DENSITY, SPECIES AND SIZE DISTRIBUTION OF GROUPERS (SERRANIDAE) IN 3 HABITATS AT ELBOW REEF, FLORIDA-KEYS

We examined the density, size and species distribution of groupers in three habitats on an inshore-to-offshore transect across Elbow Reef, F lorida Keys: high-relief spur-and-groove (4-9 m depth), relict spur-an d-groove (10-20 m), and deep fore reef slope (21-30 m). Physical relie f was greatest in the high-relief spur-and-groove (up to 3 m), lowest in the relict spur-and-groove habitat (<0.5-1 m), and intermediate in the deep fore reef slope habitat (1-1.5 m). Benthic coverage in the th ree habitats was dominated by algae (>30%). There were significant dif ferences in the density, size, and species distribution of groupers am ong the three habitats. Graysby, Epinephelus cruentatus, was numerical ly dominant, constituting 82-91% of individuals observed. Black groupe r, Mycteroperca bonaci, and Nassau grouper, E. striatus, were more abu ndant in high to moderate relief habitats, whereas red hind, E. guttat us, was more abundant in the low-relief habitat. The size distribution was shifted towards smaller sizes in lowest relief habitat and toward s larger sizes in areas with greater (>0.5 m) vertical relief. We sugg est that fishing pressure in the Florida Keys has resulted in an offsh ore grouper assemblage dominated by graysby, a small grouper species ( <40 cm total length) which is not targeted by fishermen, and that habi tat selection and biological interactions have significantly influence d the ecological structure of the grouper assemblage of this coral ree f.