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Auteur (down) Shannon, L.; Coll, M.; Bundy, A.; Gascuel, D.; Heymans, J.J.; Kleisner, K.; Lynam, C.P.; Piroddi, C.; Tam, J.; TraversTrolet, M.; Shin, Y.
Titre Trophic level-based indicators to track fishing impacts across marine ecosystems Type Article scientifique
Année 2014 Publication Revue Abrégée Mar Ecol Prog Ser
Volume 512 Numéro Pages 115-140
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Résumé ABSTRACT: Trophic level (TL)-based indicators have been widely used to examine fishing impacts in aquatic ecosystems and the induced biodiversity changes. However, much debate has ensued regarding discrepancies and challenges arising from the use of landings data from commercial fisheries to calculate TL indicators. Subsequent studies have started to examine survey-based and model-based indicators. In this paper, we undertake an extensive evaluation of a variety of TL indicators across 9 well-studied marine ecosystems by making use of model- as well as survey- and catch-based TL indicators. Using detailed regional information and data on fishing history, fishing intensity, and environmental conditions, we evaluate how well TL indicators are capturing fishing effects at the community level of marine ecosystems. Our results highlight that the differences observed between TL indicator values and trends is dependent on the data source and the TL cut-off point used in the calculations and is not attributable to an intrinsic problem with TL-based indicators. All 3 data sources provide useful information about the structural changes in the ecosystem as a result of fishing, but our results indicate that only model-based indicators represent fishing impacts at the whole ecosystem level.
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1206
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Auteur (down) Rouyer, T.; Fromentin, J.M.; Stenseth, N.C.; Cazelles, B.
Titre Analysing multiple time series and extending significance testing in wavelet analysis Type Article scientifique
Année 2008 Publication Revue Abrégée Mar Ecol Prog Ser
Volume 359 Numéro Pages 11-23
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Résumé ABSTRACT: In nature, non-stationarity is rather typical, but the number of statistical tools allowing for non-stationarity remains rather limited. Wavelet analysis is such a tool allowing for non-stationarity but the lack of an appropriate test for statistical inference as well as the difficulty to deal with multiple time series are 2 important shortcomings that limits its use in ecology. We present 2 approaches to deal with these shortcomings. First, we used 1/ƒβ models to test cycles in the wavelet spectrum against a null hypothesis that takes into account the highly autocorrelated nature of ecological time series. To illustrate the approach, we investigated the fluctuations in bluefin tuna trap catches with a set of different null models. The 1/ƒβ models approach proved to be the most consistent to discriminate significant cycles. Second, we used the maximum covariance analysis to compare, in a quantitative way, the time–frequency patterns (i.e. the wavelet spectra) of numerous time series. This approach built cluster trees that grouped the wavelet spectra according to their time–frequency patterns. Controlled signals and time series of sea surface temperature (SST) in the Mediterranean Sea were used to test the ability and power of this approach. The results were satisfactory and clusters on the SST time series displayed a hierarchical division of the Mediterranean into a few homogeneous areas that are known to display different hydrological and oceanic patterns. We discuss the limits and potentialities of these methods to study the associations between ecological and environmental fluctuations.
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1667
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Auteur (down) Robert, M.; Dagorn, L.; Filmalter, J.D.; Deneubourg, J.L.; Itano, D.; Holland, K.
Titre Intra-individual behavioral variability displayed by tuna at fish aggregating devices (FADs) Type Article scientifique
Année 2013 Publication Revue Abrégée Mar Ecol Prog Ser
Volume 484 Numéro Pages 239-247
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Résumé ABSTRACT: Fishers have exploited the associative behavior displayed by several pelagic fish species with floating objects for decades, through the use of man-made fish aggregating devices (FADs), which facilitate the capture of such species. However, our understanding of this associative behavior and its adaptive value is poor and the scientific community is ill-equipped to provide fishery managers with science-based recommendations on the impacts of FADs on ecosystems. In an array of 13 anchored FADs around Oahu, Hawaii, USA, 72 yellowfin tuna Thunnus albacares were equipped with internal acoustic tags, which facilitated the continuous monitored of their presence and absence around each FAD using automated acoustic receivers. Data were analyzed using survival curves with the objective of determining the behavioral dynamics of fish joining and leaving the FADs. Residence times at FADs were characterized by 4 behavioral modes: briefly passing near a FAD (average 13.1 min), short association (average 2.9 d), and 2 long association behaviors (13.8 and 23.2 d, respectively). Statistical analyses suggest that different behavioral modes were likely dependent upon local conditions around the FAD at a given time (environmental factors or social interactions). We observed 2 behavioral modes for absence times from FADs: short (2.8 d) and long (infinite). More importantly, individuals exhibited behavioral variability, switching between short and long residence times at FADs. This suggests that large pelagic fish can display a range of behavioral responses while in an array of FADs, challenging the common hypothesis of a single behavioral pattern, which could ultimately lead to an ecological trap. Survival curves were best fitted with exponential models, suggesting that underlying behavioral processes were time independent.
