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Invasive non-native species


What are invasive non-native species?

Non-native species (NNS) are plants and animals which have been introduced (accidentally or deliberately) outside of their native range through human activity.

Many non-native species contribute positively to our lives, as livestock, crops, timber, garden plants or pets. However, a small proportion (10-15%) of non-native species spread rapidly and cause damage to the environment, economy or human health; these species are known as invasive non-native species (INNS).

INNS are recognised worldwide as one of the top drivers of biodiversity loss.

The law on non-native species

In Scotland, all non-native species are covered by Section 14 of the Wildlife and Countryside Act 1981 (as amended by the Wildlife and Natural Environment (Scotland) Act 2011).

The Act makes it an offence to:

  • release or allow to escape from captivity any animal to a place outwith its native range.
  • cause any animal outwith the control of any person to be at place outwith its native range.
  • plant or otherwise cause to grow any plant in the wild outwith its native range.

You can find out whether a plant or animal is outwith its native range on the NatureScot website.

Under the Scottish Government Non-native species Code of Practice, relevant organisations have a role as habitat leads:

Organisation Habitat responsibility


All terrestrial and wetland habitats and any others not detailed below

Scottish Government Marine Directorate

The marine environment

Scottish Forestry

Woodland and other habitats managed by Forestry and Land Scotland (the national forest estate)


Freshwater (still and flowing waters)

NatureScot is the overall lead body, and all named organisations have a range of specific responsibilities relevant to their particular habitat.

All of these organisations have a discretionary power to enter into Species Control Agreements or Species Control Orders to require action to be taken, or an activity stopped, to prevent the spread of INNS.

INNS in regulated activities:

Controlled Activities

Biosecurity measures should be used during any operation that could pose a risk of spreading INNS, e.g., engineering work, use of water pumps, or access to the area by any vehicles. There are biosecurity requirements and guidance in various SEPA documents:

Water transfers

The bulk movement of water between hydrologically unconnected waterbodies, mostly for water supply or hydropower generation, can pose a high risk of spreading INNS.

SEPA has published a Position Statement on the transfer of raw water which places strict requirements on any new water transfers to prevent the creation of pathways that could spread INNS between catchments.


Responsibilities relating to species such as Japanese knotweed, Himalayan balsam and Giant hogweed are shared by SEPA and NatureScot, depending on the situation.

SEPA is responsible for dealing with INNS in waste, for example where there is a known operator or transporter of the waste, or where disposal will be contained within a development site. Where a terrestrial species such as Japanese knotweed has been found in the wild with no known link to how it came to be there, then NatureScot lead on the response.

Waste transfer and disposal issues are covered comprehensively on NetRegs. This includes the SEPA guidance on the onsite management of Japanese knotweed and associated soils.

Planting schemes in developments and SUDS

The Be Plant Wise campaign is aimed at gardeners and pond owners but provides useful information on managing a pond to avoid harmful invasive plants that can also be used when designing aquatic planting schemes for amenity and SUDS ponds.

INNS on your land:

It is the responsibility of the landowner or land manager to prevent any non-native species on their land or water from spreading into the wild.

This means that if a non-native species is present on land or water you own or manage, you should take all reasonable steps to avoid it from spreading. In the case of aquatic species, this includes preventing it from spreading out of a pond or loch via any outflowing waters.

For invasive non-native species, you should also take steps to avoid them causing damage, for example by Eradication, containment or control.

Eradication, containment and control

Where possible, and where it is likely to help prevent spread, the best approach can be to eradicate the INNS. This may not be feasible for some aquatic species, especially where there are native or protected species which could be damaged during an eradication; in this situation the INNS should be contained and/or controlled.

Details of how to develop a management plan for eradication or control of plant INNS, including links to information on potential control approaches for different plant species, are given in WAT-SG-18: Control of Plants in or near to Water.

Containment could take the form of screen or other capture mechanisms at the outlet of standing waters (see Preventing downstream spread). Where the affected waters are used for recreation, it is vital to encourage good biosecurity for all water users (see INNS and biosecurity in water).

Preventing downstream spread

When carrying out any control that will disturb an aquatic INNS, measures must be taken to prevent propagules (plant fragments, animals, eggs etc.) from drifting downstream in any watercourses or drains from the pond or loch.

