Adaptation in a time of stress: A social-ecological perspective on changing fishing strategies in the Canadian snow crab fishery     

《Marine Policy》2015

Recent scholarship has focused attention on the dynamics and management of marine social ecological systems and on the need for developing a deeper understanding of the fishing strategies of fish harvesters. This includes an understanding of how a broad range of factors influence the strategies of those at the ‘center’ of marine social-ecological interactions. This paper reports on the findings of a survey of snow crab (Chionoecetes opilio) fishers in Southeastern Labrador conducted at a time (2005) of significant stress in the fishery. Results highlight that snow crab fishers are embedded in a social-ecological system and that shifts in fishing strategies in times of stress are a product of adapting to a dynamic, interactive set of factors that have social, economic, ecological and management aspects. Important differences between fleet sectors (larger and smaller vessels) as well as processes of learning are also described. The article concludes with a discussion of the implications for management and the utility of a holistic social-ecological perspective.  相似文献   

Patterns and drivers of asteroid abundances and assemblages on the continental margin of Atlantic Canada          下载免费PDF全文

Katie S. P. Gale  Kent Gilkinson  Jean‐François Hamel  Annie Mercier 《Marine Ecology》2015,36(3):734-752

Although continental shelf and slope environments typically exhibit high epifaunal biomass and have been subjected to increasing fishing pressure, ecological information on assemblages of non‐commercial invertebrate species from subtidal and bathyal areas remains limited. Sea stars (Echinodermata: Asteroidea), which are known to influence communities through their feeding habits, have received less attention than structural taxa such as corals and sponges. To better understand the ecological roles of asteroids on continental shelves, we investigated ~30 species and assessed their distributions and co‐occurrence with other benthic invertebrates on the shelf and slope of Eastern Canada. Using fisheries data and in situ video footage, we compiled a large dataset covering ~600,000 km² that included over 350,000 individual asteroid records (37–2243 m depth). Multivariate analyses revealed geographically distinct asteroid assemblages, with a maximal overall density at 400–500 m and the highest diversity at 500–700 m. The most abundant and densely occurring species was Ctenodiscus crispatus. We found that asteroids associate with corals, sponges, bivalves, and other echinoderms, and that depth and substrate influence these assemblages. We identified species likely to affect coexisting organisms by their burrowing behavior that can disrupt epi‐ and infauna (C. crispatus) and through predation on ecologically important corals (Hippasteria phrygiana). In addition to providing baseline distribution and ecological information for many bathyal asteroid species in the Northwest Atlantic, this work highlights the abundance and diversified roles of asteroids within continental shelf and slope ecosystems.  相似文献   

Sangay volcano, Ecuador: structural development, present activity and petrology     

Michel Monzier  Claude Robin  Pablo Samaniego  Minard L. Hall  Jo Cotten  Patricia Mothes  Nicolas Arnaud   《Journal of Volcanology and Geothermal Research》1999,90(1-2)

Sangay (5230 m), the southernmost active volcano of the Andean Northern Volcanic Zone (NVZ), sits 130 km above a >32-Ma-old slab, close to a major tear that separates two distinct subducting oceanic crusts. Southwards, Quaternary volcanism is absent along a 1600-km-long segment of the Andes. Three successive edifices of decreasing volume have formed the Sangay volcanic complex during the last 500 ka. Two former cones (Sangay I and II) have been largely destroyed by sector collapses that resulted in large debris avalanches that flowed out upon the Amazon plain. Sangay III, being constructed within the last avalanche amphitheater, has been active at least since 14 ka BP. Only the largest eruptions with unusually high Plinian columns are likely to represent a major hazard for the inhabited areas located 30 to 100 km west of the volcano. However, given the volcano's relief and unbuttressed eastern side, a future collapse must be considered, that would seriously affect an area of present-day colonization in the Amazon plain, 30 km east of the summit. Andesites greatly predominate at Sangay, there being few dacites and basalts. In order to explain the unusual characteristics of the Sangay suite—highest content of incompatible elements (except Y and HREE) of any NVZ suite, low Y and HREE values in the andesites and dacites, and high Nb/La of the only basalt found—a preliminary five-step model is proposed: (1) an enriched mantle (in comparison with an MORB source), or maybe a variably enriched mantle, at the site of the Sangay, prior to Quaternary volcanism; (2) metasomatism of this mantle by important volumes of slab-derived fluids enriched in soluble incompatible elements, due to the subduction of major oceanic fracture zones; (3) partial melting of this metasomatized mantle and generation of primitive basaltic melts with Nb/La values typical of the NVZ, which are parental to the entire Sangay suite but apparently never reach the surface and subordinate production of high Nb/La basaltic melts, maybe by lower degrees of melting at the periphery of the main site of magma formation, that only infrequently reach the surface; (4) AFC processes at the base of a 50-km-thick crust, where parental melts pond and fractionate while assimilating remelts of similar basaltic material previously underplated, producing andesites with low Y and HREE contents, due to garnet stability at this depth; (5) low-pressure fractionation and mixing processes higher in the crust. Both an enriched mantle under Sangay prior to volcanism and an important slab-derived input of fluids enriched in soluble incompatible elements, two parameters certainly related to the unique setting of the volcano at the southern termination of the NVZ, apparently account for the exceptionally high contents of incompatible elements of the Sangay suite. In addition, the low Cr/Ni values of the entire suite—another unique characteristic of the NVZ—also requires unusual fractionation processes involving Cr-spinel and/or clinopyroxene, either in the upper mantle or at the base of the crust.  相似文献   

