Tim McClanahan Publishes 'Belize Protected Area Boosting Predatory Fish Populations but Herbivorous Fish Needed for Reef Recovery Still Lagging' (Pew Marine Fellow, 1996)

A 14-year study by Tim McClanahan of the Wildlife Conservation Society (WCS) and colleagues in an atoll reef lagoon in Glover's Reef, Belize has found that fishing closures there produce encouraging increases in populations of predatory fish species. However, such closures have resulted in only minimal increases in herbivorous fish, which feed on the algae that smother corals and inhibit reef recovery. The study appears in an online version of Aquatic Conservation: Marine and Freshwater Ecosystems. Specifically, the fishing closures have resulted in the recovery of species such as barracuda, groupers, snappers, and other predatory fish. Herbivorous fish such as parrotfish and surgeonfish, however, managed only slight recoveries, along with a small amount of the herbivory needed to reduce erect algae and promote the growth of more hard corals. This modest recovery of herbivorous fish has not been sufficient in reversing the degradation of the reefs by algae that have overgrown the reef and replaced the coral that once occupied 75 percent, but now represent less than 20 percent, of the seafloor cover. The authors note that a recent national-level ban by the Belizean government on the fishing of parrotfish—a widespread herbivorous species—may be the key to reef recovery, provided that the fishing ban is enforced and met with compliance. “The fishing ban in the fully protected portion of the lagoon was expected to result in an increase in predatory fish and—more importantly—herbivorous fish such as parrotfish that in turn reverse the degraded condition of algal dominance in this reef,” said McClanahan. “What happened was a recovery of predatory fish, but not of the herbivorous fish, a finding that is forcing us to come up with a more effective model of reef management and recovery. If the nation-wide ban on parrotfish is successful, then we can see if this type of large-scale management is the only effective solution for protecting coral reefs.”

Read the full study, Testing for Top-Down Control: Can Post-Disturbance Fisheries Closures Reverse Algal Dominance? visit the Wiley Library website.