This usually means that some form of screen should be put in place at the pond or loch outlet to provide sufficient filtration to capture propagules of non-native species. It should be removed once there is no longer a risk of propagules washing downstream. All material captured by the screen should be disposed of appropriately (see Disposal of plant waste; seek further advice where non-native animals are involved).

The screen may need to be in place for several days or weeks after control is completed. Where there is a long-term risk of downstream spread then installation of a permanent screen should be considered, along with plans for ongoing management of the screen and any waste materials arising.

Any plans to place structures into the outlet or downstream watercourse should be discussed with the SEPA Permitting Team at an early stage of the design to ensure it will not create an obstruction to flow or cause other issues.

Disposal of plant waste

When developing a management plan, the disposal of any plant waste removed from the waterbody should be included in the plan.

Most non-native aquatic plant species can be successfully composted, but it should be done in a location where any leakage (including tiny plant fragments) cannot get back into the waterbody.

For domestic scale volumes of aquatic plant waste, adding it to a well-managed compost bin is sufficient, provided it is positioned away from any waterbodies. Once fully composted the plant material is no longer viable so the compost can be used in garden borders etc. as normal.

For large scale infestations which create a large volume of aquatic plant waste, high temperature composting is recommended, where plant material will reach at least 50C. A Local Authority composting facility may be suitable, with appropriate waste transfer authorisation.

The ‘compost with care’ information provided by the Be Plant Wise campaign provides additional guidance.

Spraying INNS with herbicide

Before considering the use of herbicide, check SEPA guidance on Control of plants in or near to water.

If herbicide is the only available option, the only herbicide licensed for use in or near water is glyphosate.

All plant protection products, such as herbicides, are licensed by the Health and Safety Executive. They can provide more information on appropriate use of licensed products.

To ensure you use a product authorised for aquatic use, check the HSE pesticides register. Note that this list is frequently updated so you should always check before using any herbicide.

INNS and biosecurity in your garden or pond

It is illegal to release, plant or allow to spread any non-native species into the wild. Don’t dump any non-native plants outside of your garden.

You should make sure any garden plants don’t spread out of your garden. Be Plant Wise gives practical advice on how to prevent the spread of garden plants into the wild.

The Gardening without harmful invasive plants guide can help you choose suitable plants.

When clearing out your pond, don’t allow any plants or animals to enter nearby water. See the Be Plant Wise tips for pond or aquarium plants

INNS and biosecurity in water

It is illegal to release, plant or allow to spread any non-native species into the wild. Take measures to avoid moving water and debris away when you leave a site.

If you take part in contact water activities such as yachting, canoeing or angling on rivers, lochs or the coast, follow the advice on the Check Clean Dry pages. The key principles are straightforward - whenever you leave the water, remember to Check Clean Dry:

Check your equipment, boat, and clothing after leaving the water for mud, aquatic animals, or plant material. Remove anything you find and leave it at the site.

Clean everything thoroughly as soon as you can, paying attention to areas that are damp or hard to access. Use hot water if possible.

Dry everything for as long as you can before using elsewhere as some invasive plants and animals can survive for over two weeks in damp conditions.

For water-based events, there is general guidance, plus a Scottish Events Biosecurity Guide and Risk Assessment Guide, both of which were developed by SEPA, Scottish Canoe Association and Royal Yachting Association.

What to do if you find an INNS

It is illegal to release, plant or allow to spread any non-native species into the wild. Don’t collect it or move it - leave it where it is!

Non-native species can easily be spread and are not always easy to see therefore good biosecurity practice is essential.

If you find NNS where you are working, check your legal obligations (see INNS in regulated activities).

If possible, please report your sighting (see How to report a sighting of INNS). Your data helps improve our understanding of how INNS are behaving in Scotland and can help inform management plans or other action to contain or control them.

How to report a sighting of INNS

If you want to report your sighting, make a note of:

  • the date
  • the species
  • the number or quantity seen
  • the national grid reference (the phone apps should generate this automatically but if you need help go to UK Grid Reference Finder)
  • take a photo if possible as this may help verify the record

You can report your sighting to:

Pink Salmon should be reported to Fisheries Management Scotland. Enquiries about Pink Salmon can be sent to Scottish Government Salmon and Recreational Fisheries email.

Escaped farmed fish should be reported to the Scottish Government Fish Health Inspectorate (FHI). It is a legal requirement for the operator to do so and FHI will investigate reports from partner organisations and members of the public in relation to fish farms. You can report escaped farmed fish by email or by calling 0131 244 3498.

