Browsing Brage IMR by Author "Axelsen, Bjørn Erik"
Now showing items 1-17 of 17
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Acoustic observations of dusky dolphins Lagenorhynchus obscurus hunting Cape horse mackerel Trachurus capensis off Namibia
Bernasconi, Matteo; Nøttestad, Leif; Axelsen, Bjørn Erik; Krakstad, Jens-Otto (Journal article; Peer reviewed, 2011-05-16)Predator–prey interactions of mammals and their fish prey in marine ecosystems are rarely identified and recorded. We document for the first time the underwater behaviour of hunting dusky dolphins Lagenorhynchus obscurus ... -
Acoustic observations of jellyfish in the Namibian Benguela
Brierley, Andrew S.; Axelsen, Bjørn Erik; Buecher, Emmanuelle; Sparks, Conrad A. J.; Boyer, Helen; Gibbons, Mark J. (Journal article; Peer reviewed, 2001-01-26)Multi-frequency acoustic data (18, 38 and 120 kHz) were collected in conjunction with pelagic trawl sampling for gelatinous macrozooplankton during a cruise to the Namibian Benguela in September 1999. Sampling focused ... -
An evaluation of the bottom trawl surveys in the Benguela Current Large Marine Ecosystem
Axelsen, Bjørn Erik; Johnsen, Espen (Journal article; Peer reviewed, 2014-07-02)Demersal fish, shrimp and cephalopod assemblages on the continental shelves and slopes off Angola, Namibia and the southern and western coasts of South Africa have been monitored in terms of fisheries-independent trawl ... -
Await in the pelagic: herring compromising reproduction and survival within a vertically split school
Axelsen, Bjørn Erik; Misund, Ole Arve; Fernö, Anders; Nøttestad, Leif; Johannessen, Arne (ICES CM documents, Working paper, 1998) -
‘Await’ in the pelagic: dynamic trade-off between reproduction and survival within a herring school splitting vertically during spawning
Axelsen, Bjørn Erik; Nøttestad, Leif; Fernö, Anders; Johannessen, Arne; Misund, Ole Arve (Journal article; Peer reviewed, 2000-10-19)Spatio-temporal aspects of spawning behaviour were investigated in a single school of Norwegian spring-spawning herring Clupea harengus, and are explained by changes in the relative importance of reproduction, predation ... -
Impact of herring spawning behaviour on acoustic abundance estimates
Skaret, Georg; Fernö, Anders; Nøttestad, Leif; Johannessen, Arne; Axelsen, Bjørn Erik (ICES CM documents, Working paper, 2001)Spawning dynamics of Norwegian spring spawning herring was studied in south western Norway 29 March to 3 April 2000 using hydroacoustics. The horizontal distribution of the spawning layers shifted in a south-easterly ... -
In situ of Cape horse mackerel (Trachurus capensis)
Axelsen, Bjørn Erik (ICES CM Documents;1999/J:4, Working paper, 1999)The acoustical target strength (TS) of Cape horse mackerel (Trachurus capensis) was measured in situ at 38 kHz using a submersible split beam transducer in combination with a SIMRAD EK 500 echosounder. The transducer ... -
Migration patterns in Norwegian spring-spawning herring: why young fish swim away from the wintering area in late summer
Kvamme, Cecilie; Nøttestad, Leif; Fernö, Anders; Misund, Ole Arve; Dommasnes, Are; Axelsen, Bjørn Erik; Dalpadado, Padmini; Melle, Webjørn (Journal article; Peer reviewed, 2003-03-04)Norwegian spring-spawning herring Clupea harengus make extensive feeding migrations in the Norwegian Sea during summer. At the end of the feeding season herring may meet conflicting demands between moving to areas with ... -
