MEPS 371:243-252 (2008)  -  DOI: https://doi.org/10.3354/meps07604

ABSTRACT: Early juvenile spotted seatrout Cynoscion nebulosus (n = 199) were collected during late summer and autumn 2001 from shoreline habitats within 9 coastal regions bordering Mississippi Sound in the north-central Gulf of Mexico to ascertain how well fish could be spatially classified based on otolith chemistry. Left otoliths were assayed for trace element:Ca ratios of Ba, Li, Mg, Mn and Sr, and right otoliths for δ¹³C and δ¹⁸O. Significant overall differences in otolith chemistry existed among the 9 regions; 61% of the joint variance in the 7 otolith chemistry variables was explained by the regional factor in a multivariate analysis of variance (MANOVA). All 7 otolith chemistry variables differed significantly among the 9 regions. The isotopes δ¹³C and δ¹⁸O showed the highest regional affinities, and Li showed the strongest regional association of all the trace elements. Canonical discriminant function analysis (CDFA) maximally separated regional groups of early juvenile fish. The first 3 of 7 discriminant functions accounted for 97.5% of the cumulative variance in the 7 otolith chemistry variables. CDF 1 was influenced primarily by δ¹⁸O and Li, CDF 2 by Mn and δ¹³C, and CDF 3 by Mg and Ba. In the all-inclusive CDFA, 93.4% of cases were classified correctly, and classification success among regions ranged from 83.3 to 100%. The influence of freshwater discharge from 7 rivers along the Mississippi coastline likely made it possible to detect the relatively fine-scale spatial differences seen in this study, as defined by a mean interregional distance of only 25 km.

KEY WORDS: Otolith chemistry · Spotted seatrout · Gulf of Mexico · Juvenile