Cristin-resultat-ID: 1969327
Sist endret: 5. januar 2022, 14:49
Resultat
Mastergradsoppgave
2021

River migration of sea trout Salmo trutta in River Beiarelva, Northern Norway

Bidragsytere:
  • Nanna Norderud

Utgiver/serie

Utgiver

NTNU Vitenskapsmuseet

Om resultatet

Mastergradsoppgave
Publiseringsår: 2021
Antall sider: 49

Klassifisering

Fagfelt (NPI)

Fagfelt: Biovitenskap
- Fagområde: Realfag og teknologi

Beskrivelse Beskrivelse

Tittel

River migration of sea trout Salmo trutta in River Beiarelva, Northern Norway

Sammendrag

Sea trout (Salmo trutta) return to the river for spawning and often also for overwintering, and unsuccessful river migration can threaten the population viability. The present thesis investigated the river migration of 44 veteran sea trout in River Beiarelva in Northern Norway. The sea trout were tracked for one year (August 2020 - August 2021), with main focus on the autumn migration in 2020. Acoustic telemetry was used to assess individual migration patterns between the tidal influenced stretch and the upstream freshwater stretch of the river. Individual’s total body length, body condition factor and sex were linked to behavioural metrics to evaluate if these characteristics could explain the observed behaviour. Upstream migrants entered the freshwater stretch above the tidal zone between 19 August and 28 September, consistent with the peak of upstream migrants in other northern sea trout populations. From August to December, the sea trout spent on average significant less time in the upstream freshwater zone of the river (mean = 41 days) than in the tidal influenced zone (mean = 55 days). The majority of the tagged sea trout (75%) entered the upstream freshwater stretch, probably for spawning. Larger sea trout, sea trout in better body condition and males, in particular, were more likely to enter freshwater than smaller individuals, individuals in poorer body condition and females. This could likely be explained by a higher proportion of immature individuals among the smaller sea trout, sea trout in poorer body condition and, particularly, among females. The downstream migration from the upstream freshwater stretch to the tidal influenced waters occurred mainly between 2 October and 21 November (n = 22), although six sea trout descended over winter (December – April). The relatively shorter freshwater residence suggest that the tidal zone is a favourable habitat to reside in between August and December, likely due to unfavourable conditions in the upstream freshwater stretch and/or better growth opportunities in the tidal influenced stretch. Sea trout were detected on all receivers deployed in the anadromous stretch of the river, except the receiver deployed farthest upstream in the tributary Tollåga. Total body length, body condition factor and sex had limited effects on timing of upstream migration, migratory distance in the river, timing of downstream migration and freshwater residence time, suggesting that other intrinsic or environmental factors, not included in this thesis, could be important for the autumn river migrations of sea trout. This thesis highlights the importance of tidal influenced parts of rivers for sea trout populations, and implies that the species may be especially susceptible to habitat alternations and fishing pressure in the lower parts of rivers.

Bidragsytere

Nanna Norderud

  • Tilknyttet:
    Forfatter
    ved Institutt for naturhistorie ved Norges teknisk-naturvitenskapelige universitet
Aktiv cristin-person

Jan Grimsrud Davidsen

  • Tilknyttet:
    Veileder
    ved Institutt for naturhistorie ved Norges teknisk-naturvitenskapelige universitet

Sindre Håvarstein Eldøy

  • Tilknyttet:
    Veileder
    ved Institutt for naturhistorie ved Norges teknisk-naturvitenskapelige universitet
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