Butterfly kingfish

The butterfly kingfish ("Gasterochisma melampus") is a species of ray-finned fish in the family Scombridae. It was formerly the only species in the genus "Gasterochisma", but other species have been discovered. It is the type species of the genus "Gasterochisma".
Description.
It resembles a slender tuna. This fish can be found around the world in southern temperate waters of 8–15 °C (46–59 °F), but most commonly under 10 °C (50 °F), and at depths to 200 m (660 ft) in the open ocean.