Effects of acoustic alarms, designed to reduce small cetacean bycatch in gillnet fisheries, on the behaviour of North Sea fish species in a large tank     

Kastelein RA  van der Heul S  van der Veen J  Verboom WC  Jennings N  de Haan D  Reijnders PJ 《Marine environmental research》2007,64(2):160-180

World-wide many cetaceans drown incidentally in fishing nets. To reduce the unwanted bycatch in gillnets, pingers (acoustic alarms) have been developed that are attached to the nets. In the European Union, pingers will be made compulsory in some areas in 2005 and in others in 2007. However, pingers may effect non-target marine fauna such as fish. Therefore in this study, the effects of seven commercially-available pingers on the behaviour of five North Sea fish species in a large tank were quantified. The species tested were: sea bass (Dicentrarchus labrax), pout (Trisopterus luscus), thicklip mullet (Chelon labrosus), herring (Clupea harengus), and cod (Gadus morhua). The fish were housed as single-species schools of 9-13 individuals in a tank. The behaviour of fish in quiet periods was compared with their behaviour during periods with active pingers. The results varied both between pingers and between fish species. Sea bass decreased their speed in response to one pinger and swam closer to the surface in response to another. Thicklip mullet swam closer to the bottom in response to two pingers and increased their swimming speed in response to one pinger. Herring swam faster in response to one pinger, and pout and cod (close relatives) showed no behavioural responses to any of the pingers. Of the seven pingers tested, four elicited responses in at least one fish species, and three elicited no responses. Whether similar responses would be elicited in these fish species in the wild, and if so, whether such responses would influence the catch rate of fisheries, cannot be derived from the results of this study. However, the results indicate the need for field studies with pingers and fish. Based on the small number of fish species tested, the present study suggests that the higher the frequency of a pinger, the less likely it is to affect the behaviour of marine fish.  相似文献   

ESI计量分析数据库的功能与科学评价——以中国地学研究机构的科学评价为例   总被引：2，自引：0，他引：2  

韩欣  刘子忠 《地质科技情报》2010,29(1)

ESI是国际著名的学术信息机构ISI建设的衡量科学研究绩效、跟踪科学发展趋势的计量分析数据库。在介绍ESI功能的基础上,利用ESI中10年来中国地球科学论文被引情况对国家评价、研究机构评价、科学家评价、期刊评价、论文评价等方面进行了分析。从发表论文数量看,中国已经进入地学大国的行列,但与地学强国还相距甚远。地学科学家应该在提高论文质量、提升论文引用率方面更加努力,为我国乃至世界地球科学的发展做出更大的贡献。  相似文献   

高美古全夜视宁度的变化     

刘子忠 《天文研究与技术》1999,(1):12

介绍了云南丽江高美古天文候选点,１９９５年１２月～１９９６年１１月全夜视宁度观测结果：全年平均ｒ０＝１６．５０ｃｍ（ＦＷＨＭ＝０．６７″）,夜平均极大值ｒｍａｘ＝２２．４１ｃｍ（０．４９″）,夜平均极小值ｒｍｉｎ＝１２．９５ｃｍ（０．８５″）。  相似文献   

一个薄层崩积物滑坡体中孔源压力波动的观测与分析     

Hane  WC 雷谦荣 《水文地质工程地质译丛》1993,(3):28-35

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Influence of fracture anisotropy on ground water ages and chemistry,Valley and Ridge province,Pennsylvania   总被引：5，自引：0，他引：5  

Burton WC  Plummer LN  Busenberg E  Lindsey BD  Gburek WJ 《Ground water》2002,40(3):242-257

Model ground water ages based on chlorofluorocarbons (CFCs) and tritium/helium-3 (³H/³He) data were obtained from two arrays of nested piezometers located on the north limb of an anticline in fractured sedimentary rocks in the Valley and Ridge geologic province of Pennsylvania. The fracture geometry of the gently east plunging fold is very regular and consists predominately of south dipping to subhorizontal to north dipping bedding-plane parting and east striking, steeply dipping axial-plane spaced cleavage. In the area of the piezometer arrays, which trend north-south on the north limb of the fold, north dipping bedding-plane parting is a more dominant fracture set than is steeply south dipping axial-plane cleavage. The dating of ground water from the piezometer arrays reveals that ground water traveling along paths parallel to the dip direction of bedding-plane parting has younger ³H/³He and CFC model ages, or a greater component of young water, than does ground water traveling along paths opposite to the dip direction. In predominantly unmixed samples there is a strong positive correlation between age of the young fraction of water and dissolved sodium concentration. The travel times inferred from the model ages are significantly longer than those previously calculated by a ground water flow model, which assumed isotropically fractured layers parallel to topography. A revised model factors in the directional anisotropy to produce longer travel times. Ground water travel times in the watershed therefore appear to be more influenced by anisotropic fracture geometry than previously realized. This could have significant implications for ground water models in other areas underlain by similarly tilted or folded sedimentary rock, such as elsewhere in the Valley and Ridge or the early Mesozoic basins.  相似文献   

在厄瓜多尔的金矿勘查     

Bagby  WC 苏文利 《物探化探译丛》1997,(6):47-49

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太古代含铁建造中金矿床的新类型：强烈剪切变质的含钯金矿床     

