Linking natural and electronic data records to assess population dispersal and lifetime migration in North Sea Plaice

Current fisheries management advice is limited by a lack of knowledge on the spatialdynamics of commercially important fish stocks. To describe the lifetime movements ofplaice (Pleuronectes platessa L.) in the North Sea, we combined two state-of-the-art techni-ques: fish tagging with electronic data storage tags (DSTs) and otolith microchemistry. DSTdata allowed detailed reconstruction of the geographical movements of more than 160 free-swimming adult plaice and provided continuous records of ambient temperature for periodsof up to 18 months. By matching DST data with seasonal growth-ring composition in theotoliths of 40 of these fish, we attempted to establish the retrospective positioning of thesefish in space and time throughout their adult lives. Otoliths obtained from juveniles sampledfrom the main nursery areas of the English Channel and North Sea where also analyzed fordifferences in trace element composition. By matching the chemical signatures obtained foreach nursery area with the elemental composition of otolith core in DST tagged fish, we at-tempted to link pre- and post recruitment behaviour in plaice. By providing information onpopulation structure and dynamics that would be unattainable using conventional methods,the results from this study have the potential to significantly improve the parameterisation ofassessment methods currently applied in fisheries management.