Blar i Published in cooperation with others på forfatter "Ona, Egil"
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Fjordranching with conditioned cod
Midling, Kjell; Kristiansen, Tore S.; Ona, Egil; Øiestad, Victor (ICES CM Documents;1987/F:29, Working paper, 1987)In June 1986, 1600 pond-reared one-year old cod were released into a fjord after being conditioned with a pulsed 160 Hz sound signal to search for food at a feeding location. Echosounders, UW-video and ultrasonic ... -
Haddock avoidance reactions during trawling
Ona, Egil; Chruickshank, O. (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, ... -
How many trawl hauls, and how many fish from each haul are needed to obtain a given precision in the age structure estimate for Norwegian spring spawning herring? A bootstrap approach
Hjellvik, Vidar; Ona, Egil (ICES CM documents, Working paper, 2006)The Norwegian spring spawning herring is assessed each year from acoustic surveys. The age structure in the stock is estimated from trawl samples. Typically, about 10 trawl samples are taken per survey, and 100 fish from ... -
Hull mounted, protruding transducer for improving echo integration in bad weather
Ona, Egil; Traynor, Jimmie J. (ICES CM documents, Working paper, 1990)A 38 kHz split beam survey transducer has been mounted on the tip of a 4 m vertical protrusile stabilizing keel of the United States NOAA fishery research vessel R/V Miller Freeman. Air blocking problems, generally ... -
Hull mounted, protruding transducer for improving echo integration in bad weather
Ona, Egil; Traynor, Jimmie J. (ICES CM Documents;1990/B:31, Working paper, 1990)A 38 kHz split beam survey transducer has been mounted on the tip of a 4 m vertical protrusile stabilizing keel of the United States NOAA fishery research vessel R/V Miller Freeman. Air blocking problems, generally ... -
In situ determination of bottom trawl ground gear contact
Engås, Arill; Ona, Egil; Ramberg, Kjell (ICES CM documents, Working paper, 2001)Exact definition of towed distance with proper ground gear contact is an essential parameter in bottom trawl swept area estimates of fish abundance. Errors in this key parameter may lead to a first order bias in abundance ... -
In situ observations of swimbladder compression in herring
Ona, Egil (ICES CM documents, Working paper, 1984)The hydrostatic function of the swimbladder in herring is experimentally investigated through in situ diver-assisted measurements of swimbladder volume on net-caught and caged fish. In agreement with morpho-physiological ... -
In situ target strength observations on haddock
Ona, Egil; Hansen, Kaare A. (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 ... -
Migratory behaviour of cultured Atlantic salmon smolts released during day or night
Holm, Marianne; Huse, Ingvar; Jørstad, Knut Eirik; Ona, Egil; Skilbrei, Ove (ICES CM documents, Working paper, 1998) -
Modeling fish reaction to vessel noise, the significance of the reaction thresholds
Handegard, Nils Olav; Ona, Egil (ICES CM documents, Working paper, 2001)A simple model of fish reaction to vessel noise is made. The fish are assumed to swim directly away from the noise source. The main noise source is assumed to be the propeller. Parameters for endurance and swimming speed ... -
Modelling herring target strength pressure dependence in the frequency domain
Gorska, Natalia; Ona, Egil (ICES CM documents, Working paper, 2001)Improved understanding of the acoustic scattering properties of the fish is needed when trying to remove potential bias is acoustic abundance estimates. The paper address the problem of systematic pressure or depth dependency ... -
More on the frequency dependence of target strength of mature herring
Foote, Kenneth G.; Hansen, Kaare A.; Ona, Egil (ICES CM Documents;1993/B:30, Working paper, 1993)The hibernating stock of Norwegian spring-spawning herring has been acoustically surveyed in a fjord system in northern Norway in December 1992. The survey frequencies are 18, 38, 120, and 200 kHz. When the corresponding ... -
On acoustic multi-frequency species identification and separation of Atlantic mackerel, Norwegian spring spawn herring and Norway pout.
Gorska, Natalia; Ona, Egil; Korneliussen, Rolf J. (ICES CM documents, Working paper, 2004)The accuracy of the multi-frequency species identification and separation algorithms may be significantly improved when the detailed acoustic scattering characteristics of the fish are known, including its expected variability ... -
On the frequency dependence of target strength of mature herring
Foote, Kenneth G.; Hansen, Kaare A.; Ona, Egil (ICES CM Documents;1992/B:10, Working paper, 1992)Mature herring (Clupea harengus), hibernating in Ofotfjord in December 1991, was measured simultaneously at each of three frequencies: 18, 38, and 120 kHz. Measurements of the mean volume backscattering coefficient were ... -
Optimal acoustic beam pattern corrections for split beam transducers
Ona, Egil (ICES CM Documents;1990/B:30, Working paper, 1990)Precise in situ target strength estimates of fish can only be made when the effect of the transducer directivity is totally removed from the recorded target amplitudes. By guiding a standard calibration target through the ... -
Optimal acoustic beam pattern corrections for split beam transducers
Ona, Egil (ICES CM Documents;1990/B:30, Working paper, 1990)Precise in situ target strength estimates of fish can only be made when the effect of the transducer directivity is totally removed from the recorded target amplitudes. By guiding a standard calibration target through ... -
Preliminary results from tests using a high-frequency sonar as trawl-sonde
Ona, Egil; Eger, K. (ICES CM Documents;1986/B:37, Working paper, 1986)A high-frequency, short-range sonar is tested for trawl-geometry measurements on pelagic and bottom trawls. The sonar was operated on a standard, coaxial trawl sonde cable, and produced excellent images of the trawl ... -
Reactions of herring to trawling noise
Ona, Egil; Toresen, Reidar (ICES CM Documents;1988/B:36, Working paper, 1988)The reaction of herring during pelagic trawl sampling has been studied by use of a high-frequency scanning sonar mounted on the headline of the trawl. The difficulties of obtaining high catch rates on shallow herring ... -
Recommendations for the collection of multifrequency acoustic data
Korneliussen, Rolf J.; Diner, Noel; Ona, Egil; Fernandes, Paul G. (ICES CM Documents;2004/R:36, Working paper, 2004)Traditionally, collection of acoustic data has been optimised for a single frequency, while requirements for the optimal combination of multifrequency data has been given less attention. Even though data manipulation can ... -
The relative frequency response, as derived from individually separated targets on cod, saithe and Norway pout
Pedersen, Geir; Korneliussen, Rolf J.; Ona, Egil (ICES CM documents, Working paper, 2004)The relative frequency response is an important acoustic feature used to characterise acoustic targets. This response has been defined as the sv, volume backscattering coefficient, for a specific frequency relative to ...