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Auteur CORMON, X.; LOOTS, C.; VAZ, S.; VERMARD, Y.; MARCHAL, P.
Titre Spatial interactions between saithe (Pollachius virens) and hake (Merluccius merluccius) in the North Sea Type Article scientifique
Année 2014 Publication Revue Abrégée Ices Journal Of Marine Science
Volume (down) 71 Numéro 6 Pages 1342-1355
Mots-Clés biotic interactions; competition; Generalized linear models; Hake; North sea; overlap; predator-prey relationship; saithe; species distribution modelling
Résumé Spatial interactions between saithe (Pollachius virens) and hake (Merluccius merluccius) were investigated in the North Sea. Saithe is a well-established species in the North Sea, while occurrence of the less common hake has recently increased in the area. Spatial dynamics of these two species and their potential spatial interactions were explored using binomial generalized linear models (GLM) applied to the International Bottom Trawl Survey (IBTS) data from 1991 to 2012. Models included different types of variables: (i) abiotic variables including sediment types, temperature, and bathymetry; (ii) biotic variables including potential competitors and potential preys presence; and (iii) spatial variables. The models were reduced and used to predict and map probable habitats of saithe, hake but also, for the first time in the North Sea, the distribution of the spatial overlap between these two species. Changes in distribution patterns of these two species and of their overlap were also investigated by comparing species' presence and overlap probabilities predicted over an early (1991–1996) and a late period (2007–2012). The results show an increase in the probability over time of the overlap between saithe and hake along with an expansion towards the southwest and Scottish waters. These shifts follow trends observed in temperature data and might be indirectly induced by climate changes. Saithe, hake, and their overlap are positively influenced by potential preys and/or competitors, which confirms spatial co-occurrence of the species concerned and leads to the questions of predator–prey relationships and competition. Finally, the present study provides robust predictions concerning the spatial distribution of saithe, hake, and of their overlap in the North Sea, which may be of interest for fishery managers.
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ISSN 1054-3139 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1135
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Auteur Poisson, F.; Filmalter, J.D.; Vernet, A.L.; Dagorn, L.
Titre Mortality rate of silky sharks (Carcharhinus falciformis) caught in the tropical tuna purse seine fishery in the Indian Ocean Type Article scientifique
Année 2014 Publication Revue Abrégée Canadian Journal of Fisheries and Aquatic Sciences
Volume (down) 71 Numéro 6 Pages 795-798
Mots-Clés
Résumé Scientists aboard French purse seine vessels recorded the number and condition of silky sharks (Carcharhinus falciformis) caught during three fishing cruises in the Indian Ocean. A sample of 31 individuals that showed signs of life were tagged with satellite tags to investigate their postrelease mortality. The majority of individuals (95%) were brought on board using the brailer. Combining the proportion of sharks that were dead (72%) and the mortality rate of those released (48%), the overall mortality rate of brailed individuals was 85%. Few individuals (5%) were not brailed as they were entangled and landed during the hauling process. The survival rate of these individuals was high, with an overall mortality rate of meshed individuals of 18%. The combination of these two categories led to an overall mortality rate of 81%. This high value reflects the harsh conditions encountered by sharks during the purse seine fishing process. Consequently, methods that prevent sharks being brought on board are a priority for future investigations, but good handling practices should also be promoted as they could reduce mortality by at least 19%.
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Auteur BAUER, R.; Graewe, U.; Stepputtis, D.; Zimmermann, C.; Hammer, C.
Titre Identifying the location and importance of spawning sites of Western Baltic herring using a particle backtracking model Type Article scientifique
Année 2014 Publication Revue Abrégée Ices Journal Of Marine Science
Volume (down) 71 Numéro 3 Pages 499-509
Mots-Clés backtracking; Baltic Sea; Clupea harengus; hatching sites; lagoon; larval transport; spring spawning
Résumé The recruitment success of some herring stocks fluctuates strongly, and apparently, success is often already determined during the early life stages, i.e. before metamorphosis. In studying the survival of early life stages and its affecting factors, particularly those during the egg stage, it is crucial to examine the processes at the spawning sites, which often cannot be explored directly. A recent decline in the recruitment of Western Baltic spring-spawning herring (WBSSH) increases the urgency of filling the knowledge gap for this stock, especially because one bottleneck in the recruitment seems to occur before hatching. We examined the successful 20032009 spawning sites of WBSSH in the main spawning ground, the Greifswalder Bodden lagoon. Instead of using common techniques such as diving or underwater videography, which are usually unsuitable for mapping large areas, we applied a model approach. We tracked herring larvae at length 610 mm, recorded by larval surveys during MarchJune of the respective years, back to their hatching sites using a Lagrangian particle backtracking model. We compared the spawning areas identified by the model with the results of earlier field studies; however, we also analysed variations between years, larval length groups, and different applied growth models, which are needed to define hatch-dates. Although spawning sites could not be identified with high precision because of the strong diffusion in the area studied, results indicate that larvae up to 10 mm length are caught near their hatching sites. However, the location of successful spawning sites varied largely between years, with the main hatching sites situated in the Strelasund and the eastern entrance of the lagoon. This may reflect variations in spawning-site selection or quality. A better knowledge of the locations and relative importance of, and the processes occurring on, the different spawning sites will provide an important contribution to the sustainable management of this commercially valuable herring stock.
