Turkish freshwaters as a case of rising invasion risk of aquarium fishes under climate change.

Abstract

Climate change is expected to increase the invasiveness of non-native aquarium fish, yet national assessments rarely consider future warming conditions. We screened 46 popular ornamental freshwater fish imported into Türkiye for invasion risk. Each species received a Basic Risk Assessment (BRA) score under current conditions and an adjusted Climate Change Assessment (CCA) score under regional warming scenarios. The BRA classified 12 species (26.1%) as high risk, while under the CCA, this rose to 16 species (34.8%). Four species, namely goldfish Carassius auratus, common carp Cyprinus carpio, vermiculated sailfin catfish Pterygoplichthys disjunctivus, and leopard pleco P. gibbiceps, reached very high-risk status. Climate change adjustment resulted in an increase in the basic scores for 34 species, a decrease for three, and no change for nine. Seven species achieved the maximum increment of + 12 under predicted climate change conditions. Our results show that marginal habitats, such as thermal springs and effluent canals, could become suitable for these species, even as water stress in Central Anatolia threatens both native and invasive species. We recommend dynamic, climate-aware risk protocols, combined with empirical validation via field and eDNA monitoring, and a precautionary ‘whitelist’ import system based on robust risk screening protocols as applied in this study.