Blar i ICES CM documents authored by IMR scientists (1949-2011) på emneord "acoustics"
Viser treff 21-40 av 221
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Acoustic estimates of saithe in the North Sea in 1984 and 1985
(ICES CM Documents;1985/G:14, Working paper, 1985)This paper describes the results from a joint cruise in July 1984 with two vessels, and the results from two cruises in February - March 1985. In July the saithe were standing well above the bottom, but the saithe were ... -
Acoustic estimates of saithe in the North Sea in 1985 and 1986
(ICES CM Documents;1986/G:49, Working paper, 1986)This paper describes the results from a joint cruise in July 1985 with two vessels, and the results from one cruise in February 1986. The acoustic estimates agree fairly well with the estimates made by the North Sea ... -
Acoustic estimates of spawning cod off Lofoten and Møre in 1985
(ICES CM Documents;1985/G:66, Working paper, 1985)The annual surveys on the spawning stock of North-east Arctic cod were carried out in the Lofoten and Møre areas in March- April 1985. These surveys were undertaken to estimate the size and age structure of the spawning ... -
Acoustic extinction in dense herring layers, measured from a bottom-mounted transducer
(ICES CM documents, Working paper, 2006)Herring is often found in dense aggregations or schools, and acoustic shadowing is thus a problem in acoustic survey estimates. Knowledge of the attenuated echo intensity in herring aggregations is essential for correcting ... -
Acoustic investigation of fish behaviour apropos avoidance reaction
(ICES CM Documents;1981/B:21, Working paper, 1981) -
Acoustic measurements of schooling herring. Estimation of school biomass and target strength
(ICES CM Documents;1988/B:26, Working paper, 1988)The connections between reflected echo energy and dimensions of fatty herring schools were studied by a combination of multibeam sonar and a calibrated echo integration unit. A relation between the area and the biomass ... -
Acoustic portrait of herring in Vestfjord, january 1996, with geostatistical analysis
(ICES CM Documents;1996/H:31, Working paper, 1996)In January 1996 the stock of Norwegian spring-spawning herring (Clupea harengus) was acoustically surveyed in the wintering area. Both immature and mature fish were present. Because of the comparative lateness of the ... -
Acoustic properties of Salpa thompsoni.
(ICES CM documents;2009 / I:01, Working paper, 2009)Salps are common members of the world oceans planktonic community (Madin, et.al., 2006). In the southern ocean, both krill (Euphausia superba) and salps (Salpa thompsoni) can occur in dense aggregations (Loeb et al, 2009, ... -
Acoustic sampling volume versus equivalent beam angle
(ICES CM Documents;1988/B:5, Working paper, 1988)Irnprovements in target strength measurement have shown the equivalent beam angle (EBA) to be a worrisome source of error in echo integrator surveys. The reason is that the EBA is generally defined as a purely physical ... -
Acoustic survey of deep-water fish of the Skagerrak
(ICES CM Documents;1992/H:15, Working paper, 1992)Introduction: Two fish species, the greater silver smelt Argentina silus and the roundnose grenadier Coryphaenoides rupestris, are highly abundant in the deep-water areas of the Skagerrak. Since the 1970s, a small aimed ... -
Acoustic survey on blue whiting in the Norwegian Sea, August / September 1985
(ICES CM Documents;1985/H:4, Working paper, 1985)Seven research vessels from USSR, Norway, GDR, Iceland and the Faroes participated in the fourth ICES-coordinated acoustic survey on blue whiting in the Norwegian Sea and adjacent waters. Blue whiting were recorded over ... -
An acoustic survey on 0-group gadoids in the northern North Sea and the Shetland-Orkney area, July 1984
(ICES CM Documents;1985/G:17, Working paper, 1985)An acoustic survey was carried out by two research vessels in July 1984 to assess the distribution and abundance of 0-group gadoids. The 0-groups were distributed in scattering layers by night and in schools by day. ... -
Analysis of spatial variability of Georges Bank haddock (Melanogrammus aeglefinus) from trawl survey data using a linear regression model with spatial interaction
(ICES CM Documents;1990/D:36, Working paper, 1990)A regression model with spatially autocorrelated errors is used to test if there is systematic spatial variation across the study area in haddock catch per tow data from the NEFC annual fall survey from 1963 - 1987. A ... -
Assigning values of target strength and equivalent beam angle in acoustic surveys of fish
(ICES CM Documents;1991/B:34, Working paper, 1991)Contrary to popular opinion, the equivalent beam angle (~) is not determined solely by the transducer directivity. Rather, like the target strength TS, it also depends on the scattering properties of the target fish, but ... -
Automatic recording of fish heart rate on a personal computer
(ICES CM Documents;1988/B:34, Working paper, 1988)From acoustic tags operated into fish in a closed system, the heartbeat signals are sent via underwater telemetry and counted on a personal computer. The computer removes false pulses caused by noise, and calculates the ... -
Can subjective evaluation of echograms improve correlation between bottom trawl and acoustic densities?
(ICES CM documents, Working paper, 2004)Direct comparison of acoustic densities and trawl catches involves fundamental difficulties related to species and size selectivity of the trawl and efficiency of the acoustic instrumentation. In some surveys, therefore, ... -
Changes in acoustic abundance - a signal indicatior for stock dynamics for cod (Gadus morhua)
(ICES CM documents, Working paper, 1999)To be able to take the proper and timely management actions, it is crucial to reliably defect major changes in trends of fish stock abundance. For the assessment of Northeast Arctic cod, the Norwegian bottom trawl survey ... -
Combined algorithms for detection of acoustic categories
(ICES CM Documents;2004/R:38, Working paper, 2004)There is a current desire to harvest marine resources by managing total marine ecosystems rather than single species of the ecosystems. By means of algorithms applied on high-quality multi-frequency acoustic data, species, ... -
Comparison between "underway" and "on station" acoustic measurements made during bottom trawl surveys
(ICES CM Documents;2002/J:3, Working paper, 2002)It becomes in many cases, routine, to collect acoustic data during bottom trawl surveys, both during and between trawls providing “on station” and “underway” acoustic data. Still, the combination of trawl and acoustic data ... -
Comparison of equal-area cylindrical and circular piston transducers
(ICES CM Documents;1994/L:29, Working paper, 1994)Design of sondes for in situ measurement of zooplankton or other scatterers requires choosing among alternative transducer geometries. This contribution addresses the problem of choosing between cylindrical and circular ...