Blar i Brage IMR på forfatter "Ona, Egil"
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Comparisons of echo-integration performance from two different multiplexed echosounders
Macaulay, Gavin; Schoulding, Ben; Ona, Egil; Fässler, Sascha M. M. (Journal article; Peer reviewed, 2018)A time-series of acoustically derived aquatic biomass estimates relies on the acoustic equipment maintaining the same performance throughout the time-series. This is normally achieved through a regular calibration process. ... -
Complete acoustic recording of water column scatters and sea bed characteristics.
Knudsen, Hans Petter; Melle, Webjørn; Misund, Ole Arve; Ona, Egil; Aksnes, Dag Lorents; Seirup, Hans Petter (The Journal of the Acoustical Society of America, Others, 2001) -
Correcting for avoidance in acoustic abundance estimates for herring using a generalized linear model
Hjellvik, Vidar; Handegard, Nils Olav; Ona, Egil (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. ... -
CRIMAC - Annual Report 2020
Ona, Egil; Handegard, Nils Olav; Pedersen, Geir; Forland, Tonje Nesse; Tenningen, Maria; Johnsen, Espen (Research report, 2021) -
Day and night fish distribution pattern in the net mouth area of the Norwegian bottom-sampling trawl
Engås, Arill; Ona, Egil (Journal article; Peer reviewed, 1990)A high-frequency scanning sonar, mounted as a net sonde, was used to study fish behaviour in the mouth area of the Norwegian bottom-sampling trawl. Fish distribution patterns were significantly different by day and night. ... -
A deep scattering layer under the North Pole pack ice
Snoeijs-Leijonmalm, Pauline; Gjøsæter, Harald; Ingvaldsen, Randi Brunvær; Knutsen, Tor; Korneliussen, Rolf; Ona, Egil; Skjoldal, Hein Rune; Stranne, Christian; Mayer, Larry; Jakobsson, Martin; Gårdfeldt, Katarina (Peer reviewed; Journal article, 2021)The 3.3 million km2 marine ecosystem around the North Pole, defined as the Central Arctic Ocean (CAO), is a blind spot on the map of the world’s fish stocks. The CAO essentially comprises the permanently ice-covered deep ... -
Detailed in situ target strength measurements of 0-group cod
Ona, Egil (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
Ona, Egil; Knutsen, Tor (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 spatial distribution of acoustic categories
Korneliussen, Rolf J.; Ona, Egil (ICES CM documents, Working paper, 2005) -
Determining the entrance position of fish in trawls
Ona, Egil (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, ... -
Determining the extinction cross section of aggregating fish
Foote, Kenneth G.; Ona, Egil; Toresen, Reidar (Journal article; Peer reviewed, 1992)When fish are aggregated over a flat bottom, and fish and bottom echoes can be distinguished, it is possible to determine the fish extinction cross section by a simple application of the echo integration method. The theory ... -
Differences in swimbladder volume between Baltic and Norwegian spring spawning herring: possible consequences for mean target strength
Fässler, Sascha M.M.; Gorska, Natalia; Ona, Egil (ICES CM documents;2007/H:03, Working paper, 2007)Volume and shape of the swimbladder of Baltic and Norwegian spring spawning herring were measured, together with individual herring fat content. Swimbladder size was found to differ significantly between the two herring ... -
Direct measurements of equivalent beam angle on hull-mounted transducers
Ona, Egil; Vestnes, Gudmund (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 ... -
Effects of seismic shooting on catch and catch-availability of cod and haddock
Engås, Arill; Løkkeborg, Svein; Ona, Egil; Soldal, Aud Vold (Fisken og havet, Research report, 1993) -
Effects of seismic shooting on local abundance and catch rates of cod (Gadus morhua) and haddock (Melanogrammus aeglefinus)
Engås, Arill; Løkkeborg, Svein; Ona, Egil; Soldal, Aud Vold (Journal article; Peer reviewed, 1996)To determine whether seismic exploration affected abundance or catch rates of cod (Gadus morhua) and haddock (Melanogrammus aeglefinus), acoustic mapping and fishing trials with trawls and longlines were conducted in the ... -
Effekter av seismisk skyting på fangst og fangsttilgjengelighet av torsk og hyse
Engås, Arill; Løkkeborg, Svein; Ona, Egil; Soldal, Aud Vold (Fisken og havet, Research report, 1993) -
Effekter av seismiske undersøkelser på fiskefordeling og fangstrater for garn og line i Vesterålen sommeren 2009 : Effects of seismic surveys on fish distribution and catch rates of gillnets and longlines in Vesterålen in summer 2009
Løkkeborg, Svein; Ona, Egil; Vold, Aud; Peña, Hector; Salthaug, Are; Totland, Bjørn; Øvredal, Jan Tore; Dalen, John; Handegard, Nils Olav (Fisken og havet, Research report, 2010-02-22)In connection with the Norwegian Petroleum Directorate’s seismic survey off the coasts of Vesterålen in summer 2009, a project was carried out to study the degree to which commercial fishes were affected. Four chartered ... -
Experiences using the constraint technique on bottom trawl doors
Engås, Arill; Ona, Egil (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
Ona, Egil; Røttingen, Ingolf (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 ... -
Feasibility study on the use of scientific multibeam sonar to characterize the Atlantic Bluefin Tuna spawning stock
Tenningen, Maria; Pena, Hector; Korneliussen, Rolf; Ona, Egil; Pons, Vicent Puig (Rapport fra havforskningen;2019 - 34, Research report, 2019)The Institute of Marine Research (IMR) and the Polytechnic University of Valencia (UPV) were invited by ICCAT Atlantic-Wide Research Program for Bluefin Tuna (GBYP) to carry out a feasibility study on the use of scientific ...