Advanced search    

Search: authors:"Egil Ona"

28 papers found.
Use AND, OR, NOT, +word, -word, "long phrase", (parentheses) to fine-tune your search.

Atlantic cod (Gadus morhua) feeding over deep water in the high Arctic

The Atlantic cod (Gadus morhua) is a highly adaptive demersal, boreal species with a broad distribution on the continental shelves on both sides of the North Atlantic. However, whether the species also uses adjoining deeper water basins as feeding grounds or migration corridors remain unknown. In this study, we aimed to describe the vertical and horizontal distributions of Atlantic ...

Broad bandwidth acoustic backscattering from sandeel—measurements and finite element simulations

Acoustic backscattering measurements were made of individual sandeel (Ammodytes marinus L.) at frequencies from 100 to 280 kHz in a laboratory tank. Measurements were made versus incidence angle, −30° to 30° relative to both dorsal and lateral aspect directions, for dead whole sandeel and for excised backbones. Backscatter spectra from whole fish have deep minima at frequencies ...

Target strength and tilt-angle distribution of the lesser sandeel (Ammodytes marinus)

Target strength and tilt-angle distribution of lesser sandeel (Ammodytes marinus) - ICES Journal of Marine Science Marine Science Rokas Kubilius 0 1 Egil Ona 0 0 Institute of Marine Research , PO

Feeding herring schools do not react to seismic air gun surveys

Peña, H., Handegard, N. O. and Ona, E. 2013. Feeding herring schools do not react to seismic air gun surveys. – ICES Journal of Marine Science, 70: 1174–1180. The real-time behaviour of herring schools exposed to a full-scale 3D seismic survey off Vesterålen, northern Norway, was observed using an omnidirectional fisheries sonar. Throughout the study period, the herring swam slowly ...

Measuring herring densities with one real and several phantom research vessels

phantom research vessels Ruben Patel Egil Ona Vessel-induced avoidance can potentially cause a large bias in acoustic estimates of schooling, pelagic-fish biomass. This paper presents a method for

Marine ecosystem acoustics (MEA): quantifying processes in the sea at the spatio-temporal scales on which they occur

Sustainable management of fisheries resources requires quantitative knowledge and understanding of species distribution, abundance, and productivity-determining processes. Conventional sampling by physical capture is inconsistent with the spatial and temporal scales on which many of these processes occur. In contrast, acoustic observations can be obtained on spatial scales from ...

Accuracy of the Kirchhoff-Approximation and Kirchhoff-Ray-Mode Fish Swimbladder Acoustic Scattering Models

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 models (Kirchhoff-approximation, Kirchhoff-ray-mode, finite element solution of the Helmholtz equation, and prolate-spheroid-modal-series). Smoothly varying ...

A revised target strength–length estimate for blue whiting (Micromesistius poutassou): implications for biomass estimates

Pedersen, G., Godø, O. R., Ona, E., and Macaulay, G. J. 2011. A revised target strength–length estimate for blue whiting (Micromesistius poutassou): implications for biomass estimates. – ICES Journal of Marine Science, 68: 2222–2228. Acoustic abundance estimates of blue whiting have generally been higher than estimates based on catch data. One explanation has been that the ...

Size-dependent frequency response of sandeel schools

Johnsen, E., Pedersen, R., and Ona, E. 2009. Size-dependent frequency response of sandeel schools. – ICES Journal of Marine Science, 66: 1100–1105. Annual Norwegian sandeel surveys have been conducted in the North Sea since 2005 to measure the stock of lesser sandeel (Ammodytes marinus). Target identification is often a major challenge in acoustic surveys, and discriminant analyses ...

Lateral-aspect, target-strength measurements of in situ herring (Clupea harengus)

) Geir Pedersen Nils Olav Handegard Egil Ona Surveys of schooling herring with the new multibeam sonar (Simrad MS70) pose new challenges when converting the echo energy to estimates of biomass. Because

Calibration methods for two scientific multibeam systems

Egil Ona 0 Valerie Mazauric 0 Lars Nonboe Andersen 0 0 E. Ona: Institute of Marine Research , PO Box 1870 Nordnes, NO 5817 Bergen , Norway. V. Mazauric: Ifremer-Paris, Direction des Moyens et Ope

The use of an adaptive acoustic-survey design to estimate the abundance of highly skewed fish populations

Alf Harbitz Egil Ona Michael Pennington The uncertainty (relative root-mean-square error) of abundance estimates based on a simple and easily implemented adaptive design for an acoustic survey is

An expanded target-strength relationship for herring

Egil Ona Target-strength (TS) experiments on captive, adult herring have been conducted at intervals over several years to investigate the acoustic effect of pressure and seasonal changes on fish

Correcting for vessel avoidance in acoustic-abundance estimates for herring

Vidar Hjellvik Nils Olav Handegard Egil Ona When a research vessel passes over a school or layer of herring (Clupea harengus), the fish may avoid the vessel by swimming downwards and horizontally

Acoustic backscatter by schools of adult Atlantic mackerel

Gorska, N., Korneliussen, R. J., and Ona, E. 2007. Acoustic backscatter by schools of adult Atlantic mackerel. – ICES Journal of Marine Science, 64: 1145–1151. The extent of acoustic backscatter by schools of adult Atlantic mackerel (Scomber scombrus) is investigated to improve biomass estimates. Previous studies involving modelled scattering from individual mackerel showed that ...

Modelling the acoustic effect of swimbladder compression in herring

Natalia Gorska Egil Ona Obtaining accurate data on fish target strength (TS) is important when determining the quality of the results from acoustic surveys. However, this requires an improved

Modelling the effect of swimbladder compression on the acoustic backscattering from herring at normal or near-normal dorsal incidences

Natalia Gorska 0 Egil Ona 0 0 N. Gorska; Institute of Oceanology of Polish Academy of Sciences , ul. Powstancow Warszawy 55, PL-81-712 Sopot , Poland. E. Ona: Institute of Marine Research , PO Box

Estimation and compensation models for the shadowing effect in dense fish aggregations

Xianyong Zhao 0 Egil Ona 0 0 X. Zhao: Yellow Sea Fisheries Research Institute , 106 Nanjing Road, Qingdao 266071 , P. R. China This paper addresses the problem of acoustic ''shadowing'' (i.e

The acoustic properties of Salpa thompsoni

Wiebe, P. H., Chu, D., Kaartvedt, S., Hundt, A., Melle, W., Ona, E., and Batta-Lona, P. 2010. The acoustic properties of Salpa thompsoni. – ICES Journal of Marine Science, 67: 583–593. Aggregations of the salp Salpa thompsoni were encountered during the Antarctic krill and ecosystem-studies cruise on the RV “G.O. Sars” from 19 February to 27 March 2008. The salp's in situ target ...

Synthetic echograms generated from the relative frequency response

Calibrated, digitized data from multi-frequency echo sounders have been used to generate new, synthetic echograms. The relative frequency response measured at four acoustic frequencies (18, 38, 120, and 200 kHz) is the main acoustic feature used to characterize the acoustic targets. Synthetic echograms are used to enhance and colour-code sample volumes with similar acoustic ...