Latin name

Trichiurus lepturus

Other names

Beltfish, Atlantic cutlassfish, Pacific cutlassfish, Japanese cutlassfish.

Identification

The body is elongated, bare, and ends in a thread-like appendage. The eyes are large and the large mouth has long pointed teeth, similar to fangs. The lateral line begins at the upper edge of the gill cover, runs obliquely behind the tips of the pectoral fins, then straight near the ventral contour. 

Features of fish fins

The caudal fin is absent. The dorsal fin is long, extending from the head to the caudal peduncle. The anal fin is reduced to tiny spines, usually ingrown or slightly piercing the skin. The anterior margin of the pectoral fin awn is not serrate. Dorsal spines (total): 3. Dorsal soft rays (total): 130-135. Anal soft rays: 100-105. 

Fish colouring

The body is silvery-steel coloured (resembling a sabre), but turns silver-grey after death. The fins are usually translucent and may have a yellowish tinge.

Distribution

Found in tropical and subtropical seas in all oceans. In the eastern Atlantic they are found from the southern United Kingdom to southern Africa, including the Mediterranean. In the western Atlantic they are found from Virginia (sometimes Cape Cod) to northern Argentina, including the Caribbean and the Gulf of Mexico. In the eastern Pacific they are found from southern California to Peru. They are widespread in the Indo-Pacific, from the Red Sea to South Africa, Japan, the entire coast of Australia (except Tasmania and Victoria) and Fiji, and are absent from the central Pacific, including Hawaii. Some populations are migratory.

Habitat

Marine, benthic-pelagic, amphidromous fish. It prefers relatively shallow coastal areas to muddy bottoms, but occasionally enters estuaries and has been recorded from 0 to 589 metres. 

Size

Maximum length is 234 cm, usually about 1 m, body mass reaches 5 kg. Life expectancy is up to 15 years.

Behavior

Juveniles migrate vertically, ascending at night to feed on krill and small fish, and returning to the seafloor during the day. Large adults, which feed mainly on fish, travel in the opposite direction.

Food and feeding habits

Juveniles and immature individuals feed on euphausiids, pelagic crustaceans and small fish. Adults switch to a piscivorous diet.

Reproduction

Spawning is temperature dependent as the larvae prefer water warmer than 21°C (70°F) and cannot tolerate temperatures below 16°C (61°F). Spawning therefore occurs throughout the year in tropical regions and in spring and summer in colder regions. During the spawning season, each female lays many thousands of eggs, which hatch in three to six days. The eggs and larvae are pelagic. In the Sea of Japan, most individuals reach maturity at two years of age, but some reach maturity after one year.

Fishing

Valuable commercial fish.

Relationship with a person

It is used for cooking. The flesh is dense but tender when cooked, with a moderate 'fishy' taste and smell, and a low fat content.