After their emergence from the gravel, the fry depend basically on their eyes to locate and capture food. Important food items listed by most investigators are stonefly nymphs, mayfly nymphs, caddisfly larvae, blackfly larvae, and terrestrial insects. Imprinting A very complex interaction occurs between the young salmon and its environment. Every stream is unique. The quality of the water, therefore, differs from stream to stream and from one area of a stream to another.
Young salmon are able to detect immeasurable traces of elements present in their environment.
From the time the young fry emerges it is constantly receiving imprinting cues. The cues received from the water in one part of the stream are slightly different from those absorbed a little farther down or upstream. Throughout the freshwater rearing stage, which varies from species to species, the fry receive a succession of cues which may assist them in returning to their natal spawning grounds. Young salmon may undergo a series of imprinting processes. Biologists are still not certain exactly when the imprinting process begins.