Consulta: subjectFacets:"Target strength"
Registros recuperados: 8
Data/hora: 09/06/2024 08:29:47

Diel changes in acoustic and catch estimates of krill biomass
Provedor de dados: 5
Autores: Simard, Yvan; Sourisseau, Marc.
Krill-biomass estimates can be compromised by diel variabilities in acoustic backscatter and the catch efficiencies of various nets. This paper describes an effort to quantify these variabilities at fine temporal and spatial scales during a three-day experiment at a fixed location, using high-resolution, stratified Bioness samples and echo-integration, and assuming a fixed distribution of krill orientations. Night-time catches in the krill scattering layer (SL) were 15 times the acoustic estimates. The situation was reversed during daytime, when the acoustic estimates in the SL were 5 times larger than the catches. This collectively resulted in a ±10-dB gradual diel cycle in the difference of vertically integrated biomass from both sampling methods. Use of...
Tipo: Text
Palavras-chave: Thysanoessa raschi; Target strength; Strobe light; St Lawrence Estuary; Meganyctiphanes norvegica; Krill; In situ orientation; Feeding; Diel vertical migration; Avoidance.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/publication-6591.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

Acoustic backscattering from salp and target strength estimation
Provedor de dados: 5
Autores: David, P; Guerin-ancey, O; Oudot, G; Van Cuyck, Jp.
Although zooplanktonic organisms nearly have the acoustical impedance of water, they backscatter the sound. Strong acoustical echoes from salps were recorded in the Weddell sea at 150 kHz (1992), in the Indian ocean at 12 kHz (1994) and in the Mediterranean at 120 and 38 kHz (1996). Sphere and cylinder models were applied to estimate the salp target strength. The salp is modelled by a cylindrical gelatinous body (length L) and a spherical nucleus (radius a). Backscattering from each part was estimated individually. With a detection threshold of -100 dB, the minimum body length and the minimum radius of nucleus to be theoretically detected were estimated for each of the following frequencies: 12, 38, 120 and 150 kHz. A small salp (L = 14 rum and a = I mm)...
Tipo: Text
Palavras-chave: Salpe; Target strength; Acoustique sous-marine; Salp; Target strength; Underwater acoustics.
Ano: 2001
URL: http://archimer.ifremer.fr/doc/00322/43341/42886.pdf

Acoustic surveys on the southern blue whiting (Micromesistius australis).
Provedor de dados: 20
Autores: Madirolas, A.
Two joint Argentine-British acoustic surveys specifically targeted on the southern blue whiting (Micromesistius australis) were carried out during September 1994 and 1995. The surveys confirmed the existence of a spawning concentration area located south from San Carlos Strait, in waters south of Malvinas Islands, ASW. The obtained point estimates of blue whiting abundance were 84801 t for the 1994 survey and 140953 t for the 1995 survey. The surveys also provided information on the school structure and behavior as well as some clues about the complex migration pattern of the species.
Tipo: Journal Contribution
Palavras-chave: Fishery surveys; Echo surveys; Biomass; Geographical distribution; Target strength; Biomass; Geographical distribution; Http://aims.fao.org/aos/agrovoc/c_926; Http://aims.fao.org/aos/agrovoc/c_5083.
Ano: 1999
URL: http://hdl.handle.net/1834/2567

Estimaciones in situ de la fuerza de blanco (TS) de la merluza de tres aletas
Provedor de dados: 20
Autores: Lillo, S.; Bahamonde, R.; Cancino, C.; Saavedra, J.; Saavedra, A.; Flores, F.
En el presente informe se entregan los resultados del proyecto FIP 2005-29, cuyo objetivo general es estimar mediante métodos in situ, la fuerza de blanco de la especie merluza de tres aletas (Micromesistius australis). El enfoque metodológico propuesto consideró dos formas para la estimación de la fuerza de blanco. El primero correspondió al método de estimación de TS in situ, en el cual las mediciones acústicas se realizan con los peces en su ambiente natural y en el que la identificación de las especies como la estructura de tamaños de los peces insonificados se obtiene mediante lances de pesca y el segundo método ex situ basado en la morfometría de la vejiga.
Tipo: Report
Palavras-chave: Target strength; Echo surveys.
Ano: 2007
URL: http://hdl.handle.net/1834/1854

