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What is a Stonefish?

R. Kayne
R. Kayne

The stonefish is believed to be the most venomous fish in the world, belonging to the genus Synanceia of the Synanceiidae family. It is mainly found in coastal areas within the Indo-Pacific region, comprised of much of the Pacific Ocean, the Indian Ocean, and the Indonesian seas that join them, excluding polar and temperate regions. Habitats are also found off the northern Australian coast. Though considered a marine animal, a few species are known to live in rivers.

The stonefish gets its name from its ability to change its mottled colors in order to camouflage itself among the rocks and coral reefs where it lives. Depending on the species, its body can reach nearly 14 inches (about 35cm) in length. Stonefish have a large, upturned heads and protruding eyes. A stonefish will sit on the sea floor waiting perfectly still for small passing fish and shrimps. When a fish gets close enough, the stonefish lunges with its opened mouth, sucking up its prey and returning to its original position in mere fractions of a second.


To discourage manta rays, sharks and other hunters that scour the seabed and reefs for food, stonefish evolved a deadly defense mechanism. The dorsal fin has thirteen needlelike spines, sharp enough to pierce the sole of a shoe. Glands containing highly toxic venom feed the spines, pumping poison into any animal unlucky enough to be stuck. Once spines have delivered their noxious toxin, glands must regenerate over the course of the next several days before becoming fully charged.

A sting from a stonefish creates excruciating pain accompanied by rapid swelling and necrosis at the sting site. The extent of injury depends upon the number of spines involved, depth of the wounds, and the amount of toxin delivered. The venom attacks the muscles, potentially affecting the respiratory system and heart. Local paralysis, difficulty breathing and shock can result. Death can occur within 48 hours. However, a sting is treatable, with quick treatment being the most effective course.

According to publicly available medical information, immediately following a stonefish sting the victim should remain calm, lay down, and elevate the injured body part — most likely the foot or leg — so that it remains higher than the rest of the body. The injured area should be immersed in water as hot as comfortably tolerable, and immediate arrangements should be made to transport the victim to a medical care facility to receive anti-venom and any other appropriate treatment. Recovery can take a few days, depending on the severity of the sting.

If it is necessary to walk in shallows where a stonefish might be present, reef sandals are recommended or other protective shoes of equal quality. Slowly shuffling the feet forward through the sand might scare a nearby animal away, rather than lifting the feet and accidentally stepping down on a spine. When possible, swimming is preferable over shuffling as this will not only lessen the possibility of contact with a stonefish, but will prevent potential damage to the ecosystem.

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