Click here to watch a video of the archerfish in action.
As their name implies, archerfish exhibit a remarkable strategy for hunting food, using their mouths as a bow to spit out a jet of water like an arrow.
The fish aims the jet at objects that move or glow, and is able to knock insects off overhanging branches down into the water for consumption.
Not only do archerfish have good eyesight, but also the ability to compensate for light refraction as visual information crosses the air-water boundary. Their retinas show differentiation of photoreceptor cells that correlate with differences in aquatic and aerial fields of view.
Their mean spitting angle is approximately 74 degrees from the horizontal, but can be accurately adjusted between 45 and 110 degrees depending on the victim’s location.
To focus on its prey, the fish rotates its eye, allowing a “spitting image” of the prey to fall into the target zone on the retina.
It then positions its lips just above the surface, closes its gill covers, and presses its tongue against a narrow groove in the roof of its mouth, sending a stream of water up to five meters high, depending on its size.
This jet can be varied according to the size and location of the prey. Fish begin shooting before they are fully grown, but have to learn from experience during which time they hunt in groups, perhaps to increase the chance of hitting a target.
Archerfish typically stay near the water surface and can even jump out of the water to catch nearby prey in their mouths.
Click here to watch a video of the archerfish in action.
Matthew Oldfield is a freelance photographer based in Bali, Indonesia, specializing in editorial and documentary images from both above and below the waves. He works primarily with charities, NGO’s, and other organizations working to conserve the environment, endangered species, and disappearing cultures.
