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Fine stream wood: effects on drift and brown trout (Salmo trutta) growth and behaviour
Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper. (Naturresurs Rinnande Vatten)ORCID-id: 0000-0001-7160-1290
2016 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Karlstad University Press, 2016. , s. 43
Serie
Karlstad University Studies, ISSN 1403-8099 ; 34
Nyckelord [en]
stream fish, wood, salmonid, trout, aquatic invertebrates, behaviour, sheltering
Nationell ämneskategori
Biologiska vetenskaper
Forskningsämne
Biologi
Identifikatorer
URN: urn:nbn:se:kau:diva-44537ISBN: 978-91-7063-715-5 (tryckt)OAI: oai:DiVA.org:kau-44537DiVA, id: diva2:950545
Disputation
2016-09-23, 9C 203, Universitetsgatan 2, Karlstad, 10:15 (Engelska)
Opponent
Handledare
Anmärkning

Artikel 3 publicerades i avhandlingen som manuskript med samma titel.

Tillgänglig från: 2016-09-02 Skapad: 2016-08-01 Senast uppdaterad: 2017-08-10Bibliografiskt granskad
Delarbeten
1. Effects of fine wood on macroinvertebrate drift in four boreal forest streams
Öppna denna publikation i ny flik eller fönster >>Effects of fine wood on macroinvertebrate drift in four boreal forest streams
2016 (Engelska)Ingår i: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 765, nr 1, s. 317-327Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Most studies of stream wood have focused on pieces a parts per thousand yen0.1 m diameter. However, this approach may overlook an important feature of small streams, where wood < 0.1 m can constitute the majority of wood pieces. We examined the effect of fine wood (FW) on local drift of stream macroinvertebrates. The study was carried out at seven sites in four boreal forest streams, from early June to mid-August 2011. This was done by anchoring bundles of FW at each site and measuring drift upstream and downstream of each bundle. We hypothesized that FW would increase drift density, biomass and diversity of aquatic invertebrates. Ten weeks after FW addition, aquatic drift density was higher downstream than upstream of FW bundles, while drift biomass and drift diversity did not differ significantly downstream and upstream of FW.

Nyckelord
Invertebrates, Colonization, FWD, In-stream wood, Small woody debris
Nationell ämneskategori
Biologiska vetenskaper
Forskningsämne
Biologi
Identifikatorer
urn:nbn:se:kau:diva-40971 (URN)10.1007/s10750-015-2423-x (DOI)000366641200022 ()
Tillgänglig från: 2016-03-03 Skapad: 2016-03-03 Senast uppdaterad: 2019-07-10Bibliografiskt granskad
2. Effect of fine wood on juvenile brown trout behaviour in experimental stream channels
Öppna denna publikation i ny flik eller fönster >>Effect of fine wood on juvenile brown trout behaviour in experimental stream channels
2016 (Engelska)Ingår i: Ecology of Freshwater Fish, ISSN 0906-6691, E-ISSN 1600-0633, Vol. 25, nr 4, s. 664-673Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

In-stream wood can increase shelter availability and prey abundance for stream-living fish such as brown trout, Salmo trutta, but the input of wood to streams has decreased in recent years due to harvesting of riparian vegetation. During the last decades, fine wood (FW) has been increasingly used for biofuel, and the input of FW to streams may therefore decrease. Although effects of in-stream FW have not been studied as extensively as those of large wood (LW), it is probably important as shelter for small-sized trout. In a laboratory stream experiment, we tested the behavioural response of young-of-the-year wild brown trout to three densities of FW, with trout tested alone and in groups of four. Video recordings were used to measure the proportion of time allocated to sheltering, cruising and foraging, as well as the number of aggressive interactions and prey attacks. Cruising activity increased with decreasing FW density and was higher in the four-fish groups than when fish were alone. Foraging decreased and time spent sheltering in FW increased with increasing FW density. Our study shows that juvenile trout activity is higher in higher fish densities and that trout response to FW is related to FW density and differs from the response to LW as reported by others. © 2015 John Wiley & Sons A/S.

