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Enefalk, Å., Huusko, A., Louhi, P. & Bergman, E. (2019). Fine stream wood decreases growth of juvenile brown trout (Salmo trutta). Environmental Biology of Fishes, 1-12
Open this publication in new window or tab >>Fine stream wood decreases growth of juvenile brown trout (Salmo trutta)
2019 (English)In: Environmental Biology of Fishes, ISSN 0378-1909, E-ISSN 1573-5133, p. 1-12Article in journal (Refereed) Epub ahead of print
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.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Fine woody debris, Structure, In-stream, Shelter, Predatory refuge
National Category
Biological Sciences
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-45653 (URN)10.1007/s10641-019-00869-4 (DOI)
Note

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

Available from: 2016-09-02 Created: 2016-09-02 Last updated: 2019-04-05Bibliographically approved
Enefalk, Å. & Bergman, E. (2016). Effect of fine wood on juvenile brown trout behaviour in experimental stream channels. Ecology of Freshwater Fish, 25(4), 664-673
Open this publication in new window or tab >>Effect of fine wood on juvenile brown trout behaviour in experimental stream channels
2016 (English)In: Ecology of Freshwater Fish, ISSN 0906-6691, E-ISSN 1600-0633, Vol. 25, no 4, p. 664-673Article in journal (Refereed) 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.

Place, publisher, year, edition, pages
John Wiley & Sons, 2016
Keywords
salmonid; YOY; streams; wood; small woody debris
National Category
Ecology Biological Sciences
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-42488 (URN)10.1111/eff.12244 (DOI)000388307300015 ()2-s2.0-84938718603 (Scopus ID)
Available from: 2016-05-27 Created: 2016-05-23 Last updated: 2017-12-06Bibliographically approved
Enefalk, Å. & Bergman, E. (2016). Effects of fine wood on macroinvertebrate drift in four boreal forest streams. Hydrobiologia, 765(1), 317-327
Open this publication in new window or tab >>Effects of fine wood on macroinvertebrate drift in four boreal forest streams
2016 (English)In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 765, no 1, p. 317-327Article in journal (Refereed) 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.

Keywords
Invertebrates, Colonization, FWD, In-stream wood, Small woody debris
National Category
Biological Sciences
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-40971 (URN)10.1007/s10750-015-2423-x (DOI)000366641200022 ()
Available from: 2016-03-03 Created: 2016-03-03 Last updated: 2017-12-06Bibliographically approved
Enefalk, Å. (2016). Fine stream wood: effects on drift and brown trout (Salmo trutta) growth and behaviour. (Doctoral dissertation). Karlstad University Press
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. p. 43
Series
Karlstad University Studies, ISSN 1403-8099 ; 34
Keywords
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
Watz, J., Bergman, E., Calles, O., Enefalk, Å., Gustafsson, S., Hagelin, A., . . . Bror, J. (2015). Ice cover alters the behavior and stress level of brown trout Salmo trutta. Behavioral Ecology, 26(3), 820-827
Open this publication in new window or tab >>Ice cover alters the behavior and stress level of brown trout Salmo trutta
Show others...
2015 (English)In: Behavioral Ecology, ISSN 1045-2249, E-ISSN 1465-7279, Vol. 26, no 3, p. 820-827Article in journal (Refereed) Published
Abstract [en]

Surface ice in rivers and lakes buffers the thermal environment and provides overhead cover, protecting aquatic animals from terrestrial predators. We tested if surface ice influenced the behavior (swimming activity, aggressive encounters, and number of food items eaten) and stress level (coloration of eyes and body) of stream-living brown trout Salmo trutta at temperatures of 3–4 °C in indoor experimental flumes. We hypothesized that an individual’s resting metabolic rate (RMR, as measured by resting ventilation rate) would affect winter behavior. Therefore, groups of 4 trout, consisting of individuals with high, low, or mixed (2 individuals each) RMR, were exposed to experimental conditions with or without ice cover. Ice cover reduced stress responses, as evaluated by body coloration. Also, trout in low RMR groups had a paler body color than those in both mixed and high RMR groups. Trout increased their swimming activity under ice cover, with the highest activity found in high RMR groups. Ice cover increased the number of aggressive encounters but did not influence the number of drifting food items taken by each group. In mixed RMR groups, however, single individuals were better able to monopolize food than in the other groups. As the presence of surface ice increases the activity level and reduces stress in stream-living trout, ice cover should influence their energy budgets and production. The results should be viewed in light of ongoing global warming that reduces the duration of ice cover, especially at high latitudes and altitudes.

