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Home > Our work > Other issues > Non-native species

Non-native species

What is the issue?

Non-native species are plants or animals which adversely affect the habitats they invade economically, environmentally and/or ecologically. They can cause significant problems to our native animals and plants and annually cost millions of pounds to manage. Hundreds of freshwater species have been moved outside their native ranges, by deliberate introductions, within ballast waters of international shipping, canals, and releases from aquaria, gardens and bait buckets. This has resulted in many waterbodies now containing several non-native species each.

Introduced fish and invertebrate species are a great threat to our native populations. They predate, outcompete and displace native species from their preferred habitats. They can also spread parasites and introduce novel diseases, to which native populations have no natural immunity. Non native species can cause far-reaching ecological imbalances within watercourses, therefore controlling their spread is vital if we are to protect native species and their habitats.

The top ten ‘high impact’ alien species, according to the Water Framework Directive Risk Assessment, affecting water bodies in England and Wales have been identified as;

Australian swamp stonecrop (Crassula helmsii)
Floating pennywort (Hydrocotyle ranunculoides)
Water Fern (Azolla filiculoides)
Parrot’s feather (Myriophyllum aquaticum)
Common cord-grass (Spartina anglica)
Japanese weed (Sarassum muticum)
North American signal crayfish (Pacifastacus leniusculus)
Zebra mussel (Dreissena polymorpha)
Chinese mitten crab (Eriocheir sinensis)
Slipper limpet (Crepidula fornicata)

What S&TA has achieved so far

  • S&TA has worked closely with the Environment Agency and NGO colleagues to publicise the arrival of the killer shrimp (Dikerogammarus villosus), which was found for the first time in the UK in Grafham Water, in September 2010 (click to current information of killer shrimp found on website). Communications via our website, e-news, GameFisher etc, have raised awareness of the potential impacts of the killer shrimp and inform water-users how to prevent further spread of the shrimp.

What still needs to be done?

  • Currently, under the Water Framework Directive, alien species cannot, on their own, be a reason for a waterbody to fail ‘good ecological status’. S&TA views this as ridiculous, as the presence of dominant alien species may indicate a stressed ecosystem. We will continue to campaign for this to be changed.
  • We believe future focus should be on prevention, rather than cure. Education of the implications and damage to native ecosystems caused by non-native species must be translated to the general public to help prevent accidental introductions.

Other information