About Steelhead

Steelhead are strong, acrobatic fish that can navigate small waterfalls to reach spawning grounds. Napa County Resource Conservation District.

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Steelhead Life-Cycle
Steelhead trout (Oncorhynchus mykiss) belong to the family Salmonidae which includes all salmon, trout, and chars. Steelhead are the anadromous form of rainbow trout, a salmonid species native to western North America and the Pacific Coast of Asia. The term anadromous refers to fish species born in the stream that migrate to the ocean for their adult phase, then return to fresh water to spawn. Steelhead are similar to some Pacific salmon in their life cycle and ecological requirements. They are born in fresh water streams, where they spend their first 1-3 years of life. They then emigrate to estuaries and ultimately to the ocean where most of their growth occurs. After spending between one to four growing seasons in the ocean, steelhead return to fresh water streams – often the stream where they began their lives - to spawn. Unlike Pacific salmon, steelhead do not necessarily die after spawning and are able to spawn more than once.

In Southern California, most steelhead spawn from December through April in small streams and tributaries where cool, well-oxygenated water is available year round. The female selects a site with gravel substrate where there is good flow through the gravel. She then digs a nest, called a redd, and deposits eggs, which the male then fertilizes. The eggs are covered by gravel and cobbles right after they are laid and fertilized.

Steelhead in Carpinteria Creek in 2008. Photo by Mark Capelli, NOAA.

The length of time it takes for eggs to hatch is heavily dependent on water temperature. Eggs hatch sooner in warmer water, but the young fish are smaller and generally have lower survival rates. If the temperature goes too high, eggs will not hatch at all. After hatching, the developing steelhead will remain in the gravel for another four to six weeks. During this time, they are called alevins and obtain nutrients from a yolk sack attached to their body. When they emerge from the gravel, they are called fry, and are able to catch their own food.
Newly emerged fry move to shallow, protected areas of the stream (usually in the stream margins). They establish feeding areas that they defend. Most juveniles can be found in riffles (a shallow stretch of a river or stream, where the current is above the average stream velocity and where the water forms small rippled waves as a result), although larger ones will move to pools.
Steelhead have a dual life history in which they can remain in their freshwater rainbow trout phase their entire lives, or can change into a smolt. A smolt is a juvenile fish. This is the stage in the life history of steelhead where young fish become physiologically adapted to saltwater and begin their trek to the salt water environment. The freshwater rainbow trout and saltwater steelhead forms co-exist as parts of the same population in many streams and rivers. In dammed rivers such as the Santa Ynez, Santa Clara and Ventura Rivers steelhead populations became landlocked above the dams and are forced to live in their freshwater “rainbow trout” phase. In these cases, ocean-run steelhead can no longer access the freshwater populations above dams, isolating the populations and further threatening the species.
Source (Adapted from):
Steelhead Restoration and Management Plan for California, by Dennis McEwan and Terry Jackson, CA Department of Fish and Game.
Click here to see a diagram of the Steelhead Life-Cycle in the City of San Luis Obispo’s brochure.

Steelhead facts

1. Steelhead are the fastest freshwater fish in on the west coast and are able to reach burst speeds of 21 feet per second. This speed is necessary to help steelhead swim upstream and over small waterfalls during and after winter storms.
2. Steelhead can reach 3-feet long and weigh over 20 pounds.
3. Southern steelhead are believed to be the ancestors of all other steelhead types found further north. Following the ice age steelhead inhabiting Southern California branched out to the north as rivers became ice-free, creating new steelhead sub-species (including populations in the Central Valley, Klamath River, and elsewhere).
4. The federal agency in charge of steelhead, the National Marine Fisheries Service, identified 15 geographically-based populations of steelhead on the West Coast. Of those, only the Southern California Steelhead is listed as federally Endangered. To learn more about steelhead recovery planning visit the website of the National Marine Fisheries Service.
5. The largest run of steelhead in Southern California is believed to have been over 30,000 adults in the Santa Ynez River before Bradbury Dam (Cachuma Reservoir) and other dams were built. In 2008, only 17 adult steelhead were documented in this river: a 99% reduction.

EDC’s steelhead protection and restoration work focuses on the federally Endangered Southern California Steelhead, which occurs in EDC’s southern service area of Santa Barbara and Ventura Counties, and the South Central California Coast Steelhead which occurs in EDC’s northern service area of San Luis Obispo County. Click here to learn more about EDC’s work to protect and recover steelhead.