The expansion of no-take marine reserves (NTMRs) within Australia's Great Barrier Reef Marine Park more than a decade ago is working to protect fish just as experts had hoped it would, say researchers who have been monitoring the reef via underwater surveys. The findings, reported in the Cell Press journal Current Biology on March 26, come as encouraging news for Australia's largest reef and for other, similar projects around the world.
While the park reserves could not protect the reef directly from extensive physical damage caused by Tropical Cyclone Hamish in 2009, researchers say that the reserves surely have helped in the reef's recovery.
"The sheer size of the Great Barrier Reef Marine Park ensured there were adequate areas unaffected by the cyclone that should serve as larval sources of fishes and coral to aid recovery in affected areas," says Michael Emslie of the Australian Institute of Marine Science.
The Great Barrier Reef Marine Park includes a large-scale network of NTMRs that extends over 2,000 kilometers along the northeast coast of Australia, Emslie and his colleagues explain. In 2004, the no-take reserves, which made up less than five percent of the park, were expanded to cover more than one-third of the area.
In the new study, researchers from the Australian Institute of Marine Science and the Centre for Excellence for Coral Reef Studies at James Cook University relied on data collected by underwater surveys over two time periods (2004 to 2012 and 1983 to 2012) from reefs spread over approximately 150,000 km2 of the Great Barrier Reef Marine Park. They investigated effects on fish numbers and sizes, species diversity, and the impact of disturbance from the severe tropical cyclone.
The numbers and size of coral trout, the most commercially important fishery species in the area, were consistently greater in NTMRs than on fished reefs over both the short and medium terms. At the same time, there was no evidence that the expansion of NTMR area within the marine park had hurt coral trout stocks on adjacent fished reefs, as fishers had to concentrate their effort on the remaining open reefs.
The work to monitor the health of the Great Barrier Reef continues as part of the Australian Institute of Marine Science's Long Term Monitoring Program. But it is important to recognize that no-take reserves alone will not be enough to keep the reefs safe.
"That the devastating effects of a severe tropical cyclone affected both NTMR and fished reefs equally is a timely reminder that NTMRs are not, by themselves, the solution for the full range of threats currently afflicting coral reefs," says David Williamson of James Cook University. "Pollution, sedimentation, coastal development, and the escalating effects of climate change all act at regional and global scales. The establishment of highly connected networks of NTMRs can contribute to a secure future for coral reefs, but effective measures to reduce land-based threats and to mitigate climate change will also be essential."
Current Biology, Emslie et al.: "Expectations and outcomes of reserve network performance following re-zoning of the Great Barrier Reef Marine Park."
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