Consulta: subjectFacets:"Acoustics"
Registros recuperados: 25
Data/hora: 01/06/2024 04:55:28

Validação da bioacústica como alternativa à avaliação visual para monitoramento do comportamento ingestivo de bovinos em pastagens.
Provedor de dados: 14
Autores: VOLPI, D.; ALVES, F. V.; SARAIVA, E. F.; VIGAS, V. P.; ARGUELHO, A. da S.; ZOPOLLATTO, M.; ALMEIDA, R. G. de.
A observação visual do comportamento ingestivo em ruminantes, principalmente naqueles mantidos em pastagens, apesar de comumente utilizada com diferentes finalidades de estudo, é trabalhosa, pouca precisa e empenha grande quantidade de mão-de-obra. Com o avanço da tecnologia em geral, outras metodologias, que fazem uso de sensores mecânicos, ópticos e sonoros, mostram grande potencial de uso em ruminantes. A bioacústica, em particular, adequa-se em experimentos que necessitam tanto de macro quanto de microatividades, otimizando mão-de-obra e com custo relativamente baixo em comparação à outras metodologias automatizadas. Entretanto, por ser um campo de estudo recente na produção animal, as operações de captura e análise dos sons ainda precisam ser...
Tipo: Documentos (INFOTECA-E)
Palavras-chave: Acústica; Pecuária de precisão; Som; Feeding; Well-being; Precision livestock; Comportamento Animal; Gado Nelore; Nutrição Animal; Pastejo; Pecuária; Ruminante; Alimentação; Bem-Estar; Acoustics; Animal well-being; Grazing; Ruminants; Sounds.
Ano: 2018
URL: http://www.infoteca.cnptia.embrapa.br/infoteca/handle/doc/1102352

Fluid emissions at the Aquitaine Shelf (Bay of Biscay, France): A biogenic origin or the expression of hydrocarbon leakage?
Provedor de dados: 5
Autores: 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

A method for controlled target strength measurements of pelagic fish, with application to European anchovy (     Engraulis encrasicolus     )
Provedor de dados: 5
Autores: 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

Joint use of echosounding, fishing and video techniques to assess the structure of fish aggregations around moored Fish Aggregating Devices in Martinique (Lesser Antilles)
Provedor de dados: 5
Autores: 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

Seafloor habitat definition for spatial management in fisheries: a case study on the continental shelf of southeast Australia
Provedor de dados: 5
Autores: Bax, N; Kloser, R; Williams, A; Gowlett-holmes, K; Ryan, T.
The importance of habitat to Fisheries production on Australia's southeast continental shelf is part of a five-year study of ecosystem functioning and its implications for a sustainable fishery. Benthic habitats from 40 m to similar to 200 m were studied, based on identification of suitable sites from local fishers' information. Results presented here concentrate on data from a single mesohabitat at 40-60 m depth collected over two days. Macrohabitats within this mesohabitat were discriminated as soft, hard and rough from visual inspection of acoustic echograms. Subsequent analysis of the return echoes using roughness and hardness indices did not significantly improve real-time visual discriminations. Macrohabitats were sampled with an underwater video...
Tipo: Text
Palavras-chave: Habitat benthique; Acoustique; Communauté biologique; Vidéo sous-marine; Gestion spatiale; Seafloor habitat; Acoustics; Biological communities; Underwater video; Spatial management.
Ano: 1999
URL: http://archimer.ifremer.fr/doc/00325/43594/44035.pdf

Observing the ocean interior in support of integrated management
Provedor de dados: 5
Autores: Trenkel, Verena; Handegard, Nils Olav; Weber, Thomas C.
Active- and passive-acoustic methods are widely used tools for observing, monitoring, and understanding marine ecosystems. From 25 to 28 May 2015, 214 scientists from 31 nations gathered for an ICES symposium on Marine Ecosystem Acoustics (SoME Acoustics) to discuss three major themes related to acoustic observations of marine ecosystems: (i) recent developments in acoustic and platform technologies; (ii) acoustic characterisation of aquatic organisms, ecosystem structure, and ecosystem processes; and (iii) contribution of acoustics to integrated ecosystem assessments and management. The development of, and access to new instruments, such as broad bandwidth systems, enables insightful ecological studies and innovative management approaches. Unresolved...
Tipo: Text
Palavras-chave: Acoustics; Broadband; Multi-frequency; Passive and active acoustics; Ecosystem approach to management; Ecosystem monitoring; Pelagic ecosystem; Echosounder; Sonar.
Ano: 2016
URL: http://archimer.ifremer.fr/doc/00347/45820/45921.pdf

