Blar i ICES CM documents authored by IMR scientists (1949-2011) på emneord "gear experiments"
Viser treff 21-40 av 117
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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 ... -
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 ... -
Computerbased detection of schools for counting, quantification of size and swimming behavior by the SIMRAD SA950 sonar
(ICES CM Documents;1993/B:17, Working paper, 1993)As a help in stock assessment of pelagic, schooling fish a software for detection of schools and quantification of their size and swimming behaviour by a high resolution sonar has been developed. The system reads the ... -
Cultivation of mussels (Mytilus edulis) by use of net bags
(ICES CM Documents;1970/E:12, Working paper, 1970) -
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 ... -
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 ... -
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 ... -
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 ... -
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 ... -
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 ... -
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 ... -
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 ... -
Evaluation of the Norwegian shrimp surveys conducted in the Barents Sea and the Svalbard area 1980- 1997
(ICES CM Documents;1997/Y:7, Working paper, 1997)Trawl surveys for shrimp (Pandalus borealis) have been conducted annually in the Barents Sea and the Svalbard area since 1980 by Norwegian research institutes. The surveys have been conducted in the period April to ... -
Evidence of sampling induced biases in mortality estimates from experiments investigating mortality in fish escaping from towed fishing gears
(ICES CM Documents;2002/V:25, Working paper, 2002)When studying escapes from trawl codends and other selective devices, the most common method of capturing or ‘sampling’ escaping fish is using a codend cover (Figure 1). This paper will summarise a programme of work providing ... -
Experiences using the constraint technique on bottom trawl doors
(ICES CM Documents;1993/B:18, Working paper, 1993)The constraint technique, i.e. using a rope between the warps, has the intention of minimizing the variability in trawl geometry with depth. Experiments with the constraint technique on two different bottom trawls used ... -
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 ...