Reef sharks are in trouble, FIU study says

Overfishing is pushing reef sharks toward the brink of extinction.

What's happening: Globally, the five main shark species that live on coral reefs — grey reef, blacktip reef, whitetip reef, nurse and Caribbean reef sharks — have declined by an average of 73%, according to a study co-led by researchers at Florida International University (FIU) and published June 15 in Science.

Why it matters: Depletion of marine ecosystems could threaten the livelihoods of millions of people worldwide who depend on them.

• "We are seeing that when sharks disappear, that causes other changes in these ecosystems," Mike Heithaus, an FIU dean and co-author of the study, said in a statement.

Context: The findings are part of a massive, multiyear project called Global FinPrint. Researchers set up underwater video equipment across 371 reefs in 58 nations and territories, and analyzed the footage.

• By 2020, the scientists found that sharks essentially disappeared from reefs in the Dominican Republic, French West Indies, Kenya, Vietnam, the Windward Dutch Antilles and Qatar.

What they're saying: "This tells us the problem for sharks on coral reefs is far worse and more widespread than anyone thought," Colin Simpfendorfer, lead study author and professor at Australia's James Cook University, said in a statement.

Yes, but: In some places, such as Australia, the Bahama, and the U.S., conservation strategies are working, researchers have noted.

• To help ecosystems, governments can implement shark fishing bans, establish no-take marine protected areas and set controls on trade.
• Reef shark populations can rebound in under a decade if such strategies are implemented, the study's authors wrote.

Between the lines: The authors noted that economics can affect overfishing.

• Sharks and rays are sometimes fished for subsistence and sold in local or export markets; other times, they are valued alive as tourism resources.