English
norskBlar i forfatter "Næsje, Tor"
Viser treff 1-16 av 16
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Area use and movement patterns of wild and escaped farmed Atlantic salmon before and during spawning in a large Norwegian river
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-02-02)We compared the within-river movements and distribution of wild and escaped farmed Atlantic salmon Salmo salar before and during spawning in the Namsen river system of Central Norway. A total of 74 wild and 43 escaped farmed salmon were captured at sea, tagged with radio transmitters and released. Based on our examinations, most, if not all salmon (farmed and wild) entering the River Namsen were ... -
Atferd og spredning av rømt oppdrettslaks og villaks i Namsen og andre elver. Resultater fra merking av laks i Namsfjorden og Vikna
(Research report; Forskningsrapport, 2013-04)Vi undersøkte atferd og spredning av rømt oppdrettslaks og villaks i Namsen og andre elver i Midt-Norge i 2012. Hovedmålsettingen var å skaffe kunnskap slik at man kan gjøre sikrere beregninger av den reelle andelen rømt oppdrettslaks i lakseelver. De ulike delmålene var å: Vurdere sikkerheten i dagens metoder for beregning av andel oppdrettslaks i gytebe-stander av villaks. Sammenligne ... -
Biologiske undersøkelser i Altaelva 2005
(Research report; Forskningsrapport, 2006-05)Altaelva er ei av Norges beste elver for sportsfiske etter laks. Elva har en storvokst laksestamme, og en unik kultur og historie knyttet til laksefisket. Stortinget vedtok å utbygge og regulere elva for kraftproduksjon i 1978. Byggingen av kraftverksdammen ble igangsatt i 1983, og Alta kraftverk ble satt i drift i 1987. Det er gjennomført omfattende fiskebiologiske undersøkelser i vassdraget siden ... -
Diving behaviour of Atlantic salmon at sea: effects of light regimes and temperature stratification
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-07-04)The diving behaviour of adult Atlantic salmon Salmo salar L. post-spawners in the Norwegian and Barents Seas was monitored with pop-up satellite archival tags (PSATs) and data storage tags (DSTs). Salmon from the 3 studied populations showed similar depth use patterns: tagged specimens spent most of their time near the surface (mean of 82% of the time at depths <10 m), with occasional short deep ... -
Fish populations, gill net catches and gill net selectivity in the Lower Orange River, Namibia, from 1995 to 2001
(Research report; Forskningsrapport, 2007-01)The Orange River: The lower part of the Orange River forms the border between Namibia and South Africa from the mouth of the river and 580 km upstream. The river origins in the Lesotho Highlands, and runs for approximately 2300 km from the source to the Orange River Mouth at Oranjemund (Namibia) and Alexander Bay (South Africa), where it discharges into the Atlantic Ocean. The total Orange ... -
Fiskebiologiske undersøkelser i Altaelva 2010
(Research report; Forskningsrapport, 2011)Altaelva er ei av Norges beste elver for sportsfiske etter laks. Stortinget vedtok i 1978 å utbygge og regulere elva for kraftproduksjon. Byggingen av kraftverksdammen ble igangsatt i 1983, og Alta kraftverk ble satt i drift i 1987. Omfattende fiskebiologiske undersøkelser er gjennomført i vassdraget siden 1981. Formålet har vært å dokumentere eventuelle endringer i laksebestanden, finne årsakene ... -
Homing behaviour of Atlantic salmon (Salmo salar) during final phase of marine migration and river entry
(Journal article; Tidsskriftartikkel; Peer reviewed, 2013)Little is known about Atlantic salmon behaviour during the last phase of the marine homing migration and subsequent river entry. In this study, 56 adult Atlantic salmon in the Alta Fjord in northern Norway were equipped with acoustic transmitters. Salmon generally followed the coastline, but their horizontal distribution was also affected by wind-induced spreading of river water across the fjord. ... -
Marine depth use of sea trout Salmo trutta in fjord areas of Central Norway
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-09-15)The vertical behaviour of 44 veteran sea trout <i>Salmo trutta</i> (275–580 mm) in different marine fjord habitats (estuary, pelagic, near shore with and without steep cliffs) was documented during May–February by acoustic telemetry. The swimming depth of <i>S. trutta</i> was influenced by habitat, time of day (day v. night), season, seawater temperature and the body length at the time of tagging. ... -
