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Auteur Darnaude, A.M.; Hunter, E. doi  openurl
  Titre Validation of otolith delta O-18 values as effective natural tags for shelf-scale geolocation of migrating fish Type Article scientifique
  Année 2018 Publication Revue Abrégée Mar. Ecol.-Prog. Ser.  
  Volume 598 Numéro Pages 167-185  
  Mots-Clés atlantic bluefin tuna; carbon stable-isotopes; cod gadus-morhua; Fish migration; life-history; Natural tag; north-sea plaice; Oxygen; oxygen-isotope fractionation; Plaice; Pleuronectes platessa; pleuronectes-platessa l; population regulation; Site fidelity; Stable isotopes; stock structure; western-australia  
  Résumé The oxygen isotopic ratio of fish otoliths is increasingly used as a 'natural tag' to assess provenance in migratory species, with the assumption that variations in delta O-18 values closely reflect individual ambient experience of temperature and/or salinity. We employed archival tag data and otoliths collected from a shelf-scale study of the spatial dynamics of North Sea plaice Pleuronectes platessa L., to examine the limits of otolith delta O-18-based geolocation of fish during their annual migrations. Detailed intra-annual otolith delta O-18 measurements for 1997-1999 from individuals of 3 distinct sub-stocks with different spawning locations were compared with delta O-18 values predicted at the monthly, seasonal and annual scales, using predicted sub-stock specific temperatures and salinities over the same years. Spatio-temporal variation in expected delta O-18 values (-0.23 to 2.94%) mainly reflected variation in temperature, and among-zone discrimination potential using otolith delta O-18 varied greatly by temporal scale and by time of year. Measured otolith delta O-18 values (-0.71 to 3.09%) largely mirrored seasonally predicted values, but occasionally fell outside expected delta O-18 ranges. Where mismatches were observed, differences among sub-stocks were consistently greater than predicted, suggesting that in plaice, differential sub-stock growth rates and physiological effects during oxygen fractionation enhance geolocation potential using otolith delta O-18. Comparing intra-annual delta O-18 values over several consecutive years for individuals with contrasted migratory patterns corroborated a high degree of feeding and spawning site fidelity irrespective of the sub-stock. Informed interpretation of otolith delta O-18 values can therefore provide relatively detailed fisheries-relevant data not readily obtained by conventional means.  
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  Langue English Langue du Résumé Titre Original  
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  Volume de collection (down) Numéro de collection Edition  
  ISSN 0171-8630 ISBN Médium  
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  Numéro d'Appel MARBEC @ alain.herve @ collection 2377  
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Auteur Gaertner, D. url  doi
openurl 
  Titre Estimates of historic changes in total mortality and selectivity for Eastern Atlantic skipjack (Katsuwonus pelamis) from length composition data Type Article scientifique
  Année 2010 Publication Revue Abrégée Aquatic Living Resources  
  Volume 23 Numéro Pages 3-11  
  Mots-Clés analysis; Bayesian; change-point; Fad; Fishing; Mortality; rate; Skipjack; strategies; tuna  
  Résumé Catch-at-size data of the eastern Atlantic skipjack were used to estimate changes in total mortality from 1969 to 2007. We used a transitional model of mean length that generalized the Beverton-Holt mortality estimator to allow change in mortality rate under nonequilibrium conditions. Then, from homogeneous periods of time, length-converted catch curves were used to access qualitative changes in selectivity patterns for two surface fisheries (the baitboat fishery operating from Dakar, Senegal, and the European and associated purse seine fisheries). To explore the impact of catch on the mortality rate, a Bayesian change-point analysis was conducted on the catch time series to detect concomitant variation between mortality rates and catch. Finally, potential causes of these changes are discussed in relation to the implementation of new fishing technology, such fish aggregating devices (FAD). The general pattern depicted by total mortality is in agreement with previous knowledge on this fishery: a state of complete or practically complete exploitation during the nineties followed by the decrease in nominal purse seine fishing effort in the last decade, combined with the effect of a seasonal moratorium on FAD fishing operations. There was no evidence of a change in selectivity between the two contrasted periods of time considered: 1969-1979 and 1986-1999; the second period being characterized by the introduction of new technology onboard vessels. In contrast, the covariation over time between total catch and mortality rate three years later highlights the effect of the fishing pressure on the stock of eastern Atlantic skipjack.  
