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| Registros recuperados: 23 | |
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| Dupre, Stephanie; Berger, Laurent; Le Bouffant, Naig; Scalabrin, Carla; Bourillet, Jean-francois. |
| Fishery acoustic surveys conducted in the Bay of Biscay and dedicated to monitoring and predicting pelagic ecosystem evolution reveal numerous active seeps on the Aquitaine Shelf, east of the shelf break, at water depths ranging from 140 to 185 m. Some acoustic anomalies recorded in the water column with hull-mounted single and multibeam echosounders are clearly caused by fluid escape at the seabed, most likely gases. These fluid emissions are associated at the seafloor with high backscatter subcircular small-scale mounds, on average less than 2 m high and a few metres in diameter. Based on near-bottom video and acoustic surveys, these mounds are interpreted to be by-products of gas seepage, possibly methane-derived authigenic carbonates. The spatial... |
| Tipo: Text |
Palavras-chave: Bay of Biscay; Aquitaine Shelf; Parentis Basin; Fluid; Seepage; Acoustics. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00201/31192/29888.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; 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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| Korneliussen, R; Diner, Noel; Ona, E; Berger, Laurent; Fernandes, P. |
| Acoustic surveys are used to estimate the abundance and distribution of many fish species, and have been based traditionally on data collected at a single acoustic frequency. Although it has been known for some time that the use of additional frequencies can provide information on the nature of the acoustic target, the knowledge and technology required to combine the so-called "multifrequency data" in an appropriate manner has been limited. The use of several transducers of different frequencies is now common on board research vessels and fishing vessels, so multifrequency data are often collected. In order for these data to be combined appropriately, their physical and spatial characteristics from each frequency should be as similar as possible. We detail... |
| Tipo: Text |
Palavras-chave: Species identification; Multifrequency acoustics; Data collection. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-5286.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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| Delacroix, Sylvain; Germain, Gregory; Berger, Laurent; Billard, Jean-yves. |
| Bubble sweep-down on oceanographic vessels generates acoustic perturbations. We propose in this work to characterize the sub-surface bubbles occurrence conditions from acoustic data analysis acquired during surveys in relatively shallow water with the IFREMER research vessels Thalassa and Pourquoi Pas?. The methodology of data analysis used in this work allows us to characterize the sailing conditions influence on bubble sweep-down occurrence. The correlation between sailing conditions and acoustic perturbations tends to demonstrate that the presence of bubbles under the hull is clearly related to the wind speed and natural aeration, and that surface bubbles are advected differently in the water column by the two vessels |
| Tipo: Text |
Palavras-chave: Bubble sweep-down; Acoustic perturbation; Ship motion. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00294/40557/39632.pdf |
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| Demer, Da; Berger, Laurent; Bernasconi, M; Bethke, E; Boswell, K; Chu, D; Domokos, R; Dunford, A; Fassler, S; Gauthier, S; Hufnagle, Lt; Jech, Jm; Le Bouffant, Naig; Lebourges-dhaussy, Anne; Lurton, Xavier; Macaulay, Gj; Perrot, Yannick; Ryan, T; Parker-stetter, S; Stienessen, S; Weber, T; Williamson, N. |
| Acoustic instrument calibration is fundamental to the quantitative use of its data for estimating aquatic resource abundance. Regular calibrations also allow instrument performance to be monitored to detect changes due to the environment or component dynamics, degradation, or failure. This is the second ICES Cooperative Research Report (CRR) focussed on calibrations of acoustic instruments. The first, CRR No. 144 (Foote et al., 1987), was published during the era of analogue electronics more than a quarter of a century ago. Since then, not only has the acoustic equipment improved vastly with digital electronics and signal processing, but the techniques for applying them to studies of marine organisms have both advanced and diversified. Motivating,... |
| Tipo: Text |
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| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00586/69821/67711.pdf |
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| Lefort, Riwal; Fablet, Ronan; Berger, Laurent; Boucher, Jm. |
| In this letter, we address the characterization of objects in 3-D sonar images of the water column obtained by a multibeam echo sounder. Compared with classic 2-D images from a monobeam echo sounder, these 3-D images provide finer scale observation of the pelagic biomasses and new tools to characterize 3-D distributions. By viewing object patterns as realizations of spatial point processes, we investigate descriptive spatial statistics. This method is then applied to 3-D fisheries acoustics data set for characterization of the distribution of pelagic fish schools. Reported experiments illustrate the relevance of the proposed descriptors. The comparison of our method with 2-D sonar data analysis further demonstrates the information gain from using 3-D sonar... |
| Tipo: Text |
Palavras-chave: Fisheries acoustics; Multibeam sensor; Object patterns in images; Point processes; Spatial statistics. |
| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00056/16769/14270.pdf |
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| Trenkel, Verena; Berger, Laurent; Bourguignon, Sebastien; Doray, Mathieu; Fablet, Ronan; Masse, Jacques; Mazauric, Valerie; Poncelet, Cyrille; Quemener, Gael; Scalabrin, Carla; Villalobos, Hector. |
| This paper provides an overview of the progress Ifremer has made recently in fisheries acoustics and the study of small pelagic fish by: i) pushing observation frontiers using a range of platforms including an autonomous underwater vehicle, AUV, ii) developing measuring instruments and methods and iii) studying fish distributions. Presently, information from several frequencies of single-beam echosounders is routinely collected together with data from the ME70 multibeam echosounder. For onboard data acquisition control the HERMES software was developed. The new MOVIES 3D software includes modules for simultaneous realistic 3D visualisation and post-processing such as bottom detection, school extraction and calculation of descriptors and integration of all... |
| Tipo: Text |
