Rachel Bowes (RivEM PostDoc) and colleagues have studied the downstream passage of several migrating fish species during spring and fall 2020. Here she writes about their work:

Laxeleratorn at Vattenfall’s Research & Development facility in Älvkarleby

“Dams are like giant road blocks for fish in rivers. It is not always feasible or realistic to remove a dam to restore fish movement throughout rivers, so we need to design detours around them.

When going downstream we call this detour past the dam a bypass. The question we are asking is: How can we design a better bypass for multiple fish species to be able to move downstream past a dam more easily and efficiently? To test this, we are using the Laxeleratorn at Vattenfall’s Research & Development facility in Älvkarleby. We are testing Silver Eels, Salmon, and Roach fish species. Changing the design of the bypass and amount of water flowing through it, we hope to find out what combination creates the optimal bypass for these fish species.”

European eel (Anguilla anguilla)

European eel, Anguilla anguilla. Photo: Jörgen Wiklund

Karlstad University has an opening for a PhD position in aquatic conservation biology. The project will focus on “Resolving production bottlenecks for the European eel”. Conserving biodiversity is one of the major challenges in applied aquatic ecology. The European eel functions as a flagship species in marine and freshwater conservation, and its population collapse is of major concern for ecologists, fishers and managers.

The aim of the PhD project is to identify:

(i) relationships between yellow eel habitat use, growth, behavior and survival.

(ii) effects of habitat characteristics and the surrounding landscape on eel large-scale movements within freshwater systems.

(iii) functioning downstream passage solutions at hydropower plants for a wide range of silver eel phenotypes.

The position is full-time for four years. Doctoral students may also be assigned departmental duties, such as teaching, which will extend the period of employment accordingly.

Read more and apply for the position here.

Last day to apply is 5 June 2019.

Europeisk ål, Anguilla anguilla. Foto: Jörgen Wiklund.

Under senhösten 2018 har forskare från NRRV undersökt två olika typer av låglutande galler (vinkel mot strömriktningen = 30°) och dess effekt på nedströmsvandrande ål (Anguilla anguilla). Studien har utförts i Vattenfalls nya strömränna ”Laxelleratorn” som genom sina mått (24 meter lång, 4 meter bred och 2 meter djup) är i paritet med en intagskanal till ett litet vattenkraftverk.

Bakgrunden tll studien är den stora minskningen av ålbeståndet som har skett sedan mitten av 1900-talet och som lett till att ålen numer är klassad som en akut hotad art (sedan 2005). En av orsakerna tros vara den höga mortaliteten för blankål vid nedströmspassage i anslutning till vattenkraftverk, där framförallt passage genom turbinerna ger låga överlevnadschanser.


Laxelleratorn i Älvkarleby.

För att hindra ålen att passera genom turbinerna eller andra passager med hög mortalitet kan, istället för ett konventionellt intagsgaller, ett låglutande galler (< 30° mot strömriktning) installeras. Dessa leder fisken mot en flyktöppning som leder till en säkrare passage, till exempel en fiskväg eller en fälla, och en återställning av vattendragets konnektivitet. Ett exempel där ett låglutande galler finns installerat är Hertingforsen i Ätran där goda resultat uppnåtts för flera arter (Calles m.fl.).

Totalt märktes 80 ålar (medellängd ± 1 standardavvikelse (SD) = 845 ± 74 mm) med PIT-tags och släpptes ut i strömrännan där de endera fick möta ett α-galler (avleder fisk från botten mot ytan) eller ett β-galler (avleder fisken från ena sidan till den andra). Dessutom testades för vardera galler två olika spaltvidder: 15 och 30 millimeter. De huvudsakliga parametrarna som undersöktes var avledningseffektivitet för respektive gallerkonfiguration och tiden den tog för ålen att passera.

Resultatet analyseras i nuläget men de preliminära resultaten tyder generellt på en god avledande förmåga. Rapporten planeras vara klar under våren 2019.


Se även:

Calles O, Christiansson J, Kläppe S, Alenäs I, Karlsson S, Nyqvist D, Hebrand M. (2015). Slutrapport Hertingprojektet – Förstudie och uppföljning av åtgärder för förbättrad fiskpassage 2007-2015. Naturresurs rinnande vatten, Karlstads universitet


Försöksuppställningen i laxelleratorn.


The experimental flume “Kungsrännan” under construction in Älvkarleby.

Hydropower dams block migration routes and disrupt longitudinal connectivity in rivers, thereby posing a threat to migratory fish species. Various fish passage solutions have been implemented to improve connectivity with varying success. For downstream migrating fish, low sloping turbine intake racks are used to guide fish to bypasses. Current knowledge, however, is based on hydropower plants with intake capacities <72 cm. There is also a trade-off between electricity generation and fish guidance (smaller bar spacing – better for fish, larger bar spacing – better for hydropower). Currently, gap widths/bar spacings of 10-20 mm are recommended but behavioral guidance effects open up the possibility of larger bar spacings.

During spring, Karlstad University in collaboration with Vattenfall and NINA, will experimentally study the behavior and passage performance of downstream migrating salmon smolts approaching a variety of low sloping intake racks. The experiments will be conducted in a new large experimental flume – Kungsrännan – at the Vattenfall hydraulic laboratory in Älvkarleby, Sweden. We will study the passage behavior and performance of smolts for alpha racks – inclined from the bottom up – and beta racks – angled from one side of the channel to the other – with different gap-widths (15-30 mm).

For this, we are looking for one interested and ambitious assistant to join us in Älvkarleby. The assistant will be salaried and is needed from mid-April to mid-June. Housing in the area can be provided. Are you interested in joining us? Contact Olle Calles for more information.

