Blar i Brage IMR på emneord "echo sounder"
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Cylindrical sonar design for fish echo surveying
(ICES CM Documents;1988/B:3, Working paper, 1988)Most applications of echo integration involve use of a fixed single-beam transducer that is rather narrow and downwards-oriented. It is often desired to sense fish in other directions, for example, to assess components ... -
Detailed in situ target strength measurements of 0-group cod
(ICES CM Documents;1994/B:30, Working paper, 1994)Target strength measurements in situ of cod fry have been made using 38 and 120 kHz split beam echo sounders. Two data sets are sampled in essentially pure, evenly sized, cod concentrations, one in a Ullsfjord, Northern ... -
Digital representation of split-beam-transducer beam patterns
(ICES CM Documents;1986/B:2, Working paper, 1986)The farfield beam pattern of each of two different split-beam transducers is computed and represented in the axial region by a finite number of constant levels. The accuracy of representation is determined as a function ... -
Directional properties of an 18-kHz transducer
(ICES CM Documents;1993/B:29, Working paper, 1993)Several theoretical measures of directivity are given for an 18-kHz transducer that is used in both single-beam and split-beam applications, namely the SIMRAD transducer type 18-11 in the single-beam variant. These are ... -
Distribution of herring (Clupea harengus) and zooplankton in the Norwegian Sea, as determined from generalised additive models
(ICES CM documents, Working paper, 2005)We analyse the variability in the distribution and feeding of the Norwegian spring-spawning herring in the period from 1995 to 2004, using survey data collected throughout the Norwegian Sea each year in May - June. The ... -
Diurnal variation in frequency response of gadoids in the Barents Sea
(ICES CM documents, Working paper, 2006)Earlier studies have demonstrated substantial diurnal variation in acoustic abundance of fish. Both the level and the uncertainty of abundance estimates from surveys carried out around the clock are affected. It has been ... -
Effect of missing modes on calibration sphere target strengths
(ICES CM Documents;1996/B:37, Working paper, 1996)It has been suggested that modes of vibration of solid elastic spheres, such as those used in the calibration of echo sounder systems, can be affected by the manner of suspension. This hypothesis is investigated in the ... -
En korreksjon til ekkoloddets dybdeangivelse
(Fisken og havet;1964 - Nr. 3, Research report, 1964)An echo sounder is adjusted for constant sound velocity, usually 1500 m/sec. Since the velocity of sound in the sea is varying with temperature, salinity and depth, a correction is necessary if accurate soundings are ... -
Estimating tail-beat frequency using split-beam echosounders
(Journal article; Peer reviewed, 2009-02-04)Data from a standard split-beam echosounder are used to estimate tail-beat frequency within a dense herring (Clupea harengus L.) layer. The data were collected by lowering a horizontally projecting 38 kHz split-beam ... -
Estimating tail-beat frequency using split-beam echosounders
(Journal article; Peer reviewed, 2009-02-04)Data from a standard split-beam echosounder are used to estimate tail-beat frequency within a dense herring (Clupea harengus L.) layer. The data were collected by lowering a horizontally projecting 38 kHz split-beam ... -
Experiences using the ES-400, split-beam echo sounder, with special reference to the single-fish recognition criterion
(ICES CM Documents;1986/B:38, Working paper, 1986)Realistic estimates of in situ target strength can be made when the fish concentrations are acoustically resolved into single individuals. In the split-beam echo sounder, as in all other systems available for in situ ... -
Fish target strengths for use in echo integrator surveys
(Journal article; Peer reviewed, 1987)In situ measurements of fish target strength are selected for use in echo integrator surveys at 38 kHz. The results are expressed through equations in which the mean target strength TS is regressed on the mean fish length ... -
Haddock avoidance reactions during trawling
(ICES CM Documents;1986/B:36, Working paper, 1986)Fish reaction to the whole trawling operation was studied using a stationary echo sounder-system observing the fish in front of the vessel and during trawl passage. Strong avoidance reactions were observed on haddock, ... -
Herring tilt angles, measured through target tracking
(Report / Alaska Sea Grant College Program, Chapter, 2001)The target strength of herring in captivity was monitored experimentally at three frequencies (18, 38, and 120 kHz) over a period of 3 years using split-beam echo sounders. One of the fundamental parameters of a target ... -
In situ target strength observations on haddock
(ICES CM Documents;1986/B:39, Working paper, 1986)In situ target strength measurements of ideally resolved haddock have been made using the ES-400 split-beam echo sounder. The measurements are compared with the mean target strength obtained simultaneously by counting ... -
Influence of Different Factors on Abundance Estimates Obtained from Simultaneous Sonar and Echo Sounder Recordings
(Journal article; Peer reviewed, 2011-12-28)Use of horizontal guided sonar in addition to vertical echo sounder may improve biomass estimation of pelagic fish schooling near the surface. But proportions of horizontal guided sonar to vertical echo integration estimates ... -
Kan måle fiskestørrelse før fangsting
(Havforskningsnytt;Nr. 6-2016, Working paper, 2016)