Fish will play a vital role in helping the Great Barrier Reef cope with the effects of climate change, a new study has found.
Scientists have warned that rising sea temperatures will have a disastrous effect on the future of the Great Barrier Reef, which currently supports a $5.1 billion per year tourism industry.
The reef suffered two mass coral bleaching events in 1998 and 2002.
And while most reef areas recovered with relatively low levels of coral death, some locations suffered severe damage, with up to 90 per cent of corals killed.
But although it is only a matter of time before the next coral bleaching event occurs, new research published today in the international journal Current Biology shows that healthy fish populations are essential to coral recovery.
Corals survive within a preferred range of environmental conditions, so if temperatures are too hot for too long the coral collapses and is replaced by weedy growth, a process known as a phase shift.
Researchers from the Centre of Excellence for Coral Reef Studies (CoECRS) have found that one way to prevent a phase shift is to have a population of fish ready to eat any weeds that may sprout before the corals have a chance to regenerate.
CoECRS researchers spent two and a half years tracking the recovery of corals in the Great Barrier Reef that were severely damaged by bleaching.
Team leader Professor Terry Hughes said the location was ideal because the fish populations were unusually intact due to the Marine Park Authority's no-take policy.
The no-take policy prohibits people from breaking off or taking pieces of coral.
Researchers fenced fish out of some areas so they could compare coral recovery in areas with and without fish.
Prof Hughes said the results were dramatic.
"The coral cover virtually doubled where the fish had access, while the fenced-off areas became overgrown with slimy weed and the corals failed to recover," Prof Hughes said.
Researchers found that herbivorous fish were particularly beneficial to the coral's recovery.
"The larger herbivorous fishes - such as parrot and sturgeon - are particularly important in keeping recovering corals free from weedy overgrowth," team member Professor Dave Bellwood said.
"Herbivorous fish are rarely caught by professional fishermen in Australia - though they are still hunted by spear fishers - but around the world they are under remorseless pressure.
"Over time, this could lead to the permanent loss of huge swathes of coral reef with serious consequences for communities which depend on them.
"This research indicates it is important to avoid overfishing of these herbivores at all costs."
Fellow author and research manager with the Great Barrier Reef Marine Park Authority, Dr Laurence McCook, said the research provided valuable information for the protection of the Great Barrier Reef.
Dr McCook said the study showed that no-take areas such as those applied on the Great Barrier Reef in the Green Zones made important contributions to the Reef's resilience.
"Maintaining resilience is a vital aspect of reef management," he said.
"A priority for the Great Barrier Reef Marine Park Authority is to build the Reef's resilience through initiatives such as no-take zoning and reducing water pollution."
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