Anglerfish: Characteristics, Unusual Mating and Japanese Food

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ANGLERFISH

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The anglerfish is arguably one of the ocean's ugliest creatures. It sits motionless in the water with its mouth agape waiting for prey to pass its way. The fleshy-tip of the fish's hair-thin dorsal fin hangs in front of its mouth like a worm. When prey comes near, the angelfish sucks it into its mouth faster than the human eye can see. If the prey gets the bait. No problem. The anglerfish simply grows another fleshy tip. Deep sea anglerfish use a lure with bacterial light to attract fish.

There are 168 known species of anglerfish, most of which are found at ocean depths beneath about 300 meters. Some species mate through a process known as sexual parasitism. Males, which are often less than 10 millimeters in length, attach to the body of the larger female. In some cases male anglerfish attach themselves to females that 1,000 times larger than they are.

When they are young anglerfish males are similar in size to females. Anglerfish females can live up to 25 years in the wild, and males can reach 21 years. These fish can be kept in captivity. But they are a popular delicacy in Japan. The growth rate of young anglerfish has been estimated at 13.6 centimeters per year. Males mature sexually at sage six while females reach sexual maturity at age 14. Like most fish, anglerfish likely exhibit indeterminate growth (they just keep growing). Because of the age difference for sexual maturity, female anglerfish have a greater size than male anglerfish at maturity — 73.2–98.0 centimeters in length for females and 48.9–58.0 centimeters in length for males. Anglerfish are a host for over 50 different species of parasites some include the larvae of the species as well as the matured species.

The sea devil anglerfish is is one of the world’s more spectacular-looking fishes. Katherine J. Wu and Rachael Lallensack wrote in Smithsonian magazine: The iconic image of the anglerfish — a deep-sea creature sporting jagged, translucent teeth and a luminescent lure to bait prey — represents only the females of this bunch. Petite, stunted and devoid of glowy baubles, male anglerfish are harder to photograph and far less interesting to look at. Males that luck upon a mate in the deep ocean attach themselves to her much large body for keeps, sucking in nutrients from her body while fertilzing her eggs. [Source: Katherine J. Wu , Rachael Lallensack, Smithsonianmag.com, February 14, 2020]

Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se ; Encyclopedia of Life eol.org ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems ; Woods Hole Oceanographic Institute whoi.edu ; Cousteau Society cousteau.org ; Monterey Bay Aquarium montereybayaquarium.org ; MarineBio marinebio.org/oceans/creatures

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Anglerfish Habitat and Where They Are Found

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There are about 300 known species of anglerfish, some of which are among the deepest-dwelling ocean fish. They can be found in all the world’s oceans. According to Animal Diversity Web: Anglerfish inhabit the ocean at depths of 0 to 1000 meters (0 to 3,280 feet), rarely dropping below the continental slope. This wide range of depths is influenced by fish age and seasonality (water temperatures and prey availability). They lie half-buried in the sediment (sand or mud) as they wait for prey as low as the continental shelf.

Lophius piscatorius, also known as monkfish, is a species of anglerfish found mostly in the northern Atlantic Ocean and the Mediterranean Sea.. They are found along the coast of Greenland and the entirety of Iceland. The northernmost extent of the range is the tip of Norway and continues south along the entirety of the United Kingdom. They continue eastward as far as Turkey and then around the coast of western Africa as far south as Namibia. [Source: Kristen Coleman, Animal Diversity Web (ADW)]

The larvae transition from shallow water to living at greater depths. Hislop et al. (2001) state that the post-larval stage for anglerfish is a short pelagic stage and growth is rapid, while Ellis et al. (2012) report a prolonged pelagic existence. Juvenile anglerfish have been seen at depths of 10-500 meters, but habitat information beyond this is scant. Adults have been observed at depths close to 1000 meters to spawn.

Anglerfish Physical Characteristics

Adult anglerfish typically have body lengths of 35 to 100 centimeters (13.78 to 39 inches). Female anglerfish live longer and have greater size than males. The mean lengths at sexual maturity was 73 centimeters (28.7 inches) for females (at age 14) and 49 centimeters (19.3 inches) for males (at age 6). A male anglerfish measuring 200 centimeters in length has been reported. Another individual weighing 57.7 kilograms has also been reported. [Source: Kristen Coleman, Animal Diversity Web (ADW)]

Adults have scaleless, very thin, flat bodies to help them blend with the sand or mud where they life in wait for prey. Both male and females have wide mouths with sharp teeth and a fleshy growth, the illicium, that extends from the ventral region of their head extending towards the anterior of their face and is used as bait to lure their prey.

