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Fine stream wood decreases growth of juvenile brown trout (Salmo trutta)
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
National Resources Institute, Finland.
University of Oulu, Finland.
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences. (River Ecology and Management Research Group)
(English)Manuscript (preprint) (Other academic)
National Category
Biological Sciences
Research subject
Biology
Identifiers
URN: urn:nbn:se:kau:diva-45653OAI: oai:DiVA.org:kau-45653DiVA: diva2:957595
Available from: 2016-09-02 Created: 2016-09-02 Last updated: 2016-09-02Bibliographically approved
In thesis
1. Fine stream wood: effects on drift and brown trout (Salmo trutta) growth and behaviour
Open this publication in new window or tab >>Fine stream wood: effects on drift and brown trout (Salmo trutta) growth and behaviour
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Stream ecosystems and their riparian zones have previously been regarded as two different ecosystems, linked through numerous reciprocal subsidies. Today, ecologists agree that the stream and the riparian zone should be regarded as one system, the stream-riparian ecosystem, which is characterised largely by the subsidies between land and water. The terrestrial subsidies to the stream affect stream-living biota in several ways, some of which are well-known while others less so. The input of wood to the stream from the riparian zone is believed to play an important role in the population dynamics of stream-living fish. In this doctoral thesis, I explore effects of fine stream wood (FW, <10 cm diameter) on wild stream-living young-of-the-year brown trout (Salmo trutta) by reporting and discussing results from laboratory, semi-natural and field experiments. My results show that the local density of drifting prey is higher in the presence of FW than in its absence, and also that young-of-the-year brown trout decrease their diurnal foraging time and prey capture success when FW is added to their habitat. I show that trout decrease their swimming activity in the presence of FW, aggregate in FW bundles, and have lower growth rates than trout without FW access. Also, the degree of sheltering in FW bundles was higher during day than at night in a study performed at low water temperatures; moreover, the presence of an ectothermic nocturnal predator (burbot, Lota lota) did not affect the degree of sheltering in FW bundles by trout. Taken together, my results indicate that young-of-the-year brown trout with access to FW bundles spend considerable amounts of time sheltering in the FW, and by doing so they miss the opportunity for higher growth and foraging rates outside of the shelter. The most probable explanation for this behaviour is that growth is traded off against survival, i.e., the predation risk is higher outside of the shelter.

Abstract [en]

Stream ecosystems and their riparian zones have previously been regarded as two different ecosystems, linked through numerous reciprocal subsidies. Today, ecologists agree that the stream and the riparian zone should be regarded as one system, the stream-riparian ecosystem, which is characterised largely by the subsidies between land and water. In this doctoral thesis, I explore one such subsidy – the input of fine stream wood (FW) to streams. Wild stream-living young-of-the-year brown trout (Salmo trutta) was chosen as study species. My results show that the local density of drifting prey is higher in the presence of FW than in its absence, and that young-of-the-year brown trout decrease their diurnal foraging time and prey capture success when FW is added to their habitat. I show that trout decrease their activity in the presence of FW, aggregate in FW bundles, and have lower growth rates than trout without FW access. Taken together, my results indicate that young-of-the-year brown trout spend considerable amounts of time in FW bundles, and by doing so they miss the opportunity for higher growth and foraging rates outside of the shelter. The most probable explanation for this behaviour is that growth is traded off against survival.

Place, publisher, year, edition, pages
Karlstad University Press, 2016. 43 p.
Series
Karlstad University Studies, ISSN 1403-8099 ; 34
Keyword
stream fish, wood, salmonid, trout, aquatic invertebrates, behaviour, sheltering
National Category
Biological Sciences
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-44537 (URN)978-91-7063-715-5 (ISBN)
External cooperation:
Public defence
2016-09-23, 9C 203, Universitetsgatan 2, Karlstad, 10:15 (English)
Opponent
Supervisors
Available from: 2016-09-02 Created: 2016-08-01 Last updated: 2016-09-02Bibliographically approved

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Enefalk, ÅsaBergman, Eva
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