Acoustic surveys on the southern blue whiting (Micromesistius australis).
Provedor de dados: 20
Autores: Madirolas, A.
Two joint Argentine-British acoustic surveys specifically targeted on the southern blue whiting (Micromesistius australis) were carried out during September 1994 and 1995. The surveys confirmed the existence of a spawning concentration area located south from San Carlos Strait, in waters south of Malvinas Islands, ASW. The obtained point estimates of blue whiting abundance were 84801 t for the 1994 survey and 140953 t for the 1995 survey. The surveys also provided information on the school structure and behavior as well as some clues about the complex migration pattern of the species.
Tipo: Journal Contribution
Palavras-chave: Fishery surveys; Echo surveys; Biomass; Geographical distribution; Target strength; Biomass; Geographical distribution.
Ano: 1999
URL: http://hdl.handle.net/1834/2567

Medición de la fuerza del blanco acústico de dos especies de peces marinos de las familias Lutjanidae y Haemulidae (pargo criollo, Lutjanus analis y ronco amarillo, Haemulon sciurus)
Provedor de dados: 20
Autores: Linares, E.O.; Caballero, P.I.; Guillard, J.; Sierra, L.; Hernández, J.L.
Se presentan los resultados de las ecuaciones acústicas de TS (Fuerza del Blanco acústico) en su aspecto dorsal de dos especies de peces de interés comercial (pargo criollo, Lutjanus analis y ronco amarillo, Haemulon sciurus) del Golfo de Batabanó, Cuba. Los trabajos se ejecutaron en Puerto Esperanza (Provincia de Pinar del Río) y zonas cercanas a Xcalak, península de Yucatán (México) en lugares de aguas claras y poco profundas con poca corriente, empleando métodos hidroacústicos. Para realizar las mediciones se utilizó una ecosonda de Doble Haz DT 5000 BIOSONICS, con transductor digital y frecuencia de 129 Khz. La profundidad a que se midieron los peces fue de 3 m. La ecuación obtenida para el ronco amarillo es TS(db) =21.9 log L(cm)– 69.2, para un r...
Tipo: Journal Contribution
Palavras-chave: Echosounders; Target strength.
Ano: 2009
URL: http://hdl.handle.net/1834/3392

Estimaciones in situ de la fuerza de blanco (TS) de merluza del sur y merluza de cola
Provedor de dados: 20
Autores: Lillo, S.; Barbieri, M.A.; Espejo, M.; Castillo, J.; Miranda, H.; Córdova, J.; Saavedra, A.; Rojas, M.; Cancino, C.; Flores, F.; Reyes, H.
En el presente informe se entregan los resultados finales del proyecto FIP 2003-34, cuyo objetivo general fue estimar mediante métodos in situ, la fuerza de blanco de las especies merluza del sur y merluza de cola (Merluccius australis y Macruronus magellanicus). En primer lugar durante el desarrollo del proyecto, se debió proponer un enfoque metodológico dirigido a efectuar las mediciones de fuerza de blanco considerando las características del recurso y los medios tecnológicos disponibles. En segundo término, se procedió a definir un sistema acústico a emplear para lo cual se analizaron diferentes alternativas, seleccionándose un sistema compuesto de un transductor de profundidad que era desplegado en las profundidades de distribución de los recursos...
Tipo: Report
Palavras-chave: Stock assessment; Acoustic equipment; Echo surveys; Target strength; Stock assessment; Http://aims.fao.org/aos/agrovoc/c_24251.
Ano: 2005
URL: http://hdl.handle.net/1834/1812