FISH PREDATORS AND SCAVENGERS OF THE SEA-URCHIN ECHINOMETRA-MATHAEI IN KENYAN CORAL-REEF MARINE PARKS

Predation on 120 adult sea urchins of the species Echinometra mathaei was observed during daylight in shallow-water coral reefs (0.5 to 3 m deep) in a variety of sites in 3 Kenyan marine parks. The predators were few (8 species) and dominated by the triggerfish Balistapus undulatus (65% of all observations) followed by terminal-male wrasses Coris formosa, C. aygula and Cheilinus trilobatus, and lastly the scavenger Lethrinus mahsena. Those species that attempted, but failed, to prey on E. mathaei were slightly more numerous (11 species), while scavengers of opened carcasses were the most speciose (20 species). Based on these observations, it is suggested that B. undulatus is a 'keystone predator' and that fishery regulations that protect this species may be necessary in order to reduce the detrimental consequences of high sea urchin abundance - such as high reef substrate erosion and competitive exclusion of fishes.