Community Research and Development Information Service - CORDIS

Monitoring downstream migration of silver eel by telemetry

The biotelemetry Nedap Trail System proved to be an appropriate system to monitor downstream migration of silver eel. The applicability of transponders was tested in a controlled tank-experiment with 20 tagged and 20 untagged silver eel. No differences in mortality and timing of activities were observed, but activity level was lower in tagged group. A pilot study with 10 silver eel in 2001 was conducted, of which 8 started their migration and 2 made it to the sea. In 2002 a field experiment with 150 silver eel was carried out. Of 125 started their migration of which at least 32, and most probably 38, reached the sea. 16 transponders were recaptured by fishermen. Most eel migrated downstream during end October - early November when river discharge increased. A second migration peak occurred during January. At hydropower stations 63 % passed during 19:00-24:00 hours, indicating that closing the turbines on the days with peak migrations during 5 hours yields a relatively high protection.

Reported by

The Netherlands Institute for fisheries research (RIVO)
Haringkade 1
1970 AB IJMuiden
Netherlands
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