The Chinook Salmon have seasonal runs in which all adults return to their natal streams and spawn at approximately the same time of year. Sexual maturity can be anywhere from 2-7 years, so within any given run, size will vary considerably. Salmon are semalparous, and shortly after spawning they die.
After migrating back to the exact place of birth, with very little straying, the adults span in the course gravel of the river. The female first digs a redd in the gravel with an undulating motion of her tail, while the male stands guard. The female then deposits her eggs (3000-14000) in the nest, sometimes in 4-5 different packets within a single redd. The male then deposits his sperm, and both parents guard the redd until they die, sometime within the next 25 days. Spawning is timed so that the fry will emerge in the spring, the time where the stream has the highest productivity.
Many streams have more than one run, with each run going to a slightly different location in the stream. In each location, different environmental factors will affect the timing of the run, all timed so the fry emerge in the spring. For example, in a stream with spring and summer runs, often the spring run will go to higher elevation and with the colder temperature, the eggs will take longer to hatch (Pacific States Marine Fisheries Commission, 1996; National Wildlife Federation, 2002; Matthews and Waples, 1991; NOAA, 2001; Delaney and ADFG, 1994; Government of Canada, 2002).
Key Reproductive Features: Semelparous; Seasonal breeding; Gonochoric/gonochoristic/dioecious (sexes separate); Sexual; Fertilization; Fertilization :: External; Oviparous
Spawning season varies, but the most common runs are in the summer and fall with some streams having runs in the spring and winter as well.
There is no parental care in Chinook Salmon, as both parents die before the young emerge. However, the decomposing adult carcasses provide necessary nutrients to the eggs and fry.
Parental Investment: No parental involvement