Stonefish (Synanceja verrucosa)

Length: up to 0.4 mDistribution: Pacific and Indian Ocean, ranging from the Red Sea to Great Barrier Reef

Synanceja verrucosa is a fish species, sometimes lethal to humans, which is known as the reef stonefish or simply stonefish. They are carnivorous ray-finned fish with venomous spines that lives on reef bottoms, camouflaged as a rock. They are the most venomous known fish in the world.

The average length of most stonefish is about 30-40 centimeters. The largest Stonefish ever recorded was 51 centimeters long. It has a mottled greenish to mostly brown colour which aids in its ability to camouflage itself among the rocks of many of the tropical reefs. It eats mostly small fish, shrimp and other crustaceans.

Like the shark family, stonefishes do not possess a swim bladder and swim by thrashing their tail in a side-to-side manner. However, divers rarely see a stonefish swimming (which has given rise to the often stated and incorrect statement that “stonefish can’t swim”) as they are usually found motionless on the coral or floor. Unless severely frightened, a stonefish will prefer to move by walking on its pectoral fins.

Its main habitat is on coral reefs, around dull coloured plants, near and about rocks, or can be found dormant in the mud or sand.

The Reef Stonefish is the most venomous fish in the world. Its dorsal area is lined with 13 spines that release venom from two sacs attached to each spine. Its venom causes severe pain with possible shock, paralysis, and tissue death depending on the depth of the penetration. This level can be fatal to humans if not given medical attention within a couple of hours. Immediate first aid treatment requires immersion of the affected limb in hot water, ensuring that it is not so hot that skin damage may occur. The immobilisation of venom at penetration site by tourniquet or firm constrictive bandaging is no longer recommended.

The venom consists of a mixture of proteins, including the hemolytic stonustoxin, the neurotoxic trachynilysin and the cardioactive cardioleputin; an antivenom is available.

The venom is protein based, and it can be (partially) denatured by the application of a very hot compress to the injury site. Some relief can be gained from infiltrating the wound with a local anaesthetic. This is a temporary measure to reduce localized pain and shock. Medical aid must be sought at the earliest opportunity. Typically, surviving victims suffer localized nerve damage occasionally leading to atrophy of adjoining muscle tissues.

There have been unproven reports of osteo-arthritic sufferers experiencing improved mobility and reduction in joint pain following envenomation episode. The responsible agent has not been identified.

The pain is said to be so severe that the victims of its sting want the affected limb to be amputated. The poisonous sting of Scorpion Fish and Lionfish are said to deliver almost the same level of pain.