Stonefish are a marine or brackish species of fish belonging to the Synanceiidae family. They are not to be confused with certain scorpionfish of the Scorpaenidae family that are also referred to as rockfish or stonefish. There are about five species total living in the coastal regions of the Indo-Pacific oceans, from Africa and the Red Sea, to Japan and Australia. Stonefish live among shallow waters on coral and rocky reefs, as well as in mudflats and estuaries. Some species can live in rivers but require either brackish water or must return to a saltwater environment at some point. They can survive for 5 to 10 years in the wild, grow to be around 30-40 cm in length and may weigh up to 5 lbs.
They do have two pelvic and three anal spines, but they’re hidden under the skin. Their appearance displays encrusted brown or grey skin with red, orange or yellow patches. Their texture helps them camouflage among their surroundings to avoid predators and ambush prey. Sometimes algae may also be growing on this fish because of their lifestyle. They will wait for hours to ambush prey once they are less than their body length away. A stonefish attack lasts as little as 0.015 seconds and they swallow their prey whole. Their diet consists mostly of other fish and shrimp. When not chasing prey, stonefish swim very slowly.
Stonefish are famous as the most dangerous venomous fish in the world. There are venomous sacs on each of their 13 spines and the venoms have both cardiovascular and neuromuscular toxicity due to their mix of enzymes and non-enzymatic protein. Their venom is only used as a defense mechanism against predators, rather than for capturing prey. The amount of venom released is proportional to the pressure applied. Empty sacs will refill after a couple of weeks. A person should seek immediate medical attention for anti-venom if stung because of the severe pain and possibility of heart failure or even death if left untreated.
Another uncommon fish trait stonefish hold is the ability to survive up to 24 hours out of water. They do this by absorbing oxygen through their skin, but they will eventually succumb to dehydration and suffocation if they can’t return to the water. Most stonefish lead solitary lives except when mating, but some have been found as part of a group. The females lay around one million eggs for the males to fertilize. The hatchlings are well-developed but may take up to three years to mature. Sharks, rays and humans are the biggest predators towards stonefish. Humans will consume stonefish as a delicacy in Asia or capture them for aquariums, but this does not appear to be causing unstable numbers in wild populations.