Browsing Brage IMR by Author "Klevjer, Thor A."
Now showing items 1-20 of 23
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Acoustic micronektonic distribution and density is structured by macroscale oceanographic processes across 17–48° N latitudes in the North Atlantic Ocean
García-Seoane, Eva; Klevjer, Thor A.; Mork, Kjell Arne; Agersted, Mette Dalgaard; Macaulay, Gavin; Melle, Webjørn Raunsgård (Peer reviewed; Journal article, 2023)This study investigates the large-scale distribution patterns of the acoustic scattering layers and micronekton density across the Northeast Atlantic Ocean during daylight hours. A research cruise on board R/V “Kronprins ... -
An acoustic method to observe the distribution and behaviour of mesopelagic organisms in front of a trawl
Underwood, Melanie; García-Seoane, Eva; Klevjer, Thor A.; Macaulay, Gavin; Melle, Webjørn Raunsgård (Peer reviewed; Journal article, 2020) -
Antarctic krill swarm characteristics in the Southeast Atlantic sector of the Southern Ocean
Krafft, Bjørn A.; Skaret, Georg; Knutsen, Tor; Melle, Webjørn; Klevjer, Thor A.; Søiland, Henrik (Journal article; Peer reviewed, 2012-09-28)Knowledge about swarm dynamics and underlying causes is essential to understand the ecology and distribution of Antarctic krill Euphausia superba. We collected acoustic data and key environmental data continuously across ... -
Behavior of individual mesopelagic fish in acoustic scattering layers of Norwegian fjords
Kaartvedt, Stein; Torgersen, Thomas; Klevjer, Thor A.; Røstad, Anders; Devine, Jennifer A. (Journal article; Peer reviewed, 2008-05-22)Mesopelagic acoustic scattering layers (SLs) in 2 fjords were studied from a stationary research vessel. Diel vertical movements of SLs were assessed by hull-mounted transducers, while in situ behavior of individuals ... -
Distribution and biomass estimation of Antarctic krill (Euphausia superba) off the South Orkney Islands during 2011-2020
Skaret, Georg; Macaulay, Gavin; Pedersen, Ronald; Wang, X.; Klevjer, Thor A.; Krag, L.A.; Krafft, Bjørn Arne (Peer reviewed; Journal article, 2023)Antarctic krill is a key species in the Southern Ocean and subject to the most extensive fishery in the Antarctic. The Norwegian Institute of Marine Research has conducted acoustic-trawl monitoring of krill off the South ... -
Distribution and composition of mesopelagic macroplankton and micronekton in the North-east Atlantic
Garcia-Seoane, E.; Klevjer, Thor A.; Knutsen, Tor; Macaulay, Gavin; Mork, Kjell Arne; Rosen, Shale; Strand, Espen; Wienerroither, Rupert; Underwood, Melanie; Melle, Webjørn Raunsgård (Lecture, 2018) -
Distribution of Antarctic krill and apex predators at South Orkney Islands in 2014, and assessing escape mortality of krill in trawls
Krafft, Bjørn A.; Krag, Ludvig A.; Klevjer, Thor A.; Skaret, Georg; Pedersen, Ronald (Rapport fra Havforskningen;Nr. 10-2014, Working paper, 2014) -
Does seismic have an effect on zooplankton? - Field study at Ekofisk with RV Kristine Bonnevie
Utne-Palm, Anne Christine; de Jong, Karen; Pedersen, Geir; Klevjer, Thor A.; Titelman, Josefin; Strand, Espen; Vereide, Emilie Hernes; Kühn, Saskia; Hannaas, Sigurd; Totland, Atle; Buschmann, Håvard Johnsen; Mihaljevic, Marina; Strømme, Rune; Johannesen, Reidar (Toktrapport;2022 - 9, Research report, 2022)Toktnr: 2022611 -
Dynamics of phytoplankton species composition, biomass and nutrients in the North Atlantic during spring and summer - A trans-Atlantic study
Naustvoll, Lars Johan; Melle, Webjørn Raunsgård; Klevjer, Thor A.; Drinkwater, Kenneth F.; Strand, Espen; Knutsen, Tor (Peer reviewed; Journal article, 2020)During a return trip in May–June 2013 from Bergen, Norway, to Nuuk, Greenland, on the Institute of Marine Research's R/V “G. O. Sars”, four ocean basins, the Norwegian, Iceland, Irminger and Labrador seas, were surveyed ... -
Ecology of mesozooplankton across four North Atlantic basins
Strand, Espen; Klevjer, Thor A.; Melle, Webjørn Raunsgård; Knutsen, Tor (Peer reviewed; Journal article, 2020)A comparative study of the mesozooplankton in four North Atlantic basins is presented. During a trans-Atlantic expedition with R/V G.O. Sars in May and June 2013, the Norwegian Sea, Iceland Sea, Irminger Sea and Labrador ... -
Evidence for light-controlled migration amplitude of a sound scattering layer in the Norwegian Sea
Norheim, Eirik; Klevjer, Thor A.; Aksnes, Dag Lorents (Journal article; Peer reviewed, 2016-06-09)The oceanic sound scattering layer (SL) is an ubiquitous acoustic signature of mesopelagic fishes and invertebrates that are important food sources for the oceanic macrofauna and players in the biological carbon pump. We ... -
