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Registros recuperados: 123
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A catch curve analysis for east Atlantic and Mediterranean bluefin tuna ArchiMer
Kell, Laurence; Bonhommeau, Sylvain; Fromentin, Jean-marc.
A catch-curve analysis using catch-at-age (CAA) data is performed to evaluate recent changes in selection pattern of the eastern Atlantic and Mediterranean bluefin tuna fishery. This was done in order to detect changes following the implementation of the Recovery Plan.
Tipo: Text Palavras-chave: Bluefin tuna; Catch curves; Management; Selectivity; Stock assessment.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00191/30272/28732.pdf
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A management strategy evaluation framework for Mediterranean Atlantic bluefin tuna ArchiMer
Kell, L. T.; Fromentin, Jean-marc.
This paper presents an example of Management Strategy Evaluation (MSE) for Mediterranean and East Atlantic bluefin tuna using the FLR open source framework. Scenarios corresponding to alternative plausible hypotheses about the stock dynamics were used to evaluate alternative management strategies and to test their robustness to implementation error e.g. catch mis-reporting. The strategies evaluated correspond to i) harvest control rule (HCR) based upon F0.1 (a proxy for FMSY ) with an objective of restoring the stock to a level that would “ permit the maximum sustainable catch” and ii) a reduction of fishing mortality on immature fish. The main conclusions were that the F0.1 HCR alone would not result in the recovery of the stock in the next 15 years and...
Tipo: Text Palavras-chave: Thunnus thynnus; Management plans; Management strategy evaluation; Simulation model.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/00194/30477/28884.pdf
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A participatory scenario method to explore the future of marine social-ecological systems ArchiMer
Planque, Benjamin; Mullon, Christian; Arneberg, Per; Eide, Arne; Fromentin, Jean-marc; Heymans, Johanna Jacomina; Hoel, Alf Håkon; Niiranen, Susa; Ottersen, Geir; Sandø, Anne Britt; Sommerkorn, Martin; Thébaud, Olivier; Thorvik, Thorbjørn.
Anticipating future changes in marine social‐ecological systems (MSES) several decades into the future is essential in the context of accelerating global change. This is challenging in situations where actors do not share common understandings, practices, or visions about the future. We introduce a dedicated scenario method for the development of MSES scenarios in a participatory context. The objective is to allow different actors to jointly develop scenarios which contain their multiple visions of the future. The method starts from four perspectives: “fisheries management,” “ecosystem,” “ocean climate,” and “global context and governance” for which current status and recent trends are summarized. Contrasted scenarios about possible futures are elaborated...
Tipo: Text Palavras-chave: Barents Sea; Future studies; Multiple perspectives; Participatory fisheries management; Storylines; Uncertainty.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00485/59621/62647.pdf
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A phytosociological method for interpreting plankton data ArchiMer
Fromentin, Jean-marc; Ibanez, F.; Legendre, P..
Multivariate techniques allow data sets to be summarised, but are not deslgned to causally model ecological phenomena. The ambiguity of the interpretation results from the ambiguity of the scaling space. The phytosociological method proposed by Grandjouan (1982; These d'etat, Universite Louis Pasteur, Strasbourg) is a general interpretive framework allowing separate consideration of 3 distinct reference spaces. a geographical space to visualise the spatio-temporal distribution of the descriptors, an ecological space showing the effects of the environmental variables on the biological descriptors, and a bio-ethological space showing the statistically meaningful species cornmunities. It is thus possible to define the position of each biological category and...
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Ano: 1993 URL: http://archimer.ifremer.fr/doc/00033/14454/11756.pdf
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A simulation framework to evaluate management strategies for Atlantic tunas: a preliminary example based on east Atlantic bluefin ArchiMer
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
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Ano: 2000 URL: http://archimer.ifremer.fr/doc/00194/30566/28991.pdf
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A state-space model to derive bluefin tuna movement and habitat from archival tags ArchiMer
Royer, Francois; Fromentin, Jean-marc; Gaspar, P.
