Many marine fishes use the mangrove ecosystem for foraging, protection, spawning and as a nursery habitat To develop a better understanding of energy flow between the local mangrove and coral reef ecosystems, the ontogentic migration and trophic connectivity of reef fishes were examined through the use of stable isotope ratios Juvenile and adult reef fishes, including species such as, the grey snapper Lutjanus griseus, bluestriped grunt Haemulon sciurus, yellowfin mojarra Gerres cinereus, and great barracuda Sphyraena barracuda, were collected both from mangrove a coral reef sites located near Port Everglades, Broward County, Florida All species were analyzed using δ 13C and δ 15N from muscle tissues and δ 18O and δ 13C from otoliths to evaluate ontogenetic migrations, foraging, and occupation within both the mangrove and reef sites Preliminary δ18O and δ13C otolith data indicate mangroves to be more depleted than offshore reef habitats, indicating that juvenile fish are utilizing the mangroves The δ13C and δ15N in muscle tissue is more depleted in juvenile fish caught from the mangroves than fish adult fish caught on the reef This study will help clarify the relative importance of the various habitats essential for early life-history stages of reef fishes.