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The Response of River-Resident Fish to Reservoir Freshet Releases of Varying Profiles Intended to Facilitate a Spawning Migration

Baker, N. J.; Taylor, M. J.; Harvey, J. P.; Angelopoulos, N. V.; Smith, M. A.; Noble, R. A.; Tinsdeall, M.; Baxter, J.; Bolland, J. D.; Baker, Nicola; Taylor, Marie; Cowx, I. G.; Harvey, Jon; Nunn, A. D.; Angelopoulos, Natalie; Smith, Michelle; Noble, Richard; Tinsdeall, Mark; Baxter, Joe; Bolland, Jon


N. J. Baker

M. J. Taylor

J. P. Harvey

N. V. Angelopoulos

M. A. Smith

R. A. Noble

M. Tinsdeall

J. Baxter

J. D. Bolland

Nicola Baker

Marie Taylor

I. G. Cowx

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Dr Jon Harvey
Senior Lecturer in Fisheries Science

Natalie Angelopoulos

Michelle Smith

Mark Tinsdeall

Joe Baxter


Natural hydrological regimes encompass varying seasonal flow characteristics that provide fish with cues and opportunities for upstream spawning migrations, but these flows are often modified/absent in regulated rivers. Compensatory artificial flows (freshets) can be released from reservoirs to replicate these characteristics, but studies testing their effectiveness are limited. To address this, river‐resident brown trout, a species known to undertake spawning migrations, were manually tracked using radio telemetry in a regulated upland river in northern England in response to 11 freshet releases of differing timing, magnitude and duration. Spawning migrations were not observed because extent of movement during freshets was generally small and the pattern of movement (i.e. directionality and relocation indices) was comparable between impact/control reaches. Movements during freshets were comparable with those observed the days immediately before/after and were small relative to the entire tracking period. In conclusion, freshets characteristic of those recommended to produce “naturalized” autumn/winter flow elevations did not stimulate/facilitate spawning migrations of river‐resident brown trout under the given seasonal conditions. Outside freshets, longer unidirectional movements occurred during low flow periods and elevated river level due to rainfall, including during periods of reservoir overtopping. Notwithstanding, fish in experimental reaches were significantly more active (total distance moved) and occupied a larger extent of river (range during freshet) than those in control reaches during short‐duration freshets. Therefore, during dry years/when (autumn/winter) reservoir overtopping events are unlikely, small‐magnitude freshets providing flows that allow fish short opportunities to search for/find superior local habitat whilst minimising total water released are recommended.


Baker, N. J., Taylor, M. J., Harvey, J. P., Angelopoulos, N. V., Smith, M. A., Noble, R. A., Tinsdeall, M., Bolland, J. D., Baxter, J., Baker, N., Taylor, M., Cowx, I. G., Harvey, J., Nunn, A. D., Angelopoulos, N., Smith, M., Noble, R., Tinsdeall, M., Baxter, J., & Bolland, J. (2020). The Response of River-Resident Fish to Reservoir Freshet Releases of Varying Profiles Intended to Facilitate a Spawning Migration. Water Resources Research, 56(6), Article e2018WR024196.

Journal Article Type Article
Acceptance Date Jan 5, 2020
Online Publication Date Jan 29, 2020
Publication Date 2020-06
Deposit Date Feb 6, 2020
Publicly Available Date Jul 30, 2020
Journal Water Resources Research
Print ISSN 0043-1397
Publisher American Geophysical Union
Peer Reviewed Peer Reviewed
Volume 56
Issue 6
Article Number e2018WR024196
Keywords River regulation; Freshet; Migration barrier
Public URL
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©2020 American Geophysical Union. All rights reserved.

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