Life History and Behavior of Red Lionfish

Reproduction

They are mainly a solitary species and courting is the only time when aggregate, generally 1 male with several females. Both P. volitans and P. miles are gonochoristic, only showing sexual dimorphism during reproduction. Similar courtship behaviors are observed in all Pterois species. These behaviors include circling, sidewinding, following, and leading. The lionfish are mostly nocturnal, leading to the behaviors typically around nightfall and continuing through the night. After courtship the female releases two egg masses that are fertilized by the male before floating to the surface. The eggs are kept together by a mucus which disintegrates within a few days to release larvae. Data collected suggests that lionfish can reproduce monthly, through all seasons of the year.

Early life history and dispersal

Although little is known about the larval stage of the lionfish, some traits of the larvae include a large head, a long, triangular snout, long, serrated head spines, a larve pelvic spine, and coloration only in the pelvic fins. Larvae hatch 36 hours after fertilization. The larvae are good swimmers and can eat small ciliates just 4 days after conception. The larval stage is the shortest stage of the lionfish’s life, with a duration of about one month.

Predators and Prey

There has been very little documentation of any true predators of the lionfish. It has been suggested that larger fish and sharks that should be able to eat the lionfish have not recognized the lionfish as prey due to the novelty of the fish in the invaded areas. Lionfish have, however, infrequently been found in the stomachs of grouper. The lionfish themselves are voracious feeders and have outcompeted and filled the niche of the overfished snapper and grouper. When hunting, they corner prey using their large fins and then use their quick reflexes to swallow the prey whole. They hunt primarily from late afternoon to dawn. High rates of prey consumption, a wide variety of diet, and increasing abundance of the fish lead to concern that the fish may have a very active role in the already declining trend of fish densities. As the fish become more abundant, they are becoming a threat to the fragile ecosystems that they have invaded. Between outcompeting similar fish and having a large diet, the lionfish is drastically changing and disrupting the food chains that hold the marine ecosystems together. As these chains are distrupted, we continue to see declining densities of other fish populations, as well as a decline in the overall diversity of coral reef areas.

Lionfish have venomous dorsal spines that are used purely for defense. When threatened, the fish often faces its attacker in an upside down posture which brings its spines to bear. However, a lionfish's sting is usually not fatal to humans. If a human is envenomed, that person will experience extreme pain, and possibly headaches, vomiting, and breathing difficulties. A common treatment is soaking the afflicted area in hot water, as very few hospitals carry specific treatments. However, immediate emergency medical treatment is still advised, as some people are more susceptible to the venom than others.

As an invasive

Two of the fifteen species of Pterois, P. volitans and P. miles, have established themselves as significant invasive species off the East Coast of the United States and in the Caribbean. About 93% of the invasive lionfish population is P. volitans, also known as the Red Lionfish. The red lionfish is found off the East Coast of the United States and the Caribbean Sea, and was likely first introduced off the Florida coast in the early to mid- 1990s. Adult lionfish specimens are now found along the United States East Coast from Cape Hatteras, North Carolina, to Florida, and in Bermuda, the Bahamas, and throughout the Caribbean, including the Turks and Caicos, Haiti, Cuba, Dominican Republic, Puerto Rico, St. Croix, Belize, Honduras, Aruba and Mexico.

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Red Lionfish

The red lionfish (Pterois volitans) is a venomous coral reef fish in the family Scorpaenidae, order Scorpaeniformes. P. volitans is natively found in the Indo-Pacific region, but has become a huge invasive problem in the Caribbean Sea and along the East coast of the United States along with a similar species, Pterois miles. Red lionfish are clad in white stripes alternated with red, maroon, or brown. Adults can grow as large as 17 inches (43 cm) in length while juveniles may be shorter than 1 inch (2.5 cm). They can live up to 10 years. The fish has large venomous spines that protrude from the body like a mane, giving it the common name of the lionfish. The venomous spines make the fish inedible or deter most potential predators. Lionfish reproduce monthly and are able to quickly disperse during their larval stage for expansion of their invasive region. There are no definitive predators of the lionfish, and many organizations are promoting the harvest and consumption of lionfish in efforts to prevent further increases in the already high population densities.

