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Auteur Queiros, Q.; Fromentin, J.-M.; Astruc, G.; Bauer, R.K.; Saraux, C. doi  openurl
  Titre 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 (down) 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 Chassot, E.; Duplisea, D.; Hammill, M.; Caskenette, A.; Bousquet, N.; Lambert, Y.; Stenson, G. url  doi
openurl 
  Titre Role of predation by harp seals Pagophilus groenlandicus in the collapse and non-recovery of northern Gulf of St. Lawrence cod Gadus morhua Type Article scientifique
  Année 2009 Publication Revue Abrégée Mar. Ecol.-Prog. Ser.  
  Volume (down) 379 Numéro Pages 279-297  
  Mots-Clés cod; functional response; harp seal; model; predation; recovery  
  Résumé A statistical catch-at-age model was developed to assess the effects of predation by the northwest Atlantic harp seal population on northern Gulf of St. Lawrence cod by estimating the relative importance of different sources of mortality that affected the stock during a period of collapse and non-recovery. Cod recruitment at age 1 is modeled via a non-linear stock-recruitment relationship based on total egg production and accounts for changes in female length-at-maturity and cod condition. Natural mortality other than seal predation also depends on cod condition used as an integrative index of changes in environmental conditions. The linkage between seals and cod is modeled through a multi-age functional response that was derived from the reconstruction of the seal diet using morphometric relationships and stomach contents of more than 200 seals collected between 1998 and 2001. The model was fitted following a maximum likelihood estimation approach to a scientific survey abundance index (1984 to 2006). Model results show that the collapse of the northern Gulf of St. Lawrence cod stock was mainly due to the combination of high fishing mortality rates and poor environmental conditions in the early to mid-1990s contributing to the current state of recruitment overfishing. The increase in harp seal abundance during 1984 to 2006 was reflected by an increase in predation mortality for the young cod age-groups targeted by seals. Although current levels of predation mortality affect cod spawning biomass, the lack of recovery of the NGSL cod stock seems mainly due to the very poor recruitment.  
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  ISSN 0171-8630 ISBN Médium  
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  Numéro d'Appel LL @ pixluser @ collection 15  
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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 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 (down) 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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  Volume de collection Numéro de collection Edition  
  ISSN 0962-8436 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2161  
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Auteur Maury, O.; Poggiale, J.-C. url  openurl
  Titre 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 (down) 324 Numéro Pages 52-71  
  Mots-Clés biodiversity; Dynamic Energy Budget theory; predation; Schooling; Size spectrum  
  Résumé  
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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 Travers, M.; Shin, Y.-J.; Jennings, S.; Machu, E.; Huggett, J.A.; Field, J.G.; Cury, P. url  doi
openurl 
  Titre Two-way coupling versus one-way forcing of plankton and fish models to predict ecosystem changes in the Benguela Type Article scientifique
  Année 2009 Publication Revue Abrégée Ecological Modelling  
  Volume (down) 220 Numéro 21 Pages 3089-3099  
  Mots-Clés Benguela upwelling; Ecem 07; End-to-end approach; food web; marine; Marine ecosystem model coupling; Predation  
  Résumé 'End-to-end' models have been adopted in an attempt to capture more of the processes that influence the ecology of marine ecosystems and to make system wide predictions of the effects of fishing and climate change. Here, we develop an end-to-end model by coupling existing models that describe the dynamics of low (ROMS-N(2)P(2)Z(2)D(2)) and high trophic levels(OSMOSE). ROMS-N(2)P(2)Z(2)D(2) is a biogeochemical model representing phytoplankton and zooplankton seasonal dynamics forced by hydrodynamics in the Benguela upwelling ecosystem. OSMOSE is an individual-based model representing the dynamics of several species of fish, linked through opportunistic and size-based trophic interactions. The models are coupled through a two-way size-based predation process. Plankton provides prey for fish, and the effects of predation by fish on the plankton are described by a plankton mortality term that is variable in space and time. Using the end-to-end model, we compare the effects of two-way coupling versus one-way forcing of the fish model with the plankton biomass field. The fish-induced mortality on plankton is temporally variable, in part explained by seasonal changes in fish biomass. Inclusion of two-way feedback affects the seasonal dynamics of plankton groups and usually reduces the amplitude of variation in abundance (top-down effect). Forcing and coupling lead to different predicted food web structures owing to changes in the dominant food chain which is supported by plankton (bottom-up effect). Our comparisons of one-way forcing and two-way coupling show how feedbacks may affect abundance, food web structure and food web function and emphasise the need to critically examine the consequences of different model architectures when seeking to predict the effects of fishing and climate change.  
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  ISSN 0304-3800 ISBN Médium  
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  Numéro d'Appel LL @ pixluser @ collection 29  
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