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| Registros recuperados: 129 | |
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| Rouyer, Tristan; Fromentin, Jean-marc; Menard, Felix; Calzelles, B; Briand, K; Pianet, R; Planque, Benjamin; Stenseth, N. |
| The patterns of variations in fisheries time series are known to result from a complex combination of species and fisheries dynamics all coupled with environmental forcing (including climate, trophic interactions, etc.). Disentangling the relative effects of these factors has been a major goal of fisheries science for both conceptual and management reasons. By examining the variability of 169 tuna and billfish time series of catch and catch per unit effort (CPUE) throughout the Atlantic as well as their linkage to the North Atlantic Oscillation (NAO), we find that the importance of these factors differed according to the spatial scale. At the scale of the entire Atlantic the patterns of variations are primarily spatially structured, whereas at a more... |
| Tipo: Text |
Palavras-chave: Time series analysis; North Atlantic Oscillation; Atlantic tuna. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-3984.pdf |
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| 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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| 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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| 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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| Fromentin, Jean-marc. |
| In 2002, about 40% of the yield of the French purse seine fleet targeting bluefin tuna came from the Gulf of Lions, 38% from the Balearic Islands and about 22% from the Malta-Lybia area (a new area for this fleet). The fleet caught, in the Gulf of Lions, mostly juvenile bluefin (mainly 2 and 3 years old), whereas both juveniles and adults were targeted and caught in the Balearic and Maltese areas. As in 2001, the 2002 size composition of bluefin catches have been estimated from the EU log-books and both years looked very similar. Calculating Kolmogorov-Smirnov two sample tests between the yearly size compositions of 1990-1995 and those of 2001 and 2002, indicated significant differences between these two pools of data. Finally, we confirm that if the... |
| Tipo: Text |
Palavras-chave: Atlantic bluefin tuna; Catch statistics. |
| Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/00194/30482/28889.pdf |
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| Cury, Philippe M.; Fromentin, Jean-marc; Figuet, Sarah; Bonhommeau, Sylvain. |
| The relationship between spawning fish abundance and the number of offspring, the so-called stock-recruitment relationship, is crucial for fisheries management and conservation measures. Using the most comprehensive data set ever assembled, we quantify this relationship for 211 fish stocks worldwide, revealing a global pattern with a pervasive asymptotic shape that shows increasing recruitment reaching an upper limit for values around half to two-thirds of parental biomass. This corroborates previous theoretical and modeling results. However, parental biomass is a predictor for only 5% to 15% of the variance in recruitment, demonstrating the weak predictive power of the stock-recruitment relationship in marine fish populations. Thus, there is a need to... |
| Tipo: Text |
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| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00253/36441/35000.pdf |
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| Fonteneau, Alain; Fromentin, Jean-marc. |
| This communication presents a global overview of Atlantic bluefin tuna biology, exploitation and management. The comparison between bluefin tuna and all other tuna species do show that this species is ranking number one among other tunas world wide in a wide range of its resources and fisheries characteristics. Bluefin tuna is for instance the gold winner in the category of fisheries (about 10,000 years of documented fisheries, the highest price in the market, the largest tuna taken), of its peculiar biology (large migration, homing, growth, etc.) and in the category of risks presently faced by the resource, because of its multiple scientific uncertainties still pending, its increasingly serious statistical problems and the heavy political context in the... |
| Tipo: Text |
Palavras-chave: Pêche; Durabilité; Pêche abusive; Migration; Caractéristique du cycle vital; Fisheries; Sustainability; Overfishing; Migration; Life history trait.. |
| Ano: 2003 |
URL: http://archimer.ifremer.fr/doc/00194/30568/28995.pdf |
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| Druon, Jean-noel; Fromentin, Jean-marc; Hanke, Alex R.; Arrizabalaga, Haritz; Damalas, Dimitrios; Ticina, Vjekoslav; Quilez-badia, Gemma; Ramirez, Karina; Arregui, Igor; Tserpes, George; Reglero, Patricia; Deflorio, Michele; Oray, Isik; Karakulak, F. Saadet; Megalbfonou, Persefoni; Ceyhan, Tevfik; Grubisic, Leon; Mackenzie, Brian R.; Lamkin, John; Afonso, Pedro; Addis, Piero. |
| An ecological niche modelling (ENM) approach was used to predict the potential feeding and spawning habitats of small (5-25kg, only feeding) and large (> 25kg) Atlantic bluefin tuna (ABFT), Thunnus thynnus, in the Mediterranean Sea, the North Atlantic and the Gulf of Mexico. The ENM was built bridging knowledge on ecological traits of ABFT (e.g. temperature tolerance, mobility, feeding and spawning strategy) with patterns of selected environmental variables (chlorophyll-a fronts and concentration, sea surface current and temperature, sea surface height anomaly) that were identified using an extensive set of precisely geo-located presence data. The results highlight a wider temperature tolerance for larger fish allowing them to feed in the northern –... |
| Tipo: Text |
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| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00308/41953/41803.pdf |
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| Royer, Francois; Fromentin, Jean-marc. |
| We present a methodology for the non-linear analysis of long-term ecological time series. Using a time-delay embedding procedure, we investigated the complexity of 1-dimensional signals and compared their structure to their stochastic counterparts. Recurrence-based statistics and surrogate testing were used for this purpose. The method was first tested on elementary models for illustrative purposes and its potentialities and limits reviewed. We then investigated the time structure of 6 Mediterranean bluefin tuna trap catches known to display long-term fluctuations. These time series showed significantly more determinism than linear stochastic processes, displaying more recurring patterns/states than stochastic surrogates. The short term structure of these... |
| Tipo: Text |
Palavras-chave: Embedding; Surrogate testing; Density dependence; Recurrence; Thunnus thynnus. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-1982.pdf |
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| 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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| Menard, Frederic; Fromentin, Jean-marc; Goy, J; Dallot, S. |
| This study describes the temporal fluctuations of doliolid populations sampled in the Bay of Villefranche-sur-Mer (Northwestern Mediterranean Sea) from 1967 to 1990. The abundance level of doliolids (strongly dominated by Doliolum nationalis and Dolioletta gegenbauri phorozooids) was estimated weekly according to Frontier's (1969) ordinal scale. Population abundance shows important interannual variations. The series displays a clear upward trend from the late 1960s to the early 1980s; thereafter, the abundances remain at a high and steady level. Five annual patterns of abundance level changes are identified, using cluster analysis. The influence of hydrological and meteorological conditions on doliolid abundance is tested using a Markov regression model... |
| Tipo: Text |
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| Ano: 1997 |
URL: http://archimer.ifremer.fr/doc/00093/20431/18098.pdf |
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| Brosset, Pablo; Lloret, Josep; Munoz, Marta; Fauvel, Christian; Van Beveren, Elisabeth; Marques, Virginie; Fromentin, Jean-marc; Menard, Frederic; Saraux, Claire. |
| Limited resources in the environment prevent individuals from simultaneously maximizing all life-history traits, resulting in trade-offs. In particular, the cost of reproduction is well known to negatively affect energy investment in growth and maintenance. Here, we investigated these trade-offs during contrasting periods of high versus low fish size and body condition (before/after 2008) in the Gulf of Lions. Female reproductive allocation and performance in anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) were examined based on morphometric historical data from the 1970s and from 2003 to 2015. Additionally, potential maternal effects on egg quantity and quality were examined in 2014/2015. After 2008, the gonadosomatic index increased for... |
| Tipo: Text |
Palavras-chave: Maternal effect; Northwest Mediterranean; Anchovy; Sardine. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00353/46458/46233.pdf |
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| Registros recuperados: 129 | |
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