Predator release of the gastropod Cyphoma gibbosum increases predation on gorgonian corals.

When large, predatory fishes and invertebrates were excluded from areas of a coral reef in the Florida Keys, USA, densities of the normally rare gastropod Cyphoma gibbosum, a principal predator of gorgonian corals, increased 19-fold. Gorgonians in predator exclosures were grazed more frequently and extensively by C. gibbosum than were gorgonians in uncaged areas. In exclosures, 14% of all gorgonians showed recent predation by C. gibbosum, with 62% of the entire colony surface being removed from these attacked individuals. In areas where predators of C. gibbosum were not excluded, only 5% of gorgonians exhibited recent damage, with only 26% of the colony surface being removed from these few damaged individuals. Thus, the increases in both frequency and extent of attack combined to produce an 8x increase in gorgonian damage following removal of large predators. These patterns suggest that predators typically suppress C. gibbosum populations, that overfishing of these predators could release C. gibbosum from top-down control, and that this release will allow increased damage to gorgonian corals.