Flowing out of Lago Toro beneath the granite towers of Torres del Paine, the Serrano carries meltwater from the Grey Glacier down to the Última Esperanza fjord, and the scenery alone would justify the trip before a single cast is made. Big brown trout hold in the deeper glacial-volcanic runs and back channels, joined by rainbows and chinook salmon lower in the system, and boat access is common given the river's size and the park's logistics. Streamers and sculpin patterns fished with some authority account for the better fish, particularly where the current softens below faster water. Wind off the Paine massif can be relentless, so timing around calmer weather windows matters as much as fly selection on a river this exposed.

• Volcanic glacial