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Cutlassfish Scientific Classification

The Cutlassfish are about 45 species of predatory fish in the family Trichiuridae of the order Scombriformes found in seas around the world. Fish of this family are long, slender, and often steel blue or silver in color, hence the name. They have reduced or absent pelvic and caudal fins, giving them an eel-like appearance and large fangs.

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.

Habitat and Activity

Cutlassfish are located in the depths (50-1500 m) of tropical and temperate marine waters, such as the West Indies, Gulf of Mexico, and south Atlantic coast of the United States (Schultz, 2011), but are also found in coastal waters worldwide. During the day, juvenile and small adult fish form schools in the depths.  Adults feed on pelagic prey during the day.

Food And Feeding

Cutlassfish are carnivores and lie in wait and ambush prey near the water surface. Juvenile and young adults suspend their bodies vertically with their jaws facing upwards and remain motionless. This decreases the cross section of the body visible to other smaller fish or squid. The mouth is large and tapering allowing for active hunting. When prey passes nearby, the cutlassfish lunges upwards and seizes it with the fang like teeth. The cutlassfish can be propelled upwards, out of the water if the lunge is in shallow water. They feed on anchovies, sardines, squid and crustaceans (Schultz, 2011). They change feeding habits; at the juvenile stage, they feed mostly on zooplankton but become carnivorous when adult feeding mainly on pelagic fishes.

Beautiful school of Cutlassfish, vertically feeding in the water column. Lit up by the lights on ROV SuBastian while exploring on the #CostaRicaDeep expedition.

Cutlassfish Population Ecology

Cutlassfish is seen along the coast in late spring and summer. Adult males move north to warmer waters to feed, and females stay during the cold season. Saber larvae are found on plateaus and slopes around temperatures above 21°C. Juveniles reside in coastal waters, adults on terraces, and adults are found in tropical regions.

Males are considered to maintain an exclusive indoor range. During the rainy season, feeding intensity increases as food sources increase, i.e. shellfish increase in number as well as shrimp. The population abundance of these top predators serves as a good indicator of primary productivity. Populations fluctuate as the numbers of crustaceans and other food sources increase.

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