Towards an Autonomous Pelagic Observatory: Experiences from Monitoring Fish Communities around Drifting FADs
Provedor de dados: 5
Autores: Brehmer, Patrice; Sancho, Gorka; Trygonis, Vasilis; Itano, David; Dalen, John; Fuchs, Ariel; Faraj, Abdelmalek; Taquet, Marc.
This work presents a methodological synthesis for the in situ monitoring of fish aggregating devices (FADs) using a combination of optical, echosounder and SCUBA observations conducted in the vicinity of drifting FADs. The acoustic methods allowed, according to the devices used, the description of the spatial organisation and dynamics of biotic scattering layers, individual fishes, schools, shoals and mammals, while visual, photographic and video observations permitted species identification within a range of 0 to ~ 25 m. Based on these results, we elaborate on the interest to combine acoustic and visual methods, and present an autonomous instrumented drifting buoy for remotely monitoring fish diversity and abundance in the pelagic ecosystems. The...
Tipo: Text
Palavras-chave: Optical; Census; Acoustics; Buoy; Seaorbiter; Biomonitoring; Conservation; Environmental monitoring; Fish; Pelagic.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00461/57252/59265.pdf

Change in the shoaling behaviour and nutritional condition of anchovies (Engraulis encrasicolus L.) during a wind-induced water column disturbance: a natural event test of a general hypothesis
Provedor de dados: 5
Autores: Bergeron, Jean-pierre; Masse, Jacques.
Fishermen have long observed the sudden change of shoaling behaviour of small pelagic fish following a strong wind event. The phenomenon was thereafter confirmed by fisheries scientists using acoustic tools. In this study, we report our observations made with acoustics to measure disorganization of the previously observed spatial distribution and shape of shoals that occurred after a wind event. The measurements were made during a fisheries research cruise in the Bay of Biscay (NE Atlantic) aimed at determining i) small pelagic fish species abundance and ii) the individual nutritional state of anchovies (Engraulis encrasicolus L.) via evaluation of their RNA/DNA ratio. A spatial fine-scale study was conducted in two of the main breeding areas for anchovy,...
Tipo: Text
Palavras-chave: Engraulis encrasicolus L.; Anchovy; Behaviour; Acoustics; Bay of Biscay; Nutritional condition; RNA/DNA ratio.
Ano: 2011
URL: http://archimer.ifremer.fr/doc/00033/14473/11782.pdf

Spatial and temporal variability of zooplankton off New Caledonia (Southwestern Pacific) from acoustics and net measurements
Provedor de dados: 5
Autores: Smeti, Houssem; Pagano, Marc; Menkes, Christophe; Lebourges-dhaussy, Anne; Hunt, Brian P. V.; Allain, Valerie; Rodier, Martine; De Boissieu, Florian; Kestenare, Elodie; Sammari, Cherif.
Spatial and temporal distribution of zooplankton off New Caledonia in the eastern Coral Sea was studied during two multidisciplinary cruises in 2011, during the cool and the hot seasons. Acoustic measurements of zooplankton were made using a shipborne acoustic Doppler current profiler (S-ADCP), a scientific echosounder and a Tracor acoustic profiling system (TAPS). Relative backscatter from ADCP was converted to biomass estimates using zooplankton weights from net-samples collected during the cruises. Zooplankton biomass was estimated using four methods: weighing, digital imaging (ZooScan), ADCP and TAPS. Significant correlations were found between the different biomass estimators and between the backscatters of the ADCP and the echosounder. There was a...
Tipo: Text
Palavras-chave: South Pacific; Acoustics; Zooplankton; Vertical migration; Water masses; Mesoscale dynamics.
Ano: 2015
URL: https://archimer.ifremer.fr/doc/00297/40809/39836.pdf