The principle behind downstream fish passage solutions using low sloping intake racks. The fish is swept and guided along a beta rack to a bypass at the rack’s downstream end.


Tracking smolts in Huntington River, a tributary to Winooski River.

The accepted version of the scientific article “Downstream migration and multiple dam passage by Atlantic salmon smolts” by Daniel Nyqvist (Kau), Stephen McCormick (USGS), Larry Greenberg (Kau), William Ardren (US Fish and Wildlife), Eva Bergman (Kau), Olle Calles (Kau), and Theodore Castro-Santos (USGS) is available online at North American Journal of Fisheries Management. The paper presents a study on downstream migration and dam passage of landlocked Atlantic salmon smolts in the River Winooski, a tributary to Lake Champlain.

In the abstract the authors write: “The purpose of this study was to investigate behavior and survival of radio-tagged wild- and hatchery-reared landlocked Atlantic salmon smolts as they migrated past three hydropower dams equipped with fish bypass solutions in the Winooski River, Vermont, USA. Among hatchery-released smolts, those released early were more likely to initiate migration and did so after less delay than those released late. Once migration was initiated, however, the late-released hatchery smolts migrated at greater speeds. Throughout the river system hatchery released fish performed similarly to wild fish. Dam passage rates varied between the three dams and was highest at the dam where unusually high spill levels occurred throughout the study period. Of the 50 fish that did migrate downstream, only 10% managed to reach the lake. Migration success was low despite the presence of bypass solutions, underscoring the need for evaluations of remedial measures; simply constructing a fishway is not synonymous with providing fish passage.”

Access the paper here or contact the authors.


The Herting dam with the low sloping intake rack in the intake channel to the left and the large nature-like fishway to the right. (Photo from Fiskevårdstekniks film)

Recently, the paper “Upstream and downstream passage of migrating adult Atlantic salmon: Remedial measures improve passage performance at a hydropower dam” was published in the journal Ecological Engineering. The paper was authored by Daniel Nyqvist, Anders Nilsson, Ingemar Alenäs, Jonas Elghagen, Mats Hebrand, Simon Karlsson, Stefan Kläppe and Olle Calles. They summarize the paper: “Habitat connectivity is central for life-cycle progression for migrating organisms. Passage of hydropower dams is associated with mortality, delay, and migratory failure for migrating fish, and the need for remedial measures to facilitate passage is widely recognized. Lately, nature-like fishways have been promoted for upstream migrating fish, and low-sloping turbine intake racks for downstream migrating fish, but evaluations of these remedial measures are largely lacking. At Herting hydropower dam in southern Sweden, a technical fishway for upstream migrating salmonids, and a simple bypass entrance/trash gate for downstream migrating fish have been replaced by a large nature-like fishway for up and downstream migrating fish, and a low-sloping rack, guiding downstream migrating fish to the bypass entrance, has been installed. In this study, we evaluated these remedial measures for adult Atlantic salmon, spawners and kelts, in a before/after improved remedial measures radio telemetry study. Passage performance was improved for both up- and downstream migrating adult Atlantic salmon after remedial measures. Passage rate increased for fish migrating in both directions, and overall delay decreased while overall passage efficiency increased for upstream migrating fish. After the improved passage solutions almost all tagged fish passed the dam with very little delay. Before modifications, upstream passage performance through the technical fishway was higher at higher temperatures, at day compared to night, and for males compared to females. No such effects were observed for the after-measures nature-like fishway, indicating good passage performance for both sexes under a wide range of environmental conditions. Similarly, for downstream migrating kelts, discharge positively affected passage rate before but not after the fishway modifications. Altogether, our work demonstrates the possibility of coexistence between hydropower and Atlantic salmon in a regulated river.”

Access the paper here. For questions, e-mail the authors.

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.

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 daniel.nyqvist@kau.se.


The hydroelectric dam in the study. Turbine intakes and bypass entrances to the left, open spill gates to the right. Photo from Google Maps.

The paper “Migratory delay leads to reduced passage success of Atlantic salmon smolts at a hydroelectric dam” by Daniel Nyqvist (Kau), Larry Greenberg (Kau), Elsa Goerig (INRS, Quebec) , Olle Calles (Kau) , Eva Bergman (Kau), William Ardren (US Fish and Wildlife), and Theodore Castro-Santos (USGS) was recently published in the journal Ecology of Freshwater Fish. The paper presents a study on the behavior of landlocked Atlantic salmon smolts in the Winooski River in Vermont, USA.

In the abstract the authors write:“Passage of hydropower dams is associated with mortality, delay, increased energy expenditure and migratory failure for migrating fish and the need for remedial measures for both upstream and downstream migration is widely recognized. A functional fish passage must ensure safe and timely passage routes that a substantial portion of migrating fish will use. Passage solutions must address not only the number or percentage of fish that successfully pass a barrier, but also the time it takes to pass. Here we used radio telemetry to study the functionality of a fish bypass for downstream-migrating wild-caught and hatchery-released Atlantic salmon smolts. We used time to event analysis to model the influence of fish characteristics and environmental variables on the rates of a series of events associated with dam passage. Among the modeled events were approach rate to the bypass entry zone, retention rates in both the forebay and the entry zone and passage rates. Despite repeated attempts, only 65% of the tagged fish present in the forebay passed the dam. Fish passed via the bypass (33%), via spill (18%) and, via turbines (15%). Discharge was positively related to approach, passage, and retention rates. We did not detect any differences between wild and hatchery fish. Even though individual fish visited the forebay and the entry zone on multiple occasions, most fish passed during the first exposures to these zones. This study underscores the importance of timeliness to passage success and the usefulness of time to event analysis for understanding factors governing passage performance.”

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

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.