Description and Taxonomy

P. volitans has very few fish that resemble it, with the most common being Pterois miles, the devil firefish. The visual distinguishable trait between the two similar species is the extra dorsal and anal fin ray present on P. volitans. It has also been reported that P. volitans reaches to the Western and Central Pacific and Western Australia. P. miles is found in the Red Sea, Persian Gulf, and Indian Ocean. Mitochondrial DNA analyses have proven that the two species are genetically different. It is unknown whether or not the two species hybridize, although no differences have been found in their reproductive biology. Both species are considered invasive along the East Coast of the United States, with approximately 93% of the population consisting of P. volitans. Genetic studies have shown that a strong founder effect has occurred, and there is low genetic diversity in the populations in the Atlantic.

The red lionfish is part of the family Scorpaenidae, order Scorpaeniformes, and suborder Pteroidae. Lionfish have distinctive red, maroon, and white vertical stripes. Fleshy tentacles protrude from above the eyes and below the mouth. The fish have fan-like pectoral fins with venomous spines, 13 long separated dorsal spines, and 3 anal spines. Lionfish larvae are planktonic, and adults can be as large as 17 inches (43 cm) in length. Lionfish generally inhabit rocky and coral reef areas, and can be found at depths between 1 metre (3.3 ft)in shallow mangroves and 131.5 metres (431 ft). They are most often found under ledges or in shaded cave areas, in an almost motionless state. As they become more abundant, there have been claims of the fish also being found in bays and estuaries. The most distinguishable characteristic of the red lionfish, as well as all scorpionfishes, are the venomous spines protruding from the body. An extremely showy and ornate fish such as the lionfish should be an easy target for predators, but the large spines act as a great defense. The spines are incorporated into certain fins of the fish, and have venom glands at the base of the spine. These glands protect the fish from predation, delivering a painful and potentially fatal venomous “sting” to predators or a human that may come in contact with a lionfish.

Geographic Distribution

P. volitans occurs natively in the Indo-Pacific region, including the Western and Central Pacific and off the coast of Western Australia.


See also :

• Life History and Behavior of Red Lionfish

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Pterois fish

Pterois is a genus of venomous marine fish found mostly in the Indo-Pacific, known collectively as the lionfish. Pterois is characterized by red, white and black stripes, showy pectoral fins and venomous spiky tentacles. Pterois are classified into fifteen different species, but Pterois radiata, Pterois volitans and Pterois miles are the most commonly studied. Pterois are popular aquarium fish and are readily utilized in the culinary world.

In the mid 1990s, the species P. volitans and P. miles were unintentionally introduced into the Atlantic Ocean and have become an invasive species along the East Coast of the United States.

Morphology and Behavior

Pterois range in size from 6.2 to 42.4 cm with typical adults measuring 38 cm and weighing an average of 480 g. They are well known for their ornate beauty, venomous spines and unique tentacles. Juvenile lionfish have a unique tentacle located above their eye sockets that varies in phenotype between species. It is suggested that the evolution of this tentacle serves to continually attract new prey; studies also suggest that it plays a role in sexual selection

Hazard to Humans

Lionfish are known for their venomous tentacles, a feature that is uncommon among marine fish in the East Coast coral reefs. The potency of their venom makes them excellent predators and dangerous to fishermen and divers. Pterois venom produced negative inotropic and chronotropic effects when tested in both frog and clam hearts and has a depressing effect on rabbit blood pressure. These results are thought to be due to nitric oxide release. In humans, Pterois venom can cause systemic effects such as vomiting, fever and sweating and has been lethal in a few cases.

Prey

According to a study that involved the dissection of over 1,400 lionfish stomachs from Bahamian to North Carolinian waters, Pterois prey mostly on small fishes, invertebrates and mollusks in large amounts, with some specimens’ stomachs containing up to six different species of prey. The amount of prey in lionfish stomachs over the course of the day suggest that lionfish feed most actively from 7:00-11:00 A.M., with decreased feeding throughout the afternoon. Lionfish are skilled hunters, using specialized bilateral swim bladder muscles to provide exquisite control of location in the water column, allowing the fish to alter its center of gravity to better attack prey. The lionfish then spreads its large pectoral fins and swallows its prey in a singe motion. Tiger grouper (Mycteroperca tigris) have been shown to occasionally prey on Pterois, but these findings have been few and far between.

