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Auteur Salvetat, J.; Lebourges-Dhaussy, A.; Travassos, P.; Gastauer, S.; Roudaut, G.; Vargas, G.; Bertrand, A. doi  openurl
  Titre In situ target strength measurement of the black triggerfish Melichthys niger and the ocean triggerfish Canthidermis sufflamen Type Article scientifique
  Année 2020 Publication Revue Abrégée Mar. Freshw. Res.  
  Volume 71 Numéro 9 Pages (down) 1118-1127  
  Mots-Clés acoustics; aggregating devices fads; archipelago; atlantic; behavior; biomass estimation; frequency; north-east Brazil; shore fishes; small tuna; spinner dolphins; swimbladder; target strength-length relationships; tropical ecosystem; tropical tuna; underwater acoustics; underwater video  
  Résumé Triggerfish are widely distributed in tropical waters where they play an important ecological role. The black triggerfish Melichthys niger may be the dominant species around oceanic tropical islands, whereas pelagic triggerfish, such as the ocean triggerfish Canthidermis sufflamen, can assemble around fish aggregating devices (FADs) where they are a common bycatch of tuna fisheries. In this study we combined acoustic and optical recordings to provide the first in situ target strength (TS) measurement of black and ocean triggerfish. Data were collected in the Archipelago of Fernando de Noronha off north-east Brazil. The mean TS of a 27.8-cm-long black triggerfish at 70 and 200 kHz was -39.3 dB re 1 m(2) (CV = 14.0%) and -38.9 dB re 1 m(2) (CV = 14.4%) respectively. The mean TS values of ocean triggerfish (with a size range of 39-44 cm) at 70 and 200 kHz were -36.0 dB re 1 m(2) (CV = 15.7%) and -33.3 dB re 1 m(2) (CV = 14.0%) respectively. This work opens up the field for acoustic biomass estimates. In addition, we have shown that TS values for ocean triggerfish are within the same range as those of small tunas. Therefore, acoustic data transmitted from FADs equipped with echosounders can introduce a bias in tuna acoustic biomass estimation and lead to increased rates of bycatch.  
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  ISSN 1323-1650 ISBN Médium  
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  Notes WOS:000562536400007 Approuvé pas de  
  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2872  
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Auteur Sempo, G.; Dagorn, L.; Robert, M.; Deneubourg, J.-L. url  doi
openurl 
  Titre Impact of increasing deployment of artificial floating objects on the spatial distribution of social fish species Type Article scientifique
  Année 2013 Publication Revue Abrégée Journal of Applied Ecology  
  Volume 50 Numéro 5 Pages (down) 1081-1092  
  Mots-Clés behaviour-based modelling; Bycatch; Fad; Fob; sustainable fishery; tuna  
  Résumé * Approximately 300 pelagic fish species naturally aggregate around floating objects (FOBs) at the surface of the oceans. Currently, more than 50% of the world catch of tropical tuna comes from the industrial tuna fisheries around drifting FOBs. Greater understanding of the complex decision-making processes leading to this aggregation pattern and the impact of the massive release of artificial FOBs by fishermen on the spatial distribution and management of tuna is needed. * We analyse how the interplay between social (relationships between individuals) and non-social (responses to the environment) behaviours may affect the spatial distribution of a population in a multi-FOB environment. Taking the example of tropical tunas associating with FOBs and using differential equations and stochastic simulations, we examine how, when increasing the number of FOBs, fish aggregation dynamics and the distribution of the population among patches are affected by the population size, level of sociality and the natural retentive and/or attractive forces of FOBs on individual tuna. * Our model predicts that, depending on the species' level of sociality, fish will be scattered among FOBs or aggregated around a single FOB based on the number of FOBs deployed in a homogeneous oceanic region. * For social species, we demonstrated that the total fish catch is reduced with increasing FOBs number. Indeed, for each size of population, there are a number of FOBs minimizing the total population of fish associated with FOBs and another number of FOBs maximizing the total population of associated fish. * Synthesis and applications. In terms of fisheries management, the total catch volume is directly linked to the total number of floating objects (FOBs) for non-social species, and any limit on the number of sets would then result in a limit on the total catch. For social species (e.g. tuna), however, increasing the number of FOBs does not necessarily lead to an increase in the total catch, which is a non-intuitive result. Indeed, our model shows that, for specific values of the parameters, deploying a greater number of FOBs in the water (all other parameters being constant) does not necessarily help fishermen to catch more tuna, but does increase the level of fishing effort and bycatch.  
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  ISSN 1365-2664 ISBN Médium  
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  Numéro d'Appel LL @ pixluser @ collection 265  
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Auteur Dalongeville, A.; Andrello, M.; Mouillot, D.; Albouy, C.; Manel, S. doi  openurl
  Titre Ecological traits shape genetic diversity patterns across the Mediterranean Sea: a quantitative review on fishes Type Article scientifique
  Année 2016 Publication Revue Abrégée J. Biogeogr.  
