Johan Watz contributed the cover photo.

The paper “Ice cover affects the growth of a stream-dwelling fish”  by Johan Watz, Eva Bergman, John Piccolo and Larry Greenberg was published as the cover article in the May issue of the scientific journal Oecologia. The journal presents its issue and the paper:

“Winter conditions are believed to play an important role in the population dynamics of northern temperate stream fi sh, challenging the ability of fi sh to physiologically and behaviourally adapt. In this issue, Watz et al. show that brown trout (Salmo trutta) that spent the winter under ice cover grew more and used a broader range of habitats than trout in uncovered stream sections. These results indicate that the presence of surface ice may function as overhead cover against terrestrial piscivores and improve the energetic status of stream fish during winter.”

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

The stream aquaria with ice cover.

The Lab and Stream, a project that “strives to bridge the gap between anglers and academics”, has written about NRRV:s lab research on winter ecoology of brown trout:

“I think that one of the reasons that people are fascinated with fish is that they are hard to observe. Fish live in a world that is difficult to visit and largely mysterious to us air breathers, even though that world might be only a few feet underneath your boat or dock. While the underwater world might seem like an alternate dimension, the under ice world is even more distant from people’s understanding. Anyone that has stood on a frozen lake has wondered what is going on underneath them, but under ice behavior is notoriously hard to study because it’s cold and dark down there.

A cool new study by researchers from Sweden and Norway has shed some light on what trout are doing under the ice. They built stream channels in the lab that had a window on one side (to observe the fish) and added ice cover to the top of the channels to simulate a frozen river environment. In each channel they added 4 brown trout and observed their feeding and swimming behaviour…”

Read the full article at labandstream.wordpress.com.

Johan Watz led the experiment described and focoused his PhD on the winter ecololgy of salmonids. Read his thesis here. Links to the papers included are available in this blog post.

Under den gångna veckan har Johan Watz spikat sin avhandling “Salmonid behaviour under winter conditions”. Kappan kan läsas online här. Avhandlingens publicerade artiklar är följande:

Paper II: Effects of ice cover on the diel behaviour and ventilation rate of juvenile brown trout

Paper III: Day and night drift-feeding by juvenile salmonids at low water temperatures

Paper IV: Prey capture rates of two species of salmonids (Salmo trutta and Thymallus thymallus) in an artificial stream: effects of temperature on their functional response

Paper V: Ice cover alters the behavior and stress level of brown trout Salmo trutta

Avhandlingens försvar kommer att gå av stapeln den 22 Januari 2016 kl. 10:15 i Nyquistsalen (9C 203) på Karlstads Universitet. Opponent är Richard Cunjak från University of New Brunswick, Kanada. Alla intresserade är välkomna.

Salmonid (Atlantic salmon) eggs (photoscienceimage)

Larry Greenberg is currently working on a research project on potential effects of increased winter temperature on brown trout growth and behavior. The research is funded by Karlstad University’s Lecturers and Professors Research Award. Larry describes the project:

“The predicted climate change over the next 65 years will have a major impact on the Earth’s plants and animals. Climate scenarios for Sweden predict that mean annual temperature will increase by 3-5 ° C, with a greater increase in winter than in summer. Because incubation of eggs laid by brown trout and related fishes occurs during winter, the predicted increased winter temperatures may have a major impact on egg development, with far-reaching consequences for fish after they have hatched. The fact that environmental conditions during the egg stage can affect later life stages (juveniles and adults) may seem unlikely, but recent studies have already shown that temperature conditions during egg development can affect growth of juveniles and even reproductive output of adults. As embryonic temperature conditions have been shown to affect growth, one would also expect such conditions to even affect behavior, as behavior and growth are often linked.

For this project, I plan to investigate how an increase in winter temperature conditions during egg development affects the behavior and growth of juvenile brown trout. I will raise fertilized brown trout eggs over the winter at ambient temperature and at 5° C warmer water, and test for subsequent effects on the feeding behavior and personality of juveniles as well as on their growth and metabolic rates.  The research is novel by being the first to investigate whether or not thermal conditions during egg development can affect both the behavior and growth of juveniles.”

