MULTIPLICATIVE LOSS OF LANDLOCKED ATLANTIC SALMON <i>Salmo salar</i> L. SMOLTS DURING DOWNSTREAM MIGRATION TROUGH MULTIPLE DAMS

Norrgård, Johnny; Greenberg, Larry; Piccolo, John; Schmitz, Monika; Bergman, Eva

doi:10.1002/rra.2616

Cited by 42 publications

(46 citation statements)

References 54 publications

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“…Only one (6%) of our tagged kelts survived passage of all eight hydropower dams in the system and most probably reached the lake. This confirms the high accumulated mortality of smolts (16%) and kelts (0%) previously reported from the River Klarälven (Norrgård et al ., ; Nyqvist et al ., ) and other systems where fish have to pass multiple dams (Calles & Greenberg, ). The high passage mortality underscores the need for remedial measures to conserve salmon populations in regulated rivers.…”

Section: Discussionmentioning

confidence: 99%

Intake Approach and Dam Passage by Downstream‐migrating Atlantic Salmon Kelts

Nyqvist

Bergman

Calles

et al. 2017

River Research & Apps

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Abstracts 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. Copyright © 2017 John Wiley & Sons, Ltd.

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Section: Discussionmentioning

confidence: 99%

Intake Approach and Dam Passage by Downstream‐migrating Atlantic Salmon Kelts

Nyqvist

Bergman

Calles

et al. 2017

River Research & Apps

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“…There is a risk that dams and power stations delay downstream migrating smolts if they accumulate above the dam or if they are stunned, stressed and disoriented after they have passed the dam and turbines (Norrgård et al., ; Nyqvist et al., ; Stich, Kinnison, Kocik & Zydlewski, ). The smolts in the present study had a slower migration speed when they passed the power station than in other river stretches.…”

Section: Discussionmentioning

confidence: 99%

Survival and behaviour of Atlantic salmon smolts passing a run‐of‐river hydropower facility with a movable bulb turbine

Thorstad

Havn

Sæther

et al. 2017

Fisheries Management Eco

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Downstream migration of radio‐tagged Atlantic salmon smolts, Salmo salar L., was studied in the Kinzig, Germany, to examine effects of passing a run‐of‐river hydropower station with a movable bulb turbine. Immediate mortality for smolts passing the power station was low (3%–6%), probably facilitated by a curved rack in front of the turbine and the possibility to pass over it. Mortality in the impounded stretch above the power station was also low (1.5% extra mortality compared to a control stretch). The combined mortality due to hydropower was 5%–8%, excluding delayed effects. Most smolts followed the main flow passing through the turbine area (94%). Only few used a fishway (4%) or a nearby millstream (2%). Migration speed was slowed down at the power station, but the passage only caused a short delay (average/median 8.6/1.3 hr). However, even low mortality and short delays at several power stations and reservoirs may have considerable cumulative effects.

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“…Disorientation reduces the speed of migration (Williams ; Noorgard et al . ), which increases mortality due to predation by fish and birds (Rieman et al . ; Jepsen et al .…”

Section: Significance For Other Regionsmentioning

confidence: 99%

“…Similar patterns have been recorded for eels (Acou et al 2008;Carr and Whoriskey 2008;Pedersen et al 2012), which become disorientated in reservoirs during downstream migration. Disorientation reduces the speed of migration (Williams 2008;Noorgard et al 2013), which increases mortality due to predation by fish and birds (Rieman et al 1991;Jepsen et al 1998). Reservoirs can, therefore, significantly impact downstream migrations of salmon and eels.…”

Section: Figurementioning

confidence: 99%

Large reservoirs as ecological barriers to downstream movements of Neotropical migratory fish

2014

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Most large rivers in South America are fragmented by large dams, and a common management strategy to mitigate impacts has been construction of fish passes. Recent studies, however, indicate that downstream passage of adults and young fish is nil or minimal. Better understanding of this phenomenon is needed if fishways are to provide any tangible conservation value in South America. We propose, in this article, that large reservoirs impose a different kind of barrier to migrating fish: impoundments create a diffuse gradient of hydraulic/limnological conditions that affects fish behaviour and functions as an extensive environmental filter that discourages downstream movements. To develop this idea, we characterize the barriers created by dams and reservoirs by describing their distinct nature, the effects on fish migration and potential solutions. We show, for example, that dams generally prevent upstream movements, whereas reservoirs impede mainly downstream movements. In this context, we explain how fish passes, in some instances, can partially mitigate fragmentation caused by dams, but there is no technical solution to solve the barrier effect of reservoirs. In addition, we present a body of empirical evidence that supports the theory that large reservoirs are important barriers to fish migration in South America, we offer an overview of the size of reservoirs to show that impoundments typically have large dimensions, and we discuss the significance of this theory for other regions. Based on current and proposed river regulation scenarios, we conclude that conservation of Neotropical migratory fish will be much more complicated than previously believed.

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MULTIPLICATIVE LOSS OF LANDLOCKED ATLANTIC SALMON Salmo salar L. SMOLTS DURING DOWNSTREAM MIGRATION TROUGH MULTIPLE DAMS

Cited by 42 publications

References 54 publications

Intake Approach and Dam Passage by Downstream‐migrating Atlantic Salmon Kelts

Intake Approach and Dam Passage by Downstream‐migrating Atlantic Salmon Kelts

Survival and behaviour of Atlantic salmon smolts passing a run‐of‐river hydropower facility with a movable bulb turbine

Large reservoirs as ecological barriers to downstream movements of Neotropical migratory fish

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