The piranha was discovered in east London

A seagull is thought to have dropped the carnivorous, razor-toothed, red-bellied piranha on to a boat's deck.

It had only just died, with marks from the seagull's beak still on its back.

It is believed its owner had released it into the river - but the fish cannot survive for more than a few days in temperatures below 15C (59F).

The piranha landed on the Thames Bubbler at Halfway Reach, Dagenham, East London.

Owned by Thames Water, the boat pumps oxygen to keep the river's 119 types of fish alive.

The Environment Agency said it was an offence to release non-native species into the wild.