Stoneflies
Gammarids
That's the first thing to know. It runs about twenty-five kilometres from Course to Montcavrel before joining the Canche near Estrée, and there are stretches where you can step across it without getting your knees wet. But every inch of it holds wild brown trout — genuine chalk-stream fish, stable-temperature, clear-water, selective. The canopy is close and the casting awkward, and the fish that live here have seen every fly in the box. Olives and caddis through spring, terrestrials when the water gets low in July and August. A proper short-rod river: a 7ft 3-weight, a long leader, and the patience to work one pool at a time. Not a beginner's water. The people who fish it are people who have learned to fish somewhere bigger and then looked for something harder.
In chalk-spring and karst trout systems, generally stable temperatures broaden olive and other mayfly activity from early spring into autumn, with strong evening caddis, steady subsurface scuds and buzzers where clear groundwater and weedbeds develop, and terrestrials from meadow and woodland banks rounding out the food calendar, depending on how fast each river drops and clears after rain.
- Chalk