Caddisflies
Gammarids
The Béthune and the Eaulne are the two headwater rivers that join at Arques-la-Bataille to form the Arques proper, and each of them on its own is worth a day's fishing. The Béthune runs down from Neufchâtel-en-Bray through Bellencombre and Saint-Saëns, a proper chalk stream with cold stable water and a wild brown trout population throughout — nothing large, but honest and consistent. The Eaulne is shorter and quieter, rising near Londinières and running parallel to the Béthune before they meet. Both rivers get occasional sea trout running up from the Arques in autumn, and both hold grayling in the steadier pools. Olives from March, mayfly in the second half of May, summer caddis. AAPPMA beats through most of the fishable length. If you've fished the Arques itself and want to trace the river back to its sources, this is where it comes from.
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