Hawaii's Reef Fishes

Boxfishes (Ostraciidae)

Whitley's Trunkfish (male) Ostracion whitleyi (Fowler, 1931)

The trunkfishes, also popularly known as boxfishes, are unique in possessing a bony carapace of polygonal plates with gaps for the mouth, gill opening, caudal peduncle, and fins. The carapace may be triangular, quadrangular, pentagonal, hexagonal, or nearly round in cross-section; its surface is usually rough due to small tubercles on the plates.

Some of the species have stout spines which project from the carapace. The mouth is small and low on the head; the gill opening is a short near-vertical slit. There are no spines in the fins; the dorsal and anal fins are posterior in position, usually with 9 rays; there are no pelvic fins.

As would be expected from their bony armor and boxy shape, trunkfishes are slow swimmers; the usual progression is by a sculling action of the dorsal and anal fins; the caudal fin is brought into play when the fishes want to move faster.

They feed on a wide variety of benthic animals, especially sessile forms such as tunicates and sponges; many also ingest large amounts of algae. Some trunkfishes, at least, secrete a skin toxin when under stress.

Six species are recorded from the Hawaiian Islands; one of these occurs only in deep water. Another, Ostracion cubicus, is known from Hawaii from only one specimen and one sighting.

Spotted Boxfish

All information and pictures in this section are from John E. Randall's Shore Fishes of Hawai'i by permission of the author.