井内偏心声源激发的三维声场的数值研究   总被引：10，自引：2，他引：8       下载免费PDF全文

沈建国  张海澜 《地球物理学报》2000,43(2):279-286

为了研究环形声波测井仪和扇区水泥胶结测井仪的工作原理,本文利用实轴积分 法计算了井内靠近井壁的偏心声源激发的声场,得到了在井壁不同位置的接收波形,分析了 直达波、井壁反射波、纵波、横波和面波在这些波形中的反映．偏心声源激发的三维声场没有 轴对称性,比井轴上的居中声源的情况复杂．  相似文献   

Varying sediment sources (Hudson Strait,Cumberland Sound,Baffin Bay) to the NW Labrador Sea slope between and during Heinrich events 0 to 4     

J. T. Andrews  D. C. Barber  A. E. Jennings  D. D. Eberl  B. Maclean  M. E. Kirby  J. S. Stoner 《第四纪科学杂志》2012,27(5):475-484

Core HU97048‐007PC was recovered from the continental Labrador Sea slope at a water depth of 945 m, 250 km seaward from the mouth of Cumberland Sound, and 400 km north of Hudson Strait. Cumberland Sound is a structural trough partly floored by Cretaceous mudstones and Paleozoic carbonates. The record extends from ～10 to 58 ka. On‐board logging revealed a complex series of lithofacies, including buff‐colored detrital carbonate‐rich sediments [Heinrich (H)‐events] frequently bracketed by black facies. We investigate the provenance of these facies using quantitative X‐ray diffraction on drill‐core samples from Paleozoic and Cretaceous bedrock from the SE Baffin Island Shelf, and on the < 2‐mm sediment fraction in a transect of five cores from Cumberland Sound to the NW Labrador Sea. A sediment unmixing program was used to discriminate between sediment sources, which included dolomite‐rich sediments from Baffin Bay, calcite‐rich sediments from Hudson Strait and discrete sources from Cumberland Sound. Results indicated that the bulk of the sediment was derived from Cumberland Sound, but Baffin Bay contributed to sediments coeval with H‐0 (Younger Dryas), whereas Hudson Strait was the source during H‐events 1–4. Contributions from the Cretaceous outcrops within Cumberland Sound bracket H‐events, thus both leading and lagging Hudson Strait‐sourced H‐events. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Exotic pollen as an indicator of variable atmospheric circulation over the Labrador Sea region during the mid to late Holocene     

Catherine A. Jessen  Sandrine Solignac  Niels Nørgaard‐Pedersen  Naja Mikkelsen  Antoon Kuijpers  Marit‐Solveig Seidenkrantz 《第四纪科学杂志》2011,26(3):286-296

Variability in the abundance of exotic (non‐native) pollen in sediment cores has long been considered as a potential proxy for changing atmospheric circulation, but the difficulty of gaining sufficient total exotic pollen and the incomplete understanding of atmospheric pollen transport patterns has hindered its application. In light of recent advances in the study of pollen transport, we present an exotic pollen record from two fjord sediment cores taken from the west (Placentia Bay, Newfoundland) and east (Narsaq Sund, Greenland) Labrador Sea as a basis for studying variations in regional atmospheric circulation. The two cores cover the last ca. 5500 years and indicate a shift in dominant spring/summer air masses at ca. 2000 (southern Greenland) and 3000 cal a BP (Newfoundland) transporting reduced concentrations of pollen from southerly and south‐westerly vegetation zones. This may suggest a shift away from more dominantly zonal atmospheric circulation (a feature of positive North Atlantic Oscillation years) to more frequent meridional circulation. These results support sea ice/sea‐surface temperature proxy reconstructions from Newfoundland, investigated as part of the same project, which also suggest increased winter atmospheric circulation during the early part of the time period studied. In this region, more positive North Atlantic Oscillation years, and therefore more zonal atmospheric circulation, are associated with increased atmospheric circulation in both the winter and the summer seasons. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Recent changes in the Labrador Sea Water within the Deep Western Boundary Current southeast of Cape Cod     

