Fishing ban guards coral reefs against predatory starfish...(the basis of results of an extensive mon...)

The initial zoning plan for the Great Barrier Reef Marine Park was fully implemented in 1989, with no-take zones covering 4.5 percent of the region. Subsequent surveys found that the relative frequency of outbreaks on reefs that were open to fishing was 3.75 times higher than on no-take reefs in the mid-shelf region, where most outbreaks occur.

"It had been suggested that exploited fishes eat the juvenile starfish, but there are only one or two anecdotal observations," Sweatman said. "I did not expect to find this pattern at all."

He remains skeptical that exploited fish species are significant predators of starfish, but said there might be a "trophic cascade" where increased numbers of exploited fishes, many of which are carnivores, cause a decline in small predatory fishes that favors larger invertebrates. He speculates that those invertebrates may prey on the starfish when they are very small.

The Great Barrier Reef Marine Park was re-zoned in mid-2004, increasing the no-take zones from 4.5 percent to 33 percent of the area of the park, a move that Sweatman's group reported in the June 23rd Current Biology has led to a rapid comeback of coral trout in the area.

" Whatever the underlying mechanism, this study suggests that this increase should reduce the overall impact of future waves of A. planci outbreaks," he said. "That effect may be amplified if fewer reefs with starfish outbreaks mean less effective propagation of outbreaks from reef to reef."

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