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Auteur (down) Sydeman, W.J.; Thompson, S.A.; Anker-Nilssen, T.; Arimitsu, M.; Bennison, A.; Bertrand, S.; Boersch-Supan, P.; Boyd, C.; Bransome, N.C.; Crawford, R.J.M.; Daunt, F.; Furness, R.W.; Gianuca, D.; Gladics, A.; Koehn, L.; Lang, J.W.; Logerwell, E.; Morris, T.L.; Phillips, E.M.; Provencher, J.; Punt, A.E.; Saraux, C.; Shannon, L.; Sherley, R.B.; Simeone, A.; Wanless, R.M.; Wanless, S.; Zador, S.
Titre Best practices for assessing forage fish fisheries-seabird resource competition Type Article scientifique
Année 2017 Publication Revue Abrégée Fisheries Research
Volume 194 Numéro Pages 209-221
Mots-Clés fisheries; Forage fish; Methodology; resource competition; Seabirds
Résumé Worldwide, in recent years capture fisheries targeting lower-trophic level forage fish and euphausiid crustaceans have been substantial (∼20 million metric tons [MT] annually). Landings of forage species are projected to increase in the future, and this harvest may affect marine ecosystems and predator-prey interactions by removal or redistribution of biomass central to pelagic food webs. In particular, fisheries targeting forage fish and euphausiids may be in competition with seabirds, likely the most sensitive of marine vertebrates given limitations in their foraging abilities (ambit and gape size) and high metabolic rate, for food resources. Lately, apparent competition between fisheries and seabirds has led to numerous high-profile conflicts over interpretations, as well as the approaches that could and should be used to assess the magnitude and consequences of fisheries-seabird resource competition. In this paper, we review the methods used to date to study fisheries competition with seabirds, and present “best practices” for future resource competition assessments. Documenting current fisheries competition with seabirds generally involves addressing two major issues: 1) are fisheries causing localized prey depletion that is sufficient to affect the birds? (i.e., are fisheries limiting food resources?), and 2) how are fisheries-induced changes to forage stocks affecting seabird populations given the associated functional or numerical response relationships? Previous studies have been hampered by mismatches in the scale of fisheries, fish, and seabird data, and a lack of causal understanding due to confounding by climatic and other ecosystem factors (e.g., removal of predatory fish). Best practices for fisheries-seabird competition research should include i) clear articulation of hypotheses, ii) data collection (or summation) of fisheries, fish, and seabirds on matched spatio-temporal scales, and iii) integration of observational and experimental (including numerical simulation) approaches to establish connections and causality between fisheries and seabirds. As no single technique can provide all the answers to this vexing issue, an integrated approach is most promising to obtain robust scientific results and in turn the sustainability of forage fish fisheries from an ecosystem perspective.
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ISSN 0165-7836 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2167
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Auteur (down) Saraux, C.; Van Beveren, E.; Brosset, P.; Queiros, Q.; Bourdeix, J.-H.; Dutto, G.; Gasset, E.; Jac, C.; Bonhommeau, S.; Fromentin, J.-M.
Titre Small pelagic fish dynamics: A review of mechanisms in the Gulf of Lions Type Article scientifique
Année 2019 Publication Revue Abrégée Deep-Sea Res. Part II-Top. Stud. Oceanogr.