Marine migration and habitat use of anadromous brown trout Salmo trutta
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-05-22)The biology and ecology of anadromous brown trout Salmo trutta at sea is poorly understood. This study provided information on spatial and temporal distribution of sea trout in the ocean. The behaviour of 115 individuals (veteran migrants, 270-700 mm) was tracked by using acoustic telemetry in a fjord system during April-September in 2012-2013. Overall, fish spent 68% of their marine residence ... -
Migratory behaviour and survival rates of wild northern Atlantic salmon (Salmo salar) post-smolts: effects of environmental factors
(Journal article; Tidsskriftartikkel; Peer reviewed, 2009-12-03)To study smolt behaviour and survival of a northern Atlantic salmon (Salmo salar) population during river descent, sea entry and fjord migration, 120 wild S. salar were tagged with acoustic tags and registered at four automatic listening station arrays in the mouth of the North Norwegian River Alta and throughout the Alta Fjord. An estimated 75% of the post-smolts survived from the river mouth, ... -
Migratory behaviour and survival rates of wild northern Atlantic salmon Salmo salar post-smolts: effects of environmental factors
(Conference object; Konferansebidrag, 2009-09-14) -
Movements of female lumpsucker Cyclopterus lumpus in a Norwegian fjord during the spawning period
(Research report; Forskningsrapport, 2007)Lumpsucker are distributed throughout the North Atlantic Ocean, and migrate considerable distances between offshore feeding areas and shallow inshore spawning areas. In July 2006, a study on the movements of female lumpsucker during the spawning period was carried out in Øksfjord, Northern Norway. Twenty fish (mean body mass 3.2 kg, range 1.5- 4.8 kg) were tagged with acoustic transmitters and ... -
Redefining the oceanic distribution of Atlantic salmon
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-10)Determining the mechanisms driving range-wide reductions in Atlantic salmon marine survival is hindered by an insufcient understanding of their oceanic ecology and distribution. We attached 204 pop-up satellite archival tags to post-spawned salmon when they migrated to the ocean from seven European areas and maiden North American salmon captured at sea at West Greenland. Individuals migrated ... -
Return migration of adult Atlantic salmon (Salmo salar L.) to northern Norway
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-09-18)The return migration of adult Atlantic salmon was investigated by analysing recaptures of individuals tagged and released as smolts in the River Altaelva and the River Halselva using a catch per unit effort approach. Although the salmon were recaptured over a large area along the coastline (from >1100 km south to>500 km northeast of their home rivers), the results indicated a relatively accurate ... -
State-dependent migratory timing of postspawned Atlantic salmon (Salmo salar)
(Journal article; Tidsskriftartikkel; Peer reviewed, 2013)Atlantic salmon (Salmo salar) often survive spawning and migrate back to the sea to feed, either shortly after spawning in autumn or the following spring. We conducted a 4-year observational field study using telemetry to evaluate the determinants of migration timing in Atlantic salmon postspawners (kelts). We found that individuals with low energy reserves migrated early to the risky but productive ... -
Trophic niche similarity among sea trout Salmo trutta in Central Norway investigated using different time-integrated trophic tracers
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-21)From 2011 to 2013, anadromous brown trout Salmo trutta (213−730 mm, total body length, LT) were collected during or shortly after their marine feeding migration at 7 different localities in central Norway. The mean volume of stomach content (%) of marine fish prey eaten by S. trutta captured in marine waters varied from 34 to 89%. There was a high prevalence (67−100%) for parasite groups potentially ...
