Guss

For the most part the first flies to come off will be small stones and as the water warms the get bigger and bigger. The best way to tell a stone in the air is that they have 4 wings and look like one or them old biplanes. From a distance a stone looks alot like a cadis, but it seems to early for them, butyour area may be different. On a side note I sawsome small stoneshatch abot 2 weeks ago,we still had feetof snow on the ground and the river was still iced up, tuff little guys.

At first I would have said Blue wing Olives (small may flies), but that is just a guess.Next time get a pic of the bugs and I can help you more.