Corner and sloped culvert baffles improve the upstream passage of adult European eels (Anguilla anguilla)
Corner and sloped culvert baffles improve the upstream passage of adult European eels (Anguilla anguilla)
Installation of baffles intended to improve fish passage through culverts can reduce discharge capacity and trap debris, increasing flood risk. A sloping upstream face may reduce this risk, but new designs must be tested for fish passage efficiency. The European eel (Anguilla anguilla) is a critically endangered species, yet the suitability of even common baffle types to aid upstream movement has not been tested. This study compared the water depth, velocity, turbulent kinetic energy (TKE), and upstream passage performance of adult yellow-phase eels, between three 6 m long culvert models: smooth and unmodified (control); containing corner baffles (treatment 1); and with prototype sloped baffles installed (treatment 2). Passage of individual fish was assessed during 25 one-hour trials per model. Performance was quantified as entrance efficiency, number of entries per fish, passage efficiency, and overall efficiency. Total and passage delay, and successful passage time were also evaluated. Despite some individuals being able to swim against unexpectedly high water velocities (>1.5 m s?1 for 4 m), passage performance in the control was poor, with an overall efficiency of 28%. Compared to the control, both treatments increased the mean centreline water depth by approximately 0.11 m, created heterogeneous flow conditions with low velocity resting areas, and reduced maximum velocities. As a result, entrance rate and all efficiency parameters were higher for the treatments than for the control (overall efficiency = 84%), despite longer passage delay. The TKE was slightly higher in treatment 2 than 1, but there was no difference in water depth or overall efficiency. The findings show that both corner and sloped baffles can mitigate for impeded upstream adult eel movement. The extent to which the sloping upstream face will improve debris transport should be explored further.
anguilliforms, waterway crossings, fish passage, river restoration, hydrodynamics
752-759
Newbold, L.R.
aa48f87e-fcf0-4a7e-a9c9-98437c2a4585
Karageorgopoulos, P.
1a2b4f3d-21d0-4db3-a645-b77a68d1638d
Kemp, P.S.
9e33fba6-cccf-4eb5-965b-b70e72b11cd7
December 2014
Newbold, L.R.
aa48f87e-fcf0-4a7e-a9c9-98437c2a4585
Karageorgopoulos, P.
1a2b4f3d-21d0-4db3-a645-b77a68d1638d
Kemp, P.S.
9e33fba6-cccf-4eb5-965b-b70e72b11cd7
Newbold, L.R., Karageorgopoulos, P. and Kemp, P.S.
(2014)
Corner and sloped culvert baffles improve the upstream passage of adult European eels (Anguilla anguilla).
Ecological Engineering, 73, .
(doi:10.1016/j.ecoleng.2014.09.076).
Abstract
Installation of baffles intended to improve fish passage through culverts can reduce discharge capacity and trap debris, increasing flood risk. A sloping upstream face may reduce this risk, but new designs must be tested for fish passage efficiency. The European eel (Anguilla anguilla) is a critically endangered species, yet the suitability of even common baffle types to aid upstream movement has not been tested. This study compared the water depth, velocity, turbulent kinetic energy (TKE), and upstream passage performance of adult yellow-phase eels, between three 6 m long culvert models: smooth and unmodified (control); containing corner baffles (treatment 1); and with prototype sloped baffles installed (treatment 2). Passage of individual fish was assessed during 25 one-hour trials per model. Performance was quantified as entrance efficiency, number of entries per fish, passage efficiency, and overall efficiency. Total and passage delay, and successful passage time were also evaluated. Despite some individuals being able to swim against unexpectedly high water velocities (>1.5 m s?1 for 4 m), passage performance in the control was poor, with an overall efficiency of 28%. Compared to the control, both treatments increased the mean centreline water depth by approximately 0.11 m, created heterogeneous flow conditions with low velocity resting areas, and reduced maximum velocities. As a result, entrance rate and all efficiency parameters were higher for the treatments than for the control (overall efficiency = 84%), despite longer passage delay. The TKE was slightly higher in treatment 2 than 1, but there was no difference in water depth or overall efficiency. The findings show that both corner and sloped baffles can mitigate for impeded upstream adult eel movement. The extent to which the sloping upstream face will improve debris transport should be explored further.
Text
Newbold et al 2014 Corner and sloped baffles European eel.pdf
- Accepted Manuscript
More information
Published date: December 2014
Keywords:
anguilliforms, waterway crossings, fish passage, river restoration, hydrodynamics
Organisations:
Water & Environmental Engineering Group
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Local EPrints ID: 370540
URI: http://eprints.soton.ac.uk/id/eprint/370540
ISSN: 0925-8574
PURE UUID: 5a863346-f8a6-4491-a38a-74b202154d8e
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Date deposited: 28 Oct 2014 17:13
Last modified: 15 Mar 2024 03:21
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Author:
L.R. Newbold
Author:
P. Karageorgopoulos
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