The study focused on the behavior of kelts at the Edsforsen dam – the first dam that the downstream migrating kelts encounter.

The scientific paper ”Intake Approach and Dam Passage by Downstream-migrating Atlantic Salmon Kelts” by Daniel Nyqvist, Eva Bergman, Olle Calles, and Larry Greenberg was recently published in River Research and Applications. The paper presents a study on the behavior of downstream migrating kelts in the River Klarälven, Sweden. In the abstract the authors write:

”Studying fish behaviour at hydropower dams is needed to facilitate the design and improvement of fish passage solutions, but few studies have focused on Atlantic salmon kelts. Here, we used radio telemetry (n = 40, size range = 50–81 cm) and acoustic sonar to study kelt movements in the forebay as well as their dam passage survival and subsequent migration success past multiple dams. We also compare radio telemetry and acoustic sonar observations of fish behaviour and used acoustic sonar to measure the depth distribution of fish approaching the turbine intake zone. Passage success at the dam was 41%, and mortality was largely associated with turbine passage (62%). The two fish that passed via the spill gates survived and continued their downstream migration. At the dam, all but one radio-tagged kelt approached the intake zone shortly after arrival to the forebay, and sonar data showed that approaching fish were predominantly surface oriented (72%, 88% and 96% of the observations were less than 1, 2 and 3 m deep, respectively). Turbine passage rate from the intake zone was higher at night than at day, indicating that the lack of visual cues may reduce the barrier effect of the 70-mm conventional trash rack. Turbine passage rate also increased with increasing hydropower generation. The percentage of observed upstream movements away from the intake zone compared with the total number of observations was considerably greater in the radio telemetry data (41%) than in the sonar data (4%). Only one fish survived passage of all eight hydropower dams to reach the lake. This low-passage survival underscores the need for remedial measures to increase the survival of migrating kelts, and the fish’s surface orientation as well as their rapid approach to the intake rack should be taken into account when designing such measures.”

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

John Piccolo, researcher at Karlstad University has written a short story for the Freshwater Working Group of the Society of Conservation Biology about his work in Klarälven. Read the story at the group’s facebook page or here below:

This is a story about some of the toughest field work I’ve carried out in over 20 years of research on salmon populations in either North America or Sweden, and describes the first documentation of a wild Atlantic salmon smolt run on the River Klarälven in central Sweden.

Klarälven is the longest river in Scandinavia, and is home to one of the world’s last remaining large-bodied landlocked Atlantic salmon (pictured) populations. The landlocked salmon migrate from Vänern, the largest lake in the EU, to spawn and rear in Klarälven (learn more about Klarälven here). After living for 2-4 years in the river, the salmon smolt migrate downstream to feed and grow in the lake. Although there has been anecdotal information about the smolt migration for many years, nobody had ever succeeded in trapping them to estimate production. Due to historical fishing pressure, and hydropower development, the Klarälven salmon are believed to be highly-threatened. However, salmon populations could also be recovering in Klarälven, because fishing pressures have reduced, and populations have gone from a low of less than 100 spawning adults to a record return of over 1000 in 2016. With this history in mind, we set out to better our understanding of salmon smolt populations in Klarälven and to guide more successful management and restoration.


A River Klarälven smolt (photo: Teemu Collin).

As many aquatic scientists know, trapping fishes or even invertebrates in rivers can be difficult – they all tend to migrate during rising or falling flows when water levels in the river are high. Keeping a net in the water can be difficult or impossible under such conditions. Months of organic debris that has been deposited along the river banks is suddenly washed into the stream, and nets need to be cleaned often, sometimes hourly 24-hours round. An additional variable in the mix is that in large rivers, organic debris can be large (picture large tree branches or even entire trees!)! High water levels, rapid flows, and large debris are challenging obstacles, and if these obstacles bring our sampling gear down, it can be quite dangerous to get the gear up and running again. I did my first smolt trapping back in 1996 on the Salmon River in Idaho, USA. I remember watching a mature conifer tree some 30 meters long being sucked into an eddy like a drinking straw, and being ejected clear out of the river on its’ way downstream. The power of a flooding river is truly awe-inspiring.


