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2004_Gudena: Silver eel migration in the Gudena River, Denmark
Citation
Aarestrup, K., Thorstad, E. B., Koed, A., Svendsen, J. C., Jepsen, N., Pedersen, M. I., & Økland, F. (2004) Silver eel migration in the Gudena River, Denmark.

Availability: Unrestricted after moratorium period
Data are initially restricted, but the access condition relaxes to academic or unrestricted once a specified period of time after an event (such as collection, publication, completion of QC procedures or project cessation) has elapsed

Description
The population of European silver eel Anguilla anguilla has declined tremendously in the last decades. The cause of this decline is unknown, and it is necessary to investigate the migratory behaviour and survival rates of silver eels during the reproductive migration in order to understand if the decline is related to factors acting during that migration. We estimated survival and progression rates of European silver eel migrating in the lower part of the River Gudenaa and during the first phase of the marine migration in the Randers Fjord in Denmark. Fifty migrating silver eel (total body length: 56 to 84 cm) were captured, and each was equipped with an acoustic transmitter. Their migration was subsequently monitored using an array of automatic listening stations, and progression rate and mortality in the river, inner part of the fjord and outer part of the fjord were estimated. more

Survival was high in fresh water. However, 60% of eels were lost in the inner and outer fjord, supporting the hypothesis that mortality is large in the early phase of the marine migration and that fishing may be a major cause of mortality of silver eels. There was no indication that the slowest-migrating individuals were more prone to fishing mortality than the faster-migrating individuals. Progression rate increased as the eels proceeded downriver and out of the fjord. The migration was predominantly nocturnal, both in the river and fjord. Based on the available evidence, a considerable increase in eel survival in the river–fjord system will be needed in order to fulfil the goals in the European Union recovery plan for eels.

Scope
Themes:
Fisheries, Fisheries > Fish stocks/catches/taggings
Keywords:
Marine, Fresh water, Brackish water, Acoustic telemetry, Tracking, Pisces

Temporal coverage
1 January 2004 - 31 December 2005
Quasi continuous (< 1 min.)

Taxonomic coverage
Pisces [WoRMS]

Contributors
Norwegian Institute for Nature Research (NINA), moredata creator
Technical University of Denmark; National Institute of Aquatic Resources (DTU Aqua), moredata creator

Related datasets
Parent dataset:
ETN data: fish acoustic receiver network, more

Dataset status: Completed
Data type: Data
Data origin: Research: field survey
Metadatarecord created: 2019-11-22
Information last updated: 2020-02-28
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