Now, let me begin by being straight with you. I'm not going to tell you everything you need to know about what works, when, on the Thurso - otherwise where would the fun be! However, I will give you a lot of pointers in the right direction.
Between January and March you would be best to use between a 2" and 3" tubes with a barbless double. Much depends on river height, but generally fairly large tubes work well. If you like to fish a double at this time of year then a size 2 or 4 should suffice.
Once the season starts progressing you can decrease your fly size to around an 1"-1.5" tube and size 6 or 8 double. If the water height starts to drop away then very small doubles - 10's or 12's tend to work well, often forfeiting a tube for a small double or two..
Towards the end of the season you would do well to go back to slightly larger flies.
With regards to patterns, flies such as the Willie Gunn, Torrish, Green Highlander, Silver Wilkinson, Thunder & Lightning, Yellow & Orange, and Fast Eddie work well on tubes. Alley's Shrimps, Hairy Mairy, Stoats Tails, Thurso Dowg, Golden Demon, Munro Killer, Macartair, General Practitioner, Templedog, Kerrie's Killer, Red Demon, Copper King and Fast Eddie fish well as doubles.
View some well known patterns here
The best advice I can offer is to echo that of the late Davie Sinclair - "keep your flee in the water"