The crew working on the trap (photo: Teemu Collin).

It took us four sampling seasons, filled with trial and error, to achieve partial sampling success for our project. The first year we tried floating smolt traps like those often used for Pacific salmon. Although these can be adequate when there are large numbers of smolt migrating, we did not catch sufficient numbers of smolt to make mark-recapture estimates. During years two and three, we imported stationary traps, a Finnish design, that are anchored to the river bottom with 3-4-meter-long thick iron poles. It takes two days of hard labor for a work crew to drive these into the substrate by hand, balancing on the deck while holding the boat in position in the strong river flow (see photos). Inspired by the work to setup these Finnish traps, the title for this story comes from the classic song about mine workers – the iron bars didn’t weigh 16 tons, but just setting up the net was A LOT of work. Once the net was installed, the hard work began. Cleaning and emptying the net every day, and waiting for the spring flood to bring the salmon smolt. Although I was involved in this work, it is really our field crew that deserves most of the credit – it was a 24-hour a day, 7-day a week job, cleaning every day and staying vigilant for possible emergencies. During years two and three we came close to success – we had begun to catch larger numbers of smolt just at the time when flows became unmanageable and the net had to be removed. These years involved a lot of trial and error in operating and maintaining the net, cleaning, sewing mesh, clearing debris. The worst of it was cutting the net out during high flows, just when it seemed the smolt were beginning to run.


The Finnish trap (photo: Teemu Collin).

Each year we’d improved our technique and catch; the second year we caught over 300 smolt, and made our first rough estimates of production. However, we had yet to document a substantial wild smolt run. We managed to scrape together enough funding for one more try, and set to work for our final attempt. With two years’ experience, we installed the net in record time and had a good cleaning and maintenance routine. The field crew was on the job every day and smolt numbers began to climb as did the prognosis for the spring flood. They managed to continue to fish the net right into the beginning of the flood, and finally, on the last five days that they could fish before the flood, they hit the jackpot! SMOLTS! The field crew caught over 1000 smolt during their last five days – 425 the day before they had to remove the net. This one-week catch exceeded the total number of smolt we’d caught the previous two years combined. Our mark-recapture estimates suggest that over 15,000 wild salmon smolt migrated that year, documenting substantial production of wild landlocked Atlantic salmon, probably the largest remaining population in the world. Our hard work and persistence paid off – national and international awareness of the Klarälven salmon has continued to grow, and they are the focus of renewed efforts to maintain and restore wild salmon populations that have been impacted by centuries of anthropogenic impacts.”

nyqvist2016cLast Friday, I, Daniel Nyqvist, successfully defended my PhD-thesis ”Atlantic salmon in regulated rivers – Migration, dam passage, and fish behavior” at Karlstad University. Scott Hinch (University of British Columbia, Canada) was opponent and Eva Thorstad (NINA, Norway), Kim Aarestrup (DTU AQUA, Denmark) and Hans Lundqvist (Swedish University of Agriculture) constituted the grading committee (betygskommitté). The short abstract of the thesis reads:

”Hydropower dams block migration routes, thereby posing a threat to migratory fish species. Fishways and other fish passage solutions may aid fish to pass hydropower dams. A functional fish passage solution, however, must ensure safe and timely passage for a substantial portion of the migrating fish. In this thesis, I focus on downstream passage and evaluate the behavior and survival of migrating Atlantic salmon in relation to dams in systems with (1) no fish passage solutions (2) simple passage solutions (3) best available passage solutions. In addition, I studied the survival and behavior of post-spawners and hatchery-released smolts.

A large portion of the spawners survived spawning and initiated downstream migration. For hatchery-reared smolts, early release was associated with faster initiation of migration and higher survival compared to late release. Multiple dam passage resulted in high mortality, and high spill levels were linked to high survival and short delay for downstream migrating salmon. For smolts, dam passage, even with simple passage solutions, was associated with substantial delay and mortality. Rapid passage of a large portion of the migrating adult salmon was achieved using best available passage solutions.”

