Comparative demography of mushroom corals (Scleractinia: Fungiidae) at Eilat, northern Red Sea

Abstract.

The population structure and growth rates of stony corals may provide important information concerning their processes of turnover and recovery on coral reefs, yet for most corals such information is lacking. We quantify here the population dynamics of solitary free-living mushroom corals on a fringing reef at Eilat, northern Red Sea. Population models were applied to estimate growth, mortality, and lifespan in members of four common taxa: Ctenactis echinata, Fungia scutaria, F. fungites, and the subgenus F. (Danafungia) spp. Individuals of C. echinata and F. scutaria grew allometrically: their oral disc length increased more rapidly than width, leading to an oval body shape. Individuals of F. fungites and F. (Danafungia) spp. grew isometrically, retaining a circular body shape. A population of F. scutaria on the intertidal reef flat was characterized by young individuals (mean age=2 years), with high mortality and short lifespan (13 years). In contrast, populations of the other three mushroom coral taxa on the reef slope consisted of older individuals (mean age=4–9 years), with lower mortality and longer lifespans (24–46 years). Demographic patterns appeared to vary with species characteristics, and possibly with the level of disturbance in each reef habitat. Minimum sizes at which these mushroom corals may be removed sustainably from the populations range from 7 to 22 cm polyp diameter (5–14 years of age). We conclude that the Beverton and Holt population dynamic model is applicable to the management of stony corals with solitary or compact, upright growth forms that rarely fragment.