Sign up & join the conversation.

Invasive Species Prevention


Invasive species are one of the top 5 highest risks to world and UK biodiversity.

The spread of invasive species is a major issue in both marine and inland waters around the world. They can disrupt our boating activities, compete with native plants and animals and can cause major changes to entire ecosystems.


What are Invasive species?
Invasive species are plants and animals from other countries that have been introduced and have become established outside of their normal habitat or native country.


How did they get here?
Invasive species can be transported the UK in a number of different ways, including by shipping vessels, aquaculture industries and accidental/intentional release. They can also be transported from place to place by hitching a ride on boat hulls, anchors and propellers, or being carried in ballast and bilge water.


What’s their impact?
As well as the devastating environmental impacts, invasive species can spread disease, restrict navigation, block waterways, clog up propellers, and add significantly to the management costs of our waterways. Recreational facilities can also suffer as a result of these invasive species.

Fast-growing species like zebra mussels are already causing problems in many areas, blocking engine cooling water intakes resulting in engines over-heating. Didemnum vexillum, known as the carpet sea squirt, has a smothering effect; covering aquatic habitats in thick sheet-like growths and interfering with fishery and aquaculture operations. Once established, invasive species become extremely difficult and expensive to eradicate.


How can you identify INNS?
GB Non-Native Species Secretariat (NNSS) guides and maps
Marine Biological Association (MBA) INNS guides

Report sightings:
iRecord App: All Invasive Non-Native Species (INNS)


On the Water:

  • Avoid sailing or motoring through water plants and weed if possible. This can chop up plants and can spread them further. If caught up on the hull or propeller, invasive alien species can be transferred to another area.
  • If the boat is on the water but not in use and stationary for a period of time, if possible, raise propellers out of the water to minimise the risk of species entering the engine. Use your boat regularly to prevent biofouling of the hull and engine.
  • If an anchor has been used, wash off both the anchor and chain before stowing

After Use:

Check, Clean and Dry!

The best way to protect both your stretch of water and others around the UK from INNS follow the Check, Clean and Dry approach to removing INNS from your boat, equipment and clothing.


  • Check for any plant or animal material on your boat, equipment and clothing. Pay particular attention to areas that are damp or hard to inspect.
  • Remove visible fouling and put in the bin, not back in the water.


  • Wash your boat, equipment and clothing that has come into contact with the water thoroughly with tap water (including outboard, trailer and trolley/vehicle tyres). Pay attention to any crevices.
  • Flush outboard engines with clean fresh water before leaving the site using appropriate equipment, flush muffs or in accordance with manufacturer’s recommendations. Allow the water to drain completely from the engine in a vertical down position.
  • For boats kept in the water permanently or not lifted often, remove biofouling regularly from the hull with a sponge or soft brush to prevent build up.
  • Any fouling that cannot be removed with a soft sponge or brush must be lifted and cleaned onshore. Choose a marina operator with a filtered boat wash down facility that can capture not only biofouling, but any antifoul residue.
  • Where a filtered wash-down facility is not available, ensure removed biofouling is collected and disposed of in a bin.


  • When recovering your craft drain water from every part and all equipment that can hold water, e.g. water that collects in bilges, base of the mast and centre board casing before leaving a site
  • Clothing and equipment should be thoroughly dried for as long as possible before it is used elsewhere. This is important because many species can survive in damp conditions for up to two weeks.

On Land and Boat Storage:

  • Store boats and outboard engines in a location where any run-off does not drain into a waterbody (e.g. drains, gullies or rivers).
  • Return any engines to their vertical down position to drain.
  • Use general waste bins to dispose of any plant or animal material found in prop bags or other equipment.

Antifoul Your Boat:

If boats are normally kept in the water, the Check, Clean, Dry approach may not always be a practical method of preventing the spread of INNS:

  • An appropriate anti-fouling coating system and good maintenance are the best way of preventing biofouling accumulation, which therefore minimises the risk of spread.
  • Boat owners can play a vital role in preventing concentrated scrapings from entering the water by choosing a marine facility that uses a wash-down system that captures run off and by following the Green Blue’s best practice advice.


Boat Users


Green Products
& Services

Related Resources

Support Our Campaign
Stop The Spread!

Info and Guidance
Boating Around Wildlife

Info and Guidance
Anchoring With Care

Social Share Buttons and Icons powered by Ultimatelysocial