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Species of the genus Lophius have some of the slowest ventilatory cycles in fishes that last more than 90 seconds. They have a large gill chamber, supported by long branchiostegal rays and ending in a siphon-like gill opening positioned underneath and behind the base of the pectoral fin. Lophius do not use their jaw, suspensorium or gill cover during ventilation. When anglerfish are disturbed from the sediment, they have been reported to breathe more rapidly.

Anglerfish have a lateral line system that help them sense their environment through water pressure and vibrations. The lateral line is visible as a line along the middle of their body. Anglerfish also have chemosensory structures such as taste buds, free nerve endings and solitary chemosensory cells, which resemble taste buds.

Anglerfish Behavior

Anglerfish are sit-and-wait-predators. They move very little and it has been deduced that they depend on tactile responses to feed, if the lure functions successfully.

Monkfish are more active during the day. They coexist with another species of anglerfish, Lophius budegassa, black anglerfish, which are active at night. It's suspected they hold these different activity cycles to avoid niche overlap. [Source: Kristen Coleman, Animal Diversity Web (ADW)]

Home ranges have not been reported for anglerfish. They are suspected of moving both as juveniles and adults for spawning, feeding, and following thermal preferences. They are not believed to hold and maintain territories. Some species of the genus Lophius travel long distances.A juvenile female anglerfish was recorded to have traveled 876 kilometers. Anglerfish can also move vertically at all ages up and down the water column— moving from the ocean floor to the surface. The reason for this movement is unknown, but it could be for spawning or feeding. They've been known to spawn as deep at 1000 meters. The newly-hatched young are believed to live a pelagic lifestyle for about 4 months before moving to areas with a firm surface on which the fish can settle.

Anglerfish Food and Feeding Habits

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According to Animal Diversity Web: Anglerfish use a sit-and-wait strategy for feeding. Their illicium, that extends from their head, is used to lure their prey. Like other members of the family, feeding efforts are size-specific, with larger anglerfish consuming larger prey. Generally, the young focus on consuming invertebrates (especially crustaceans and cephalopods). As the juveniles age, they switch from invertebrates to eating fish, comsumed opportunistically. [Source: Kristen Coleman, Animal Diversity Web (ADW)]

Farina et al. (2008) summarized the main diets of larger, adult anglerfish across their range: Norway pout (Trisopterus esmarkii) and blue whiting (Micromesistius poutassou) are main prey in European waters; whiting (Merlangius merlangus) and Norway lobster (Nephrops norvegicus) in the Irish Sea; lesser sandeel (Ammodytes marinus) at Shetland Islands; cephalopods in the Cantabrian Sea. Additional species reported as prey are sea-birds and Atlantic cod Gadus morhua.

There are many cases of anglerfish being found with empty stomachs, suggesting they do not feed often. Some authors have reported higher rates of feeding in fall and winter months.

Anglerfish Reproduction

Male anglerfish testes are generally mature year-round while female ovaries produce eggs only a ceratin time of the year, for example from November to May in the North Atlantic Ocean. A male anglerfish testis is tubular and extends across in a bean shape, located in the dorsal abdomen. As for females, their tubes merge and meet in the middle to form a single flat tube. [Source: Kristen Coleman, Animal Diversity Web (ADW)]

Mating systems in anglerfish are not well-described. Anglerfish spawn at different times, depending on geographic location. Three separate articles list different but overlapping spawning seasons: November-May, January-June, and May-June. [Source: Kristen Coleman, Animal Diversity Web (ADW)]

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Fertilization among some species of anglerfish, like most fish, is external. Females of these species only mate once a season, but it's unknown if males mate with multiple females. The breeding season varies by geographic location — three separate articles report differeing but overlapping mating seasons as November to May, January to June, and May to June. Females breed just once per year. During the breeding season, it was discovered that there was more mature male anglerfish than mature female anglerfish.

Some species of anglerfish fuse together to reproduce (See Below). For some this attachment is temporary. In others, it is permanent: the skin tissues of the two fish fuse and eventually their circulatory systems connect, and the male becomes dependent on its mate for nutrients.

Kiss of Death Anglerfish Reproduction

Among certain species of anglerfish, the males are a fraction of the size of the females and their only goal in life is to mate and have the life sucked out of them. While swimming free the males hardly develop. If all goes well the tiny males attach themselves to the bodies of the much large females.

