Temporal and Spatial Variability in Juvenile Red Snapper Otolith Elemental Signatures in the Northern Gulf of Mexico

Abstract.-We examined otolith chemistry of age-0 red snapper Lutjanus campechanus in U.S. waters of the northern Gulf of Mexico (GOM) to determine if otolith elemental signatures could be employed as natural tags to estimate postsettlement population connectivity. Fish (n ¼ 755) belonging to five successive yearclasses (1996)(1997)(1998)(1999)(2000) were sampled from three GOM regions. Solution-based analysis of otolith chemistry was accomplished with sector field-inductively coupled plasma-mass spectrometry (Ba, Mg, Mn, and Sr) and inductively coupled plasma-optical emissions spectrometry (Ca). Several regional trends observed for individual elements were consistent among year-classes, yet elemental signatures were significantly different among years as well as among regions (multivariate analysis of variance [MANOVA]; p , 0.001). Jackknifed classification accuracies from linear discriminant function analysis approached 80% (mean ¼ 78.4%) in all years except 1998 (62.4%). Overall, these results indicate otolith elemental signatures may serve as effective region-specific natural tags of GOM red snapper. Significant differences in otolith chemistry among yearclasses indicates year-class-specific analysis is required to derive natural tags. Furthermore, regional differences in elemental signatures may be insufficient in some years to be employed as accurate natural tags