Behaviour, escapement and mortality of female European silver eels within a regulated lowland river draining into the Baltic Sea

Abstract

Migration patterns of 146 female silver eels on their way through fresh and brackish water stretches of the Warnow River into the Baltic Sea were studied using acoustic telemetry. The majority of eels (77%) regained their expected downstream migration behaviour after a median rehabilitation time of 2 days. Positive rheotactic behaviour was observed for 23% of tagged eels after release, probably influenced by experimental procedures. The observed silver eel escapement rate was 63%. Two migratory groups were classified by significantly different migratory speed, time of residence in brackish waters and biometric silvering characteristics. Although the classification of silvering stages is based on these measures, the proportions of these stages did not reflect the observed differences in migratory behaviour. In the context of a permanent silver eel descent in the freshwater part of the Warnow River, a permanent escapement was likewise occurring into the Baltic Sea.

Research, management and conservation of anguillid eels—A global perspective

“…Indeed, barriers to migration are recognised as an issue for all anguillids and Frankowski et al. () reported European silver eel escapement from a German regulated river at 63%. Further, Bolland et al.…”