Ort, förlag, år, upplaga, sidor
John Wiley & Sons, 2016
Nyckelord
salmonid; YOY; streams; wood; small woody debris
Nationell ämneskategori
Ekologi Biologiska vetenskaper
Forskningsämne
Biologi
Identifikatorer
urn:nbn:se:kau:diva-42488 (URN)10.1111/eff.12244 (DOI)000388307300015 ()2-s2.0-84938718603 (Scopus ID)
Tillgänglig från: 2016-05-27 Skapad: 2016-05-23 Senast uppdaterad: 2017-12-06Bibliografiskt granskad
3. Winter sheltering by juvenile brown trout (Salmo trutta): Effects of stream wood and an instream ecothermic predator
Öppna denna publikation i ny flik eller fönster >>Winter sheltering by juvenile brown trout (Salmo trutta): Effects of stream wood and an instream ecothermic predator
2017 (Engelska)Ingår i: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 62, nr 1, s. 111-118Artikel i tidskrift (Refereegranskat) 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.

Ort, förlag, år, upplaga, sidor
John Wiley & Sons, 2017
Nyckelord
cover, lotic, predator avoidance, small woody debris, substratum
Nationell ämneskategori
Ekologi
Forskningsämne
Biologi
Identifikatorer
urn:nbn:se:kau:diva-45641 (URN)10.1111/fwb.12854 (DOI)000390146000010 ()
Tillgänglig från: 2016-09-02 Skapad: 2016-09-02 Senast uppdaterad: 2019-07-10Bibliografiskt granskad
4. Fine stream wood decreases growth of juvenile brown trout (Salmo trutta)
Öppna denna publikation i ny flik eller fönster >>Fine stream wood decreases growth of juvenile brown trout (Salmo trutta)
2019 (Engelska)Ingår i: Environmental Biology of Fishes, ISSN 0378-1909, E-ISSN 1573-5133, Vol. 102, nr 5, s. 759-770Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

In this study, the growth rate, gut fullness, diet composition and spatial distribution of brown trout was compared between artificial channels with and without fine wood (FW). Access to FW resulted in significantly lower brown trout growth rates over the study period from late summer to early winter as water temperatures declined from 17 °C to 1 °C. Access to FW resulted in minor differences in occurrence of the most common taxa found in brown trout diets, except for chironomid larvae which were found in c. 60% of the brown trout guts from control treatments but in only 30% of the guts from FW treatments in early winter. Diet consisted primarily of case-bearing and free-living Trichoptera larvae, Asellus, chironomid and Ephemeroptera larvae. Brown trout gut fullness was not significantly affected by access to FW bundles. Brown trout aggregated among FW but were more evenly distributed in channels lacking it. Our results suggest that juvenile brown trout use FW as a shelter at a wide range of water temperatures, and that this behaviour may result in reduced growth rates during their first fall and the onset of their first winter. We also show that prey availability and the composition of brown trout diet changes from late summer to early winter and that FW has a small but significant effect on brown trout diet composition.

Ort, förlag, år, upplaga, sidor
Springer, 2019
Nyckelord
Fine woody debris, Structure, In-stream, Shelter, Predatory refuge
Nationell ämneskategori
Biologiska vetenskaper
Forskningsämne
Biologi
Identifikatorer
urn:nbn:se:kau:diva-45653 (URN)10.1007/s10641-019-00869-4 (DOI)000468519700008 ()
Anmärkning

Artikeln publicerad som manuskript i Enefalks doktorsavhandling Fine stream wood: effects on drift and brown trout (Salmo trutta) growth and behaviour.

Tillgänglig från: 2016-09-02 Skapad: 2016-09-02 Senast uppdaterad: 2019-06-12Bibliografiskt granskad

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