River Rottnan in winter

Johan Watz, Olle Calles, Niclas Carlsson, Teemu Collin, Ari Huusko, Jörgen Johnsson, Anders Nilsson, Johnny Norrgård and Daniel Nyqvist recently published the paper “Wood addition in the hatchery and river environments affects post-release performance of overwintering brown trout” in the journal Freshwater Biology.

In the abstract, the authors write:

“1. Habitat structural complexity affects the behaviour and physiology of individuals, and responses to the  environment can be immediate or influence performance later in life through delayed effects.

2. Here, we investigated how structural enrichment, both pre-release in the hatchery rearing environment and post-release in the wild, influenced winter growth and site fidelity of brown trout stocked into side channels of a regulated river.

3. Experiencing structural enrichment in the rearing environment during 3 months in autumn had no pre-release effect on growth, but a delayed positive effect after release during the subsequent winter. Moreover, trout recaptured in wood-treated sections of the side channels had grown more than trout recaptured in control sections. Wood enrichment in the side channels also increased overwinter site fidelity.

Johan Watz at the field site.

4. These results show that adding structure during a relatively short period may alter growth trajectories, and adding wood to side channels is a cost-effective method to enhance winter habitat carrying capacity for  juvenile salmonids in regulated rivers.”

Access the paper here.

Teemu Collin tracking trout at the field site.

 

Dead wood in a side channel of the river.

 

River Rottnan.

A Dolly Varden trout (Salvelinus malma).

On Tuesday 16 October, Johan Watz from Karlstad University will give a seminar titled: “Report from a postdoctoral research stay in Sapporo and results from a field experiment: Condition-specific competition between two Japanese charr species”. The seminar will start at 13:15 in room 5F416 at Karlstad University. Everyone who wants to are welcome to attend the seminar.

Forskare i NRRV har under hösten påbörjat ett projekt inom ett för forskargruppen helt nytt ämnesområde. Det handlar om rörelsemönster hos den spanska skogssnigeln, även kallad mördarsnigel. Mördarsnigeln är en ovälkommen gäst i mångas trädgårdar, där den kan orsaka stor skada genom att äta rent i odlingar och blomsterrabatter. Det är en främmande art i Sverige, som mest troligt har kommit hit när ägg följt med plantor, jord, krukor och annan trädgårdsutrustning.

Frågor om sniglarnas spridningsmönster och koloniseringsförmåga när de väl har kommit till ett område skulle kunna besvaras med hjälp av studien. Till en början diskuterades sniglarna under en fikarast på universitetet, sedan följde att Johan Watz (projektledare) med flera på Karlstads universitet sökte och fick pengar av Kungliga Skogs- och Lantbruksakademien för att genomföra studien.

Nu har ca 50 mördarsniglar i en trädgård i Karlstad märkts med små chip (så kallade pit-tags, samma typ av märkning som används i forskningen om fisk), så att sniglarna kan pejlas och deras rörelsemönster och levnadsvanor studeras.

Tidningen Värmlands folkblad (VF) skrev om projektet måndag 1 oktober, som på flera platser i Karlstad tog plats på löpsedlarna.

Även SVT uppmärksammade studien 3 oktober, och reportaget når du genom att trycka här.

Johan Watz, Anders Nilsson and Olle Calles from Karlstads Universitet, and Jonas Elghagen from Elghagen FIskevård, recently published the scientific note “Evaluation of a novel mobile floating trap for collecting migrating juvenile eels, Anguilla anguilla, in rivers” in the journal Fisheries Management and Ecology.

In the abstract, the authors write: “To improve the situation for the threatened European eel in regulated rivers, better methods need to be developed that more efficiently collect and transport juvenile eels past dams. In this study, a novel mobile, floating eel trap is described, and the results from an evaluation of the trap in two Swedish regulated rivers are presented. The mobile trap was designed to reduce the length of the climbing distance while maximizing the width of the entrance. The mobile trap caught more juvenile eels than a stationary eel ladder, serving as control. Furthermore, the mobility of the floating trap enables adaptive placement and thus offers managers the possibility to search for the spatial optimum for trapping efficiency.” Access the paper here, or e-mail any of the authors

The mobile floating trap next to the stationary eel ladder used as control. Photo from the Watz et al. 2017.

The mobile floating trap without cover. Juvenile eels climb the short and wide ramps (black) and slide (on the small metallic shutes) towards the left (in the photo) were they are collected. Photo: from the papers supplementary material.

The trap in the tailrace of a hydropower plant in River Lagan.

A sample of juvenile eels caught in the study, here held in a 10 L bucket.

