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| Registros recuperados: 61 | |
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| Doray, Mathieu; Petitgas, Pierre; Nelson, Laetitia; Mahevas, Stephanie; Josse, E; Reynal, Lionel. |
| Fish-aggregating devices (FADs) are increasingly used worldwide to enhance tuna catches. Meanwhile, ecosystem-based management of this fishery is constrained by a paucity of information regarding the interaction of FAD-associated tuna aggregations with their local environment. This paper reports the results of a nine-month study around a FAD moored near Martinique Island, aimed at assessing the effects of the local environment on the variability of monthly estimates of proximate tuna biomass. Dual-frequency, active acoustics provided highresolution quantitative data on the pelagic community around the FAD, from fish to micronekton forage. Geostatistics were used to compute biomass estimates of the tuna aggregation comprising most of the FADassociated fish... |
| Tipo: Text |
Palavras-chave: Lesser Antilles; Tuna; Environment; Geostatistics; Biomass estimation; Fish aggregating device. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2008/publication-6162.pdf |
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| Doray, Mathieu; Petitgas, Pierre; Josse, E. |
| Universal kriging was used to model the spatio-temporal variability in the acoustic density of tuna aggregations recorded during star echosounding surveys around moored fish aggregating devices (FADs) in Martinique (Lesser Antilles). The large-scale deterministic drift in the tuna spatial distribution was modeled using an advection-diffusion equation applied to animal grouping. Residuals from the drift were modeled as a random component with small-scale spatial correlation. An estimation variance formula was derived from this deterministic-statistical mixed model to assess the mean precision of density estimates of daytime tuna aggregation. The mean relative error obtained with our star design for daytime surveys was 24%. The methodology was applied to... |
| Tipo: Text |
Palavras-chave: Acoustic survey precision; Advection diffusion model; Moored fish aggregating devices; Tuna; Geostatistics. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-4559.pdf |
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| Petitgas, Pierre; Woillez, Mathieu; Doray, Mathieu; Rivoirard, Jacques. |
| Marine research survey data on fish stocks often show a small proportion of very high-density values, as for many environmental data. This makes the estimation of second-order statistics, such as the variance and the variogram, non-robust. The high fish density values are generated by fish aggregative behaviour, which may vary greatly at small scale in time and space. The high values are thus imprecisely known, both in their spatial occurrence and order of magnitude. To map such data, three indicator-based geostatistical methods were considered, the top-cut model, min–max autocorrelation factors (MAF) of indicators, and multiple indicator kriging. In the top-cut and MAF approaches, the variable is decomposed into components and the most continuous ones... |
| Tipo: Text |
Palavras-chave: Top-cut; MAF; Indicators; Co-kriging; Skewed distribution; Anchovy; Bay of Biscay; Fisheries survey data; Aggregation. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00429/54021/55339.pdf |
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| Doray, Mathieu. |
| Knowledge of the acoustic response of single fish (or Target Strength: TS) is of prime importance for acoustic target classification and abundance estimation. This report investigates the effect of TS~length equation selection on the anchovy and sardine biomass estimates derived from PELGAS acoustic and fishing survey data. We aim at assessing the respective effects of b20 and depth correction terms on anchovy biomass acoustic estimates derived from the PELGAS survey, in order to evaluate the magnitude of a potential non linear effect of fish depth on acoustic biomass estimates. The PELGAS 2012, 2014, 2015 and 2016 survey data are re-analysed using several TS equations with different b20 values and/or depth correction terms to assess the respective effects... |
| Tipo: Text |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00377/48839/49265.pdf |
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| Doray, Mathieu; Berger, Laurent; Le Bouffant, Naig; Coail, Jean-yves; Vacherot, Jean-philippe; De La Bernardie, Xavier; Moriniere, Pierre; Lys, Elisabeth; Schwab, Romain; Petitgas, Pierre. |
