Environment Agency officials in Devon have found a dead aquarium fish in a river which they have misidentified as a Red-bellied piranha.
The illegally dumped fish, which was found by Environment Agency fisheries specialists electro-fishing in the East Okement tributary of the River Torridge in Devon, was identified as a Red-bellied piranha, Pygocentrus nattereri.
Eddie Stevens, one of the team of scientists who found the fish said: "What we actually came across was something which we would not expect to find in our wildest dreams - we could hardly believe our eyes.
"After completing 20 metres of the survey a large tail emerged from the undercut bank on the far side of the river. Our first thought was that a sea trout had become lodged in amongst the rocks and debris collected under the bank. But when it was removed from the river we were speechless to find it was a piranha."
The Environment Agency said that the piranha's stomach was full of sweetcorn, which suggests that the fish was a pet which was dumped in the river after it outgrew its owner's aquarium, and was found dead as it could not tolerate such low water temperatures.
Media reports are stating that the "piranha" which measures around 35cm/14" in length is unusually large, as the species typically reaches just 20cm/10".
The Agency itself said: "In shoals the piranha ambushes its prey, stripping the flesh of large animals such as Anaconda or even Jaguar within minutes. They have also been known to attack humans devouring flesh and bones to leave no trace."
However, Practical Fishkeeping believes that the fish in the Agency's image appears to be a Red-bellied pacu, Piaractus brachypomus, a species that can reach over 80cm and weigh more than 25kg.
This largely herbivorous species was once a common aquarium fish, but the species has become less common as the keeping of larger-growing species has fallen out of favour and many shops have become unwilling to re-home fish purchased by fishkeepers unable to adequately meet their long-term needs.
Mark Diamond, the Agency's ecology manager said: "Whilst piranhas can't survive the colder climates of the UK, this latest find highlights a real issue - that releasing unwanted exotic pets or plants into rivers can have serious consequences for native wildlife.
"Rather than dumping things in the wild, we would urge people to seek advice about what to do with exotic species."
Practical Fishkeeping advises all fishkeepers to carefully consider all new fish purchases and to never illegally release any unwanted aquarium fish into the wild.