Browsing Published in cooperation with others by Subject "acoustics"
Now showing items 41-60 of 221
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Comparison of two 120-kHz split-beam transducers
(ICES CM Documents;1991/B:31, Working paper, 1991)The performance of two 120-kHz split-beam transducers is compared through the following measures: relative power level, directivity index, relative source level, and reverberation index or equivalent beam angle. Sidelobe ... -
Correcting for avoidance in acoustic abundance estimates for herring using a generalized linear model
(ICES CM documents, Working paper, 2006)When a research vessel passes over a herring school or layer, the herring may avoid the vessel by swimming downwards and horizontally. The fish may also change its orientation, which may alter its mean target strength. ... -
Deep towed vehicle for fish abundance estimation concept and testing
(ICES CM Documents;1991/B:53, Working paper, 1991)A research program was initiated in Norway in 1988 for measuring the abundance of fish resources at depth from 500 to 1000 metres. It was decided to develope a deep towed vehicle, to bring acoustic transducers down to ... -
Definition of the problem of estimating fish abundance over an area from acoustic line-transect measurements of density
(ICES CM Documents;1990/D:25, Working paper, 1990)The problem of acoustic abundance estimation is briefly reviewed. Under proper conditions, fish density can be measured with high accuracy along line transects. Observed variations in fish density consequently reflect ... -
Designing an improved transducer array geometry
(ICES CM Documents;1988/B:2, Working paper, 1988)Improvements in a split-beam transducer that is also used for surveying are sought through changes in array geometry. These are assessed through relative changes in the sum of source level and voltage response and the ... -
Designing an Ocean Mid-trophic Automatic Acoustic Sampler (MAAS) - thoughts on how to include echo sounder observatories in ecosystem models
(ICES CM documents;2009/I:21, Working paper, 2009)Echo sounders are a widely used tool for observing marine ecosystems. Traditionally, carefully designed surveys are used to integrate biomass to a global estimate, which is coupled to traditional stock assessment models. ... -
The development of acoustic instrumentation in fisheries research and commercial fisheries in Norway
(ICES CM Documents;1966/F:8, Working paper, 1966) -
Direct measurements of equivalent beam angle on hull-mounted transducers
(ICES CM Documents;1985/B:43, Working paper, 1985)Measurements for checking the equivalent beam angle on a hullmounted transducer have been made on a standard 38-29/25-E SIMRAD transducer on the Norwegian research vessel "ELDJARN". The measurements were made during a ... -
Directional responses in herring to sound and noise stimuli
(ICES CM Documents;1969/B:20, Working paper, 1969) -
Diurnal variation in acoustic densities: why do we se less in the dark?
(ICES CM Documents;2004/R:33, Working paper, 2004)Introduction: In the Barents Sea, the echo abundance of demersal fish is about 50% higher at day than at night. Three possible reasons are: • Fish hide in the bottom dead zone at night. • Fish target strength changes due ... -
Diurnal variations in acoustic density measurements of wintering Norwegian spring spawning herring
(ICES CM Documents;1995/B:12, Working paper, 1995)Survey data from six herring assesment cruises in the wintering areas for spring spawning Norwegian herring were analysed with regard to variation in abundance and depth with time of day. The data were quite consistant ... -
Dynamics of wintering Norwegian spring-spawning herring at the entrance to Tysfjorden, December 1996
(ICES CM Documents;1997/CC:16, Working paper, 1997)The entrance region to Tysfjorden was acoustically surveyed a total of eleven times during the December 1996 abundance survey of the spawning stock of Norwegian spring-spawning herring (Clupea harengus). The observations ... -
Effect of swimming on fish target strength
(ICES CM Documents;1985/B:29, Working paper, 1985)The influence of the swimming movement on fish target strength is investigated through a modelling exercise. In this, several gadoid specimens are represented as acoustic scatterers through their triangulated swimbladder ... -
Effects of a geophysical survey on catching success in longline fishing
(ICES CM Documents;1991/B:40, Working paper, 1991)The effects on longline catches of a geophysical survey conducted during the winter fishery for cod (Gadus morhua) were studied. Spatial extent of the effects was investigated by comparing the catch rates of longlines ... -
Empirical results on precision - effort relationships for acoustic surveys
(ICES CM Documents;1989/B:30, Working paper, 1989)Repeated echo integrator surveys using a rather dense survey grid were performed in areas where the effect of fish migration was assumed to be insignificant. Relative estimates of fish abundance representing different ... -
Equivalent beam angles for several standard transducers
(ICES CM Documents;1990/B:21, Working paper, 1990)Nominal values for the equivalent beam angle are given for several transducers. These are the standard split-beam transducers designed for the SIMRAD EK500 scientific echo sounder, with operating frequencies of 38 and 120 ... -
Estimation of fish abundance by acoustics during the North Sea Young Herring Survey 1972
(ICES CM Documents;1972/H:10, Working paper, 1972) -
Estimation of unreported catch in a commercial trawl fishery
(ICES CM Documents;1991/D:12, Working paper, 1991)The Institute of Marine Research (IMR), Bergen, has carried out combined bottom trawl and acoustic surveys for cod in the Barents Sea since 1981. Commercial statistics are collected routinely for this area through the ... -
Estimators in acoustic surveying of fish populations
(ICES CM Documents;1976/B:36, Working paper, 1976) -
Evaluation of the North-East Arctic saithe (Pollachius virens) acoustic survey
(ICES CM Documents;1997/Y:20, Working paper, 1997)Since 1985 an acoustic survey specially designed for saithe has annually been conducted in October-November by the Institute of Marine Research (IMR) on the Norwegian near coastal banks. Since 1992 the survey has covered ...