Marine biologists researching in the Caribbean have found that a commercial fishing ban led to healthier coral reefs.

The study, led by Peter Mumby of Devon’s Exeter University, concentrated on a marine park in the Bahamas. It found that, following a ban on commercial fishing, the return of top predators – sharks and, in particular, the Nassau grouper – helped corals to grow more efficiently.

The findings contained a surprising twist. Higher numbers of the top predators meant that more parrotfish were eaten – and, as parrotfish nibble away and clear reefs of coral-inhibiting weed, one might expect this to have been bad news.

But it transpired that the consumption of some parrotfish allowed other parrotfish to grow larger. Once they reached a length of about 30cm, they became immune to being swallowed by predators, while their size also meant a bigger appetite.

The overall result was more, not less weed removed from the reefs. Nature’s balancing of species is indeed a complex business!

The Exeter team’s study report has been published by Science, the magazine of the American Association for the Advancement of Science (AAAS).

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