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| Registros recuperados: 129 | |
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| Fromentin, Jean-marc. |
| In 1963, the leading fisheries targeting Atlantic bluefin tuna (Thunnus thynnus) in the Norwegian Sea and North Sea suddenly collapsed without any warning. Little is known about this collapse and several hypotheses have been put forward, such as changes in migratory routes, recruitment failure or eradication of a sub-population: all of these hypotheses could result from natural causes and/or from overfishing. To help explain this mysterious event, an original data set of the main bluefin tuna fisheries of the 20th century, including total catch and size composition of the catch, has been compiled and analysed. The results reveal a strong and unambiguous link between the Nordic purse seine and Spanish trap fisheries during the 1950s and 1960s. However, this... |
| Tipo: Text |
Palavras-chave: Thunnus thynnus; Retrospective analysis; Population structure; Migration patterns; Fisheries collapse. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-6425.pdf |
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| Fromentin, Jean-marc; Kell, Laurence T. |
| An integrative simulation framework was built to evaluate the consequences of variability attributable to changes in carrying capacity or the stock’s migration pattern of Atlantic bluefin tuna on the ICCAT stock assessment and management procedures. We also evaluated the performances of stock assessment methods with respect to their ability to provide good estimates of MSY, FMSY and BMSY and tested the robustness of the current ICCAT management strategy to uncertainty about the true dynamics and historical exploitation levels. The results clearly indicate that the VPA performances were seriously impaired if the long-term variations in catches are due to changes in migration/availability. There is further considerable confounding between the underlying... |
| Tipo: Text |
Palavras-chave: Thunnus thynnus; Stock assessment; VPA; Biological reference points; MSY; Management strategy; Simulation model. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/00192/30295/28786.pdf |
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| Granger, Victoria; Bez, Nicolas; Fromentin, Jean-marc; Meynard, Christine; Jadaud, Angelique; Merigot, Bastien. |
| Mapping diversity indices, that is estimating values in all locations of a given area from some sampled locations, is central to numerous research and applied fields in ecology. Two approaches are used to map diversity indices without including abiotic or biotic variables: (i) the indirect approach, which consists in estimating each individual species distribution over the area, then stacking the distributions of all species to estimate and map a posteriori the diversity index, (ii) the direct approach, which relies on computing a diversity index in each sampled locations and then to interpolate these values to all locations of the studied area for mapping. For both approaches, we document drawbacks from theoretical and practical viewpoints and argue... |
| Tipo: Text |
Palavras-chave: Interpolation methods; Map; Quadratic entropy; Spatial statistics; Species diversity; Species richness; Beta-diversity. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00257/36819/37060.pdf |
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| Planque, Benjamin; Fromentin, Jean-marc. |
| Spatial and temporal patterns of Calanusfinmarchicus and C. helgolandicus (Copepoda, Calanoida) were investigated in the northeast Atlantic and the North Sea from 1962 to 1992. The seasonal cycle of C.finmarchicus is characterised by a single peak of abundance in spring, whereas the seasonal cycle of C. helgolandicus shows 2 abundance maxima, one in spring and one in autumn. The former species mainly occurs in northern regions (limited by the 55*N parallel in the North Sea and by the 50*N parallel in the open ocean). The latter species shows 2 types of spatial patterns, occurring in the Celtic Sea during spring and in the Celtic Sea plus the North Sea in autumn. Differences in seasonal spatial patterns of Calanus species may result from different responses... |
| Tipo: Text |
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| Ano: 1996 |
URL: http://archimer.ifremer.fr/doc/00033/14458/11760.pdf |
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| Kell, Laurence T; Fromentin, Jean-marc; Gauthiez, F; Restrepo, Victor. |
| The Ad Hoc Working Group on the Precautionary Approach (SCRS/99/11) recommended the development of a simulation modelling framework to investigate the performance of stock specific management strategies under a variety of realistic hypothesis about population and fishery dynamics. This paper describes a preliminary simulation model based on East Atlantic bluefin tuna developed using flexible software that allows the implications for management of a variety of plausible hypotheses about stock and fishery dynamics to be explored. The intention is to illustrate the ways in which such models can be used and the types of advice that they can provide |
