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Effects of large wood density on brown strout (Salmo trutta) behaviour in artificial streams
Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
Karlstad University, Faculty of Social and Life Sciences, Department of Biology.ORCID iD: 0000-0002-3191-7140
Karlstad University, Faculty of Social and Life Sciences, Department of Biology.ORCID iD: 0000-0003-2220-1615
(English)Manuscript (preprint) (Other academic)
National Category
Biological Sciences
Research subject
Biology
Identifiers
URN: urn:nbn:se:kau:diva-6902OAI: oai:DiVA.org:kau-6902DiVA: diva2:394010
Available from: 2011-02-01 Created: 2011-02-01 Last updated: 2015-11-12Bibliographically approved
In thesis
1. Forest – stream linkages: Brown trout (Salmo trutta) responses to woody debris, terrestrial invertebrates and light
Open this publication in new window or tab >>Forest – stream linkages: Brown trout (Salmo trutta) responses to woody debris, terrestrial invertebrates and light
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Forests surrounding streams affect aquatic communities in numerous ways, contributing to energy fluxes between terrestrial and lotic ecosystems. The five papers in this thesis focus on woody debris, terrestrial invertebrates and light, three factors influenced by riparian zone structure, potentially affecting streams and brown trout (Salmo trutta). The individual strength of these stressors and their interactions with each other are not well studied, and their qualitative effects may differ both spatially and temporally as well as with the size-structure of specific fish populations.

Using a combination of laboratory and field experiments, I examined the effects of woody debris, terrestrial invertebrates and light on prey availability and on the growth rates, diets and behavior of different size-classes of trout. My field experiments showed that addition of high densities of large wood affected trout growth in a positive way. This positive effect of large wood on trout growth may be related to prey abundance, as indicated by the high standing crop of aquatic macroinvertebrates on the wood. The positive effects on trout may also be related to decreased energy expenditures in wood habitats, as trout increased the ratio between numbers of prey captured and time spent active and that swimming activity and level of aggression decreased as wood densities were increased in a laboratory experiment. Terrestrial invertebrates are generally assumed to be a high quality prey resource for fish and my field experiments showed that reduction of terrestrial invertebrate inputs had a negative effect on trout growth. The availability of terrestrial prey in the stream was also coupled to trout diet and linked to growth, as fish with high growth rates had high proportions of terrestrial prey in their diets. Light, measured as PAR, did not have an effect on chlorophyll biomass, nor was there an effect on aquatic macroinvertebrates or trout. Hence, even if light levels were sufficient for increased photosynthesis, other factors such as low nutrient content may have limited the effects. Many of my results were dependent on fish-size. I observed, for example, that large trout had higher capture rates on surface-drifting terrestrial prey than small trout when prey densities were intermediate or high, but at low prey densities, the consumption of terrestrial prey by large and small trout were similar. Moreover, although large wood and terrestrial invertebrates affected growth of both small and large trout, the effects were generally more consistent for large trout.

Although changes in riparian forests typically induce an array of interacting effects that certainly call for further research, the overall conclusion from this thesis is that many of the factors I have studied have profound effects on stream biota and trout. The positive effects from large wood also propose that adding trees to streams may partly compensate for negative effects associated with riparian deforestation.

Place, publisher, year, edition, pages
Karlstad: Karlstad University, 2011. 42 p.
Series
Karlstad University Studies, ISSN 1403-8099 ; 2011:3
Keyword
Brown trout, growth, foraging, woody debris, terrestrial invertebrates, light, riparian zone, forestry, stream
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-6731 (URN)978-91-7063-335-5 (ISBN)
Public defence
2011-02-25, Andersalen, 11D 121, Karlstads universitet, Karlstad, 13:15 (English)
Opponent
Supervisors
Available from: 2011-02-01 Created: 2011-01-03 Last updated: 2011-10-25Bibliographically approved

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