Salmon are masters of osmoregulation. They are able to control both body fluids and ions during the transition from fresh water to salt water and back again. Young salmon, called smolt, are born of eggs hatched in freshwater and must prepare for life in the salty ocean. The young salmon will soon be bathed in ocean water that is about three times as concentrated as its body fluids, meaning that it will tend to lose water to its surroundings all of the time. All BUT ONE adaptation helps the salmon survive the change from fresh water to salt water.