Predator Allows Coral Reef Rebound

Parrotfish, such as this one from the Great Barrier Reef, play critical roles as gardeners in marine protected areas, maintaining the balance between corals and seaweeds that would otherwise overgrow them. [Image © Science]

The return of a top predator to a protected marine reserve in the Bahamas has unexpectedly led to a revival of the reserve’s coral reefs as well, according to a new study published in the 06 January 2006 issue of the journal Science.

The tale of the Nassau grouper, its parrotfish prey and parrotfish grazing habits among the coral shows how reserves may benefit ocean habitats in surprising ways, according to Peter Mumby and colleagues. Parrotfish are the top grazers in Bahamian coral reefs, “cleaning” the reefs and prompting their growth by nibbling on the algae that attach to the coral.

The Nassau grouper, on the other hand, makes its meals out of parrotfish. So it might seem that a no-fishing zone that increases the number of groupers would be bad news for the reef. Instead, the researchers found that the return of the groupers led to a shift in parrotfish size among the reefs, toward larger and faster parrotfish that can escape the grouper's jaws.

The bigger parrotfish are also more efficient reef grazers, which keeps the reefs clean and flourishing. In a related “Perspective” article, Ove Hoegh-Guldberg says the study is the kind of research needed to convince government and other agencies that marine reserves are valuable conservation tools.

6 January 2006