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Auteur Javidpour, J.; Molinero, J.-C.; Ramirez-Romero, E.; Roberts, P.; Larsen, T. doi  openurl
  Titre (up) Cannibalism makes invasive comb jelly, Mnemiopsis leidyi, resilient to unfavourable conditions Type Article scientifique
  Année 2020 Publication Revue Abrégée Commun. Biol.  
  Volume 3 Numéro 1 Pages  
  Mots-Clés black-sea; ctenophore mnemiopsis; evolution; growth; impact; kiel fjord; mechanisms; population-dynamics; predation; rates  
  Résumé The proliferation of invasive marine species is often explained by a lack of predators and opportunistic life history traits. For the invasive comb jelly Mnemiopsis leidyi, it has remained unclear how this now widely distributed species is able to overcome long periods of low food availability, particularly in their northernmost exotic habitats in Eurasia. Based on both field and laboratory evidence, we show that adult comb jellies in the western Baltic Sea continue building up their nutrient reserves after emptying the prey field through a shift to cannibalizing their own larvae. We argue, that by creating massive late summer blooms, the population can efficiently empty the prey field, outcompete intraguild competitors, and use the bloom events to build nutrient reserves for critical periods of prey scarcity. Our finding that cannibalism makes a species with typical opportunistic traits more resilient to environmental fluctuations is important for devising more effective conservation strategies. Javidpour et al. use high-frequency field data, geochemical-isotopic analysis, and modeling of prey-predator dynamics of the comb jelly in the western Baltic Sea to show that adult comb jellies cannibalize their own larvae. This shift to cannibalism allows adults to build nutrient reserves for periods of prey scarcity and sheds light on the ability of this invasive species to thrive amidst environmental fluctuations.  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2788  
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Auteur Queiros, Q.; Fromentin, J.-M.; Astruc, G.; Bauer, R.K.; Saraux, C. doi  openurl
  Titre (up) Dolphin predation pressure on pelagic and demersal fish in the northwestern Mediterranean Sea Type Article scientifique
  Année 2018 Publication Revue Abrégée Mar. Ecol.-Prog. Ser.  
  Volume 603 Numéro Pages 13-27  
  Mots-Clés Anchovy; artisanal fisheries; bottle-nosed dolphins; Bottlenose dolphin; cetaceans reveals; delphinus-delphis; European hake; Gulf of Lions; longline fisheries; marine ecosystem; Predation pressure; Sardine; stenella-coeruleoalba; Striped dolphin; striped-dolphin; Top-down effect; trophic cascades; tursiops-truncatus  
  Résumé Sardine Sardina pilchardus, anchovy Engraulis encrasicolus and European hake Merluccius merluccius represent a significant part of the commercial landings in the Gulf of Lions (northwestern Mediterranean Sea). However, their stocks have shown severe declines during the last decades due to fishing pressure and/or environmental changes. The aim of this study was to estimate the current predation pressure of bottlenose dolphins Tursiops truncatus and striped dolphins Stenella coeruleoalba – which are abundant in the area-on sardine, anchovy and hake. To do so, we developed an original approach based on several data sets and models (aerial surveys, stomach contents, allometric and stock assessment models) and Monte Carlo simulations to incorporate various sources of uncertainty due to data limitations. Despite the uncertainties, the results showed that dolphin predation pressure on sardine and anchovy was extremely low in the Gulf of Lions (all simulations <0.5 % of the available stock), indicating little impact of dolphins on those populations. However, significant predation pressure on hake (median value: 23 %) was detected, a value which might have doubled in the last 30 yr because of hake overfishing. Overexploitation has thus reinforced the natural mortality of hake due to dolphin predation, but this predation pressure remains 2 to 3 times lower than that exerted by fisheries.  
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  ISSN 0171-8630 ISBN Médium  
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  Numéro d'Appel MARBEC @ alain.herve @ collection 2429  
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Auteur Maury, O.; Poggiale, J.-C. url  openurl
  Titre (up) From individuals to populations to communities: A dynamic energy budget model of marine ecosystem size-spectrum including life history diversity Type Article scientifique
  Année 2013 Publication Revue Abrégée Journal of Theoretical Biology  
  Volume 324 Numéro Pages 52-71  
  Mots-Clés biodiversity; Dynamic Energy Budget theory; predation; Schooling; Size spectrum  
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  ISSN 0022-5193 ISBN Médium  
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  Notes <p>\textbackslashtextlessp\textbackslashtextgreaterIndividual metabolism, predator–prey relationships, and the role of biodiversity are major factors underlying the dynamics of food webs and their response to environmental variability. Despite their crucial, complementary and interacting influences, they are usually not considered simultaneously in current marine ecosystem models. In an attempt to fill this gap and determine if these factors and their interaction are sufficient to allow realistic community structure and dynamics to emerge, we formulate a mathematical model of the size-structured dynamics of marine communities which integrates mechanistically individual, population and community levels. The model represents the transfer of energy generated in both time and size by an infinite number of interacting fish species spanning from very small to very large species. It is based on standard individual level assumptions of the Dynamic Energy Budget theory (DEB) as well as important ecological processes such as opportunistic size-based predation and competition for food. Resting on the inter-specific body-size scaling relationships of the DEB theory, the diversity of life-history traits (i.e. biodiversity) is explicitly integrated. The stationary solutions of the model as well as the transient solutions arising when environmental signals (e.g. variability of primary production and temperature) propagate through the ecosystem are studied using numerical simulations. It is shown that in the absence of density-dependent feedback processes, the model exhibits unstable