| Measuring fish target strength (TS) in the wild is challenging because: (i) TS varies versus physical (orientation relative to the incident sound wave, size, and depth) and physiological fish attributes (maturity and condition), (ii) the target species and its aforementioned attributes are difficult to assess in near real time, and (iii) in the case of packed fish schools, accepted echoes may originate from multiple unresolved targets. We propose a method for controlled TS measurements of densely packed small pelagic fish during daytime, based on the joint use of a Remotely Operated Towed Vehicle, “EROC”, with a pelagic trawl fitted with a codend opening system, “ENROL”. EROC, equipped with a 70-kHz split-beam echosounder (Simrad EK60) and a low-light... |
| Tipo: Text |
Palavras-chave: Acoustics; Deformed cylinder model; Engraulis encrasicolus; Remotely operated vehicle; Target strength; Video. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00346/45693/45623.pdf |
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| Doray, Mathieu; Josse, E; Gervain, P; Reynal, Lionel; Chantrel, Josselin. |
| From April 2003 to April 2004 monthly sea surveys were conducted around 2 fish aggregating devices (FADs) moored at 2000 and 2500 m depth in Martinique (Lesser Antilles). The use of a dual frequency splitbeam echosounder combined with an underwater camera and fishing methods allowed assessment of average space and time distribution of pelagic fish aggregated beneath the FADs, as well as identification of their overall size and species composition. At daytime, 4 fish aggregations were identified at each FAD, representing 4 distinct types: i) an aggregation of small juvenile tuna (mean fork length, FL: 30 cm) observed very close to the surface in 25% of daytime periods; ii) a small surface aggregation dominated by carangids, Caranx crysos, present in 65% of... |
| Tipo: Text |
Palavras-chave: Lesser Antilles; Tuna; Aggregative behaviour; Small scale fishery; Underwater video; Acoustics; Fish aggregating device. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-3634.pdf |
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| Doray, Mathieu; Petitgas, Pierre; Masse, Jacques. |
| Estimer la biomasse d'un stock de poissons par acoustique nécessite de combiner des données de nature diverse collectées le long du parcours d'échantillonnage (Woillez et al., 2009). Il s'agit essentiellement de combiner trois champs de données spatialisées : une carte de densités acoustiques attribuées aux poissons, une carte de proportions d'espèces et une carte de longueurs moyennes. |
| Tipo: Text |
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| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00003/11447/7997.pdf |
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| Doray, Mathieu; Petitgas, Pierre; Romagnan, Jean-baptiste; Huret, Martin; Duhamel, Erwan; Dupuy, Christine; Spitz, Jérôme; Berger, Laurent; Dorémus, Ghislain; Bourriau, Paul; Grellier, Patrick; Massé, Jacques; Sanchez, Florence. |
| The initial objective of the PELGAS integrated survey was to assess the biomass of small pelagic fish in the Bay of Biscay in spring. Sampling has been extended to study the spatial structure and dynamics of the pelagic ecosystem in springtime. The PELGAS survey has produced since 2000 long-term time-series of spatially-explicit data and indices, describing the main pelagic ecosystem components: hydrology, phytoplankton, mesozooplankton, fish and megafauna. In addition to small pelagic fish biomass estimates used for fish stock assessment, the survey now delivers two types of ecosystem products: standard gridded maps of ecosystem parameters, and a time series dataset of indicators of the Bay of Biscay pelagic ecosystem state. The evolution of the PELGAS... |
| Tipo: Text |
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| Ano: 2018 |
URL: http://archimer.ifremer.fr/doc/00457/56844/58693.pdf |
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| Doray, Mathieu; Huret, Martin; Couturier, Christian; Doublet, Sylvain. |
| L'objectif des Nation Unies pour le développement durable de l’Océan (ODD14) peut il se décliner dans le secteur de la pêche en France ? Et si oui comment ? La principale fonction de la pêche (et de l’aquaculture) françaises étant la fourniture de produits de la mer à des fins alimentaires, nous replaçons la pêche (et de l’aquaculture) françaises dans le contexte plus large de l’approvisionnement alimentaire du pays. Nous présentons le scénario prospectif Afterres2050, qui propose une trajectoire vers un approvisionnement alimentaire durable pour le France (et quelques voisins) en 2050. Afterres2050 est un scénario technique qui vise à satisfaire nos besoins, en alimentation, en énergie, et en matériaux à l’horizon 2050, dans le respect des écosystèmes,... |
