Steelhead Trout

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Steelhead Trout

Oncorhynchus mykiss

StatusEndangered (Selected rivers in California and Washington); Threatened (Selected rivers in California, Idaho, Oregon, and Washington)
ListedJune 17, 1998 (Parts of California, Idaho, Oregon, and Washington); August 2, 1999 (Parts of Oregon and Washington)
DescriptionA trout that is steel blue above and silvery on the sides and belly in salt water and olive green on the back and less silver on the sides and belly in freshwater.
HabitatMay migrate as juveniles to the ocean and return to freshwater to spawn or may spend entire life in freshwater.
FoodTrout feed on aquatic and terrestrial insects, small fish insects and their eggs, and crustaceans.
ReproductionSpawns between December and June in freshwater.
ThreatsHabitat loss and degradation, disease, and dams making spawning sites inaccessible.
RangeCalifornia, Idaho, Oregon, Washington


At sea, Oncorhynchus mykiss (steelhead) are steel blue above with bright silvery sides and belly. Sharply defined black spots mark back, head, sides, dorsal, and caudal fins. The spots are small, rarely over 0.125 in (0.32 cm) in diameter, and highly variable in number. After entering freshwater, steelhead develop a broad pink or red stripe on each side of the body. This stripe fades away at the edges rather than being sharply outlined. In freshwater, steelhead gradually take on more of an appearance of a stream rainbow trout; the back gradually becomes olive green and the sides and belly become less silvery. Steelhead lack the red streaks beneath the jaw that characterize the cutthroat trout. The mouth lining is white. Juveniles are covered with small, oval to round parr marks. Steelhead typically do not have the pair of red or orange streaks on the underside of the jaw that are characteristic of cutthroat trout.

Most steelhead usually weigh less than 10 lbs (4.5 kg), but an individual weighing 42 lbs (19 kg) was caught in Alaska, and a 23 lb (10 kg) individual was caught in California. Immature sea-run individuals returning after less than a year in the ocean are called "half-pounders" and weigh from 0.5-1.5 lbs (230-680 g). The life span from this species is about seven years, but older individuals have been recorded.


The steelhead exhibit one of the most complex suites of life history traits of any salmonid species. Steelhead may exhibit anadromy (migration as juveniles from freshwater to the ocean, and then returning to spawn in freshwater) or freshwater residency (residing their entire lives in freshwater). Freshwater forms are usually referred to as rainbow or redband trout, while anadromous life forms are termed steelhead. Few detailed studies have been conducted regarding the relationship between resident and anadromous steelhead and, as a result, the relationship between these two life forms is poorly understood. Recently the scientific name for the biological species that includes both steelhead and rainbow trout was changed from Salmo gairdneri toO. mykiss. This change reflects the premise that all trout from western North America share a common lineage with Pacific salmon.

Steelhead typically migrate to marine waters after spending two years in freshwater. They then reside in marine waters for typically two or three years prior to returning to their natal stream to spawn as four-or five-year olds. Unlike other Pacific salmon, steelhead are iteroparous, meaning they are capable of spawning more than once before they die. However, it is rare for steelhead to spawn more than twice before dying; most that do so are females. Steelhead adults typically spawn between December and June. Depending on water temperature, steelhead eggs may incubate in redds (nesting gravels) for 45 days to four months before hatching as alevins (a larval life stage dependent on food stored in a yolk sac). Following yolk-sac absorption, young juveniles or fry emerge from the gravel and begin actively feeding. Juveniles rear in freshwater from one to four years, then migrate to the ocean as smolts.

Biologically, steelhead can be divided into two reproductive ecotypes, based on their state of sexual maturity at the time of river entry and the duration of their spawning migration. These two ecotypes are termed "stream maturing" and "ocean maturing." Stream maturing steelhead enter freshwater in a sexually immature condition and require several months to mature and spawn. Ocean maturing steel-head enter freshwater with well-developed gonads and spawn shortly after river entry. These two re-productive ecotypes are more commonly referred to by their season of freshwater entry.

Two major genetic groups or subspecies of steel-head occur on the West Coast of the United States: a coastal group and an inland group, separated in the Fraser and Columbia River basins approximately by the Cascade crest. These genetic groupings apply to both anadromous and non-anadromous forms of steelhead. Both coastal and inland steelhead occur in Washington and Oregon. California is thought to have only coastal steelhead while Idaho has only inland steelhead.

