English
norskBlar i forfatter "Rikardsen, Audun H."
Viser treff 21-40 av 42
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The major threats to Atlantic salmon in Norway
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-03-03)Atlantic salmon (Salmo salar) is an economically and culturally important species. Norway has more than 400 watercourses with Atlantic salmon and supports a large proportion of the world’s wild Atlantic salmon. Atlantic salmon are structured into numerous genetically differentiated populations, and are therefore managed at the population level. Long-distance migrations between freshwater and ocean ... -
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 food consumption by adult Atlantic salmon and energetic impacts of increased ocean temperatures caused by climate change
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-27)Atlantic salmon Salmo salar are experiencing widespread population declines, and reductions in growth and survival in the marine environment are contributing factors. Our aims were to estimate marine food consumption of adult salmon and to determine how energetics would be directly afected by the increased ocean temperatures associated with climate change. We tagged previous spawners on outward ... -
Marine mammal hotspots in the Greenland and Barents Seas
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-04)Environmental change and increasing levels of human activity are threats to marine mam- mals in the Arctic. Identifying marine mammal hot - spots and areas of high species richness are essential to help guide management and conservation efforts. Herein, space use based on biotelemetric tracking devices deployed on 13 species (ringed seal <i>Pusa hispida</i>, bearded seal <i>Erignathus ... -
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) -
Occurrence of emerging brominated flame retardants and organophosphate esters in marine wildlife from the Norwegian Arctic
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-10-10)To understand the exposure and potential sources of emerging brominated flame retardants (EBFR) and organophosphate esters (OPEs) in marine wildlife from the Norwegian Arctic, we investigated concentrations of EBFRs in 157 tissue samples from nine species of marine vertebrates and OPEs in 34 samples from three whale species. The samples, collected from a wide range of species with contrasting ... -
Ocean migration of pop-up satellite archival tagged Atlantic salmon from the Miramichi River in Canada
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-01-13)The ocean migration of 16 post-spawned adult Atlantic salmon [Salmo salar L.] from the Miramichi River, Canada, tagged concurrently with pop-up satellite archival tags and acoustic transmitters was reconstructed using a Hidden Markov Model. Individuals exclusively utilized areas within the Gulf of St Lawrence and the Labrador Sea, and showed little overlap with known distributions of European stocks. ... -
Ocean predation and mortality of adult Atlantic salmon
(Journal article; Peer reviewed, 2019-05-27)Predation and mortality are often difficult to estimate in the ocean, which hampers the management and conservation of marine fishes. <br>We used data from pop-up satellite archival tags to investigate the ocean predation and mortality of adult Atlantic salmon (Salmo salar) released from 12 rivers flowing into the North Atlantic Ocean. Data from 156 tagged fish revealed 22 definite predation ... -
Overlevelse, spredning og vandring i sjøen for simulert rømt lakseparr og smolt fra et landbasert settefiskanlegg
(Research report; Forskningsrapport, 2011-04)Hensikten med prosjektet var å undersøke overlevelse og spredning for parr og smolt av opp-drettslaks (Salmo salar L.) fra et landbasert settefiskanlegg (SalMar Settefisk AS, avd. Folla-foss) etter simulert rømning om høsten. Dette ble gjort ved å merke parr og smolt med akustis-ke merker for å kartlegge umiddelbar romlig og temporær spredning etter rømning, samt for å undersøke om, og eventuelt ... -
Quantitative fatty acid signature analysis reveals a high level of dietary specialization in killer whales across the North Atlantic
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-13)Quantifying the diet composition of apex marine predators such as killer whales (Orcinus orca) is critical to assessing their food web impacts. Yet, with few exceptions, the feeding ecology of these apex predators remains poorly understood. <p>Here, we use our newly validated quantitative fatty acid signature analysis (QFASA) approach on nearly 200 killer whales and over 900 potential prey to model ... -
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 ... -
Relationship between marine growth and sea survival of two anadromous salmonid fish species
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06-12)Résumé : L’étude fait état de preuves empiriques appuyant le paradigme de « croissance–survie » chez les phases marines de l’omble chevalier (Salvelinus alpinus) et de la truite de mer (Salmo trutta). Ce paradigme postule que les individus plus grands ou a` croissance plus rapide sont plus susceptibles de survivre que leurs conspécifiques plus petits ou a` croissance plus lente. Nous avons utilisé ... -
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 ... -
Revealing the full ocean migration of individual Atlantic salmon
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-02-14)Knowledge of the complete horizontal migration and vertical movements of Atlantic salmon (Salmo salar L.) during the marine phase is important for understanding the link between individual processes and population recruitment. We studied the detailed migration behaviour of six post-spawned adult Atlantic salmon from a North Norwegian river, during the entire ocean migration, by using high-resolution ... -
Seaward migrating Atlantic salmon smolts with low levels of gill Na+, K+ -ATPase activity : is sea entry delayed?
(Journal article; Tidsskriftartikkel; Peer reviewed, 2010-11-16)Two groups of migrating wild Atlantic salmon (Salmo salar) smolts caught within a 1 week interval in the River Alta, northern Norway, were tagged with acoustic transmitters and measured for gill Na+, K+ -ATPase activity in order to compare their smolt status with timing of sea entry. The first group of smolts had low levels of gill Na+, K+ -ATPase activity and resided in the lower part of the river ... -
Sluttrapport for prosjekt: "Kartlegging og testing av metoder for å redusere interaksjoner mellom fiskeri og hval" - FHF 901681
(Research report; Forskningsrapport, 2024-04-03)Spekkhoggere og knølhval i norske farvann følger den pelagiske fiskeflåten og beiter på fisken som blir samlet sammen av nøtene. Disse interaksjonene har ved flere anledninger ført til skade eller død av hval, og fangsttap og ødelagte redskap for fiskerne. Målsetningen i dette prosjektet var å kartlegge og teste utstyr og metoder som kan bidra til å redusere uønskede interaksjoner mellom spekkhoggere ... -
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 ... -
Transmission dynamics of the monogenean Gyrodactylus salaris under seminatural conditions
(Journal article; Tidsskriftartikkel; Peer reviewed, 2014-07-12)Tracking individual variation in the dynamics of parasite infections in wild populations is often complicated by lack of knowledge of the epidemiological history of hosts. Whereas the dynamics and development of Gyrodactylus salaris Malmberg, 1957, on Atlantic salmon, Salmo salar L., are known from laboratory studies, knowledge about infection development on individual wild fishes is currently sparse. ...
