The stonefish, which reaches an average length of 30 to 40 centimetres and up to 2 kg / 5 lbs in weight, is the most venomous fish in the world having venomous sacs on each one of its 13 spines
Two species of stonefishes have been recorded in Australia, the Reef Stonefish and the Estuary Stonefish. They are found throughout shallow coastal waters of the northern half of Australia. The fish usually lies motionless, often partially buried in the substrate and perfectly camouflaged among surrounding coral, rocky reef, rubble, or aquatic plants.
One of the ways to tell the two species apart is the placement of the eyes. The eyes of the Reef Stonefish are separated by a deep depression, however those of the Estuary Stonefish are elevated and separated by a bony ridge.
The stonefish (Synanceia verrucosa) has 13 sharp strong dorsal fin spines that are contained within a sheath of thick skin. At the base of each spine there are two venom glands that discharge their contents along ducts in the spine. When disturbed, the fish erects its spines, but maintains its position on the sea floor.
As the most venomous fish in the sea, most would assume that stone fish kill their prey using the venom in their spines, but this is not the case. The venomous spines are for protection. To capture prey, on the other hand, the fish uses speed. It patiently waits for its prey to appear and then swims fast and quickly attacks. The attack can last as little as 0.015 seconds! When not chasing their prey however, the fish normally swims very slowly.
Stings to humans usually occur to the feet of swimmers or waders who have ventured away from clean sandy substrate and closer to the more complex bottom structure preferred by the fish. Multiple spines can often penetrate affected limbs, resulting in more extensive envenomation. The pain is immediate, excruciating and may last for many days. Muscular paralysis, breathing difficulties, shock, and sometimes heart failure and death can ensue.
To make things worse, stings can occur on the beach, not just in the water, since stonefish can survive out of the water for up to 24 hours.
For some, the pain of a sting alone can be lethal. Associate professor Bryan Fry, a venom researcher at the University of Queensland, Brisbane explains...
“It produces such mind-blowing agony that the body goes into shock and the person dies.”
Stonefish antivenom is the second-most administered in Australia.
Can you eat a Stonefish?
Even though the stonefish's potentially fatal sting has been described as the worst pain a person can feel, human death from eating stonefish is rare to nonexistent.
When stonefish venom is cooked, it loses its potency. And when served raw as in the sashimi dish Okoze–its venomous dorsal fins are simply removed. The body meat that remains is delicious and nontoxic.
Stonefish are edible to humans if prepared properly as the protein-based venom quickly breaks down if heated, while raw stonefish served as part of sushi is rendered harmless simply by removing the dorsal fins, which are the main source of venom. The fish are considered a delicacy in many parts of Asia, including south Japan, south Fujian and Guangdong in China, and Hong Kong. In the Hokkien-speaking area, they are considered delicacies and good for health.
Stonefish meat is white, dense and sweet, and the skin is also edible. They are usually cooked with ginger into a clear soup, and sometimes served raw as sushi or sashimi.
Although envenomation usually occurs in those engaged in marine sports, chefs may suffer envenomation when cutting stonefish, which is eaten either sliced raw, boiled, or deep-fried by Japanese. Since many people cook and eat Japanese food, it is important to know that cutting a stonefish for cooking carries the risk of envenomation.