Evidence of temperature control on mesopelagic fish and zooplankton communities at high latitudes
Chawarski, Julek; Klevjer, Thor A.; Coté, David; Geoffroy, Maxime (Peer reviewed; Journal article, 2022)Across temperate and equatorial oceans, a diverse community of fish and zooplankton occupies the mesopelagic zone, where they are detectable as sound-scattering layers. At high latitudes, extreme day-night light cycles may ... -
Feeding ecology of Benthosema glaciale across the North Atlantic
Knutsen, Tor; Strand, Espen; Klevjer, Thor A.; Salvanes, Anne Gro Vea; Broms, Cecilie; Sunde, Synne Myhre; Aksnes, Dag Lorents; García-Seoane, Eva; Melle, Webjørn Raunsgård (Peer reviewed; Journal article, 2023)The glacier lanternfish Benthosema glaciale is a key myctophid with a wide distribution in the northern Atlantic. It is a species that has a strong vertical migration capacity and have the potential to move between the ... -
Fine-scale observations of physical and biological environment along a herring feeding migration route
Melle, Webjørn Raunsgård; Klevjer, Thor A.; Strand, Espen; Wiebe, Peter H.; Slotte, Aril; Huse, Geir (Peer reviewed; Journal article, 2020)We observed herring horizontal and vertical distribution during feeding migration along a 128 km transect across the Arctic front of the Norwegian and Iceland seas, in early June, in relation to its physical, chemical and ... -
Large scale patterns in vertical distribution and behaviour of mesopelagic scattering layers
Klevjer, Thor A.; Irigoien, Xabier; Røstad, Anders; Fraile-Nuez, Eugenio; Benítez-Barrios, Verónica María; Kaartvedt, Stein (Journal article; Peer reviewed, 2016-01-27)Recent studies suggest that previous estimates of mesopelagic biomasses are severely biased, with the new, higher estimates underlining the need to unveil behaviourally mediated coupling between shallow and deep ocean ... -
Mass estimates of individual gas-bearing mesopelagic fish from in situ wideband acoustic measurements ground-truthed by biological net sampling
Agersted, Mette Dalgaard; Khodabandeloo, Babak; Klevjer, Thor A.; García-Seoane, Eva; Strand, Espen; Underwood, Melanie; Melle, Webjørn Raunsgård (Peer reviewed; Journal article, 2021)A new acoustic approach to estimate the mass of individual gas-bearing fish at their resident depth at more than 400 m was tested on Cyclothone spp.. Cyclothone are small and slender, and possibly numerically underestimated ... -
Mesopelagic flesh shear viscosity estimation from in situ broadband backscattering measurements by a viscous–elastic model inversion
Khodabandeloo, Babak; Agersted, Mette Dalgaard; Klevjer, Thor A.; Pedersen, Geir; Melle, Webjørn Raunsgård (Peer reviewed; Journal article, 2021)In fisheries acoustics, target strength (TS) is a key parameter in converting acoustic measurements to biological information such as biomass. Modelling is a versatile tool to estimate TS of marine organisms. For swimbladdered ... -
Micronekton biomass distribution, improved estimates across four north Atlantic basins
Klevjer, Thor A.; Melle, Webjørn Raunsgård; Knutsen, Tor; Strand, Espen; Korneliussen, Rolf; Dupont, Nicolas; Salvanes, Anne Gro Vea; Wiebe, Peter H. (Peer reviewed; Journal article, 2019)Distribution of micronekton was investigated during early summer of 2013, using data from a cruise covering the central parts of four north Atlantic basins, the Norwegian Sea (NS), Iceland Sea (ICS), Irminger Sea (IRS), ... -
Pelagiske økosystem i De nordiske hav - grunnlagsstudie knyttet til åpningsprosess for utforskning og utvinning av havbunnsmineraler på norsk kontinentalsokkel
Kutti, Tina; Mork, Kjell Arne; Chierici, Melissa; Børsheim, Knut Yngve; Bagøien, Espen; Knutsen, Tor; Broms, Cecilie; Klevjer, Thor A.; Strand, Espen; Gjøsæter, Harald; Stenevik, Erling Kåre; Høines, Åge Sigurd; Windsland, Kristin; Frie, Anne Kirstine Højholt (Rapport fra havforskningen;2021 - 41, Research report, 2021)Denne rapporten er en leveranse til bestillingen «Grunnlagsstudie: Pelagisk økosystem» fra Oljedirektoratet til Havforskningsinstituttet. Studien er bestilt i forbindelse med at regjeringen har igangsatt en prosess for ... -
Piscivorous fish patrol krill swarms
Kaartvedt, Stein; Røstad, Anders; Fiksen, Øyvind; Melle, Webjørn; Torgersen, Thomas; Breien, M. T.; Klevjer, Thor A. (Journal article; Peer reviewed, 2005-09-01)Dense swarms of the krill Meganyctiphanes norvegica in the Norwegian Sea were patrolled by large, piscivorous fish, which apparently use the krill swarms as feeding grounds in their hunt for planktivores. For the krill, ...