Cartographie sous-marine: Etat de l'art et problemes
Provedor de dados: 5
Autores: Renard, V.
The side looking sonars have been developed for greater swath coverage, digital processing of the signals has improved the quality of the images and interferometric techniques have been used to determine the depth of the bottom features. A review of the systems existing today is presented. Documents such as graphs, block diagrams, images, maps, sections, created from data acquired at sea level suffer from a filtering or smoothing effect that restricts the representativity of the measured parameters and therefore limits their interpretation. The greater the depth of the seafloor, the greater the filtering. It is due not only to the nature of the measured phenomenon but also the characteristics of the sensors, to their operation and to the data processing....
Tipo: Text
Palavras-chave: Bathymetry; Cartography; Sensors; Echosounders; Acoustic imagery; Acoustics; Ocean floor; Seafloor mapping.
Ano: 1990
URL: http://archimer.ifremer.fr/doc/1990/acte-1147.pdf

Micronekton distributions and assemblages at two shallow seamounts of the south-western Indian Ocean: Insights from acoustics and mesopelagic trawl data
Provedor de dados: 5
Autores: Annasawmy, Pavanee; Ternon, Jean-francois; Cotel, Pascal; Cherel, Yves; Romanov, Evgeny V.; Roudaut, Gildas; Lebourges-dhaussy, Anne; Ménard, Fréderic; Marsac, Francis.
Micronekton distributions and assemblages were investigated at two shallow seamounts of the south-western Indian Ocean using a combination of trawl data and multi-frequency acoustic visualisation techniques. La Pérouse (∼60 m) seamount is located on the outskirts of the oligotrophic Indian South Subtropical Gyre province with weak mesoscale activities and low primary productivity all year round. The “MAD-Ridge” seamount (thus termed in this study; ∼240 m) is located in the productive East African Coastal (EAFR) province with high mesoscale activities to the south of Madagascar. This resulted in higher micronekton species richness at MAD-Ridge compared to La Pérouse. Resulting productivity at MAD-Ridge seamount was likely due to the action of mesoscale...
Tipo: Text
Palavras-chave: Micronekton; Seamount; South-western Indian Ocean; Acoustics; Seamount-associated fauna.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00510/62135/66368.pdf

Acoustic characterisation of pelagic fish aggregations around moored fish aggregating devices in Martinique (Lesser Antilles)
Provedor de dados: 5
Autores: Doray, Mathieu; Josse, Erwan; Gervain, Paul; Reynal, Lionel; Chantrel, Josselin.
Sea cruises were conducted for 57 days over 16 months to characterise pelagic fish aggregations around 2 moored fish aggregating devices (FADs) in Martinique (Lesser Antilles). Echosounder surveys run in a star pattern were used in conjunction with obliquely beamed sonar observations. An echo-integration-by-shoal algorithm was implemented to isolate pelagic fish shoals from sound scattering layers and to compute mean morphometric, positional and density parameters. Tree regressions were used to select and classify pelagic fish Target Strengths (TS), with reference to their spatial and temporal characteristics. The main type of pelagic fish aggregation was a large sub-surface aggregation. It was observed during all daytime periods within a radius of 400 m...
Tipo: Text
Palavras-chave: Lesser Antilles; Tuna; Large pelagic fish; Aggregative behaviour; Shoal density; Target Strength; Acoustics; Fish Aggregating Device.
Ano: 2006
URL: http://archimer.ifremer.fr/doc/2006/publication-1734.pdf

Methodological developments for improved bottom detection with the ME70 multibeam echosounder
Provedor de dados: 5
Autores: 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

Application du laser a la detection sous-marine: Experimentation d'un imageur
Provedor de dados: 5
Autores: Kervern, G; Legall, A.
Nowadays, side-looking sonar is the only equipment able to carry out long-range underwater imaging. The use of optics is limited to short-range identification by means of conventional video-cameras. However, active optical systems (lidars) manufacturing, using a blue-green laser, will enable optics to hold its place in the field of long-range underwater imaging. After a short comparison between acoustics and optics in underwater detection and a description of the proper features of underwater optical propagation, we present the different conceivable imaging principles and propose a method to determine their performances. The experimentations described concern a lidar imager mock-up using one of the imaging principles proposed. The pictures obtained deal...
Tipo: Text
Palavras-chave: Optics; Lasers; Detection; Acoustics; Underwater cameras; Sonar imagery; Imaging techniques; Underwater photography; Marine technology; Side scan sonar.
Ano: 1990
URL: http://archimer.ifremer.fr/doc/1990/acte-1139.pdf