When encountering a female a young male clamps onto an area near the female’s genital opening with his jaws. The male then slowly degenerates and his blood system becomes united with the female’s. The male does even need to eat. His brain and other organs break down and are absorbed into the female’s body. After a male dies it decays, leaving behind its still-potent sex organs which the female can tap anytime to fertilize her eggs for the rest of her life..

Katherine J. Wu and Rachael Lallensack wrote in Smithsonian magazine :Among “the sea devil (Ceratiidae) family, males are little more than sperm sacs with nostrils. Born into a world of darkness, they sniff and strain to fulfill their only life goal: find and mate with a female, detectable by a potent combination of pheromones and her species-specific glow. In some cases, the males are so poorly developed that they lack even a fully functional digestive system. Up to 99 percent of these unfortunate suitors die as starving virgins. [Source: Katherine J. Wu , Rachael Lallensack, Smithsonianmag.com, February 14, 2020]

“The other one percent don’t fare much better. Once a male locates a female, he’ll press his mouth to her flank and begin to disintegrate, fusing the pair’s flesh together. The male’s organs melt away until all that remains is little more than a pair of testes with gills. Some females can carry upwards of six males on their bodies at once, dipping into their sperm at will.

Anglerfish Eggs and Development

Fertilized anglerfish eggs are buoyant and are often stuck together in the form of a translucent ribbon that can be more than 10 meters long and 25centimeters wide. The number of offspring is unknown but female anglerfish release between 300,000 to 2.8 million eggs. Time to hatching has been estimated at 3 weeks at 7 degrees C, but can be sped up in warm waters. The growth rate of young anglerfish was estimated at 13.6 millimeters per year.

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According to Animal Diversity Web: There is be no known reported parental involvement in Anglerfish. The eggs are kept in a protective gelatinous coating that is translucent and may be toxic or distasteful to predators. The coating could also reduce or even eliminate olfactory cues so it does not bring in predators. Given the lack of parental investment beyond spawning, time of independence is immediate.

Laurenson (2006) collected a ribbon of more than 50 fertilized eggs and allowed them to continue growing in a laboratory environment for about a week. The rate of development, moving from "stages 12 to 14" at a temperature of 7 degrees C, was reported as 120 hours. At this pace, it was suggested that eggs can complete their development cycles in 3 weeks. At warmer temperatures, this development rate increased (such as, 27 hours to complete the same cycles listed above, at 20 degrees C). Eggs size was 2-3 millimeters , on average.

Strange Immune System of Anglerfish

Anglerfish have unusual ways of mating and catching prey and they also have and an unusual immune system. Donna Lu wrote in New Scientist: We now know how the fish can fuse tissues without triggering a potent immune response. They have a strange immune system. In all other vertebrate species, the fusion of tissues would trigger a significant immune response, because an animal’s immune system attacks cells it recognises as foreign — the reason why people have to take immunosuppressive drugs after receiving an organ transplant. [Source: Donna Lu, New Scientist, July 30, 2020

By analysing the DNA of 31 anglerfish specimens from 10 species, Thomas Boehm at the Max Planck Institute of Immunobiology and Epigenetics in Freiburg, Germany, and his colleagues found that fusing anglerfish species are missing key immune system genes. All other vertebrates have some form of adaptive immunity, in which white blood cells known as T-cells and B-cells protect the body by recognising foreign pathogens and producing specific antibodies against them. “Patients with defects in adaptive immunity are very poorly,” says Boehm. But the anglerfish seem to have traded adaptive immunity for reproductive success without severe consequences.

Species with temporarily attaching males didn’t have functional aicda genes, which are needed for antibodies to mature. Permanently attaching species also had non-functioning rag genes, which are needed to assemble T-cell receptors. The deep sea isn’t entirely devoid of pathogens, so how the anglerfish are able to defend themselves from infection remains a mystery, says Boehm.

Anglerfish Fishing and Human Consumption

Kristen Coleman wrote in Animal Diversity Web: Humans are the main predator of anglerfish. They fish for them and once caught they are sold in markets as food in European and Asian countries, often without the skin or head.. They are marketed fresh and frozen. They can be steamed, sauteed, broiled, boiled, fried, microwaved and baked. The name for anglerfish as food in French is "Queue de Lotte." There have also been reports of harbor seals breaking into nets to eat anglerfish. Cannibalism occurs but it is rare. [Source: Kristen Coleman, Animal Diversity Web (ADW)]

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Anglerfish are usually caught using trawling and gillnets. Farina et al. (2008) reported that this species, along with two others in the genus (Lophius americanus and Lophius vomerinus) were harvested at a rate of more than 100,000 tons (90,718,474 kilograms) in 2007.