Place, publisher, year, edition, pages
Oxford: Oxford University Press, 2015
Keywords
aggression, climate change, energy budget, metabolic rate, winter
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-35931 (URN)10.1093/beheco/arv019 (DOI)000356585100024 ()
Available from: 2015-04-29 Created: 2015-04-29 Last updated: 2018-09-10Bibliographically approved
Enefalk, Å. (2014). Effects of fine woody debris on juvenile brown trout (Salmo trutta) and drifting invertebrates. (Licentiate dissertation). Karlstad: Karlstads universitet
Open this publication in new window or tab >>Effects of fine woody debris on juvenile brown trout (Salmo trutta) and drifting invertebrates
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In boreal forest streams, woody debris is an important habitat component. Stream invertebrates and salmonids such as brown trout benefit from in-stream wood. The studies presented in this thesis explore how drifting stream invertebrates respond to addition of fine woody debris, and how young-of-the-year (0+) brown trout behave in habitats with and without fine woody debris. The first paper reports results from a field experiment where fine woody debris was added to streams, and invertebrate drift was measured in order to detect impacts of the fine woody debris on drift density, biomass and taxon diversity. In the end of the season, the fine woody debris-affected drift samples showed higher density, biomass and taxon diversity than the control samples. In the second paper, I describe effects of fine woody debris on 0+ brown trout, studied in laboratory stream channels. Trout were tested in habitats without fine woody debris, with an intermediate fine woody debris density, and with a high fine woody debris density. Swimming activity and foraging time were significantly lower when fine woody debris was present than when it was absent. More time was spent sheltering at the high fine woody debris density than at the intermediate one. The increasing exploitation of fine woody debris for biofuel purposes should be considered in relation to the effects on brown trout and stream invertebrate habitat.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2014. p. 22
Series
Karlstad University Studies, ISSN 1403-8099 ; 2014:15
Keywords
brown trout, juvenile, stream, woody debris, invertebrates, fine woody debris
National Category
Natural Sciences
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-31672 (URN)978-91-7063-545-8 (ISBN)
Presentation
2014-04-29, 11D227, Universitetsg 2, Karlstad, 10:00 (English)
Opponent
Supervisors
Note

Artikel 1 ingick i avhandlingen som manuskript med titeln "Effects of fine wood addition on invertebrate drift in boreal forest streams". Nu publicerad.

Available from: 2014-04-07 Created: 2014-03-10 Last updated: 2017-12-06Bibliographically approved
Enefalk, Å. & Bergman, E.Effects of fine wood addition on invertebrate drift in boreal forest streams.
Open this publication in new window or tab >>Effects of fine wood addition on invertebrate drift in boreal forest streams
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Fine woody debris (FWD) is a key habitat component for stream-living organisms, but there have been few tests of its importance for macroinvertebrate drift in boreal forest streams. We experimentally investigated the effect of FWD addition on the drift fauna at seven sites in four boreal forest streams, from early June to mid-August 2011. This was done by anchoring bundles of FWD at each site and measuring drift upstream (within site control) and downstream of each bundle. We hypothesized that addition of FWD would increase drift density and biomass of stream invertebrates as well as drift taxon richness. Variation between sites was high, with site-specific minimum values of drift biomass of 0.2 - 4.1 mg wet mass/100 m3 and maximum values of 3.9 - 41.7 mg/100 m3. Despite this variation, there was a significant increase in total aquatic drift density and biomass 8 to 10 weeks after wood addition. Aquatic taxon richness in the drift also increased significantly after FWD addition. This study shows for the first time that FWD can increase drifting invertebrate density, biomass and taxon diversity in small boreal forest streams.

Keywords
fine wood, fine woody debris, stream, invertebrates, aquatic larvae
National Category
Natural Sciences
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-31670 (URN)
Available from: 2014-03-10 Created: 2014-03-10 Last updated: 2017-12-06Bibliographically approved
Enefalk, Å. & Bergman, E.Juvenile brown trout response to fine woody debris in experimental stream channels.
Open this publication in new window or tab >>Juvenile brown trout response to fine woody debris in experimental stream channels
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Changes in riparian vegetation due to forest harvesting may affect the input of fine woody debris, an important structural element, to streams. Woody debris has been shown to benefit trout populations. In-stream fine woody debris (FWD) has not been studied as extensively as large woody debris, but is probably important to smaller-sized trout. In a laboratory stream experiment we tested young-of-the-year wild brown trout, Salmo trutta, responses to three densities of fine woody debris (FWD). The trout were tested as singletons and four together. Swimming activity increased with increasing fish density and decreasing FWD density. Foraging decreased and time spent in FWD increased with increasing FWD density. Aggressiveness was lowest in intermediate FWD density. Our study shows that FWD impact on trout is related to fish rank, fish density and FWD density, and that juvenile trout response to fine WD is different from the response to large WD reported by others.

Keywords
fine woody debris, brown trout, juvenile, streams
National Category
Natural Sciences
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-31671 (URN)
Available from: 2014-03-10 Created: 2014-03-10 Last updated: 2017-12-06Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-7160-1290

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