Production of new colonies by fragmentation of established colonies is shown to be an extremely important mode of reproduction and local distribution anlong major reef-bu~lding corals. This type of reproduction avoids the high mortality rates of larvae and juveniles and spreads the risk of mortality for the genotype Fragmentation by corals wlth high growth rates results In their domination of certain reef zones, rapid growth of reefs on which these corals are abundant, and rapid recovery from disturbances. I conclude that a number of the most successful corals are adapted to fragment, 1.e have incorporated fragmentation into their life histories

X-radiographic techniques were used to measure growth rates and bioerosional damage in 3 massive coral species collected at Carrie Bow Cay. Belize. Montastrea annularisgrew significantly faster (F = 6.34 mm p-') than Porites astreoides (E = 4.75mm p-') and both grew significantly faster than M. cavernosa (2 = 4.36mm p-'). M. annularis (when combined with data from Weber and White. 1977) and M. cavernosa growth rates were inversely correlated with water depth. M. annularis skeletons were significantly more excavated (?=?.g% of cross-sectional area) than M. cavemosa (F = 5.3 % ) or P. astreoides (x = 4.8 %) skeletons. Over 80 % of skeletal excavation occurred within 2 cm of a dead surface in all 3 species. Bioerosion within this 'dead area' was significantly greater in M. annularis (F = 15.3 % of cross-sectional area) than in M. cavernosa (F = 12.1 %) or P. astreoides (? = 8.0%), and significantly greater in M, cavernosa than in P. astreoides. Boring sponges accounted for 85 to 94 % of skeletal excavation, with polychaetes, bivalves, and sipunculans accounting for the balance. Differences in percentage excavation correspond to differences in skeletal density (dense species are more bored), proportion of dead skeletal surface available for recruitment by boring organisms (although anomalous results were obtained for P. astreoides because of an encrusting sponge associate), and possibly to differences in plankton primary productivity.