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Coral reef census will help scientists protect fragile underwater habitats

Coral reef census
Marine-protected areas support a variety and abundance of reef fish in the Rock Islands of Palau, Micronesia.
(Tane Sinclair-Taylor)

Despite pressures from overfishing and changing ocean conditions, some coral reefs around the world manage to defy expectations.

In a survey of more than 2,500 reefs around the world, scientists identified 15 that were surprisingly healthy, considering their proximity to large human populations or unfavorable environmental conditions, according to a new report in Nature.

These so-called bright spots had far more fish than the researchers could reasonably expect, said Josh Cinner, a professor at James Cook University in Australia who studies how social sciences can improve coral reef management.

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A Titan villager navigates a traditional Melanesian outrigger over the coral reef surrounding the island of Mbuke in Papua New Guinea.
A Titan villager navigates a traditional Melanesian outrigger over the coral reef surrounding the island of Mbuke in Papua New Guinea.
(Tane Sinclair-Taylor)

Along with 15 bright spots, Cinner and his colleagues found 35 “dark spots,” areas with fewer fish than the researchers would have anticipated.

By examining what’s going right at these bright spots — and wrong at the dark spots — scientists hope to find new insights for confronting the numerous problems coral reefs face today.

“We wanted to know why these reefs could ‘punch above their weight,’ so to speak, and whether there are lessons we can learn about how to avoid the degradation often associated with overfishing,” Cinner, the study’s lead author, said in a statement.

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Researchers from James Cook University conduct reef fish biomass surveys in Kimbe Bay, New Britain, Papua New Guinea.
Researchers from James Cook University conduct reef fish biomass surveys in Kimbe Bay, New Britain, Papua New Guinea.
(Tane Sinclair-Taylor)

Coral reefs provide habitat and food for countless species. Many conservation efforts focus on relatively pristine areas under minimal threat. But as pressures from fishing and climate change mount, coral reefs in human-inhabited areas need protection too, the study argues.

Around the world, coral reefs are threatened by population growth, overfishing and destructive fishing practices such as dragging large nets across the ocean floor. On top of that, climate change threatens the reefs with increased coral bleaching and more severe cyclones.

The study found that reefs around wealthier countries tended to be in better condition. The findings also confirmed that marine reserves help sustain fish populations when their protections were enforced.

The study found input from local fishermen on managing reefs helps keep them healthy. Here, a man uses a handmade spear to hunt sleek unicornfish.
The study found input from local fishermen on managing reefs helps keep them healthy. Here, a man uses a handmade spear to hunt sleek unicornfish.
(Tane Sinclair-Taylor)

Surprisingly, the bright spots weren’t limited to places where people were scarce. They also included areas where humans make high use of their local reefs.

Typically found in the Pacific Ocean, these bright spots included reefs in the Solomon Islands, parts of Indonesia, Papua New Guinea and Kiribati. In these countries, people had strong cultural institutions attached to the reefs and were more engaged in management efforts.

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The bright spots also tended to have more favorable environmental conditions, such as more deep water where fish could take refuge from dangers.

The endangered humphead Maori wrasse has suffered dramatic population declines over the last few decades as a result of overfishing. This photo was captured in Palau, Micronesia.
The endangered humphead Maori wrasse has suffered dramatic population declines over the last few decades as a result of overfishing. This photo was captured in Palau, Micronesia.
(Tane Sinclair-Taylor)

The exact reasons bright spots have managed to fare better than other reefs in similar conditions still require more detailed investigation. However, the study authors suggested that allowing for property rights and increasing local participation in fisheries could spur more innovation in reef conservation.

If bright spots offer suggestions for how to improve coral reefs, dark spots may help identify practices to avoid.

Dark spots were found in every major ocean basin and even included some uninhabited areas thought to be near-pristine, such as the Northern Hawaiian Islands.

They tended to be places where people were better able to catch large amounts of fish. Dark spots also occurred in areas recently ravaged by cyclones or coral bleaching. 

The long-term viability of coral reefs ultimately depends on reducing carbon emissions, the study said. But overfishing still threatens a reef’s underlying ecological health — and curbing that will give reefs a chance to cope with environmental change.

Blackspotted rubberlips (Plectorhinchus gaterinus) form a dense school on a reef in the Western Indian Ocean.
Blackspotted rubberlips (Plectorhinchus gaterinus) form a dense school on a reef in the Western Indian Ocean.
(Tane Sinclair-Taylor)
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Photographs by Tane Sinclair-Taylor.

sean.greene@latimes.com

Follow me on Twitter seangreene89 and “like” Los Angeles Times Science on Facebook.

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