An alien non-native species is a species which is not native to the local area / region or the UK. 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 writing Biosecurity Plans to help address these concerns in their local areas
Anglers have a key role to play in identifying, reporting and ensuring they do not intentionally or accidently introduce or spread damaging alien species.
North American Signal Crayfish - picture courtesy of Keith Kirk
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 many UK 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 ELIA 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 SNH, ELIA and GFT.
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.