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Auteur Neira, S.; Moloney, C.; Christensen, V.; Cury, P.; Shannon, L.; Arancibia, H. url  doi
openurl 
  Titre Analysing changes in the southern Humboldt ecosystem for the period 1970-2004 by means of dynamic food web modelling Type Article scientifique
  Année 2014 Publication Revue Abrégée Ecological Modelling  
  Volume 274 Numéro Pages 41-49  
  Mots-Clés Ecopath with Ecosim; Fishing patterns; Physical forcing; Regime shifts; Southern Humboldt; Trophic controls  
  Résumé A 22-group Ecopath model representing the southern Humboldt (SH) upwelling system in the year 1970 is constructed. The model is projected forward in time and fitted to available time series of relative biomass, catch and fishing mortality for the main fishery resources. The time series cover the period 1970 to 2004 and the fitting is conducted using the Ecopath with Ecosim (EwE) software version 5.1. The aim is to explore the relative importance of internal (trophic control) and external (fishing, physical variability) forcing on the dynamics of commercial stocks and the Southern Chilean food web. Wide decadal oscillations are observed in the biomass of commercial stocks during the analyzed period. Fishing mortality explains 21% of the variability in the time series, whereas vulnerability (v) parameters estimated using EwE explain an additional 20%. When a function affecting primary production (PP) is calculated by Ecosim to minimize the sum of squares of the time series, a further 28% of variability is explained. The best fit is obtained by using the fishing mortality time series and by searching for the best combination of v parameters and the PP function simultaneously, accounting for 69% of total variability in the time series. The PP function obtained from the best fit significantly correlates with independent time series of an upwelling index (UI; rho = 0.47, p<0.05) and sea surface temperature (SST; rho = -0.45, p<0.05), representing environmental conditions in the study area during the same period of time. These results suggest that the SH ecosystem experienced at least two different environmentally distinct periods in the last three decades: (i) from 1970 to 1985 a relatively warm period with low levels of upwelling and PP, and (ii) from 1985 to 2004 a relatively cold period with increased upwelling and PP. This environmental variability can explain some of the changes in the food webs. Fishing (catch rate) and the environment (bottom-up anomaly in PP) appear to have affected the SH both at the stock and at the food web level between 1970 and 2004. The vulnerability setting indicates that the effects of external forcing factors may have been mediated by trophic controls operating in the food web.  
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  Volume de collection Numéro de collection Edition  
  ISSN 0304-3800 ISBN Médium  
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  Numéro d'Appel (up) LL @ pixluser @ collection 330  
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Auteur Peraltilla, S.; Bertrand, S. url  doi
openurl 
  Titre In situ measurements of the speed of Peruvian anchovy schools Type Article scientifique
  Année 2014 Publication Revue Abrégée Fisheries Research  
  Volume 149 Numéro Pages 92-94  
  Mots-Clés Multibeam sonar; Peruvian anchovy; School speed  
  Résumé While speed of fish schools is critical information for parameterizing numerous ecosystem models and evaluating fishery management options, it is poorly documented. Here we present results of in situ measurements of the speed of Peruvian anchovy schools, a small pelagic species that sustain the world's largest mono-specific fishery. Instantaneous school speed was in average 0.6 ms(-1), authorizing theoretical maximum displacements of similar to 26 km day(-1).  
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  Langue Langue du Résumé Titre Original  
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  Volume de collection Numéro de collection Edition  
  ISSN 0165-7836 ISBN Médium  
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  Numéro d'Appel (up) LL @ pixluser @ collection 331  
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Auteur Pikitch, E.K.; Rountos, K.J.; Essington, T.E.; Santora, C.; Pauly, D.; Watson, R.; Sumaila, U.R.; Boersma, P.D.; Boyd, I.L.; Conover, D.O.; Cury, P.; Heppell, S.S.; Houde, E.D.; Mangel, M.; Plaganyi, E.; Sainsbury, K.; Steneck, R.S.; Geers, T.M.; Gownaris, N.; Munch, S.B. url  doi
openurl 
  Titre The global contribution of forage fish to marine fisheries and ecosystems Type Article scientifique
  Année 2014 Publication Revue Abrégée Fish and Fisheries  
  Volume 15 Numéro 1 Pages 43-64  
  Mots-Clés ecosystem-based management; Ecosystem service; fish; fisheries value; forage; supportive values; trade-offs  
  Résumé Forage fish play a pivotal role in marine ecosystems and economies worldwide by sustaining many predators and fisheries directly and indirectly. We estimate global forage fish contributions to marine ecosystems through a synthesis of 72 published Ecopath models from around the world. Three distinct contributions of forage fish were examined: (i) the ecological support service of forage fish to predators in marine ecosystems, (ii) the total catch and value of forage fisheries and (iii) the support service of forage fish to the catch and value of other commercially targeted predators. Forage fish use and value varied and exhibited patterns across latitudes and ecosystem types. Forage fish supported many kinds of predators, including fish, seabirds, marine mammals and squid. Overall, forage fish contribute a total of about 16.9 billion USD to global fisheries values annually, i.e. 20% of the global ex-vessel catch values of all marine fisheries combined. While the global catch value of forage fisheries was 5.6 billion, fisheries supported by forage fish were more than twice as valuable (11.3 billion). These estimates provide important information for evaluating the trade-offs of various uses of forage fish across ecosystem types, latitudes and globally. We did not estimate a monetary value for supportive contributions of forage fish to recreational fisheries or to uses unrelated to fisheries, and thus the estimates of economic value reported herein understate the global value of forage fishes.  
