By using acoustic telemetry, the behaviour and fishery mortality of silver eels Anguilla anguilla (L.) were studied during the early phase of the spawning migration through the Havel River downstream to the river Elbe. A total of 99 female silver eels were implanted with acoustic transmitters and released at two locations in the Havel River system in autumn 2007. Tag recaptures by fisheries were used to assess fishery mortality. Most eels continued their downstream migration immediately after release during October–November in the year of release. However, some eels continued their downstream migration the following spring or autumn; only a few eels migrated in winter and summer. Tagged eels reached the river Elbe from 2 days to more than 1 year after tagging. Fishing efficiency was very high, and by the end of December 2008, only 8% of the tagged eels had reached the river Elbe, whereas 25% were reported caught by commercial fishers and 2% by recreational fishers. The remaining 65% of the tagged eels were unaccounted for at the end of the study period. Copyright © 2011 John Wiley & Sons, Ltd.