Invasive Non Native Species (INNS) are those that have been transported outside of their natural range and that damage our environment, the economy, our health and the way we live.

The problem

Invasive non native species (INNS) are the second greatest threat to biodiversity, being capable of rapidly colonising a wide range of habitats and excluding native flora and fauna.

Over the last 400 years INNS have contributed to 40% of animal extinctions where the cause is known.

Water is an excellent transport medium for the dispersal of many of these species, rivers and lochs and their banks and shorelines are amongst the most vulnerable areas to their introduction, spread and impact.

Ecological changes wrought by INNS can further threaten already endangered native species and reduce natural productivity and amenity value of riverbanks and water bodies.

The Dee, Cowie and Carron catchments currently have ten INNS, plus two translocated species (native to Great Britain but transported outside its natural range) – see below. 

American mink, Mustela vison

Occurrence: Present throughout the three catchments but have nearly been eradicated from the western Dee catchment by a sustained trapping programme. 

Problem: Mink prey on water fowl, small mammals and fish. They can contribute substantially to juvenile salmon mortality in local areas. Mink are linked to the decline of water voles in the Cairngorm National Park - 94% decline in distribution of water voles since 1950s.

Action: The RDT, through its membership to RAFTS, supports a mink control officer in NE Scotland whose job is to co-ordinate a mink removal programme. Further info. 

Japanese knotweed, Fallopia japonica

Occurrence: Localised in small dense pockets in the Dee catchment, from just above Ballater downstream. Dense stands in the lower Cowie around Stonehaven and localised in the lower river Carron.

Problem: Forms dense thickets which out-competes native plants and reduces biodiversity through altering the habitat for wildlife. Winter dieback of the plants exposes bank sides to soil erosion.

Action: Control programme on Rivers Cowie and Carron being undertaken, summer 2011, with volunteers. Further info.

 Giant hogweed, Hercaleum mantegazzianum

Occurrence: Individual plants and small groups in the Dee and Cowie catchments. Dense population on the Carron on outskirts of Stonehaven.

Problem: It is a public health hazard due to the toxins in its sap reacting with UV light to blister skin. Giant hogweed out-competes native vegetation, resulting in a loss of plant and invertebrate diversity. Winter dieback exposes river banks to soil erosion.

 Action: Currently preparing to survey distribution of this species.  Further info.

Himalayan balsam, Impatiens glandulifera          

Occurrence: Present throughout the Dee, below Dinnet

Problem: Forms dense stands that shade out native plants, reducing biodiversity and denuding river banks of understory vegetation. Winter dieback of the plant exposes bank sides to soil erosion.

 Action: Currently preparing to survey distribution of this species.  Further info.

 Water crowfoot, Ranunculus sp.

Occurrence: Native to Britain but not northern Scotland. It has been translocated to the Dee and is present in the middle and lower reaches (downstream of Dess); very prolific in some areas downstream of Banchory.

Problem: Dense stands have overwhelmed the stream bed, accumulating sediment and in some areas impacting freshwater pearl mussel beds and salmon spawning gravels.

Action: Dee DSFB in 2010 trialled removal of Ranunculus in the main stem of the Dee through hand pulling and digging out the plant by the roots. Will continue in 2011, focusing on salmon spawning areas. Survey results.

 Canadian waterweed, Elodea canadensis

Occurrence: Present in slow-flowing locations throughout the Dee downstream of Braemar.

Problem: Spread by disposal of plant fragments near waterways and escapes from garden ponds during floods. Can dominate native macrophyte communities, which can lead to their extinction and thereby impacts local invertebrate communities.

Action: Monitor for distribution. Futher info.

 Nuttall's pondweed, Elodea nutallii

Occurrence: Present confirmed in Loch of Skene.

Problem: Spread by disposal of plant fragments near waterways and escapes from garden ponds during floods. Can dominate native macrophyte communities, which can lead to their extinction and thereby impacts local invertebrate communities.

Action: Monitor for distribution. Futher info.

 Rhododendron, Rhododendron ponticum

Occurrence: Present in a few locations in the middle and lower Dee district.

Problem: Spreads and forms dense thickets which out-compete native plants, indirectly impacting on fish and invertebrate communities. Preventis site access.

Action: Monitor; felling where impacting on riparian habitat. Further info.

 Rainbow trout, Oncorhynchus mykiss

Occurrence: Introduced to commercial and angling club fishing ponds throughout the district. Escapees have been caught near some of these ponds.

Problem: Escaped fish are a potential source of viral and bacterial diseases affecting wild fish. They can out-compete our native salmon and trout.

Action: Monitor; close potential escape avenues through liaising with fisheries owners.

 American skunk cabbage, Lysichiton americanus

Occurrence: In the Lower Dee between Durris and Peterculter.

Problem: Escapes from gardens into the wild, spreading along waterways. Can out-compete native vegetation, having indirect effects on local wildlife.

Action: Monitor for distribution.

 Minnow, Phoxinus phoxinus

Occurrence: Thoughout the mainstem of the river Dee, locally abundant. Present in the River Carron.

Problem: Is a translocated species that has been introduced throughout the district by anglers. Minnows can out-compete native species for resources, but they also provide another food source for kingfishers, herons, sawbill ducks and larger fish.

Action: Monitor for distribution.

 Grey squirrel, Sciurus carolinensis

Occurrence: Introduced to Aberdeen and have spread along riparian corridors. Abundant as far west as Banchory, present up to Braemar.

Problem: Greys out-compete native red squirrels in mixed woodlands. Red squirrels are becoming more fragmented in distribution. Greys carry squirrel pox virus and are unaffected by it, but it is fatal to red squirrels.

Action: Support monitoring and trapping programme that is underway in Aberdeenshire. Save Scotland's red squirrels.

North American signal crayfish, Pacifastacus leniusculus

Occurrence: Present in the Esk district, which borders the south side of the Dee catchment. Also present in other Scottish catchments, including the Tay.

Problem: Excludes salmon from preferred habitat and impacts on aquatic invertebrates and macrophytes. Burrowing into river banks can undermine banks.

Action: Monitoring annually by DeeDSFB using crayfish traps. Immediate action if any are found. Further info.

Gyrodactylus salaris, Gs

Occurrence: Native to the Baltic States. Spread to Norway where it has wiped out salmon in 41 rivers. Not known to be in the UK.

Problem: Parasitic gill fluke that feeds on Atlantic salmon. If introduced into our rivers, would decimate salmon populations. Any (chemical) treatment would have major impact on biodiversity, if allowed. High risk of invasion through unintentional introduction from anglers and water sport enthusiasts.

Action: Awareness campaign run by DeeDSFB and RDT. Disinfection centres set up in Deeside for international anglers to use on their equipment.