  Volume 43 Numéro 4 Pages (down) 845-857  
  Mots-Clés atlantic bluefin tuna; bass dicentrarchus-labrax; climate-change; cod gadus-morhua; ecological traits; effective population-size; genetic diversity; gilthead sea; life-history traits; marine fishes; marine populations; Mediterranean Sea; microsatellite markers; microsatellites; mitochondrial; mitochondrial DNA; molecular markers; population genetics  
  Résumé AimWe set out to identify the determinants of the variation in genetic diversity among fish species and test whether multi-species genetic diversity is randomly distributed in space. LocationMediterranean Sea. MethodsWe collected genetic diversity data from 39 published studies on Mediterranean fishes (31 species) along with the spatial coordinates of the sampling sites. We focused on microsatellite heterozygosity (151 data points) and mitochondrial haplotype diversity (201 data points). We used linear regressions to link genetic diversity and 11 ecological traits. We also tested for spatial autocorrelation and trends in the residuals. ResultsAmong-species variation in microsatellite heterozygosity was explained by three ecological traits: vertical distribution, migration type and body length. Variation in mitochondrial haplotype diversity was also explained by vertical distribution and migration type, and by reproductive strategy (semelparity). However, vertical distribution and migration type showed opposite effects on microsatellites and mitochondrial diversity. After accounting for the effects of ecological traits, no spatial pattern was detected, except for one of the species considered. Main conclusionsEcological factors explain an important proportion of the among-species genetic diversity. These results suggest that life history strategies of the species influence the variation of microsatellite diversity indirectly through their effect on effective population size, while the spatial variations of genetic diversity seem to be too complex to be identified in our analysis. We found very different effects of traits on mitochondrial and nuclear DNA diversity, which can be explained by the specificities of mitochondrial DNA (absence of recombination, maternal inheritance and non-neutrality).  
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  ISSN 0305-0270 ISBN Médium  
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  Numéro d'Appel MARBEC @ alain.herve @ collection 1627  
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Auteur Walker, E.; Rivoirard, J.; Gaspar, P.; Bez, N. url  doi
openurl 
  Titre From forager tracks to prey distributions: an application to tuna vessel monitoring systems (VMS) Type Article scientifique
  Année 2015 Publication Ecological Applications Revue Abrégée  
  Volume 25 Numéro 3 Pages (down) 826-833  
  Mots-Clés Gps; multivariate geostatistics; presence index; spatiotemporal distribution; trajectometry; Tropical tuna; vessel monitoring system (VMS)  
  Résumé In the open ocean, movements of migratory fish populations are typically surveyed using tagging methods that are subject to low sample sizes for archive tags, except for a few notable examples, and poor temporal resolution for conventional tags. Alternatively, one can infer patterns of movement of migratory fish by tracking movements of their predators, i.e., fishing vessels, whose navigational systems (e.g., GPS) provide accurate and frequent VMS (vessel monitoring system) records of movement in pursuit of prey. In this paper, we develop a state-space model that infers the foraging activities of fishing vessels from their tracks. Second, we link foraging activities to probabilities of tuna presence. Finally, using multivariate geostatistical interpolation (cokriging) we map the probability of tuna presence together with their estimation variances and produce a time series of indices of abundance. While the segmentation of the trajectories is validated by observers' data, the present VMS-index is compared to catch rate and proved to be useful for management perspectives. The approach reported in this manuscript extends beyond the case study considered. It can be applied to any foragers that engage in an attempt of capture when they see prey and for whom this attempt is linked to a tractable change in behavior.  
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  Volume de collection Numéro de collection Edition  
  ISSN 1051-0761 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1116  
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Auteur Escalle, L.; Gaertner, D.; Chavance, P.; Delgado de Molina, A.; Ariz, J.; Mérigot, B. doi  openurl
  Titre Forecasted consequences of simulated FAD moratoria in the Atlantic and Indian Oceans on catches and bycatches Type Article scientifique
  Année 2017 Publication Revue Abrégée ICES J. Mar. Sci.  
  Volume 74 Numéro 3 Pages (down) 780-792  
  Mots-Clés area; Bycatch; ecosystem approach to fisheries; fish aggregation device; management; Megafauna; Monte Carlo simulations; Purse-seine fishery; time; time-area restriction; tropical tuna purse-seine fishery; Tuna  
  Résumé Given the increasingly extensive use of drifting fish aggregation devices (FADs) by the purse-seine fisheries targeting tropical tunas, fishing effort restrictions have been introduced to manage tropical tuna stocks. However, these measures are focused on the protection of juvenile tunas and do not take account of the potential impact on bycatch or associated megafauna (whales and whale sharks). An iterative “fishing-day” Monte Carlo simulation model was developed to investigate the consequences on tropical tunas and bycatch of introducing extensive area 6-month moratoria on FAD activities. The model allowed for variability in a range of plausible values of the parameters characterizing the fishing operations conducted by European purse-seiners in the eastern tropical Atlantic and western Indian Oceans for the period 2005-2014. Monte Carlo simulations, using probabilities based on these fishery data, were carried out for the French and Spanish fishing fleets separately to account for differences in fishing strategies. The models predicted a decrease in FAD sets and an increase in free school sets. As a consequence, the catch of small tuna (<10 kg) decreased while the catch of large tuna (>= 10 kg) increased, leading to an overall increase in tuna catch of 100-200 tons/year/vessel in the Atlantic Ocean, and a decrease of 400-1500 tons/year/vessel in the Indian Ocean. The bycatch decreased in the Indian Ocean, while in the Atlantic Ocean billfishes, turtles and chondrichthyans bycatch increased slightly and other bony fishes decreased. Because fishing practices were modified, whale and whale shark associated sets increased slightly in the Indian Ocean.  
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  ISSN 1054-3139 ISBN Médium  
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  Numéro d'Appel MARBEC @ alain.herve @ collection 2105  
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