Anglerfishes are fish that generally inhabit great depths (mostly 200 meters, although there are records up to 1,000 meters) on continental shelves, although certain species also inhabit more superficial waters.
The head of the Anglerfishes is especially spiny. It is rounded, compressed dorsoventrally, and has numerous sharp spines and ridges on both the dorsal and lateral surface of the head. At the base of the pectoral fins, on the upper flank, there is a spine of considerable size. They also have spines on both sides of the face just behind the mouth, as well as two spiny bony ridges on the face that run all the way to the back of the eyes. The intraorvital space is slightly concave. Anglerfishes have a very large, wide, slightly upwardly oriented mouth. The upper jaw is protractile, and the lower jaw is protruding. Both jaws are equipped with numerous long and sharp teeth. The gill openings are large. The width of the head is lost as the body moves towards the back of the fish.
Anglerfishes have two separate dorsal fins. The first is composed of 2-3 individual spines and is located on the head. These may or may not be attached by a membrane to a second piece of dorsal fin located at the level of the pectoral fins. The first spine of the dorsal fin in the head has been transformed in certain species into a reed (illicium) finished at the top with a fleshy bait (esca) which is used to attract its prey towards the mouth. The second dorsal fin has soft spokes. The pelvic fins, in those species that have them, are in front of the pectoral fins, and have a spine and 4-5 soft rays. The pectoral fins have 2-5 narrow and elongated spokes. Finally, the anal fin is formed by 6-11 soft spokes that are born at the level of the second dorsal fin.
The lateral line of the Anglerfishes is present, although it is usually indistinguishable. Their skin is soft and devoid of scales. The maximum recorded length of the Anglerfishes is 2 meters, although they mostly reach 25-45 cm in length. They are classified into 18 families and 72 genera, with 358 species, all of them marine.