Beatriz Peña-Molino  Terrence M. Joyce 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(10):1019-1030

Water properties measured by the central mooring in the Line W mooring array southeast of Cape Cod document a large character shift during the period of November 2001 to April 2008. The observed temperature, salinity and planetary potential vorticity (PPV) anomalies manifest changes in the formation region of the water masses present at Station W, specifically upper Labrador Sea Water (uLSW), deep Labrador Sea Water (dLSW) and Overflow Water (OW). During the observation period, the minimum in the PPV anomaly field relative to the record mean PPV profile migrated from 1500 m, where it was originally found, to 700 m. Temporal changes in the vertical distribution of temperature and salinity were correlated with the PPV changes. This suggests a dLSW-dominated first half of the record versus an uLSW-dominated second half. The structure of these anomalies is consistent with observations within the Labrador Sea, and their transit time to Line W agrees well with tracer-derived times for signals spreading along the western boundary. In that context, the observed water properties at Line W in the early 2000s reflected the intense deep convection in the Labrador Sea in the mid-1990s, with less intense convection subsequently affecting lighter isopycnals. The observed velocity field is dominated by high-frequency (periods of days to months) fluctuations, however, a fraction of the velocity variability is correlated with changes in water mass properties, and indicate a gradual acceleration of the southwestward flow, with a corresponding increase in Deep Western Boundary Current transport.  相似文献   

Wetland classification in Newfoundland and Labrador using multi-source SAR and optical data integration     

Meisam Amani  Bahram Salehi  Sahel Mahdavi  Jean Granger  Brian Brisco 《地理信息系统科学与遥感》2017,54(6):779-796

A vast portion of Newfoundland and Labrador (NL) is covered by wetland areas. Notably, it is the only province in Atlantic Canada that does not have a wetland inventory system. Wetlands are important areas of research because they play a pivotal role in ecological conservation and impact human activities in the province. Therefore, classifying wetland types and monitoring their changes are crucial tasks recommended for the province. In this study, wetlands in five pilot sites, distributed across NL, were classified using the integration of aerial imagery, Synthetic Aperture Radar, and optical satellite data. First, each study area was segmented using the object-based method, and then various spectral and polarimetric features were evaluated to select the best features for identifying wetland classes using the Random Forest algorithm. The accuracies of the classifications were assessed by the parameters obtained from confusion matrices, and the overall accuracies varied between 81% and 91%. Moreover, the average producer and user accuracies for wetland classes, considering all pilot sites, were 71% and 72%, respectively. Since the proposed methodology demonstrated high accuracies for wetland classification in different study areas with various ecological characteristics, the application of future classifications in other areas of interest is promising.  相似文献   

Stable isotope analysis of some representative fish and invertebrates of the Newfoundland and Labrador continental shelf food web   总被引：3，自引：1，他引：3  

Graham D. Sherwood  George A. Rose 《Estuarine, Coastal and Shelf Science》2005,63(4):537-549

We examined stable carbon and nitrogen isotopic signatures of 17 fish and 16 invertebrate taxa common to the Newfoundland and Labrador (NL) continental shelf food web. Particular sampling emphasis was placed on Atlantic cod (Gadus morhua) and related prey species (e.g. shrimp, Pandalus borealis, and capelin, Mallotus villosus). We found highly significant (p < 0.0001) differences between near-shore (bays) and offshore (shelf edge) δ¹⁵N signatures for cod, ‘other fish’ (pooled) and invertebrates (pooled). In contrast, there were only minor differences in δ¹³C signatures of ‘other fish’ (p < 0.05) and no difference for cod and invertebrates among the two habitats. We sampled at two times of the year (January and June) and found no systematic effect of season on both δ¹³C and δ¹⁵N in cod, ‘other fish’ and invertebrates. We calculated isotopic fractionation factors for cod from the entire shelf (mixed diet) and for cod with diets composed mainly of capelin or shrimp. These values ranged between 2.2‰ and 3.9‰ for δ¹⁵N and −0.4‰ and 0.8‰ for δ¹³C and, for δ¹⁵N, may reflect diet-related differences in bioenergetic status. We discuss potential mechanisms for near-shore versus offshore enrichment of δ¹⁵N signatures, and demonstrate the implications of this spatial variation on δ¹⁵N-derived trophic position estimates.  相似文献   

Juvenile capelin (Mallotus villosus) off Newfoundland and Labrador in the 1990s     

Anderson  John T.; Dalley  Edgar L.; O'Driscoll  Richard L. 《ICES Journal of Marine Science》2002,59(5):917-928

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