| Tipo: Text |
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| Ano: 2000 |
URL: http://archimer.ifremer.fr/doc/00194/30566/28991.pdf |
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| Fromentin, Jean-marc. |
| The present paper proposes a simple descriptive analysis of the ICCAT bluefin tuna tagging database. Since 1954, about 91.2% of the tags were released in the West Atlantic and 8.8% in the East Atlantic. The great majority of tags was recaptured in their area of release, i.e., 95.7% and 97.25% for the East and the West Atlantic, respectively. The number of tags released in the West and recaptured in the East (102) was about 5 times higher than the reverse (19), but the percentage of transatlantic migrations from East-to-West (4.3%) was about 2 times higher than the one from West-to-East (2.25%). The percentage of transatlantic migrations varies over time, especially from West-to-East. It was much higher during the 90’s (7.6%) than in the three previous... |
| Tipo: Text |
Palavras-chave: Conventional tag; Migration rates; Thunnus thynnus; East and West Atlantic stocks. |
| Ano: 2002 |
URL: http://archimer.ifremer.fr/doc/00194/30495/28904.pdf |
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| Fromentin, Jean-marc; Farrugio, Henri. |
| In 2003, IFREMER implemented an observer program on board of the French purse seiner targeting bluefin tuna (BFT) in the Mediterranean Sea to collect the size composition of catches. The protocol and the sampling design were established by IFREMER and the operations were carried out by two independent scientific observers (each one following a given boat over two distinguished fishing seasons). The 788 BFT measured by the two observers during the ~ 190 fishing days were mostly small/juveniles fish and solely represented 2.7% of the total catches. The sampling appears largely insufficient to be representative of this fleet and was furthermore strongly biased (big BFT being under-sampled). From our viewpoint, the implementation of a joint observer program on... |
| Tipo: Text |
Palavras-chave: Atlantic bluefin tuna; Catch; Size composition; Observer; Purse seine; Mediterranean; By-catch. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/00194/30502/28912.pdf |
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| Corbineau, A; Rouyer, Tristan; Cazelles, B; Fromentin, Jean-marc; Fonteneau, A; Menard, Felix. |
| We analysed the patterns of variation that characterize 33 catch time series of large pelagic fishes exploited by the Japanese and Taiwanese longline fisheries in the Indian Ocean from 1968 to 2003. We selected four species, the yellowfin (Thunnus albacares), the bigeye (T. obesus), the albacore (T. alalunga), and the swordfish (Xiphias gladius) and aggregated data into five biogeographic provinces of Longhurst (2001). We carried out wavelet analyses, an efficient method to study non-stationary time series, in order to get the time-scale patterns of each signals. We then compared and grouped the different wavelet spectra using a multivariate analysis to identify the factors (species, province or fleet) that may influence their clustering. We also... |
| Tipo: Text |
Palavras-chave: Indian Ocean; Dipole Mode Index; Longline fisheries; Wavelet analysis; Time series analysis; Pelagic fishes. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-4714.pdf |
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| Morfin, Marie; Fromentin, Jean-marc; Jadaud, Angelique; Bez, Nicolas. |
| This study analyzes the temporal variability/stability of the spatial distributions of key exploited species in the Gulf of Lions (Northwestern Mediterranean Sea). To do so, we analyzed data from the MEDITS bottom-trawl scientific surveys from 1994 to 2010 at 66 fixed stations and selected 12 key exploited species. We proposed a geostatistical approach to handle zero-inflated and non-stationary distributions and to test for the temporal stability of the spatial structures. Empirical Orthogonal Functions and other descriptors were then applied to investigate the temporal persistence and the characteristics of the spatial patterns. The spatial structure of the distribution (i.e. the pattern of spatial autocorrelation) of the 12 key species studied remained... |
| Tipo: Text |
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| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00087/19860/17507.pdf |
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| Gros, Philippe; Biseau, Alain; Fromentin, Jean-marc; Thebaud, Olivier. |
| The report is focused on the research priorities pertaining to the implementation of the ‘maximum sustainable yield’ (MSY) and of the ‘ecosystem approach to fisheries’ (EAF). The MSY is first examined, taking account of its relevance as a management objective, of its link with maximum economic yield (MEY), and of its close relationship with ecosystem productivity and fishing capacity. Related research priorities are identified. In the second part, emphasis is put on EAF, a very challenge for fishery scientists. The extension of fisheries science towards an ecosystem dimension (including human activities) and the integration of uncertainty have opened up large fields of research. Priorities are presented by domain. Five principal areas of knowledge and... |
