ICES Journal of Marine Science: Journal du Conseil Advance Access originally published online on September 5, 2007
ICES Journal of Marine Science: Journal du Conseil 2007 64(7):1450-1456; doi:10.1093/icesjms/fsm130
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Assessment of population size and migration routes of silver eel in the River Rhine based on a 2-year combined mark-recapture and telemetry study
1 VIVION BV, Händelstraat 18, 3533GK Utrecht, The Netherlands
2 Visadvies BV, Vondellaan 14, 3521 GD Utrecht, The Netherlands
3 Zoologisches Institut, Universität zu Köln, Allgemeine Ökologie und Limnologie, Ökologische Forschungsstation, 46459 Rees-Grietherbusch, Germany
4 Rijksinstituut voor Integraal Zoetwaterbeheer en Afvalwaterbehandeling, Postbus 17, 8200 AA Lelystad, The Netherlands
5 Struktur und Genehmigungsbehörde Nord Rheinland-Pfalz, Postfach 200361, 56003 Koblenz, Germany
6 Rheinfischereigenossenschaft im Lande Nordrhein-Westfalen, Römerhofweg 12, 50374 Erftstadt, Germany
7 Sportvisserij Nederland, Postbus 162, 3720 AD Bilthoven, The Netherlands
8 Bezirksregierung Arnsberg, Heinsbergerstr. 53, 57399 Kirchhundem-Albaum, Germany
Correspondence to D. Ingendahl: tel: +49 272377 940; fax: +49 272377 977; e-mail: detlev.ingendahl{at}bezreg-arnsberg.nrw.de
Klein Breteler, J., Vriese, T., Borcherding, J., Breukelaar, A., Jörgensen, L., Staas, S., de Laak, G., and Ingendahl, D. 2007. Assessment of population size and migration routes of silver eel in the River Rhine based on a 2-year combined mark-recapture and telemetry study. – ICES Journal of Marine Science, 64: 1450–1456.More than 3000 female silver eels >50 cm were marked and released in the River Rhine at Cologne in 2004 and 2005, and more than 4000 and 6000 per year, respectively, were checked for marks in the different Rhine branches close to the sea. Migration pathways of downstream-migrating eels were also tracked by telemetry from the point of release (300–350 km from the sea, depending on the migration route) through the three main branches of the Rhine (Waal, Nederrijn + Lek, IJssel + Lake IJsselmeer) to the sea. Downstream migration to the sea took from <2 d to more than a year, but was generally in October and November of the year of release. Most successful migrators seemed to find their way to the sea via the Nieuwe Waterweg rather than via Lake IJsselmeer or Haringvliet. Some 23% of released eels of the 2004 cohort and 15% of the 2005 cohort made it to the sea in less than 2 years. The telemetry data suggest that the Nederrijn + Lek watercourse, the only location where hydropower stations have been built in the lower Rhine system, might be important for downstream migration of eels only in the years with greater discharges, suggesting that management measures should concentrate on the Waal and downstream sections to improve spawning escapement of the silver eel population of the Rhine system.
Keywords: Anguilla anguilla, eel, mark-recapture, migration, population size, Rhine, silver eel, telemetry
Received 3 January 2007; accepted 13 July 2007; advance access publication 5 September 2007.