The Reel Downfall of Reefs Controlling Fishing to Save the Coral Reefs

Across the world coral reefs are dying because of over-fishing. It is the fish which protect the reefs from excessive algae, the main culprit in coral death. For over a millennium, inhabitants of small islands who depended on seafood for survival practiced conservation or starved. In the 20th century, however, improvements in fishing gear and increased seafood demand have led to a breakdown of the once sustainable system. A fifth of the reefs are now completely dead and most of the rest now support a fraction of the marine life they once did.

In the Caribbean, the predators were eliminated first, then the herbivores, until only the sea urchins were keeping the algae density down. When an epidemic wiped out most of the Caribbean’s urchins in 1983, the corals died, too. Now the region’s coral cover is estimated at only 13 percent, from 50 percent 30 years go, according to Alan Friedlander, a Hawaii-based marine ecologist.

Today, across the Pacific, people who depend on seafood for survival are beginning to buck the trend—placing limits on how much one can fish and setting aside no-take areas where the fish populations can reproduce in peace.

The trend began in Palau a few years ago as the Micronesian Challenge, a conservation initiative to ban or severely restrict fishing in 30 percent of coastal waters by 2020. Palau’s dependence on diving tourism has been a powerful motivator. The challenge was proposed by Palau president Tommy Remengesau, Jr., who was named a Time Magazine Hero of the Environment last year and is receiving major financing from the Nature Conservancy. The campaign—urging the nations of Palau and nearby islands to adopt this conservation initiative—has already spawned imitators in Asia and the Caribbean.


One of the most successful comebacks, according to Friedlander, has emerged in largely fished-out Hawaii. Moomomi Bay, a small fishing community of mostly indigenous Hawaiians, has achieved the spectacular result of two metric tons of fish biomass (total weight of all fish) per hectare for a 10-mile strip of coastline, while feeding 1,500 people. The locals use a very precise lunar calendar and ban fishing when fish aggregate to spawn. (To compare, Fiji’s present average biomass is 0.6 tons, the California kelp forest’s is 0.4 tons, and the Great Barrier Reef, which is commercially fished, has about 1.7 tons, says Friedlander.)

Hawaii, which boasts one of the highest densities of Marine Protected Areas in the world, with some dating back 40 years, was also the site of a landmark study last year that quantified just how many fish come back when a no-fishing marine protected area is created, and how fast. Incentives to help the fish return included creating big no-take reserves and limiting fishing in areas between them.


The reef conservation movement comes just in time, since global warming trends are bringing increasingly frequent spikes in tropical ocean temperatures, causing mass deaths of corals, the fish communities they support and the shorelines they protect from waves. At the same time, researchers are solving the biggest problem confronting marine scientists: the lack of baselines. A baseline, in the natural sciences, is an ecosystem that has not been affected by man before it could be studied. Only in the last half-century has marine science progressed beyond dissecting fish, and, by then, most of the marine ecosystems had been altered by over-fishing, invasive species or pollution.

Close examination of remote pristine islands—the most thoroughly studied of these is Kingman Reef, a U.S. possession 930 miles south of Hawaii—has revealed surprising findings. Comparing uninhabited and protected Kingman with populated Christmas Island 400 miles to the southeast, a team led by the Scripps Institute of Oceanography in La Jolla, California, found that the corals in Kingman were a model of health while those in Christmas were sickly and lacked growth. Searching for answers, they counted fish.

They found that Kingman has a biomass of a whopping 5.3 metric tons per hectare, of which 85 percent are sharks, jacks and other top predators. Christmas, where all the sharks have been fished out so their dried fins can be sold to the lucrative Chinese market, has a biomass of 1.3 tons. The amount of microbes in the water, including pathogenic viruses, was 10 times greater in Christmas than in Kingman.

While the total biomass of herbivores was not much different in both islands, Christmas was dominated by damselfish, which essentially farm the algae they eat, while Kingman was dominated by tangs, which eat much more algae. The researchers concluded that the greater amount of bacteria in Christmas stemmed from a greater amount of sugar in the water released by algae, and that these microbes ate coral eggs and sperm and attacked adult corals weakened by excessive algae. Thus, the presence of large numbers of sharks was linked for the first time to the health of the coral reefs.

“We found that the corals at Kingman were surviving hot-water periods very well and those at Christmas were not,” says Stuart Sandin of Scripps.

Today, most Pacific islanders are focused on bringing back the fish they can eat, like groupers, snappers and jacks, and the herbivores that will keep their reefs healthy. But as science progresses, the importance of bringing back the whole ecosystem, sharks and all, is going to come into focus.