Olivo  GR 刘子忠 《地质科学译丛》1996,13(3):44-48

Ｃａｕｅ铁矿位于Ｓａｏ Ｆｒａｎｃｉｓｃｏ地盾南部Ｉｔａｂｉｒａ地区。在该区已确定出其变质程度达到角闪岩相三个地质单元：（１）太古代火山沉积层序；（２）元代含铁建筑单元；（３）元古代石曲岩单元。含铁建造单元被角闪岩脉切割，在构造上被火山沉积层序内的滑石片岩和角闪岩叠。  相似文献   

旋涡黑子在1972年10月太阳活动中的作用     

丁有济  李维宝  吴铭蟾  蒋治中  洪琴芳  刘子忠 《天文学报》1977,(2)

本文收集了云南天文台和北京天文台观测的1972年10月太阳活动区(McMath 12094)的68个耀斑192个节点的照相资料和一些黑子日珥形态,对它们进行了相关分折,得到如下主要结果:1.本区最初的耀斑活动开始于全群诸黑子中具有扭结磁场最高能态的前导黑子A(N)的上空,它迅速发展到后随S极黑子上空,然后发展到黑子面积以外.这一演变过程与全群黑子的形态变化和旋转运动同步.2.A黑子附近的耀斑活动最初开始于扭结磁力管的内部,与扭结磁形态的松解过程同步,耀斑节点的分布由黑子本影附近移向半影的外面.当扭结完全松开,该处耀斑活动全面减少.3.发现了一个巨大的黑子冕珥下面的强烈的吸引中心是旋涡黑子,从而证实了冕珥是强大电流在日冕中收缩形成的.4.对于A黑子的扭转磁结构提供了本区耀斑活动的主要能量来源和导致不稳定性的问题进行了讨论.  相似文献   

Clionid sponge surveys on the Florida Reef Tract suggest land-based nutrient inputs   总被引：1，自引：0，他引：1  

Ward-Paige CA  Risk MJ  Sherwood OA  Jaap WC 《Marine pollution bulletin》2005,51(5-7):570-579

Bioerosion by Cliona delitrix and Cliona lampa was assessed at 43 sites along the Florida Reef Tract, USA, in the summer of 2001. Sponge abundances were estimated using rapid visual assessment. Tissue samples of sponges were taken for analysis of delta15N. Comparison samples were taken from Belize. Annual trends in sponge abundance were estimated from archived videos covering the period from 1996 to 2001. Sites with the greatest boring sponge size and cover were in the Backcountry and Lower Keys, where total nitrogen, ammonium, and delta15N levels were highest. The sites with the largest relative increase of C. delitrix and C. lampa over the 5 year period were in the Upper Keys, where the greatest relative decline in stony coral cover has occurred. Florida sponge delta15N values were 5.2(+/-0.1)%, suggesting the influence of human waste; in comparison, offshore Belize samples were 2.1(+/-0.1)%. These results suggest sewage contamination of the Florida Reef Tract, shifting the carbonate balance from construction to destruction.  相似文献   

Assessing the influence and distribution of shrimp pond effluent in a tidal mangrove creek in north-east Australia   总被引：1，自引：0，他引：1  

Costanzo SD  O'Donohue MJ  Dennison WC 《Marine pollution bulletin》2004,48(5-6):514-525

Effluent from a land based shrimp farm was detected in a receiving creek as changes in physical, chemical and biological parameters. The extent and severity of these changes depended on farm operations. This assessment was conducted at three different stages of shrimp-pond maturity, including (1) when the ponds were empty, (2) full and (3) being harvested. Methods for assessing farm effluent in receiving waters included physical/chemical analyses of the water column, phytoplankton bioassays and nitrogen isotope signatures of marine flora. Comparisons were made with an adjacent creek that served as the farms intake creek and did not directly receive effluent. Physical/chemical parameters identified distinct changes in the receiving creek with respect to farm operations. Elevated water column NH(4)(+) (18.5+/-8.0 microM) and chlorophyll a concentrations (5.5+/-1.9 microg/l) were measured when the farm was in operation, in contrast to when the farm was inactive (1.3+/-0.3 microM and 1.2+/-0.6 microg/l, respectively). At all times, physical/chemical parameters at the mouth of the effluent creek, were equivalent to control values, indicating effluent was contained within the effluent-receiving creek. However, elevated delta(15)N signatures of mangroves (up to approximately 8 per thousand) and macroalgae (up to approximately 5 per thousand ) indicated a broader influence of shrimp farm effluent, extending to the lower regions of the farms intake creek. Bioassays at upstream sites close to the location of farm effluent discharge indicated that phytoplankton at these sites did not respond to further nutrient additions, however downstream sites showed large growth responses. This suggested that further nutrient loading from the shrimp farm, resulting in greater nutrient dispersal, will increase the extent of phytoplankton blooms downstream from the site of effluent discharge. When shrimp ponds were empty water quality in the effluent and intake creeks was comparable. This indicated that observed elevated nutrient and phytoplankton concentrations were directly attributable to farm operations.  相似文献