Venomous Reef Fish: Scorpionfish, Stonefish and Stargazers

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Poisonous marine creatures like lionfish, stone fish and sea snakes are basically gentle and only attack if provoked. Though venom has evolved 18 separate times in 2,500 venomous fish species, fish venom is understudied, Leo Smith, an associate professor of ecology and evolutionary biology at the University of Kansas, told the New York Times.

Worldwide, scorpionfishes (a taxonomic order that includes scorpionfish, stonefish and lionfish) rank second only to stingrays in total number of human envenomations by fish species. Puncture wounds from lionfish species' spines can cause extreme pain, potentially lasting for days, accompanied by sweating and breathing difficulties. Experiments suggests that stonefish antivenom may also work on lionfish venom.

Scuba divers generally approach poisonous sea creatures with little to fear. Reports of attacks by poisonous fish are rare but they do occur. In September 1998, an 18-year-old man died after apparently being bitten by a fish or sea snake while snorkelling off Majorca during a catamaran trip. He was pulled back on to the boat after his girlfriend raised the alarm and began foaming at the mouth as he was taken by speedboat to a nearby jetty. [Source: Daniel Waddell. Electronic Telegraph]

Staff from a local medical center attempted to revive him with heart massage. A friend who was on the trip, said: "It was very distressing. His girlfriend was on the jetty with him, and when the doctors stopped the massage, she let out a howling wail. It was awful." One person on the boat said that a snake was responsible, but a description given by crew members to a marine expert in Palma pointed to a spider fish. Their bite is normally not fatal, but there could have been an allergic reaction.

Websites and Resources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Fishbase ; Encyclopedia of Life ; Smithsonian Oceans Portal ; Woods Hole Oceanographic Institute ; Cousteau Society ; Monterey Bay Aquarium ; MarineBio


20110307-NOAA  scorpionfish_100.jpg
The scorpionfish family counts 300 members around the world, including feathery lionfish, bottom dwelling scorpionfish, and stonefish, the world's most venomous fish. Stonefish and scorpionfish venom is very poisonous. Stings are extremely painful and can cause death. There is an antivenin. [Source: David Doubilet, National Geographic, November 1987 ┭]

Scorpion fish spend most of their life sitting motionless on the sea floor, half buried in the sand, waiting patiently for food — small fish, crustaceans and even other scorpionfish — to come their way. When one does the well camouflaged fish gulps its victim down in one lightning quick bite. Scorpionfish have leglike pectoral fins which allow it to walk along the sea floor. When the predator swims bright colors are revealed behind backside of the fins, which are normally hidden. The bright colors may be a warning to other predators that the scorpionfish's dorsal spines are venomous.┭

"I stared at the rocky bottom, and the rocky bottom stared back" is how diver and photographer David Doubilet described an encounter with a scorpionfish. Even then it wasn't until later that he realized the rock next to scorpionfish he saw was in fact another scorpionfish.┭


Stonefish are the world's most venomous fish. They are also amazingly well camouflaged. Some species look like small boulders covered with red and green algae, and even if you are looking straight at one it is difficult to make out were the mouth and eyes are and tell the front of the fish from the back. Spines on the fishes back contain a powerful venom. Always make sure you have on a pair of foot-covering flippers if you are anywhere in a place with stone fish because the way most people are stung is by steeping on one. [Source: David Doubilet, National Geographic, November 1987 ┭]

Stonefish are found through the South Pacific and Indian Oceans. The sting causes extreme pain and rapid paralysis, but is rarely fatal. If stung by a stonefish, immerse your foot in hot water to relieve the pain.

Stonefish have venom on each of their thirteen spines. "The sting is so excruciating," says Doubilet, "that people have begged for death and sometimes gotten their wish...The pressure of a victim's hand foot or hand on a dorsal spine pushes back a fleshy sheath containing venom glands, squeezing venom up two grooves on the needle-sharp spine. In a sense the victim shoots itself. Even the sting of a dead stonefish can be disabling.” An antivenin developed in Australia is effective against several bit all of the stonefish species. ┭

A stonefish's pink skin, which is also venomous, hosts tiny worms, crustaceans and algae (the source of the green on the fish's skin). Periodically the stonefish gets rid of these encrustation apparently by injecting them with poison. The only sea creatures known to feed on stonefish are sea snakes.┭


Frogfish, a member of the stonefish family, are brilliant masters of disguise in brilliantly colored coral gardens. They come in a dazzling array of colors — orange with brown stripes, yellow with red markings and splotches like on an algae-covered rock — and are covered with feathery ghoul-like appendages that make them easy to confuse with a piece or coral or a sea anemone. [Source: Fred Bavendam, National Geographic, July 1998]

Hanging from their mouth, frogfish have an appendage with a worm-like piece of flesh that is used to lure prey. Like stonefish and stargazers frogfish find a nice cozy place to hide themselves and wait for prey to come their way, attracted by the lure. As prey approaches, the frogfish snatches it in one-sixth thousandth of a second with its mouth. It has the fastest "gape and suck" of any fish — so fast fish around the prey often don’t realize anything has happened.

