Reported not to establish breeding populations if the peak emergence of fry corresponds to flood season and cold summer temperatures and if temperature does not fall below 13° C (Ref. 59043). Males mature generally at 2 years and females at 3. Spawning happens from November until May in the Northern hemisphere and from August to November on the Southern hemisphere. The size of the eggs depends on the size of the female. In captivity spawning is fostered by abdominal massage. Egg size 3-6 mm, fry length after hatching 12-20 mm. Hatchlings are well developed and equipped with a large yolk sac. The female finds a spot and digs a pit. While digging, an attendant male courts her or is busy driving away other males. As soon as the pit is completed, the female drops into it and is immediately followed by the male. The pair is side by side, they open their mouth, quiver and release egg and sperm. Females produce from 700 to 4,000 eggs per spawning event (Ref. 4706). At this point, a subordinate male moves in and releases sperm into the nest. The female quickly moves to the upstream edge of the nest and starts digging a new pit, covering the eggs. The whole process is repeated for several days until the female deposits all her eggs (Ref. 27547). Young fish move downstream at night, shortly after emergence (Ref. 4706). Reproductive strategy: synchronous ovarian organization, determinate fecundity (Ref. 51846).
- Gall, G.A.E. and P.A. Crandell 1992 The rainbow trout. Aquaculture 100:1-10. (Ref. 4706)
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