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  ISSN 1467-2960 ISBN Médium  
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  Numéro d'Appel (up) LL @ pixluser @ collection 332  
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Auteur Putman, N.F.; Abreu-Grobois, F.A.; Broderick, A.C.; Ciofi, C.; Formia, A.; Godley, B.J.; Stroud, S.; Pelembe, T.; Verley, P.; Williams, N. url  doi
openurl 
  Titre Numerical dispersal simulations and genetics help explain the origin of hawksbill sea turtles in Ascension Island Type Article scientifique
  Année 2014 Publication Revue Abrégée Journal of Experimental Marine Biology and Ecology  
  Volume 450 Numéro Special Issue Pages 98-108  
  Mots-Clés dispersal; mtDNA; ocean circulation model; Sea turtle  
  Résumé Long-distance dispersal and ontogenetic shifts in habitat use are characteristic of numerous marine species and have important ecological, evolutionary, and management implications. These processes, however, are often challenging to study due to the vast areas involved. We used genetic markers and simulations of physical transport within an ocean circulation model to gain understanding into the origin ofjuvenile hawksbill sea turtles (Eretmochelys imbricata) found at Ascension Island, a foraging ground that is thousands of kilometers from known nesting beaches. Regional origin of genetic markers suggests that turtles are from Western Atlantic (86%) and Eastern Atlantic (14%) rookeries. In contrast, numerical simulations of transport by ocean currents suggest that passive dispersal from the western sources would be negligible and instead would primarily be from the East, involving rookeries along Western Africa (i.e., Principe Island) and, potentially, from as far as the Indian Ocean (e.g., Mayotte and the Seychelles). Given that genetic analysis identified the presence of a haplotype endemic to Brazilian hawksbill rookeries at Ascension, we examined the possible role of swimming behavior by juvenile hawksbills from NE Brazil on their current-borne transport to Ascension Island by performing numerical experiments in which swimming behavior was simulated for virtual particles (simulated turtles). We found that oriented swimming substantially influenced the distribution of particles, greatly altering the proportion of particles dispersing into the North Atlantic and South Atlantic. Assigning location-dependent orientation behavior to particles allowed them to reach Ascension Island, remain in favorable temperatures, encounter productive foraging areas, and return to the vicinity of their natal site. The age at first arrival to Ascension (4.5-5.5 years) of these particles corresponded well to estimates of hawksbill age based on their size. Our findings suggest that ocean currents and swimming behavior play an important role in the oceanic ecology of sea turtles and other marine animals.  
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  Volume de collection Numéro de collection Edition  
  ISSN 0022-0981 ISBN Médium  
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  Numéro d'Appel (up) LL @ pixluser @ collection 333  
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Auteur Torres-Irineo, E.; Gaertner, D.; Chassot, E.; Dreyfus-Leon, M. url  doi
openurl 
  Titre Changes in fishing power and fishing strategies driven by newtechnologies : the case of tropical tuna purse seiners in the easternAtlantic Ocean Type Article scientifique
  Année 2014 Publication Revue Abrégée Fisheries Research  
  Volume 155 Numéro Pages 10-19  
  Mots-Clés  
  Résumé Technological advancements can influence both the fishing power of a fleet and the fishing strategies itemploys. To investigate these potential linkages, we examined almost three decades of data (1981&8211;2008)from French tropical tuna purse seiners operating in the eastern Atlantic Ocean. Applying a sequence ofstatistical methods at different temporal and spatial scales, we analyzed two indicators of fishing power(sets per boat-day on fish aggregating devices (FADs) and sets per boat-day on free-swimming schools)each of which represent a distinct fishing mode. Our results show that the increasing modernizationof this fleet has led to increases in both fishing power and the available number of fishing strategies tochoose from. A key output of this analysis was the breakdown of fishing power time series (for each fishingmode) into separate periods of continuous years during which catchability was assumed to be constant,thus identifying regime shifts. This partitioning allowed us to identify when key changes occurred inthe fishery. Changes in FAD-associated fishing were mostly driven by the introduction of radio beacons(early 1990s) which lead to an increase in fishing effort and an expansion of fishing grounds (directeffect) and the implementation of time-area management measures which resulted in a fragmentationof the traditional fishing grounds in the 2000s (indirect effect). During the same period, fishing on free-swimming schools also increased despite the biomass of stocks decreasing and fishing grounds remainingunchanged. This suggests these increases were driven by improvements in fish detection technology (e.g.,bird radars, sonar). These identified increases are not entirely unexpected: indeed it is widely recognizedthat fishing power in the purse seine tuna fishery has increased over time. However, these increases donot necessarily occur linearly. Thus, understanding how fishing power is changing over time (such asdetermining when regime shifts occur) is critical to improving the CPUE standardization procedure intropical tuna purse seine fisheries.  
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  Langue eng Langue du Résumé Titre Original  
  Éditeur de collection Titre de collection Titre de collection Abrégé  
  Volume de collection Numéro de collection Edition  
  ISSN 0165-7836 ISBN Médium  
  Région Expédition Conférence  
  Notes Approuvé pas de  
  Numéro d'Appel (up) LL @ pixluser @ collection 335  
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