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Auteur Matich, P.; Kiszka, J.J.; Heithaus, M.R.; Le Bourg, B.; Mourier, J. doi  openurl
  Titre Inter-individual differences in ontogenetic trophic shifts among three marine predators Type Article scientifique
  Année 2019 Publication Revue Abrégée Oecologia  
  Volume (down) 189 Numéro 3 Pages 621-636  
  Mots-Clés body-size; bull shark; carcharhinus-leucas; delta-n-15 values; Dietary shifts; Elasmobranchs; Foraging development; individual variation; intertissue comparisons; Juveniles; life-history traits; niche shifts; Nursery; specialization; stable-isotopes  
  Résumé Ontogenetic niche shifts are widespread. However, individual differences in size at birth, morphology, sex, and personalities can cause variability in behavior. As such, inherent inter-individual differences within populations may lead to context-dependent changes in behavior with animal body size, which is of concern for understanding population dynamics and optimizing ecological monitoring. Using stable carbon and nitrogen isotope values from concurrently sampled tissues, we quantified the direction and magnitude of intraspecific variation in trophic shifts among three shark species, and how these changed with body size: spurdogs (Squalus spp.) in deep-sea habitats off La Reunion, bull sharks (Carcharhinus leucas) in estuarine habitats of the Florida Everglades, and blacktip reef sharks (Carcharhinus melanopterus) in coral reef ecosystems of Moorea, French Polynesia. Intraspecific variation in trophic shifts was limited among spurdogs, and decreased with body size, while bull sharks exhibited greater individual differences in trophic shifts, but also decreased in variability through ontogeny. In contrast, blacktip reef sharks exhibited increased intraspecific variation in trophic interactions with body size. Variability in trophic interactions and ontogenetic shifts are known to be associated with changes in energetic requirements, but can vary with ecological context. Our results suggest that environmental stability may affect variability within populations, and ecosystems with greater spatial and/or temporal variability in environmental conditions, and those with more diverse food webs may facilitate greater individual differences in trophic interactions, and thus ontogenetic trophic shifts. In light of concerns over environmental disturbance, elucidating the contexts that promote or dampen phenotypic variability is invaluable for predicting population- and community-level responses to environmental changes.  
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  ISSN 0029-8549 ISBN Médium  
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Auteur Lorin-Nebel, C.; Avarre, J.C.; Faivre, N.; Wallon, S.; Charmantier, G.; Durand, J.D. url  doi
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  Titre Osmoregulatory strategies in natural populations of the black-chinned tilapia Sarotherodon melanotheron exposed to extreme salinities in West African estuaries Type Article scientifique
  Année 2012 Publication Revue Abrégée J. Comp. Physiol. B-Biochem. Syst. Environ. Physiol.  
  Volume (down) 182 Numéro 6 Pages 771-780  
  Mots-Clés ATPase; Gills; Hypersalinity; Na+/ K+; Osmoregulation; Teleost; Tilapia; cichlidae; expression; fish; gambia; gill; life-history traits; pisces; saloum estuaries; water  
  Résumé The effect of salinity was studied in natural populations of the black-chinned tilapia (Sarotherodon melanotheron) from West Africa. This euryhaline species colonizes nearly all coastal environments from bays to lagoons characterized by salinities ranging from fresh water to hypersaline water over 100 aEuro degrees. Individuals were sampled during the dry season at several locations characterized by different levels of salinity (3-102 aEuro degrees). Their osmotic status and their gills were analyzed. The branchial mitochondria-rich cells (MRC), localized at the basis of the filaments and along the lamellae in fish taken from the saline stations, showed a wide plasticity with significant differences in their number and size. The most striking results were a significant larger area (a parts per thousand 3x) and a higher number (a parts per thousand 55x) of MRC at high salinity (102 aEuro degrees) compared to low salinity (3 aEuro degrees). The major ion transporters and channels were localized by immunocytochemistry and different expression patterns have been recorded between stations. Despite an increased Na+/K+-ATPase (NKA) alpha-subunit expression and NKA activity, pointing to an increased monovalent ion excretion, a severe osmotic imbalance was recorded in animals living in hypersaline environments.  
