Red Sea Stonefish - The master of disguise
Believe it or not, there is only 1 species of stonefish in the Red Sea (Synanceia Verrucosa) although at least 5 other species are often mistaken for stonefish by divers. These would be the scorpionfish, of which there are 4 distinct species and the filamented devilfish. This is not surprising when you consider that scorpionfish, lionfish, and stonefish all belong to the same family (Scorpaenidae).
All members of this family have similar characteristics in that they all have venomous spines. The stonefish has 13 dorsal spines, each containing 2 venom sacs, 3 venomous spines on its anal fin, and 2 venomous spines on each of its pelvic fins. It is officially the world’s most venomous fish and the venom it injects can kill an adult in less than an hour. Stepping on or accidentally touching the spines of this fish can cause you vomiting, fever, swelling, excruciating pain, difficulty breathing, and tissue destruction around the entry wound so immediate medical attention is imperative. First aid involves placing the affected area in very hot water, as hot as the patient can stand, for between 20 and 30 minutes (not more than 30 minutes) as the heat helps to break down the proteins in the venom. If there are spines in the wound do NOT try to remove them but simply pad around them.
However, this fish is not out to get you. It will not chase you with the intention of harming you. Rather it uses its venom as protection and to avoid predation. Its main predators are sharks, rays, and moray eels.
The stonefish is a clumsy mover that does not travel very far. It is a bottom dweller and is a master of camouflage that can be found partially buried in the sand or hiding among coral blocks or rocks. It may even be covered in algae thus enhancing its disguise. Although naturally a brown or grey color it can take on other colors to fit in with its surroundings. Often the only clue to its presence is its highly arched mouth pointing upwards and the eye swellings.
The stonefish is not an active predator but rather lays in wait for its prey to swim by. It has a very large mouth with powerful jaws that can strikeout and suck down its prey whole extremely quickly, in less than 15 milliseconds. They like to eat reef fish and bottom-dwelling invertebrates.
The stonefish lives a solitary life. However, males and females do come together in groups briefly during the mating season when the female will lay eggs on the seafloor and the males will swim over the gelatinous egg mass releasing sperm to fertilize them. The eggs of the stonefish are quite large compared to the eggs of other similar-sized fish and the hatchlings are usually already well developed enough to defend themselves when they emerge. Other than this basic information very little is known about the mating habits of stonefish.
Margaret Hargreaves - PADI Instructor