Frogfish are found in seas throughout the world but they more common in the coral reefs off Indonesia and Australian, particularly in northern Sulawesi's Lembeh Strait and near Edithburgh, Australia. Frogfish are such master of disguise that scientists have a hard time finding them. Sometimes they also have a hard time identifying them. Some species look almost the same expect they come in different colors. Others can change color in a few day or minutes. Forty-one frogfish species had been recognized as of the late 1990s.

Some frogfish species are better suited for crawling along the ocean floor than swimming. When approached by potential predators, a frogfish can open its mouth wide to make it appear large than it is. It can also enlarge its mouth to suck down prey twice its size.

Female frogfish lay thousands of eggs, which are fertilized outside her body by a male’s sperm. The males sometimes picks up the eggs deposited by the female and blows them from his mouth along with bubbles of mucus. The mucus hardens around the egg mass and creates a light floating bag. The eggs sink to the bottom when the embryos hatch.

Stargazers — Ugly, Venomous, Electric Fish

Stargazers resemble flattened stone fish. There are 50 different species of them and they are widely distributed in tropical and temperate waters in the Pacific, from the Americas to Southeast Asia. They are called stargazers because both eyes on the top of their flat bodies appear to be gazing up at the stars.

Stargazers belong to the genera Astroscopus and Uranoscopus. They have a pair of poison dorsal spines and have electric organs behind their eyes which give off a 50 volt jolt. Stargazers are ambush predators that spend most of their time lying time burrowed into the sand and mud surfaces of the continental shelf and upper slopes.Ichthyologist Dr. William Leo Smith of the University of Kansas playfully called them "the meanest things in creation."

The Atlantic Stargazer (Scientific name: Uranoscopus scaber) is widely distributed along marine waters of the Atlantic coast of Europe to Portugal, the Gulf of Guinea, the Black Sea, the Red Sea, the Mediterranean Sea, along the northern coast of Africa. It is a benthic (living on or near the bottom of the sea) species and is typically found in warm, subtropical waters at depths of 15 to 400 meters (40 to 1300 feet). Studies of their lifespan suggest they do not live longer than six years. [Source: Alex Letulle, Animal Diversity Web (ADW) /=]

Stargazers are a delicacy in some cultures (the venom is not poisonous when eaten), and they can be found for sale in some fish markets with the electric organ removed. The Atlantic Stargazer is not commercially important in the Eastern Mediterranean Sea, while it makes up 2.6 percent of total caught fish by trawls in the Western Mediterranean. The only recorded natural predators of the Atlantic stargazer are bottlenose dolphins but they are often caught as bycatch in gillnets. Studies show that Atlantic stargazer has a low exploitation rate, even in comparison to other bottom dwelling fish in the area, therefore, it is assessed as a species of “Least Concern” by the International Union for Conservation of Nature (IUCN) Red List with no plans to manage the species in place. [Source: Wikipedia]

Stargazer Characteristics, Behavior and Reproduction

The Atlantic stargazer reaches lengths of 30 centimeters (12 inches), with their average length being 25 centimeters (10 inches). Females are larger than males. According to Animal Diversity Web: Atlantic Stargazers and other members of Uranoscopus are easily recognized by a large, dorsally-flattened and square head with dorsolaterally placed eye. A protractible and tooth-filled mouth opens vertically with the lower jaw extending past the upper jaw. The lower mandible possesses unique processes such as tiny sensory appendages called cutaneous cirri that line the bottom lip and a long, slender outgrowth of the oral valve at least as long as eye diameter. A poisonous cleithral spine four times the head length located dorsoposterior to the gill cover. [Source: Alex Letulle, Animal Diversity Web (ADW) /=]

Northern stargazer
Long, somewhat compressed body extending posteriorly from the broader head with two dorsal fins and an anal fin; the first dorsal fin has three to 4 spines, the second dorsal fin has 13 to 15 soft ray, and the anal fin has one spine and 12 to 14 soft rays. The Atlantic stargazer has a white mottled greyish-brown dorsal and lateral scales with a yellowish underside. Average size of the

Stargazer sense using touch and chemicals usually detected with smell. Being nocturnal (active at night), predators, the Atlantic Stargazer spends much of the day motionlessly buried in the sand or mud and are more active at night. The stargazer leaves only the eyes and mouth above the sand and lie in wait for small fish, yet are known to react to inanimate objects such as rocks and trash. For reasons that still remain unknown, studies consistently report Atlantic Stargazer and a species of Mediterranean Sea croaker, Sciaena umbra, to congregate in clusters.

