Low mortality rate in silver eels (Anguilla anguilla L.) passing through a small hydropower station

Bernaś, Rafał; Dębowski, P.; Skóra, Michał; Radtke, Grzegorz; Morzuch, Jacek; Kapusta, Andrzej

doi:10.1071/mf16396

Cited by 5 publications

(5 citation statements)

References 16 publications

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“…Many factors affect turbine-induced mortality including turbine type, speed, hydroelectric generating station head, and size of outmigrating eel (Eyler et al, 2016). Turbine type affects mortality (Bernas et al, 2017) with eels generally experiencing higher mortality rates when passing through Kaplan turbines than Francis turbines (Winter, Jansen, & Breukelaar, 2007), whereas small Kaplan turbines can have a 100% mortality rate given the high rate of spin and closeness of the blades (Haro et al, 2000). In contrast, small Francis turbines results in mortality rates between 6% and 24% (EPRI, 2001), medium sized Francis turbines are similar to Kaplan turbines (Eyler et al, 2016) but may be as high as 60% (Calles et al, 2010) and large…”

Section: Mortality At a Generating Stationmentioning

confidence: 99%

Cumulative downstream turbine‐induced mortality and thresholds for facilitating upstream passage of American eel

Haxton

2021

River Research & Apps

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American eels (Anguilla rostrata) are vulnerable to turbine-induced mortality during outmigration along regulated rivers. Turbine-induced mortality is cumulative when multiple facilities are encountered along the route. This level of mortality may be unsustainable such that facilitating upstream movement ostensibly for recovery purposes, may in fact be detrimental to the population or an ecological trap. The objectives of this study were to estimate a theoretical threshold for facilitating upstream movement passed hydroelectric facilities and estimating cumulative turbine mortality within waterbodies across American eel's historical range within Ontario, Canada. A stagestructured model was used to estimate mortality thresholds parameterized by published life stage survival probabilities using a maternal effect and altering silver eel survival to mimic turbine mortality. The threshold was exceeded when population growth (λ) declined below 1.0. Site mortality was estimated based on the generating station characteristics including turbine type, size, proportion of flow through turbines, and sluice gate height. Cumulative mortality within a waterbody was projected using a Bayesian network (i.e., conditional probability) and the calculated site-specific mortality. The survival required for a stable population using the stage-structured model was 0.75; (0.65-0.85) therefore, annual mortality greater than 0.25 (0.15-0.35) would result in population decline (λ < 1). The effects of turbine mortality increased with additional hydroelectric facilities encountered along the route. Across Ontario, there was no eel habitat deemed to be safe in terms of levels of cumulative turbine mortality during outmigration. Moreover, 89.1% of eel habitat was considered to be within the cautionary range of turbine mortality, whereas 10.9% of eel habitat was considered to be above the threshold for sustainable passage during outmigration. Lake Ontario accounted for 98.2% of the area within the cautionary range, whereas most of the tributaries and watersheds associated with the Ottawa River and Lake Ontario were above the threshold.

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Section: Mortality At a Generating Stationmentioning

confidence: 99%

Cumulative downstream turbine‐induced mortality and thresholds for facilitating upstream passage of American eel

Haxton

2021

River Research & Apps

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“…Stocks of European eel Anguilla anguilla (l. 1758) and American eel ( Anguilla rostrata LeSueur 1817) have declined over past decades (Bernaś et al ., ; Bruijs & Durif, ; Dainys et al ., ; Dekker, ; EPRI, ; Travade et al ., ). Among a host of causative factors ( e.g ., overfishing, dam construction, habitat loss, etc .)…”

Section: Introductionmentioning

confidence: 98%

“…Despite concerns on the fate of silver eels passing through hydro turbines, published literature is relatively sparse compared with that on emigrating clupeids and salmonids. EPRI's (, ) review and of others (Bernaś et al ., ; Bruijs & Durif, ; Calles, ; Dainys et al ., ; Larinier & Travade, ; Travade et al ., ) indicated that earlier passage studies primarily utilised netting systems to capture turbine‐passed emigrating silver eels. A large amount of variation (mortality of between 15 and 38% at large propeller turbines and 50 to 100% at small turbines for European eel) was noted across sites in these uncontrolled field studies (Bernaś et al ., ; Bruijs & Durif, ).…”

