The quagga mussel, first spotted by Environment Agency teams carrying out routine water quality testing on the River Wraysbury, has now been confirmed in a total of nine locations in the south east.

It’s important that everyone who uses lakes and rivers helps to slow the spread of this species by following the ‘check, clean, dry’ approach and thoroughly cleaning and drying any fishing or boating equipment.

Over the last few weeks the Environment Agency has stepped-up its monitoring on the River Thames and reservoirs in the local area to investigate the extent of the problem and the distance that the quagga mussel has spread.

The Environment Agency is continuing to work with a range of partners including Thames Water, Angling Trust and local angling clubs, to ensure that people check, clean and dry any equipment that has been in contact with water.

Environment Agency teams up and down the country have been briefed to be on the look-out for the quagga mussel. The quagga mussel can significantly affect freshwater ecosystems, and can outcompete native mussels. It can also block water pipes and smother boats’ hulls.

Sarah Chare, head of fisheries, biodiversity and geomorphology at the Environment Agency, said:

These newest discoveries only go to show just how prolific the quagga mussel is. We are monitoring the extent of its spread and working closely with partners to ensure they are aware of it and know what action to take. Everyone has an important role to play by following the simple steps of ‘check, clean, dry’. If you spot one then please report it to us through the online form.

Like the zebra mussel and killer shrimp this species comes from the Ponto-Caspian region – an area around the Black and Caspian seas in south-east Europe.

Simon Earl, head of water production at Thames Water, said:

Another invasive species is the last thing we need clogging up our network. But we have a lot of experience in dealing with zebra mussels, which are similar to quagga mussels, and there is no threat to the quality of the water we supply to our customers. We’ll continue to monitor the situation and would urge those using our reservoirs to help us stop the spread of the mussels by reporting any sightings and following Environment Agency advice on cleaning equipment.

Mark Owen, head of freshwater at the Angling Trust, said:

It’s vitally important that all water users, including anglers, take every possible precaution to stop this species spreading throughout the UK. Invasive species could do untold damage to freshwater and estuarine environments if they are allowed to spread which could have a significant impact on marine and freshwater fish stocks.

Quagga mussels tend to be about the size of a human thumbnail but can grow to about 4cm. The larvae of quagga mussels are not visible to the naked eye which makes drying a critical step in applying good biosecurity. There’s good evidence that rinsing or soaking equipment in hot water increases the chance of killing larvae and adults, and is a suggested addition to the check, clean, dry approach. The quagga mussel has now been confirmed at the following nine locations.

To the west of London: Wraysbury Reservoir River Wraysbury The Queen Mother Reservoir Queen Elizabeth II Reservoir Queen Mary Reservoir Bessborough Reservoir

In the Lee Valley: Warwick East Reservoir Warwick West Reservoir William Girling Reservoir



The Environment Agency will update the distribution map on its website if new discoveries are made.

There is specific biosecurity guidance for different water users on the non-native species secretariat check, clean, dry pages.