New Study Finds Sharks in Tropical Coral Reefs Are Disappearing Due to Human Activity
June 19, 2018
ARLINGTON, Va. (June 19, 2018) – A new study published today in the Proceedings of the National Academy of Sciences (PNAS) found that sharks populations are disappearing in waters where humans are fishing — even in marine protected areas.
The study, conducted by Conservation International Senior Director, Global Fisheries and Aquaculture Program Jack Kittinger, Ph.D. and 36 scientists, assessed about 1,800 tropical coral reefs and found that sharks and other reef predators, such as large snappers, were present in just 28 percent of the scientists’ observations. Also, they were hardly seen at all at reefs where human pressure, through fishing or pollution, was high.
The research provides vital evidence on the most effective ways to protect fish populations, especially sharks. The study showed that the number of top predators in large remote marine reserves in areas with very low human pressures is much higher — more than quadruple the numbers found in remote lightly fished unprotected areas.
“Coral reefs are in a trade war and the conservationists’ solution of choice is Marine Protected Areas,” said Kittinger. “This research tells us that the closer a reef is to a major market, the more we have to temper our expectations about conservation gains, and the more important remote protected areas become for populations of top predators.”
Researchers used a new way of measuring the human pressures, such as fishing and pollution, to study the effects these are having on fish on the world’s reefs. The ‘human gravity’ scale calculates factors such as human population size, distance to reefs, and the transport infrastructure on land — which can determine reefs’ accessibility to fishermen and markets.
Where human pressure was high, the probability of encountering a top predator dropped to almost zero (less than 0.005). This scarcity is regardless of whether there are protections in place, such as ‘no-take’ marine reserves or restrictions on fishing equipment.
Research failed to pinpoint why sharks do better in remote reserves, however, the market value of fins expose sharks to fishing. In addition, scientists believe the size of reserves in heavily fished areas are likely to be too small to protect sharks as they have large hunting ranges that likely expose them to fishing when they stray outside reserves.
The study also reveals that people are profoundly degrading communities of fish on coral reefs. Marine reserves located in remote areas with little human pressure have more than four times as many fish compared to reserves near highly fished areas.
Although those reserves within areas of high human pressure are relatively depleted, the research shows that they play a vital conservation role, containing around five times as many fish as openly fished areas under similar human pressure.
About Conservation International
Conservation International uses science, policy and partnerships to protect the nature that people rely on for food, fresh water and livelihoods. Founded in 1987, Conservation International works in more than 30 countries on six continents to ensure a healthy, prosperous planet that supports us all. Learn more about Conservation International, the groundbreaking “Nature Is Speaking” campaign and its series of virtual reality projects: “My Africa”, “Under the Canopy” and “Valen’s Reef.” Follow Conservation International’s work on our Human Nature blog, Facebook, Twitter, Instagram, and YouTube.