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| Registros recuperados: 61 | |
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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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| 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; Stequert, Bernard; Taquet, Marc. |
| Daily growth increments measured in the otolith of Thunnus atlanticus were used to estimate the age and growth of individuals. which were sampled from an artisanal fishery operating around fish aggregating devices (FADs) moored off Martinique Island. In this study, 76 otoliths were analysed for fish ranging from 20 to 68 cm fork lengths (FL). The fish were caught using trolling lines at depths ranging from 0 to 10 m. Counts were made, under a light microscope, on the external part of the transverse section of the sagittae, from the primordium to the ventral edge. The mean coefficient of variation of the age reading was 2.4%. To validate readings, the number of increments for 11 individuals was counted using both optic and scanning electron microscopes. The... |
| Tipo: Text |
Palavras-chave: Thunnus atlanticus; Daily increment; Otolith; Age. |
| Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/2004/publication-396.pdf |
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| Petitgas, Pierre; Renard, Didier; Desassis, Nicolas; Huret, Martin; Romagnan, Jean-baptiste; Doray, Mathieu; Woillez, Mathieu; Rivoirard, Jacques. |
| This paper presents a novel application of the geostatistical multivariate method known as min–max autocorrelation factors (MAFs) for analysing fisheries survey data in a space–time context. The method was used to map essential fish habitats and evaluate the variability in time of their occupancy. Research surveys at sea on marine fish stocks have been undertaken for several decades now. The data are time series of yearly maps of fish density, making it possible to analyse the space–time variability in fish spatial distributions. Space–time models are key to addressing conservation issues requiring the characterization of variability in habitat maps over time. Here, the variability in fisheries survey data series is decomposed in space and time to address... |
| Tipo: Text |
Palavras-chave: MAF; Space-time; Habitat; Mapping; Sardine; Bay of Biscay. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00599/71157/69915.pdf |
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| Blanluet, Arthur; Doray, Mathieu; Berger, Laurent; Romagnan, Jean-baptiste; Le Bouffant, Naig; Lehuta, Sigrid; Petitgas, Pierre. |
| Sound scattering layers (SSLs) are observed over a broad range of spatio-temporal scales and geographical areas. SSLs represent a large biomass, likely involved in the biological carbon pump and the structure of marine trophic webs. Yet, the taxonomic composition remains largely unknown for many SSLs. To investigate the challenges of SSL sampling, we performed a survey in a small study area in the Northern Bay of Biscay (France) by combining broadband and narrowband acoustics, net sampling, imagery and video recordings. In order to identify organisms contributing to the observed SSLs, we compared measured frequency spectra to forward predicted spectra derived from biological data. Furthermore, to assess the confidence in SSL characterization, we evaluated... |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00588/70035/67955.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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| Lambert, C.; Authier, M.; Doray, Mathieu; Doremus, G.; Spitz, J.; Ridoux, V.. |
| Most oceanographic systems, especially shelf ecosystems, are characterised by interannual variability in the timing, extent and intensity of their seasonal patterns. Such interannual variations have important consequences on top predator habitat preferences. Capitalising on oceanographic surveys performed every spring since 2004 in the Bay of Biscay (BoB), this study explored interannual variations in habitat preferences exhibited by five mobile top predator species: bottlenose and common dolphins, auks, fulmars and northern gannets. We expected to find species with similar habitat preferences every year or species exhibiting important variability in their habitat preferences. First, we identified with a Principal Component Analysis (PCA) three different... |
| Tipo: Text |
Palavras-chave: Habitat preference; Temporal variability; Cetaceans; Seabirds; North Atlantic; Bay of Biscay. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00431/54226/55549.pdf |
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| Doray, Mathieu; Coulon, Noémie; Huret, Martin; Le Bouffant, Naig; Berger, Laurent. |
| This study aims at estimating the anchovy biomass that was missed in the echosounder surface blind zone during the PELGAS survey, in an attempt to explain the relative difference between acoustic and DEPM biomass estimates in springtime 2019 in the Bay of Biscay. Acoustic data collected by a side-looking echosounder are analysed in order to estimate the negative bias introduced in acoustic biomass estimates by the acoustic blind zone. Corrected anchovy acoustic biomass estimates and maps are compared to DEPM ones, in an attempt to reconcile egg and acoustic estimates. Remaining discrepancies are discussed in the light of acoustic and egg biomass estimation assumptions. We showed that surface school biomass can be calculated while applying standard acoustic... |
| Tipo: Text |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00662/77412/79072.pdf |
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| Duhamel, Erwan; Doray, Mathieu; Huret, Martin; Sanchez, Florence; Authier, Matthieu; Bergot, Patricia. |
| The Pelgas15 acoustic survey has been carried out with globally 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 130 valid identification hauls instead of about 50 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: 2015 |
URL: http://archimer.ifremer.fr/doc/00278/38972/37513.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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| Duhamel, Erwan; Doray, Mathieu; Huret, Martin; Sanchez, Florence; Lespagnol, Patrick; Doremus, Gislain; Le Bourdonnec, Pierre. |
| An acoustic survey (PELGAS) is carried out every year in the Bay of Biscay in spring onboard the French research vessel Thalassa. The objective of PELGAS survey is to study the abundance and distribution of pelagic fish in the Bay of Biscay. The main target species are anchovy and sardine but they are considered in a multi-specific context and within an ecosystemic approach as they are located in the centre of pelagic ecosystem. The Pelgas17 acoustic survey has been carried out with medium weather conditions (regular wind, low atmospheric 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 110 valid... |
| Tipo: Text |
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| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00398/50903/51674.pdf |
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| Doray, Mathieu. |
| EchoR is a R statistical software package aiming at: i) handling pre-processed fisheries acoustics data collected during sea surveys, and ii) computing standard ec(h)osystemic indicators based on those fisheries acoustics data. This tutorial gives examples of EchoR capacities. |
| Tipo: Text |
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| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00128/23879/21814.pdf |
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| Registros recuperados: 61 | |
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