Pterois can live from five to fifteen years and have complex courtship and mating behaviors. Females release two mucus-filled egg clusters frequently, which can contain as many as fifteen thousand eggs. Studies on Pterois reproductive habits are have increased significantly in the past decade.

Native Waters

The lionfish is a predator native to the Indo-Pacific. It aggressively preys on small fish and invertebrates. They can be found around the seaward edge of reefs and coral, in lagoons, and on rocky surfaces to fifty meters. They show a preference for turbid inshore areas and in harbors. Lionfish have a generally hostile attitude and are territorial towards other reef fish. Many universities in the Indo-Pacific have documented reports of Pterois aggression towards divers and researchers.

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Frogfish

Frogfishes, family Antennariidae, are a type of anglerfish in the order Lophiiformes. They are known as anglerfishes in Australia, where 'frogfish' refers to a different type of fish. Frogfishes are found in almost all tropical and subtropical oceans and seas around the world, the primary exception being the Mediterranean Sea.

Range

Frogfish live in the tropical and subtropical regions of the Atlantic and Pacific, as well as in the Indian Ocean and the Red Sea. Their habitat lies for the most part between the 20-degree isotherms, in areas where the surface level water usually has a temperature of 20 C (68 F) or more. They extend beyond the 20-degree isotherms in the area of the Azores, Madeira, and the Canary Islands, along the Atlantic coast of the USA, on the south coast of Australia and the northern tip of New Zealand, coastal Japan, around Durban, South Africa, and at Baja California.[2] The most types are found in the Indo-Pacific region with the highest concentration around Indonesia. In the tiny Lembah Strait, north-east of Sulawesi, divers have found nine different species. Frogfish live generally on the ocean floor around coral or rock reefs, at most up to 100 meters (330 ft) deep.

There are a few exceptions to these general limits. The Brackishwater Frogfish is at home in ocean waters as well as brackish and fresh water around river mouths. The Sargassumfish lives in clumps of drifting sargassum, which often floats into the deeper ocean and have been known to take the sargassumfish as far north as Norway.

Features

Frogfish have a stocky appearance, atypical of fish. Ranging from 2.5–38 cm (1-15 inches) long, their plump, high-backed, non-streamlined body is scaleless and bare, often covered with bumpy, bifurcated spinules. Their short bodies have between 18 and 23 vertebrae and their mouths are upward pointed with palatal teeth. They are often brightly colored, white, yellow, red, green, or black or spotted in several colors in order to blend in with their coral surroundings. Coloration can also vary within one species, making it difficult to differentiate between them.

Rather than typical dorsal fins, the front-most of the three fins is called the illicium or "rod" and is topped with the esca or "lure". The illicium often has striped markings, while the esca takes a different form in each species. Because of the variety of colors even within a single species, the esca and illicium is a useful tool to differentiate among different varieties. Some of them resemble fish, some shrimp, some polychaetes, some tubeworms, and some simply a formless lump; one genus, Echinophryne has no esca at all. Despite very specific mimicry in the esca, examinations of stomach contents do not reveal any specialized predation patterns, for example, only worm-eating fish consumed by frogfish with worm-mimicking esca. If lost, the esca can be regenerated. In many species the illicium and esca can be withdrawn into a depression between the second and third dorsal fins for protection when they are not needed.

Frogfish have small, round gill openings behind their pectoral fins. With the exception of Butler's frogfish and the Rough Anglerfish, frogfish use a gas bladder to control their buoyancy.

Mimicry and camouflage

The unusual appearance of the frogfish is designed to conceal it from predators and sometimes to mimic a potential meal to its prey. In ethology, the study of animal behavior, this is known as aggressive mimicry. Their unusual shape, color, and skin textures disguise frogfish. Some resemble stones or coral while others imitate sponges, or sea squirts with dark splotches instead of holes. In 2005, a species was discovered, the striated frogfish, that mimics a sea urchin while the sargassumfish is colored to blend in with the surrounding sargassum. Some frogfish are covered with algae or hydrozoa. Their camouflage can be so perfect, that sea slugs have been known to crawl over the fish without recognizing them.

For the scaleless and unprotected frogfish, the camouflage is an important defense against predators. Some frogfish can also inflate themselves, like pufferfish, by sucking in water in a threat display. In aquariums and in nature, frogfish have been observed, when flushed from their hiding spots and clearly visible, to be attacked by clownfish, damselfish, and wrasse, and in aquariums, to be killed.

