Invasive Fish Species and Native Welfare Impacts

Invasive fish such as signal crayfish, topmouth gudgeon, and wels catfish threaten native aquatic ecosystems and impose significant welfare costs on native species through predation, competition, and disease transmission.

Key Facts

Signal crayfish carry crayfish plague which has eliminated native white-clawed crayfish from most of their UK range
Topmouth gudgeon can devastate zooplankton communities, destabilising whole pond ecosystems
Wels catfish have established in UK rivers, potentially preying on waterfowl and small mammals
Invasive fish are among the top five drivers of freshwater biodiversity loss globally
The pet trade and angling are primary pathways for invasive fish introduction to new water bodies

Welfare Considerations

Invasive fish species impose significant welfare costs on native wildlife through predation, competitive exclusion, and disease. Native white-clawed crayfish experience rapid mortality from crayfish plague with no treatment available. Predation by invasive species on native fish, amphibians, and invertebrates represents large-scale ongoing suffering. Eradication attempts using rotenone or electrofishing are welfare interventions in themselves, causing acute distress to targeted and non-targeted species.

What You Can Do

Never release aquarium or pond fish into wild waterways under any circumstances
Clean, check, and dry all fishing and water sports equipment between water bodies
Report invasive species sightings to the GB Non-Native Species Information Portal
Support funding for native species arks where white-clawed crayfish are conserved in disease-free facilities