Abstract

Natural biogeochemical tags of age-O red snapper, Lutjanus campechanus, nursery areas in the northern Gulf of Mexico were detennined based on sagittal otolith microchemistry. Age-O red snapper were collected in 1996 and 1997 from historically important nursery areas in north central, northwest and southwest areas of the United States' Gulf of Mexico. Otolith microchemistry of these fish was assayed using solution-based inductively coupled plasma-mass spectrometry (ICP-MS). In addition to Ca, four elements (Ba, Cd, Mg, Sr) were consistently detected in age-O red snapper otolith solutions above ICP-MS limits of detection. For statistical analyses, otolith concentrations of these elements were expressed as ratios to Ca. In 1996 and 1997 there were significant diferences in Ba:Ca, Cd:Ca, Mg:Ca, and Sr:Ca ratios between nursery areas. Multivariate analyses of variance, with all four element: Ca ratios as dependent variables, indicated that diferences in nursery-specific elemental signatures were statistically significant in 1996 and 1997, linear discriminant functions were computed from elemental data in each year as a tool to classify individual fish to their nursery areas of collection. In 1996, overall classification accuracy of age-O fish to nursery area was 93%, while 1997 age-O fish were correctly classified with an overall accuracy of 87%. Future research will focus on determining the otolith core microchemistry of adult red snapper from otTshore reefs in the northern Gulf of Mexico, and on determining the nursery areas from which adults recruited based on the microchemical tags developed from age-O red snapper otoliths.

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