Under certain conditions, anadromous and resident steelhead are capable not only of interbreeding, but also of having offspring that express the alternate life history form; that is, anadromous fish can produce non-anadromous offspring, and vice versa. There is evidence that in very cold streams juvenile steelhead have difficulty attaining mean threshold size for smoltification and therefore do not emigrate downstream early in life. They are thermally-fated to a resident life history regardless of whether they were the offspring of anadromous or resident parents.

Freshwater populations can help buffer extinction risks to sea-faring steelhead populations by providing offspring that migrate to the ocean and enter the breeding population of steelhead, and by providing a reserve gene pool in freshwater that may persist through times of unfavorable conditions for anadromous fish. In spite of these potential benefits, presence of resident populations is not a substitute for conservation of anadromous populations. A particular concern is isolation of resident populations by human-caused barriers to migration.

Habitat and Distribution

Historically, steelhead were distributed throughout the North Pacific Ocean from the Kamchatka Peninsula in Asia to the northern Baja Peninsula. Presently, the species distribution extends from the Kamchatka Peninsula, east and south along the Pacific coast of North America, to approximately Malibu Creek in southern California. There are infrequent anecdotal reports of steelhead occurring as far south as the Santa Margarita River in San Diego County. Historically, steelhead likely inhabited most coastal streams in Washington, Oregon, and California as well as many inland streams in these States and Idaho. However, during the twentieth century, over 23 indigenous, naturally reproducing stocks of steelhead are believed to have been extirpated, and many more are thought to be in decline in numerous coastal and inland streams in Washington, Oregon, Idaho, and California. Forty-three stocks have been identified as being at moderate or high risk of extinction.

Of the 15 Evolutionary Significant Units (ESUs) the National Marine Fisheries Service has identified, two have been listed as endangered, seven as threatened, three as candidates for listing, and three as viable and not in danger of extinction.

One is the Lower Columbia River ESU listed as Threatened on June 17, 1998. This coastal steelhead ESU occupies tributaries to the Columbia River between the Cowlitz and Wind Rivers in Washington, inclusive, and the Willamette and Hood Rivers in Oregon, inclusive. Excluded are steelhead in the upper Willamette River basin above Willamette Falls, and steelhead from the Little and Big White Salmon Rivers in Washington. Rivers draining into the Columbia River have their headwaters in increasingly drier areas, moving from west to east. Columbia River tributaries that drain the Cascade Mountains have proportionally higher flows in late summer and early fall than rivers on the Oregon coast.

Steelhead populations in this ESU are of the coastal genetic group, and a number of genetic studies have shown that they are part of a different ancestral lineage than inland steelhead from the Columbia River Basin. Genetic data also show steelhead from this ESU to be distinct from steel-head from the upper Willamette River and coastal streams in Oregon and Washington.

There have been almost universal, and in many cases dramatic, declines in steelhead abundance since the mid-1980s in both winter-run and summer-run steelhead runs in the Lower Columbia River. Of 21 wild winter-run and summer-run steel-head stocks on the northern side of this region, only two are healthy and the remaining 19 are depressed. The primary exception to the declines is the Toutle River winter-run steelhead stock, which has increased following decimation by the eruption of Mount St. Helens in 1980. In some cases, chinook salmon populations in the same streams have not shown such dramatic declines. No clear explanation presently exists for these declines in steelhead, but not chinook salmon. The National Marine Fisheries Service (NMFS) is unable to identify any natural populations of steelhead in this ESU that could be considered healthy.

Summer-run steelhead are native to the Hood, Lewis, Washougal and Kalama Rivers in this ESU. However, summer-run fish have also been introduced into the Sandy and Clackamas Rivers. Furthermore, naturally spawning winter-run steelhead populations have been negatively impacted by introductions of non-native summer-run steelhead due to interbreeding and/or competition.

