Stonefish: shy, venomous and almost invisible reef inhabitant

The stonefish is a member of the family Synanceiidae, a group of venomous fish whose sting can be fatal to humans. They are found in large numbers in the coastal regions of the Indo-Pacific oceans, although there are also species along the coasts of Florida and the Caribbean. Australia is the place where stonefish are most abundant, but they can also be found in the Philippines, the Red Sea, the Maldives, and Indonesia.

This fish has thirteen spines on its dorsal fin that inject an amount of venom proportional to the pressure applied. The bite causes excruciating pain and enormous swelling. Its venom spreads rapidly, killing tissue and causing muscle weakness, temporary paralysis and shock, which can be fatal if not treated immediately.

Stonefish live in coastal waters, a few meters deep, perfectly camouflaged by pretending to be a rock or a piece of coral. Their skin is gray with white, brown, red or even yellow and green touches, and they have small protuberances along their body that give them the appearance of an underwater rock with algae or lichen. They have an average size of up to 35 centimeters in length, although "monsters" of up to 50 centimeters have been found.

A fish capable of living out of water

They usually live in rocky or coral environments, often under rocks or overhangs, and are able to bury themselves under the sand using their large and powerful pectoral fins. It can also survive out of the water for up to 24 hours, waiting for the tide to return it to the sea. This increases the risk of being stung by this fish as swimmers may step on one mistaking it for a rock.

Stonefish in Maldivian waters. Image by Philippe Guillaume

Can you identify the two stonefish in this picture? Photo by jpmckenna - Loitering Around North Vancouver

The stonefish feeds on fish and crustaceans. When one of its prey swims up to the stonefish, it opens its huge mouth and, at a dizzying speed similar to that of a frogfish, devours its victim in milliseconds. Despite its powerful venom, this fish is not immune to other natural predators. Larger sharks such as tiger sharks, white sharks and even rays feed on them. Juvenile stonefish are also eaten by poisonous sea snakes. In Japan and China, this fish is considered a delicacy and quite expensive, despite its appearance and poisonous spines. It is served as sashimi, and if you go to a restaurant in Japan and ask for Okoze, you will be served the most poisonous fish in the world.

Stonefish are not dangerous as long as they are not disturbed or attacked, but if they feel threatened they will raise their dorsal fin to prevent an attack.