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  1. Scotland
  2. Nith
  3. Biosecurity


An alien non-native species is a species which is not native to the local area / region or Scotland. The introduction of an alien species, either as a deliberate release or inadvertently through escapes can disrupt the natural balance of an ecosystem. Direct effects of an introduced species may include predation, habitat loss or augmentation, or competition for habitat and food resources. Indirect effects from alien species include the introduction and / or spread of diseases and parasites. Most non-native species are very difficult and expensive to eradicate or control once established.

Biosecurity issues are of increasing economic and ecological significance. According to a survey, 'An Audit of Alien Species in Scotland', conducted by Scottish Natural Heritage, there are approximately 1000 non native species present in Scotland and while most exist in small populations with little impact on native flora and fauna, a small but significant proportion of these non native species are invasive. Recognition of the importance of the prevention, control or eradication of non native invasive species, parasites and diseases local river catchments has resulted in Fishery Trusts across Scotland writing Biosecurity Plans to help address these concerns.

The Nith Catchment Biosecurity Plan is available to download from here. It is the aim of the plan to unite different organisations and the general public in the prevention and control of invasive nonnative species (INNS) and anyone who is interested in helping with any of these projects will be welcomed.

Anglers have a key role to play in identifying, reporting and ensuring they do not intentionally or accidently introduce or spread damaging alien species.

Any sightings or questions regarding Biosecurity please contact Debbie Parke at the Nith Catchment Fishery Trust on 01387 740043

Key species to be aware of

Fish - never introduce non-native fish species to any water without the appropriate licence. Introduced species can have a devastating impact on native fish stocks. Although now illegal, the loss or release of live bait by pike anglers has caused problems in some Dumfries & Galloway waters

Plants - key species of concern in Dumfries & Galloway include Japanese knotweed, Himalayan balsam and giant hogweed. There are control programmes aimed at eradicating these species from the riparian zone of all the region's rivers. Please report to the Nith Catchment Fisheries Trust the presence of these species on any river banks. Great care must be taken not to accidently spread the seeds of balsam. For more information on identification and their control see tab labelled 'INN plants'

Invertebrates - North American signal crayfish are present in a few Dumfries & Galloway waters and causing extensive ecological damage. If you catch a crayfish please kill it immediately (there are no native crayfish in Galloway) and report to the Nith Catchment Fishery Trust.

Disease / parasites - Gyrodactylus salaris (GS) is a freshwater ecto-parasite that infects Atlantic salmon and some other salmonid species. The parasite is less than 1 mm long and infests the skin, fins and gills which eventually kills its salmon host. An infestation of GS in a river will threaten the existence of any salmon population. At the present time this parasite is restricted to Norway, Sweden, Finland, Russia and some other Baltic countries but importantly has not yet occurred in the UK. There are various ways in which GS could be introduced into the UK, although the most likely route would be through water or fish from infected areas but there is also a risk from contaminated equipment from anglers and any other freshwater recreational activity (canoes, diving gear, etc). Always ensure you disinfect your angling equipment if you have recently fished abroad.

Invasive species

In 2010, a project to control Invasive Non-Native Species (INNS) within the Nith catchment was launched. The project has focused on the control of invasive species of plants such as Japanese knotweed, Giant hogweed and Himalayan balsam, all of which were introduced into the Nith catchment as ornamental garden plants. Unfortunately, due to their invasive nature these plants have spread into the wild, often resulting in many of our native species being unable to grow, thus reducing the biodiversity of our river banks.

In the Nith area, as elsewhere, the most effective method to control Japanese knotweed and Giant hogweed is by injecting Roundup (Glyphosate) into their stems, with encouraging results.

Japanese knotweed

The treatment of Japanese knotweed started upstream of New Cumnock and systematically moved south, down the catchment, to Dumfries. This work will continue down through Dumfries and along the coast of the estuary. Treatment has also begun on the River Cairn.


  • Green cane-like stems with red specks that can reach up to 2 - 3m tall.
  • Heart shaped green leaves up to 120mm long.
  • Creamy white flowers from August to October
  • Roots consist of rhizomes that can reach up to 3m deep!

Control Options:

  • Applying with a commercial glyphosate-based chemical such as Roundup ProBiactive is highly effective
  • Spraying - This should take place 4 times per year for a total of 4 years. The initial spraying should commence in May when the plant is 3 foot tall, and the final spraying should be in September just before the plant dies back for the winter. The two other sprayings should be within these dates during the summer.
  • Stem Injection - This should be carried out once a year for a total of two years. This should take place in August time when the plant is at its strongest to support the treatment. A follow up visit should take place to treat any stems missed.

