ACCURATE CLASSIFICATION OF JUVENILE WEAKFISH CYNOSCION REGALIS TO ESTUARINE NURSERY AREAS BASED ON CHEMICAL SIGNATURES IN OTOLITHS

We investigated the ability of trace element and isotopic signatures i n otoliths to record the nursery areas of juvenile (young-of-the-year) weakfish Cynoscion regalis from the east coast of the USA. Juvenile C . regalis were captured with otter trawls at multiple sites in Doboy S ound (Georgia), Pamlico Sound (North Carolina), Chesapeake Bay (Virgin ia), Delaware Bay (Delaware) and Peconic Bay (New York), from July to September 1996. One sagittal otolith from each specimen was assayed fo r Mg/Ca, Mn/Ca, Sr/Ca and Ba/Ca ratios using inductively coupled plasm a mass spectrometry (ICP-MS), while delta(13)C and delta(18)O Values f rom the other sagittal otolith in the pair were determined using isoto pe ratio mass spectrometry (IR-MS). A multivariate analysis of varianc e determined that there were significant differences in trace element signatures among locations. Bootstrapped 95% confidence ellipses on ca nonical variates indicated that all 5 locations were significantly iso lated in discriminant space. On the basis of these differences, linear discriminant function analysis (LDFA) and artificial neural network ( ANN) models were used to classify individual fish to their natal estua ry with an overall error rate of 37 % for LDFA and 29.6% for ANN. Addi tion of delta(13)C and delta(18)O values to the LDFA and ANN models de rived from the trace element data resulted in overall error around 10% . We will, therefore, be able to use chemical signatures from the juve nile portion of adult C. regalis otoliths to accurately classify these fish to their natal estuary.