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STEELHEAD
Oncorhynchus mykiss
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Endangered,
federal Endangered Species Act
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Threatened, federal Endangered
Species Act
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Species of Concern, California
Department of Fish & Game
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.
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).
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
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.
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