Blar i ICES CM documents authored by IMR scientists (1949-2011) på emneord "VDP::Agriculture and fishery disciplines: 900::Fisheries science: 920::Fisheries technology: 924"
Viser treff 61-80 av 493
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Day / night variation in fish directivity in the trawl opening
(ICES CM Documents;1994/B:18, Working paper, 1994)Still photographs of fish in the mouth area of a bottom trawl were taken by a downwards-oriented automated strobe camera mounted near the headrope. Fish angles relative to the towing direction were measured. Fish were ... -
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 ... -
Demersal pair trawling and its operational parameters.
(ICES CM Documents;1982/B:36, Working paper, 1982) -
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. ... -
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 ... -
Detection and counting of individual free-swimming krill using a 2MHz scanning sonar
(ICES CM Documents;1992/L:18, Working paper, 1992)The euphausiid crustacean Meganyctiphanes norvegica (M. Sars) have been detected and counted in the scanning section of a 2 MHz scanning sonar beam up to 3 meters from the sonar head. The tests completes a pilot investigation ... -
Detection of internally tagged fish with special application to the atlanto-scandian herring
(ICES CM Documents;1977/H:20, Working paper, 1977)The paper describes the operating principle and use of a new machine for detection and sorting of internally tagged fish. The machine has been used in the calculation of the Atlanto-Scandian herring stock size. Fixed ... -
Determining the entrance position of fish in trawls
(ICES CM documents, Working paper, 1999)The entrance position of a fish is defined as its two-dimensional position in a cross section of a trawl near the centre of the headline. Individual fish entering the trawl: detected by highresolution scanning sonar, ... -
Development and testing of rope and large meshed midwater trawls in Norway
(ICES CM Documents;1977/B:40, Working paper, 1977) -
Development of a species-selective trawl for demersal gadoid fisheries
(ICES CM Documents;1995/B+G+H+J+K:1, Working paper, 1995)An experiment was carried out to test a prototype species-selective bottom trawl for separating cod from haddock, secondarily saithe, in the Norwegian commercial roundfish fisheries. A sorting system incorporating a ... -
The development of acoustic instrumentation in fisheries research and commercial fisheries in Norway
(ICES CM Documents;1966/F:8, Working paper, 1966) -
Differences between near bottom biomass spatial structure observed in the Irish Sea, the North Sea and the Barents Sea in recent years
(ICES CM documents, Working paper, 2003)Based on acoustic data and trawl catches collected during bottom trawl surveys, we compare the spatial structure of the biomass available in the first meters above the bottom in three different regions, the Barents Sea ... -
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 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 ... -
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 variation in bottom trawl survey catches: does it pay to adjust?
(ICES CM Documents;2001/Q:11, Working paper, 2001)We have studied the diurnal bias of bottom trawl survey catches with the purpose of adjusting for it and thereby improving the accuracy of abundance estimates. The correction term is estimated with uncertainty, and thus ... -
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 ... -
Diurnal variation models of bottom trawl survey catches parameterised by using commercial CPUE data
(ICES CM Documents;2004/R:41, Working paper, 2004)Introduction: Diurnal variation is observed in almost all marine surveys and can cause biased abundance and length frequency estimates. Symmetric logistic models developed by Hjellvik et al. (2001) were utilized to ...