Archival tagging provides a unique way to study the spatial dynamics and habitat of pelagic fish. This technique generates lagrangian data of a particular type in marine ecology: although highly informative about processes at different scales (e.g. horizontal movements versus diving behaviour), such data are impaired by location errors and the lack of combination with actual environmental variability. The present paper introduces a framework for modelling bluefin tuna movement in relation to its habitat, using records of light, depth and temperature from archival tags. Based on data assimilation concepts and methods, we show how an explicit formulation of the observation process and the statistics of external variables (e.g. ambient temperature) can...
Tipo: Text Palavras-chave: Tag; Archival; Habitat; Movement; Bluefin tuna.
Ano: 2005 URL: http://archimer.ifremer.fr/doc/2005/publication-671.pdf
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A year-class curve analysis to estimate mortality of Atlantic bluefin tuna caught by the Norwegian fishery from 1956 to 1979 ArchiMer
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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Aerial surveys of bluefin tuna in the Western Mediterranean sea: retrospective, prospective, perspective ArchiMer
Bonhommeau, Sylvain; Farrugio, Henri; Poisson, Francois; Fromentin, Jean-marc.
While the current stock status of bluefin tuna (BFT) has been considered as declining, there remain considerable data limitations for its stock assessment in the Mediterranean Sea. The collection of fishery-independent data reveals to be crucial to compensate for the lack of Mediterranean purse seine CPUE indices as well as to overcome a potential halt in the bluefin tuna fishery that would impede the monitoring of the stock and the comparison to reference points. Here we present a retrospective of aerial surveys that have been carried out since 2000. It includes the protocol as well as a retrospective of temporal and spatial distribution of detected schools. We then propose several perspectives that could improve the data collection method itself and the...
Tipo: Text Palavras-chave: Atlantic bluefin tuna; Aerial survey; Index of abundance; Gulf of Lions; Strip transect.
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00192/30292/28775.pdf
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Aerial surveys to monitor bluefin tuna abundance and track efficiency of management measures ArchiMer
Bauer, Robert; Bonhommeau, Sylvain; Brisset, Blandine; Fromentin, Jean-marc.
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...
Tipo: Text Palavras-chave: Thunnus thynnus; Index of abundance; Fishery-independent; Gulf of Lions; Mediterranean Sea; Strip transect; Distance sampling.
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00281/39192/45096.pdf
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An attempt to evaluate the recent management regulations of the east Atlantic and Mediterranean bluefin tuna stock through a simple simulation model ArchiMer
Fromentin, Jean-marc.
This manuscript proposes a simple simulation model to investigate the implications to the resources of the recent management regulations adopted for the East Atlantic and Mediterranean bluefin tuna stock. If perfectly implemented, the new regulations on minimum size and closed fishing areas mostly lead to a change in the selectivity pattern which moves towards older fish, so decreasing growth-overfishing. The potential sustainable yields therefore considerably increase (almost double in comparison to those that would be obtained without the new regulations) while the SSB can rapidly reach 20% of the virgin SSB. An error of 20% in the implementation of these new regulations affects their efficiencies and does not seem to allow the rebuilding of the SSB at a...
Tipo: Text Palavras-chave: Bluefin tuna; Management regulations; Stock rebuilding; Simulation model.
Ano: 2008 URL: http://archimer.ifremer.fr/doc/00192/30297/28787.pdf
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An evaluation of changes in stock productivity and consequences for management. An example based on North Atlantic albacore Thunnus alalunga ArchiMer
Kell, Laurence T; Fromentin, Jean-marc.
Reference points are important elements of fisheries management and the supporting scientific advisory frameworks. However, fish stocks can fluctuate extensively over a large range of spatial and temporal scales independent of human exploitation and there has been a classical tendency to assume a dichotomy, i.e., that changes in fish populations are primarily attributable either to exploitation or to environmental variability. Therefore we look at variability in surplus production and examine the relative impacts of the environment and exploitation on the productivity of North Atlantic albacore (Thunnus alalunga). The analysis revealed that variations were driven by environmental effects. It was also found that substantial variations in time-series of...
Tipo: Text Palavras-chave: Thunnus alalunga; Albacore; Fisheries management; FLR; Reference points; Stationary processes; Surplus production..