Outside of office hours, you can call the main switchboard on 0131 244 1833 and ask for the FHI duty inspector. Further information is available from the Fish Health Inspectorate.

Who to contact about INNS

If you have a query that is not answered in other sections of this webpage, you can contact the habitat lead directly:

Species licensing enquiries

If you would like to release an animal or plant anything in the wild, or your activity risks spreading anything into the wild then you need to make sure that the area it will be spread into is within its native range.

For release of most non-native species, contact NatureScot: Tel 01463 725364 or email.

For release of freshwater fish, contact Scottish Government Marine Directorate by email.


To report illegal activity such as fly-tipping of non-native plants (or garden waste that could contain them), or the trapping or moving of crayfish):

  • Police: if you witness an illegal activity happening, contact the police using the non-emergency 101 phone number, or email. You can find more information on the Police Scotland Wildlife Crime webpage.
  • All types of fly-tipping, including the dumping of garden waste that could contain non-native species should be reported to the Local Authority where the dumping was found - check who to contact.

Japanese knotweed

If you have Japanese knotweed on your land, you should ensure it does not spread off your land.

If it spreads into the wild, this is an offence under the Wildlife and Countryside Act (see The law on non-native species).

You could also be affecting adjacent landowners. Where a non-native species spreads onto a neighbour’s land and causes a nuisance, if it’s not possible to come to an amicable agreement with the neighbouring landowner, then advice from a solicitor on the potential use of civil proceedings would be the next course of action.

The Royal Horticultural Society provides advice for gardeners.

If you carry out any control of this species or undertake any work on areas containing Japanese knotweed, check that you have the correct permissions before starting work (See Spraying INNS using herbicide and Waste).

North American Signal Crayfish

Signal crayfish (Pacifastacus leniusculus) are not widespread in Scotland, so efforts concentrate on preventing them from spreading to protect our uninvaded waters. Once they have been introduced it is very unlikely that Signal crayfish can be eradicated. There have been several trial eradications in small, enclosed waterbodies such as quarry ponds using chemical treatments, but this approach is not possible in larger standing waters or running waters where dilution would be too great and the damage the chemicals would cause to other wildlife would be unacceptable.


Although trapping may sound like a useful aid to getting rid of crayfish it can instead make the problem far worse. Traps tend to favour larger male individuals, removing natural predation within the population (the big ones cannibalize the small ones and can help keep the population in check) so leaving a younger, more readily reproducing population that spreads more quickly. Trapping will not control or eradicate a population, and commercial trapping or trapping for personal use is not permitted in Scotland. 

The NatureScot licensing team only issue licences for crayfish trapping under exceptional circumstances because the risk of encouraging their spread is so great. They do not issue licenses for the purpose of catching crayfish to eat because in addition to the problems above this also creates incentives for people to move them to new areas.

It is illegal to possess a live crayfish in Scotland. If you witness an illegal activity happening (i.e. the trapping or moving of crayfish), please do not approach the people doing it, but we would encourage you to contact the police using the non-emergency 101 phone number or by email.

If you catch one accidentally, do not take it away alive. Kill it humanely by placing it on a hard surface, then hit it with a single lethal blow with a heavy or hard object or crush it with a single action.

Preventing spread

You can help prevent the spread of non-native crayfish by following the advice in INNS and biosecurity in water and by reporting any you find (see How to report a sighting of INNS)

If you need to carry out any work on areas containing North American Signal crayfish, check that you are aware of your responsibilities (see INNS in regulated activities).

Pink Salmon

Pacific Pink Salmon (Onchorhynchus gorbuscha) are not native to European waters. They were introduced to some Russian rivers in the 1960’s but slowly spread to colonise some Norwegian rivers.

Occasional sightings of individual vagrant fish have historically been made in Scotland, but in recent years numbers have increased significantly to 139 in 2017; 42 in 2019; and 171 in 2021. Increasing numbers are also seen across southern Norway, Ireland and England.

They have a distinct two-year lifecycle, with invading fish being derived from ‘odd’ year stocks, so are currently only recorded in any numbers in odd years, but the increasing quantity of fish arriving threatens our aquatic biodiversity, including native Atlantic Salmon and other fish.

If you see or accidentally catch a Pink Salmon, please report it to Fisheries Management Scotland, where you can also find advice on what action to take.

There is more information on this species on the Scottish Government website.