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Impact of tide gates on the migration of adult European Eels, Anguilla anguilla

Impact of tide gates on the migration of adult European Eels, Anguilla anguilla
Impact of tide gates on the migration of adult European Eels, Anguilla anguilla
Tide gates form a temporal barrier to fish migration, closing during the flood tide and opening during the ebb, primarily for flood prevention and land reclamation. Their impact on downstream adult migration of the critically endangered European eel, Anguilla anguilla, is unknown. The River Stiffkey, UK, has three top-hung tide gates (one counterbalanced, two not) through which it discharges into the North Sea. Adult eels of silver appearance (n?=?118) were caught between 0.5 and 6.0 km upstream from the tide gates in Autumn 2011 and implanted with 23 mm half-duplex passive integrated transponder (PIT) tags. Tagged individuals were detected by PIT antennae located near the tide gates. Of the eels tagged, 80 were detected actively migrating downstream to the gates. Escapement past the gates was 98.3 %. Speed of migration was slower near the gates than for an unimpeded upstream reach and was positively and negatively related to mean degree of gate opening and mean light intensity, respectively. When the largest gate was modified through installation of an orifice intended to improve upstream passage of sea trout and juvenile eels, downstream migration was more rapid when it was operating. However, video analysis revealed that eels did not pass through the orifice, meaning that faster migration may have been a result of the gates being open on more occasions when eels initially approached them, or the lower tides and upstream saline intrusion that occurred during these periods. Top-hung tide gates in the River Stiffkey delayed eel migration, potentially increasing the risk of predation and energy expenditure immediately prior to a 5000–6000 km migration to spawning grounds in the Sargasso Sea
silver eel, tide gate, escapement, passage efficiency, delay
1559-2723
2031-2043
Wright, G.V.
ccc5ddf5-fda4-42b6-b511-43b4a4248198
Wright, R.M.
3a09b49d-87d1-4b85-9063-d1093de9a3b1
Kemp, P.S..
9e33fba6-cccf-4eb5-965b-b70e72b11cd7
Wright, G.V.
ccc5ddf5-fda4-42b6-b511-43b4a4248198
Wright, R.M.
3a09b49d-87d1-4b85-9063-d1093de9a3b1
Kemp, P.S..
9e33fba6-cccf-4eb5-965b-b70e72b11cd7

Wright, G.V., Wright, R.M. and Kemp, P.S.. (2015) Impact of tide gates on the migration of adult European Eels, Anguilla anguilla. Estuaries and Coasts, 38 (6), 2031-2043. (doi:10.1007/s12237-014-9931-1).

Record type: Article

Abstract

Tide gates form a temporal barrier to fish migration, closing during the flood tide and opening during the ebb, primarily for flood prevention and land reclamation. Their impact on downstream adult migration of the critically endangered European eel, Anguilla anguilla, is unknown. The River Stiffkey, UK, has three top-hung tide gates (one counterbalanced, two not) through which it discharges into the North Sea. Adult eels of silver appearance (n?=?118) were caught between 0.5 and 6.0 km upstream from the tide gates in Autumn 2011 and implanted with 23 mm half-duplex passive integrated transponder (PIT) tags. Tagged individuals were detected by PIT antennae located near the tide gates. Of the eels tagged, 80 were detected actively migrating downstream to the gates. Escapement past the gates was 98.3 %. Speed of migration was slower near the gates than for an unimpeded upstream reach and was positively and negatively related to mean degree of gate opening and mean light intensity, respectively. When the largest gate was modified through installation of an orifice intended to improve upstream passage of sea trout and juvenile eels, downstream migration was more rapid when it was operating. However, video analysis revealed that eels did not pass through the orifice, meaning that faster migration may have been a result of the gates being open on more occasions when eels initially approached them, or the lower tides and upstream saline intrusion that occurred during these periods. Top-hung tide gates in the River Stiffkey delayed eel migration, potentially increasing the risk of predation and energy expenditure immediately prior to a 5000–6000 km migration to spawning grounds in the Sargasso Sea

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Accepted/In Press date: 16 December 2014
Published date: 13 January 2015
Keywords: silver eel, tide gate, escapement, passage efficiency, delay
Organisations: Water & Environmental Engineering Group

Identifiers

Local EPrints ID: 382838
URI: http://eprints.soton.ac.uk/id/eprint/382838
ISSN: 1559-2723
PURE UUID: 1de97886-505f-4bd2-aa81-05e26c018a13
ORCID for P.S.. Kemp: ORCID iD orcid.org/0000-0003-4470-0589

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Date deposited: 02 Nov 2015 14:52
Last modified: 15 Mar 2024 03:21

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Contributors

Author: G.V. Wright
Author: R.M. Wright
Author: P.S.. Kemp ORCID iD

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