Trophic interactions and climate-driven range dynamics of native and invasive catfish in freshwater ecosystems

Invasive species and climate change are among the most significant drivers of biodiversity loss in freshwater ecosystems, yet their combined effect on predator-prey dynamics remains insufficiently characterised. Here, we assess the trophic interactions and climate-driven range dynamics of two large-bodied catfish—the non-native African catfish, Clarias gariepinus and the native Wels catfish, Silurus glanis—in a thermally stable freshwater system in Türkiye. Using comparative functional response experiments and stable isotope analysis, we quantified predation patterns on a native prey species, Alburnus escherichii and a widespread non-native prey, Carassius gibelio. Both predators exhibited feeding efficiency on the native prey, with C. gariepinus demonstrating consistently greater consumption rates and potential ecological impact, particularly under warmer conditions. Ecological niche models projected range expansion for both catfish species under future climate scenarios, with increasing habitat overlap that may elevate the likelihood of interspecific interactions and exacerbate predation pressure on native fish communities. Our findings demonstrate how warming conditions can reinforce the ecological impacts of an invasive predator while altering its spatial interactions with native species, underscoring the urgent need to integrate experimental, field-based, and modelling approaches to anticipate climate-amplified invasion risks in freshwater ecosystems.