Shaded streams with permeable watersheds provide naturally resilient fish habitat refugia during heatwaves

Streamflow, dissolved oxygen, and water temperature underpin stream fish habitat suitability, so climate change could cause widespread habitat deterioration. Identifying stream characteristics that mediate habitat resilience to heatwaves will allow conservation effort prioritisation. Here, a set of readily applied metrics were used to assess hydrological and oxythermal responses of neighbouring salmonid streams, with distinctive geologies, soil‐types, and localised riparian shading, to periods of anomalously warm conditions. During heatwaves, low flows, warm‐water temperatures, and diel oxygen variability, associated with biogenic production and respiration, predominated. In a low‐shade stream lacking significant catchment water storage, high daytime (>22°C) and night‐time (>19°C) water temperatures and low early morning O2 concentrations ( 6 mg L−1; temperatures