The frame of the thesis is available here. Already published papers included in the thesis are Post-Spawning Survival and Downstream Passage of Landlocked Atlantic Salmon (Salmo salar) in a Regulated River: Is There Potential for Repeat Spawning? (in River Research and Applications) and Migratory delay leads to reduced passage success of Atlantic salmon smolts at a hydroelectric dam (in Ecology of Freshwater Fish). For full access to the thesis, contact


Radiotagged migrating brown trout.

Next week, Daniel Nyqvist, PhD-student at Karlstad University, will defend his (my…) thesis ”Atlantic salmon in regulated rivers: migration, dam passage, and fish behavior”. The defense will take place on Friday, December 9th, at 10:15 in room 9C 203 on Karlstad University. The abstract and the frame of the thesis are available online here.

Scott Hinch (University of British Columbia, Canada) is the opponent and Eva Thorstad (NINA, Norway), Kim Aarestrup (DTU AQUA, Denmark) and Hans Lundqvist (Swedish University of Agriculture) constitute the grading committee (betygskommitté). The visiting researchers will give seminars at Karlstad University on Thursday, December 8th. The seminars start at 14:15 in room 5F322:

Scott Hinch: Using telemetry in adaptive management experiments at fish passage facilities

Eva Thorstad: New results on downstream migration of eel and salmon past power stations in Germany

Hans Lundqvist: Wild Baltic stocks of Atlantic salmon in northern Sweden: Where are we and where are we going in Umeälven?

Kim Aarestrup has yet to disclose the title of his seminar.

Everyone is welcome to attend both the PhD-defense and the seminars.

I Klarälven fångas lekvandrande lax och öring i en fiskfälla i Forshaga, det första kraftverket de stöter på under sin vandring upp i älven. Fällan består av en laxtrappa som slutar i ett falskt fall som lockar fisken in i fisken i en bassäng. Från fällan i Forshaga transporteras de fångade fiskarna i lastbil förbi åtta vattenkraftverk och släpps ut i norra Värmland. Därifrån fortsätter de sin lekvandring älven. Fisken rör sig fritt i området mellan Edsforsens- och Höljes kraftverk. Under de senaste åren har arbete bedrivits för att förbättra verksamheten vid fällan, och det har troligtvis bidragit till det rekordhöga antalet fångad och transporterad vild lax och öring under 2016. Enligt den statistik som finns tillgänglig har det aldrig fångats lika många vilda laxar respektive öringar något enskilt år sedan åtminstone slutet av 1940-talet. Ännu återstår ett par veckor innan fällan stänger för säsongen.


Antalet vilda laxar fångade i fällan i Forshaga (bild från Gammelkroppa lax AB).


Antalet vilda öringar fångade i fällan i Forshaga (bild från Gammelkroppa lax AB).


The scientific paper ”The Migratory Behaviour and Fallback Rate of Landlocked Atlantic Salmon (Salmo salar) in a Regulated River: does Timing Matter?” by Anna Hagelin, Olle Calles, Larry Greenberg, Daniel Nyqvist and Eva Bergman was recently published in River Research and Applications. The system studied is the River Klarälven, Sweden and in the abstract the authors write:

”The behavior of early (June–July) and late (August–September) migrating, adult Atlantic salmon, in The River Klarälven, Sweden, was analyzed using radio telemetry. River Klarälven is a regulated river without functioning fishways, instead upstream migrating salmon are trapped and trucked past eight hydropower plants before released back to the river. We distinguished two parts of the spawning migration, that is, one part being the migration from the place where the fish was released to the spawning grounds. The other part was a holding phase on the spawning grounds with little or no movements before spawning. The late salmon spent less of their total time on holding, 36.2%, and more on migration, 63.8%, compared with early migrating salmon, which distributed their time rather evenly between migration, 47.5%, and holding, 52.5%. In total, early salmon used 30% more time migrating and 156% more time holding than late salmon. Some Atlantic salmon (Salmo salar) fell back over the hydropower plant after release and got excluded from spawning. The fallback rates of transported, tagged spawners were higher in the early than in the late group in both years. The fallback rate in 2012 was 42.8% of the early group and 15.1% in the late. In 2013, there were 51.7 % fallbacks in the early group and 3.4% in the late. The salmon fell back on average 9 days after being released in 2012 and 16 days in 2013. A high mean daily discharge on the day of release increased the probability of becoming a fallback”

Download the paper here. If you don’t have free access, email any of the co-authors.

