Guidance on Invasive Non-Native Species
Invasive Non-Native Species (INNS) are those not naturally occurring in specific regions in the UK (non-native) that have been introduced by the actions of humans and rapidly spread, out-competing native species (invasive). Only those that have serious negative impacts on our native species, our health or our economy are considered to be INNS.
INNS and the Thames
INNS are a problem for the Thames and its surroundings with established INNS in the river, on its banks and on nearby land.
The INNS of most concern in the Thames or considered most likely to next invade are listed below. You can find identification sheets, pictures and further information on the GB Non-Native Species Secretariat website.
|Common Name||Latin Name||Habitat||Further Info|
|Water primrose||Ludwigia grandiflora||Freshwater||NNSS Fact Sheet|
|Quagga mussel||Dreissena rostriformis bugensis||Freshwater||PLA Bulletin October 2014|
|Topmouth gudgeon||Pseudorasbora parva||Freshwater||NNSS Fact Sheet|
|New Zealand pigmyweed||Crassula helmsii||Freshwater|
|Killer shrimps||Dikerogammarus villosus and haemobaphes||
|Signal crayfish||Pacifastacus leniusculus||
|Chinese mitten crab||Eriocheir sinensis||
|Pacific oyster||Magallana gigas||
|Veined whelk||Rapana venosa||Marine|
|Marine splash midge||Telmatogeton japonicus||Brackish|
|Carpet sea-squirt||Didemnum vesillum||Marine|
|Slipper limpet||Crepidula fornicata||Marine|
|Japanese knotweed||Fallopia japonica||Terrestrial|
|Giant hogweed||Heracleum mantegassianum||Terrestrial|
|Himalayan balsam||Impatiens glandulifera||Terrestrial|
|Canada goose||Branta Canadensis||
|Ruddy duck||Oxyura jamaicensis||
|NNSS Fact Sheet|
|Pacific wireweed||Sargassum muticum||Marine|
|Pale galingale||Cyperus eragrostis||Terrestrial|
If you spot one of these species in or close to the tidal Thames, please report when and where to [email protected].
What Can I Do?
- Report sightings by email with a photo and location details to [email protected]
- Undertake good biosecurity generally
- To prevent spread of aquatic invasive species, undertake good biosecurity around water (see GB NNSS Check Clean Dry).
Generic advice for recreational users
Check equipment and clothing for presence of organisms, remove and dispose of safely.
Clean thoroughly, if possible by immersing in 45°C water for 15 mins or hot pressure wash for at least a minute. Contain wash water and dispose of safely.
Dry for at least 48 hours before using elsewhere.
When leaving an anchorage, wash off both the anchor and chain before stowing.
When recovering watercraft, drain water from every part and from all equipment.
Further information available on the GBNNS website
For users of watercraft (boats, canoes, kayaks and all watercraft)
For ships – ballast water convention
Why are INNS a problem?
- Compete with and displace populations of native species
- Spread disease
- Clog waterways
- Restrict navigation
- Affect water quality
- Clog water intakes
- Damage riverbanks and structures
INNS are estimated to cost the British economy over £1.7 billion every year.
What is the PLA doing?
The PLA is co-ordinating the formation of a Thames Vision INNS Working Group. It is planned that the group will produce a Thames INNS Strategy from which an Action Plan will develop to achieve interim targets that will contribute towards the two Vision priority actions to
"improve biodiversity of sites recognised for their wildlife interest and the connections between them" and "improve water quality by a range of measures including reduced litter in the river".
This should help us collectively achieve the Vision Environment and Heritage Goal
"The river the cleanest since the Industrial Revolution with improved habitats and awareness of heritage"
Page updated March 2021.