Browsing Brage NMBU by Author "Haraldstad, Tormod"
Now showing items 1-13 of 13
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Anthropogenic and natural size-related selection act in concert during brown trout (Salmo trutta) smolt river descent
Haraldstad, Tormod; Höglund, Erik; Kroglund, Frode; Olsen, Esben Moland; Hawley, Kate Louise; Haugen, Thrond Oddvar (Peer reviewed; Journal article, 2020)By hindering migration and inducing direct turbine mortality during downstream migration, hydropower is regarded as one of the most serious threats to anadromous salmonids. Yet, little attention has been paid to long-term ... -
Diel migration pattern of Atlantic salmon (Salmo salar) and sea trout (Salmo trutta) smolts: an assessment of environmental cues
Haraldstad, Tormod; Kroglund, Frode; Kristensen, Torstein; Jonsson, Bror; Haugen, Thrond O (Journal article; Peer reviewed, 2017)The timing of smolt migration is a key phenological trait with profound implications for individual survival during both river descent and the subsequent sea sojourn of anadromous fish. We studied relationships between the ... -
Effects of repeated short episodes of environmental acidification on Atlantic salmon (Salmo salar) from a landlocked population
Höglund, Erik; Høgberget, Rolf; Åtland, Åse; Haraldstad, Tormod; Øverli, Øyvind; Vindas, Marco A (Peer reviewed; Journal article, 2021)Chronic or repeated exposure to environmental contaminants may result in allostatic overload, a physiological situation in which the costs of coping affect long-term survival and reproductive output. Continuous measurements ... -
Empirical support for sequential imprinting during downstream migration in Atlantic salmon (Salmo salar) smolts
Haraldstad, Tormod; Forseth, Torbjørn; Olsen, Esben M.; Haugen, Thrond O.; Höglund, Erik (Peer reviewed; Journal article, 2022)The precise homing of Atlantic salmon to their natal river and spawning grounds is the foundation for locally adapted genetically differentiated populations across rivers or across river sections. A sequential imprinting ... -
Hydropower-induced selection of behavioural traits in Atlantic salmon (Salmo salar)
Haraldstad, Tormod; Haugen, Thrond Oddvar; Olsen, Esben M.; Forseth, Torbjørn; Höglund, Erik (Peer reviewed; Journal article, 2021)Renewable energy projects such as hydropower facilities contribute towards meeting the world`s growing energy demands and urgent need for mitigating climate change. However, such infrastructure has the potential to ... -
Increased precision of growth data gained by reading multiple scales from each individual of Atlantic salmon (Salmo salar)
Haraldstad, Tormod; Haugen, Thrond Oddvar; Borgstrøm, Reidar; Jonsson, Bror (Journal article; Peer reviewed, 2016)The precision of growth estimates based on fish scales often remains uncertain because of withinindividual variation in scale size and scale patterns, and also due to measurement errors. Based on scale readings of Atlantic ... -
Migratory passage structures at hydropower plants as potential physiological and behavioural selective agents
Haraldstad, Tormod; Haugen, Thrond Oddvar; Kroglund, Frode; Olsen, Esben Moland; Höglund, Erik (Peer reviewed; Journal article, 2019) -
Neuroendocrine indicators of allostatic load reveal the impact of environmental acidification in fish
Höglund, Erik; Korzan, Wayne; Åtland, Åse; Haraldstad, Tormod; Høgberget, Rolf; Mayer, Ian; Øverli, Øyvind (Peer reviewed; Journal article, 2020)When mobilized from surrounding soils and binding to gills at moderately low pH, aluminum (Al) cations can adversely affect fish populations. Furthermore, acidification may lead to allostatic overload, a situation in which ... -
Påvirkes laksesmolt av aluminium i brakkvann?Telemetriundersøkelser i Storelva i Holt, Aust-Agder,2007
Kroglund, Frode; Høgberget, Rolf; Haraldstad, Tormod; Økland, Finn; Thorstad, Eva Bonsak; Teien, Hans-Christian; Rosseland, Bjørn Olav; Salbu, Brit; Nilsen, Tom Ole; Stefansson, Sigurd Olav; Guttrup, Jim (NIVA-rapport;6245-2011, Research report, 2011)Storelva har vært fullkalket siden 1996. Kalkingen har ikke gitt den forventede økningen i fangst av laks. Vassdraget avviker således fra erfaringene man har fra andre kalka elver på Sørlandet. Flere hypoteser er ... -
Påvirkes laksesmolt av aluminium i brakkvann?Telemtriundersøkelser Storelva i Holt, Aust-Agder,2008
Kroglund, Frode; Høgberget, Rolf; Haraldstad, Tormod; Økland, Finn; Thorstad, Eva Bonsak; Teien, Hans-Christian; Rosseland, Bjørn Olav; Salbu, Brit; Nilsen, Tom Ole; Stefansson, Sigurd Olav; Guttrup, Jim (NIVA-rapport;6246-2011, Research report, 2011)Fangsten av laks i Storelva i Holt er lavere enn forventet. Flere hypoteser er forkastet. De senere årene har fokus vært på: vil aluminium i brakkvann kunne hemme smoltens utvandring fra elv til hav? I 2007 og 2008 ... -
Scale- and growth analysis of Atlantic salmon (salmo salar) caught with a bag net near the River Mandalselva, on the Skagerrak coast
Haraldstad, Tormod (Master thesis, 2011-10-03)The abundance of wild Atlantic salmon (Salmo salar) has declined since the 1970s. The major reason for the recent decline appears to be increased marine mortality. Before 1970s, the native populations of Atlantic salmon ... -
Smoltutvandring i Nidelva 2014-Utprøving av tiltak for nedvandrende smolt ved Rygene kraftverk
Haraldstad, Tormod; Guttrup, Jim; Haugen, Thrond Oddvar (Research report, 2014)Antall pre-smolt oppstrøms Rygene, 3546 (3083-4214), er lavere en hva en kunne forvente utfra antall oppvandrende gytefisk og egnet gyte- og oppvekstareal i elva. I tillegg estimeres et betydelig tap av smolt under ... -
Utredning av aktuelle kalkingstiltak i Agder
Haraldstad, Tormod; Hindar, Atle; Høgberget, Rolf; Kaste, Øyvind; Teien, Hans-Christian (NIVA-rapport, Research report, 2017)De fleste store vassdragene i Vest-Agder kalkes i dag for å sikre god nok vannkvalitet for laks og sjøørret. Blant disse er Audna, som er blitt dosererkalket siden 1985, og Mandalselva hvor det ble satt i gang storstilt ...