Meet One of the Most Venomous Fish on Earth:
Stonefish

Stonefish are the masters of disguise and a sting caused by these fish is able to produce extreme pain to humans. In some cases, it is potentially fatal.

Despite their potent venom, they are considered a delicacy in some Asian regions, if well prepared. Stonefish sit still near rocks and corals, or bury themselves in the sand, which allows them to take their camouflage to the next level.

Stonefish biology and behaviors

Stonefish size varies according the species. In average, they have a length of 30 to 40 centimeters, and they can weight up to 2kg. Their warty, scaleless skin along with their colors enable them to perfectly blend in with the surroundings. They have a large mouth and powerful jaws. In addition, stonefish have a raised bony structure on their head, with two small eyes.

Approximately 1200 species of fish are thought to be venomous, but stonefish are among the most lethal. Their dorsal fin has 13 short, thick spines that are raised when these fish feel threatened. They have the most advanced venom apparatus, composed of two bulky glands on the sides of each dorsal spine. The venom is composed of neurotoxins and is released when pressure is put on the spine.

The amount of venom released is equivalent to the pressure applied in the spines. It is used as a defense mechanism against predators. Moreover, they have two pelvic and three anal spines.

Recently, researchers discovered that stonefish have a “lachrymal sabre” or, in other words, a switchblade beneath each eye. Even though it isn’t connected to venom, this sabre is considered an additional defensive mechanism. To deploy it, the stonefish only have to squeeze the cheeks muscles. Furthermore, the sabre glows which means it can be used for mating or territory defense.

There are five species of stonefish: some of them are marine, others are estuarine. They usually live alone, and are sedentary animals that can be found at depths of 40 meters. They typically sit still near rocks and corals, or bury themselves in the sand, which allows them to take their camouflage to the next level. Sometimes it is possible to see organisms growing at their surface. Interestingly, stonefish can as well live out of the water for up to 24 hours.

Reproduction and life cycle

Stonefish have oviparous reproduction. Female stonefish release around a million eggs on the bottom of the sea floor, whereas the males release the sperm that will further fertilize them. When they hatch, newborn stonefish are already well developed.

Even though the females lay a huge amount of eggs, a great percentage of them is eaten by other aquatic organisms. Only a small number survives and reaches maturity. In the wild, a stonefish can live up to 10 years.

“Stonefish are abundant around the tropical waters of Indian and Pacific Oceans as well as in the Red Sea.

Where are stonefish found?

They are abundant around the tropical waters of Indian and Pacific Oceans as well as in the Red Sea. Stonefish can be found in coastal waters and even lying on beaches. Because of this, people should have extra precaution when walking on beaches of coastal regions where they are present.

What do they eat? And who eats them?

Stonefish usually feed on other fish and invertebrates, that are frequently swallowed whole. They don’t hunt or use their venomous spines to catch their prey. Instead, they remain motionless till a prey approaches. Then, vacuum is created by expanding the oral cavity, and they suck in their prey in less than 0.01 seconds.

On the other hand, the main predators of stonefish are sea snakes, moray eels, sharks and rays.

Red Stonefish sit still waiting for a prey. They remain motionless till a prey approaches.

Do stonefish sting humans?

Yes! In fact, a sting from stonefish is incredibly painful and symptoms may persist for days. The main symptoms caused by the neurotoxins of the venom are nausea, vomiting, local swelling, discoloration, sweating, cardiac arrythmias, respiratory distress, convulsions and necrosis. In more extreme cases, the damages are so severe that people die.

At a hospital in Pulau Bukom, an island near Singapore, 81 cases of stonefish stings were documented over a period of 4 years.

How to treat a sting from stonefish? And how to avoid it?

In order to treat a sting from stonefish, the spines and membranes must be carefully removed from the skin. It is suggested that hot water at 45ºC helps relief the pain. If a stonefish stings you, you should go to the hospital because you might need the antivenom. Only one is commercially available that neutralizes stonefish venom.

To prepare it, it is necessary to milk the fish by collecting some venom from the spines.

The wounds usually occur on the sole of the foot. Therefore, to avoid a painful sting from these fish, bathers should use footwear and adopt a shuffling gait.

A sting from stonefish is incredibly painful and symptoms may persist for days.

Main threats and conservation status

These outstanding animals are not a fisheries target and are rarely eaten by people. However, they are considered a delicacy in some Asian regions, such as south Japan, Hong Kong, Guangdong and Fujian. Their dorsal fin is removed because of the venom and they are served raw as sashimi. It is found in some local markets and is a food supply in subsistence fisheries.

It is suggested that the destruction and degradation of stonefish habitats, especially corals, due to human activities, might be causing localized population declines. Despite this, stonefish populations are generally stable, and IUCN finds that their conservation status is of least concern.

Australian Aboriginal communities

Curiously, Australian Aborigines performed a dance ritual that represented the pain caused by stonefish stings. The goal was to teach other people about the danger associated with the fish.