Glider-Based Active Acoustic Monitoring of Currents and Turbidity in the Coastal Zone
Provedor de dados: 5
Autores: Gentil, Mathieu; Many, Gaël; Durrieu De Madron, Xavier; Cauchy, Pierre; Pairaud, Ivane; Testor, Pierre; Verney, Romaric; Bourrin, François.
The recent integration of Acoustic Doppler Current Profilers (ADCPs) onto underwater gliders changes the way current and sediment dynamics in the coastal zone can be monitored. Their endurance and ability to measure in all weather conditions increases the probability of capturing sporadic meteorological events, such as storms and floods, which are key elements of sediment dynamics. We used a Slocum glider equipped with a CTD (Conductivity, Temperature, Depth), an optical payload, and an RDI 600 kHz phased array ADCP. Two deployments were carried out during two contrasting periods of the year in the Rhone River region of freshwater influence (ROFI). Coastal absolute currents were reconstructed using the shear method and bottom tracking measurements, and...
Tipo: Text
Palavras-chave: Glider; Optics; Acoustics; Satellite; Coastal hydrodynamics; Suspended particulate matter; Particulate fluxes; Gulf of Lions; Mediterranean.
Ano: 2020
URL: https://archimer.ifremer.fr/doc/00648/76039/76962.pdf

A fisheries acoustic multi-frequency indicator to inform on large scale spatial patterns of aquatic pelagic ecosystems
Provedor de dados: 5
Autores: 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

Estimation de la précision des campagnes acoustiques au Sénégal par la méthode géostatistique transitive à une dimension
Provedor de dados: 5
Autores: Samb, Birame; Petitgas, Pierre.
This study presents an application of the geostatistical one-dimensional (1D) transitive method for estimating the precision of acoustic pelagic abundance estimates in Senegal. In applying the method, the major problem encountered was how to take into account the temporal variability in the computation of the estimation variance. In acoustic surveys, echointegration is performed continuously along the ship's sailing track. For a survey design made of parallel transects, each transect can thus be considered as a sampling unit. By summing the density values along the transects to obtain biomass values per transect, the 2D estimation is simply reduced to a 1D estimation procedure. If the transects are equidistant, the geostatistical transitive method applied...
Tipo: Text
Palavras-chave: Céostatistique; Variance; Acoustique; Abondance; Geostatistics; Variance; Acoustics; Abundance.
Ano: 1997
URL: http://archimer.ifremer.fr/doc/00188/29883/28348.pdf

Noise generation in the solid Earth, oceans and atmosphere, from nonlinear interacting surface gravity waves in finite depth
Provedor de dados: 5
Autores: Ardhuin, Fabrice; Herbers, T. H. C.
Oceanic pressure measurements, even in very deep water, and atmospheric pressure or seismic records, from anywhere on Earth, contain noise with dominant periods between 3 and 10 s, which is believed to be excited by ocean surface gravity waves. Most of this noise is explained by a nonlinear wave-wave interaction mechanism, and takes the form of surface gravity waves, acoustic or seismic waves. Previous theoretical work on seismic noise focused on surface (Rayleigh) waves, and did not consider finite-depth effects on the generating wave kinematics. These finite-depth effects are introduced here, which requires the consideration of the direct wave-induced pressure at the ocean bottom, a contribution previously overlooked in the context of seismic noise. That...
Tipo: Text
Palavras-chave: Acoustics; Geophysical and geological flows; Surface gravity waves.
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00125/23580/21479.pdf

Controle commande d'un robot sousmarin
Provedor de dados: 5
Autores: Durand, D; Domingo, J; Levallois, E.
This system is composed of a high accuracy hydraulic manipulator arm with 6 degrees of freedom, for high loads (2000 daN), using ultrasound proximetry and contact force measurement data to carry out the subsea connection of bottom oil wells. An expert system controls the connection phases and generates the sequences of commands to be executed by the robot. The safety systems and failure modes are also taken into account. A graphic operator station provides easy control. Each connection phase generates a graphic representation of the robot status and all the proprioceptive and exteroceptive sensors. The control/command system, although it is designed to carry out a subsea connection by means of a manipulator arm, can be adapted to any type of process. For...
Tipo: Text
Palavras-chave: Marine technology; Acoustics; Connecting; Connectors; Oil wells; Sensors; Hydraulics; Robots; Manipulators.
Ano: 1990
URL: http://archimer.ifremer.fr/doc/1990/acte-1155.pdf