| Tipo: Text |
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| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/00013/12408/9194.pdf |
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| Van Beveren, Elisabeth; Bonhommeau, Sylvain; Fromentin, Jean-marc; Bigot, Jean-louis; Bourdeix, Jean-herve; Brosset, Pablo; Roos, David; Saraux, Claire. |
| Since 2007, the ecosystem of the Gulf of Lions has shifted to a different regime, characterised by a low anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) biomass and a remarkably high sprat (Sprattus sprattus) biomass. Surprisingly, the abundance and recruitment of anchovy and sardine remained high. To understand which processes (bottom-up or top-down control, etc.) could have caused this shift, we studied the changes in body condition, growth and size and age of anchovy, sardine and sprat over 1984–1985 and 1992–2012, using data from scientific surveys. The annual age structure of anchovy and sardine was estimated using Bayesian mixture models based on size frequency data with priors on the age–length relationship derived from independent... |
| Tipo: Text |
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| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00192/30335/29917.pdf |
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| Brosset, Pablo; Fromentin, Jean-marc; Menard, Frederic; Pernet, Fabrice; Bourdeix, Jean-herve; Bigot, Jean-louis; Van Beveren, Elisabeth; Perez Rodia, Maria A.; Choy, Sandrine; Saraux, Claire. |
| As condition is a key variable in population dynamics (especially for survival, growth and reproduction), the use of well-defined and accurate fish condition indices is capital. In particular, condition indices (morphometric, bioenergetic and biochemical) have never been compared and validated for the European anchovy Engraulis encrasicolus, the European pilchard Sardina pilchardus and the European sprat Sprattus sprattus. The accuracy of two indirect methods, the morphometric relative condition index Kn and the bioenergetics index determined with the Distell Fish Fatmeter was investigated by comparing with a direct measure of relative lipid content carried out with a thin layer chromatography-flame ionization detector. Estimations from the fatmeter... |
| Tipo: Text |
Palavras-chave: Anchovy; Fatmeter; Lipids; Mediterranean Sea; Sardine; Sprat. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00226/33741/32304.pdf |
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| Brophy, Deirdre; Haynes, Paula; Arrizabalaga, Haritz; Fraile, Igaratza; Fromentin, Jean-marc; Garibaldi, Fulvio; Katavic, Ivan; Tinti, Fausto; Karakulak, F. Saadet; Macias, David; Busawon, Dheeraj; Hanke, Alex; Kimoto, Ai; Sakai, Osamu; Deguara, Simeon; Abid, Nouredinne; Santos, Miguel Neves. |
| Two stocks of bluefin tuna (Thunnus thynnus) inhabit the north Atlantic; the western and eastern stocks spawn in the Gulf of Mexico and the Mediterranean Sea respectively. Trans-Atlantic movements occur outside spawning time whereas natal homing maintains stock structure. Commercial fisheries may exploit a mixed assemblage of both stocks. The incorporation of mixing rates into stock assessment is precluded by uncertainties surrounding stock discrimination. Otolith shape descriptors were used to characterise western and eastern stocks of Atlantic bluefin tuna in the present study and to estimate stock composition in catches of unknown origin. Otolith shape varied with length and between locations and years. Within a restricted size range (200-297-cm fork... |
| Tipo: Text |
Palavras-chave: Elliptical Fourier analysis; Population structure; Stock mixture analysis. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00346/45745/45381.pdf |
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| Fromentin, Jean-marc; Lopuszanski, Daniel. |
| This study presents the results of an electronic tagging programme on mature Atlantic bluefin tuna (ABFT) that has been conducted since 2007 offshore of the French Mediterranean Coast. The spatial distributions of ABFT showed little year-to-year variation and the fish concentrated in a small area of the central northwestern Mediterranean, where they may stay for several months. The individual tracks display sinuous trajectories in this area, indicating the possibility of feeding behaviour. No fish went out to the North Atlantic, but several fish displayed some migration to the southern western Mediterranean Sea during winter and the central Mediterranean during the spawning season. The homing behaviour of one fish after a full year as well as the back and... |
| Tipo: Text |
Palavras-chave: Feeding area; Front; Marine protected area; Pop-up archival tag; Spatial distribution; Thunnus thynnus. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00165/27637/25835.pdf |
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| Registros recuperados: 129 | |
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