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Registros recuperados: 27
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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 spatiotemporal study of bacterial community profiles associated with Atlantic bluefin tuna larvae, Thunnus thynnus L., in three Mediterranean hatcheries ArchiMer
Gatesoupe, Joel; Coves, Denis; Ortega, Aurelio; Papandroulakis, Nikos; Vadstein, Olav; De La Gandara, Fernando.
During the first 2 years of larval rearing trials with Atlantic bluefin tuna, survival was a challenging issue. As bacterial colonization of the gut has been shown to play a key role for other species, we studied the profiles of the microbiota associated with individual larvae at different stages in three distant hatcheries. The Bacterial Community Profile (BCP) was quantified based on PCR-DGGE analyses of partial amplicons from 16S rDNA. Considerable individual variability in BCP was observed before onset of feeding, and the BCP did not show regular fluctuation during ontogenesis. Microalgae were added to the rearing tanks in two of the three hatcheries, but it was not possible to distinguish the effect of location from the effect of algal addition on...
Tipo: Text Palavras-chave: Larval rearing; Bacterial diversity; DGGE; Thunnus thynnus.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00075/18648/16197.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 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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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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Biometric relationships and fattning rate of bluefin tuna "Thunnus thynnus thynnus" L. 1758 in Tunisian fish farm OceanDocs
Hattour, A.; Moussa, A..
An analysis of data from a Tunisian farm during the months of June to November of the year 2008 is presented. These data were broken down into two sets the first concern sampled fish while towing them to farm (wild set), the second set concern sampled specimen at the end of fattening process (fattening set). The wild group comprised specimens ranging from 90 to 276 cm fork length, and the fattened group included specimens from 105 to 310 сm. Juvenile proportion (Lf<130 сm) in fattened specimen (15.7%) was considerably smaller compared to the proportion in wild specimens (61,8%). The distribution of individual weights of slaughtered BFT shows the prevalence 31-50 kg specimen class (60.4%). The L-W relationships were determined for each of these sets....
Tipo: Journal Contribution Palavras-chave: Thunnus thynnus; Tuna fisheries; Length-weight relationships; Fish farms; Tuna; Fattening.
Ano: 2012 URL: http://hdl.handle.net/1834/5315
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Contribution à l'étude de la dynamique du thon rouge Atlantique - Approches écologiques et océanographiques ArchiMer
Royer, Francois.
[1] The spatial and temporal dynamics of Atlantic bluefin tuna, Thunnus thynnus, are here investigated through data analysis and statistical modelling. The local, regional and global scales are considered successively. A phenomenological approach is favoured, as well the extended use of image processing tools and estimation theory techniques. Their potential role in partially observed or ill-defined problems in marine ecology is presented and discussed. The acute need for frequency-explicit methods is in particular stressed out. Hypothesis testing and significance testing of ecological space/time processes are further discussed. [2] The first chapter depicts how surface fronts can structure the pelagic habitat: dedicated detection and mapping tools are...
Tipo: Text Palavras-chave: Archival tags; Kalman filter; Density dependence; Oceanic fronts; Time series; Thunnus thynnus; Marques archives; Filtre de Kalman; Densite dependence; Fronts oceaniques; Series temporelles; Thunnus thynnus.
Ano: 2005 URL: http://archimer.ifremer.fr/doc/2005/these-636.pdf
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Descriptive analysis of the ICCAT bluefin tuna tagging database ArchiMer
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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Determining bluefin tuna habitat through frontal features in the Mediterranean sea ArchiMer
Royer, Francois; Fromentin, Jean-marc; Farrugio, Henri; Gaspar, Philippe.
The distribution patterns of bluefin tuna schools observed during the STROMBOLI EU project (2000-2002) were analysed in relation to oceanographic conditions. High-resolution radiometers (AVHRR and SeaWiFS) were used on a daily basis to derive maps of environmental variability. An edge detection technique was especially applied to estimate the position of frontal features. Using a variety of geostatistical and point process techniques, we were able to show that the distribution of bluefin schools was partially driven by the occurrence of transient fronts in the Gulf of Lions. This is believed to be mainly a trophic association, since enhanced convergence and retention processes occur at fronts, possibly leading to higher prey densities (e.g. anchovies). The...