Ano: 2011 URL: http://archimer.ifremer.fr/doc/00192/30282/28758.pdf
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An evaluation of the implications of population structure on the current bluefin tuna advice framework ArchiMer
Kell, Laurence T; Fromentin, Jean-marc; Bonhommeau, Sylvain.
The objectives of the comprehensive ICCAT Atlantic-Wide Research Programme on Bluefin Tuna (GBYP) are to improve data collection, knowledge of key biological and ecological processes, assessment models and management. An important element of which is to develop a robust advice framework consistent with the Precautionary Approach. The current advice framework, which is based upon Virtual Population Analysis, demonstrates how a Management Strategy Evaluation (MSE) framework can be used to evaluate the robustness of management advice to uncertainty about stock structure.
Tipo: Text Palavras-chave: Bluefin; Management Strategy Evaluation; Robustness; Stock structure; VPA.
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00192/30277/28740.pdf
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An overview on the use of precautionary approach and tuna management ArchiMer
Fonteneau, Alain; Fromentin, Jean-marc.
This paper develops a critical overview of the various problems and uncertainties faced in tuna stock assessment, management and conservation. This presentation is based on Atlantic tunas, but also on various tuna stocks worldwide. Tuna jisheries management is characterized by major uncertainties in the stock assessment; since these stock assessments are always done only on jishery data which are often biased. Fortunately most tuna stocks are showing a strong resistance to overfishing. These major characteristics of tuna stocks and jisheries, and the bias in the scientific analysis, are presented and discussed. As a result, many of the reference point recommended for the precautionary approach applied to jisheries are often quite inappropriate for tuna...
Tipo: Text Palavras-chave: Tunas; Precautionay approach; Atlantic; Management; Assessment.
Ano: 2000 URL: http://archimer.ifremer.fr/doc/00194/30564/28984.pdf
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Analysing multiple time series and extending significance testing in wavelet analysis ArchiMer
Rouyer, Tristan; Fromentin, Jean-marc; Stenseth, N; Cazelles, B.
In nature, non-stationarity is rather typical, but the number of statistical tools allowing for non-stationarity remains rather limited. Wavelet analysis is such a tool allowing for non-stationarity but the lack of an appropriate test for statistical inference as well as the difficulty to deal with multiple time series are 2 important shortcomings that limits its use in ecology. We present 2 approaches to deal with these shortcomings. First, we used 1/f beta models to test cycles in the wavelet spectrum against a null hypothesis that takes into account the highly autocorrelated nature of ecological time series. To illustrate the approach, we investigated the fluctuations in bluefin tuna trap catches with a set of different null models. The 1/f beta models...
Tipo: Text Palavras-chave: Maximum covariance analysis; Surrogates; Wavelet significance testing; Wavelet clustering; Multivariate time series; Non stationarity.
Ano: 2008 URL: http://archimer.ifremer.fr/doc/2008/publication-4291.pdf
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Analysis of the potential impact of several management measures for eastern Atlantic bluefin tuna on the basis of yield per recruit ArchiMer
Arrizabalaga, Haritz; Restrepo, Victor; Fromentin, Jean-marc; Ortiz De Urbina, J M.
A standard yield per recruit (YPR) analysis is used to analyse the effects of minimum size regulations and time area closures on bluefin tuna from the eastern stock (east Atlantic and Mediterranean). Analyses were based on a fishing mortality 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 fishing mortality vector was modified according to some combinations of minimum size regulations and time area closures. It is concluded that: (i) PSmed is the main contributor to catch at age in the range of ages 1-13; (ii) The minimum size regulations considered would increase the YPR more than the time area closures, but these would enhance SPR...
Tipo: Text Palavras-chave: Yield/recruit; Yield predictions; Size limit regulations; Time-area closures; Bluefin tuna.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/00192/30329/28806.pdf
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Are EU log-books suitable to compute size frequencies of bluefin tuna catches of the French purse seiners? ArchiMer
Fromentin, Jean-marc.
The 2001 size composition of Atlantic bluefin tuna catches of the French purse seiners has been estimated from the EU log-books and appears roughly in agreement with those estimated from the local seafood traders between 1982 and 1998. However, the accuracy of the 2001 size composition remains uncertain because of a lack of a standard protocol and of sampling on catch coming from heterogeneous and/or multiple shoals. Regarding the spatial and temporal dynamic of the French fishery, an observer program should be implemented to correct and validate the size frequencies of these catches.
