Thornback Cowfish

Description

Like other members of the family Ostraciidae, the thornback cowfish has hexagonal, plate-like scales which are fused together to form a solid, box-like carapace, from which the eyes, mouth, fins and tail protrude. The mouth is small and has protruding lips, the upper profile of the snout is straight, the back is somewhat convex, the flanks are concave and the belly rounded, causing the fish to resemble a purse. There are small pre-ocular spines on either side of the head, a large spine projects from the dorsal ridge and a further moderate-sized spine projects from each of the pelvic ridges near the anal fin. Neither the dorsal fin nor the anal fin has any spines but both have nine soft rays, while the caudal fin is fan-shaped and has ten rays. A typical length for this fish is 15 cm (6 in). It can grow to 23 cm (9.1 in) in length.

The colour is variable, and changes to match the fish's surroundings; generally pale tan with spots or wiggly markings in yellow, mauve or blue. In some regions, this fish is toxic.

Distribution

Its range extends from the east coast of Africa between Tanzania and South Africa and the island of Madagascar, to Japan, Indonesia, Australia, Hawaii and Rapa Island.

Habitat

It occurs in areas of sand, rubble, corals and algae both in lagoons and on the seaward side of reefs. It can be found as deep as 132 m (433 ft) but a more normal depth range is between about 6 and 30 m (20 and 100 ft).

Ecology

This fish is usually solitary but the males are territorial in the breeding season. The diet consists of small invertebrates, which are exposed by jets of water from the mouth blowing away sand, and picked up by suction from the sea bed. It is an uncommon species.