Rockfish in Puget Sound: An ecological history of exploitation     

Gregory D. Williams  Phillip S. Levin  Wayne A. Palsson 《Marine Policy》2010

In Puget Sound, WA (USA), rockfish (Sebastes spp.) have significantly declined in abundance, with multiple petitions to list individual species under the Endangered Species Act. In order to better understand the ecological legacy of rockfish fishing to the Puget Sound ecosystem, the local history of rockfish exploitation was reviewed, focusing on the socioeconomic forces and management decisions which influenced the trajectory of landings. Rockfish have always been harvested for human consumption in the region, but over time exploitation patterns have changed from an opportunistic subsistence activity by indigenous peoples, to a year-round target of commercial and recreational interests. Annual commercial and recreational harvests together peaked (almost 400 mt) in the early 1980s as anglers’ attitudes changed, gear technology improved, rockfish became more familiar to the market, human population increased, and agency programs promoted fisheries to sustain employment. Rockfishes were generally not managed intensely or with conservation goals in mind until the late 1980s, in part due to scientific shortcomings and a lack of resources. By the time management actions were deemed necessary, the greatest harvest had already occurred. However, the low intrinsic productivity of most rockfish species suggests that the legacy of fishing will remain for years to come. As managers strive to restore the integrity and resilience of Puget Sound, they must realize the significance of historical fishery removals to the ecosystem and use the proper social and economic incentives to drive individual behavior toward these ecosystem goals.  相似文献   

Seismic attenuation in the crust at the mid-Atlantic plate boundary in south-west Iceland   总被引：1，自引：0，他引：1  

William Menke  Vadim Levin  Ravi Sethi 《Geophysical Journal International》1995,122(1):175-182

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The theoretical model of the drop spectrum formation process in clouds     

L. M. Levin  Y. S. Sedunov 《Pure and Applied Geophysics》1968,69(1):320-335

Summary In this paper the theoretical model of cloud spectrum formation process is built in which spectrum formation and its development are followed by and these observations find no contradictions, beginning with air ascent containing condensation of nuclei and up to large drop formation falling out off the cloud. Both the obtained results of velocity spectrum formation and the form of distribution function corresponds to the direct observations. The model does not use any empirical relations and empirical regularities; it is free from arbitrary suppositions and assumptions which are not examined by experiments, and the number of parameters in it is limited by ones (vertical velocityU _z, turbulent diffusion coefficientK _z and two parameter distribution function of nucleus condensation with super-saturation). First in the developed theory the principal contradictions not allowing till now to connect together condensational and coagulation stages of cloud spectrum development are overcome.  相似文献   

Influence of illumination conditions on the sea-bottom visibility     

G. D. Gilbert  L. S. Dolin  I. M. Levin  A. G. Luchinin  S. Stewart 《Izvestiya Atmospheric and Oceanic Physics》2006,42(1):115-123

Statistical models of the useful and background signals forming an image of the sea bottom observed through a rough sea surface are constructed. The methods for estimating the signal-to-noise ratio in the image of the bottom with the test distribution of the reflectance are described. The dependence of the signal-to-noise ratio on observational conditions, in particular, on the mutual orientation of the directions of sighting, wind, and solar vertical, is analyzed. Recommendations on the choice of optimal conditions for bottom observations from airborne carriers are given.  相似文献   

Surficial Hydrocarbon Seep Infauna from the Blake Ridge (Atlantic Ocean, 2150 m) and the Gulf of Mexico (690–2240 m)     

Christie A. Robinson  Joan M. Bernhard  Lisa A. Levin  Guillermo F. Mendoza  & Jessica K. Blanks 《Marine Ecology》2004,25(4):313-336

Abstract.  Infauna, including foraminifera and metazoans, were enumerated and identified from five types of seep habitats and two adjacent non-seep habitats. Collections were made with the deep submergence research vessel 'Alvin' from three areas of active seepage in the Gulf of Mexico (Alaminos Canyon [2220 m], Atwater Canyon [1930 m], and Green Canyon lease block 272 [700 m]) and on the Blake Ridge Diapir [2250 m], which is located off the southeastern coast of the United States. The seep habitats sampled included four types of microbial mats ( Beggiatoa , Thioploca , thin and thick Arcobacter ) and the periphery of a large mussel bed. Sediments under large rhizopod protists, xenophyophores, were sampled adjacent to the mussel bed periphery. A non-seep site, which was >1 km away from active seeps, was also sampled for comparison. Densities of most taxa were higher in the Gulf of Mexico seeps than in Blake Ridge samples, largely because densities in the thick microbial mats of Blake Ridge were significantly lower. Diversity was higher in the Thioploca mats compared to other microbial-mat types. Within an ocean basin ( i.e. , Atlantic, Gulf of Mexico) we did not observe significant differences in meiofaunal or macrofaunal composition in Beggiatoa versus Thioploca mats or thin versus thick Arcobacter mats. Foraminifera represented up to 16% of the seep community, a proportion that is comparable to their contribution at adjacent non-seep communities. In general, the observed densities and taxonomic composition of seep sites at the genus level was consistent with previous observations from seeps ( e.g. , the foraminifers Bolivina and Fursenkoina , the dorvilleid polychaete Ophryotrocha ).  相似文献   

Numerical simulation of artificial ground freezing in a fluid-saturated rock mass with account for filtration and mechanical processes     

Ivan A. Panteleev  Anastasiia A. Kostin  Oleg A. Plekhov  Lev Yu. Levin 《寒旱区科学》2017,9(4):363-377

This study is devoted to the numerical simulation of the artificial ground freezing process in a fluid-saturated rock mass of the potassium salt deposit. A coupled model of nonstationary thermal conductivity, filtration and thermo-poroelasticity, which takes into account dependence of the physical properties on temperature and pressure, is proposed on the basis of the accepted hypotheses. The considered area is a cylinder with a depth of 256 meters and diameter of 26.5 meters and includes 13 layers with different thermophysical and filtration properties. Numerical simulation was carried out by the finite-element method. It has been shown that substantial ice wall formation occurs non-uniformly along the layers. This can be connected with geometry of the freezing wells and with difference in physical properties. The average width of the ice wall in each layer was calculated. It was demonstrated that two toroidal convective cells induced by thermogravitational convection were created from the very beginning of the freezing process. The effect of the constant seepage flow on the ice wall formation was investigated. It was shown that the presence of the slow flow lead to the delay in ice wall closure. In case of the flow with a velocity of more than 30 mm per day, closure of the ice wall was not observed at all in the foreseeable time.  相似文献   

'Back to the future'     

Maria Cristina Gambi  Lisa Ann Levin 《Marine Ecology》2005,26(1):1-2

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The Nevelsk tsunami on August 2, 2007: Instrumental data and numerical modeling     

A. I. Zaitsev  D. P. Kovalev  A. A. Kurkin  B. W. Levin  E. N. Pelinovsky  A. G. Chernov  A. Yalciner 《Doklady Earth Sciences》2008,421(1):867-870

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Dislocation model of the August 2, 2007, <Emphasis Type="Italic">M</Emphasis><Subscript><Emphasis Type="Italic">w</Emphasis></Subscript> 6.2 Nevelsk earthquake     

N. F. Vasilenko  B. W. Levin  A. S. Prytkov  Ch. U. Kim  H. Takahashi 《Doklady Earth Sciences》2008,422(1):1145-1149

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Bimodal character of latitudinal earthquake distributions in the pacific region as a manifestation of global seismicity   总被引：1，自引：0，他引：1  

B. V. Levin  E. V. Sasorova 《Doklady Earth Sciences》2009,424(1):175-179

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