The anglerfish are fish of the teleost order Lophiiformes. They are bony fish named for their characteristic mode of predation, in which a modified luminescent fin ray (the esca or illicium) acts as a lure for other fish. The luminescence comes from symbiotic bacteria, which are thought to be acquired from seawater, that dwell in and around the sea.
Some anglerfish are notable for extreme sexual dimorphism and sexual symbiosis of the small male with the much larger female, seen in the suborder Ceratiidae, the deep sea anglerfish. In these species, males may be several orders of magnitude smaller than females.
Anglerfish occur worldwide. Some are pelagic (dwelling away from the sea floor), while others are benthic (dwelling close to the sea floor). Some live in the deep sea (such as the Ceratiidae), while others on the continental shelf, such as the frogfishes and the Lophiidae (monkfish or goosefish). Pelagic forms are most often laterally compressed, whereas the benthic forms are often extremely dorsoventrally compressed (depressed), often with large upward-pointing mouths.