Predicted habitat shifts and conservation priorities for climate-sensitive fish in mountain rivers across a climatic transition zone under future climate change

Identifying suitable habitat shifts and climate refugia under climate change is essential for the conservation of freshwater fish, particularly in mountainous river systems. However, there is a lack of comprehensive evaluation frameworks to quantitatively assess the degree to which regional fish assemblages are affected. In addition, asymmetric habitat shift patterns in fish populations of mountainous rivers remain insufficiently explored. To address these gaps, we developed a climate-responsive evaluation framework—CR-TOPSIS—based on the Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS), and applied it to assess current and future habitat changes for the Top 15 climate-sensitive species and other key protected species in the Qinba mountainous region, integrating environmental DNA surveys and targeted traditional capture, cross-validated against regional checklists and expert review with MaxEnt modeling. Projections were made under two climate scenarios (SSP126 and SSP585) for the period 2070–2100. Results indicated pronounced asymmetric habitat shift patterns, with leading-edge expansion consistently exceeding trailing-edge contraction across climate scenarios. Species distribution centroids exhibited a clear northward shift, averaging 1.76 km under SSP126 and 2.64 km under SSP585, reflecting enhanced redistribution under stronger warming. Coldwater and bottom-dwelling species experienced disproportionate habitat loss under high-emission scenarios, whereas eurythermal and pelagic-spawning species showed comparatively higher adaptive potential. Core climate refugia, defined by 100% spatial overlap across scenarios, covered approximately 0.51 × 10 ³ km² and were primarily concentrated along the midstream Hanjiang River and its tributaries, remaining stable under both climate pathways. This study demonstrates the utility of integrating molecular monitoring and species distribution models to detect climate-sensitive shifts, evaluate species vulnerability and conservation prioritization in montane freshwater ecosystems.