Another ESU is the Central Valley, California, ESU which was listed as Threatened on June 17, 1998. This coastal steelhead ESU occupies the Sacramento and San Joaquin Rivers and their tributaries. Excluded are steelhead from San Francisco and San Pablo Bays which are part of the Central California Coast ESU. In the San Joaquin basin, the best available information suggests that the current range of steelhead has been limited to the Stanislaus, Tuolumne, and Merced Rivers tributaries and the mainstream San Joaquin River to its confluence with the Merced River by human alteration of formerly available habitat. The Sacramento and San Joaquin Rivers offer the only migration route to the drainages of the Sierra Nevada and southern Cascade mountain ranges for anadromous fish. The distance from the Pacific Ocean to spawning streams can exceed 180 mi (290 km), providing unique potential for reproductive isolation among steelhead. The Central Valley is much drier than the coastal regions to the west, receiving on average only 4-20 in (10-50 cm) of rainfall annually. The valley is characterized by erosive soils, and native vegetation was dominated by oak forests and prairie grasses prior to agricultural development. The coastal vegetation is redwood forests. Steelhead within this ESU have the longest freshwater migration of any population of winter-run steelhead. There is essentially one continuous run of steelhead in the upper Sacramento River. River entry ranges from July through May, with peaks in September and February. Spawning begins in late December and can extend into April.

Ecological information provides additional insight into species diversity within this region. First, the Central Valley as a whole can be divided into three ecoregions based largely on elevation and associated changes in climate and rainfall: (1) A mountainous region, averaging about 3,280 ft (1,000 m) in elevation, that includes the headwaters of the Sacramento and tributaries to the San Joaquin Rivers; (2) a region of tablelands and hills at intermediate elevation, through which the tributary rivers flow; and (3) the valley itself, which includes broad, flat lands that border the Sacramento and San Joaquin Rivers. Geologically, the upper Sacramento River basin, which arises from the volcanic Cascade Range, differs from the lower Sacramento and San Joaquin River basins, which flow out of the northern and southern Sierra Nevada. The upper Sacramento River basin is also hydrologically distinct, and it supports native subspecies of resident steel-head. The southern part of the San Joaquin River basin is also very distinct ecologically, and genetic data indicate that, as a group, Central Valley steel-head are quite distinct from all coastal populations.

Various reports indicate that naturally spawning steelhead are distributed throughout a number of streams in the Central Valley region, but that they occur in small numbers. Furthermore, many populations are of non-native, mixed, or uncertain origin. In 1994, the recent total run size to the upper Sacramento River basin is probably less than 10,000 steelhead per year, and it is believed that less than 2,000 of those fish were the result of natural production from native populations.

Long-term declines in abundance, small population sizes in the Sacramento River, and the high risk of interbreeding between hatchery and naturally spawned steelhead as major concerns for steelhead in this region. Additionally, the significant loss of historic habitat, degradation of remaining habitat from water diversions, reduction in water quality and other factors, and the lack of monitoring data on abundance are other important risk factors.

A third ESU is the South-Central California Coast ESU, listed as Threatened on June 17, 1998. This coastal steelhead ESU occupies rivers from the Pajaro River, located in Santa Cruz County. Most rivers in this ESU drain the Santa Lucia Mountain Range, the southernmost unit of the California Coast Ranges. The climate is drier and warmer than in the north, which is reflected in the vegetation change from coniferous forest to chaparral and coastal scrub. Another biological transition at the north of this area is the southern limit of the distribution of coho salmon. The mouths of many of the rivers and streams in this area are seasonally closed by sand berms that form during periods of low flow in the summer. The southern boundary of this ESU is near Point Conception, a well-known transition area for the distribution and abundance of marine flora and fauna.

A fourth ESU is the Southern California ESU, which was listed as Endangered on June 17, 1998. This coastal steelhead ESU occupies rivers from the Santa Maria River, San Luis Obispo County to the southern extent of the species' range. Available data indicate that Malibu Creek, Los Angeles County is the southernmost stream generally recognized as supporting a persistent, naturally spawning population of anadromous steelhead.

Migration and life history patterns of southern California steelhead depend more strongly on rainfall and stream flow than is the case for steelhead populations farther north. River entry ranges from early November through June, with peaks in January and February. Spawning primarily begins in January and continues through early June, with peak spawning in February and March. Average rainfall is substantially lower and more variable in this ESU than regions to the north, resulting in increased duration of sand berms across the mouths of streams and rivers and, in some cases, complete dewatering of the marginal habitats. Environmental conditions in marginal habitats may be extreme, including elevated water temperatures, droughts, floods, and fires, and presumably impose selective pressures on steelhead populations. Steelhead use of southern California streams and rivers with elevated temperatures suggests that populations within this ESU are able to withstand higher temperatures than those to the north. The relatively warm and productive waters of the Ventura River resulted in more rapid growth of juvenile steelhead than occurred in northerly populations. However, relatively little life history information exists for steelhead from this ESU.

