Most poisonous fish

Many species of fish are poisonous to eat, but the most poisonous are the pufferfish (family Tetraodontidae) of the Red Sea and Indo-Pacific region, which contain a neurotoxin called tetrodotoxin (TTX) – one of the most powerful non-proteinous poisons. Their ovaries, eggs, blood, liver, intestines and, to a lesser extent, skin, contain TTX, which is derived from bacteria such as Pseudomonas and Vibrio spp present in shellfish and other invertebrates that they eat. A 2017 study published in the journal Toxins puts the oral LD50 for tetrodotoxin at 232 micrograms per kilogram of body weight – which means a lethal dose for a 70-kg (154-lb) human could be as little as 16 milligrams (0.0005 ounces).

Earlier studies suggested that even smaller quantities of tetrodotoxin – e.g., 1–4 milligrams (0.00003–0.0001 ounces) – could be lethal to humans, however owing to a lack of empirical data, such reports are now being treated with caution.