Salmon are normally raised in net-pens, which vary in size and shape depending on the scale of the operation and other factors such as water depth and wave energy. The average dimensions of a typical square pen are 10 meters on a side by 4 meters deep, but circular designs can be up to 30 meters in diameter and 30 meters deep.
Pens normally consist of an inner containment net and an outer predator net.
Clearance between the predator net and the bottom helps to maintain water circulation, which distributes metabolic waste and excess feed. Pens are usually strung together, connected by walkways, to form a single system. Several systems may exist on one lease site. Eggs are hatched and fry are obtained from fresh water hatcheries for salmonids. Salmon smolts are generally transferred to net pens off-shore in the spring, where they are held until reaching harvest size.