Tipo: Text Palavras-chave: Thunnus thynnus; Aerial survey; Gulf of Lions; Sea surface temperature; Ocean colour; Fronts.
Ano: 2005 URL: http://archimer.ifremer.fr/doc/00194/30504/28914.pdf
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Eastern Atlantic bluefin tuna: what we learn from historical time-series of trap catches ArchiMer
Ravier, Christelle; Fromentin, Jean-marc.
More than one hundred long-term time-series of bluefin tuna catches from the ancestral Mediterranean and Atlantic trap fisheries are used to (1) estimate historical range of BFT yields in the Mediterranean and adjacent Atlantic and (2) investigate spatial and temporal patterns of fluctuations in trap catches. Mean historical catches were around 110 000 tunas/year (± 50 000), i.e. 15 000 tons/year (∈[7 000;25 000]). Fluctuations in trap catches are of large magnitude, periods of high abundance being up to seven times higher than those of low abundance. More interesting was the occurrence of 100-year-long periodic fluctuations as well as 20-year cycles. These medium- to long-term fluctuations, representing more than 50% of the total variability in the...
Tipo: Text Palavras-chave: Thunnus thynnus; Time series analyses; Abundance; Population dynamics; Long-term changes; Trapfishing.
Ano: 2002 URL: http://archimer.ifremer.fr/doc/00194/30497/28906.pdf
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Environmental noise in spawning areas: the case of Atlantic bluefin tuna (Thunnus thynnus) ArchiMer
Royer, Francois; Fromentin, Jean-marc.
This paper provides an exploratory analysis aiming to seek whether the colour of environmental noise theory could help in understanding the intriguing reproductive strategy of Atlantic bluefin tuna (BFT). A frequency-based approach based on spectral exponents, f(beta) with beta < 0, is chosen and applied on 10 biogeographical provinces covering the North Atlantic. The major BFT spawning area, i.e. the Mediterranean Sea, was the only one to display a pink power spectrum, whereas open ocean regions displayed more reddened fluctuations, i.e. greater variance at low frequencies. Environmental noise in the Mediterranean could, thus, offer more favourable characteristics on the long-term than the open ocean. The implications of these findings are discussed in...
Tipo: Text Palavras-chave: Thunnus thynnus; Spectral analysis; Spawning; Sea surface temperature; Environmental noise.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-2437.pdf
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Estimating the productivity of Atlantic bluefin tuna from validated scientific data ArchiMer
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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Evaluation of the performance and robustness of VPA-based stock assessment and MSY-based management strategy to process error: the Atlantic bluefin tuna case study ArchiMer
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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Fluctuations à long terme du thon rouge: validité, origines et conséquences ArchiMer
Ravier, Christelle.
Describe and gain understanding on fluctuations in animal population over time and space is a central goal of population ecology. This is also crucial to ensure the sustainable management of exploited resources, particularly those with complex population dynamics such as the bluefin tuna. The goal of this work is to collect bluefin tuna catches from the ancestral Mediterranean and Atlantic trap fisheries to (i) characterise long-term fluctuations in bluefin tuna population migrating in the Mediterranean, (ii) analyse their causes et (iii) assess their implications for fisheries management. The bluefin tuna main biological and ecological characteristics are first detailed. Then, the first part presents the trap fishery, and the process of collect and...
Tipo: Text Palavras-chave: Biological reference point; V.p.a.; Management; Migration; N.a.o.; Temperature; Tunas/environment relationships; Population dynamics; Periodic fluctuations; Long term trend; Time series; East Atlantic; Mediterranean Sea; Trap fishery; Thunnus thynnus; Points biologiques de référence; V.p.a.; Modèle global; Migration; N.a.o.; Température; Relation thon/environnement; Dynamique de population; Fluctuations périodiques; Tendances à long terme; Séries temporelles; Atlantique Est; Méditerranée; Madrague; Thunnus thynnus.
