Identification and evaluation of shark bycatch in Georgia’s commercial shrimp trawl fishery with implications for management     

C. N. BELCHER  C. A. JENNINGS 《Fisheries Management and Ecology》2011,18(2):104-112

Abstract Many US states have recreational and commercial fisheries that occur in nursery areas occupied by subadult sharks and can potentially affect their survival. Georgia is one of few US states without a directed commercial shark fishery, but the state has a large, nearshore penaeid shrimp trawl fishery in which small sharks occur as bycatch. During our 1995–1998 investigation of bycatch in fishery‐dependent sampling events, 34% of 127 trawls contained sharks. This bycatch totalled 217 individuals from six species, with Atlantic sharpnose shark, Rhizoprionodon terraenovae (Richardson), the most common and finetooth shark, Carcharhinus isodon (Müller & Henle) and spinner shark, Carcharhinus brevipinna (Müller & Henle), the least common. The highest catch rates for sharks occurred during June and July and coincided with the peak months of the pupping season for many species. Trawl tow speed and tow time did not significantly influence catch rates for shark species. Gear configurations [net type, turtle excluder device (TED), bycatch reduction device] affected catch rates for shark species. Results of this study indicate gear restrictions, a delayed season opening, or reduced bar spacing on TEDs may reduce shark bycatch in this fishery.  相似文献   

美国罗非鱼产品进口市场集中度分析     

张红燕  袁永明  贺艳辉  王红卫  代云云 《湖南农业科学》2016,(11):106-108

美国是全球罗非鱼产品进口贸易大国,2015年罗非鱼产品进口量为22.5万t,进口额为9.81亿美元,是国际罗非鱼产品市场上最重要的进口贸易国之一。我国是罗非鱼产品出口贸易国,了解和掌握美国罗非鱼产品进口市场情况,对促进中国罗非鱼产品出口具有重要的意义。从进口量额、进口产品分析、进口来源地和进口价格总结了美国罗非鱼产品进口现状,通过进口来源国市场集中度(CR指数)、赫芬达尔—赫希曼指数(HHI指数)和洛伦兹曲线分析了进口市场集中度指标,表明美国罗非鱼产品进口来源市场集中度非常高。  相似文献   

美国耐旱景观实践及启示     

李应宾  付宗驰  武文丽 《中国城市林业》2015,13(6):45-48

在水资源日益紧缺的背景下,耐旱景观在世界范围内受到重视,其原则广泛应用于干旱地区的景观营造并获得了巨大收益。文中介绍美国耐旱景观及其原则,解析耐旱景观的内涵,列举美国耐旱景观实践的具体做法,希望通过美国耐旱景观的实践能够让更多地区的景观建设获得启示并从中受益。  相似文献   

Ontogenetic niche shifts in the American Alligator establish functional connectivity between aquatic systems     

Amanda L. Subalusky  Lee A. Fitzgerald 《Biological conservation》2009,142(7):1507-1514

Individual animals undergoing ontogenetic shifts in habitat use may establish a mobile link between discrete ecosystems via movement of energy, nutrients and matter, as well as through impacts on ecosystem and habitat structure. The American Alligator (Alligator mississippiensis) is a model species for studying ecological implications of ontogenetic niche shifts, because they grow in size by several orders of magnitude, and they play a critical role as both top predators and ecosystem engineers. We used equal trapping effort, radio telemetry and nest surveys to document ontogenetic habitat shifts of alligators between hydrologically isolated, seasonal wetlands and riverine systems. To estimate the degree of functional connectivity between systems, we quantified alligator biomass and nutrient excretion in both systems. Seasonal wetlands provided nesting and nursery sites for adult females and juveniles, which constituted 0.78 g/m² biomass and excreted 0.05 g/m²/yr N, P, Ca, Mg, Na and K in that system. In contrast, the riverine system provided non-nesting habitat for adults and sub-adults of both sexes, totaling 0.18 g/m² biomass and excreting 0.01 g/m²/yr of nutrients. Furthermore, sub-adults and adult females were documented moving across the terrestrial matrix, while adult males spent the duration of the study in the creek. Our results demonstrated that ontogenetic niche shifts in alligators establish connectivity between seasonal wetlands and riverine systems and with the surrounding terrestrial matrix. These findings have implications for the definition of jurisdictional wetlands under the US Supreme Court’s 2001 SWANCC decision and highlight the importance of ecological, as well as hydrological, connectivity.  相似文献   

Canine leishmaniosis in the United Kingdom: A zoonotic disease waiting for a vector?     