Analyse des risques pour les mammifères marins liés à l'emploi des méthodes acoustiques en océanographie
Provedor de dados: 5
Autores: Lurton, Xavier; Antoine, Loic.
The use of acoustical systems in various human activities in the ocean (industry, defence, science) raises the issue of their impact upon marine mammals populations. Several serious accidents linked to the use of naval sonars led the military, industrial and scientific communities to investigate the potential dangers of their own activity.    This report aims at identifying the risks for the cetaceans linked to the use of acoustic and seismic systems currently used for oceanographic science. The analysis proposed here stays within the frame of bibliography synthesis and elementary modelling, and brings no new scientific elements on the topic. An overview of the status of cetacean populations is given first, with a summary of the possible acoustical...
Tipo: Text
Palavras-chave: Seismics; Sonar; Acoustics; Oceanography; Acoustical methods; Auditory threshold; Stranding; Acoustical risks; Marine mammals.
Ano: 2007
URL: http://archimer.ifremer.fr/doc/2007/rapport-2390.pdf

The new fisheries multibeam echosounder ME70: description and expected contribution to fisheries research
Provedor de dados: 5
Autores: 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

Combining acoustic and CUFES data for the quality control of fish-stock survey estimates
Provedor de dados: 5
Autores: Petitgas, Pierre; Goarant, Anne; Masse, Jacques; Bourriau, Paul.
Petitgas, P., Goarant, A., Masse, J., and Bourriau, P. 2009. Combining acoustic and CUFES data for the quality control of fish-stock survey estimates. - ICES Journal of Marine Science, 66: 1384-1390.
Tipo: Text
Palavras-chave: CUFES; Biscay; Bias; Anchovy; Acoustics; Abundance.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/publication-6566.pdf

A method for reducing uncertainty in estimates of fish-school frequency response using data from multifrequency and multibeam echosounders
Provedor de dados: 5
Autores: Berger, Laurent; Poncelet, Cyrille; Trenkel, Verena.
Fish schools can be insonified simultaneously with multifrequency echosounders (e.g. Simrad EK60s) and a multibeam echosounder (e.g. Simrad ME70). This paper presents a method for combining these data to improve estimates of the relative frequency response r(f) of fish schools. Values of r(f) are now commonly used to classify echoes in fishery surveys. The data from the roll- and pitch-stabilized, high-resolution ME70 are used to correct beam-width effects in the multifrequency EK60 data. First, knowing the exact position and orientation of the transducers and the position of the vessel, the echoes are placed into a common geographic coordinate system. Then, the EK60 data are rejected if they do not include a significant percentage of the fish school...
Tipo: Text
Palavras-chave: Species identification; Scomber scombrus; Sardina pilchardus; Pelagic fish; Acoustics.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/publication-6590.pdf

A transboundary study of the pelagic fish stocks of southern
Provedor de dados: 20
Autores: Krakstad, Jens-Otto; Amaro, Aristóteles P. da S.; Shigwedha, Vaino.
The main objectives of the survey were the following: • To map the distribution and estimate the abundance of the most commercially important pelagic species in the Namibia-Angola transboundary area (15°50-19°00’), following the survey design utilized in Angolan waters (6 n.mi spacing between transect lines), with special emphasis on the two horse mackerel Cunene horse mackerel (Trachurus trecae) and Cape horse mackerel (Trachurus capensis), sardine “Pilchard” (Sardinops sagax) and other small pelagic species, including anchovy (Engraulis capensis) and round herring (Etrumeus whiteheadi). • To map the distributions and estimate the abundance of the same species in central Namibia south to Dune Point (20°15’ S), following the established survey design with...
Tipo: Report
Palavras-chave: Pelagic fisheries; Fishery surveys; Acoustics; Sampling; Trawls; Oceanography; Biomass; Distribution; Composition.
Ano: 2012
URL: http://hdl.handle.net/1834/5230

Lettre IMROP
Provedor de dados: 20
Autores: IMROP.
Tipo: Other
Palavras-chave: Sélaciens; Requins; Sharks; Camapgnes acoustiques; Acoustic serveys; Cetacian monitoring; Acoustics.
Ano: 2006
URL: http://hdl.handle.net/1834/1508