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1136
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Auteur Freon, P.; Avadi, A.; Soto, W.M.; Negron, R.
Titre Environmentally extended comparison table of large-versus small- and medium-scale fisheries : the case of the Peruvian anchoveta fleet Type Article scientifique
Année 2014 Publication Revue Abrégée Canadian Journal of Fisheries and Aquatic Sciences
Volume (down) 71 Numéro 10 Pages 1459-1474
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Résumé Literature on small-scale fisheries usually depicts them as preferable over large-scale-industrial fisheries regarding societal benefits (jobs, jobs per investment) and relative fuel efficiency (e. g., Thomson 1980). We propose an environmentally extended Thomson table for comparing the Peruvian anchoveta (Engraulis ringens) fleets of purse seiners, backed up by methodological information and augmented with life cycle assessment (LCA)-based environmental performance information, as a more comprehensive device for comparing fleets competing for the same resource pool. Findings from LCA and a previous study on the anchoveta steel fleet together allowed characterizing the whole Peruvian anchoveta fishery. These results, along with socioeconomic indicators, are used to build an environmentally extended Thomson table of the fleet's main segments: the steel industrial, the wooden industrial, and the wooden small-and medium-scale (SMS) fleets. In contrast with the world figure, the Peruvian SMS fleets show a fuel performance nearly two times worse than the industrial fleets, due to economies of scale of the latter (although the small-scale segment itself (<10 m(3)) performs similarly to the industrial steel fleet). Furthermore, the absolute number of jobs provided by the industrial fisheries is much larger in Peru than those provided by the SMS fisheries. This is due to the relatively larger development of the industrial fishery, but as in previous studies, the SMS fleets generate more employment per tonne landed than the industrial fleet, as well as more food fish and less discards at sea.
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1149
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Auteur Kaplan, D.; Chassot, E.; Amande, J.M.; Dueri, S.; Demarcq, H.; Dagorn, L.; Fonteneau, A.
Titre Spatial management of Indian Ocean tropical tuna fisheries: potential and perspectives Type Article scientifique
Année 2014 Publication Revue Abrégée Ices Journal of Marine Science
Volume (down) 71 Numéro 7 Pages 1728-1749
Mots-Clés Bycatch; conservation; Indian Ocean; Marine protected areas (MPAs); pelagic; spatial management of fisheries; tropical tuna fisheries
Résumé Effective use of spatial management in the pelagic realm presents special challenges due to high fish and fisher mobility, limited knowledge and significant governance challenges. The tropical Indian Ocean provides an ideal case study for testing our ability to apply existing data sources to assessing impacts of spatial management on tuna fisheries because of several recent controversial spatial closures. We review the scientific underpinnings of pelagic MPA effects, spatio-temporal patterns of Indian Ocean tuna catch, by catch and fish movements, and the consequences of these for the efficacy of spatial management for Indian Ocean tropical tuna fisheries. The tropical Indian Ocean is characterized by strong environmental fluctuations, regular seasonal variability in catch, large observed tuna displacement distances, relatively uniform catch-per-unit-effort and bycatch rates over space, and high fisher mobility, all of which suggest significant variability and movement in tropical tuna fisheries that are simply not well adapted to static spatial closures. One possible exception to this overall conclusion would be a large time/area closure east of Somalia. If closed for a significant fraction of the year it could reduce purse-seine bycatch and juvenile tuna catch. Dynamic closures following fish migratory patterns are possible, but more focused information on fish movements will be needed for effective implementation. Fortunately, several recent improvements in conventional fishery management and reporting will likely enhance our ability to evaluate spatial and non-spatial management options in the near future, particularly as pertaining to bycatch species.
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1199
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