Marine non-native species

Scotland has a growing problem with marine invasive non-native species, which threaten marine biodiversity and more.

Invasive non-native species can have serious negative impacts on native Scottish habitats and species. They can put at risk whole ecosystems – and thus marine biodiversity and our economy – and affect our health.

Early detection is crucial if we’re to try to clear an invasive species that has arrived in our waters. It may be possible to contain or manage populations of a species found only in patchy locations.

Not all the non-native species that arrive in Scottish waters become invasive. Many are present without significant effect.

Impacts on the marine environment

Invasive non-native species in our seas can have significant impacts on both biodiversity and the economy.

Away from their native habitats, invasive species are often able to grow very large and very quickly, and can displace native species. They can become the most dominant species in the area and some can smother other creatures.

Invasive species can have impacts on our marine industries, for example:

  • seaweeds can grow on structures such as piers, slipways, fish farm cages and boat hulls or get tangled in boat propellers
  • by killing or competing with marine aquaculture species
  • by spreading disease

Invasive species that threaten Scotland

Marine invasive non-native species that are now widespread and well established in Scotland include:

Report a sighting of wireweed, still relatively new to Scotland, by emailing Find out how to recognise wireweed.

Invasive species found only in patchy locations within Scotland include:

Report a sighting of the carpet sea-squirt via the Biological Records Centre website.

Species present in the British Isles but yet to reach Scotland include:

Preventing introduction

It’s extremely hard to get rid of an invasive species once it’s established in Scottish waters. So it’s vital to prevent species arriving here in the first place.

Activities that can move non-native species around the world include:

  • shipping – attached to ship hulls or in ballast water
  • transport of fish and shellfish for the seafood industry
  • scientific research
  • species escaping from public aquariums

Non-native species may be released by accident or on purpose.

Marine biosecurity planning is a critical step in creating a framework to reduce the risk of introduction.

You may also wish to find out about the law, management and regulation of invasive non-native species.

Marine biosecurity planning guidance

Marine Biosecurity Planning Guidance for producing site and operation-based plans for preventing the introduction of non-native species

Marine biosecurity planning – Identification of best practice: A review: SNH Commissioned Report No. 748

You can also find out on the Non-native Species Secretariat website about: