Patterns in the spatial distribution of Peruvian anchovy (Engraulis ringens) revealed by spatially explicit fishing data   总被引：1，自引：0，他引：1  

Sophie Bertrand  Erich Díaz  Matthieu Lengaigne 《Progress in Oceanography》2008,79(2-4):379

Peruvian anchovy (Engraulis ringens) stock abundance is tightly driven by the high and unpredictable variability of the Humboldt Current Ecosystem. Management of the fishery therefore cannot rely on mid- or long-term management policy alone but needs to be adaptive at relatively short time scales. Regular acoustic surveys are performed on the stock at intervals of 2 to 4 times a year, but there is a need for more time continuous monitoring indicators to ensure that management can respond at suitable time scales. Existing literature suggests that spatially explicit data on the location of fishing activities could be used as a proxy for target stock distribution. Spatially explicit commercial fishing data could therefore guide adaptive management decisions at shorter time scales than is possible through scientific stock surveys. In this study we therefore aim to (1) estimate the position of fishing operations for the entire fleet of Peruvian anchovy purse–seiners using the Peruvian satellite vessel monitoring system (VMS), and (2) quantify the extent to which the distribution of purse–seine sets describes anchovy distribution. To estimate fishing set positions from vessel tracks derived from VMS data we developed a methodology based on artificial neural networks (ANN) trained on a sample of fishing trips with known fishing set positions (exact fishing positions are known for approximately 1.5% of the fleet from an at-sea observer program). The ANN correctly identified 83% of the real fishing sets and largely outperformed comparative linear models. This network is then used to forecast fishing operations for those trips where no observers were onboard. To quantify the extent to which fishing set distribution was correlated to stock distribution we compared three metrics describing features of the distributions (the mean distance to the coast, the total area of distribution, and a clustering index) for concomitant acoustic survey observations and fishing set positions identified from VMS. For two of these metrics (mean distance to the coast and clustering index), fishing and survey data were significantly correlated. We conclude that the location of purse–seine fishing sets yields significant and valuable information on the distribution of the Peruvian anchovy stock and ultimately on its vulnerability to the fishery. For example, a high concentration of sets in the near coastal zone could potentially be used as a warning signal of high levels of stock vulnerability and trigger appropriate management measures aimed at reducing fishing effort.  相似文献   

Impacts of Kelvin wave forcing in the Peru Humboldt Current system: Scenarios of spatial reorganizations from physics to fishers   总被引：2，自引：1，他引：1  

Sophie Bertrand  Boris Dewitte  Jorge Tam  Erich Díaz  Arnaud Bertrand   《Progress in Oceanography》2008,79(2-4):278

Because climate change challenges the sustainability of important fish populations and the fisheries they support, we need to understand how large scale climatic forcing affects the functioning of marine ecosystems. In the Humboldt Current system (HCS), a main driver of climatic variability is coastally-trapped Kelvin waves (KWs), themselves originating as oceanic equatorial KWs. Here we (i) describe the spatial reorganizations of living organisms in the Humboldt coastal system as affected by oceanic KWs forcing, (ii) quantify the strength of the interactions between the physical and biological component dynamics of the system, (iii) formulate hypotheses on the processes which drive the redistributions of the organisms, and (iv) build scenarios of space occupation in the HCS under varying KW forcing. To address these questions we explore, through bivariate lagged correlations and multivariate statistics, the relationships between time series of oceanic KW amplitude (TAO mooring data and model-resolved baroclinic modes) and coastal Peruvian oceanographic data (SST, coastal upwelled waters extent), anchoveta spatial distribution (mean distance to the coast, spatial concentration of the biomass, mean depth of the schools), and fishing fleet statistics (trip duration, searching duration, number of fishing sets and catch per trip, features of the foraging trajectory as observed by satellite vessel monitoring system). Data sets span all or part of January 1983 to September 2006. The results show that the effects of oceanic KW forcing are significant in all the components of the coastal ecosystem, from oceanography to the behaviour of the top predators – fishers. This result provides evidence for a bottom-up transfer of the behaviours and spatial stucturing through the ecosystem. We propose that contrasting scenarios develop during the passage of upwelling versus downwelling KWs. From a predictive point of view, we show that KW amplitudes observed in the mid-Pacific can be used to forecast which system state will dominate the HCS over the next 2–6 months. Such predictions should be integrated in the Peruvian adaptive fishery management.  相似文献   

Tropical peatlands: current plight and the need for responsible management          下载免费PDF全文

Sophie M. Green  Susan Page 《Geology Today》2017,33(5):174-179

Peatlands are important carbon stores, but when drained (e.g. for agriculture), this carbon is released to the atmosphere as carbon dioxide (CO₂, a greenhouse gas). Globally, at least 15% of peatlands have been drained, mostly in Europe and South‐east Asia, and are responsible for 5% of human‐derived CO₂ emissions. Peatlands have been exploited for generations, but not without local to global consequences, particularly in South‐East Asia. However, recognition of the continuous environmental toll caused by peatland exploitation is leading to a need to change attitudes and practices, in order to propel a move towards a more balanced and responsible use of peat in both northern and tropical peatlands.  相似文献   

Temperature And Wind Velocity Oscillations Along a Gentle Slope During Sea-Breeze Events     

Sophie?BastinEmail author  Philippe?Drobinski 《Boundary-Layer Meteorology》2005,114(3):573-594

The flow structure on a gentle slope at Vallon dOl in the northern suburbs of Marseille in southern France has been documented by means of surface wind and temperature measurements collected from 7 June to 14 July 2001 during the ESCOMPTE experiment. The analysis of the time series reveals temperature and wind speed oscillations during several nights (about 60--90 min oscillation period) and several days (about 120–180 min oscillation period) during the whole observing period. Oscillating katabatic winds have been reported in the literature from theoretical, experimental and numerical studies. In the present study, the dynamics of the observed oscillating katabatic winds are in good agreement with the theory.In contrast to katabatic winds, no daytime observations of oscillating anabatic upslope flows have ever been published to our knowledge, probably because of temperature inversion break-up that inhibits upslope winds. The present paper shows that cold air advection by a sea breeze generates a mesoscale horizontal temperature gradient, and hence baroclinicity in the atmosphere, which then allows low-frequency oscillations, similar to a katabatic flow. An expression for the oscillation period is derived that accounts for the contribution of the sea-breeze induced mesoscale horizontal temperature gradient. The theoretical prediction of the oscillation period is compared to the measurements, and good agreement is found. The statistical analysis of the wind flow at Vallon dOl shows a dominant north-easterly to easterly flow pattern for nighttime oscillations and a dominant south-westerly flow pattern for daytime oscillations. These results are consistent with published numerical simulation results that show that the air drains off the mountain along the maximum slope direction, which in the studied case is oriented south-west to north-east.  相似文献   

Residential mobility trajectories and integration in Douala and Bafoussam,Cameroon     

Aristide Yemmafouo  Chrétien Ngouanet  Romeo Keumo Songong  Nicodème Djikeng Teufack  Sophie Ariane Djuidje 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2017,117(2):105-116

Abstract

This study examines how migrant households relocate their homes in two Cameroonian cities over the course of lifetimes or even generations. The central claim is that homeownership is the ultimate sign of integration into city life. Using qualitative and quantitative research methods (218 interviews, 30 focus groups and a household survey, sample size 686), the study argues that three key factors explain why people move: the quality of housing they can affords, the proximity to a workplace and the potential for homeownership. Three residential model trajectories are identified. The first describes a journey from being a new migrant who is a guest of family or friends in the city centre to being a married family with kids owning a home in the urban periphery. The second model continues that journey by returning back to the city centre in pursuit of more convenient, high-status home location (if finances permit). A third model describes moves to sites all over the city later in life as older individuals seek to maximize family income in the way they use multiple properties. Understanding residential mobility patterns has the potential to lead to a better public policies and more effective private investments in the housing sector.  相似文献   

Dynamics of a wave-dominated tidal inlet and influence on adjacent beaches,Currumbin Creek,Gold Coast,Australia     

Bruno Castelle  Julien Bourget  Nathalie Molnar  Darrell Strauss  Sophie Deschamps  Rodger Tomlinson 《Coastal Engineering》2007

Currumbin Creek on the Australian Gold Coast is a wave-dominated tidal inlet which exhibits a particularly active morphology. The recent history of Currumbin Creek entrance has seen rapid growth of the entrance for access to the ocean by fishermen, as a world class surfing site, and as a recreational area. Before the construction of two groynes in the 70's, Currumbin Creek entrance was highly variable in terms of inlet location and sand bar characteristics due to a cyclical behaviour of spit migration. Nowadays, the entrance is stabilised. However, natural processes continue with the entrance infilling causing flood and navigation issues, resulting in a regular dredging program to maintain an open entrance and for regular beach nourishment plans.  相似文献   

