The Chassezac is a small river that does a very dramatic thing: it starts on the schist of Mont Lozère, runs south through trout water that could sit anywhere in the Cévennes, and then cuts abruptly into the limestone to form the Gorges du Chassezac — a vertical-walled canyon that local kayakers speak about in tones of respectful fear. The trout fishing is in the upper reaches above the gorges and in the tributary streams that feed it. It is the kind of water where you park the car at a back-road bridge, walk upstream for half an hour, and then realise you probably won't see another angler all day. The usable beats are above Les Vans and upstream of the first hydroelectric barrage. The fish are small — six to ten inches is the honest range, with occasional better fish in the deeper pools — but they rise confidently to a well-presented dry in the right weather. March through early June is the window. After that, like most Cévennes water, the Chassezac thins out to a trickle and the fish retreat to the holding pools. The schist colour is always there, even at low water: dark water that looks almost peat-stained but isn't.

• Schist