Piranha found in the Thames

The carnivore - which, when in a feeding frenzy will attack any creature, including humans - was dropped by a seagull onto the deck of a boat. It is believed to have been released into the Thames by its owner.

It had only just died when it fell on the Thames Bubbler at Halfway Reach in Dagenham - more than 5,000 miles from its Amazon home.

The crew suspected the 10cm fish was a piranha and it was taken to the London Aquarium. Curator Paul Hale said: "It is a red-bellied piranha. It was probably released and floated to the surface where it was picked up by a seagull."

The red-bellied piranha (Pygocentrus nattereri), has short, powerful jaws lined with razor-sharp teeth capable of devouring 16cm of flesh with each bite. They hunt in shoals and can eat even large prey in seconds. It is thought a shoal ate up to 300 people when their boat sank near Obidos in Brazil in 1981.

But the fish cannot survive at temperatures of below 15C for more than a few days - and the Thames is currently 10C. Mr Hale added: "Piranhas are generally nervous, not the ferocious killers people think. They prey on weak, injured animals."

The dead fish, found on Tuesday, is being kept in deep freeze by the Environment Agency, which warned it was an offence to release any non-native species into the wild.