Moonfish is the name for a variety of fish, but is used regionally, so that people may speak of the moonfish at cross-purposes without realizing it, each referring to a different fish. Adding the genus and species names can be helpful in these circumstances.
One fish called moonfish is the opah (Lampris regius), a commercial fish that lives among the Hawaiian Islands. Opah are often found with tunas and billfish rather than in schools of their own kind. They have a silver-gray, speckled upper body and a red belly, with red fins and tail. They are shaped rather like a pentagon and weigh between 60 and 200 pounds (27.2 to 90.7 kg). Opah are sold as fresh fish, primarily for restaurant use in sashimi and broiling.
Another moonfish — sometimes spelled as an open compound, moon fish Branchiostegus wardi) — also known as Ward’s Horsehead or Tile Fish which is found in the Pacific Ocean off the coast of New South Wales and Queensland, Australia. It is a long, thin, fish with a reddish silver body and a blunt snout and grows up to 17.7 inches (45 cm) in length. It is eaten, but is not highly rated as a food fish.
A third fish known as moonfish (Mene maculata) is found in the Indo-Pacific region, east of Africa, the South China Sea, south of Japan, and north and northeast of Australia. Also called Toothed Soapy or Pony Fish, it has a shape somewhat like the Opah, but only grows to a length of about 11.8 inches (30 cm). It is a commercial fish and is known as danggit in the Philippines, where it is popular. It is also sold in frozen portions in China.
The so-called “Atlantic Moonfish” (Selene setapinnis) has a squarish shape and is found in the waters of Brazil. It can grow up to 23.6 in (60 cm) and weighs up to about 10 pounds (4.6 kg). It, too, is a commercial fish and sold in frozen portions.
Other fish referred to as moonfish include Vomer setapinnis, as well as an extinct group of fish from the Jurassic period from the genus Dapedium and fish other than those mentioned above from the genera Bathyaethiops, Brosme, Chaetodipterus, Lampris, Mola, Monodactylus, Pomoxis, Selene, and Trachinotus.