With A Lack Of Sharks, Fish Are Forgoing Defensive Gear

What happens when we overfish sharks? Fish appear to drop their guard.

Off Australia’s northwest coast, two neighboring coral reefs seem nearly identical. If you dove there, you’d find the same kinds of corals living in the same kind of water, with the same kinds of fish flitting through the polyps. But as you swam through the tropical waters, you’d begin to realize that something important is missing from one of the reefs. On Scott Reef, there are scarcely any sharks. From there, you may begin to look even more closely, and see the subtle signs that these two reefs are less similar than they first appeared.

For centuries, shark fishers from Indonesia have targeted Scott Reef. Next door, the Rowley Shoals have been protected as a marine reserve since the early 1990s. Now, in a new study, University of Miami marine ecologist Neil Hammerschlag and his colleagues have shown how the near depletion of sharks from Scott Reef has sent a cascade of subtle changes through the ecosystem—the signs of which are written on the bodies of the fish.

Photo: Albert kok/Wikimedia Commons (CC BY-SA 3.0)

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