There are less than 200 adults comprising total run size for each of the six streams in this ESU. Populations have been extirpated from all streams south of Ventura County, with the exception of Malibu Creek in Los Angeles County.

The fifth steelhead ESU is the Upper Columbia River Basin ESU which is Endangered and was listed on June 17, 1998. This inland steelhead region comprises the Columbia River basin upstream from the Yakima River, Washington, to the U.S.-Canada border. The geology of these provinces is somewhat similar and very complex, developed from marine invasions, volcanic deposits, and glaciation. The river valleys in this region are deeply dissected and maintain low gradients except in extreme headwaters. The climate in this area includes extremes in temperatures and precipitation, with most precipitation falling in the mountains as snow. Stream flow in this area is provided by melting snowpack, groundwater, and runoff from alpine glaciers. It is a harsh environment for fish, much different from the benign, coastal streams of the Pacific Northwest. Life history characteristics for Upper Columbia River basin steelhead are similar to those of other inland steelhead ESUs; however, some of the oldest smolt ages for steelhead, up to seven years, are reported from this region. This may be associated with the cold stream temperatures. Based on limited data available from adult fish, smolt age is dominated by two-year olds. Steelhead from the Wenatchee and Entiat Rivers return to freshwater after one year in salt water, whereas Methow River steelhead are primarily two-ocean residents.

In 1939, the construction of Grand Coulee Dam on the Columbia River blocked over 1,120 mi (1,800 km) of river from access by anadromous fish. In an effort to preserve fish runs affected by Grand Coulee Dam, all anadromous fish migrating upstream were trapped at Rock Island Dam from 1939-1943 and either released to spawn in tributaries between Rock Island and Grand Coulee Dams or spawned in hatcheries and the offspring released in that area. Through this process, smolts of all anadromous salmonids, including steelhead, which were historically native to several separate subbasins above Rock Island Dam, were redistributed among tributaries in the Rock Island-Grand Coulee reach without regard to their origin.

Estimates of historical (pre-1960s) abundance are available from fish counts at dams. Counts at Rock Island Dam from 1933-1959 averaged 2,600-3,700, suggesting a pre-fishery run size in excess of 5,000 adults for tributaries above Rock Island Dam. Runs may already have been depressed by lower Columbia River fisheries at this time. The 1989-1993 average natural escapements numbered 800 for the Wenatchee River, and 450 for the Methow and Okanogan Rivers. Recent average total escapements for these stocks were 2,500 and 2,400, respectively. Average total run size at Priest Rapids Dam for the same period was approximately 9,600 adult steel-head.

Habitat degradation, juvenile and adult mortality in the hydrosystem, and unfavorable environmental conditions in both marine and freshwater habitats have contributed to the declines and represent risk factors for the future. Harvest in lower river fisheries and genetic homogenization from composite broodstock collections are other factors that may contribute significantly to risk to the Upper Columbia region.

Hatchery populations, considered part of this ESU, include the Wells Hatchery stock of summer-run steelhead. Although this stock represents a mixture of native populations, it probably retains the genetic resources of steelhead populations above Grand Coulee Dam that are now extinct from those native habitats. Operations at the Wells Hatchery have utilized large numbers of spawning adults and have incorporated about 10% of naturally spawning adults into the broodstock each year, procedures that should help minimize the negative genetic effects of artificial propagation. Because of the incorporation of naturally spawning adults into the hatchery broodstock and the large number of hatch-ery propagated fish that spawn naturally, there is a close genetic resemblance between naturally spawning populations and the Wells Hatchery stock that could be used for recovery purposes.

