Discrimination of French grunts (Haemulon flavolineatum, Desmarest, 1823) from mangrove and coral reef habitats using otolith microchemistry

Using French Grunts (Haemulon flavolineatum) held captive within mangrove and reef sites, we determined (a) whether otolith microchemical differences existed between mangroves and reefs separated at a biologically relevant spatial scale (0.25–7.1 km), (b) whether patterns in elemental concentrations were consistent across years, and (c) whether it was possible to identify whether a given fish occupied a mangrove as a juvenile. Three sites were established at Great Exuma, Bahamas (two reefs and one mangrove, May 2001) and at Turneffe Atoll, Belize (one reef and two mangroves, August 2001 and 2002). Using concentrations of Sr and Ba, discriminant function analysis (DFA) indicated unique spatial microchemical signatures of fish from each of the three Bahamas sites allowing an average correct classification of 77%. Using concentrations of Sr, Ba, Sn and Pb (2001), and in addition Li, Mg, Cu and Rb (2002), DFA of the three Belize sites indicated an average correct classification of 68% and 85% in 2001 and 2002, respectively. To assess temporal variability in otolith microchemistry, we compared microchemical signatures of Belize fish from 2001 to those from 2002. On average, 42% of fish from 2002 were correctly classified to their captive sites using chemical information from 2001, thus suggesting considerable temporal variability in otolith microchemistry. Finally, to identify whether a given fish occupied a mangrove during its juvenile stage, we ablated the juvenile portion of the otolith taken from reefs in Belize 2002. Results of this analysis indicated that 36% of 39 individuals taken from the reef had a signature more representative of one of the mangrove sites. Although otolith microchemistry varied temporally and our analysis was restricted to the grouping of individuals to only one of three sites, mangroves appeared to contribute to reef populations.