The Ponto-Caspian quagga mussel, Dreissena rostriformis bugensis (Andrusov, 1897), invades Great Britain

Great Britain has been subject to an increasing rate of invasion from freshwater species of Ponto-Caspian origin. A recent horizon-scan of potential invaders into Great Britain named the Ponto Caspian quagga mussel, Dreissena rostriformis bugensis (Andrusov, 1897), as the non-native species least wanted. On 29(th) September 2014 quagga mussels were discovered in the Wraysbury River, Surrey, during a routine kick sample collected by the Environment Agency. Identity was confirmed using genetic markers (Cytochrome Oxidase I - COI) on five individuals encompassing a broad morphological variation. The absence of very large individuals (max. length 16 mm), absence of shells and absence of quagga mussels in samples collected during March 2014 point toward a recent invasion. The quagga mussels were found attached to submerged rocks, vegetation, bridge walls and shells of zebra mussels, Dreissena polymorpha (Pallas, 1771). The collection site is a small (<5m wide), shallow (<50cm deep) stream that is not navigable or regularly fished. This suggests that the species is more widely distributed than the current location, because such a system is unlikely to be the point of introduction. The shallow depth (30cm) in open water at which quagga mussels were abundant is surprising given that zebra mussels have failed to establish in such habitats, despite being present in the catchment for over 100 years. Previously published models predict quagga mussels will establish widely across England, western and southern Wales and central Scotland. The high abundance and inter-connectivity of waterways adjacent to the Wraysbury River suggest further spread is likely. Containment through national biosecurity measures (e.g. 'Check, Clean, Dry' of boats and equipment, as promoted by the UK Environment Agency) is recommended, although ultimately it can be assumed that quagga mussels will cause similar widespread ecological and economic harm in Britain as has been experienced in invaded regions of Western Europe and North America.