Otolith microchemistry to investigate nursery site fidelity and connectivity of juvenile European sea bass in Ireland

Abstract

Knowledge of the role that nurseries play in the growth and survival of juvenile European sea bass Dicentrarchus labrax is essential to provide information for sustainable stock management. To examine D. labrax nursery fidelity, multi-annual geochemical tags from the otoliths of 385 juveniles (0-group, 1-group and 2-group) were collected in 4 estuaries along the south coast of Ireland, close to the northern limit of its range. This study identified high between-estuary discrimination of 0-group otolith geochemical tags over multiple years. It also confirmed that over 91% of captured 1-group D. labrax remain close to their original settlement sites irrespective of sampling year. Although the capture in individual estuaries of 2-group D. labrax was less common, otolith geochemical tags indicated >95% fidelity to their original settlement sites. Where migration between estuaries was inferred, it was restricted to an adjacent estuary (<50 km coastal distance). The consistency of the multi-annual geochemical tag signatures observed will enable assignment of nursery origin to adult D. labrax which disperse around the coast of Ireland and ultimately allow the identification of estuary nursery sites that contribute most to the adult stock.