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). A single pufferfish can contain enough TTX to kill 30 adults. Across various studies, the toxin has been described as anywhere from 100 times up to 10,000 times more potent than cyanide.

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.

Several species of the closely related porcupinefish (family Diodontidae) are also extremely poisonous yet still consumed as food fish in certain Asian countries.

Other common names for pufferfish are globefish, swellfish, balloonfish and blowfish, though as a dish it is known as fugu.

Improper preparation of fugu can cause fatal poisoning, so only restaurants with specially licensed cooks in Japan are allowed to sell it. For many, the consumption of fugu is a status symbol and devotees describe the dish as producing a pleasant, warm tingling. However, badly prepared fugu still hospitalizes around 34–64 people per year, resulting in 0–6 deaths per annum. Even though this poison is around 1,250 times deadlier than cyanide, some 10,000 tons of fugu are consumed annually in Japan alone.

The most common genus of pufferfish that is consumed as fugu is Takifugu, which has 25 species – the majority of which live in seas and areas of brackish water such as estuaries in the north-west Pacific.