Description
Numerous small scales; one dorsal fin plus one adipose fin; no spines in fins; back and tail lack distinct large black spots; first gill arch has 18-28 short, stout, smooth gill rakers; upper side of large individuals is steel-blue, with black speckles; sides silvery; silvery to white belly; tips of caudal, anal, and pectoral fins tinged black in males. Spawning males are dark olive to black on the upper side, with vertical red or dusky bars or blotches on green sides and white-tipped anal and pelvic fins. Spawning females are similar but less distinctly marked. Young have 6-14 narrow, short parr marks on each side. Total length to around 102 cm.
Habitat
Chum salmon spend most of their lives (2-7 years, usually 3-5 years) in the ocean. Adults return to spawn in streams where they hatched, sometimes moving up to 2,000 km upstream in rivers lacking major barriers in Alaska and Canada but usually spawning not far from salt water (usually within 100 km). Spawning occurs in gravel riffles in rivers and streams of various sizes. The female digs a redd, or nest, by displacing gravel and making depressions in an area of about 2.25 sq meters (Moyle 1976).
Ecology
Transplanting attempts have been unsuccessful outside natural range.
Reproduction
In many areas, chum salmon enter streams in distinct seasonal runs (e.g., summer and fall). In Washington, spawning usually occurs in fall, October-December. In California, spawning has been observed from early August to early February. Spawning adults generally are 2-5 years old, sometimes up to seven years old. Adults die within about a week after spawning. Depending on water temperature, eggs hatch in several months, and the alevins complete yolk absorption within the gravel environment. Fry migrate directly to the sea soon after emergence, with a peak in April-May in Washington, spending relatively little time in fresh water.