Piranha invasion threatening native fish

Photo: Wikimedia CommonsThe Environment Agency warned of the dangers of releasing non-native species into UK rivers after staff discovered a piranha during a routine river monitoring survey.Environment Agency fisheries specialists spotted a dead piranha in the East Okement tributary of the River Torridge in Devon as they began a survey of fish species using electric fishing equipment.

At 35 cm long, the fearless piranha is commonly found in the Amazon River basin, and is the most ferocious freshwater fish in the world - infamous for its razor sharp teeth and hunting prey in packs.While piranhas would not survive in UK rivers, the introduction of non-native species poses a serious threat to native wildlife.

Floating pennywort (Hydrocotyle ranunculoides), originally from North America, was brought to Britain in the 1980s as a plant for tropical aquaria and garden ponds.

After being released into the wild, it is now starving rivers across the south of England and south Wales of light, nutrients and oxygen. This kills many of the species living in it and also increases the risk of flooding by blocking the waterway.

An autopsy carried out by the Environment Agency found the Piranha’s stomach was full of sweetcorn suggests it might have been kept as a domestic pet. Environment Agency experts believe the piranha was most likely to have been placed in the river once the fish became too large for its tank, and was found dead as the fish could not tolerate the low temperature of the water.

Fish species which the team would commonly expect to find in the river include salmon, brown trout and less commonly the bullhead, stone loach and minnow.

Mark Diamond, Ecology Manager at the Environment Agency, 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."

Eddie Stevens, one of the three-man monitoring team, from the Environment Agency 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."