Another ESU is the Snake River Basin ESU, listed as Threatened on June 17, 1998. This inland steel-head region includes the Snake River basin of southeast Washington, northeast Oregon, and Idaho. The Snake River flows through terrain that is warmer and drier on an annual basis than the upper Columbia basin or other drainages to the north. Geologically, the land forms are older and much more eroded than most other steelhead habitat. The eastern portion of the basin flows out of the granitic geological unit known as the Idaho Batholith. The western Snake River basin drains sedimentary and volcanic soils of the Blue Mountains complex. Collectively, the environmental factors of the Snake River basin result in a river that is warmer and more turbid, with higher pH and alkalinity, than is found elsewhere in the range of inland steelhead. Snake River basin steelhead are summer steelhead, as are most inland steelhead, and have been classified into two groups, A-run and B-run, based on migration timing, ocean age, and adult size. Snake River basin steelhead enter freshwater from June to October and spawn in the following spring from March to May. Snake River basin steelhead usually smolt at an age of 2-3 years. Each has several life history differences, including spawning size, run time, and habitat type.

The Imnaha River Hatchery stock was recently founded from an undiluted stock with no previous history of non-native hatchery releases for the purpose of preserving the native genetic resources of this area. Therefore, this stock represents an important component of the evolutionary legacy of this ESU. Although the Oxbow Hatchery stock has been under artificial propagation for several generations and has been propagated almost entirely from hatchery-derived adults, this stock represents the only source of a unique genetic resource.

Prior to Ice Harbor Dam completion in 1962, there were no counts of Snake River basin naturally spawned steelhead. However, Lewiston Dam counts during the period from 1949-1971 averaged about 40,000 steelhead per year in the Clearwater River, while the Ice Harbor Dam count in 1962 was 108,000, and averaged about 70,000 until 1970. Although there is little information for most stocks within this ESU, there are recent run size or escapement estimates for several stocks. The 1990-1994 average escapement above Lower Granite Dam was approximately 71,000.

The Central California Coast ESU was listed as Threatened on June 17, 1998. Only two estimates of historical (pre-1960s) abundance are available: an average of about 500 adults in Waddell Creek in the 1930s and early 1940s, and an estimate of 20,000 steelhead in the San Lorenzo River before 1965. In the mid-1960s, 94,000 steelhead were estimated to be spawning in many rivers of this ESU, including 50,000 and 19,000 fish in the Russian and San Lorenzo Rivers, respectively. More recent estimates for the Russian River is 7,000 fish and 500 fish in the San Lorenzo River. These estimates indicate that recent total abundance of steelhead in these two rivers is less than 15% of their abundance 30 years ago. Additional recent estimates for several other streams indicate individual run sizes are 500 fish or less. Steelhead in most tributary streams in San Francisco and San Pablo Bays have been extirpated. Steelhead in this ESU may be exhibiting slight increases in abundance in recent years. Updated abundance data for the Russian and San Lorenzo Rivers indicate increasing run sizes over the past two to three years, but it is not possible to distinguish the relative proportions of hatchery and natural steelhead in those estimates. Additional data from a few smaller streams in the region also show general increases in juvenile abundance in the 1964-1975 period. Data from the Carmel River show increases in adult and juvenile steelhead abundance over the past two to five years.

The Middle Columbia River ESU listed as Threatened since August 2, 1999 occupies the Columbia River basin and tributaries from above the Wind River in Washington and the Hood River in Oregon upstream to, and including, the Yakima River, in Washington. Geology within this province is dominated by the Columbia River Basalt formation, stemming from lava deposition. This intermontane region includes some of the driest areas of the Pacific Northwest, generally receiving less than 16 in (40 cm) of rainfall annually.

Current population sizes are substantially lower than historic levels, especially in the rivers with the largest steelhead runs: the John Day, Deschutes, and Yakima Rivers. At least two extinctions of native steelhead runs have occurred in the Deschutes River basin. Trends in natural escapement in the Yakima and Umatilla Rivers have been highly variable since the mid to late 1970s, ranging from abundances of 2,000-3,000 steelhead during peaks that indicate relatively healthy runs to those that are cause for concern, approximately 500 fish during the low points.

The serious declines in abundance in the John Day River basin are especially troublesome because the John Day River has supported the largest populations of naturally spawning summer steelhead in the ESU. Populations in the Yakima River basin are at a small fraction of historical levels, with the majority of production coming from a single stream. The number of naturally spawning fish in the Umatilla River has been relatively stable in recent years, but this has been accomplished with substantial supplementation of natural spawning by hatchery-reared fish. Naturally produced steelhead have declined precipitously in the Deschutes River over the past decade. The most optimistic observation that can be made for steelhead in this area is that some populations have shown resiliency to bounce back from even more depressed levels in the past.