Do's and Don'ts!:

  • Never throw away or fly tip plant material or soil - under the Wildlife and Countryside Act 1981, it is an offence to plant or otherwise encourage the growth of Japanese Knotweed.
  • Never strim, flail, mow or chip Japanese Knotweed - pieces of stem as small as a fingernail can grow into new stems.
  • Scottish Environmental Protection Agency (SEPA) should be contacted before any chemical control takes place near water.
  • Removal of plant material off site must be carried out by a licensed carrier


Himalayan balsam

Although Himalayan balsam is an annual plant it is considered to be one of the hardest invasive species to control, due to its explosive method of distributing its seeds for metres around. The Nith Catchment Fishery Trust, following research elsewhere, will be experimenting to see if by using dilute concentrations of Roundup to destroy the Himalyan balsam, native flora will be able to thrive.


  • Stems are sappy and hollow in pinky-red colour. They can grow to 3m, being the tallest annual plant in Britain.
  • Spear-shaped leaves with serrated edges. Dark green with a dark red midrib up to 150mm long.
  • Flowers are slipper-shaped on long stalks. They are purplish-pink and flower from June to August.
  • Seeds are white, brown and black. They are produced from July to October with 4 - 16 per pod that explode, throwing seeds up to 20 foot.

Control Options

  • Spraying with a commercial glyphosate-based chemical such as Roundup ProBiactive is effective. This should be done when the leaves are fully out, but before flowering - typically in June
  • Cutting stems with a strimmer or pulling up hand before it flowers and sets seeds is successful. This grazing technique is highly effective.
  • Himalayan Balsam can be disposed of by leaving to dry out onsite or by burning.

Do's and Don'ts!

  • Never throw away or fly tip plant material or soil - under the Wildlife and Countryside Act 1981, it is an offence to plant or otherwise encourage the growth of Himalayan Balsam.
  • Scottish Environmental Protection Agency (SEPA) should be contacted before any chemical control takes place near water.
  • Do not touch the plant when loaded seed pods are showing - they will explode showering seeds. Be careful not to transport seeds to a new site. Seeds can be hidden in clothing or on your dog for example.

Giant hogweed

During 2011, all of the flowering Giant hogweed plants along the River Nith and Scaur were injected with Roundup, 52km of river bank. Giant hogweed flowers mature into seed heads with thousands of seeds each, which, once dispersed, can stay dormant in the soil for many years. This means that it is necessary to go back year after year and treat the newly emerging plants until the seed bank is exhausted.


  • Stems are hollow, green with dark or purple blotches and will grow up to 5m tall!
  • Leaves are dark green in a rosette with a jagged appearance and spiky at the ends. The lower leaves can be up to 1.5m long!.
  • Flowers are white with several hundred in large umbrella-like flower heads up to 50cm across, appearing from June - July.
  • Each flower will produce up to 50,000 seeds that are easily dispersed by water and can remain viable for up to 15 years

Control Options

  • Spraying with a commercial glyphosate-based chemical, such as Roundup ProBiactive is effective on Giant Hogweed. The plant needs to be sprayed once all the leaves are fully out, but before flowering. This is typically in June. Any re-growth can be sprayed later in the season. The plant should be controlled in 2 - 3 years, but will need future checking for any newly germinating seeds.
  • Cutting the stems before the plant flowers and sets seed is also an effective control option. This grazing-like method will stop the plant from producing seeds. This should be done for 2 - 3 years before achieving full eradication. Due to the health and safety issues with the 'skin burning' sap of Giant Hogweed, cutting should only be carried out by a qualified person.

Do's and Don'ts!

  • Never throw away or fly tip plant material or soil - under the Wildlife and Countryside Act 1981, it is an offence to plant or otherwise encourage the growth of Giant Hogweed.
  • Scottish Environmental Protection Agency (SEPA) should be contacted before any chemical control takes place near water.
  • Giant Hogweed should not be touched without protective clothing as contact with the sap can produce painful skin conditions

What can you do?

The Nith Catchment Fishery Trust are keen to hear from anyone that has reports of Japanese Knotweed, Himalayan Balsam or Giant Hogweed locations near watercourses within the Nith catchment area.

Dumfries and Galloway Council are equally keen to receive any roadside location reports by calling the main switch board on 030 3333 3000.

The Trust is now running a 'River Guardian' volunteer scheme to encourage interested helpers to take part in this important conservation project within the Nith catchment. A limited number of training opportunities are available in order to develop a strong team of volunteers to assist with ongoing monitoring and control.

If you wish to find out more information, or want advice on controlling these alien plant species, please contact Debbie Parke at:

The Nith Catchment Fishery Trust
37 George Street

Tel. 01387 740043

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