Steelhead, or steelhead trout, are the same species as rainbow trout (Oncorhynchus mykiss), except they have different life cycles. Where rainbow trout spend their entire life cycle in freshwater, steelhead, as a result of genetic modifications, are anadromous, that is, they spend parts of their life in fresh water and in saltwater.
Steelhead eggs are laid in fast-flowing, well-oxygenated, gravel-bottomed streams and rivers that empty into the Pacific. Once hatched, a steelhead spends one to three (or more) years in the river before undergoing physical changes that allow it to survive in seawater (smoltification). The smolt migrate downstream and enter the ocean where they live and mature for two or three years before returning to the river where they were born to spawn and begin the cycle again.
Unlike salmon, which die after spawning, steelhead are iteroparous and can spawn several time separated by months or years. Of the steelhead that survive to spawn once, about 20 to 30 percent return to the sea and manage to return and spawn a second time.
Steelhead migrate inland at different times of the year. Those returning to their birth rivers between November and April are fully developed when they leave the ocean and can begin to spawn as soon as they reach their spawning sites. These are known as “winter-run” steelhead. Those returning between May and October are called “summer-run” steelhead. The reproductive organs of summer-run steelhead are not fully mature when these fish enter the rivers. They mature in fresh water enroute to the spawning grounds.
Summer-run steelhead often return to rivers when water temperature is high and the water level is too low to permit the steelhead to navigate to their spawning grounds. These returning wild fish congregate in isolated, deep, cooler pools awaiting the return of fall rains and higher, colder water so they can navigate upstream to their spawning sites in the smaller tributaries. Often hundreds of fish congregate in these pools.
Unfortunately these large groups of fish are very attractive to poachers. Wild steelhead are already threatened and one act of vandalism can be devastating to their population. A “Fishwatch” program along the North and South Umpqua Rivers in Oregon has been in operation since 1993 to stop poaching of summer-run steelhead (also spring chinook and cut-throat trout). At the Big Bend Pool in the South Fork of Cedar Creek, where up to 600 steelhead congregate each summer, a “Fishwatch” steward camps each summer and protects the massed steelhead from harassment and poaching.
This picture was taken in early September at the Big Bend Pool. The steward said approximately 225 steelhead were gathered in the pool this year. Unfortunately I did not have the appropriate lens and filters with me, but the approximately 24 inch steelhead are visible. Seeing all those steelhead swimming in the pool was testimony to the value of conservation programs.