Interspecific variation in juvenile snapper otolith chemical signatures in the northern Gulf of Mexico

The objective of this study was to evaluate whether age-0 lane snapper Lutjanus synagris otolith chemical signatures could serve as accurate proxies for those of its congener, red snapper L. campechanus, among northern Gulf of Mexico (GOM) nursery regions. Red (n = 90) and lane (n = 53) snappers were sampled from 3 regions of the northern GOM in fall 2005, and their otolith chemistry was analyzed with sector field-inductively coupled plasma-mass spectrometry (Ba:Ca, Mg:Ca, Mn:Ca, Sr:Ca, Li:Ca) or stable isotope ratio-mass spectrometry (delta C-13 and delta O-18). Chemical signatures were significantly different among regions (MANOVA, p < 0.001) and between species (MANOVA, p = 0.029), with the species effect being driven by significant differences in 4 of the 7 constituents analyzed (ANOVA, p < 0.036). The significant region effect persisted (MANOVA, p < 0.001), but the species effect was non-significant (MANOVA, p = 0.964) when constituent values were normalized to species-specific means. Mean regional classification accuracies from linear discriminant functions computed with otolith constituent data were 84% for lane snapper and 80% for red snapper whether data were normalized or not. Maximum likelihood models parameterized with normalized lane snapper otolith chemistry data estimated red snapper regional composition reasonably well among mixed-region samples (mean error = 9.7% among models). Therefore, it appears age-0 lane snapper otolith chemical signatures can serve as accurate proxies for those of red snapper in the northern GOM. These results have broader implications for deriving natural tags based on otolith chemistry for fishes that may have low abundance in parts of their range.