Even though humans think they are very different from the cold-blooded, slimy, finned creatures that live in the water, their basic needs are the same. Even though fish live in the water, they still require adequate living space. Cover for juvenile and adult salmonids is important for protection from predators and to provide living space.
Salmonids use two forms of cover, overhead and submerged.
Overhead cover consists of riparian vegetation, overhanging banks, turbulent water, and logs. Submerged cover usually consists of large rocks, aquatic vegetation, logs, etc. Space requirements vary with species, age, and time of year. Space is generally made up of pools within the stream. In general, more space and food means more fish.