| Tipo: Text |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00512/62325/66583.pdf |
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| Doray, Mathieu; Le Bouffant, Naig; Verin, Yves. |
| The Simrad ME70 multibeam echosounder has been operated in the Eastern Channel during the IBTS2010 sea survey (14-26/01/10). The objectives were: i) to observe dense night-time herring aggregations ii) to record ME70 data in fisheries research mode during demersal trawling to further test the interest of ME70-derived bathymetric indicators for demersal habitats characterisation iii) to acquire night-time acoustic data of sound scattering layers and compare them with synoptic mesopelagic trawls results i) to test the integration of a sidewards looking echosounder (Simrad ER60 120kHz, 2.5x10°) in the R/V acoustic data recording system. |
| Tipo: Text |
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| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00068/17890/15420.pdf |
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| Doray, Mathieu; Mahevas, Stephanie; Trenkel, Verena. |
| Few analyses have been performed to estimate the efficiency of trawls targeting demersal fish using the ratio of catches and acoustic densities. In summer 2006, acoustic and fishing data were collected simultaneously over 3 d by three fishing vessels equipped with identical pelagic trawls in the Bay of Biscay. Variography identified moderate spatial autocorrelation in the acoustic backscatter at a mean scale of 3 km, a scale slightly smaller than the mean haul length (3.5 km), indicating that fish horizontal availability did not influence trawl efficiency. Acoustic backscattering densities expressed as nautical area scattering coefficients (NASCs) recorded in the trawled layer were compared with equivalent NASC (ENASC) values calculated from the species... |
| Tipo: Text |
Palavras-chave: Availability; Bay of Biscay; Catchability; Generalized linear model; Geostatistics; Hake; Vulnerability. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00002/11372/7980.pdf |
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| Duhamel, Erwan; Doray, Mathieu; Huret, Martin; Sanchez, Florence; Lespagnol, Patrick; Doremus, Ghislain; Lemerre, Charlotte. |
| The Pelgas16 acoustic survey has been carried out with very good weather conditions (regular low wind, medium temperatures) for the whole area, from the South of the bay of Biscay to the west of Brittany. The help of commercial vessels (two pairs of pelagic trawlers and a single one) during 18 days provided about 120 valid identification hauls instead of about 60 before 2007 when Thalassa was alone to identify echotraces. Their participation increased the precision of identification of echoes and some double hauls permitted to confirm that results provided by the two types of vessels (R/V and Fishing boats) were comparable and usable for biomass estimate purposes. These commercial vessels participated to the PELGAS survey in a very good spirit of... |
| Tipo: Text |
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| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00344/45546/45157.pdf |
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| Petitgas, Pierre; Doray, Mathieu; Masse, Jacques; Grellier, Patrick. |
| Fish length frequency histograms from research surveys are of prime importance for identifying habitats of different life stages, as well as for stock assessment. However, no method has thus far been available for mapping these histograms as spatially varying curves. Here, a procedure is applied to map spatially connected curves, and detail is given on how it can be applied to map the length frequency histograms. At each sample location, a fish length frequency histogram is given as a vector of non-independent values. The histogram is first modelled as a polynomial expansion on the basis of orthogonal polynomials. Then, the polynomial coefficients are mapped by co-kriging, after fitting a model of co-regionalization. The length frequency map is finally... |
| Tipo: Text |
Palavras-chave: Co-kriging; European anchovy; Fish length; Functional kriging; Habitat; Mapping curves. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00049/16042/13581.pdf |
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| Registros recuperados: 61 | |
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