Atlantic stargazers migrate to more open waters during a spawning period from March to September with a peak in May. As the length and weight of the female Atlantic Stargazer increases, so does the amount of viable eggs produced during the spawning period. The pelagic (living in the open ocean, far from land) eggs range from 0.62 millimeters up to a maximum of 1.86 millimeters after fertilization. The individuals inhabit pelagic (living in the open ocean, far from land) waters throughout larval, post larval and juvenile stages. (Coker, et al., 2008) /=\

Stargazer Poison and Electricity

Stargazers have a pair of poison dorsal spines which provide protection from predators. Some species have electric organs behind their eyes which give off a 50 volt jolt. Although less powerful than the charge of an electric eel, which are capable of producing up to 500 volts, more than enough to kill a horse, or an African electric catfish, the jolt is powerful enough to stun prey or give a powerful jolt to a careless diver who makes the mistake of picking one up.

According to Siladen Resort; The primary defense technique of a stargazer is to simply bury itself deeper into the sand and completely cover itself until the threat has passed. If that is not possible, they will flee, using their other, more deadly defence mechanisms. Although their venom wont kill you, it can be extremely painful, and will cause localised swelling and can induce shock.[Source: Siladen Resort

Perhaps more impressive, is there third method of defence, electricity. Although electrical discharge is not unique to stargazers, they are unique as they are the only electric fish that do not have specialised electroreceptors. This electrical defence comes from modified muscle tissues known as â sonic musclesâ , that are located just behind the eyes. This is used as a defence mechanism while they are swimming in the open.

Astroscopus species have a single electric organ consisting of modified eye muscles, while Uranoscopus species have theirs derived from sonic muscles. These two genera within stargazers represent one of eight independent evolutions of bioelectrogenesis. Stargazer's paired electric organs are aligned vertically inside the head. [Source: Wikipedia]

Stargazer Hunting

Stargazers spend most of their time lying buried in the sand, with only their eyes and mouth exposed, waiting for fish to come with range and then gulp it down with its lightning quick oversize mouth. Describing a stargazer attack of small fish, photographer Mike Severns wrote in Natural History, "It exploded from the sand, leaving a thick cloud of silt hovering in the water. Then it promptly retreated to the bottom and reburied itself. “

The Atlantic Stargazer buries itself and waits for prey to come within a certain distance before attacking. According to Animal Diversity Web: The protractible appendage of the mouth is used as a lure to attract small fish by waving it around. The major prey of the Atlantic stargazer are small teleosts with a contributing diet of crustaceans, molluscs, echinoderms, and annelids. The Atlantic Stargazer shows an increased feeding activity during the Fall which decreases until it reaches a low in the Summer.

It was thought that stargazers used their electricity shocks to immobilize passing fish with an electric shock A shock from a stargazer can be painful and stunning however a fish would have to physically touch the stargazer to receive any shock.

Prehistoric Stargazers Found with Feces in Their Skull

Stargazer (Uranoscopus sulphureus) in the sands of the Lembah Strait in Indonesia

A stargazer fossil from the Miocene Period (23 million to 5.3 million years ago) was found with hundreds of tiny fossilized fecal pellets filling its skulls, believed to have been put their by worms scavenging its brain. Live Science reported: In a first for paleontology, scientists have found hundreds of tiny, fossilized fecal pellets crammed inside a fish braincase dating to about 9 million years ago. The wee fossil poops, also known as coprolites, were deposited by scavengers — probably worms — that devoured the fish's decaying head, including its brain. [Source: Mindy Weisberger, Live Science published February 01, 2022

“As they munched the flesh from the skull, the worms pooped out chains and clusters of oval coprolite beads, each measuring about 0.1 inches (2.5 millimeters) long. Small as they were, those pellets added up over time. When the hungry scavengers were done, they had left behind hundreds of pellets — enough poop to fill the fish's braincase entirely.