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Numéro d'Appel LL @ pixluser @ collection 262
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Auteur (down) Piroddi, C.; Coll, M.; Steenbeek, J.; Moy, D.M.; Christensen, V.
Titre Modelling the Mediterranean marine ecosystem as a whole: addressing the challenge of complexity Type Article scientifique
Année 2015 Publication Revue Abrégée Mar Ecol Prog Ser
Volume 533 Numéro Pages 47-65
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Résumé ABSTRACT: An ecosystem modelling approach was used to understand and assess the Mediterranean marine ecosystem structure and function as a whole. In particular, 2 food web models for the 1950s and 2000s were built to investigate: (1) the main structural and functional characteristics of the Mediterranean food web during these 2 time periods; (2) the key species/functional groups and interactions; (3) the role of fisheries and their impact; and (4) the ecosystem properties of the Mediterranean Sea in comparison with other European regional seas. Our results show that small pelagic fishes, mainly European pilchards and anchovies, prevailed in terms of biomasses and catches during both periods. Large pelagic fishes, sharks and medium pelagic fishes played a key role in the 1950s ecosystem, and have been replaced in more recent years by benthopelagic and benthic cephalopods. Fisheries showed large effects on most living groups of the ecosystem in both time periods. When comparing the Mediterranean results to those of other European regional seas modelling initiatives, the Mediterranean stood alone in relation to the type of flows (e.g. Mediterranean Sea, flow to detritus: 42%; other EU seas, consumption: 43-48%) driving the system and the cycling indices. This suggested higher levels of community stress induced by intensive fishing activities in the Mediterranean basin. This study constitutes the first attempt to build an historical and current food web model for the whole Mediterranean Sea.
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1414
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Auteur (down) Paredes, R.; Orben, R.A.; Roby, D.D.; Irons, D.B.; Young, R.; Renner, H.; Tremblay, Y.; Will, A.; Harding, A.M.A.; Kitaysky, A.S.
Titre Foraging ecology during nesting influences body size in a pursuit-diving seabird Type Article scientifique
Année 2015 Publication Revue Abrégée Mar Ecol Prog Ser
Volume 533 Numéro Pages 261-276
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Résumé ABSTRACT: Causes and consequences of differences in seabird foraging strategies between breeding colonies are not well understood. We tested whether body size of a pursuit-diving seabird, the thick-billed murre Uria lomvia, differs between breeding colonies and, if so, how size differences can be understood in the context of differences in foraging behavior, habitat use, and breeding performance. We measured adult murres over 3 seasons (2008 to 2010) at 2 of the Pribilof Islands, St. Paul and St. George, located on the continental shelf of the Bering Sea at different distances from the shelf break. Body mass and size were positively associated with deep diving and negatively associated with long flights, suggesting morphology influences foraging and commuting efficiency. Murres from St. Paul (farther from the shelf break) were larger than those from St. George (nearer the shelf break), foraged exclusively in the middle shelf domain, made deep dives during daylight, and fed on larger benthic prey. In contrast, smaller murres from St. George commuted greater distances to beyond the shelf break, made shallow dives at night, and fed on smaller, high-energy, schooling, vertical-migrating prey. Both foraging strategies resulted in similar chick-feeding rates and fledging success. The largest and the smallest murres experienced less stress during breeding compared to intermediate-sized murres, suggesting divergent selection for body size between islands. Nesting murres, as central-place foragers, may experience strong selection pressure on body size and other adaptive traits that reflect differences between breeding colonies in foraging ecology and the acquisition of resources for reproduction.
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1413
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