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Spade, Erik, 2011. Pre-spawning habitat selection of subarctic brown trout (Salmo trutta L.) in the river Vindelälven, Sweden. Second cycle, A1E. Umeå: SLU, Dept. of Wildlife, Fish and Environmental Studies

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Abstract

Habitat selection of migratory brown trout at the upper reaches of River Vindelälven, was
studied in September during the pre-spawning period. The fish migrate from down- or
upriver lakes for spawning in the river and data was collected by habitat mapping and
radio-telemetry. Habitat selection of fish was analysed with preference curves and
statistical modelling, using the physical variables; depth, stream velocity and streambed
substrate. Preference curves were derived by comparing fish habitat use with their nearby
available environment while the statistical modelling aimed to answer three main questions.
1) Do the trout have a specific preference of depth, water velocity and streambed substrate?
2) Is there any difference in habitat selection between sexes? 3) Is there a shift in habitat
selection over time? The preference curves indicated that trout favored water depths of 1-2
m, velocity compositions characterized as glides (c. 0.2-0.4 m s-1), both fine (0.02-2 mm)
and large (>200 mm) substrate compositions. The overall habitat selection of fish was
significantly influenced by all three investigated physical variables. Stream velocity was the
only factor statistically segregating females and males in habitat selection, where males
used higher velocity areas. No shifts in habitat selection over the one month study period
were found. The complexity of streams and correlations between variables often results in
difficulties to evaluate fish habitat preferences and consequently future challenges lies in
the development of models accounting for a wider range of abiotic and biotic factors.

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Habitatval hos vandrande öring, med sitt huvudsakliga utbredningsområde i övre delarna av
Vindelälven, studerades under september en månad innan lek. Data på djup, vattenhastighet
och bottensubstrat samlades in genom biotopkartering, och telemetristudier visade fiskens
ståndplatsval. Öringarnas habitatval analyserades med preferenskurvor, baserade på data av
utnyttjande och tillgång av olika habitat, samt statistisk modellering baserat på tre frågor. 1)
Har öring en specifik preferens för djup, vattenhastighet och bottensubstrat? 2) Finns det
någon skillnad i habitatval mellan könen? 3) Finns det skillnader i val av habitat över tid?
Preferenskurvorna indikerade att öringen föredrog djup av 1-2 m, områden med ett
dominerande inslag av svagt strömmande vatten (c. 0.2-0.4 m s-1), samt bottnar med både
fina (0.02-2 mm) och grova (>200 mm) sammansättningar av substrat. Alla tre variabler
inverkade signifikant på fiskens habitatval. Vattenhastighet var den enda faktorn som
statistiskt skilde könens val av habitat, då hanar föredrog en högre hastighet än honor. Inga
skiften i habitatval i relation till tid, över den månad som studien pågick, var möjliga att
urskilja. Komplexiteten i strömmande vatten och en korrelation mellan olika variabler
resulterar ofta i svårigheter i att skatta fiskens habitatpreferens, där framtida utmaningar
ligger i att utveckla modeller som kan analysera en större mängd abiotiska samt biotiska
data.

Main title:Pre-spawning habitat selection of subarctic brown trout (Salmo trutta L.) in the river Vindelälven, Sweden
Authors:Spade, Erik
Supervisor:Rivinoja, Peter and Hellström, Gustav
Examiner:Magnhagen, Carin
Series:Examensarbete i ämnet biologi
Volume/Sequential designation:2011:1
Year of Publication:2011
Level and depth descriptor:Second cycle, A1E
Student's programme affiliation:SY001 Forest Science - Master's Programme 300 HEC
Department:(S) > Dept. of Wildlife, Fish and Environmental Studies
Keywords:mapping, stream, depth, velocity, substrate, preference, radio-telemetry, Vindelälven
URN:NBN:urn:nbn:se:slu:epsilon-s-14
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-s-14
Subjects:Aquatic ecology
Language:English
Deposited On:07 Apr 2011 08:25
Metadata Last Modified:20 Apr 2012 14:18

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