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Auteur |
Ruiz, J.; Batty, A.; Chavance, P.; McElderry, H.; Restrepo, V.; Sharples, P.; Santos, J.; Urtizberea, A. |
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Titre |
Electronic monitoring trials on in the tropical tuna purse-seine fishery |
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Article scientifique |
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Année |
2015 |
Publication |
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Revue Abrégée |
ICES J. Mar. Sci. |
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Volume  |
72 |
Numéro |
4 |
Pages |
1201-1213 |
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Mots-Clés |
Bycatch; catch composition; data collection; electronic monitoring system; observers; Purse seining; Tropical tuna |
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Résumé |
The difficulty of ensuring adequate statistical coverage of whole fleets is a challenge for the implementation of observer programmes and may reduce the usefulness of the data they obtain for management purposes. This makes it necessary to find cost-effective alternatives. Electronic monitoring (EM) systems are being used in some fisheries as an alternative or a complement to human observers. The objective of this study was to test the use and reliability of EM on the tropical tuna purse-seine fishery. To achieve this objective, seven trips of tuna purse seiners operating in the three Oceans were closely monitored to compare the information provided by EM and on-board observers to determine if EM can reliably document fishing effort, set type, tuna catch, and bycatch. Total tuna catch per set was not significantly different between EM and observer datasets; however, regarding species composition, only main species matched between EM and observers. Success on set-type identification using EM varied between 98.3 and 56.3%, depending on the camera placement. Overall, bycatch species were underestimated by EM, but large bodied species, such as billfishes, were well documented. The analyses in this study showed that EM can be used to determine the fishing effort (number of sets) and total tuna catch as reliably as observers can. Set-type identification also had very promising results, but indicated that refinement of the methods is still needed. To be fully comparable with observer data, improvements for accurately estimating the bycatch will need to be developed in the application and use of the EM system. Operational aspects that need to be improved for an EM programme to be implemented include standardizing installation and on-board catch handling methodology as well as improvements in video technology deployment. |
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en |
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1054-3139, 1095-9289 |
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Numéro d'Appel |
MARBEC @ isabelle.vidal-ayouba @ |
collection |
1335 |
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Auteur |
Sardenne, F.; Chassot, E.; Fouche, E.; Menard, F.; Lucas, V.; Bodin, N. |
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Titre |
Are condition factors powerful proxies of energy content in wild tropical tunas? |
Type |
Article scientifique |
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Année |
2016 |
Publication |
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Revue Abrégée |
Ecol. Indic. |
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Volume |
71 |
Numéro |
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Pages |
467-476 |
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Mots-Clés |
body condition; cod gadus-morhua; condition indexes; ecosystem; Energy variability; fish; Fish health; katsuwonus-pelamis; Large pelagic species; Proximate composition; thunnus-albacares; western indian-ocean; Yellowfin tuna |
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Résumé |
The “condition” is used as an indicator of fish health and is generally equated with the quantity of energy reserves. Biometric condition factors have been widely used and preferred over costly and time-consuming biochemical condition. Here, we investigated the relevance of four common condition factors based on biometric measurements (Le Cren's index, girth -length index, gonado-somatic index and hepato-somatic index) and of size- and weight -based empirical models to describe the physiological condition of tropical tunas. Biometric condition factors of bigeye (Thunnus obesus), skipjack (Katsuwonus pelamis) and yellowfin (Thunnus albacares) tunas sampled throughout 2013 in the western Indian Ocean region were assessed against benchmark biochemical indices (lipid content, protein content, triacylglycerol:sterol ratio and energy density) estimated in tissues with different physiological functions, i.e. red muscle, white muscle, liver, and gonads. Our findings suggest that tropical tunas do not store lipids in white muscle and that protein content is less variable than lipid content, which largely varies with ontogeny and the seasons according to tissue and species. This variability induced inconsistency between biometric factors, including the empirically adjusted ones, and biochemical indices, with the exception of the gonado-somatic index that fitted well to the composition of the gonads in the three species, and especially in females. (C) 2016 Elsevier Ltd. All rights reserved. |
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English |
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ISSN |
