Astonishing Accuracy of the Archerfish

In India and that area, extending into Southeast Asia and Northern Australia, is a genus of ten species called archerfish. Quite a range for a small group. Most are about the size of an adult human's hand, but one doubles that. What is interesting about them is how they get food.

When people swim, they often play by getting a mouthful of water, compressing, and squirting out a stream for a few seconds. Not very powerful or accurate. The archerfish does something similar, but with great force and accuracy.

Archerfish, Flickr / Feline Groovy (CC BY-ND 2.0)

There are many factors in play, including principles of sciences, that make this water jet ability even more amazing. Consider how it sees its perching insect target and accurately blasts it into the water — and has calculated where lunch will land, so it is there before it escapes. Speaking of jet, biomimetics gets involved, as people are studying the archerfish for (wait for it) inkjet printing. Once again, we see the brilliance of the Creator at work. We could also consider the possibility that all this is an example of his sense of humor in thwarting naturalists.

The mature archer fish normally hits its target the first time. Yet it spots the prey from underwater, which has the problem of light refracting (bending) at the water-air interface. At a typical shooting angle of 74° from the horizontal, the refraction causes the archer fish to see it at 78°. It can shoot at shallower angles up to 45°, where the deviation is even greater—58°. The archer fish must compensate for this difference. It must also compensate for the fact that the jet will not travel in a straight line, but will curve downwards due to gravity, forming a parabolic path.

You can read it all at "Archer fish use advanced hydrodynamics."