stop overfishing and the fish increase – no kidding?
A controversial decision to halt commercial and recreational fishing across vast areas of the Great Barrier Reef has proven remarkably effective for reviving coral trout numbers.
“Everyone is a little surprised,” admits Garry Russ, a marine biologist at James Cook University in Townsville.
“We’ve seen a consistent pattern of recovery of coral trout from just north of Cairns to as far south as Heron Island,” he says. “It’s an extraordinarily large area.”
In mid 2004, the Australian government rezoned the Great Barrier Reef Marine Park to create the world’s largest network of marine “no-take” zones.
Fishing was totally banned across a third of the park – more that 100,000 km2 – including parts of 70 biologically distinct “bioregions”.
At the time, surveys found that the majority of Australians wanted protection for the reef, but the move was also highly controversial among both commercial and recreational fishers who primarily target coral trout.
Surveys carried out by Russ’s team now show that coral trout numbers have increased by over 60% in no-take areas around two groups of inshore islands – Palm Island and the Whitsundays – 18 months to two years after rezoning.
By contrast, Coral trout numbers in nearby fished areas did not change. “In the long term, the hope is that as numbers build up in protected areas, more fish will spawn successfully, enhancing numbers in fished areas,” says Russ.
A second team led by Hugh Sweatman of the Australian Institute of Marine Science in Townsville, has also found that coral trout numbers had increased significantly in no-take zones around reefs from 32 to 200 kilometres off-shore.
In four of these offshore regions, numbers of coral trout were between 31 and 64% higher compared to unprotected regions nearby, just two years after the zoning took place.
The consistency of the results, combined with the finding that in-shore coral trout numbers did not decrease, suggests that the differences are indeed due to decreased fishing in the off-shore no-take zones, rather than increased fishing elsewhere, says Russ.
“It’s a very positive start, but full recovery of coral trout will take 10 to 15 years of really effective protection,” says Russ. The two teams are monitoring 160 different species of fish, but so far only numbers of coral trout have changed since the rezoning.