Many frogfish can change their color. The light colors are generally yellows or yellow-browns while the darker are green, black, or dark red. They usually appear with the lighter color, but the change can last anywhere from a few days to several weeks. It is unknown what triggers the change.

Movement

Frogfish generally do not move very much, preferring to lie on the sea floor and wait for prey to approach. Once the prey is spotted, they can approach slowly using their pectoral and pelvic fins to walk along the floor. They have two "gaits" that they can use. In the first they alternately move their pectoral fins forward, propelling themselves somewhat like a two-legged tetrapod, leaving the pelvic fins out. Alternately, they can move in something like a slow gallop, whereby they move their pectoral fins simultaneously forward and back, transferring their weight to the pelvic fins while moving the pectorals forward. With either gait, then can only cover short stretches.

In open water, frogfish can swim with strokes of the tail fin. They also have a kind of jet propulsion that is often used by younger frogfish. It is achieved by rhythmically forcing their breath-water out through their gill openings, which lie behind their pelvic fins.

The sargassum frogfish has adapted fins which can grab strands of sargassum, enabling it to "climb" through the seaweed.

Hunting

Frogfish eat crustaceans, other fish, and even each other. When potential prey is first spotted, the frogfish follows it with its eyes. Then, when it approaches within roughly seven body-lengths, the frogfish begins to move its illicium in such a way that the esca mimics the motions of the animal it resembles. As the prey approaches, the frogfish will slowly move itself to prepare for its attack; sometimes this involves approaching the prey or "stalking" while sometimes it is simply adjusting its mouth angle. The catch itself is made by the sudden opening of the jaws, which enlarges the volume of the mouth cavity up to twelve-fold, pulling the prey into the mouth along with water. The attack can be as fast as 6 milliseconds. The water flows out through the gills, while the prey is swallowed and the esophagus closed with a special muscle to keep the victim from escaping. In addition to expanding their mouths, frogfish can also expand their stomachs to swallow animals up to twice their size.

Slow-motion filming has shown that the frogfish sucks in its prey in just six milliseconds, so fast that other animals can't see it happen. This is less time than it takes a muscle to contract so the source of the motion remains unknown. Frogfish have also been observed to eat lionfish; the latter's poison appears to have no effect.

See also..

• Frogfish Reproduction

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Lanternfish

Lanternfishes (or myctophids, from the Greek mykter, "nose" and ophis, "serpent") are small mesopelagic fish of the large family Myctophidae. One of two families in the order Myctophiformes, the Myctophidae are represented by 246 species in 33 genera, and are found in oceans worldwide. They are aptly named after their conspicuous use of bioluminescence. Their sister family, the Neoscopelidae, are much fewer in number but superficially very similar; at least one neoscopelid shares the common name 'lanternfish': the large-scaled lantern fish, Neoscopelus macrolepidotus.

Sampling via deep trawling indicates that lanternfish account for as much as 65% of all deep sea fish biomass. Indeed, lanternfish are among the most widely distributed, populous, and diverse of all vertebrates, playing an important ecological role as prey for larger organisms. With an estimated global biomass of 550 - 660 million metric tonnes, several times the entire world fisheries catch, lanternfish also account for much of the biomass responsible for the deep scattering layer of the world's oceans. In the Southern Ocean, myctophids provide an alternative food resource to krill for predators such as squid and the king penguin. Although plentiful and prolific, currently only a few commercial lanternfish fisheries exist: limited operations off South Africa, in the sub-Antarctic, and in the Gulf of Oman.

Description

Lanternfish typically have a slender, compressed body covered in small, silvery deciduous cycloid scales (ctenoid in four species), a large bluntly rounded head, large elliptical to round lateral eyes (dorsolateral in Protomyctophum species), and a large terminal mouth with jaws closely set with rows of small teeth. The fins are generally small, with a single high dorsal fin, a forked caudal fin, and an adipose fin. The anal fin is supported by a cartilaginous plate at its base, and originates under, or slightly behind, the rear part of the dorsal fin. The pectoral fins, usually with eight rays, may be large and well-developed to small and degenerate, or completely absent in a few species. In some species, such as those of the genus Lampanyctus, the pectorals are greatly elongated. Most lanternfish have a gas bladder, but it degenerates or fills with lipids during the maturation of a few species. The lateral line is uninterrupted.