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Ano: 2002 URL: http://archimer.ifremer.fr/doc/00194/30526/28938.pdf
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Assessing causal links in fish stock–recruitment relationships ArchiMer
Pierre, Maud; Rouyer, Tristan; Bonhommeau, Sylvain; Fromentin, Jean-marc.
Understanding whether recruitment fluctuations in fish stock arise from stochastic forcing (e.g. environmental variations) rather than deterministic forces (e.g. intrinsic dynamics) is a long standing question with important applied consequences for fisheries ecology. In particular, the relationship between recruitment, spawning stock biomass and environmental factors is still poorly understood, even though this aspect is crucial for fisheries management. Fisheries data are often short, but arise from complex dynamical systems with a high degree of stochastic forcing, which are difficult to capture through classic modelling approaches. In the present study, recent statistical approaches based on the approximation of the attractors of dynamical systems are...
Tipo: Text Palavras-chave: Causality; Forecasting models; Marine.
Ano: 2018 URL: http://archimer.ifremer.fr/doc/00408/51930/52555.pdf
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Association between bluefin tuna schools and oceanic features in the western Mediterranean ArchiMer
Royer, Francois; Fromentin, Jean-marc; Gaspar, P.
We present an analysis of the distribution of bluefin tuna Thunnus thynnus schools spotted during aerial surveys in the Gulf of Lions, in relation to oceanographic features. Bio-optical and thermal properties of the sea surface derived from high-resolution sensors (AVHRR and SeaWiFS) were studied on a daily basis, and an edge-detection technique was applied to detect frontal zones. Geostatistics and point-process analyses were used to evaluate the role of the environment in structuring the spatial pattern of bluefin tuna (BFT). The distribution of schools spotted was strongly non-stationary both in space and time; this is believed to be an effect of the survey design (transect sampling) and the influence of transient oceanographic structures (surface...
Tipo: Text Palavras-chave: Thunnus thynnus; Gulf of Lions; Point process analysis; Front detection; Sea surface temperature; Ocean colour; Aggregation.
Ano: 2004 URL: http://archimer.ifremer.fr/doc/00000/10786/7585.pdf
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Atlantic bluefin tuna: population dynamics, ecology, fisheries and management ArchiMer
Fromentin, Jean-marc; Powers, Joseph.
Both old and new information on the biology and ecology of Atlantic bluefin tuna have confronted scientists with research challenges: research needs to be connected to current stock-assessment and management issues. We review recent studies on habitat, migrations and population structure, stressing the importance of electronic tagging results in the modification of our perception of bluefin tuna population dynamics and behaviour. Additionally, we question, from both scientific and management perspectives, the usefulness of the classical stock concept and suggest other approaches, such as Clark's contingent and metapopulation theories. Current biological information confirms that a substantial amount of uncertainty still exists in the understanding of...
Tipo: Text Palavras-chave: Tuna fisheries; Thunnus thynnus; Stock assessment and management; Population structure; Population dynamics; Atlantic bluefin tuna.
Ano: 2005 URL: http://archimer.ifremer.fr/doc/2005/publication-797.pdf
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Back to the future: investigating historical data of bluefin tuna fisheries ArchiMer
Fromentin, Jean-marc.
The exploitation of Atlantic bluefin tuna in the Mediterranean Sea goes back to the first millennium before Christ and the Romans already took benefits of the bluefin tuna reproductive migration to catch them. Bluefin tuna catch did not remain stable along its millennium exploitation history but displayed conspicuous long-term fluctuations that could result from environmentally-driven changes in the bluefin tuna migration routes. The Nordic fisheries that took place in the Norwegian and North Sea in the early 1920s were the most spectacular example of Atlantic bluefin tuna fisheries collapse. During the 1950s, the Nordic fisheries were the most productive ones, catching up to 18,000 tons/year, but they suddenly crashed down without any warning in 1963....
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Ano: 2009 URL: http://archimer.ifremer.fr/doc/00193/30467/28872.pdf
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