Porcupine Fish, the common name of a family of fish. Porcupine fish are from about 10 inches to 3 feet (25 to 90 cm) long, and are covered with sharp spines. They can inflate themselves by drawing air or water into a sac in their bodies. Porcupine fish are found in nearly all tropical and some temperate waters. They feed mainly on shellfish, which they crush with their strong teeth. North American species include the porcupine fish (for which the family is named), the balloonfish, and the burrfish.