Volume 159 Numéro Pages 52-61
Mots-Clés Population dynamics; Zooplankton; anchovy; fisheries; history; forage fish; nw mediterranean sea; el-nino; fluctuations; body condition; Bottom-up; Disease; Exploited species; Top-down; sardine sardinops-sagax; southern benguela
Résumé Around 2008, an ecosystem shift occurred in the Gulf of Lions, highlighted by considerable changes in biomass and fish mean weight of its two main small pelagic fish stocks (European anchovy, Engraulis encrasicolus; European sardine, Sardina pilchardus). Surprisingly these changes did not appear to be mediated by a decrease in fish recruitment rates (which remained high) or by a high fishing pressure (exploitation rates being extremely low). Here, we review the current knowledge on the population's dynamics and its potential causes. We used an integrative ecosystem approach exploring alternative hypotheses, ranging from bottom-up to top-down control, not forgetting epizootic diseases. First, the study of multiple population characteristics highlighted a decrease in body condition for both species as well as an important decrease in size resulting from both a slower growth and a progressive disappearance of older sardines. Interestingly, older sardines were more affected by the decrease in condition than younger ones, another sign of an unbalanced population structure. While top-down control by bluefin tuna or dolphins, emigration and disease were mostly discarded as important drivers, bottom-up control mediated by potential changes in the plankton community appeared to play an important role via a decrease in fish energy income and hence growth, condition and size. Isotopic and stomach content analyses indicated a dietary shift pre- and post-2008 and modeled mesozooplankton abundance was directly linked to fish condition. Despite low energy reserves from 2008 onwards, sardines and anchovies maintained if not increased their reproductive investment, likely altering the life-history trade-off between reproduction and survival and resulting in higher natural mortality. The current worrying situation might thus have resulted from changes in plankton availability/diversity, which remains to be thoroughly investigated together with fish phenotypic plasticity.
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Editeur Lieu de Publication Éditeur
Langue English Langue du Résumé Titre Original
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Volume de collection Numéro de collection Edition
ISSN 0967-0645 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2526
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Auteur (down) Pikitch, E.K.; Rountos, K.J.; Essington, T.E.; Santora, C.; Pauly, D.; Watson, R.; Sumaila, U.R.; Boersma, P.D.; Boyd, I.L.; Conover, D.O.; Cury, P.; Heppell, S.S.; Houde, E.D.; Mangel, M.; Plaganyi, E.; Sainsbury, K.; Steneck, R.S.; Geers, T.M.; Gownaris, N.; Munch, S.B.
Titre The global contribution of forage fish to marine fisheries and ecosystems Type Article scientifique
Année 2014 Publication Revue Abrégée Fish and Fisheries
Volume 15 Numéro 1 Pages 43-64
Mots-Clés ecosystem-based management; Ecosystem service; fish; fisheries value; forage; supportive values; trade-offs
Résumé Forage fish play a pivotal role in marine ecosystems and economies worldwide by sustaining many predators and fisheries directly and indirectly. We estimate global forage fish contributions to marine ecosystems through a synthesis of 72 published Ecopath models from around the world. Three distinct contributions of forage fish were examined: (i) the ecological support service of forage fish to predators in marine ecosystems, (ii) the total catch and value of forage fisheries and (iii) the support service of forage fish to the catch and value of other commercially targeted predators. Forage fish use and value varied and exhibited patterns across latitudes and ecosystem types. Forage fish supported many kinds of predators, including fish, seabirds, marine mammals and squid. Overall, forage fish contribute a total of about 16.9 billion USD to global fisheries values annually, i.e. 20% of the global ex-vessel catch values of all marine fisheries combined. While the global catch value of forage fisheries was 5.6 billion, fisheries supported by forage fish were more than twice as valuable (11.3 billion). These estimates provide important information for evaluating the trade-offs of various uses of forage fish across ecosystem types, latitudes and globally. We did not estimate a monetary value for supportive contributions of forage fish to recreational fisheries or to uses unrelated to fisheries, and thus the estimates of economic value reported herein understate the global value of forage fishes.
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ISSN 1467-2960 ISBN Médium
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Numéro d'Appel LL @ pixluser @ collection 332
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Auteur (down) Boyd, C.; Grunbaum, D.; Hunt, G.L.; Punt, A.E.; Weimerskirch, H.; Bertrand, S.
Titre Effectiveness of social information used by seabirds searching for unpredictable and ephemeral prey Type Article scientifique
Année 2016 Publication Revue Abrégée Behav. Ecol.
