Aquatic non-native species

Invasive non-native species are amongst the greatest threats to biodiversity.  They can badly affect native species and the ecosystem, causing major problems for the environment and the economy.  Globally, invasive species have contributed to 40% of the animal extinctions that have occurred in the last 400 years.  In Scotland, freshwater invasive species are becoming more of a problem that we are working with others to address.

What can be done?

Invasive species can be very difficult and expensive to control.  This is particularly the case in rivers and lochs.  So, prevention is better than cure.  To prevent aquatic invasive species becoming established we are working with others on an important project to highlight the threat aquatic invasive species pose, improve 'biosecurity' and promote action  .  We are also taking forward targeted conservation action on particular species.  Where some species have become established early action is often the only real hope.  There have been some notable successes in controlling invasive species, such as in the River Tweed  and the Western Isles.  These show that with determination, commitment and sufficient resources it is possible to win the battle against some invasive species affecting our rivers and lochs.

What species are here?

There are a number of non-native species already present in and around our rivers and lochs. Few of these are invasive, but there are a number that have become established and are causing problems, including:

• North American signal crayfish (Pacifastacus leniusculus)
• New Zealand pygmyweed (Crassula helmsii)
• American mink (Mustela vison)
• Ruffe  (Gymnocephalus cernuus)
• Canadian   and Nuttall's  pondweeds (Elodea canadensis & E. nutallii)
• Giant hogweed  (Heracleum mantegazzianum)
• Japanese knotweed  (Fallopia japonica)
• Parrot's feather  (Myriophyllum aquaticum)
• Himalayan balsam  (Impatiens glandulifera)
• Curly waterweed  (Lagarosiphon major)

What species could arrive?

The following examples are invasive species that are close to, but have yet to reach, Scotland:

• Gyrodactlyus salaris
• Zebra mussel  (Dreissena polymorpha)
• Floating pennywort  (Hydrocotyle ranunculoides)
• Asian topmouth gudgeon  (Pseudorasbora parva)

What effects do they have?

Invasive non-native species are non-native animals or plants that have the ability to spread, causing damage to the environment, the economy, our health and the way we live.  They threaten our native plants, animals and habitats often by displacing native species and dominating habitats.  Invasive species are also costing our economy a huge amount of money - estimated at £2-6 billion per year in the UK.  If the salmon parasite Gyrodactylus salaris was to be introduced to our rivers, a Scottish Government report  estimated the potential loss to Scotland would be £633 million, with severe consequences for rural communities.

How do they they get here?

There are a variety of ways that can non-native species have been introduced to Scotland, both accidental and deliberate. These include: recreation (attached to fishing equipment or in boats/canoes etc); the transport of fish for fisheries/aquaculture; escapes from gardens and ponds; garden centres; and aquaria. 

How can I help?

A lot of effort is being put into awareness raising and you can help by ensuring that you do not accidentally release any invasive species.  Action is taking place across Scotland in a project with the Rivers and Fishery Trusts of Scotland  .  If you are concerned about freshwater invasive species then local plans are being developed and you can help contribute  .  It is often very difficult, if not impossible, to eradicate some species after they become established.  Therefore preventing introductions is the first priority.  But early intervention is also critical and you can report any aquatic invasive species  .