In all but one species, Taaningichthys paurolychnus, a number of photophores (light-producing organs) are present; these are paired and concentrated in ventrolateral rows on the body and head. Some may also possess specialised photophores on the caudal peduncle, in proximity to the eyes (e.g., the "headlights" of Diaphus species), and luminous patches at the base of the fins. The photophores emit a weak blue, green, or yellow light, and are known to be arranged in species-specific patterns. In some species, the pattern varies between males and females. This is true for the luminous caudal patches, with the males' being typically above the tail and the females' being below the tail.

Lantern fish are generally small fish, ranging from about 2 centimetres (0.79 in) to 30 centimetres (12 in) in length, with most being under 15 centimetres (5.9 in). In life, shallow-living species are an iridescent blue to green or silver, while deeper-living species are dark brown to black.

Ecology

Lanternfish are well-known for their diel vertical migrations: during daylight hours most species remain within the gloomy bathypelagic zone, between 300 metres (980 ft) and 1,500 metres (4,900 ft) in depth, but towards sundown the fish begin to rise into the epipelagic zone, between 10-100 metres (33-330 feet) deep. The lanternfish are thought to do this to avoid predation, and because they are following the diel vertical migrations of zooplankton, upon which the lanternfish feed. After a night spent feeding in the surface layers of the water column, the lanternfish begin to descend back into the lightless depths and are gone by daybreak.

Most species remain near to the coast, schooling over the continental slope. Different species are known to segregate themselves by depth, forming dense, discrete conspecific layers, probably to avoid competition between different species. Due to the lanternfishes' gas bladders, these layers are visible on sonar scans and give the impression of a "false bottom": this is the so-called deep-scattering layer that so perplexed early oceanographers.

There is great variability in migration patterns within the family. Some deeper-living species may not migrate at all, while others may do so only sporadically. Migration patterns may also be dependent on life history stage, sex, latitude, and season.

The arrangements of lanternfish photophores are different for each species, so it is assumed that their bioluminescence plays a role in communication, specifically in shoaling and courtship behaviour. The concentration of the photophores on the flanks of the fish also indicate the light's use as camouflage; in a strategy termed counterillumination, the lanternfish regulate the brightness of the bluish light emitted by their photophores to match the ambient light level above, effectively masking the lanternfishes' silhouette when viewed from below.

A major source of food for many marine animals, lanternfish are an important link in the food chain of many local ecosystems, being heavily preyed upon by whales and dolphins; large pelagic fish such as salmon, tuna and sharks; grenadiers and other deep-sea fish (including other lanternfish); pinnipeds; sea birds, notably penguins; and large squid such as the jumbo squid, Dosidicus gigas. Lantern fish themselves have been found to feed on bits of plastic debris accumulating in the oceans. At least one lantern fish was found with over 80 pieces of plastic chips in its gut, according to scientists monitoring ocean plastic in the Pacific Ocean's Eastern Garbage Patch.

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Deep sea fish

Deep sea fish is a term for any fish that lives below the photic zone of the ocean. The lanternfish is, by far, the most common deep sea fish. Other deep sea fish include the flashlight fish, cookiecutter shark, bristlemouths, anglerfish, and viperfish.

Because the photic zone typically extends only a few hundred meters below the water, about 90% of the ocean volume is invisible to humans. The deep sea is also an extremely hostile environment, with pressures between 20 and 1,000 atmospheres (between 2 and 100 megapascals), temperatures between 3 and 10 degrees Celsius, and a lack of oxygen. Most fish that have evolved in this harsh environment are not capable of surviving in laboratory conditions, and attempts to keep them in captivity have led to their deaths. For this reason little is known about them, as there are limitations to the amount of fruitful research that can be carried out on a dead specimen and deep sea exploratory equipment is very expensive. As such, many species are known only to scientists and have therefore retained their scientific name.

