Sharpshooters

The archerfish is the sharpshooter of the seas. It lurks near the shore, in estuaries and mangrove forests. When it sees a tasty bug or even a small lizard on a low-hanging leaf or branch, it fires a powerful jet of water. The impact stuns the target and knocks it into the water, where it’s easy prey. Archerfish are found from India to Southeast Asia to Singapore and Australia. An average adult is less than a foot long.

They eat a varied diet, including smaller fish and other marine creatures. But sometimes, they take aim at targets above the water. A recent study found out how they do it.

German researchers trained several archerfish to hunt from a particular spot in a tank. They then used high-speed cameras to watch the action.

They found that a fish uses its tongue and the roof of its mouth to create a tube, like a gun barrel. It breaks the surface of the water with its mouth, then snaps its gills shut, firing out a jet of water.

The jet isn’t even, like the stream from a garden hose. Instead, the fish changes the shape of its mouth to vary the speed of the jet. The water that comes out last moves faster than the water that comes out first. As a result, the water balls up into a tight blob as it reaches the target — knocking the prey off its perch.

It’s a complicated process. The fish has to compensate for distance, the way light bends as it strikes the water, and the effect of gravity. That suggests that archerfish aren’t just deadly — they’re also smart.