Native fish introduced to control invasive species in Carmarthenshire

The carefully planned introductions of European perch (Perca fluviatilis), have taken place at five sites in the county: Sandy Water Park; Morolwg, Ashpits, Lower Lliedi reservoir in Llanelli, and a private pond in Cynheidre.

Their introduction follows extensive research into predator-prey relationships. Perch, a native species, have been identified as a natural predator of Topmouth Gudgeon (Pseudorasbora parva) and provide an effective method of population control without the need for chemical intervention.

Topmouth Gudgeon is classified as a ‘Category 5 Species’ under the Import of Live Fish Act 1980 (ILFA), indicating it is one of the most potentially damaging non-native fish to invade Western Europe. Its presence threatens native wildlife and habitats, and its rapid spread could have serious national ecological consequences.

The evidence-based control programme has been funded by Welsh Government and developed by NRW working closely with Carmarthenshire County Council, Llanelli Rural Council, Swiss Valley Angling Association, and a private landowner.

Beth Greenfield, Specialist Advisor for Invasive Non-native Species (Inns) management, NRW, said: “By introducing a natural predator, we are taking a proactive and sustainable approach to managing invasive fish populations while supporting native biodiversity.

“While chemical treatment is the most effective method for managing Topmouth gudgeon in the UK, these particular sites have been evaluated and found unsuitable for such measures due to their size and connectivity with other water bodies. In these circumstances, the use of perch offers a viable alternative to managing the invasive fish population.

“This initiative is based on rigorous scientific research, and our team will closely monitor the effectiveness of the approach through regular surveys and advanced molecular analysis techniques.”

NRW say that local anglers and residents may notice increased activity around these water bodies, including the presence of its teams conducting fish introductions, setting up monitoring equipment, and performing regular ecological surveys. NRW say the community’s cooperation and support are invaluable in protecting local aquatic ecosystems.

(Lead image: Natural Resources Wales)

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