Blar i ICES CM documents authored by IMR scientists (1949-2011) på forfatter "Øvredal, Jan Tore"
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A new radio link telemetry positioning system, experiences from tracking of fish and crustaceans
Bjordal, Åsmund; Engås, Arill; Soldal, Aud Vold; Øvredal, Jan Tore (ICES CM Documents;1993/B:23, Working paper, 1993)Telemetry positioning systems based on hydrophone arrays have been used for different tracking applications. The main improvement of this new system is the wire-less transmission of signals from hydrophone - radio buoys ... -
A PC-based echo integrator system appliable for school structure analyzis
Floen, Svein; Totland, Bjørn; Øvredal, Jan Tore; Misund, Ole Arve (ICES CM Documents;1991/B:43, Working paper, 1991)A low cost system for integration of echo signals on a PC has been developed. The system calculates the area backscattering strength in surface and bottom layers, and is designed both for the purpose of conventional ... -
Acoustic measurements of schooling herring. Estimation of school biomass and target strength
Misund, Ole Arve; Øvredal, Jan Tore (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 ... -
Automatic recording of fish heart rate on a personal computer
Floen, Svein; Totland, Bjørn; Øvredal, Jan Tore (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 ... -
Automatic species recognition, length measurement and weight determination, using the CatchMeter computer vision system
Svellingen, Cato; Totland, Bjørn; White, Darren; Øvredal, Jan Tore (ICES CM documents, Working paper, 2006)The collection of biological data on species composition and individual length and weight of specimen has always been an important part of fisheries research. Traditionally, the collected information has been recorded on ... -
Avoidance reactions of ultrasonic tagged cod during bottom trawling in shallow water
Engås, Arill; Soldal, Aud Vold; Øvredal, Jan Tore (ICES CM Documents;1991/B:41, Working paper, 1991)Introduction: Observations made by echo sounder (Ona 1988) have shown that cod (Gadus morhua L.) may avoid an approaching survey vessel horizontally and vertically. However, there has been a lack of information on the ... -
How and why acoustic detectability and catchability of herring change with individual motivation and physiological state in a variable environment: a multi-scale study on a local herring population in southwestern Norway
Langård, Lise; Nøttestad, Leif; Johannessen, Arne; Fernö, Anders; Øvredal, Jan Tore; Skaret, Georg; Nilsson, Gro N.; Vabø, Rune (ICES CM documents, Working paper, 2006)The understanding of distribution and aggregation in herring (Clupea harengus) can be enhanced by integrated multi-scale studies in small ecosystems. Hydro-acoustics, underwater cameras, herring and predator gillnet samples ... -
Observation of fish behaviour, density and distribution around a surveying vessel by means of a deployable echo sounder system
Øvredal, Jan Tore; Huse, Ingvar (ICES CM Documents;1999/J:9, Working paper, 1999)Detailed acoustic observations of fish behaviour, distribution and density in the trawl area are necessary in order to establish quantitative relationships between trawl samples and fish density. Acoustic observation ... -
PC-based echo integration system for fish behaviour studies
Floen, Svein; Totland, Bjørn; Øvredal, Jan Tore (ICES CM Documents;1988/B:35, Working paper, 1988)An echo integration system presenting the distribution and vertical and horizontal movements of fish in net pens, is described. The system can be configured to multiplex up to 16 transducers sequentially. The number of ... -
Quantifying the amount of fish unavailable to a bottom trawl by use of an upward looking transducer
Michalsen, Kathrine; Aglen, Asgeir; Somerton, David; Svellingen, Ingvald; Øvredal, Jan Tore (ICES CM documents, Working paper, 1999)When surveying demersal fish with a wide and variable vertical distribution, it is desirable to combine information from a bottom trawl survey with the information from a hydroacoustic survey into an absolute abundance ... -
Spatial and temporal overlap and trophic interactions between Atlantic Saithe (Pollachius virens) and Norwegian spring spawning herring (Clupea harengus) on herring spawning grounds
Slotte, Aril; Runde, Arne; Skaret, Georg; Axelsen, Bjørn Erik; Fernö, Anders; Johannessen, Arne; Nøttestad, Leif; Øvredal, Jan Tore (ICES CM documents, Working paper, 2005)Atlantic saithe (Pollachius virens) and Norwegian spring-spawning herring (Clupea harengus) represent two of the most abundant and ecologically important fish species in the Northeast Atlantic. The two species co-occur ...