They also need deeper pools to survive a winter with anchor ice covering the habitat, unless they are in the southern tail waters of America or other countries. In nature there are seldom any linear relationships. The trout who limit their diet to minnows, sculpins, crayfish and other trout are sometimes called sharks. This equates to how much riffled or white water there is on the stream. The pools below a riffle will have a higher O2 content than the pools above the riffle.
Shelter means several things to a trout.
Protection from predators and protection from the main current, but close enough to feeding lanes in the current so little energy is expended in the gathering of food. This conservation of energy is extremely important to a trout, the less energy spent on feeding the more energy to spend on growth, all trout want to grow larger. When food is plentiful and gathering energy out put is small, a trout can grow at a fast pace. The larger the trout, the better home he can claim for himself. We know how important a good food supply is but the food supply is intertwined with the need for shelter.