What To Look For First (4 of 12)
Trout can feed in water from riffles that are so shallow their backs are almost out of the water, to 20-foot deep pools. But in general, you'll find most trout feeding in water that's from about two to six feet deep. In large, deep rivers, look for the shallower places, and in small shallow streams, look for the deep spots.
Unless you see fish feeding, or know where some trout feed from past experiences, look for structures in the current, including a rough bottom filled with large rocks, a bank lined with downed trees, or riffles at the heads of pools, and the smooth water at the tails of pools. In otherwise featureless water like the slow, middle portion of a pool, look for the central thread of current that runs down through the pool.
You can find this place by looking for the concentration of bubbles and other debris that run down through a pool. It may not always run right down the center of the pool, but can favor one side or the other. Or, it can be found in back eddies.
In the head of this pool, the riffle dumps swiftly into a deeper place. There's almost always a shelf at the head of a riffle that keeps trout out of the current, but gives them a constant supply of food overhead.
Also at the head of pools is a seam on either side of the current that provides that balance between fast water for feeding, and slower water for relief from the current. Often the heads of pools will be found at the bend in a river. And if the water's very fast, most fish will be found on the inside of the bend. But if the water is slower, more fish will be found in the middle of the river or on the outside of the bend, because that's where more food will be drifting.
The middle of a pool is often just plain harder to read. You don't have the same distinct features as at the head of the pool, so you have to look further. Look for bigger rocks, either above the surface, or swirls on the surface that show larger submerged rocks. Don't forget that the swirl caused by a submerged rock will be downstream of the rock itself. And trout are more likely to be ahead of the rock than behind it.
So, lead this plume of water generously when you cast your fly. Watch for that bubble line, because all the food drifting down through the pool will be concentrated near it, and so will the fish. Don't forget the banks. Look for water along the banks that is between two to six feet deep, and then look for logs, rocks, shade, or tiny projections in the bank that provide protection from current and predators.