The conservation status of anglerfish is "Least Concern" on the International Union for Conservation of Nature (IUCN) Red List. Anglerfish have no special status on the US federal list, Convention on International Trade in Endangered Species (CITES). The International Council for the Exploration of the Sea. (ICES )has been trying to regulate overfishing by providing fishermen with maps that show the most suitable areas for fishing. They have also been trying to regulate fishing. Since 1997, they have been attempting to reduce the number of anglerfish caught by informing the public to limit the amount they can catch. But by 2000, they advised that there should be a 40 percent reduction in catches and by 2001 it was moved to a 2/3 reduction.

Sustainable fishing is now maintained by a few methods: limiting total allowable catch (TAC), limiting effort control, implementing mesh size restrictions, and making sure that fishing for them is closed for some seasons. Still, there have been reports of over-fishing and habitat destruction due to the decline in catches in recent years.

Anglerfish Dishes in Japan

“Anko”, or anglerfish, is prized as an ingredient in “nabe” stews, particularly in eastern Japan. Hirakata, a port north of Tokyo in Ibaraki Prefecture, is regarded as the center of anko fishing. In the waters off the town, where the Oyoshio and Kuroshio currents collide, there are abundant supplies of small fish for the large-mouthed anglerfish to eat.

Anglerfish prized in Japan as food include “kianko”, a yellow goosefish species, prized for its liver, and “ankimo”, known as foie grass of the sea. When kianko are put up for auction they displayed upside-down so buyers can check out their livers.

Among the first people to embrace anglerfish as a food were Japanese fishermen who ate it at sea, where fresh water is in short supply, because anglerfish could be prepared without water as 80 percent of the fish’s body is water. Later the dish caught on with locals in fishing villages and then among tourists. One of the most popular anko dishes is “dobu-jiru”, which is made using all parts of the fish’skin, fins, ovaries, stomach, gills, liver — and uses only miso and dry-fried liver as seasoning.

Anglerfish are often cut outside while hanging from a hook. Their bodies are covered in mucous membranes called “noro”, which make the fish difficult to slice on a cutting board. When cooked as nabe the dish takes on an orange color as a result of orange fat oozing from the liver.

Monkfish

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Monkfish is the name are various species of lophiid anglerfishes found in the Atlantic and Indian Oceans. Members of the genus Lophius, they sometimes called monkfish, fishing-frogs, frog-fish, and sea-devils. They look ugly but taste good. The mostly fished and eaten monkfish in the U.S. is the American angler (Scientific name: Lophius americanus). Also known as goosefish, monktails, angler, allmouth, molligut, abbot and lotte, they have mottled dark brown to olive-green skin on top and whitish skin underneath. They are described as tadpole-like in appearance, with a body that is mostly a broad head with a large mouth and a narrow, tapering body. [Source: NOAA]

Female monkfish grow larger and live longer than male monkfish. Females live to at least 13 years and grow to more than ( one and half meters (4½ feet long), while males only live about 7 years and grow to almost one meter (3 feet) long. Males and females are able to reproduce when they reach about 35 centimeters (14 inches) and 41 centimeters (16 inches long), respectively.

Monkfish migrate seasonally to spawn and feed. They travel by slowly swimming or by using the sturdy base of their pectoral fins to walk. Scientists speculate that their wing-like pectoral fins may be used to ride currents. Monkfish spawn from February to October. Females release large egg veils that can contain more than 1 million eggs. These egg veils float near the surface along with the prevailing currents for 1 to 3 weeks (depending on temperature) until the veil disintegrates and the larvae hatch.

Monkfish are opportunistic feeders, eating whatever prey is most available at the time. Larvae feed on zooplankton (tiny floating animals). Juveniles mostly eat small fish, shrimp, and squid. Adults mainly eat fish, including other monkfish, but also feed on crustaceans, mollusks, seabirds, and diving ducks. Monkfish ambush their prey — they use a modified spine on their head as a fishing pole and bait to lure small fish toward their mouths. When the prey comes near, the monkfish takes a large gulp, which sucks the prey into its mouth and traps it behind rows of back-pointing teeth. Large monkfish have few predators. Predacious fish such as swordfish, sharks, and thorny skate prey on small monkfish..