Habitats and Characteristics of the Sea Urchins Lytechinus variegatus and Arbacia punctulata (Echinodermata) on the Florida Gulf-Coast Shelf     

Sophie K. Hill  & John M. Lawrence 《Marine Ecology》2003,24(1):15-30

Abstract Lytechinus variegatus and Arbacia punctulata have been studied primarily in inshore, shallow‐water areas. However, they are abundant in deeper waters on the Florida gulf‐coast shelf and seem important components of the benthic communities there. Lytechinus variegatus occurs alone on sand bottoms and A. punctulata occurs alone on rubble bottoms in these deeper waters. The species also co‐occur there on ­heterogeneous bottoms, each in a distinct microhabitat with A. punctulata on rubble and L. variegatus on surrounding sand. Characteristics of the sea urchins in these different deeper‐water habitat types and at one nearshore site with a heterogeneous rubble‐sand bottom were compared. Over the 2‐year study, offshore individuals of both species had low gut and gonad indices and the maximum size of individuals did not change. This suggests food limitation and low production. Offshore, A. punctulata had a higher Aristotle's lantern index and lower gut and gonad indices in populations where it ­co‐occurred with L. variegatus compared to populations where it occurred alone. The ­Aristotle's lantern index of L. variegatus did not differ among the offshore sites. Neither species seemed food limited at the nearshore site. Although productivity is lower at the offshore sites, both species extend their distribution and reproduction potential by existing there.  相似文献   

δ³⁰Si and δ²⁹Si Determinations on USGS BHVO-1 and BHVO-2 Reference Materials with a New Configuration on a Nu Plasma Multi-Collector ICP-MS     

Kathrin Abraham  Sophie Opfergelt  François Fripiat  Anne-Julie Cavagna  Jeroen T.M. de Jong  Stephen F. Foley  Luc André  Damien Cardinal 《Geostandards and Geoanalytical Research》2008,32(2):193-202

We report silicon isotopic determinations for USGS rock reference materials BHVO-1 and BHVO-2 using a Nu Plasma multi-collector (MC)-ICP-MS, upgraded with a new adjustable entrance slit, to obtain medium resolution, as well as a stronger primary pump and newly designed sampler and skimmer cones ("B" cones). These settings, combined with the use of collector slits, allowed a resolution to be reached that was sufficient to overcome the ¹⁴N¹⁶O and ¹⁴N₂ interferences overlying the ³⁰Si and the ²⁸Si peaks, respectively, in an earlier set-up. This enabled accurate measurement of both δ³⁰Si and δ²⁹Si. The δ value is expressed in per mil variation relative to the NBS 28 quartz reference material. Based on data acquired from numerous sessions spread over a period of six months, we propose a recommended average δ³⁰Si of −0.33 ± 0.05‰ and −0.29 ± 0.11‰ (2se) for BHVO-1 and BHVO-2, respectively. Our BHVO grand mean silicon isotope composition (δ³⁰Si =−0.31 ± 0.06‰) is significantly more negative than the only published value for BHVO-2, but is in very good agreement with the recently established average value of ocean island basalts (OIB), confirming the conclusion that the OIB reservoir has a distinct isotopic composition from the solar reservoir as sampled by chondrites.  相似文献   

Households’ Resilience to Hurricanes in Coastal Communities of Oaxaca,Mexico     

V. Sophie Avila-Foucat  A. F. Martínez 《社会与自然资源》2018,31(7):807-821

Hurricanes represent a common threat to coastal communities, affecting livelihood strategies and assets. Households are resilient if they can recover from a stress or shock while maintaining and arranging assets to secure a sustainable livelihood. The objective of this research is to measure the degree of resilience in the coastal households of Oaxaca, Mexico, following a hurricane using the asset approach and describing diversity, connectivity, and slow variables. The results show different degrees of resilience among the households and that social, natural, and financial capital are relevant to resilience. The diversification of income, savings, community help, natural resource use, and government transfers is among the most important assets. In particular, social capital and natural capital determine the structure and dynamics of the system.  相似文献   

Joint interpretation of the hydrochemistry of two neighbouring basins by N-way multivariate methods     

Rosario Soledad Barranquero  Marcelo Raúl Varni  Rafael Pardo  Marisol Vega  María Emilia Zabala  Víctor Alejandro Ruiz de Galarreta 《Environmental Earth Sciences》2016,75(4):335

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