oscillations. Density-dependent schooling probability and schooling-dependent predatory and disease mortalities are proposed to be important stabilizing factors allowing stationary solutions to be reached. At the community level, the shape and slope of the obtained quasi-linear stationary spectrum matches well with empirical studies. When oscillations of primary production are simulated, the model predicts that the variability propagates along the spectrum in a given frequency-dependent size range before decreasing for larger sizes. At the species level, the simulations show that small and large species dominate the community successively (small species being more abundant at small sizes and large species being more abundant at large sizes) and that the total biomass of a species decreases with its maximal size which again corroborates empirical studies. Our results indicate that the simultaneous consideration of individual growth and reproduction, size-structured trophic interactions, the diversity of life-history traits and a density-dependent stabilizing process allow realistic community structure and dynamics to emerge without any arbitrary prescription. As a logical consequence of our model construction and a basis for future studies, we define the function Φ as the relative contribution of each species to the total biomass of the ecosystem, for any given size. We argue that this function is a measure of the functional role of biodiversity characterizing the impact of the structure of the community (its species composition) on its function (the relative proportions of losses, dissipation and biological work).\textbackslashtextless/p\textbackslashtextgreater</p> Approuvé pas de  
  Numéro d'Appel LL @ pixluser @ collection 245  
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Auteur Krause, J.; Herbert-Read, J.E.; Seebacher, F.; Domenici, P.; Wilson, A.D.M.; Marras, S.; Svendsen, M.B.S.; Strombom, D.; Steffensen, J.F.; Krause, S.; Viblanc, P.E.; Couillaud, P.; Bach, P.; Sabarros, P.S.; Zaslansky, P.; Kurvers, R.H.J.M. doi  openurl
  Titre (up) Injury-mediated decrease in locomotor performance increases predation risk in schooling fish Type Article scientifique
  Année 2017 Publication Revue Abrégée Philos. Trans. R. Soc. B-Biol. Sci.  
  Volume 372 Numéro 1727 Pages 20160232  
  Mots-Clés animal groups; Behavior; danger; fish schools; geometry; group-living; killer whales; locomotion; organization; Predation; prey interactions; selfish herd; spatial position; spatial positions; vertebrates  
  Résumé The costs and benefits of group living often depend on the spatial position of individuals within groups and the ability of individuals to occupy preferred positions. For example, models of predation events for moving prey groups predict higher mortality risk for individuals at the periphery and front of groups. We investigated these predictions in sardine (Sardinella aurita) schools under attack from group hunting sailfish (Istiophorus platypterus) in the open ocean. Sailfish approached sardine schools about equally often from the front and rear, but prior to attack there was a chasing period in which sardines attempted to swim away from the predator. Consequently, all sailfish attacks were directed at the rear and peripheral positions of the school, resulting in higher predation risk for individuals at these positions. During attacks, sailfish slash at sardines with their bill causing prey injury including scale removal and tissue damage. Sardines injured in previous attacks were more often found in the rear half of the school than in the front half. Moreover, injured fish had lower tail-beat frequencies and lagged behind uninjured fish. Injuries inflicted by sailfish bills may, therefore, hinder prey swimming speed and drive spatial sorting in prey schools through passive self-assortment. We found only partial support for the theoretical predictions from current predator-prey models, highlighting the importance of incorporating more realistic predator-prey dynamics into these models. This article is part of the themed issue 'Physiological determinants of social behaviour in animals'.  
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  ISSN 0962-8436 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2161  
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Auteur Chassot, E.; Rouyer, T.; Trenkel, V.M.; Gascuel, D. url  doi
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  Titre (up) Investigating trophic-level variability in Celtic Sea fish predators Type Article scientifique
  Année 2008 Publication Revue Abrégée Journal of Fish Biology  
  Volume 73 Numéro 4 Pages 763-781  
  Mots-Clés food web; Gam; Indicator; omnivory; Predation; Trophic level  
  Résumé The trophic level (TL) mean and variance, and the degree of omnivory for five Celtic Sea fish predators were estimated using a database of stomach content records characterized by a high level of taxonomic resolution. The predators occupied a high position in the food web, i.e. 4·75 for Atlantic cod Gadus morhua, 4·44 for haddock Melanogrammus aeglefinus, 4·88 for European hake Merluccius merluccius, 5·00 for megrim Lepidorhombus whiffiagonis and 5·27 for whiting Merlangius merlangus. The level of taxonomic resolution of the prey did not greatly affect mean TL predator values; an effect on variance was evident, low resolution masking intra-population variability in TL. Generalized additive models (GAM) were used to explain the variability of predator TL caused by environmental variables (International Council for the Exploration of the Sea, ICES, division and season) and predator characteristics (total length, LT). Significant year, location season and interaction effects were found for some species and with LT at the scale of ICES subdivision. The species-specific variability of TL could be due to spatio-temporal variations in prey availability and in predator selectivity following ontogenetic changes. Omnivorous fish TL was less affected by spatio-temporal variations. In addition, results showed that the omnivory index and TL variability provide dissimilar information on predator feeding strategy. Combining information on TL variability and omnivory allowed between within-individual and between-individual components contributing to trophic niche width to be separated and the type of generalization of fish predators to be identified.  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1674  
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