Coho Salmon Life History

The coho salmon life history is relatively straight-forward. Smolts typically migrate to sea in the spring of their second year, spend 16-20 months rearing in the ocean, then return to freshwater as three-year-old adults. A returning adult may measure more than two feet in length and weigh an average of eight pounds. After the first summer at sea, a small proportion of the males reach early sexual maturity and return that fall as two-year-old "jacks." These jack returns have proven to be a fairly accurate predictor of adult abundance the following year, and serve as a key component for setting ocean coho fishing regulations.

Oregon is on the southern range of coho production that extends from Point Hope, Alaska to Monterey Bay, California. Scientists have identified wild coho populations in Oregon coastal rivers ranging from the Necanicum River, at Seaside, on the north to the Winchuck River near the California border. Together, these populations comprise a group of fish known as Oregon Coastal Natural coho, or OCNs. Most of these fish originate in waters from the Coquille River north to the Nehalem River. Three central-coast lake basins (Siltcoos, Tahkenitch and Tenmile) are also important coho producers.

While coho also live in some south-coast rivers, such as the Rogue, their numbers have been historically small compared to waters farther north.

----------- Habitat Requirements -----------

Nature tends to fill niches. While the larger chinook salmon requires big water, often low in a watershed, for spawning, coho are drawn to the next level of tributaries. A checklist of typical coho fresh water habitat follows.

* Small, relatively low-gradient tributary streams for spawning and juvenile rearing
* May use lakes for rearing where available
* Pea to orange-size spawning gravel
* Over-winter primarily in off-channel alcoves and beaver ponds, where available.
* Prefer complex instream structure (primarily large and small woody debris) and shaded streams with tree-lined banks for rearing.