From June to late September, adults migrate upstream as develop secondary sexual characteristics are developed. The spine curves to a humpback, and the jaw lengthens. The timing of the migration depends on location and may be correlated with high water. During September to November in the headwaters of rivers, females build a redd, a deep trough, by displacing sand and gravel with their tail as they lie on one side. Males defend the female from other males. He follows the female into the redd after she drops into it, and with open mouths, the male and female will vibrate and release eggs and sperm. Several males may spawn with a single female. The female digs a new redd at the upstream edge of the previous redd thereby covering the fertilized eggs in the previously made redd. About 1200-1800 eggs are laid. After the yellow egg yolk is absorbed, the eggs hatch. Hatchings without a parr mark go to the ocean and grow for 16 to 18 months before returning to the same birthplace stream the following year. Survivorships rates are low. (For a Canadian river, survivorship is 1 - 25%). Adults live only a few weeks after they spawn.
- Bigelow, H.B. and W.C. Schroeder, 1953; Chyung, M.-K., 1977; Morrow, J.E., 1980; Page, L.M. and B.M. Burr, 1991; Scott, W.B. and E.J. Crossman, 1973.
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