The female digs a nest (called a redd) in the gravel and then deposits her eggs and the male deposits sperm. After 90-150 days (depending on temperature) the eggs hatch, and the alevins (fry with yolksacs attached to the underside) stay in the gravel until the yolksac is used up. The fry then emerge from the gravel in the spring and feed and grow for a few months to two years, depending on the stream system. They then migrate downstream as smolts, following the natural current. The smolts undergo huge physiological changes in their transition from freshwater to salt water. They then spend the next 1-7 years growing and maturing at sea. Growth rates in the ocean are much faster, and perhaps as much as 99% of the somatic growth occurs as sea. Mature adults will then return to their natal streams to spawn. Once the adults have re-entered freshwater, they no longer feed, and they complete sexual maturation during the freshwater migration (Pacific States Marine Fisheries Commission, 1996; National Wildlife Federation, 2002; NOAA, 2001; Delaney and ADFG, 1994; University of California at Berkeley; Government of Canada, 2002; Ewing and Ewing, 2002; Satterfield and Finney, 2002).
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