The paper “Winter sheltering by juvenile brown trout (Salmo trutta) – effects of stream wood and an instream ectothermic predator” by Åsa Enefalk, Johan Watz, Larry Greenberg and Eva Bergman was recently published in the journal Freshwater Biology. The paper presents a study on the sheltering behavior of the juvenile trout in presence and absence of burbot and bundles of stream food. In the abstract the authors write:

1. 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.
2. 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.
3. 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.
4. Our results indicate that juvenile brown trout decrease streambed sheltering in response to a burrowing, ectothermic predator.

Read the paper here. If you don’t have access to the journal’s content, email any of the authors.

Today Åsa Enefalk successfully defended her PhD-thesis ”Fine stream wood – Effects on drift and brown trout (Salmo trutta) growth and behavior”. Theopponent was Stanley Gregory from Oregon State University whereas the grading committee consisted of Teppo Vehanen, Natural Resources Institute Finland, Ingrid Ahnesjö, Uppsala University, and Erik Pettersson, Swedish University of Agriculture.

Åsa Enefalk’s supervisors during her PhD were Eva Bergman, Anders NIlsson and Raimo Neergaard

The thesis is available here. Contact Åsa Enefalk for individual papers.

Dr. Åsa Enefalk defending her thesis.

Åsa Enefalk spikar traditionsenligt upp sin avhandling på väggen vid universitetets entré.

Idag spikade Åsa Enefalk, doktorand vid Karlstads Universitet, sin doktorsavhandling “Fine stream wood – Effects on drift and brown trout (Salmo trutta) growth and behavior”. Åsa kommer att försvara sin avhandling fredagen den 23 september kl. 10:15 i Nyqvistsalen, 9C 203. Alla är välkomna!

Stanley Gregory från Oregon State University kommer att vara opponent medan betygskommittén består av Teppo Vehanen, Natural Resources Institute Finland, Ingrid Ahnesjö, Uppsala universitet, och Erik Pettersson, SLU.

Imorgon, tisdagen den 23 Augusti, kommer Åsa Enefalk, doktorand vid Karlstads Universitet, ge ett seminarium med titeln “Fine stream wood – effects on drift and brown trout (Salmo trutta) growth and behaviour”. Seminariet ges klockan 13:30 i sal 5F416 på Karlstads universitet. Alla är välkomna!

En ung öring gömmer sig bland fin död ved (foto: Anders Tedeholm)

Under förra veckan organiserades “American Fisheries Society – 145th Annual Meeting” i Portland, Oregon, USA. Ett brett spektrum av fiskforskning presenterades och diskuterades. Förutom en stor mängd amerikaner var även många internationella forskare på plats. Från NRRV och Karlstads Universitet närvarade och presenterade Larry Greenberg, Eva Bergman, Anna Hagelin, Åsa Enefalk och Johan Watz. Följ länkar nedan för att läsa deras abstrakt eller browsa och sök bland konferensens alla presentationer och deltagare här.

• Larry Greenberg: Post-Spawning Survival and Downstream Passage of Landlocked Atlantic Salmon in a Regulated River
• Eva Bergman: Downstream Migration of Atlantic Salmon – Possibilities for Wild Smolts and Quality of Reared Smolts
• Anna Hagelin: Spawning Migration of Wild and Supplementary Stocked Landlocked Atlantic Salmon (Salmo salar)
• Åsa Enefalk: Effect of in-Stream Wood on Juvenile Trout Growth and Behaviour
• Johan Watz: Winter Behavior of Brown Trout: The Presence of Ice Cover Influences Activity, Stress and Growth

En ung öring bland fin ved (foto: Anders Tedeholm)

Den vetenskapliga artikeln “Effect of fine wood on juvenile brown trout behaviour in experimental stream channels” av Åsa Enefalk och Eva Bergman, publicerades nyligen i tidskriften Ecology of Freshwater Fish. Artikeln presenterar en studie där författarna undersökt unga öringars beteende i strömakvarier med olika mängder fin ved. I artikelns abstract sammanfattar författarna studien:

“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.”

Ladda ner artikeln här. Har du inte tillgång till tidskriftens innehåll men ändå vill läsa artikeln, kontakta någon av författarna.

Horrsjöälven där två av försökets lokaler återfinns.

Den vetenskapliga artikeln “Effects of fine wood on macroinvertebrate drift in four boreal forest streams” av Åsa Enefalk och Eva Bergman har publicerats i tidskriften Hydrobiologia. Artikeln presenterar forskning om hur fin ved i skogsvattendragen påverkar mängden driftande macroinverterbrater. I abstraktet skriver författarna:

“Most studies of stream wood have focused on pieces ≥0.1 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.”

Ladda ner artiklen här. Har du ej tillgång till tidskriftens innehåll, skriv till någon av författarna.

Idag spikade Åsa Enefalk sin licentiat avhandling med titeln “Effects of fine woody debris on juvenile brown trout (Salmo trutta) and drifting invertebrates”. Avhandlingen kan läsas på DIVA. Åsa kommer att hålla sin licentiat föreläsning den 29:e april, kl 10.00, i sal 11D 227. Alla är välkomna!