1470-160x |
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Numéro d'Appel |
MARBEC @ alain.herve @ |
collection |
1697 |
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Auteur |
Kaplan, D.; Chassot, E.; Amande, J.M.; Dueri, S.; Demarcq, H.; Dagorn, L.; Fonteneau, A. |
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Titre |
Spatial management of Indian Ocean tropical tuna fisheries: potential and perspectives |
Type |
Article scientifique |
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Année |
2014 |
Publication |
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Revue Abrégée |
Ices Journal of Marine Science |
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Volume |
71 |
Numéro |
7 |
Pages |
1728-1749 |
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Mots-Clés |
Bycatch; conservation; Indian Ocean; Marine protected areas (MPAs); pelagic; spatial management of fisheries; tropical tuna fisheries |
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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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ISSN |
1054-3139 |
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Numéro d'Appel |
MARBEC @ isabelle.vidal-ayouba @ |
collection |
1199 |
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Auteur |
Sempo, G.; Dagorn, L.; Robert, M.; Deneubourg, J.-L. |
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Titre |
Impact of increasing deployment of artificial floating objects on the spatial distribution of social fish species |
Type |
Article scientifique |
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Année |
2013 |
Publication |
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Revue Abrégée |
Journal of Applied Ecology |
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Volume |
50 |
Numéro |
5 |
Pages |
1081-1092 |
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Mots-Clés |
behaviour-based modelling; Bycatch; Fad; Fob; sustainable fishery; tuna |
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Résumé |
* Approximately 300 pelagic fish species naturally aggregate around floating objects (FOBs) at the surface of the oceans. Currently, more than 50% of the world catch of tropical tuna comes from the industrial tuna fisheries around drifting FOBs. Greater understanding of the complex decision-making processes leading to this aggregation pattern and the impact of the massive release of artificial FOBs by fishermen on the spatial distribution and management of tuna is needed. * We analyse how the interplay between social (relationships between individuals) and non-social (responses to the environment) behaviours may affect the spatial distribution of a population in a multi-FOB environment. Taking the example of tropical tunas associating with FOBs and using differential equations and stochastic simulations, we examine how, when increasing the number of FOBs, fish aggregation dynamics and the distribution of the population among patches are affected by the population size, level of sociality and the natural retentive and/or attractive forces of FOBs on individual tuna. * Our model predicts that, depending on the species' level of sociality, fish will be scattered among FOBs or aggregated around a single FOB based on the number of FOBs deployed in a homogeneous oceanic region. * For social species, we demonstrated that the total fish catch is reduced with increasing FOBs number. Indeed, for each size of population, there are a number of FOBs minimizing the total population of fish associated with FOBs and another number of FOBs maximizing the total population of associated fish. * Synthesis and applications. In terms of fisheries management, the total catch volume is directly linked to the total number of floating objects (FOBs) for non-social species, and any limit on the number of sets would then result in a limit on the total catch. For social species (e.g. tuna), however, increasing the number of FOBs does not necessarily lead to an increase in the total catch, which is a non-intuitive result. Indeed, our model shows that, for specific values of the parameters, deploying a greater number of FOBs in the water (all other parameters being constant) does not necessarily help fishermen to catch more tuna, but does increase the level of fishing effort and bycatch. |
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ISSN |
1365-2664 |
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Numéro d'Appel |
LL @ pixluser @ |
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265 |
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Auteur |
Fromentin, J.-M.; Bonhommeau, S.; Arrizabalaga, H.; Kell, L.T. |
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Titre |
The spectre of uncertainty in management of exploited fish stocks: The illustrative case of Atlantic bluefin tuna |
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Article scientifique |
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Année |
2014 |
Publication |
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Revue Abrégée |
Marine Policy |
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Volume |
47 |
Numéro |
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Pages |
8-14 |
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Mots-Clés |
tuna |
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0308-597x |
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LL @ pixluser @ |
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323 |
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