Susan E. Shaw  Debra A. Langton  Timothy J. Hillman 《Veterinary parasitology》2009,163(4):281

Leishmaniosis is an important sand fly transmitted protozoan disease of dogs and humans. In northern Europe, infection is mainly restricted to dogs that have travelled to and/or from endemic areas of the Mediterranean region during periods when there is high sand fly exposure, mostly between March and November. Infected dogs in these areas in northern latitudes are a potential reservoir should incursion of a competent vector occur. However, information on the scale of the potential reservoir in the UK is lacking. Confirmed cases of canine leishmaniosis entering the United Kingdom between 2005 and 2007 were identified using diagnostic samples submitted to the Department of Clinical Veterinary Science, University of Bristol and from collaborating laboratories (n = 257). All study dogs had clinico-pathological signs compatible with leishmaniosis, as typically reported in endemic countries and were leishmania positive in real time or conventional PCR tests, IFA serology and/or tissue microscopic examination for amastigote identification. Information obtained from each case included travel history, habitat, clinico-pathological findings and geographical location once located in the UK. The majority of dogs with complete travel history (n = 183) had spent at least 6 months in Spain (105/183), 28/183 were rescued from re-homing centres in the country of origin and 26/183 entered the UK with confirmed leishmaniosis. Once located in the UK, the majority of positive cases were resident in south and central England. The spectrum of clinico-pathological signs for this group of dogs is similar to that reported in endemic countries. These data confirm that a potentially significant reservoir of infected dogs is resident in areas where future climatic conditions may support introduction of competent vectors.  相似文献   

中、美农民合作经济组织的比较及启示     

鄢奋 《福建农业大学学报(哲学社会科学版)》2009,(3):33-36

介绍美国农民合作经济组织的理论和特点,并着重比较中、美农民合作经济组织的差异性,提出我国发展农民经济合作组织应注意的问题：（1）肯定政府的支持引导作用;（2）提升农民的平等、服务与合作意识;（3）多样化的农民合作经济组织。  相似文献   

马里兰大学图书馆印象     

颜玉怀 《农业图书情报学刊》2013,25(12):92-96

马里兰大学图书馆由1 个主馆、7 个分馆组成,实行分工联合服务。馆舍条件优越,馆藏资源丰富。服务内容呈现出专业服务、空间服务、技术服务、馆藏服务并举的多元化格局。注重用户的信息素养教育,成效显著。多途径与其他机构合作,使资源共享梦想成真。面向校外社区开放,使图书馆真正成为没有围墙的学习场所。  相似文献   

Diaspore characteristics and ecological adaptation of Bromus tectorum L. from different distribution regions     

YaoBin LIU  YuanMing ZHANG  Robert S NOWAK  Liliya DIMEYEVA 《干旱区科学》2013,5(3):310-323

The invasion of nonnative plants is considered one of the main threats to the structure and function of North American ecosystems.Moreover,they can alter ecosystem processes and reduce biodiversity.In arid and semi-arid region of North America,the species of European annual grass Bromus tectorum L.is an outstanding example of these problems,which not only increase the fire density and change the fire regime,but replace native communities.Therefore,there are amount of researches on B.tectorum,including resource acquisition,water use efficiency and growth.Whereas the relevant research on the morphology of diaspore is scare.Diaspores have a fundamental role in seed germination and seedling establishment.Besides,as an important link between different generations,diaspores have a vital significance on individual reproduction and population extension.Hence,diaspores under selection for studying have an important implication.This study compares differences in seed morphology for Bromus tectorum collected from the United States,Kazakhstan,and Xinjiang of China.The following indices of B.tectorum diaspores were analyzed:size,thickness of covering layers,and micromorphological characteristics of the base,middle and transition area of diaspores as well as of the awn.Micromorphology of the lemma and the cross-section of the diaspore were observed by scanning electron microscopy.Results showed that thickness of the lemma and the palea of diaspores from B.tectorum-infested grasslands in the United States were reduced(P<0.05),likely because of environmental influences.This reduction facilitated the germination of diaspores and lowered the resistance of B.tectorum to adverse environmental conditions.The length of the awn also increased significantly(P<0.05),which helped in dispersal and anchoring of diaspores.Therefore,B.tectorum adapted ecologically to its new environment in the United States by strengthening its establishment ability.However,the defense capability of B.tectorum decreased.These results fit the evolution of increased competitive ability hypothesis(EICA)of invasive species.Analysis of various cells on the lemma revealed that prickle densities and collapsed,long epidermal cells were easily influenced by environmental factors such as temperature and moisture because of the physiologic function of these structures on silicon accumulation.However,the form and the position of silica cells,which were not greatly influenced by environmental factors,might be genetically controlled.Studying these structures at the microscopic level helps define the relationship between the diaspore and its environment.This study has a reference value for future studies on B.tectorum.  相似文献   

黔东南地区特色生态农业发展探析     

黎华君  詹瑜  欧国武 《贵州农业科学》2011,(11)

对黔东南地区特色生态农业发展的优势和主要制约因素进行了剖析,并从良种良法的推广、特色生态农业资源的开发、农产品市场体系的完善、特色生态农业资源的保护、新的农业科技研究和新产品的开发等方面提出了黔东南特色生态农业可持续发展的对策,以期为黔东南地区特色生态农业发展提供一定的理论支撑,实现特色生态农业的可持续性发展。  相似文献   

中国与欧盟、美国、日本人造板甲醛标准比较     

王正国  段新芳  郭龙  韩井伟 《世界林业研究》2015,28(2):61-68

对中国人造板甲醛标准与欧盟、美国、日本的人造板标准进行比较, 分析国内标准与国外标准在质量要求、平衡处理和检测方法要求等方面的差异, 以及不同检测方法间的相关性, 以期为中国人造板的生产、贸易和标准制修订以及标准输出提供参考.  相似文献