Recovery of a coral reef keystone predator, Balistapus undulatus, in East African marine parks

Abstract

The red-lined triggerfish ( Balistapus undulatus) is a major predator of sea urchins and the loss of this species, along with other less influential sea urchin predators, has resulted in the proliferation of sea urchin populations on the coral reefs of East Africa. I studied the recovery of B. undulatus and the associated demise in their sea urchin prey in five Marine Protected Areas (MPAs) which differed in their age, such that the data collected spanned a 30-year range in the age of protection. Results suggest that predation on sea urchins and B. undulatus dominance recovered on a time scale of 5–10 years, but sea urchin populations were not reduced below 1000 kg/ha for more than 10 years, and B. undulatus populations may require > 30 years to recover. In a new MPA, B. undulatus competitively excluded a subordinate wrasse predator, Cheilinus trilobatus, at baited sites in < 8 years. A second triggerfish, Balistoides viridescens, was the competitive dominant to B. undulatus in direct interference interactions, but B. viridescens was not found in 2.7 ha of sampling and rarely seen eating sea urchins at baited sites. An even longer estimate of top predator recovery would occur if B. viridescens is the dominant sea urchin predator. This study suggests that short and temporary closures of <10 years will not fully restore reef ecology, and that fully protected and permanent MPAs are a necessary part of coral reef conservation programs.