East of Coyhaique the country opens into steppe, and the Ñirehuao changes character with it — a slow, meandering, spring-creek-style river winding through open grassland rather than crashing off the mountains. The clear, gentle current makes for genuine sight-fishing: browns holding in undercut banks and weed margins, visible and often maddeningly selective, which suits careful dry-fly and terrestrial presentations far more than blind streamer work. Foam hoppers and ants fished on a long, fine leader are the tools of the trade here, and a good pair of polarised glasses matters as much as any fly box. It's a different kind of Patagonian trout fishing — technical, quiet, and closer to English chalk stream sport than the region's big glacial rivers.

• Volcanic glacial