Screening at intakes and outfalls: measures to protect eel (<i>Anguilla anguilla</i>)

Sheridan, S.; Turnpenny, A.; Horsfield, R.; Solomon, D.; Bamford, D.; Bayliss, B.D.; Coates, S.; Dolben, I.; Frear, P. A.; Hazard, E.; Tavner, I.; Trudgill, N.; Wright, Rosalind M.; Aprahamian, M. W.

doi:10.2495/978-1-84564-849-7/002

Cited by 6 publications

(6 citation statements)

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“…The presence of exclusion structures or deterrents can greatly reduce entrainment risks for affected species (Nobriga et al, 2004;Rahel & McLaughlin, 2018). Fish screens are the most common form of exclusion and can range regarding open space for passage from racks with vertical bars to fine-meshed screens (Baumgartner, 2005;Rahel & McLaughlin, 2018;Sheridan et al, 2011). Specific types in use include rotary drum screens, vertical and nonvertical fixed plate screens, vertical travelling screens, high-velocity screens and pump intake screens (Nordlund, 2008).…”

Section: Management Options For Mitigating Entrainmentmentioning

confidence: 99%

A review of potential factors promoting fish movement in inter‐basin water transfers, with emergent patterns from a trait‐based risk analysis for a large‐scale project in china

Schmidt

Wang

Ren

et al. 2019

Ecology of Freshwater Fish

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Inter‐basin water transfers create new pathways between previously disjunct systems and communities. If fish movement occurs, it can lead to invasion or altered regional connectivity patterns, which could induce biotic/genetic homogenisation or synchronisation. Understanding ecological factors promoting movement is critical for predicting potential impacts during project planning, to assess ongoing effects, and to develop mediation strategies. Potential characteristics influencing movement rates were reviewed, including intrinsic traits that increase passive entrainment or active dispersal rates, extrinsic traits of the connected environments and their interactions. In order to examine patterns among these potentially influencing characteristics, a trait‐based screening method for movement and invasion risk was developed to analyse linked communities in a database from a large‐scale inter‐basin water diversion in China. Groups of fishes that scored high in the risk assessment were compared with worldwide examples of entrainment in inter‐basin water transfer systems or smaller‐scale diversions to examine emergent patterns of shared ecological characteristics. Specific traits that were most often shared in these groups, indicating a higher likelihood of movement in water diversions, include the following: a smaller body size, high adult or larval abundance, migratory behaviour, generalist and pelagic habitat preferences, and a high reproductive output. The synthesis of factors identified in this research can be used to guide future empirical studies to fill knowledge gaps regarding ecological impacts of inter‐basin water transfers or other smaller‐scale diversions on local communities and ecosystems.

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Section: Management Options For Mitigating Entrainmentmentioning

confidence: 99%

A review of potential factors promoting fish movement in inter‐basin water transfers, with emergent patterns from a trait‐based risk analysis for a large‐scale project in china

Schmidt

Wang

Ren

et al. 2019

Ecology of Freshwater Fish

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“…The minimal relative bypass discharge Q by /Q o should be in the range of 2 to 5% of the approach flow discharge Q o for angled racks and 5 to 10% for racks installed frontally, non-oblique to the approach flow (Larinier, 1998;Odeh & Orvis, 1998;Courret & Larinier, 2008;Hefti, 2012;Sheridan et al, 2014;Ebel, 2016). The fish passage engineering design criteria of the U.S.…”

Section: State-of-the-art Of Fish Bypass Systemsmentioning

confidence: 99%

Effect of bypass layout on guidance of downstream moving fish at bar rack bypass systems

