Though deplored by some trout purists, the introduction of rainbows has made fly fishing available to many more anglers, and most reservoir anglers welcome the rainbow and the exciting sport it offers in a hundred subtly different ways in different conditions. Generally a far hardier fish than the brown trout, the rainbow can withstand high temperatures, low oxygen levels, and murky waters. It is also a far more active fish, being a free riser to the fly and living and moving in loose shoals, with a strong urge to migrate upstream for spawning, falling back into lakes or lower reaches for the rest of the season. At the extreme it is anadromous, like sea trout, migrating from dense to less dense water to breed.
When to use the dry fly
Rainbows often rise freely in boisterous weather, feeding well on the surface during high winds, following the wind lanes in large groups and fearlessly rising under the bows of the angler’s boat. They will often cruise upwind in such conditions, dropping into the depths when they come to the far shores, and then feed earnestly either in midwater, or on the bottom.
In calmer water, when the angler despairs of getting his wet flies to work without creating a heavy wake, the rainbows will often rise maddening at midges and other small flies on the surface, ignoring the wet flies offered by the fisherman. Then the dry fly is often useful. Takes are sudden, and the rainbow is usually moving fast when it hits the fly. Smashtakes occur in these conditions, even when the cast is realistically heavy. The angler should not let his rod be pointing at the fly, for the shock must be absorbed by the rod when the fish takes.