Researchers found the coprolite-filled fossil at Calvert Cliffs, a site in southern Maryland that contains fossils dating from about 18 million to 8 million years ago, during the Miocene epoch. The skull belonged to the fish Astroscopus countermani, a type of bottom-dwelling ambush predator commonly known as a stargazer, and small, oblong coprolite pellets such as these are known collectively as Coprulus oblongus. In addition to the fecal-stuffed skull, the scientists also examined other coprolite pellet deposits that were clustered in sandy sediments, stuck to fossilized snail and bivalve shells, and grouped around preserved barnacles at the site.

Bearded Ghoul

The bearded ghoul(Scientific name: Inimicus didactylus) is a venomous fish also known as the Popeyed sea goblin. They are typically found at depths of five to 450 meters (16.40 to 1476.38 feet), often in brackish water, and are widely distributed in the eastern Indian and western Pacific oceans; and seem to be most common around the Andaman Islands, northern Australia, China, and the Phillipines. This bearded ghoul a benthic species that lives on or near the bottom of the sea and generally occupies moderately deep waters up to 70 meters, and are associated with mangrove swamps and coral reefs. [Source: Tiffany Wu, Animal Diversity Web (ADW) /=]

The bearded ghoul’s genus name — Inimicus — means enemy in Latin. Names of species in this genera include goblinfish, sea goblin, spiny devilfish, stinger, and stingfish. These fish sense using touch and chemicals usually detected with smell. The bearded ghoul flashes the bright undersides of its pectoral fins as a warning to predators when disturbed.

Little is known about the numbers of this species, but it is not generally considered in need of special conservation efforts. This species is not listed in International Union for Conservation of Nature (IUCN)'s Red List and has no special status under the Convention on International Trade in Endangered Species (CITES). It is also commonly caught by prawn trawlers.

Bearded Ghoul Characteristics

pair of beared ghouls

According to Animal Diversity Web: Specialized for its benthic (living on or near the bottom of the sea) habitat, it has two feeler rays on its pectoral fins that probe the seafloor and allow it to "walk" along the bottom. Its eyes and nostrils are located above its dorsal profile as another benthic (living on or near the bottom of the sea) specialization.

The bearded ghoul has an elongated body without scales, with the exception of 13-15 buried in the lateral line. It is covered with skin glands that have the appearance of warts. The range is size from 13 to 20 centimeters (5 to 8 inches) . The species has a depressed head that is strongly concave on the dorsal side. The head is also covered with flaps of skin and raised ridges, and tentacles are present on the head, trunk, and fins. Its mouth points up almost vertically, and its eyes protrude visibly outwards. A raised knob at the end of its snout gives it the appearance of having an upturned nose. /=\

The pectoral fins are large and their coloration is significant in identifying the different species of Inimicus. In Bearded ghoul, the underside of the pectoral fins bears broad dark bands (containing smaller, lighter spots) at the basal and distal ends. The lower two rays of its pectoral fins are free from the rest of the fin and used in "walking" along the bottom. This coloration is not sexually dimorphic. The caudal fin has dark bands at basal and subterminal positions. The dorsal fin is composed of 15 to 17 spines and seven to 9 rays. With the exception of the first 3, the spines are almost entirely incised from membrane.

Bearded ghoul juveniles has distinctive pigmentation on the pectoral fins that appears when the fish have reached a length of about 50 to 60 millimeters. There is little information on the reproductive cycle of this species; however, reef scorpaenids generally lay small (0.7 to 1.2 millimeters) clusters of spherical or slightly ovoid eggs in gelatinous sac-like structures. When larvae hatch, they come equipped with fully developed eyes, range in length from 1.5 to 2.3 millimeters, and have large yolk sacs. As the larvae develop further, they take on the characteristics of two general morphs: preflexion and postflexion. The former is more elongate and slender than the latter with larger development of the pectoral fins.

Bearded Ghoul Venom and Hunting

Bearded ghoul mainly eats fish. It lies partially buried in the seafloor with its eyes protruding above the substrate waiting to ambush smaller fishes. Its natural coloration allows it to blend in with its environment, making it difficult for its prey to see, it. Rows of teeth lining its jaws and vomer (a small, thin, plow-shaped, midline bone that occupies and divides the nasal cavity) allow it to seize prey.

According to Animal Diversity Web: Using its two free pectoral rays, the Bearded ghoul is able to slowly crawl along the seafloor. Coinciding with the method of hide-and-wait hunting typical of Bearded ghoul, members of the family Synancejidae are described as slow and sluggish, spending most of their life buried in mud or concealed in coral reefs.