Igår höll Larry Greenberg, professor vid Karlstads Universitet, en presentation om våra forskningsprojekt i Klarälven på ett möte arrangerat av Klarälvens Vattenråd i samverkan med Fortum och Karlstads Universitet. Fokus i presentation låg på förbättrad nedströmspassage för vild laxfisk i Klarälven. Larry rapporterar om ett välbesökt och engagerat möte: ”Cirka 25 personer var med och lyssnade och det fanns gott om frågor efteråt. Många åhörare ville se åtgärder så snart som möjligt även om man förstår att det tar tid…”


Edsforsens kraftverk med turbin-intaget i förgrunden och spill-luckor längre bak i bild. På fotot syns också antenner vi använde för att studera beteende avradiomärkta kelt i relation till dammen och kraftverket.

Läs mer om laxen i Klarälven i rapporten ”Vänerlaxens fria gång”.


Kelt framför intagsgaller (foto: Herman Wanningen).

Den vetenskapliga artikeln ”Post-spawning survival and downstream passage of landlocked Atlantic salmon (salmo salar) in a regulated river: is there potential for repeat spawning?”, om efterleksöverlevnad, nedströmsmigration och passage hos lax-kelt i Klarälven, har publicerats i River Research and Applications. Författare är Daniel Nyqvist, Olle Calles, Eva BergmanAnna Hagelin och Larry Greenberg.

I abstraktet skriver författarna: ”Repeat salmonid spawners may make large contributions to total recruitment and long term population stability. Despite their potential importance, relatively little is known about this phase of the life history for anadromous populations, and nothing has been reported for landlocked populations. Here, we studied post-spawning behaviour and survival of landlocked Atlantic salmon in relation to downstream dam passage in the River Klarälven, Sweden. Eight hydropower stations separate the feeding grounds in Lake Vänern from the spawning grounds in the River Klarälven, and no measures to facilitate downstream migration are present in the river. Forty-nine percent of the salmon survived spawning and initiated downstream migration. Females and small fish had higher post-spawning survival than males and large fish. The postspawners migrated downstream in autumn and spring and remained relatively inactive in the river during winter. Downstream migration speed in the free flowing part of the river was highly variable with a median of 9.30 km/day. Most fish passed the first hydropower station via upward-opening spill gates after a median residence time in the forebay of 25 min. However, no tagged fish survived passage of all eight hydropower stations to reach Lake Vänern. This result underscores the need for remedial measures to increase the survival of downstream migrating kelts.”

Läs artikeln här. Om du inte har tillgång till tidskriftens innehåll men ändå vill läsa artikeln, maila någon av författarna!


Lekvandrande laxar, liksom öringar, har radiomärkts och deras lekvandring studerats i Klarälven. Här märker Anna Hagelin en lax med radiosändare.

Igår höll Anna Hagelin, doktorand vid Karlstads Universitet, ett seminarium med titeln ”Fallback frequency in Landlocked Atlantic salmon and Brown trout – Does timing matter?”. Hon berättade om preliminära resultat av en telemetri-studie på lax och öring i Klarälven.

När lekvandrar laxen och varför just då? De allra flesta Atlantlaxar leker på hösten men variationen i när de vandrar upp i älven är stor. En del populationer (eller delar av populationer) vandrar på hösten innan lek, andra redan på våren och i en del extremfall – som till exempel i Loire, Frankrike – vandrar lax upp redan hösten/vintern året innan lek. Eftersom laxen inte äter i älven innebär en tidig uppvandring en potentiell kostnad i form av utebliven tillväxt. Frågan är då varför många laxar ändå vandrar upp tidigare än de ”skulle behöva”. Flera teorier har försökt förklara de tidiga vandrarna. En vanlig förklaring är att de tidiga vandrarna vandrar högre upp i systemen och därför behöver mer tid för att vandra. En annan förklaring är att de behöver ta sig upp i vattendrag som bara är passerbara under vissa delar av året (detta är exempelvis en trolig förklaring för extremfallet Loire). Genom att vandra in i en kall älv, utan predatorer och vila sig fram till lek skulle fisken också kunna byta reducerad tillväxtmöjlighet mot högre överlevnad. Tidiga fiskar kan också tänkas få en en konkurrensfördel på lekplatsen gentemot sina senkomna, och mindre hemtama, populationsfränder. Olika förklaringar kan tänkas vara sanna i olika grad för olika populationer.

