The anglerfish are ray-finned fish in the order Lophiiformes (). Both the order's common name and scientific name comes from the characteristic mode of predation, in which a modified dorsal fin ray acts as a lure for prey (akin to a human Angling, and likened to a crest or " '"). The modified fin ray, with the very tip being the esca and the length of the structure the illicium''', is adapted to attract specific prey items across the families of anglerfish by using different luring methods.
Anglerfish occur worldwide. The majority are bottom-dwellers, being demersal fish, while the aberrant deep-sea anglerfish are Pelagic fish, (mostly) living high in the water column. Some live in the Deep-sea fish (such as the deep-sea anglerfish and ), while others live in shallower waters, such as the Antennariidae and some Ogcocephalidae.
Anglerfish are notable for their sexual dimorphism, which is sometimes extremely pronounced; the males may be several orders of magnitude smaller in mass than females. This dimorphism has enabled a unique reproductive method in the deep-sea anglerfish; sexual parasitism is the attachment of male to the much larger female, sometimes fusing together as an example of natural parabiosis.
The group Lophidia was conceived by Samuel Garman in 1899; this group was subdivided into the Lophioids (incl. Lophius, Lophiomus, Melanocetus, Dolopichthys, Chaunax, and Chaunacops) and the Halieutoids (incl. Oncocephalus, Halieutaea, Halieutichthys, Halieutichthys, Halieutopsis, Halicmetus, Dibranchus, Dibranchus, and Malthopsis) based on the orientation of the ilicium's base. By 1905, Lophiiformes came into use, at that time being a suborder of Pediculati.
Alternatively, Lophiiformes may be treated as clade within Acanthuriformes; a 2025 paper defines Lophioidei as equivalent to the prior conception of Lophiiformes (the one depicted above) and converts the suborders into infraorders (as seen below). Below are two phylogenetic trees; the left phylogeny elaborates on the relationships of the suborders within Lophiiformes as set out in Pietsch and Grobecker's 1987 Frogfishes of the World: Systematics, Zoogeography, and Behavioral Ecology, while the right phylogeny is based on the 2025 study, where Maile et al combines the analysis of Ultra-Conserved Elements (UCE)s, mitochondrial DNA, and morphological evidence;
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Phylogenetics studies have consistently recovered the Lophiiformes as sister-group to the Tetraodontiformes, with both within the larger clade Acanthuriformes as of 2025. The Lophiiformes and Tetraodontiformes are united by several derived morphological features separating them from other Acanthuriformes, including restricted Fish gill, along with the absence of multiple skeletal elements, such as spines supporting the anal fin, , Nasal bone, and basisphenoid.
A 2010 mitochondrial genome phylogenetic study suggested the anglerfishes diversified in a short period during the early to mid-Cretaceous, between 130 and 100 million years ago. A 2023 preprint reduces this time to the Late Cretaceous, between 92 and 61 million years ago. Other studies indicate that anglerfish only originated shortly after the Cretaceous-Paleogene extinction event as part of a massive adaptive radiation of Percomorpha, although this clashes with the extensive diversity already known from the group by the Eocene. A 2024 study found that all anglerfish suborders most likely diverged from one another during the Late Cretaceous and Paleocene, but the multiple families of deep-sea anglerfishes (Ceratioidei), as well as their trademark sexual parasitism, originated during the Eocene in a rapid radiation following the Paleocene-Eocene thermal maximum. Adaptations to different ranges of Ocean depths may have driven the evolution of anglerfish species and families in prehistory.
Anglerfish appear in the fossil record as follows:
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Anglerfish lengths can vary from , with a few species larger than . The largest members are the European monkfish Lophius piscatorius ( Standard Length, ), the deep-sea warty anglerfish Ceratias holboelli ( Total length), the giant frogfish Antennarius commerson ( TL), and the giant triangular batfish Malthopsis gigas ().
Many suborders are sexually dimorphic, with the deep-sea anglerfish being the most extreme example; male C. holboelli can reach up to long (SL), while females are commonly around TL, potentially weighing an order of magnitude more than her mate. Male Photocorynus spiniceps were measured to be at maturity, and were at one time claimed to be the smallest vertebrate known. However, due to not being free-living (being parasitic males) and the females being , they are now often excluded from the records. Sexual dimorphism is not as pronounced in other suborders; the Lophiid monkfish genus Lophiodes are quite similar in size between the genders (Mean for Males SL; Females SL), and the same is true for Lophius itself (Males ; Females ).
Anglerfish are generally , with shallow-water species such as frogfish often camouflage as rocks, or seaweed. To blend in with the featureless dark depths they inhabit, deep-sea anglerfish are dark colored, with tints ranging from grey to brown.
