In reply to Morgan Woods:
To my knowledge,there are only two species of fish in the Sierra de Guara,
brown-trout and barbel.On the western-side,the Vadiello lake is stocked with rainbow-trout.Great climbing,too,on pudding-stone,just like Riglos!I've done a few "dry" canyons in that area,that involved swimming/floating across the lake to the start!Great fun!
Many of the canyons in the Monte Perdido area are in the National Park and sadly out of bounds.The Rio Bellos(canyon de Anisclo)was a great descent,plenty of water,even in the height of summer.Alas,also full of BIG
trout!My favourite in the area is the Miraval gorge(Rio Yaga),on the eastern edge of the park.Nothing technical,but usually plenty of water and great fun(also plenty of trout!).