Palavras-chave: Multibeam echosounder; Oceanographic AUV; Pelagic fish; Fisheries acoustics. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/00000/11165/7517.pdf |
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| Fezzani, Ridha; Berger, Laurent. |
| An automated signal-based method was developed in order to analyse the seafloor backscatter data logged by calibrated multibeam echosounder. The processing consists first in the clustering of each survey sub-area into a small number of homogeneous sediment types, based on the backscatter average level at one or several incidence angles. Second, it uses their local average angular response to extract discriminant descriptors, obtained by fitting the field data to the Generic Seafloor Acoustic Backscatter parametric model. Third, the descriptors are used for seafloor type classification. The method was tested on the multi-year data recorded by a calibrated 90-kHz Simrad ME70 multibeam sonar operated in the Bay of Biscay, France and Celtic Sea, Ireland. It... |
| Tipo: Text |
Palavras-chave: Multibeam; Reflectivity; Backscatter angular response; Segmentation. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00423/53465/56648.pdf |
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| Bourguignon, Sebastien; Berger, Laurent; Scalabrin, Carla; Fablet, Ronan; Mazauric, Valerie. |
| Multibeam echosounders and sonars are increasingly used in fisheries acoustics for abundance estimation. Because of reduced side-lobe levels in the beam-array pattern, the new Simrad ME70 multibeam echosounder installed on board Ifremer's RV "Thalassa" has been designed to allow improved detection of fish close to the seabed. To achieve this objective, precise and unambiguous detection of the water-bottom interface is required, which raises the issue of bottom detection, especially in the outer beams. The bottom-detection method implemented in the ME70 is based on the amplitude of the reverberated echo. Such an approach is efficient for vertical beams, but less accurate for beams with higher incidence angles, typically 30°40° for the beam configurations... |
| Tipo: Text |
Palavras-chave: Multibeam echosounder; Fisheries; Bottom detection; Acoustics. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-6629.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... |
| Tipo: Text |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00588/70035/67955.pdf |
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| Trenkel, Verena; Berger, Laurent. |
| Fisheries acoustic instruments provide information on four major groups in aquatic ecosystems: fish with and without swim bladder (tertiary and quaternary consumers), fluidlike zooplankton (secondary consumers) and small gas bearing organisms such as larval fish and phytoplankton (predominantly primary producers). We entertain that this information is useable to describe the spatial structure of organism groups in pelagic ecosystems. The proposal we make is based on a multi-frequency indicator that synthesises in a single metric the shape of the acoustic frequency response of different organism groups, i.e. the dependence of received acoustic backscattered energy on emitting echosounder frequency. We demonstrate the development and interpretation of the... |
| Tipo: Text |
Palavras-chave: Acoustics; Frequency response curve; Monitoring; EOF; Ecosystem state. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00128/23886/21848.pdf |
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| Doray, Mathieu; Petitgas, Pierre; Romagnan, Jean-baptiste; Huret, Martin; Duhamel, Erwan; Dupuy, Christine; Spitz, Jérôme; Authier, Matthieu; Berger, Laurent; Doremus, Ghislain; Bourriau, Paul; Grellier, Patrick; Masse, Jacques; Sanchez, Florence. |
| The initial focus of the PELGAS integrated survey was to assess the small pelagic fish biomass in the Bay of Biscay in springtime, for fisheries management purposes. Sampling has been extended to produce long-term time-series of spatially-explicit data and indices, describing the main pelagic ecosystem components: hydrology, phytoplankton, mesozooplankton, fish and megafauna. A collaborative analysis of these datasets has brought new insights on the Bay of Biscay pelagic ecosystem summarized here. New results on single ecosystem components include an analysis of water samples to groundtruth the results of an ocean color algorithm aiming at detecting phytoplanktonic coccolithophores. New insights on mesozooplankton spatio-temporal distribution and energy... |
| Tipo: Text |
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| Ano: 2018 |
URL: http://archimer.ifremer.fr/doc/00445/55665/57331.pdf |
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| Trenkel, Verena; Mazauric, Valerie; Berger, Laurent. |
| Recently, Simrad in collaboration with Ifremer developed a calibrated, multibeam, vertical echosounder (ME70) for fisheries research. We describe its capabilities and technical limitations. The ME70 has up to 45 beams with distinct frequencies in the range 70120 kHz, spanning at most 150 degrees. All beams are stabilized in vessel roll and pitch. It has reduced side-lobe levels, up to -70 dB (two-way) instead of the -2S dB (one-way) of conventional systems. We outline research areas for which the ME70 might provide new types of information and hence lead to novel insights. We illustrate the potential contributions with datasets collected in the English Channel and on the continental-shelf break of the Bay of Biscay. Finally, future research and... |
| Tipo: Text |
Palavras-chave: Three dimensional; Behaviour; Acoustics; Abundance. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-4117.pdf |
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| Doray, Mathieu; Berger, Laurent; Coail, Jean-yves; Vacherot, Jean-philippe; Bavouzet, Gerard; Petitgas, Pierre. |
| The lack of specific Target Strength (TS) values for European anchovy (Engraulis encrasicolus) and sardine (Sardina Pilchardus) in the literature has been pointed out by the Working Group on Acoustic and Egg Surveys for Sardine and Anchovy in ICES Areas VIII and IX. The need for specific small pelagics TS measurements conducted in controlled environments was recognized by the group, to further investigate the adequacy of TS length equation used to derive fish stock estimates for clupeids in European waters. TS is a stochastic variable which largely varies in the wild, in response to changes in physical (tilt angle, depth) or biological (physiology) single fish attributes. The first requirement to make sound TS measurement is to accurately identify of the... |
| Tipo: Text |
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| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00055/16637/14133.pdf |
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| Registros recuperados: 23 | |
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