The Upper Willamette River ESU listed as Threatened on August 2, 1999 comprises the Willamette River and its tributaries, upstream from Willamette Falls to the Calapooia River. The Willamette River basin is geographically complex. In addition to its connection to the Columbia River, the Willamette River historically has had connections with coastal basins through stream capture and headwater transfer events.

Steelhead from the upper Willamette River are genetically distinct from those in the lower river. Reproductive isolation from lower river populations may have been facilitated by Willamette Falls, which is known to be a migration barrier to some anadromous salmonids. For example, winter steel-head and spring chinook salmon occurred historically above the falls, but summer steelhead, fall chinook salmon, and coho salmon did not.

The native steelhead of this basin are late-migrating winter-run, entering freshwater primarily in March and April, whereas most other populations of West Coast winter steelhead enter freshwater beginning in November or December.

As early as 1885, fish ladders were constructed at Willamette Falls to aid the passage of anadromous fish. The ladders have been modified and rebuilt, most recently in 1971, as technology has improved. These fishways facilitated successful introduction of Skamania stock summer steelhead and early-migrating Big Creek stock winter steel-head to the upper basin. Another effort to expand the steelhead production in the upper Willamette River was the stocking of native steelhead in tributaries not historically used by that species. Native steelhead primarily used tributaries on the east side of the basin, with cutthroat trout predominating in streams draining the west side of the basin.

Steelhead in the Upper Willamette River ESU are distributed in a few, relatively small, natural populations. Over the past several decades, total abundance of natural late-migrating winter steelhead ascending the Willamette Fails fish ladder has fluctuated several times over a range of approximately 5,000-20,000 spawners. However, the last peak occurred in 1988, and this peak has been followed by a steep and continuing decline. Abundance in each of the last five years has been below 4,300 fish, and the run in 1995 was the lowest in 30 years. Declines also have been observed in almost all natural populations, including those with and without a substantial component of naturally spawning hatchery fish.

The Oregon Coast ESU is a candidate for listing. This coastal steelhead occupies river basins on the Oregon coast north of Cape Blanco, excluding rivers and streams that are tributaries of the Columbia River. Most rivers in this area drain the Coast Range Mountains, have a single peak in flow in December or January, and have relatively low flow during summer and early fall. The coastal region receives fairly high precipitation levels, and the vegetation is dominated by Sitka spruce and western hemlock. Upwelling off the Oregon coast is much more variable and generally weaker than in areas south of Cape Blanco. While marine conditions off the Oregon and Washington coasts are similar, the Columbia River has greater influence north of its mouth, and the continental shelf becomes broader off the Washington coast.

The Oregon Coast ESU primarily contains winter-run steelhead; there are only two native stocks of summer-run steelhead. Summer-run steelhead occur only in the Siletz River, above a waterfall, and in the North Umpqua River, where migration distance may prevent full utilization of available habitat by winter-run steelhead. Alsea River winter-run steelhead have been widely used for steelhead broodstock in coastal rivers. Populations of nonanadromous steelhead are relatively uncommon on the Oregon coast, as compared with other areas, occurring primarily above migration barriers and in the Umpqua River basin. Age structure appears to be similar to other West Coast steelhead, dominated by four-year-old spawners. Iteroparity is more common among Oregon coast steelhead than in populations to the north.

Another candidate for listing is the Klamath Mountains Province (KMP) ESU. This coastal steel-head ESU occupies river basins from the Elk River in Oregon to the Klamath and Trinity Rivers in California, inclusive. Geologically, this region includes the KMP, which is not as erosive as the Franciscan formation terrains south of the Klamath River basin. Dominant vegetation along the coast is redwood forest, while some interior basins are much drier than surrounding areas and are characterized by many endemic species. Elevated stream temperatures are a factor affecting steelhead and other species in some of the larger river basins. With the exception of major river basins, such as the Rogue and Klamath, most rivers in this region have a short duration of peak flows. Strong and consistent coastal upwelling begins at about Cape Blanco and continues south into central California, resulting in a relatively productive nearshore marine environment.