I Klarälven, där laxen vandrar upp åtminstone från maj till oktober, vet vi inte vad som driver variationen. Vad Anna Hagelins preliminära resultat visar är dock att fiskar som vandrar upp i Klarälven tidigt i högre utsträckning blir fallbacks. I utbyggda vattendrag där den uppströmsvandrande fisken passerar vattenkraftverksdammar, antingen via fiskvägar eller genom att lyftas/transporteras, finns risken att de ska falla tillbaka nedströms kraftverket igen – via spill, turbiner eller fiskvägar. Fiskar som faller tillbaka kallas fallbacks. Att falla tillbaka kan ha kraftig påverkan på den individuella fisken –  det ökar tids- och energiåtgången för passage – och på populationen som helhet. På platser där fisken räknas vid passage kan förekomsten av fallbacks leda till dubbelräkning och felaktiga beståndsuppskattningar. I Klarälven där den uppströmsvandrande laxen fångas i Forshaga, transporteras uppströms, förbi åtta kraftverk utan fiskvägar, och släpps ut i älven för att fortsätta sin lekvandring är att falla tillbaka likställt med att bli utestängd från lekplatserna. Detta innebär naturligtvis att fallbacks är en viktig aspekt av förvaltningen av laxbeståndet i älven. Men varför faller tidiga fiskar tillbaka i högre utsträckning än sena? Och vad skulle man kunna göra åt det? Det är några av frågorna Anna jobbar med just nu. Vi ser fram emot resultaten av detta arbete!

Den vetenskapliga artikeln ”Spawning migration of wild and supplementary stocked landlocked Atlantic salmon (Salmo salar)”, om laxens lekvandring i Klarälven, har publicerats i River Research and Applications. Författare är Anna Hagelin, Olle Calles, John Piccolo, Larry Greenberg och Eva Bergman från NRRV, Karlstads Universitet. I artikelns abstrakt skriver de:

”Upstream migration by adult salmonids is impeded by dams in many regulated rivers, as is the case for landlocked Atlantic salmon, Salmo salar, in the River Klarälven, Sweden. There, the salmon cannot reach the spawning grounds due to the presence of eight dams. Hence, hatchery-reared smolts are released downstream of the dams, and upstream migrating spawners are caught in a trap at the lowermost dam before transported by truck to the spawning grounds past the dams. To identify the spawning grounds and compare the behavior of wild and hatchery-reared Atlantic salmon during upstream migration and spawning, 34 wild and 28 hatchery-reared, radio-tagged Atlantic salmon were followed during their spawning migration from August to October 2011. Half (50%) of the hatchery fish, but only 11,8% of the wild fish ended up as fallbacks, i.e. they migrated past the first downstream power station, and did not spawn. A significantly higher proportion (21.4%) of hatchery- reared salmon moved in an erratic way, with several up and down stream movements, when compared to the wild salmon (5.9%). When looking at the salmon that stayed in the river (exc. fallbacks), wild individuals exhibited a holding behavior (little or no movements before presumed spawning) more often (86.7%) than the reared ones (50%). The wild salmon also held position (and presumably spawned) for longer time (25.4 days) than the reared salmon (16.1 days). Reared salmon held position, on average, 10 km further upstream than wild salmon, passing the presumed best-quality spawning habitat. The migration speed (average 17.4 km/day) between two logger stations did not differ between wild and reared fish or between sexes. Our results suggest that the reproductive success of hatchery-reared Atlantic salmon is relatively low and their capacity as supplementary spawners to the wild population in the Klarälven, is probably small.”

Läs artikeln här. Om du inte har tillgång till tidskriftens innehåll men ändå vill läsa artikeln, maila författarna!