Blar i Brage IMR på forfatter "Klevjer, Thor Aleksander"
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Application of an unsupervised clustering algorithm on in situ broadband acoustic data to identify different mesopelagic target types
Agersted, Mette Dalgaard; Khodabandeloo, Babak; Liu, Yi; Melle, Webjørn Raunsgård; Klevjer, Thor Aleksander (Peer reviewed; Journal article, 2021)The mesopelagic zone (200–1000 m depth) contains high fish species diversity but biomass and abundances are uncertain yet essential to understand ecosystem functioning. Hull-mounted acoustic systems (usually 38 kHz) often ... -
Diel vertical migration and individual behavior of nekton beyond the ocean's twilight zone
Kaartvedt, Stein; Røstad, Anders; Christiansen, Svenja; Klevjer, Thor Aleksander (Peer reviewed; Journal article, 2020)Diel vertical migration (DVM) is normally limited to the upper 1000 m. However, the use of ship-borne and stationary submerged echosounders in the Red Sea unveiled consistent formation of daytime patches extending to ... -
Estimating target strength and physical characteristics of gas-bearing mesopelagic fish from wideband in situ echoes using a viscous-elastic scattering model
Khodabandeloo, Babak; Agersted, Mette Dalgaard; Klevjer, Thor Aleksander; Macaulay, Gavin John; Melle, Webjørn Raunsgård (Peer reviewed; Journal article, 2021)Wideband (38 and 50–260 kHz) target strength of organisms were measured in situ using a towed platform in mesopelagic (200–1000 m depth) layers. Organisms with a gas-inclusion are strong scatterers of sound and acoustically ... -
Flexible behaviour in a mesopelagic fish (Maurolicus muelleri)
Klevjer, Thor Aleksander; Røstad, Anders; Aksnes, Dag Lorents; Kaartvedt, Stein (Peer reviewed; Journal article, 2021)Variability of mesopelagic scattering layers is often attributed to environmental conditions or multi-species layer composition. Yet, little is known about variation in behaviour among the individuals forming scattering ... -
Flexible behaviour in a mesopelagic fish (Maurolicus muelleri)
Christiansen, Svenja; Klevjer, Thor Aleksander; Røstad, Anders; Aksnes, Dag Lorents; Kaartvedt, Stein (Peer reviewed; Journal article, 2021)Variability of mesopelagic scattering layers is often attributed to environmental conditions or multi-species layer composition. Yet, little is known about variation in behaviour among the individuals forming scattering ... -
Mesopelagic fish gas bladder elongation, as estimated from wideband acoustic backscattering measurements
Khodabandeloo, Babak; Ona, Egil; Pedersen, Geir; Korneliussen, Rolf; Melle, Webjørn Raunsgård; Klevjer, Thor Aleksander (Peer reviewed; Journal article, 2022)Backscattered acoustic energy from a target varies with frequency and carries information about its material properties, size, shape, and orientation. Gas-bearing organisms are strong reflectors of acoustic energy at the ... -
Using vessel acoustics to detect diving patterns of krill foraging predators automatically: development of a novel method for quantifying impact of krill fishing on seals and penguins
Klevjer, Thor Aleksander; Krafft, Bjørn Arne; Godø, Olav Rune (;WG-EMM-15/25, Research report, 2015-06-20)The aim of this work was to assess the possibilities of automatically generating a dataset of dive behaviour of air-breathing predators, based on acoustic data from a monitoring survey and from commercial krill fishing ...