Monkfish are found in the Northwest Atlantic Ocean. In the U.S. they can be found off New England and Mid-Atlantic, Southeast from the Grand Banks and northern Gulf of St. Lawrence south to Cape Hatteras, North Carolina. They can tolerate a wide range of temperatures and depths, from inshore waters down to nearly 1,000 meters (3,300 feet). Monkfish live on the ocean floor, typically on sand, mud, and shell habitats. Adults spend most of their time on the bottom, often in a depression or partially covered in sediment. They also spend some time off the bottom, probably riding currents to help with migration..

Monkfish Fishing

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In 2021, the commercial landings in the U.S. of monkfish totaled 6.6 million kilograms (15 million pounds) and were valued at $10 million, according to the NOAA Fisheries commercial fishing landings database. Monkfish is one of the highest valued finfish in the Northeast. Almost all of the monkfish for sale in the United States comes from U.S. fisheries. Fishermen harvest monkfish using bottom trawls, sink gillnets, and scallop dredges. [Source: NOAA]

There are two stocks of monkfish in U.S. waters: 1) Gulf of Maine- Northern Georges Bank and 2) Southern Georges Bank-Mid-Atlantic. According to the most recent stock assessments these stocks are not overfished and not subject to overfishing (2013 stock assessment). Most monkfish in these two stocks are caught by vessels using bottom-trawl gear targeting groundfish. Although bottom trawls can affect marine habitat, most bottom trawls catch monkfish over sand and mud habitats, which tend to recover from any disturbance more quickly than more structured habitats.

The commercial monkfish fishery in the U.S. operates from Maine to North Carolina out to the continental margin. Trawl gear is primarily used in northern waters, and gillnet gear in southern waters. It is common for monkfish to be caught in conjunction with groundfish. The monkfish fishery is managed using a days-at-sea and trip limit management system. There is no known directed recreational fishery for monkfish. The market for monkfish is for human consumption. U.S. wild-caught monkfish is a smart seafood choice because it is sustainably managed and responsibly harvested under U.S. regulations. There are above target population levels. The fishing rate is at recommended levels. Area closures and gear restrictions protect habitat affected by some kinds of trawl gear. Regulations limit possession of bycatch species and require modified fishing gear to reduce bycatch.

NOAA Fisheries and the New England and Mid-Atlantic Fishery Management Councils manage the U.S. monkfish fishery. Management measures include annual catch limits, limited access permits, size limits, landing limits, and measures to reduce bycatch and impacts on habitat. Managers and researchers believe that monkfish essential fish habitat is only minimally vulnerable to the effects of bottom trawls and sink gillnet gear. Managers have implemented a variety of measures to protect habitat of other bottom-dwelling fish from any potential impacts from the monkfish fishery: 1) Two areas are closed to monkfish fishing (all gears) year-round to protect sensitive habitat. 2) Fishermen must use gear with specific requirements that prevent them from fishing in sensitive hard bottom areas.

Monkfish fisheries sometimes incidentally catch spiny dogfish and skates, which fishermen are allowed to keep as long as they have the appropriate federal permits and comply with the appropriate regulations for these fisheries. There is a limit on the amount of bycatch of other fish species allowed in the monkfish fishery, including possession and landing limits and annual quotas specified in fisheries for those species. Mesh on gillnets and trawl nets must be larger than the established minimum size to reduce bycatch.

Gillnets used to target monkfish can incidentally capture protected species, such as sea turtles, large whales (right, humpback, and fin whales), harbor porpoise, dolphins, and Atlantic sturgeon. Monkfish fishermen follow a number of measures to reduce the fishery’s potential impact on protected species: In the Mid-Atlantic, management measures prohibit gillnet vessels from using large mesh (18 centimeters, 7 inches or greater) gillnets in some areas during certain times of the year to protect migrating sea turtles. Closures are timed based on projected sea surface temperatures in fishing areas, as sea turtles are known to migrate into these areas when temperatures are about 11̊C (52̊F) or higher. The closures move large-mesh gillnetting north in advance of sea turtles migrating into fishing areas and, along with other precautions, have greatly reduced incidental catch of sea turtles in the monkfish fishery.

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Image Sources: Wikimedia Commons; YouTube, Animal Diversity Web, NOAA

Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated March 2023

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