Most venomous fish

The most venomous fish in the world are stonefish belonging to the genus Synanceia. The most studied species are the estuarine stonefish (Synanceia horrida), which are found inshore in muddy bays around China, south-east Asia and Australia, and the reef stonefish (S. verrucosa), which is found offshore on coral reefs of the Red Sea and Indo-Pacific. They have been shown to have highly similar venom. Stonefish possess up to 15 dorsal spines, each with two venom sacs containing a total 5–10 milligrams of venom. S. horrida venom has an LD50 rating as low as 0.4 micrograms (μg) per kilogram, thus a lethal human dose can be delivered easily by only one or two spines.

Little to nothing is known about the other three species from this genus (S. alula, S. nana and S. platyrhyncha) but it is presumed they have very similar and equally potent venom. S. horrida and S. verrucosa, however, are much larger than the other three species and therefore considered much more dangerous.

The most poisonous fish, meanwhile, are the pufferfish (family Tetraodontidae) of the Red Sea and Indo-Pacific region. Their bodies contain a toxin called tetrodotoxin, one of the most powerful non-proteinous poisons, which can be deadly if ingested.