The fish of the deep sea are among the strangest and most elusive creatures on Earth. In this deep unknown lie many unusual creatures we still have yet to study. Since many of these fish live in regions where there is no natural illumination, they cannot rely solely on their eyesight for locating prey and mates and avoiding predators; deep sea fish have evolved appropriately to the extreme sub-photic region in which they live. Many deep sea fish are bioluminescent, with extremely large eyes adapted to the dark. Some have long feelers to help them locate prey or attract mates in the pitch black of the deep ocean. The deep sea angler fish in particular has a long fishing-rod-like adaptation protruding from its face, on the end of which is a bioluminescent piece of skin that wriggles like a worm to lure its prey. The lifecycle of deep sea fish can be exclusively deep water although some species are born in shallower water and sink on becoming born. Due to the poor level of photosynthetic light reaching deep sea environments, most fish need to rely on organic matter sinking from higher levels, or, in rare cases, hydrothermal vents for nutrients. This makes the deep sea much poorer in productivity than shallower regions. Consequently many species of deep sea fish are noticeably smaller and have larger mouths and guts than those living at shallower depths. It has also been found that the deeper a fish lives, the more jelly-like its flesh and the more minimal its bone structure. This makes them slower and less agile than surface fish.

Sampling via deep trawling indicates that lanternfish account for as much as 65% of all deep sea fish biomass. Indeed, lanternfish are among the most widely distributed, populous, and diverse of all vertebrates, playing an important ecological role as prey for larger organisms. With an estimated global biomass of 550 - 660 million metric tonnes, several times the entire world fisheries catch, lanternfish also account for much of the biomass responsible for the deep scattering layer of the world's oceans. In the Southern Ocean, Myctophids provide an alternative food resource to krill for predators such as squid and the King Penguin. Although plentiful and prolific, currently only a few commercial lanternfish fisheries exist: These include limited operations off South Africa, in the sub-Antarctic, and in the Gulf of Oman.

A 2006 study by Canadian scientists has found five species of deep sea fish – roundnose grenadier, onion-eye grenadier, blue hake, spiny eel and spinytail skate – to be on the verge of extinction due to the shift of commercial fishing from continental shelves to the slopes of the continental shelves, down to depths of 1600 meters. The slow reproduction of these fish – they reach sexual maturity at about the same age as human beings – is one of the main reasons that they cannot recover from the excessive fishing.

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Anglerfish Classification

FishBase, Nelson, and Pietsch list eighteen families, but ITIS lists only sixteen. The following taxa have been arranged to show their evolutionary relationships.

• Suborder Lophioidei 
• Lophiidae (goosefishes or monkfishes) 
• Suborder Antennarioidei
• Antennariidae (frogfishes)
• Tetrabrachiidae (four-armed frogfishes)
• Brachionichthyidae (handfishes)
• Lophichthyidae (Boschma's frogfish — monotypic)
• Suborder Chaunacoidei
• Chaunacidae (sea toads) 
• Suborder Ogcocephaloidei
• Ogcocephalidae (batfishes)
• Suborder Ceratioidei (deepsea families)
• Centrophrynidae (prickly seadevils — monotypic)
• Ceratiidae (warty seadevils)
• Himantolophidae (footballfishes)
• Diceratiidae (doublespine seadevils)
• Melanocetidae (black seadevils)
• Thaumatichthyidae (wolf-trap seadevils)
• Oneirodidae (dreamers)
• Caulophrynidae (fanfin seadevils)
• Neoceratiidae (needlebeard seadevil — monotypic)
• Gigantactinidae (whipnose seadevils) 
• Linophrynidae (leftvent seadevils)

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Anglerfish

Anglerfishes are members of the teleost order Lophiiformes (pronounced /ˌlɑːfiːəˈfɔrmiːz/). They are bony fishes named for their characteristic mode of predation, wherein a fleshy growth from the fish's head (the esca or illicium) acts as a lure; this is considered analogous to angling.

Some anglerfishes are pelagic (live in the open water), while others are benthic (bottom-dwelling). Some live in the deep sea (e.g., Ceratiidae) and others on the continental shelf (e.g., the frogfishes Antennariidae and the monkfish/goosefish Lophiidae). They occur worldwide. Pelagic forms are most laterally (sideways) compressed whereas the benthic forms are often extremely dorsoventrally compressed (depressed) often with large upward pointing mouths.

A mitochondrial genome phylogenetic study suggested that anglerfishes diversified in a short period of the early to mid Cretaceous, between 130 and 100 million years ago.