Boes¹,

Beck²,

Meister³

et al. 2022

Proceedings of the 39th IAHR World Congress

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Hydropower plants act as a barrier to fish moving in rivers. Fish guidance structures like angled bar racks with horizontal or vertical bars are used to protect downstream moving fish from turbine passage, guiding them to a bypass as an alternative passage corridor. The function of the bypass system is to safely collect, carry and reintroduce the fish to the river downstream of the barrier. An effective bypass design is essential to ensure both fish protection and guidance to the tailwater. Most importantly, a bypass must be designed according to the swimming capacity and behavior of the target fish species. A gradual velocity increase into the bypass leads to high acceptance, being a prerequisite for high fish guidance efficiencies. The bypass entrance should be easily found, accepted and passed by all fish species without harm, delay, flight or exhaustion. The findings of two recent studies on bar rack bypass systems with (i) curved vertical and (ii) horizontal bars of different spacing indicate, amongst others, that an open channel bypass was quickly accepted by fish for mild velocity gradients at the inlet. In contrast, restrictor and pipe bypasses led to backwater with low flow velocities and high local velocity gradients in front of the bypass opening(s), leading to an avoidance reaction of fish. Although most available guidelines recommend a bypass discharge as a percentage of the water intake discharge, the present results suggest that the spatial velocity gradient in front of the bypass is the decisive parameter for an efficient bypass design to be quickly accepted by fish.

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“…However, these are not wholly effective and can incur high construction and maintenance costs [ 21 , 24 ]. Due to their small size, juvenile eel are unlikely to be blocked by existing screens designed for larger target species and life-stages and hence require expensive retrofits with very narrow-spaced designs (1–2 mm) [ 25 ]. Furthermore, eel may be impinged on poorly designed screens and suffocate if they are unable to escape because the velocities at the screen face exceed their burst swimming capabilities [ 21 , 24 ].…”

Section: Introductionmentioning

confidence: 99%

Response of upstream migrating juvenile European eel (Anguilla anguilla) to electric fields: Application of the marginal gains concept to fish screening

2022

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The decline in European eel (Anguilla anguilla) recruitment over the past half-century is partly due to river infrastructure that delays or blocks upstream migration to rearing habitat. Stimuli, such as electricity, can be used to modify the behaviour of downstream moving fish and guide them to preferred routes of passage at river infrastructure; but research on upstream migrating juvenile eel remains limited. The response of upstream migrating juvenile eel exposed to pulsed direct current (PDC) electric fields was investigated using a recirculatory flume. Eel were presented a choice of two routes upstream under either: (1) a treatment condition, in which the selection of one route resulted in exposure to High Electric Field (HEF) strength that was between 1.5–2 times stronger than the Low Electric Field (LEF) strength encountered in the alternative route; or (2) a control in which the electric field was absent in both routes. Under the treatment, five different mean HEF strengths (0.53, 0.77, 1.22, 2.17 and 3.74 Vcm-1) were tested at one of two frequencies (2 and 10 Hz). Route choice, distance downstream of the first set of electrodes at which an initial response was observed and avoidance behaviours (acceleration, retraction, switching and rejection) were compared among treatments. For the 1.22, 2.17 and 3.74 Vcm-1 and under 2 Hz, eel preferred to pass the LEF route. Avoidance was greater in the HEF route and positively related to field strength. The distance of the initial response did not differ between routes, field strengths or frequency. Upstream migrating eel avoided electric fields indicating potential to develop this approach for fish guidance. Further work is needed to test prototypes in field settings, particularly in combination with traditional physical screens to water intakes as part of a process of applying the concept of marginal gains to advance environmental impact mitigation technology.

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Screening at intakes and outfalls: measures to protect eel (Anguilla anguilla)

Cited by 6 publications

References 0 publications

A review of potential factors promoting fish movement in inter‐basin water transfers, with emergent patterns from a trait‐based risk analysis for a large‐scale project in china

A review of potential factors promoting fish movement in inter‐basin water transfers, with emergent patterns from a trait‐based risk analysis for a large‐scale project in china

Effect of bypass layout on guidance of downstream moving fish at bar rack bypass systems

Response of upstream migrating juvenile European eel (Anguilla anguilla) to electric fields: Application of the marginal gains concept to fish screening

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