The Ternoise is what the Canche would be if someone had shrunk it by half and left the character intact. It rises above Saint-Pol-sur-Ternoise and runs quietly east to its confluence with the Canche near Hesdin, a pure chalk stream winding through water meadows and under willow tunnels. The water is stable, cold in summer, gin-clear after anything but the worst storms. Wild brown trout, mostly modest — 20–30cm is the average — but they hold in every likely seam and rise with conviction when the olives come off. Mayfly through late May, sedges in June, small spinners through July evenings. Access via the local AAPPMA. The beats are not long and the fish are not large, but this is jewel-box water, and people who fish it properly tend to come back.
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