Volume 27 Numéro 4 Pages 1223-1234
Mots-Clés agent-based model; albatrosses; antarctic krill; central place foragers; colonies; evolution; foraging model; gannets; Habitat selection; insights; local enhancement; local enhancement; models; public information; search strategies
Résumé Understanding how seabirds and other central place foragers locate food resources represents a key step in predicting responses to changes in resource abundance and distribution. Where prey distributions are unpredictable and ephemeral, seabirds may gain up-to-date information by monitoring the direction of birds returning to the colony or by monitoring the foraging behavior of other birds through local enhancement. However, search strategies based on social information may require high population densities, raising concerns about the potential loss of information in declining populations. Our objectives were to explore the mechanisms that underpin effective search strategies based on social information under a range of population densities and different foraging conditions. Testing relevant hypotheses through field observation is challenging because of limitations in the ability to manipulate population densities and foraging conditions. We therefore developed a spatially explicit individual-based foraging model, informed by data on the movement and foraging patterns of seabirds foraging on pelagic prey, and used model simulations to investigate the mechanisms underpinning search strategies. Orientation of outbound headings in line with returning birds enables departing birds to avoid areas without prey even at relatively low population densities. The mechanisms underpinning local enhancement are more effective as population densities increase and may be facilitated by other mechanisms that concentrate individuals in profitable areas. For seabirds and other central place foragers foraging on unpredictable and ephemeral food resources, information is especially valuable when resources are spatially concentrated and may play an important role in mitigating poor foraging conditions.
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Langue English Langue du Résumé Titre Original
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Volume de collection Numéro de collection Edition
ISSN 1045-2249 ISBN Médium
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Notes Approuvé pas de
Numéro d'Appel MARBEC @ alain.herve @ collection 2068
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Auteur (down) Boyd, C.; Castillo, R.; Hunt, G.L.; Punt, A.E.; VanBlaricom, G.R.; Weimerskirch, H.; Bertrand, S.
Titre Predictive modelling of habitat selection by marine predators with respect to the abundance and depth distribution of pelagic prey Type Article scientifique
Année 2015 Publication Revue Abrégée J Anim Ecol
Volume 84 Numéro 6 Pages 1575-1588
Mots-Clés central place foragers; Foraging ecology; habitat use; Humboldt Current system; predator–prey interactions; spatial distribution
Résumé * Understanding the ecological processes that underpin species distribution patterns is a fundamental goal in spatial ecology. However, developing predictive models of habitat use is challenging for species that forage in marine environments, as both predators and prey are often highly mobile and difficult to monitor. Consequently, few studies have developed resource selection functions for marine predators based directly on the abundance and distribution of their prey. * We analysed contemporaneous data on the diving locations of two seabird species, the shallow-diving Peruvian Booby (Sula variegata) and deeper diving Guanay Cormorant (Phalacrocorax bougainvilliorum), and the abundance and depth distribution of their main prey, Peruvian anchoveta (Engraulis ringens). Based on this unique data set, we developed resource selection functions to test the hypothesis that the probability of seabird diving behaviour at a given location is a function of the relative abundance of prey in the upper water column. * For both species, we show that the probability of diving behaviour is mostly explained by the distribution of prey at shallow depths. While the probability of diving behaviour increases sharply with prey abundance at relatively low levels of abundance, support for including abundance in addition to the depth distribution of prey is weak, suggesting that prey abundance was not a major factor determining the location of diving behaviour during the study period. * The study thus highlights the importance of the depth distribution of prey for two species of seabird with different diving capabilities. The results complement previous research that points towards the importance of oceanographic processes that enhance the accessibility of prey to seabirds. The implications are that locations where prey is predictably found at accessible depths may be more important for surface foragers, such as seabirds, than locations where prey is predictably abundant. * Analysis of the relative importance of abundance and accessibility is essential for the design and evaluation of effective management responses to reduced prey availability for seabirds and other top predators in marine systems.
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Langue en Langue du Résumé Titre Original
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Volume de collection Numéro de collection Edition
ISSN 1365-2656 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1349
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