Think Stats, 2nd Edition

Colophon

The animal on the cover of Think Stats, second edition is an archerfish, or spinner fish (Toxotidae). This family of fish preys on land-based insects and small animals, using their specialized mouths to shoot them down with water droplets. This family consists of seven species, which can be found from India to the Philippines, Australia, and Polynesia.

The archerfish has a deep body; the space between the dorsal fin and mouth forms a straight line. The protractile mouth has a lower jaw that juts out. The shape of its mouth lends itself directly to feeding: the narrow groove in the roof of its mouth allows it to squirt a jet of water at its victim by pressing its tongue against the groove and contracting its gills to force the powerful jet of water out, which can travel up to five meters. Archerfish learn how to shoot when they reach 2.5 cm long. Often they are innaccurate at first and hunt in small schools, eventually learning from experience.

The archerfish’s eyes are also valuable tools for feeding. It has particularly good eyesight and is able to compensate for light refraction as it passes through the air-water interface when aiming at prey. Once it spots its prey, the archerfish rotates its eye so the image of the prey falls on a particular portion of the eye. Often, the archerfish will leap out of the water to grab the insect in its mouth, if within reach.

Archerfish are usually small, at 5−10 cm, but can grow up to 40 cm long. Archerfish are popular aquarium fish. ...