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Auteur (up) Barria, C.; Coll, M.; Navarro, J.
Titre Unravelling the ecological role and trophic relationships of uncommon and threatened elasmobranchs in the western Mediterranean Sea Type Article scientifique
Année 2015 Publication Revue Abrégée Mar Ecol Prog Ser
Volume 539 Numéro Pages 225-240
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Résumé ABSTRACT: Deficiencies in basic ecological information on uncommon and endangered elasmobranch fishes impair the assessment of their ecological role in marine ecosystems. In this study, we examined the feeding ecology (diet composition and trophic level) and trophic relationships of 22 elasmobranchs (2 Carcharhiniformes, 1 Hexanchiformes, 1 Lamniformes, 3 Myliobatiformes, 6 Rajiformes, 6 Squaliformes and 3 Torpediniformes) present in the western Mediterranean Sea. To obtain a comprehensive view of the feeding ecology of these species, we combined different approaches: stable isotope analyses (δ13C and δ15N values), stomach content analyses and published sources. Our results revealed differences in feeding strategies among elasmobranch groups: skates (Rajiformes) mainly consume crustaceans; sharks (Carcharhiniformes, Hexanchiformes, Squaliformes and Lamniformes) prefer mixed diets composed of cephalopods, crustaceans and fishes; electric rays (Torpediniformes) feed mostly on fishes; and the diet of stingrays (Myliobatiformes) varies between species. Sharks and electric rays show higher trophic positions than skates, and the former occupy similar positions to other apex predators. Skates are more similar to other mesopredator fishes. These new findings offer essential information on the ecological role of several elasmobranchs in the western Mediterranean Sea and provide useful data for managers for future conservation strategies.
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1485
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Auteur (up) Bauer, R.K.; Bonhommeau, S.; Brisset, B.; Fromentin, J.-M.
Titre Aerial surveys to monitor bluefin tuna abundance and track efficiency of management measures Type Article scientifique
Année 2015 Publication Revue Abrégée Mar Ecol Prog Ser
Volume 534 Numéro Pages 221-234
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Résumé ABSTRACT: Conservation and management measures for exploited fish species rely on our ability to monitor variations in population abundance. In the case of the eastern stock of Atlantic bluefin tuna (ABFT), recent changes in management policies have strongly affected the reliability of fishery-dependent indicators due to drastic changes in fishing season/area, fisheries selectivity and strategy. However, fishery-independent indices of abundance are rare for large pelagic fish, and obtaining them is often costly and labor intensive. Here, we show that scientific aerial surveys are an appropriate tool for monitoring juvenile bluefin tuna abundance in the Mediterranean. We present an abundance index based on 62 aerial surveys conducted since 2000, using 2 statistical approaches to deal with the sampling strategy: line and strip transects. Both approaches showed a significant increase in juvenile ABFT abundance in recent years, resulting from the recovery plan established in 2007. Nonetheless, the estimates from the line transect method appear to be more robust and stable. This study provides essential information for fisheries management. Expanding the spatial coverage to other nursery grounds would further increase the reliability and representativeness of this index.
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Numéro d'Appel MARBEC @ alain.herve @ collection 1474
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Auteur (up) Bouchoucha, M.; Darnaude, A.M.; Gudefin, A.; Neveu, R.; VerdoitJarraya, M.; Boissery, P.; Lenfant, P.
Titre Potential use of marinas as nursery grounds by rocky fishes: insights from four Diplodus species in the Mediterranean Type Article scientifique
Année 2016 Publication Revue Abrégée Mar Ecol Prog Ser
Volume 547 Numéro Pages 193-209
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Résumé ABSTRACT: The construction of marinas along the shoreline has caused substantial habitat destruction within the sheltered coastal areas previously used as nursery grounds by many fish species. However, although the negative ecological impacts of these constructions have been reported extensively, their potential roles in the functioning of the coastal zone remain largely unknown. Here, we surveyed the juveniles of 4 Diplodus species in 5 marinas located along the French Mediterranean coast to assess whether rocky fishes can successfully settle inside these artificialized coastal areas. Inter-specific differences in the spatiotemporal use of the various artificial habitats provided by marinas were investigated between April and August over 2 consecutive years. We also tested the potential benefit of pegging additional artificial habitats (Biohuts) on docks and pontoons to increase their value as fish nursery grounds. Our results suggest that although variations in marina and artificial habitat preferences exist between species, Diplodus juveniles repeatedly colonize marinas. Their average abundances on added Biohut habitats were twice as high as on nearby bare surfaces. This suggests that increasing the complexity of the vertical structures of marinas can considerably enhance their suitability for juvenile rocky fishes, especially at the youngest stages, when mortality is highest. Therefore, as long as marina water quality is well controlled, ecological engineering within these man-made habitats might reduce the ecological consequences of urban development by providing suitable alternative artificial nursery grounds for rocky fishes.