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  ISSN 0174-1578 ISBN Médium  
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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 (down) 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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  ISSN 0079-6611 ISBN Médium  
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Auteur Lucena-Fredou, F.; Kell, L.; Fredou, T.; Gaertner, D.; Potier, M.; Bach, P.; Travassos, P.; Hazin, F.; Menard, F. doi  openurl
  Titre Vulnerability of teleosts caught by the pelagic tuna longline fleets in South Atlantic and Western Indian Oceans Type Article scientifique
  Année 2017 Publication Revue Abrégée Deep-Sea Res. Part II-Top. Stud. Oceanogr.  
  Volume (down) 140 Numéro Pages 230-241  
  Mots-Clés Bycatch; climate-change; ecological risk-assessment; exploitation status; Fishery management; impact; life-history strategies; management; marine fishes; Productivity and Susceptibility Analysis; risk; Sustainability; trawl fishery  
  Résumé Productivity and Susceptibility Analysis (PSA) is a methodology for evaluating the vulnerability of a stock based on its biological productivity and susceptibility to fishing. In this study, we evaluated the vulnerability of 60 stocks of tuna, billfishes and other teleosts caught by the tuna longline fleets operating in the South Atlantic and Indian Ocean using a semi-quantitative PSA. We (a) evaluated the vulnerability of the species in the study areas; (b) compared the vulnerability of target and non-target species and oceans; (c) analyzed the sensitivity of data entry; and (d) compared the results of the PSA to other fully quantitative assessment methods. Istiophoridae exhibited the highest scores for vulnerability. The top 10 species at risk were: Atlantic Istiophorus albicans; Indian Ocean Istiompax indica; Atlantic Makaira nigricans and Thunnus alalunga; Indian Ocean Xiphias gladius; Atlantic T. albacares, Gempylus serpens, Ranzania laevis and X. gladius; and Indian Ocean T. alalunga. All species considered at high risk were targeted or were commercialized bycatch, except for the Atlantic G. serpens and R. laevis which.were discarded, and may be considered as a false positive. Those species and others at high risk should be prioritized for further assessment and/or data collection. Most species at moderate risk were bycatch species kept for sale. Conversely, species classified at low risk were mostly discarded. Overall, species at high risk were overfished and/or subjected to overfishing. Moreover, all species considered to be within extinction risk (Critically Endangered, Endangered and Vulnerable) were in the high risk category. The good concordance between approaches corroborates the results of our analysis. PSA is not a replacement for traditional stock assessments, where a stock is assessed at regular intervals to provide management advice. It is of importance, however, where there is uncertainty about catches and life history parameters, since it can identify species at risk, and where management action and data collection is required, e.g. for many species at high and most at moderate risk in the South Atlantic and Indian oceans.  
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  ISSN 0967-0645 ISBN Médium  
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Auteur Oikonomou, A.; Leprieur, F.; Leonardos, I.D. doi  openurl
  Titre Ecomorphological diversity of freshwater fishes as a tool for conservation priority setting: a case study from a Balkan hotspot Type Article scientifique
  Année 2018 Publication Revue Abrégée Environ. Biol. Fishes  
  Volume (down) 101 Numéro 7 Pages 1121-1136  
  Mots-Clés assemblages; Balkan peninsula; communities; Conservation; Ecomorphology; environmental-factors; Freshwater fishes; functional diversity; future challenges; habitat gradients; life-history strategies; Originality; species richness; stream; traits  
  Résumé Biodiversity studies commonly focus on taxonomic diversity measures such as species richness and abundance. However, alternative measures based on ecomorphological traits are also critical for unveiling the processes shaping biodiversity and community assembly along environmental gradients. Our study presents the first analysis of habitat-trait-community structure in a Balkan biodiversity hotspot (Louros river, NW Greece), through the investigation of the relationships among freshwater fish assemblages' composition, morphological traits and habitat features. In order to provide a hierarchical classification of species' priority to protection measures, we highlight the most ecomorphologically distinct species using originality analysis. Our results suggest that the longitudinal changes of habitat variables (water temperature, depth, substrate, altitude) drive the local fish assemblages' structure highlighting the upstream-downstream gradient. We also present evidence for environmental filtering, establishing fish assemblages according to their ecomorphological traits. The calculation of the seven available indices of ecomorphological originality indicates that Valencia letourneuxi and Cobitis hellenica, which are endemic to Louros and threatened with extinction, exhibited the highest distinctiveness; thus their protection is of great importance. The methodological approach followed and the patterns described herein can contribute further to the application of community ecology theory to conservation, highlighting the need to use ecomorphological traits as a useful 'tool'.  
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  ISSN 0378-1909 ISBN Médium  
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