September 8, 2014 / 7:18 PM / 5 years ago

Something's fishy: trout and eels cooperate in underwater hunt

WASHINGTON (Reuters) - If you want to witness effective teamwork, you might be as apt to find it among the fishy denizens of a coral reef as in the office where you work.

A spotted moray eel swims in front of children looking at an aquarium at a mall in Kiev April 28, 2013. REUTERS/Gleb Garanich

Scientists on Monday described how a colorful fish called the coral trout recruits moray eels to help hunt for prey, with both ending up well fed. Aquarium experiments showed that the trout are choosy in picking the best eel partner for the job.

The researchers noted that the trout performed as well as chimpanzees in a 2006 study that demonstrated how these close cousins of humans assisted one another in a food-gathering task.

The coral trout uses communicative body gestures including head shakes and headstands to enlist eels as hunting partners.

It’s an underwater dream team, with the trout possessing the speed to chase down a fish out in the open and the serpentine moray eel boasting a sinuous body enabling it to get at any fleeing prey that hides in a hard-to-reach coral crevice. They join forces on Australia’s Great Barrier Reef.

Some moray eels in the wild are more helpful than others. In the controlled environment of aquarium experiments, moray eel models were employed to test how well wild coral trout caught for the study could discern a good collaborator from a bad one.

One model was designed to come to the coral trout’s aid and flush out prey. The other eel model simply went the opposite direction.

The trout quickly learned which eel model was the better partner and recruited the good collaborator three times more often, the study found.

“This shows that a big mammalian brain is not necessarily required to undertake these sophisticated forms of communication,” said Alexander Vail, a marine biologist and zoologist at Britain’s University of Cambridge who led the study published in the journal Current Biology.

“Although the brains of mammals are certainly larger than those of fish, size may not be all that matters, and we are still a long way from a thorough understanding of fish brains and the mental computation they may capable of,” Vail added.

Coral trout are torpedo-shaped and about 21 inches (50 cm) long. Their body colors range from olive green to deep red and they are covered in small bright blue spots.

The eel benefits by being able to eat the fish chased into reef crevices by the trout. The trout benefits by being able to eat those fish the eel fails to catch.

“Each of these large predators is out for itself in their collaborative relationship, but they both do far better by working together and using communication to coordinate the hunt,” Vail added. “Both predators capture roughly the same number of prey items when hunting together.”

Researchers have noted similar collaboration with eels by another fish, the roving coral grouper. Vail said similar skills probably exist in other animals as well.

Reporting by Will Dunham; Editing by David Gregorio

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