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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; Restrepo, Victor. |
| At the ICCAT symposium on bluefin tuna that held in Santander in April 2008, Tangen et al.(2009) presented a first quantification of the fishing effort deployed by the Norwegian fishery targeting bluefin tuna in the North Sea and Norwegian Sea. Using a year-class curve analysis on the Norwegian CPUE, this document presents the first estimates of mortality rates of Atlantic bluefin tuna that migrated north from the mid-1950s to the late 1970s. The results indicate that bluefin tuna would have experienced a total mortality rate (Z) of 0.2 to 0.4 yr-1 (i.e. F at around 0.3 yr-1) during the late 1950s, 0.2 yr-1 during the 1960s and 0.1 yr-1 afterwards (assuming M=0.1 yr-1). These results appear to be rather robust and consistent with the VPA estimates from the... |
| Tipo: Text |
Palavras-chave: Thunnus thynnus; Fishing and natural mortalities; Year-class curves; Stock assessment. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/00192/30294/28783.pdf |
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| Fromentin, Jean-marc; Fonteneau, Alain; Restrepo, Victor. |
| During the last SCRS plenary meeting, the sub-committee on environment suggested to present a document on the ‘Ecosystem Approach to Fisheries’ (EAF). This document firstly recalls the general scientific and institutional background of EAF, then we propose a synoptic view of EAF, including four main domains: governance, exploitation, resources and impacts on ecosystems. The way that EAF is tackled within the various tuna commissions is then summarised. Finally, we rapidly examine the way the SCRS could cope with EAF issues and we suggest to merge the sub-committee on environment with this on by-catch into a single subcommittee on ecosystem. |
| Tipo: Text |
Palavras-chave: Ecosystem; Resources; Exploitation; Governance; Environment; By-catch. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/00192/30334/28809.pdf |
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| Restrepo, Victor; Arrizabalaga, Haritz; Ortiz De Urbina, J M; Fromentin, Jean-marc. |
| A standard yield per recruit (YPR) analysis is used to analyse the effects of minimum size regulations on bluefin tuna from the Eastern stock (East Atlantic and Mediterranean). Analyses were based on a selectivity vector computed over the period 1990- 1994 for which data were more reliable and VPA (performed during the 2002 stock assessment) showed a relatively good convergence. This selectivity vector was modified according to different minimum size regulations and implementation error levels. It is concluded that: (i) perfect implementation of the size limit regulation adopted in 2004 would increase YPR by 4.3% relative to the size limit adopted in 2002, and by 8.8% relative to the pattern realized in the early 1990s; (ii) YPR is however expected to... |
| Tipo: Text |
Palavras-chave: Yield/recruit; Yield predictions; Size limit regulations; Bluefin tuna.. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/00194/30545/28964.pdf |
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| Fromentin, Jean-marc; Bonhommeau, Sylvain; Kell, Laurence; Restrepo, Victor. |
| Estimating the productivity of an exploited marine species is not an easy or a trivial task. In the case of Atlantic bluefin tuna, the productivity can hardly be estimated from the natural mortality rates or the stock recruitment relationships because the former have never been estimated for this species from scientific data, but only “guesstimated”, while the latter remain highly uncertain for both the eastern stock (BFTE) and the western stock (BFTW). To get a better idea of bluefin tuna productivity, we thus applied the approach by Jennings et al. (1998) who proposed a surrogate of r, r’, named the potential rate of population increase. We compared this parameter and age-at-maturity (and to some extent the individual growth curves) of 25 species... |
| Tipo: Text |
Palavras-chave: Thunnus thynnus; Population growth rate; Fecundity; Maturity; CITES criteria. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00192/30293/28777.pdf |
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| Fromentin, Jean-marc; Restrepo, Victor. |
| Variations in recruitment and year-class strength of fish populations is a well known feature which can be related to three main factors: 1) human activity, mainly through overexploitation of the spawning stock, but also through pollution of the spawning and nursery areas; 2) biological processes, such as predation, cannibalism and competition and 3) environmental events. Life history traits of Atlantic tuna make the probability of a stable recruitment much higher for tropical tuna than temperate ones, but the latter are more adapted to the risks of recruitment failures than the former. As noise in the recruitment can lead to pseudo-cyclic variations in SSB and yields, trends in stock size and catches are also more likely in temperate Atlantic tuna. All... |
| Tipo: Text |
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| Ano: 2001 |
URL: http://archimer.ifremer.fr/doc/00194/30562/28983.pdf |
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| Gilman, Eric; Chaloupka, Milani; Dagorn, Laurent; Hall, Martin; Hobday, Alistair; Musyl, Michael; Pitcher, Tony; Poisson, Francois; Restrepo, Victor; Suuronen, Petri. |
| Bycatch in fisheries can have profound effects on the abundance of species with relatively low resilience to increased mortality, can alter the evolutionary characteristics and concomitant fitness of affected populations through heritable trait-based selective removals, and can alter ecosystem functions, structure and services through food web trophic links. We challenge current piecemeal bycatch management paradigms, which reduce the mortality of one taxon of conservation concern at the unintended expense of others. Bycatch mitigation measures may also reduce intraspecific genetic diversity. We drew examples of broadly prescribed ‘best practice’ methods to mitigate bycatch that result in unintended cross-taxa conflicts from pelagic longline, tuna purse... |
| Tipo: Text |
Palavras-chave: Bycatch; Conflicts; Decision support tool; Fisheries-induced evolution; Holistic management; Integrated management. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00475/58693/61206.pdf |
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