Reefs Are So Damaged That Fish Have Begun to Use Each Other As Cover

Posted on Categories Discover Magazine

A predatory species of fish has adapted to the destruction of its local coral reef by using another fish, the peace-loving parrotfish, for cover, according to a new study.

Researchers and local divers in the Caribbean have long talked about the tactic and painted a similar picture: The long, thin trumpetfish swims alongside the more rounded parrotfish (or another reef fish) as if seeking cover from it. But does this really help the trumpetfish to hunt?

To find out, the researchers from the universities of Cambridge and Bristol staked out three locations off the coast of Curaçao in the Dutch Caribbean. At each, they ran a series of experiments on 36 different colonies of damselfish, a food source for trumpetfish.

Fishing Lines

The scientists set up a network of nylon lines and pulled hand-painted, 3D-printed models of the predator up to the damselfish, which swam up to inspect the new arrival. When the prey fish identified it as a threat, they darted to a sheltered place on the coral reef.

Next, the researchers trotted out a parrotfish model, which the damselfish didn’t investigate as frequently and didn’t register as a threat.

Finally, the team attached a trumpetfish model to a parrotfish one and slid both toward the damselfish. The tactic seemed to work: The damselfish responded as they had with the lone parrotfish model.

A trumpetfish model hides behind a parrotfish one. (Credit: Sam Matchette)

What Did the Study Show?

To carry out the study, the zoologists spent long hours in the water, attempting to remain motionless, but the data helped confirm the usefulness of a long-speculated-about behavior.

“I was surprised that the damselfish had such a profoundly different response to the different fish,” said Sam Matchette, a researcher in the University of Cambridge Department of Zoology, in a statement. “It was great to watch this happening in real time.”

According to local divers, the greater the damage in a particular area of the reef, the more the fish seem to use the move.

“We might see this behavior becoming more common in the future as fewer structures on the reef are available for them to hide behind,” said James Herbert-Read, an associate professor in the University of Cambridge’s Department of Zoology, in a statement.

The researchers have compared the trumpetfish tactic to the “stalking horse” one once used by human duck hunters, who held cardboard cutouts of innocuous animals in front of themselves. The hunters crept up on flocks of birds, which failed to realize the severity of the situation.

Read More: Do Fish Feel Pain?

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