Ano: 2003 URL: http://archimer.ifremer.fr/doc/2003/these-65.pdf
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Habitat use, vertical and horizontal behaviour of Atlantic bluefin tuna ( Thunnus thynnus ) in the Northwestern Mediterranean Sea in relation to oceanographic conditions ArchiMer
Bauer, Robert Klaus; Fromentin, Jean-marc; Demarcq, Herve; Bonhommeau, Sylvain.
We investigated the habitat utilization, vertical and horizontal behaviour of Atlantic bluefin tuna Thunnus thynnus (ABFT) in relation to oceanographic conditions in the northwestern Mediterranean Sea, based on 36 pop-up archival tags and different environmental data sets. Tags were deployed on early mature ABFT (127–255 cm) between July and November in 2007-2014, on the shelf area off Marseille, France. The data obtained from these tags provided 1643 daily summaries of ABFT vertical behaviour over 8 years of tag deployment. Based on a hierarchical clustering of this data, we could identify four principle daily vertical behaviour types, representing surface (≦10m) and subsurface (10–100 m) orientation, moderate (50–200 m) and deep (≧200m) diving behaviour....
Tipo: Text Palavras-chave: Thunnus thynnus; Habitat use; Spike dives; Fronts; Thermal stratification; Archival tags.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00382/49329/49709.pdf
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Investigating the performances of a bayesian biomass dynamic model with informative priors on Atlantic bluefin tuna ArchiMer
Simon, M; Fromentin, Jean-marc; Bonhommeau, Sylvain; Gaertner, Daniel; Etienne, Marie-pierre.
We examined the possibility of eliciting informative priors for the parameters of a biomass production model with emphasis on the intrinsic population growth rate of Atlantic bluefin tuna (Thunnus thynnus). We reviewed the literature to propose probability distribution functions for the vital rates and used a matrix population model structured by age (Leslie) to compute the population growth rate. A generalized biomass production model is applied on two CPUE and catch datasets (1976-1996 and 1976-2006) using informative priors. The population growth rate prior has a diffuse distribution and is very sensitive to young of the year mortality rate. Thus, we compared the performances of this prior with a commonly used prior for tunas population growth rate. We...
Tipo: Text Palavras-chave: Bayesian model; Population growth rate; Uncertainties; Natural mortality; CPUE; Tuna fisheries; Thunnus thynnus.
Ano: 2011 URL: http://archimer.ifremer.fr/doc/00192/30281/28756.pdf
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Lessons from the past: investigating historical data from bluefin tuna fisheries ArchiMer
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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Long-term fluctuations in bluefin tuna trap catches: are they environmentally driven? ArchiMer
Ravier-mailly, Christelle; Fromentin, Jean-marc.
We tested whether synchronous long-term fluctuations in Atlantic bluefin tuna (Thunnus thynnus) trap catches, collected from the ancestral Mediterranean and Atlantic trap fishery, might be related to environmental changes in NAO and/or in temperature. Spectral analyses of trap catches and temperature displayed similar spectra with peak at low frequency whereas those of the NAO exhibited a broad band spectrum. Regression analyses and tests of correlation did not reveal any clear relationship between trap catches and NAO. In contrast, long-term fluctuations in trap catches appear to be negatively and significantly related to long-term trends in temperature. Underlying processes that could explain such a relationship are discussed, with special focus on...
Tipo: Text Palavras-chave: Thunnus thynnus; NAO; Temperature; Trap fishery; Migration.
Ano: 2003 URL: http://archimer.ifremer.fr/doc/00194/30530/28940.pdf
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Migration, residency, and homing of bluefin tuna in the western Mediterranean Sea ArchiMer
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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