The book, “Brown Trout: Biology, Ecology and Management”, edit by Javier Lobón-Cerviá and Nuria Sanz was recently published. The book is described as “a comprehensive guide to the most current research, history, genetics and ecology of the brown trout including challenging environmental problems”. John Piccolo and Johan Watz, both researchers at Karlstad University, have written the chapter Foraging Behaviour of Brown Trout: A Model Species For Linking Individual Ecology to Population Dynamics? They summarize their chapter as follows:

“Within the discipline of stream fish ecology, population-, community-, and even ecosystem-level patterns and processes have assumed an increasingly larger role in recent decades. It might be argued, however, that research on the behaviour of individual organisms ought still to play a major role in ecology; it is upon the individual, after all, that natural selection acts. Thus, one might reasonably expect that observing an individual fish’s behaviour should lead to robust conclusions about the fitness costs and benefits that animals must trade-off in order to achieve reproductive success. And ultimately, it is those individuals that achieve the greatest direct fitness that ought to, on average, drive the population-level processes that have attracted so much of stream fish ecologists’ attention in recent years. In linking behavioral- to population-level ecology, we are in luck when it comes to the brown trout – there is no stream fish species whose population ecology is better quantified, nor are there many species that have received more attention from behavioural ecologists. Thus we might consider the brown trout as a model species for developing the ecological understanding of how natural selection (e.g. individual, fitness-based decisions) acts to regulate stream fish populations. To forward this concept, a further development of a quantitative approach to foraging behaviour is warranted. In this chapter we review and synthesize the literature on brown trout foraging experiments with an eye towards identifying the knowledge gaps that remain to be filled in order for ecologists to quantify the fitness costs and benefits of foraging behaviour.”

The book is available (but expensive) here. For access to the specific book chapter, email John Piccolo or Johan Watz.

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A juvenile brown trout in the experimental flume.

Johan Watz, postdoc at Karlstad University, recently published the scientific article “Stress responses of juvenile brown trout under winter conditions in a laboratory stream” in the journal Hydrobiologia. In the abstract he writes: “Winter can be a challenging period for fish in northern temperate rivers and streams, particularly in those that are channelized, structurally simple or regulated by, for instance, hydropower. In these systems, dynamic sub-surface ice formation commonly occurs and stable periods with ice cover may be short. Under these adverse conditions, access to shelters has been shown to be an important factor that influences overwinter survival, and exclusion from shelters by anchor ice may cause stress. Here, stress responses of juvenile brown trout under simulated winter conditions in an artificial stream were studied. Trout were subjected to three treatments in which the trout (1) were excluded from an instream wood shelter, simulating the effects of anchor ice, (2) had access to the shelter or (3) had surface ice cover in addition to the shelter. There was a positive correlation between ventilation frequency and plasma cortisol concentration. Trout without access to shelter had 30% higher ventilation frequency than trout with instream shelter and surface ice, but no differences in cortisol concentration or stress colour were found between the treatments. River regulation that reduces surface ice and increases anchor ice formation may lead to increased stress and consequently reduce overwinter survival rates.”. 

Access the paper here: Stress responses of juvenile brown trout under winter conditions in a laboratory stream.

Johan Watz, postdoc vid Karlstads Universitet, forskar om öringens vinterekologi. Just nu pågår fältarbete i Rottnan, Värmland. Johan berättar: “Vinterförhållanden i rinnande vatten kan påverka hur mycket fisk som kan leva i älven och hur många smolt som produceras. I ett projekt tillsammans med Fortum och Bergvik Skog undersöker vi hur öringungar klarar vintern i sidofåror till Rottnan. Platser som har berikats med struktur, i form av träd som fällts i vattnet, jämförs med platser utan trädberikning. Ettåriga PIT-märkta öringar spåras genom isen, och med stationära loggerstationer. Öringarnas förflyttningar, överlevnad och tillväxt studeras. Projektet kommer fortgå fram till islossningen.”

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Johan Watz, mitt i Rottnan. “Fältarbete i -20C kan vara så här roligt.”

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Lisse de Groot, Erasmuspraktikant från Nederländerna, vid en damm av bottenis.

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En loggerstation (vid den svarta plastpåsen) detekterar fiskar som simmar förbi.

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Teemu Collin och Niclas Carlsson (studenter vid Karlstads Universitet) pejlar öring.

Verkar detta intressant? Just nu söker Karlstads Universitet en doktorand i just fiskars vinterekologi: PhD position in Global climate change and winter ecology

Imorgon, onsdagen den 7:e december, kommer Johan Watz, forskare vid Karlstads Universitet, att berätta om öringens vinterbeteende i rinnande vatten. Evenemanget är en del av universitetets “Möt en forskare”-serie och ges kl. 12:00 – 12:45 i Studieverkstaden på plan 3 i universitetets bibliotek. Alla är välkomna!

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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.

Intresserade barn samlas kring ålakvariet medan Martin Österling och Olle Calles berättar. Foto från Värmlands Folkblad.

Igår presenterades ål och ålforskning för barn i aulan på Karlstads Universitet. Som en del av Barnens universitet berättade Olle Calles och Martin Österling om ålens vandring från Sargassohavet till våra kuster,vattendrag och sjöar, och tillbaka igen. Den kraftiga minskningen av ålbestånden under de senaste årtiondena illustrerades och en ålyngelledare för att leda ålyngel förbi vattenkraftverk byggdes på scen. Tillslut förevisades levande ålar och radiotelemetri-utrustning för intresserade barn. Även Johan Watz, postdoc vid Karlstads Universitet, och Lissie de Groot, Erasmus-praktikant vid universitetet, deltog i arrangemanget.

Lokalpressen var på plats och rapporterade senare om ålen på Barnens universitet:

Värmlands Folkblad: Lärde skolbarn rädda ålar

Nya Wärmlands Tidning: Barnens universitet är tillbaka