The scientists found that coral trout numbers were significantly higher in no-take reserves than in sites that remained open to fishing.
Researchers say the increase is probably due to decreased fish mortality inside the new reserves, rather than increased fishing outside.
"Although preliminary, our results provide an encouraging message that bold political steps to protect biodiversity can produce rapid, positive results for exploited species at ecosystem scales," Russ said.
Enric Sala, a marine biologist at the Scripps Institution of Oceanography at the University of California in San Diego, said it's intuitive that a fishing ban would help fish survive.
"This rebound is great news, but it is not 'new' news," he said. "When you truly protect a species from fishing or create a no-take marine reserve, large fishes come back."
Sala notes that Florida jewfish and Mediterranean dusky grouper rebounded under similar conditions.
Study co-author Hugh Sweatman, a reef ecologist at the Australian Institute of Marine Science, agrees.
"My 10-year-old son saw the graphs and said, If you stop fishing, don't you expect to find more fish? And he is right," Sweatman said.
He noted that while individual reserves have resulted in quick increases of target species before, "what is new about our study is the rapid, fairly consistent effect in multiple reserves over a huge area."
The ecologist says the Great Barrier Reef fishing ban has offered a rare chance to test whether the largely theoretical idea of marine reserve networks actually works, adding that many questions remain.
Among them: the long-term effects of no-take reserves on coral trout populations, as well as other species on the Great Barrier Reef food chain.
Russ, the lead study author, is currently investigating whether juvenile coral trout from protected areas will migrate to help repopulate stocks in less-protected areas over time.
Sweatman says the bold strategy to protect coral trout in Australia would be hard to replicate elsewhere.
The Great Barrier Reef is "a large area with a small and relatively rich coastal human population that is not depending on the reefs for the next meal," he said.
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