Steelhead within this ESU include both winter-run and summer-run steelhead as well as the unusual half-pounder life history, characterized by immature steelhead that return to freshwater after only two to four months in saltwater, overwinterrun in rivers without spawning, then return to salt-water the following spring.

The Northern California ESU is also a candidate for listing which occupies river basins from Redwood Creek in Humboldt County to the Gualala River. Dominant vegetation along the coast is redwood forest, while some interior basins are much drier than surrounding areas and are characterized by many endemic species. This area includes the extreme southern end of the contiguous portion of the Coast Range Ecoregion. Elevated stream temperatures are a factor in some of the larger river basins (greater than 68°F [20°C]) but not to the extent that they are in river basins farther south. Precipitation is generally higher in this geographic area than in regions to the south, averaging 40-80 in (100-200 cm) of rainfall annually. With the exception of major river basins, such as the Eel, most rivers in this region have peak flows of short duration. Strong and consistent coastal upwelling begins at approximately Cape Blanco and continues south into central California, resulting in a relatively productive near-shore marine environment.

This region includes both winter-and summer-run steelhead, including what is presently considered to be the southernmost population of summer-run steelhead, in the Middle Fork Eel River. Half-pounder juveniles also occur in this geographic area, specifically in the Mad and Eel Rivers; however, adults with the half-pounder juvenile life history may not spawn south of the Klamath River basin. As with the Rogue and Klamath Rivers, some of the larger rivers in this area have migrating steel-head year round, and seasonal runs have been named. River entry ranges from August through June, and spawning from December through April, with peak spawning in January in the larger basins and late February and March in the smaller coastal basins.


Steelhead on the West Coast of the United States have experienced declines in abundance in the past several decades as a result of natural and human factors. Forestry, agriculture, mining, and urbanization have degraded, simplified, and fragmented habitat. Water diversions for agriculture, flood control, domestic, and hydropower purposes have greatly reduced or eliminated historically accessible habitat. Studies estimate that during the last 200 years, the lower 48 states have lost approximately 53% of all wetlands and the majority of the rest are severely degraded. Washington's and Oregon's wetlands are estimated to have diminished by one-third, while California has experienced a 91% loss of its wetland habitat. Loss of habitat complexity has also contributed to the decline of steelhead. For example, in national forests in Washington, there has been a 58% reduction in large, deep pools due to sedimentation and loss of pool-forming structures, such as boulders and large wood. Similarly, in Oregon, the abundance of large, deep pools on private coastal lands has decreased by as much as 80%. Sedimentation from land-use activities is recognized as a primary cause of habitat degradation in the range of West Coast steelhead.

Steelhead support an important recreational fishery throughout their range. During periods of drought conditions or summer low flow, the impacts of recreational fishing on trout stocks may be heightened. Although steelhead are not generally targeted in commercial fisheries, high seas drift-net fisheries in the past may have contributed slightly to a decline of this species in local areas, but could not be solely responsible for the large declines in abundance observed along most of the Pacific coast over the past several decades. A particular problem occurs in the main stem of the Columbia River where naturally spawned steelhead from the Upper Columbia and Snake River basin ESUs migrate at the same time and are subject to the same fisheries as hatchery-produced steelhead, chinook, and coho salmon. Incidental harvest mortality in mixed-stock sport and commercial fisheries may exceed 30% of naturally spawned populations.

Infectious diseases constitute one of many factors that can influence adult and juvenile steelhead survival. Steelhead are exposed to numerous bacterial, protozoan, viral, and parasitic organisms in spawning and rearing areas, hatcheries, migratory routes, and the marine environments. Specific diseases, such as bacterial kidney disease, ceratomyxosis, columnaris, furunculosis, infectious hematopoietic necrosis virus, redmouth and black spot disease, erythrocytic inclusion body syndrome, and whirling disease, among others, are present and are known to affect steelhead and salmon. Studies have shown that naturally spawned fish tend to be less susceptible to pathogens than hatchery-reared fish.

Introductions of non-native species and habitat modifications have resulted in increased predator populations in numerous river systems, thereby increasing the level of predation experienced by salmonids. Predation by marine mammals is also of concern in some areas experiencing dwindling steelhead run sizes.

