Tracking the migratory success of stocked European eels Anguilla anguilla in the Baltic Sea


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To investigate the extent to which European silver eels Anguilla anguilla, originating from stocking programmes in the Baltic Sea tributaries, effectively contribute to the spawning stock, two hundred and seventy-four formerly stocked A. anguilla. emigrating from the Schwentine River near Kiel, Germany, were tagged with T-Bar anchor tags. A total of 29 Anguilla spp. were recaptured (c. 11%) up to 14 months after release. Stocking history of recaptured A. anguilla. was confirmed by otolith microchemistry. Recapture locations were concentrated around the outlet of the Baltic Sea (Danish Belt Sea) with 62% of all recaptures reported here or in the Kattegat. Recaptured Anguilla spp. showed a reduction in both LT and mass (mean ± s.d. = −1·5 ± 0·9 cm and −125·3 ± 50·1 g) while average total fat content remained in the order of values previously reported as high enough to provide energy resources to allow successful completion of the spawning migration (mean ± s.d. = 28·4 ± 4·4%). The documented mean rate of travel (0·8 km day−1), however, indicated a delay in the target-oriented migration that might be interpreted as a delayed initial migration phase of orientation towards the exit of the Baltic Sea.