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  Volume de collection (down) Numéro de collection Edition  
  ISSN 0990-7440 ISBN Médium  
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  Numéro d'Appel LL @ pixluser @ collection 74  
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Auteur Gaertner, D.; Hallier, J.-P. url  doi
openurl 
  Titre Tag shedding by tropical tunas in the Indian Ocean and other factors affecting the shedding rate Type Article scientifique
  Année 2015 Publication Fisheries Research Revue Abrégée  
  Volume 163 Numéro Si Pages 98-105  
  Mots-Clés averaging; Bayesian model; Beta-binomial model; Indian Ocean; Shedding rate; Tagging data; Tropical tunas  
  Résumé A key objective of the Regional Tuna Tagging Project Indian Ocean was to estimate tag-shedding rates, Type-I (immediate tag shedding) and Type-II (long-term tag shedding). To assess this, a series of double-tagging experiments (26,899 double tags released with 4555 recoveries) were conducted as part of the broader tagging program. After omitting data from tags placed by less experienced taggers, the results of our analyses did not show any evidence that individual differences between taggers (i.e., a tagger effect) impacted estimates of tag-shedding rates. However, it was shown that the probability of retaining the second tag (inserted in the left side of the fish) was larger than retaining the first tag (inserted in the right side, i.e., the side typically tagged in single-tagging experiments). We used a Bayesian model averaging approach to account for model uncertainty in the estimates of the parameters a and L used to calculate the probability of tag retention Q(t)= alpha e-((L t)) for the right tag. The parameter estimates were alpha = 0.993 and L (per year) = 0.030 (skipjack); alpha = 0.972 and L (per year) = 0.040 (yellowfin); and alpha = 0.990 and L (per year) = 0.021 (bigeye). These results agree with estimates obtained by other large-scale tropical tuna tagging projects. We showed that tag loss has a moderate impact on the underestimation of the exploitation rate (bias = 2-6% depending on the tuna species). However, non-reporting leads to a bias of around 7% when using the high reporting rate estimate of purse seiners. Finally, tag shedding (specifically Type-II shedding) modified the individual weights of the samples of recaptures. Consequently, the total instantaneous mortality estimates (Z; calculated from mean times-at-large) were reduced by a range of 1-3%.  
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  Editeur Lieu de Publication Éditeur Murua, H.; Marsac, F.; Eveson, J.P.  
  Langue Langue du Résumé Titre Original  
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  Volume de collection (down) Numéro de collection Edition  
  ISSN 0165-7836 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1104  
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Auteur Keller, S.; Quetglas, A.; Puerta, P.; Bitetto, I.; Casciaro, L.; Cuccu, D.; Esteban, A.; Garcia, C.; Garofalo, G.; Guijarro, B.; Josephides, M.; Jadaud, A.; Lefkaditou, E.; Maiorano, P.; Manfredi, C.; Marceta, B.; Micallef, R.; Peristeraki, P.; Relini, G.; Sartor, P.; Spedicato, M.T.; Tserpes, G.; Hidalgo, M. doi  openurl
  Titre Environmentally driven synchronies of Mediterranean cephalopod populations Type Article scientifique
  Année 2017 Publication Revue Abrégée Prog. Oceanogr.  
  Volume 152 Numéro Pages 1-14  
  Mots-Clés atlantic bluefin tuna; balearic sea; Cephalopods; Dynamic factor analysis; ecological niche approach; fisheries; fluctuations; hake merluccius-merluccius; Illex coindetii; life-history; Mediterranean; medits; octopus; Octopus vulgaris; squid; Synchrony; time-series  
  Résumé The Mediterranean Sea is characterized by large scale gradients of temperature, productivity and salinity, in addition to pronounced mesoscale differences. Such a heterogeneous system is expected to shape the population dynamics of marine species. On the other hand, prevailing environmental and climatic conditions at whole basin scale may force spatially distant populations to fluctuate in synchrony. Cephalopods are excellent case studies to test these hypotheses owing to their high sensitivity to environmental conditions. Data of two cephalopod species with contrasting life histories (benthic octopus vs nectobenthic squid), obtained from scientific surveys carried out throughout the Mediterranean during the last 20 years were analyzed. The objectives of this study and the methods used to achieve them (in parentheses) were: (i) to investigate synchronies in spatially separated populations (decorrelation analysis); (ii) detect underlying common abundance trends over distant regions (dynamic factor analysis, DFA); and (iii) analyse putative influences of key environmental drivers such as productivity and sea surface temperature on the population dynamics at regional scale (general linear models, GLM). In accordance with their contrasting spatial mobility, the distance from where synchrony could no longer be detected (decorrelation scale) was higher in squid than in octopus (349 vs 217 km); for comparison, the maximum distance between locations was 2620 km. The DFA revealed a general increasing trend in the abundance of both species in most areas, which agrees with the already reported worldwide proliferation of cephalopods. DFA results also showed that population dynamics are more similar in the eastern than in the western Mediterranean basin. According to the GLM models, cephalopod populations were negatively affected by productivity, which would be explained by an increase of competition and predation by fishes. While warmer years coincided with declining octopus numbers, areas of high sea surface temperature showed higher densities of squid. Our results are relevant for regional fisheries management and demonstrate that the regionalisation objectives envisaged under the new Common Fishery Policy may not be adequate for Mediterranean cephalopod stocks. (C) 2017 Elsevier Ltd. All rights reserved.  
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  Volume de collection (down) Numéro de collection Edition  
  ISSN 0079-6611 ISBN Médium  
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  Numéro d'Appel MARBEC @ alain.herve @ collection 2132  
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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 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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