Patagonian fjord ecosystems might experience new scenarios due to climate variability (decreasing annual precipitation and glacier melting) in the short term. Herein, we studied the seasonal variability of the Puelo River regime (North Patagonia, 1944–2007, mean streamflow: 650 m 3 /s) and analyses its influence on surface salinity, temperature and dissolved oxygen in the well‐stratified Reloncaví Fjord (41.5°S). Our results s...