In most species, a wide mouth extends all around the anterior (front) circumference of the head, and bands of inwardly inclined teeth line both jaws. The teeth can be depressed (swept back) so as to offer no impediment to prey gliding towards the stomach, but to still prevent its escape. Anglerfish are able to distend both their jaw and stomach to enormous size, since their bones are thin and flexible, which allows them to swallow prey up to twice as large as their entire bodies.
The illicial apparatus is most notable in the deep-sea anglerfish (Ceratioidei) as their esca contain bioluminescent bacteria, making them glow in the dark waters of the deeper pelagic zones. In other species the esca possesses different luring mechanisms, such as emitting odoriferous chemicals that attract olfactory-driven prey (batfish, Ogcocephaloidei; possibly sea toads, Chaunacioidei), or by resembling prey attractive to small fish such as shrimp or Marine worm (frogfish, Antennarioidei). When the prey is close enough, the anglerfish catches it using suction feeding, elongated sharp teeth, or both. While sometimes reported to possess a bioluminescent esca, sea toads lack bioluminescent bacteria and do not actually possess this feature.
In at least the triplewart seadevil, the illicium is moved back and forth by five distinct pairs of muscles: namely the shorter erector and depressor muscles that dictate movement of the illicial bone, along with inclinator, protractor, and retractor muscles that aid motion of the Dorsal fin.
Because anglerfish are opportunistic foragers, they show a range of preferred prey with fish at the extremes of the size spectrum, whilst showing increased selectivity for certain prey. One study examining the stomach contents of threadfin anglerfish ( Lophiodes spilurus) off the Pacific coast of Central America found these fish primarily ate two categories of Benthic zone prey: crustaceans and Teleostei fish. The most frequent prey were Pandalidae. 52% of the stomachs examined were empty, supporting the observations that anglerfish are low energy consumers.
The deep-sea anglers often drift without actively swimming; In situ observation of female Oneirodes and (from ROVs) recorded that they often passively float in place or in a current, but they were sometimes observed to attempt to flee from the ROV, beating its pectoral fins in-phase while undulating its tail fin. The lethargic behavior of these ambush predators are suited to the energy-poor environment of the deep sea.
The jaw and stomach of the anglerfish can extend to allow it to consume prey up to twice its size. Because of the limited amount of food available in the anglerfish's environment, this adaptation allows the anglerfish to store food when there is an abundance.
The sea toad Chaunax endeavouri has been observed to retain water in its gills for at least around 26 seconds and up to 4 minutes in some cases. This behavior is thought to be an energy-saving measure as respiration requires energy, thus the fish "holding its breath" may conserve enough energy for such a behavior to be beneficial.
The spawn of all anglerfish are enveloped by a sheath, which has multiple terms referring to it. The spawn of the Lophius anglerfish consists of a thin sheet of transparent gelatinous material wide and may be longer than ; this "egg mass" may contain over a million eggs.Prince, E. E. 1891. Notes on the development of the angler-fish ( Lophius piscatorius). Ninth Annual Report of the Fishery Board for Scotland (1890), Part III: 343–348. The eggs in this sheet are in a single layer, each in its own cavity. The Ichthyoplankton and have the pelvic fins elongated into filaments. It is thought that these egg masses effectively disperse their young over great distances and a large area. A female Linophryne arborifera, with a parasitic male, was observed to have numerous eggs embedded in a gelatinous mass (the "egg raft" or "veil") protruding from the genital opening; the eggs, 0.6–0.8mm in diameter, are among the largest known for any ceratioid.
In Africa, the countries of Namibia and the Republic of South Africa record the highest catches. In Asia, especially Japan, monkfish liver, known as ankimo, is considered a delicacy. Anglerfish is especially heavily consumed in South Korea, where it is featured as the main ingredient in dishes such as Agujjim.
Northwest European Lophius species are heavily fished and are listed by the ICES as "outside safe biological limits".
In 2010, Greenpeace International added the American angler ( Lophius americanus), the angler ( Lophius piscatorius), and the black-bellied angler ( Lophius budegassa) to its seafood red list—a list of fish commonly sold worldwide with a high likelihood of being sourced from unsustainable fisheries. Greenpeace sea-food red list Additionally, anglerfish are known to occasionally rise to the surface during El Niño, leaving large groups of dead anglerfish floating on the surface.
Antennarius biocellatus is known by the common names brackish-water frogfish or freshwater frogfish; being euryhaline, it can live in freshwater for some time, sometimes claimed to be the sole representative of the anglerfish to live in freshwater. Like many frogfish, it has been displayed in Public aquarium, though unlike the other species A. biocellatus are sometimes kept in home aquaria by private .
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