The cutlassfishes are about 40 species of predatory fish in the family Trichiuridae (order Perciformes) found in seas throughout the world. Fish of this family are long, slender, and generally steely blue or silver in colour, giving rise to their name. They have reduced or absent pelvic and caudal fins, giving them an eel-like appearance, and large fang-like teeth.Some of the species are known as scabbardfishes or hairtails; others are called frostfishes because they appear in late autumn and early winter, around the time of the first frosts.