Adults develop secondary sexual characteristics during their upstream migration (Ref. 1998), which occurs any time from June to late September, depending on location (Ref. 27547). Male develop a humpback, an enlarged head and large teeth on both jaws that form a pronounced hooked type (Ref. 59043). The upstream run seems to be triggered by high water (Ref. 27547). Female builds the redd by lying on one side and using its tail, it displaces silt and light gravel to produce a deep trough. Male spends most of the time driving off intruding males. When the redd is completed, the female drops into it, followed immediately by the male. They open their mouths, vibrate and release eggs and sperm. In some cases, several males spawn with a single female. The eggs are then covered as the female digs a new redd at the upstream edge of the previous one. Adults live up to a few weeks after spawning before they die (Ref. 1998, 27547). Reported to die 10-20 days after spawning (Ref. 59043). About 1200-1800 eggs are laid. After hatching and the yellow egg yolk is absorbed, if the hatchling doesn't have a parr mark they go to the ocean and come again to the same birthplace stream the next year during spring after growing for 16-18 months. Survival rates are low, at 1-25% (taken from a Canadian river) (Ref. 12218). Reproductive strategy: synchronous ovarian organization, determinate fecundity (Ref. 51846).
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