Pinging down the food web: multi-frequency acoustic discrimination of jellyfish and fish
Lynam, Christopher P.; Brierley, Andrew S.; Axelsen, Bjørn Erik (ICES CM Documents;2004/R:6, Working paper, 2004)Jellyfish are gaining increasing prominence in many pelagic marine ecosystems worldwide. It has been argued that jellyfish-dominated communities will be the end-point in ecosystems perturbed by high fishing effort, and ... -
Schooling dynamics of spawning herring (Clupea harengus L.) in a bay in South-Western Norway
Axelsen, Bjørn Erik; Misund, Ole Arve (PINRO-IMR Symposium, Conference object, 1997)The schooling dynamics of hening (Clupea harengta L.) was investigated during spawning in Raunefjord, south-westem Norway in 1994. A single school of Nonvegian spring spawning hening WSS) was tracked during daytime over ... -
A sonar study of the migration pattern of Norwegian spring-spawning herring (Clupea harengus L.) in July
Kvamme, Cecilie; Nøttestad, Leif; Fernö, Anders; Misund, Ole Arve; Dommasnes, Are; Axelsen, Bjørn Erik (ICES CM documents, Working paper, 2000)About 700 schools of Norwegian spring-spawning herring (Clupea harengus L.) were tracked by multi-beam sonar during transect surveys in the Norwegian Sea in July 1995 and 1996. This herring stock usually concentrates in ... -
Spatial and temporal overlap and trophic interactions between Atlantic Saithe (Pollachius virens) and Norwegian spring spawning herring (Clupea harengus) on herring spawning grounds
Slotte, Aril; Runde, Arne; Skaret, Georg; Axelsen, Bjørn Erik; Fernö, Anders; Johannessen, Arne; Nøttestad, Leif; Øvredal, Jan Tore (ICES CM documents, Working paper, 2005)Atlantic saithe (Pollachius virens) and Norwegian spring-spawning herring (Clupea harengus) represent two of the most abundant and ecologically important fish species in the Northeast Atlantic. The two species co-occur ... -
Toktrapport [7/7 - 2/8, 1995]
Monstad, Terje; Holm, Marianne; Holst, Jens Christian; Axelsen, Bjørn Erik; Nøttestad, Leif ([Toktrapport/Havforskningsinstituttet];, Working paper, 1995-09-08) -
Toktrapport fra forsøkene med redskapsmodifikasjoner
Jørgensen, Terje; Løkkeborg, Svein; Palm, Anne Christine Utne; Ulvestad, Bente Hoddevik; Aasen, Asbjørn; Tysseland, Anne-Britt Skar; Axelsen, Bjørn Erik (Toktrapport/Havforskningsinstituttet;Nr. 6 - 2012, Working paper, 2012) -
Toktrapport fra forsøkene med redskapsmodifikasjoner. Tokt utført i juni og august 2013
Palm, Anne Christine Utne; Løkkeborg, Svein; Ulvestad, Bente Hoddevik; Axelsen, Bjørn Erik; Jørgensen, Terje (Rapport fra Havforskningen;Nr. 33-2013, Working paper, 2013) -
Towards the acoustic estimation of jellyfish abundance
Brierley, Andrew S.; Boyer, D.; Axelsen, Bjørn Erik; Lynam, Christopher P.; Sparks, Conrad A. J.; Boyer, Helen; Gibbons, Mark J. (Journal article; Peer reviewed, 2005-06-23)Acoustic target strengths (TSs) of the 2 most common large medusae, Chrysaora hysoscella and Aequorea aequorea, in the northern Benguela (off Namibia) have previously been estimated (at 18, 38 and 120 kHz) from acoustic ... -
Utredning av Havforskningsinstituttets framtidige infrastrukturbehov for innhenting av marine data
Huse, Geir; Nieuwejaar, Per; Bruvoll, Annegrete; Godø, Olav Rune; Taranger, Geir Lasse; Nilssen, Kjell Tormod; Knutsen, Jan Atle; Axelsen, Bjørn Erik; Ibenholdt, Karin (Rapport fra Havforskningen;17-2015, Research report, 2015)