Salmon run plankton. At this point the baby salmon are called "fry". At the end of the summer the fry develop into juvenile fish called "parr". Parr feed on small invertebrates and are camouflaged with a pattern of spots and vertical bars. They remain in this stage for up to three years. As they approach the time when they are ready to migrate out to the sea the parr lose their camouflage bars and undergo a process of physiological changes which allows them to survive the shift from freshwater to saltwater. At this point salmon are called "smolt". Smolt spend time in
Pink salmon estuaries, at about one-quarter gram in weight. The fish achieve sexual maturity in their second year of life. They return to freshwater in the summer or autumn as two-year-old adults. Pink and chum salmon sometimes interbreed in nature to form the hybrid known as the miko salmon; the hybrids are sterile. Pink salmon are coldwater fish with a preferred temperature range of 5.6 to 14.6 °C, an optimal temperature of 10.1 °C, and an upper incipient lethal temperature of 25.8 °C. The native range of the species is in the Pacific and Arctic coastal waters and rivers, from the Sacramento