Browsing Brage IMR by Author "Ona, Egil"
Now showing items 1-20 of 104
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A method to reduce survey bottom trawl variability
Engås, Arill; Ona, Egil (ICES CM Documents;1991/B:39, Working paper, 1991)A technique for limiting the variability of trawl doorspread is described. In addition, modifications of trawling technique which enable the doors to stay upright and maintain constant ground contact under different ... -
Accuracy of the Kirchhoff-approximation and Kirchhoff-ray-mode fish swimbladder acoustic scattering models
Macaulay, Gavin; Pena, Hector; Fässler, Sacha M.M.; Pedersen, Geir; Ona, Egil (Journal article; Peer reviewed, 2013)The acoustic backscatter from pressure release prolate spheroids and a three-dimensional representation of a fish swimbladder (Chilean jack mackerel, Trachurus symmetricus murphyi) was calculated using four target strength ... -
Accuracy of the Kirchhoff-Approximation and Kirchhoff-Ray-Mode Fish Swimbladder Acoustic Scattering Models
Macaulay, Gavin J.; Peña, Hector; Fässler, Sascha M. M.; Pedersen, Geit; Ona, Egil (Journal article; Peer reviewed, 2013-05-14)The acoustic backscatter from pressure release prolate spheroids and a three-dimensional representation of a fish swimbladder (Chilean jack mackerel, Trachurus symmetricus murphyi) was calculated using four target strength ... -
Acoustic abundance estimation of wintering Norwegian spring spawning herring, with emphasis on methodological aspects
Røttingen, Ingolf; Foote, Kenneth G.; Huse, Ingvar; Ona, Egil (ICES CM Documents;1994/(B+D+G+H):1, Working paper, 1994)The spawning component and part of the juvenile stock of Norwegian spring spawning herring have been wintering in a fjord system in northern Norway in recent years. Conditions for measuring the stock size have been ... -
Acoustic detection of the Greenland shark (Somniosus microcephalus) using multifrequency split beam echosounder in Svalbard waters
Ona, Egil; Nielsen, Julius (Peer reviewed; Journal article, 2022)The conservation status of the long-lived Greenland shark (Somniosus microcephalus) is unknown, and methods for non-invasively estimating local or regional abundances are wanted. Using a multifrequency split beam echosounder ... -
Acoustic estimates of 0-group fish abundance in the Barents Sea and adjacent waters in 1992 and 1993
Nakken, Odd; Hylen, Arvid; Ona, Egil (PINRO-IMR Symposium, Conference object, 1995)Acoustic and biological data collected during the international O-group surveys in 1992 and 1993 were used to estimate the abundance of O-group fish of 4 species; cod, haddock, redfish and polar cod. The abundances of ... -
Acoustic extinction in dense herring layers, measured from a bottom-mounted transducer
Utne, Kjell R.; Ona, Egil (ICES CM documents, Working paper, 2006)Herring is often found in dense aggregations or schools, and acoustic shadowing is thus a problem in acoustic survey estimates. Knowledge of the attenuated echo intensity in herring aggregations is essential for correcting ... -
Acoustic properties of Salpa thompsoni.
Wiebe, Peter H.; Chu, Dezhang; Kaartvedt, Stein; Hundt, Anna (Hölter); Melle, Webjørn; Ona, Egil; Batta-Lona, Paola (ICES CM documents;2009 / I:01, Working paper, 2009)Salps are common members of the world oceans planktonic community (Madin, et.al., 2006). In the southern ocean, both krill (Euphausia superba) and salps (Salpa thompsoni) can occur in dense aggregations (Loeb et al, 2009, ... -
Angular distribution of overwintering Norwegian spring spawning herring
Huse, Ingvar; Foote, Kenneth G.; Ona, Egil; Røttingen, Ingolf (ICES CM documents, Working paper, 1994)When plankton production drops off in the fall, adult Norwegian spring spawning herring migrate to two fiords in northern Norway with stable water masses with low temperature and predation. In the wintering areas, the ... -
Antarctic krill (Euphausia superba) catch weight estimated with a trawl-mounted echosounder during fishing
Krafft, Bjørn Arne; Krag, Ludvig A.; Pedersen, Ronald; Ona, Egil; Macaulay, Gavin (Peer reviewed; Journal article, 2023)Reporting reliable catch weight estimates is important for all fisheries management. This study explores the potential for precise and direct estimation of catch weight (green weight) for the Antarctic krill (Euphausia ... -
Atlantic cod (Gadus morhua)feeding over deep water in the high Arctic
Ingvaldsen, Randi Brunvær; Gjøsæter, Harald; Ona, Egil; Michalsen, Kathrine (Peer reviewed; Journal article, 2017) -
Avoidance reactions of herring to a survey vessel, studied by scanning sonar
Ona, Egil; Toresen, Reidar (ICES CM Documents;1988/H:46, Working paper, 1988)The behavioural response of a shallow herring layer to a steaming vessel has been studied by the use of a high-resolution scanning sonar technique. When the vessel was completely darkened, no significant reaction important ... -
Bergen Ekko Integrator
Ona, Egil (Havforskningsnytt, Working paper, 1998) -
The Bergen multifrequency analyzer (BMA): A new toolbox for acoustic catagorization and species identification
Ona, Egil; Korneliussen, Rolf J.; Knudsen, Hans Petter; Rang, Kjell; Eliassen, Inge; Heggelund, Yngve; Patel, Daniel (Others, 2004) -
Biologiske ressurser i området som er aktuelt som trasé for kraftkabler fra Norge til kontinentet
Sundt, Rolf C.; Bergstad, Odd Aksel; Fossum, Petter; Ona, Egil (Interne notat, Working paper, 1995)Rapporten er utarbeidet på oppdrag fra Statkraft Engineering, i anledning planleggingen av linjenett for overføring av elektrisk kraft fra Norge til kontinentet. Utredningen er en del av arbeidet med å vurdere konsekvensene ... -
Calibrating split beam transducers at depth
Ona, Egil; Pedersen, Geir (Journal article; Peer reviewed, 2006) -
Changes in acoustic abundance - a signal indicatior for stock dynamics for cod (Gadus morhua)
Godø, Olav Rune; Ona, Egil (ICES CM documents, Working paper, 1999)To be able to take the proper and timely management actions, it is crucial to reliably defect major changes in trends of fish stock abundance. For the assessment of Northeast Arctic cod, the Norwegian bottom trawl survey ... -
Combined algorithms for detection of acoustic categories
Korneliussen, Rolf J.; Ona, Egil (ICES CM Documents;2004/R:38, Working paper, 2004)There is a current desire to harvest marine resources by managing total marine ecosystems rather than single species of the ecosystems. By means of algorithms applied on high-quality multi-frequency acoustic data, species, ... -
Comparative analysis of split beam data
Kieser, Robert; Ona, Egil (ICES CM Documents;1988/B:44, Working paper, 1988)Split beam data can provide high quality, in situ, fish target strength estimates, however a careful calibration is required to realize this potential. In same cases a standard target has been used to make a large number ... -
Comparison of the capture efficiency of 0-group fish in pelagic trawls
Hylen, Arvid; Korsbrekke, Knut; Nakken, Odd; Ona, Egil (PINRO-IMR Symposium, Conference object, 1995)In 1992 and 1993 experiments were carried out during the international 0-group fish surveys in order to study the capture efficiency of two pelagic trawls. The catches of the standard sampling trawl were compared with ...