Otoliths imprinting of sole (Solea solea) from the Bay of Biscay: a tool to discriminate individuals from nursery origins?

Sole nurseries are located in the main bays and estuaries of the Bay of Bis cay, where juveniles from the same stock. concentrate and constitute tempor arily isolated groups. This context being favourable for elemental analyses of juvenile otoliths this study has been initiated with the aim of obtaini ng environmental imprints of the main nurseries of origin of juveniles recr uiting to the adult stock, and of evaluating the relative contribution of t hese nurseries to the stock. The objectives were to compare (i) the otolith elemental imprints obtained by sampling juveniles in the Loire and the Gir onde nurseries, and (ii) two multi-element analysis techniques: laser ablat ion inductively coupled plasma mass spectrometry (LA-ICPMS) and solution-ba sed ICPMS (SB-ICPMS) adapted to small volumes. Depending on the fish origin , differences in Sr and Rb concentrations were shown using LA-ICPMS. Compar isons between the antero-dorsal and postero-ventral sites from where otolit h material was ablated also suggested a spatial heterogeneity in otolith co mposition at least for some metals. From linear discriminant analyses, 73 % and 79 % of individuals (bootstrap estimations) were correctly classified with respect to their origin from the composition of the antero-dorsal and postero-ventral areas, respectively. The SB-ICPMS analysis was more powerfu l, which resulted in an 89 % rate of correct classification from a 2-variab le model (Mg and Cd), whereas a 5-variable model (Li, Mg, Rb, Cd, Th) resul ted in a 91 %, rate of correct classification (bootstrap estimations). Thes e results confirm that sole juveniles from the main estuaries of the French Atlantic coast could be discriminated by the elemental fingerprints of the ir otoliths. (C) 2000 Ifremer/CNRS/IRD/Editions scientifiques et medicales Elsevier SAS.