The Altier is born under the summit of Finiels, culminating point of the department of Lozère with its 1699 m, in the heart of Mont-Lozère, in granitic ground.
After having descended the slopes of Mont Lozère, it follows a valley steeped in shale, before throwing itself after 30 km, in the reservoir of Bayard-Villefort which shelters huge trout of which some subjects trace the course of the Altier on a few kilometers at the time of spawning. The granitic pebbles offer multiple caches to the numerous trout, whose average size reaches 25 to 28 cm on the downstream course, the minnows, and also the big studs. A large population of chub, from the reservoir, is present but circumscribed to the immediate upstream of the reservoir.
The Altier is 1st category fishing river