Gammarus pulses on Upper Tweed tributaries
River Teviot dusk: Gammarus pulses unlock 45–90 minute trout window
On the River Teviot and nearby Upper Tweed tributaries a steady pulse of freshwater shrimp — Gammarus — triggers one of the season’s sharpest feeding windows. These shrimp live their whole lives in the stream, feeding on dead plant material, and when light falls they drift from margins into trout lanes; the result is sudden, localised surface activity.
Reading the shrimp lane
Watch for surface dimpling, tiny bow-waves in slow seams, and trout shifting from lies into the top 20–60 cm of water. The first rise forms repeating in the same 2–10 m mark a reliable shrimp-rich lane. Inside bends, tongue edges, undercut banks and gravel riffles dropping into 1–3 ft of softer water are the classic spots where shrimp are dislodged and intercepted.
The best window is the last 45–90 minutes before dark, especially after a calm day when margins loosen. Smaller brown trout feed higher and with confidence; larger fish sit in the dark edge off the main seam and take slightly deeper presentations. Rivers to watch include the Teviot, Ettrick, Yarrow and Leader Water where clarity lets anglers read these subtle cues.
Practical play calls for a light-tackle setup, long leader and subtle shrimp imitations or small nymphs fished upstream into the lane while standing low in waders. The sound of dusk on the Tweed — a soft bow-wave, a silver flash and a trout gone — marks the end of daylight and the start of a brief, brutal feeding spell.