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Finns det bevis för täthetsberoende tillväxt eller överlevnad hos ettårig öring i Dammån och dess biflöden?
Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
2018 (Swedish)Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesisAlternative title
Is there evidence fordensity-dependent growth or survival of brown trout parr in river Dammån andits tributaries? (English)
Abstract [sv]

Denna studie genomfördes med syfte att undersöka om det fanns korrelationer mellan 0+-öring (Salmo trutta L.) år x och 1+-öring år x+1 i elva uppväxtlokaler i älven Dammån-Storån och dess biflöden Lekarån och Bastuån år 1995–2010. Detta utfördes i form av två regressionsanalyser för att se om det fanns ett funktionellt samband avseende (i) täthet 0+ och medellängd av 1+, samt (ii) täthet 0+ och täthet av 1+ inom samma lokal, med 1+-öring som beroende variabel. Därefter gjordes tre envägs-ANOVA för att klarlägga om det (i) förelåg skillnader i medellängd på 0+-öring mellan dessa elva uppväxtlokaler under samma tidsintervall, (ii) om det fanns skillnader i medellängd mellan år, samt (iii) om det fanns skillnader i maximala 0+-längder mellan lokalerna.

Resultatet visade att det fanns en svagt negativ korrelation mellan täthet av 0+- och medellängd av 1+-öring året därpå, samt en svag positiv korrelation mellan täthet av 0+- och 1+-öring. Variationsanalysen av medellängder på 0+-öring visade signifikanta skillnader i medellängd mellan lokalerna. Variationsanalysen av medellängder mellan årtal visade en knapp signifikant skillnad, och det fanns slutligen en signifikant skillnad i 0+-individers maximala längd mellan lokaler.

Abstract [en]

This study examined whether there is any evidence for density-dependent growth and survival of juvenile brown trout (Salmo trutta L.) in eleven nursery locals in the river Dammån-Storån and its tributaries Lekarån and Bastuån 1995-2010. Regression analyses were used to test for correlations between (i) density of 0+ and mean length of 1+ and (ii) density of 0+ and density of 1+. Thereafter three one-way ANOVAs were used to test for (i) any differences in mean length of underyearlings among these eleven locals during the same time period, (ii) differences in mean length between years and (iii) differences in maximum length of 0+ among locals.

The results revealed weak negative correlations between density of 0+ and mean length of 1+,  and weak positive correlations between density of 0+- and 1+-brown trout. The analysis of variance on mean length of 0+ showed significant differences in mean length between the locals. The ANOVA on differences in mean length between years showed slight differences, and the ANOVA on differences in maximum length of 0+ showed significant differences. This study suggests that there is not strong evidence for density dependence in these populations, and that local conditions in time and space are important determinants of fish growth.

Place, publisher, year, edition, pages
2018. , p. 15
Keywords [sv]
Täthetsberoende, densitet, öring, Dammån
National Category
Ecology
Identifiers
URN: urn:nbn:se:kau:diva-70409OAI: oai:DiVA.org:kau-70409DiVA, id: diva2:1268118
Subject / course
Biology
Educational program
Biology programme, 180 hp
Supervisors
Examiners
Available from: 2019-08-20 Created: 2018-12-04 Last updated: 2019-08-20Bibliographically approved

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