Like other Synancejidae, Bearded ghoul possesses a powerful venom that is stored in glands at the bases of its dorsal spines that can be injected upon contact. As described above, this species also flashes the undersides of its pectoral fins when disturbed as a warning signal. These, in addition to its natural camouflage, discourage other organisms from feeding on it.

No predators of the bearded ghoul have been observed. Fishermen have traditionally feared them fishes because of their painful, venomous spines. The fish is well concealed, and swimmers or divers may accidentally brush against The bearded ghoul’s complex and extremely potent venom is stored in glands at the bases of needle-like spines in their dorsal fins. Upon contact with the dorsal fin, the fish can deliver a potentially fatal, sting. The venom consists of a mixture of proteolytic enzymes, including stonustoxin (a hemotoxin), trachynilysin (a neurotoxin), and cardioleputin (a cardiotoxin). Despite the obvious risks, one species of Inimicus — I. japonicum — is commercially cultured in Japan as a food. [Source: Wikipedia]

Envenomation (the injection of venom) results severe and immediate local pain, sometimes followed by shock, paralysis, tissue necrosis, and even death. If stung medical aid should be sought immediately. Recommended first aid treatment includes immersion of the affected area in hot water at least 45 °C (113 °F), which. can partially break down the proteolytic enzymes in the venom. Relief from the pain can also be obtained by infiltrating the affected area with a local anesthetic. For more extreme cases, an intramuscular injection of a specific horse-derived antivenom can be lifesaving. Surviving victims often suffer localized tissue necrosis and nerve damage, leading to atrophy of adjoining muscle tissues.

Little Reef Fish With a Vampire-Like, Narcotic Bite

Fang blennies are a family of venomous fish that live in the Pacific and Indian Oceans. Steph Yin wrote in the New York Times: “It’s a small fish, only a couple of inches long, and its bright colors make it pop in the Pacific coral reefs it calls home. The first thing that makes this fish peculiar is the striking pair of large lower canines it sports. [Source: Steph Yin, New York Times March 30, 2017]

“But when attacked by a predator, this fish, part of a group called fang blennies,does something even more strange. A predator that puts this fang blenny in its mouth would experience a “violent quivering of the head,” according to George Losey, a zoologist who observed this species up close in a series of feeding experiments in the 1970s. Then the predator would open its jaws and gills. The little blenny would swim away, unscathed.

“A study published in March, 2017 in Current Biology now lays bare the details of the fish’s unusual defense mechanism: Unlike most venomous fish, which inject toxins through their fins, fang blennies deliver venom through their bite. Furthermore, fang blenny venom does not appear to produce potent pain, at least in mice. Instead, it causes a sudden drop in blood pressure, which might temporarily stupefy predators.

“The authors of the study took a multipronged approach to studying venomous fang blennies. First, they imaged the jaws of fang blennies collected from around the Pacific and Indian Oceans to confirm what scientists long suspected: Not all fang blennies have venom glands at the base of their teeth. Out of 100 fang blenny species, only about 30 are venomous, said Nicholas Casewell, a lecturer at the Liverpool School of Tropical Medicine and an author of the study. This pattern suggests that fang blennies first evolved large teeth, which certain species then coupled with venom.

“Analyzing venom extracted from one fang blenny species, the scientists identified three toxins: an enzyme, a molecule used in neuron signaling and an opioid, in the same class as heroin and some prescription painkillers. Though the toxins have never been reported in fish before, other animals — including snakes, bees, scorpions and cone snails — have independently evolved to use similar ingredients in their venoms, Dr. Casewell said.

“When his team injected small amounts of fang blenny venom into the paws of mice, the mice showed no significant signs of distress. However, their blood pressure plummeted by nearly 40 percent. “If you had such a big crash in blood pressure, you would immediately feel faint and dizzy,” Dr. Casewell said. “We don’t know that fish get faint or dizzy, but it’s extremely likely such a large drop would impact coordination and swimming ability.”

“It’s noteworthy that fang blenny venom does not cause “instant, severe pain, which is a hallmark of other fish venoms,” said Jeremy Wright, an ichthyologist at the New York State Museum. Though it may not be acutely painful, fang blenny venom is unpleasant enough to send a serious message to fish predators. Up to 20 species — some nonvenomous fang blennies and some fish that aren’t blennies at all — copy the bright colors, patterns or cruise-and-dart swimming style of the venomous fang blennies to escape predation themselves. A handful even use mimicry to feast on the scales and skin of larger fish without being eaten.

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

Text Sources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); 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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