Section: Introductionmentioning

confidence: 99%

“…EPRI's (, ) review and of others (Bernaś et al ., ; Bruijs & Durif, ; Calles, ; Dainys et al ., ; Larinier & Travade, ; Travade et al ., ) indicated that earlier passage studies primarily utilised netting systems to capture turbine‐passed emigrating silver eels. A large amount of variation (mortality of between 15 and 38% at large propeller turbines and 50 to 100% at small turbines for European eel) was noted across sites in these uncontrolled field studies (Bernaś et al ., ; Bruijs & Durif, ). More recently, however, telemetry techniques have been used to estimate mortality for downstream migration of silver European eel through turbines (Dainys et al ., ; Winter et al ., ).…”

Section: Introductionmentioning

confidence: 99%

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Passage survival of European and American eels at Francis and propeller turbines

Heisey¹,

Mathur²,

Phipps³

et al. 2019

Journal of Fish Biology

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We present the magnitude of losses of European eel Anguilla anguilla and American eel A. rostrata in passage through propeller and Francis turbines at hydroelectric projects. Survival and injury rates and types were turbine type related. Overall, eel survival was higher (mean ± 90% CI = 95.1 ± 5.3%,) and injury rate lower (12.5 ± 10.5) at Francis than propeller turbines (survival = 80.7 ± 6.4%; injury rate = 25.7 ± 7.9%). The common injury type at Francis turbines was bruises and at propeller turbines was severance. Blade shape and thickness of the leading edge of the blades (rounded, thick buckets of Francis turbines v. flatter, sharper edged blades in propeller turbines); eel entry routes into the turbines; their flexible, cylindrical body shape and orientation probably contributed to these differences. Relationship between survival and injury and turbine characteristics was turbine specific. For Francis turbines, one negative correlation (r = −0.986, P < 0.01) between survival and runner speed was found and two positive correlations between injury rates and fish length (r = 0.740, P < 0.10) and number of blades (r = 0.835, P < 0.05) were noted for propeller turbines. Several severely injured eels remained active 48 h after turbine passage suggesting caution is warranted when using telemetric movement for estimating eel survival. We conclude there is a need to (a) better understand travel paths and approach orientation of eels through turbines; (b) determine where only eel passage is of concern at hydropower plants that have both turbine types and therefore preferential operation of Francis turbines may be considered; (c) inform hydropower plant operators where turbine replacement is being considered and downstream eel passage is of concern that replacement by Francis or bulb turbines may prove beneficial for eel passage.

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“…The abundance of global eel populations, including in China, has declined significantly over the past few decades, with a 90% reduction in fishing production [8][9][10][11]. Eels migrating upstream are easily drawn into the blades of different turbines by their attraction currents and even die [12,13]. Although mechanical damage to the turbine is avoided, the continuous climbing of the eels over the spillway greatly increases their migration time and covertly reduces their survival rate [14].…”

Section: Introductionmentioning

confidence: 99%

Response of Upstream Behavior and Hydrodynamic Factors of Anguilla Japonica in a Combined Bulkhead Fishway under Tidal Conditions

Zhou

Lian

Bai

et al. 2023

Water

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Frequent changes in the tide levels in estuaries cause constant changes in the hydraulics of fish passage systems, with important effects on successful fish passage and swimming behavior. In most cases, Japanese eels often have low passage rates in engineered fishways because of their special habits. In this study, we established a 1:4 scaled-down weir-hole combination bulkhead fishway, studied the effects of different tidal differences and water depths on the passage rates and swimming behavior of yellow-phase Japanese eels, and analyzed the response of the Japanese eels to the hydraulic factors by superimposing their swimming trajectories and the flow field simulation results. We found that the passage rate of the eels decreased from 68.18% to 50.00% and 45.45% under extreme high tide differences and extreme low tide differences, respectively. The eels tended to use the low-velocity area to climb up the wall, and when crossing the mainstream, the yellow-phase Japanese eels preferred the area with a flow velocity of 0.1~0.36 m/s and a turbulent kinetic energy range of 0.001~0.007 m2/s2. Their upstream swimming speed was maintained at a range of 0.1~0.3 m/s.

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Low mortality rate in silver eels (Anguilla anguilla L.) passing through a small hydropower station

Cited by 5 publications

References 16 publications

Cumulative downstream turbine‐induced mortality and thresholds for facilitating upstream passage of American eel

Cumulative downstream turbine‐induced mortality and thresholds for facilitating upstream passage of American eel

Passage survival of European and American eels at Francis and propeller turbines

Response of Upstream Behavior and Hydrodynamic Factors of Anguilla Japonica in a Combined Bulkhead Fishway under Tidal Conditions

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