Steelhead

Oncorhynchus mykiss

  • Endangered (southern steelhead), federal Endangered Species Act
  • Threatened (south-central steelhead), federal Endangered Species Act
  • Species of Concern, California Department of Fish & Game

Steelhead trout

Steelhead trout is an anadromous fish, meaning that it leaves its freshwater stream to mature in the ocean and then returns to its natal stream to lay its eggs (spawn). Steelhead is actually the same species as rainbow trout, but because steelhead spend most of their lives in the ocean, they take on a more silvery color than trout that remain in fresh water, and can grow to a much larger size. The fish are also related to salmon, but whereas salmon only spawn once and then die, steelhead spawn several times during their lives, returning to the ocean after each spawn.

The life history of a steelhead begins in the cooler headwaters of mountain streams, where during the winter the adults lay eggs in nests or “redds,” which the female digs in the gravelly substrate of the stream bottom with her tail. The eggs take about five to eight weeks to hatch, after which the young fish remain in the freshwater stream for about a year, finding refuge in deeper pools as temperatures warm in the summer. Storms in the following winter allow these young fish to migrate downstream, where they live in a coastal lagoon for another year or two, growing rapidly in this rich ecosystem. Around the end of the second or third year, these small steelhead will then find their way to the ocean when storms again break through the natural sand bar at the edge of the lagoon and open it to the ocean. At this same time, mature steelhead, which have spent the last 1-4 years at sea, fight their way upstream back to the headwaters of their natal stream to spawn.

Steelhead in the Los Padres National Forest

Map of steelhead streams using NOAA Fisheries data; spawning habitat in the upper reaches of these streams is primarily in the Los Padres National Forest (shown in green).

Here along the Central Coast, the Los Padres National Forest plays a very important role in the lifecycle of steelhead, as it provides some of the best spawning habitat in our region. Throughout the Los Padres, steelhead migrate up large rivers, such as the Santa Maria, Santa Ynez, and Santa Clara Rivers to the south, and the Carmel and Big Sur Rivers to the north, and find their way to inland streams, such as the Sisquoc River, Matilija Creek, Arroyo Seco, and Sespe Creek. All these rivers have their headwaters in the Los Padres National forest, where temperatures remain cool enough throughout the year to maintain flowing streams where adults can spawn and deep pools where fish can survive the summer heat and drought.

There are two distinct populations of steelhead in the Los Padres, which are viewed as ecologically significant and separate from the larger populations of steelhead in the Northwest. Some scientists believe that the most southern population of steelhead, the population found south of the Santa Maria River, is the source of the genetic material—i.e., the ancestor—of all the northern populations. This makes it very important in the long-term health of steelhead in general and in our knowledge and understanding of this species. The southern steelhead population also has a number of advantages over its northern cousins, which may be important in preserving this species in the face of a warming climate. Southern steelhead for example has a higher tolerance for warmer water than its northern cousins, and a faster rate of growth, so the fish can return to the ocean far quicker, before streams dry up. The second population in the Los Padres, found between San Luis Obispo County and Santa Cruz County, is similar to the southern steelhead population, but also shares some traits of more northern populations.

Threats to Steelhead

These two steelhead populations have both suffered severe declines over the last century (some estimates are that the southern steelhead population has been decreased by 99% of historic amounts) and as a result the southern population was classified as “endangered” and the central population as “threatened,” in 1998. Declines are due primarily to artificial barriers, such as dams, as well as water extraction and pollution of creeks and streams.

Dams and other barriers continue to pose the greatest threat to steelhead, as they block fish from reaching prime spawning habitat in the cooler, wetter headwaters of mountain streams. Water diversions for agriculture and increased urban water use, meanwhile, have led to streams drying up prematurely in the summertime. Whereas these streams may have at one time provided pools for adult and juvenile steelhead during the summer months, they now can trap fish, leaving both adult and juvenile fish high and dry. Additionally, with urban development has come channelization of streams, which also acts as a barrier to steelhead passage, as it spreads the water out and speeds up its velocity, making the river too fast and too shallow for fish to pass.

ForestWatch: Protecting Our Steelhead and Mountain Streams

ForestWatch is dedicated to protecting and restoring habitat for populations of steelhead found along the Central Coast. Seventy years ago, before the building of massive dams in our region, the Santa Ynez River and the Sisquoc River had the largest and second largest steelhead runs in Santa Barbara County, respectively, with fish numbering in the tens of thousands. Now, large dams that provide water supplies for domestic and agricultural use block many of these historic steelhead runs. Gibraltar and Cachuma Dams are direct obstacles to steelhead passage on the Santa Ynez River, while Twitchell Dam is a direct obstacle to steelhead passage to the Cuyama River, and also prevents steelhead access to the Sisquoc River in most years.

ForestWatch is working to modify water releases from Twitchell Dam to restore more consistent flows so that steelhead can access the Sisquoc River downstream. ForestWatch is also working to prevent a land transfer around Lake Piru, which would give away one mile of steelhead critical habitat in Piru Creek to a local water district. The exchange would also complicate efforts to facilitate steelhead passage around Santa Felicia Dam, which currently blocks historic steelhead migration from the Santa Clara River into Piru Creek.

ForestWatch continuously supports enhanced protection for steelhead streams in the Los Padres, including the addition of fish ladders to existing dams, the removal of defunct dams (like the Matilija Dam on Matilija Creek, and the Horse Canyon Dam in the Sisquoc River watershed). We also support efforts to add additional rivers in the Los Padres National Forest to the national list of Wild and Scenic Rivers, and work to protect sensitive habitats and potential areas for steelhead restoration. We hope that continued preservation and protection of steelhead spawning habitat throughout the forest can help “bring back the steelhead” and restore this species along California’s Central Coast.

More Information

Steelhead Restoration Projects in Los Padres National Forest