FISHING restrictions are turning out to be the unexpected saviour of a coral reef in the Bahamas that was being overrun by algae and seaweed. Concerns had been raised that limiting fishing in the Exuma Cays Land and Sea Park would have the opposite effect, by allowing predator fish species to thrive and so wipe out fish that 鈥済raze鈥� the coral and keep it free of damaging algae which covers the coral surface, stopping coral larvae from settling and growing.
But predators such as the Nassau grouper, Epinephelus striatus, appear to spare larger grazers, and these survivors clear the reef far more efficiently than their smaller brethren. 鈥淲e were surprised to find the larger parrotfish escaped predation,鈥� says Peter Mumby of the University of Exeter, UK. Parrotfish grow up to 30 centimetres, and those over 25 centimetres long 鈥渨ere simply too big to swallow鈥�, he says. Fishing restrictions may also be helping by preventing the capture of parrotfish.
With the restrictions in place, groupers were seven times as plentiful in Exuma Cays as in three other Bahamas reefs where fishing is unrestricted, and the amount of grazing has doubled (Science, vol 311, p 98). As a result, algae and seaweed that stifle coral growth have been reduced fourfold.
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The reefs deteriorated in the early 1980s after a mystery disease wiped out urchins that previously kept the coral in good health.
