Toad Fish (Toadfish): Venom, Touching and Eating Risks

A toad fish is either a true toadfish, a bottom-dwelling fish of the family Batrachoididae found along coasts such as the US Atlantic, or, in Australia and New Zealand, a small pufferfish. Wikipedia lists the name in at least four families, given to fish that look toad-like or croak with their swim bladder.

The difference matters for safety. True toadfish are a bite and spine hazard. Australian toadfish are a poison hazard if eaten, because they are pufferfish.

True toadfish are ambush predators that sit on the bottom. Wikipedia counts about 83 species, from 7.5 cm to 57 cm long. Most live in the sea, but one subfamily, Thalassophryninae, lives in South American fresh water, including the Amazon, and it is the group with real venom: its spines are hollow and connect to venom glands that can give a painful wound.

The species most North American anglers meet is the oyster toadfish, Opsanus tau, found near shore from Maine to Florida (Wikipedia). Marks to check:

• Broad, flattened head and a very large mouth with sharp teeth and powerful jaws
• Yellowish body with a pattern of brown oblique bars
• Spine at the front of the first dorsal fin
• Size up to 43.2 cm (17 in), usually under 38 cm (15 in)

Wikipedia describes the oyster toadfish as not venomous, but the jaws and spine can still injure a hand. Males call with a 'boatwhistle' made by muscles that contract the swim bladder up to 300 times a second, and in 1998 NASA flew oyster toadfish into space to study how microgravity affects the balance organs of the inner ear.

In Australia the fish called toadfish are pufferfish of the family Tetraodontidae. Western Australia's Department of Primary Industries and Regional Development says this family carries tetrodotoxin, a highly lethal toxin found in the skin, flesh and organs. Wikipedia states that eating the common toadfish can be fatal.

Three you are likely to see:

• Common toadfish, Tetractenos hamiltoni: up to 14 cm, sandy to whitish with small brown spots on the back and brown bars beneath; often buries itself in sand with only the eyes showing (Wikipedia)
• Smooth toadfish, Tetractenos glaber: a close relative with larger spots and less prominent skin spines than the common toadfish (Wikipedia)
• Weeping or banded toadfish, Torquigener pleurogramma: up to 22 cm, with dark vertical 'tear' lines down the cheeks and a dark line along the side (WA DPIRD)

The Medical Journal of Australia describes poisoning symptoms as numbness around the mouth, tingling and numbness in the limbs, nausea and vomiting, loss of coordination and slurred speech, progressing in severe cases to paralysis and breathing failure. Symptoms usually start within 90 minutes, and within 1 to 2 hours in severe cases. There is no antidote; treatment is intensive supportive care, including breathing support.

If anyone has eaten a toadfish or pufferfish, or has numbness or tingling after eating fish, call emergency services or your local poison control centre immediately. Do not wait for symptoms to get worse.

Treat both kinds with care rather than as harmless.

• True toadfish: the risk is mechanical. The oyster toadfish has sharp teeth, powerful jaws and a dorsal spine (Wikipedia), and the South American Thalassophryninae have venomous spines. Keep fingers away from the mouth and handle with a tool or a wet cloth. A spine puncture that becomes very painful, swollen or red, or any sign of an allergic reaction, needs a doctor
• Australian toadfish (pufferfish): the toxin is in the skin as well as the flesh (WA DPIRD). If you catch one, WA DPIRD advises releasing it as carefully and quickly as possible, because blowfish can struggle to deflate out of water. Wash your hands afterwards and never let the fish near food
• Pets: WA DPIRD reports that pets have died after eating blowfish left on beaches, and asks anglers never to leave them on the shore or jetty. If a dog or cat eats one, go to a vet straight away

If you cannot tell which toadfish you have caught, photograph it before release; the FishLens app identifies it from the picture. Use the ID to decide how to handle it, never to decide whether it is safe to eat.

Do not eat any fish called toadfish unless you are certain of the species and local health authorities confirm it is eaten there. In Australia and New Zealand the answer is simply no: those toadfish are pufferfish, and the Medical Journal of Australia notes there is no antidote to their toxin.

True toadfish are a different case but not a casual one. Wikipedia says toadfish are not normally fished commercially, though some are taken locally for food or turned into fishmeal. Because the same name covers a poisonous pufferfish, identification has to come first. If you have eaten any fish and then feel numbness, tingling or weakness, get medical help immediately.