Hatchery programs and harvest management have strongly influenced steelhead populations. Established hatchery programs that were designed to replenish stocks that had declined because of habitat losses have complicated the conservation efforts in recent times. Some of the hatcheries have maintained relatively pure stocks that are very similar to wild-run populations, while other hatcheries have re-stocked streams with hybrids that may or may not be genetically pure. Loss of genetic purity causes some populations to become less viable, more susceptible to disease, and less valuable for scientific research.

The departments of fish and game in Washington, Oregon, and California have adopted and are implementing natural salmonid policies designed to limit hatchery influences on natural, indigenous steelhead. Sport fisheries now focus on harvest of marked, hatchery-produced steelhead, and sport fishing regulations are designed to protect wild fish. While some limits have been placed on hatchery production of anadromous salmonids, more careful management of current programs and scrutiny of proposed programs are necessary in order to minimize impacts on listed species.

Natural climatic conditions have exacerbated the problems associated with degraded and altered riverine and estuarine habitats. Persistent drought conditions have reduced already limited spawning, rearing, and migration habitat. Climatic conditions appear to have resulted in decreased ocean productivity which, during more productive periods, may help offset degraded freshwater habitat conditions.

Conservation and Recovery

The state of Washington is currently in the process of developing a statewide strategy to protect and restore wild steelhead and other salmon and trout species. In 1997, the Joint Natural Resources Cabinet was created to restore healthy salmon, steelhead, and trout populations by improving those habitats on which the fish rely. The cabinet's current activities include development of the Lower Columbia Steelhead Conservation Initiative, which is intended to comprehensively address protection and recovery of steelhead in the lower Columbia River area.

The Oregon Plan for Salmon and Watersheds, established in 1996, calls for research to determine the decline of coastal coho and steelhead, most notably, those factors relating to harvest, habitat, and hatch-ery activities; a comprehensive monitoring plan; and tap local efforts to improve understanding of freshwater and marine conditions, determine populations trends, and evaluate the effects of artificial propagation in restoring the salmon.

In 1998, the state of Oregon implemented changes to its fishing regulations that will help conserve steelhead. These regulation include: (1) Elimination of steelhead retention fisheries; (2) creation of sanctuary areas for rearing steelhead where no angling is permitted; (3) elimination of the use of bait in trout fisheries that could negatively impact juvenile steelhead; (4) implementation of season closures for trout species during juvenile steelhead out-migration; and (5) modification of gear requirements to protect juvenile steelhead in trout fisheries. Current harvest regulations and hatchery programs will be modified in the future if monitoring results indicate that changes are needed.

The state of California's program for steelhead conservation consists of several major programs: (1) The CALFED Bay-Delta program; (2) the Governor's Watershed Restoration and Protection Council to implement the watershed planning and habitat; and (3) CDFG strategic management plans for steelhead in the and Northern California ESUs.

The plans for Klamath Mountain and Northern California steelhead identify a wide range of existing and new hatchery management measures that are intended to reduce the impacts of hatchery steel-head programs on wild steelhead populations in these ESUs. These measures include: requiring a minimum 6 in (15 cm) size before releasing hatch-ery fish; marking all hatchery fish and conducting spawning surveys to assess the extent hatchery fish stray into natural spawning areas; reducing hatch-ery releases if they are found to stray; placing a cap on hatchery production; and conducting regular health checks during each rearing cycle to detect and destroy diseased fish that cannot be effectively treated.

Significant steps have been taken over the past two years in the Central California Valley towards the largest ecological restoration project yet undertaken in the United States. The CALFED program in coordination with other Central Valley efforts have implemented numerous habitat restoration actions that benefit Central Valley steelhead. Emphasis has been placed on addressing tributary drainages with high potential for steelhead production.


Protected Resources Division
National Marine Fisheries Service, Northwest Region
525 N.E. Oregon Street, Suite 500
Portland, Oregon 97232-2737
Telephone: (503) 230-5400

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Building
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121


National Marine Fisheries Service. August 18, 1997."Listing of Several ESUs of West Coast Steelhead." Federal Register 62(159): 43937

National Marine Fisheries Service. March 19, 1998."Threatened Status for Two ESUs of Steelhead in Washington, Oregon, and California." Federal Register 63(53): 13347-13371.

National Marine Fisheries Service. March 25, 1999."Threatened Status for Two ESUs of Steelhead in Oregon and Washington." Federal Register 64(57): 14521.