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Winter sheltering by juvenile brown trout (Salmo trutta): Effects of stream wood and an instream ecothermic predator
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences. (Naturresurs rinnande vatten)
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences. (Naturresurs rinnande vatten)ORCID iD: 0000-0002-4417-6636
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences. (Naturresurs rinnande vatten)ORCID iD: 0000-0002-3191-7140
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.ORCID iD: 0000-0003-2220-1615
2017 (English)In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 62, no 1, 111-118 p.Article in journal (Refereed) Published
Abstract [en]

In boreal streams, juvenile salmonids spend substantial amounts of time sheltering in the streambed and in stream wood, presumably as a means of protection against the physical environment and from terrestrial endothermic predators. Relatively little is known about sheltering by salmonids in response to instream ectothermic predators.We tested the effects of burbot (Lota lota) on the winter sheltering behaviour of PIT-tagged 0+ brown trout (Salmo trutta) in daylight and darkness. Sheltering in the streambed by trout was studied in the presence and absence of fine wood bundles.We found that the use of streambed and fine wood was lower in darkness than in daylight. Availability of fine wood significantly decreased sheltering in the streambed, and this effect was more pronounced in daylight than in darkness. The presence of a burbot significantly decreased sheltering in the streambed, had no effect on use of fine wood and resulted in a higher number of exposed trout.Our results indicate that juvenile brown trout decrease streambed sheltering in response to a burrowing, ectothermic predator.

Place, publisher, year, edition, pages
John Wiley & Sons, 2017. Vol. 62, no 1, 111-118 p.
Keyword [en]
cover, lotic, predator avoidance, small woody debris, substratum
National Category
Ecology
Research subject
Biology
Identifiers
URN: urn:nbn:se:kau:diva-45641DOI: 10.1111/fwb.12854ISI: 000390146000010OAI: oai:DiVA.org:kau-45641DiVA: diva2:957593
Available from: 2016-09-02 Created: 2016-09-02 Last updated: 2017-08-10Bibliographically 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)
Public defence
2016-09-23, 9C 203, Universitetsgatan 2, Karlstad, 10:15 (English)
Opponent
Supervisors
Note

Artikel 3 publicerades i avhandlingen som manuskript med samma titel.

Available from: 2016-09-02 Created: 2016-08-01 Last updated: 2017-08-10Bibliographically approved

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Enefalk, ÅsaWatz, JohanGreenberg, LarryBergman, Eva
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