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1545
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Auteur (up) Christensen, V.; Coll, M.; Piroddi, C.; Steenbeek, J.; Buszowski, J.; Pauly, D.
Titre A century of fish biomass decline in the ocean Type Article scientifique
Année 2014 Publication Revue Abrégée Mar Ecol Prog Ser
Volume 512 Numéro Pages 155-166
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Résumé ABSTRACT: We performed a global assessment of how fish biomass has changed over the last 100 yr, applying a previously developed methodology using ecological modeling. Our assessment built on more than 200 food web models representing marine ecosystems throughout the world covering the period from 1880 to 2007. All models were constructed based on the same approach, and have been previously documented. We spatially and temporally distributed fish biomasses delivered by these models based on fish habitat preferences, ecology, and feeding conditions. From these distributions, we extracted over 68000 estimates of biomass (for predatory and prey fishes separately, including trophic level of 3.5 or higher, and trophic level between 2.0 and 3.0, respectively), and predicted spatial-temporal trends in fish biomass using multiple regression. Our results predicted that the biomass of predatory fish in the world oceans has declined by two-thirds over the last 100 yr. This decline is accelerating, with 54% occurring in the last 40 yr. Results also showed that the biomass of prey fish has increased over the last 100 yr, likely as a consequence of predation release. These findings allowed us to predict that there will be fish in the future ocean, but the composition of fish assemblages will be very different from current ones, with small prey fish dominating. Our results show that the trophic structure of marine ecosystems has changed at a global scale, in a manner consistent with fishing down marine food webs.
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Numéro d'Appel LL @ pixluser @ collection 379
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Auteur (up) Duarte, L.; Rossi, F.; Docal, C.; Viejo, R.M.
Titre Effects of alga Fucus serratus decline on benthic assemblages and trophic linkages at its retreating southern range edge Type Article scientifique
Année 2015 Publication Revue Abrégée Mar Ecol Prog Ser
Volume 527 Numéro Pages 87-103
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Résumé ABSTRACT: Canopy-forming seaweeds are important coastal ecosystem engineers that sustain diverse multi-trophic assemblages. Their losses, with the subsequent reduction in habitat complexity, have been documented across many parts of the world and are often attributed to climate change and other anthropogenic factors. The general aim of the present study was to understand the repercussions of the decline of the canopy-forming alga Fucus serratus L. at its retreating southern range edge in the diversity and food-web linkages of intertidal assemblages. Few studies have attempted to document changes in benthic food webs following canopy loss. We examined the differences among southern locations situated at different distances from the range margin: those at the very edge, where F. serratus experienced a dramatic decline during recent years (marginal locations), and those where F. serratus is still dominant (central locations). Comparisons were made among locations situated at the same latitude and sharing a recent history of F. serratus dominance. Trophic relationships were analyzed using natural abundances of carbon and nitrogen stable isotopes. We report clear changes in the structure of benthic assemblages and lower trophic positioning of some consumers, suggesting an overall shrinkage of the food web length at the contracting range edge of F. serratus, which will transfer to higher trophic levels. Under present and future climatic scenarios, shifts in the distribution of coastal ecosystem engineers could entail a reorganization of local natural assemblages and food webs. More attention should be given to measure how much these shifts can modify the whole coastal food webs and their functioning.
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Numéro d'Appel MARBEC @ alain.herve @ collection 1340
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