震造成的灾害与灾区地质构造有极强的空间相关性。灾区地震历史的分析结果表明,该区域地震格局有明显的时空特征,重灾区灾后重建城镇选址宜多学科联合谨慎规划。康熙18年(1679年)的北京平谷-三河8.0级地震与5.12汶川地震惨烈程度相近,北京地质构造研究与地震时空格局分析具有重大的现实意义,北京城市发展中的防震规划历史经验值得5.12地震灾区在重建与今后发展中借鉴。  相似文献   

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郭良迁  马青  杜雪松  孙东颖 《大地测量与地球动力学》2008,28(3):14-20

?????????????????????????1985??2006?????????????????????α??????????????????????????????????????????????????????????6???????????????????????????????????????????????????????л??????????????5??????????????????  相似文献   

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郭良迁  黄立人 《大地测量与地球动力学》2008,28(4):17-24

????????1956??1999??????????????????????????顢?????顢?????????????????????????????б??????е??????Щ???????????????4??????У?1956??1978????????????????????????????????ε????Ms7.4?????????????й??1978??1985???1990??1995?????????????????????????鶫??????Ms6.2 ??Ms6.1?????й??  相似文献   

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范国胜  焦青 《大地测量与地球动力学》2008,28(6):27-30

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张四新  张希  王双绪  薛富平  刘立炜 《大地测量与地球动力学》2008,28(6):43-46

??????8.0?????????????????????????????????????Ms8.0?????????????α????????:???????????α???????????????????????????????????仯???????????????????????????????????????????????????????????????????????????????α???????  相似文献