The fish are named for their characteristic method of predation. Anglerfish typically have at least one long filament sprouting from the middle of the head; these are the detached and modified three first spines of the anterior dorsal fin. In most anglerfish species, the longest filament is the first (the illicium). This first spine protrudes above the fish's eyes, and terminates in an irregular growth of flesh (the esca) at the tip of the spine. The spine is movable in all directions, and the esca can be wiggled so as to resemble a prey animal, and thus to act as bait to lure other predators close enough for the anglerfish to devour them whole. The jaws are triggered in automatic reflex by contact with the tentacle.

Some deep-sea anglerfishes of the bathypelagic zone emit light from their escas to attract prey. This bioluminescence is a result of symbiosis with bacteria. The bacteria may enter the esca from the seawater through small pores; however, this is speculative and the mechanism by which ceratioids harness these bacteria is unknown. In the confines of the esca, they can multiply until their density is such that their collective glow is very bright.

In most species, a wide mouth extends all around the anterior circumference of the head, and both jaws are armed with bands of long pointed teeth, which are inclined inwards, and can be depressed so as to offer no impediment to an object gliding towards the stomach, but prevent its escape from the mouth. The anglerfish is able to distend both its jaw and its stomach (its bones are thin and flexible) to enormous size, allowing it to swallow prey up to twice as large as its entire body.

Some benthic (bottom-dwelling) forms have arm-like pectoral fins which the fish use to walk along the ocean floor. The pectoral and ventral fins are so articulated as to perform the functions of feet, enabling the fish to move, or rather to walk, on the bottom of the sea, where it generally hides itself in the sand or amongst seaweed. All around its head and also along the body, the skin bears fringed appendages resembling short fronds of seaweed, a structure which, combined with the extraordinary faculty of assimilating the colour of the body to its surroundings, camouflage the fish in areas abundant with prey.

Some anglerfishes, like those of the Ceratioid group (Ceratiidae), employ an unusual mating method. Because individuals are presumably locally rare and encounters doubly so, finding a mate is problematic. When scientists first started capturing ceratioid anglerfish, they noticed that all of the specimens were females. These individuals were a few centimetres in size and almost all of them had what appeared to be parasites attached to them. It turned out that these "parasites" were highly reduced male ceratioids.

At birth, male ceratioids are already equipped with extremely well developed olfactory organs[dubious – discuss] that detect scents in the water. The male ceratioid lives solely to find and mate with a female. They are significantly smaller than a female angler fish, and may have trouble finding food in the deep sea. Furthermore, the growth of the alimentary canals of some males becomes stunted, preventing them from feeding. These features necessitate his quickly finding a female anglerfish to prevent death. The sensitive olfactory organs help the male to detect the pheromones that signal the proximity of a female anglerfish. When he finds a female, he bites into her skin, and releases an enzyme that digests the skin of his mouth and her body, fusing the pair down to the blood-vessel level. The male then slowly atrophies, first losing his digestive organs, then his brain, heart, and eyes, and ends as nothing more than a pair of gonads, which release sperm in response to hormones in the female's bloodstream indicating egg release. This extreme sexual dimorphism ensures that, when the female is ready to spawn, she has a mate immediately available. Multiple males can be incorporated into a single female.

The spawn of the anglerfish of the genus Lophius consists of a thin sheet of transparent gelatinous material 0.6 or 0.9 metres (2 or 3 feet) wide and 7.6 to 9 metres (25–30 feet) long. The eggs in this sheet are in a single layer, each in its own cavity. The spawn is free in the sea. The larvae are free-swimming and have the pelvic fins elongated into filaments. Such an egg sheet is rare among fish.

One family Lophiidae is of commercial interest with fisheries found in the in north-western Europe, eastern North America, Africa and the Far East. In Europe and North America, the tail meat of fish of the genus Lophius, known as goosefish (North America) or monkfish, is widely used in cooking, and is often compared to lobster tail in taste and texture. In Asia, especially Korea and Japan, it is a delicacy.

Northwest European Lophius spp. are listed by the ICES as "outside safe biological limits." Additionally, anglerfish are known to occasionally rise to the surface during El Niño, leaving large groups of dead anglerfish floating on surface.

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. The Greenpeace International seafood red list is a list of fish commonly sold worldwide which have a very high likelihood of being sourced from unsustainable fisheries.

See Also

• Anglerfish Classification

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