The eggs are presently developing under different temperature regimes at Gammelkroppa fish hatchery.

Last Friday, Joacim Näslund, Gothenburg University defended his thesis: “The Pace of Life of Juvenile Brown Trout – Inter- and Intra-individual Variation in Growth and Behaviour“. Opponent was Robert McLaughlin from University of Guelph, Canada. John Piccolo, from Karlstads Universiy was part of the “betygsnämnd” (evaluation committee) together with Petronella Kettunen, GU och Fredrik Nordwall, HaV. 

In relation to the defense, a workshop on “Ecology of Stream Salmonids” was organized. At the workshop, John Piccolo presented an overview of foraging and habitat selection models for salmonid restoration.

A few weeks ago Stina Gustavsson and I (both PhD-students at KaU) attended a course in “Fish migration: Theory and technology” at the Tromsö University (UiT). The course was given by Eva Thorstad (NINA and UiT) and Audun Rikardsen (UiT). Topics included ecology and evolution of fish migration, methods in fish telemetry (tags and tagging) and plenty of case studies on migrating fish. Focus was on anadromous salmonids in northern Europe – Atlantic salmon, brown trout and arctic charr – and European eel, but (for example) fish migration studies in the Zambezi River and on Atlantic halibut were also discussed. Elina Halttunen, IMR also visited the course and gave a lecture on the importance of Atlantic salmon post-spawners and their downstream migration. Other attendees included Master- and PhD-students from Tromsö University (Norway), Oslo University (Norway) and DTU Aqua (Denmark). It was an interesting course with good lectures and a lot of stimulating discussions.

“Arctic charr in midnight sun”
Photo: Audun Richardsen – www.audunrikardsen.com

Åsa Enefalk speglar sig i pinnarna i Karlstads Universitets strömrännor.

Idag höll Åsa Enefalk ett intressant och uppskattat seminarium med titeln ”Effects of fine woody debris on brown trout”. Hon började sitt föredrag med en genomgång om den ekologiska teorin bakom öring och död ved. Död ved, eller ”fine woody debris” (pinnar!) som Åsa forskar om, kan påverka öringen och dess tillväxt på flera olika sätt. Pinnarna kan ge skydd från strömmen, vilket minskar energiåtgången och därigenom kan öka tillväxten. Veden kan också ge avskärma en öring från andra öringar och på så sätt minska mängden konflikter mellan fiskarna. Genom att inte slösa lika mycket tid och energi på att slåss kan fisken ägna sig åt att tillväxa. Den döda veden utgör också habitat för öringens mat – bottenfauna – och ger fisken skydd från predatorer. Men för mycket ved är inte heller bra. En massa ved kan bli ett problem vid jakten på maten och om fiskarna istället för att ha lite koll på varandra irrar runt i en vedlabyrint, för att plötsligt stöta på varandra kan det leda till mer aggression.

Åsa berättade sedan om hennes forskning runt dessa här teorier. Hon beskrev både ett laboratorieförsök i källaren på Kau och ett experiment i utomhusrännor i Finland. Hon har sett att öringen gärna uppehåller sig i veden och bekräftat att veden påverkar fiskens beteende. Tidiga resultat pekar på att sambandet mellan ved och tillväxt inte alltid är glasklart. En intressant aspekt av resultaten var hur fiskarnas inbördes rang påverkar hur de drar nytta av och beter sig i veden. Till exempel var aggressiviteten hög för fiskar med hög rang, både i miljöer med väldigt lite och väldigt mycket ved men mindre med mellanstora tätheter av ved. För fiskar med låg rang utgjorde dock även mycket ved ett skydd från aggressivitet.

Linnea disputerar den 24 februari kl 10.15 i sal 9C 204 (obs inte kl 13.15). Spikningen blir den 3 februari kl 13. Hennes avhandling heter “Behaviour and metabolic rates of brown trout and Atlantic salmon: influence of food, environment and social interactions”.

Larry Greenberg, Professor