Killer shrimp named UK's worst 'alien invader'

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The Environment Agency has named the worst non-native invader of UK waterways as the ‘Killer shrimp' (Dikerogammarus villosus), so named as it kills native shrimp and young fish.

The EAs top ten list of 'alien invaders' are:

  • Killer shrimp
  • Water primrose
  • Floating pennywort
  • American Signal crayfish
  • Topmouth gudgeon 
  • Giant hogweed
  • Japanese knotweed 
  • Himalayan balsam
  • Mink
  • Chinese Mitten crab

The Killer shrimp is a relative newcomer to UK waters. Originating from the Ponto-Caspian Region of Eastern Europe, it was only reported for the first time last year.

So far the shrimp has only been reported in Wales and Cambridgeshire. Despite measuring just 30mm/1.2" long, this shrimp can cause severe problems for British waters as it has a voracious appetite which can severely alter native habitats. In addition, it has a high rate of reproduction meaning that it has the potential to spread rapidly.

Defra and the EA both predict that if the shrimp becomes widespread it will threaten a number of native species through predation and competition and will have knock-on effects for biodiversity and the wider functioning of freshwater ecosystems in the UK.

The shrimp has already colonised parts of Western Europe, killing and out-competing a range of aquatic species such as freshwater invertebrates, particularly native freshwater shrimps and even very young fish.

The EA say that they currently spend £2m a year controlling invasive species and that the overall cost to the economy is probably in the region of £1.7bn a year. Invasive species can cause damage to riverbanks and buildings, increasing flood risk and hitting native wildlife. They can even become so prolific that anglers, fishermen and boaters cannot use the waterways.

Trevor Renals, invasive species expert at the Environment Agency, said if invasive species are not controlled there is a risk of losing some native species and incurring even more clean-up costs, as well as "falling short of the strict EU targets for our rivers and lakes".

"We would urge everyone to help stop the spread of these species by making sure that garden and pond plants don't end up near rivers and parkland and thoroughly cleaning any fishing, boating and canoeing equipment when moving between waterways."

For more information see the GB non-native species secretariat website.

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