Status Review of West Coast Steelhead from Washington, Idaho, Oregon, and California
Peggy J. Busby, Thomas C. Wainwright,
Gregory J. Bryant*, Lisa J. Lierheimer,
National Marine Fisheries Service
"Among these fishermen one occasionally hears more or less protracted discussions as to whether the fish are trout or steelheads, whether they belong to the same species as the larger steelheads which enter the river, whether they differ from the smaller stream trout, whether they differ from the steelheads of other rivers, what is a steelhead anyway..." (Snyder 1925, p. 50).
National Technical Information Service
U.S. Department of Commerce
5285 Port Royal Road
Springfield, VA 22161
Appendix A - Samples of Oncorhynchus mykiss used in Genetic Analyses
Appendix B - Petitioned Steelhead Populations Listed by Evolutionarily Significant Unit
Appendix C - Steelhead Artificial Propagation Facilities
Appendix D - Releases of Hatchery Steelhead
Appendix E - Steelhead Abundance Data
Appendix F - Glossary
In February 1994, the National Marine Fisheries Service (NMFS) received a petition seeking protection under the Endangered Species Act (ESA) for 178 populations of steelhead (anadromous Oncorhynchus mykiss) in Washington, Idaho, Oregon, and California. At the time, NMFS was conducting a status review of coastal steelhead populations (O. m. irideus) in Washington, Oregon, and California. In response to the broader petition, NMFS expanded the ongoing status review to include inland steelhead (O. m. gairdneri) occurring east of the Cascade Mountains in Washington, Idaho, and Oregon. This report summarizes biological and environmental information considered by the Biological Review Team (BRT) that conducted the West Coast Steelhead Status Review.
The ESA allows listing of "distinct population segments" of vertebrates as well as named species and subspecies. The policy of the NMFS on this issue for anadromous Pacific salmonids is that a population will be considered "distinct" for purposes of the ESA if it represents an evolutionarily significant unit (ESU) of the species as a whole. To be considered an ESU, a population or group of populations must 1) be substantially reproductively isolated from other populations, and 2) contribute substantially to the ecological or genetic diversity of the biological species. Once an ESU is identified, a variety of factors related to population abundance are considered in determining whether a listing is warranted.
After considering available information on steelhead genetics, phylogeny and life history, freshwater ichthyogeography, and environmental features that may affect steelhead, the BRT identified 15 ESUs--12 for coastal steelhead and 3 for the inland form. The BRT reviewed population abundance data and other risk factors for these steelhead ESUs and concluded that five (Central California Coast, South-Central California Coast, Southern California, Central Valley, and Upper Columbia River) are presently in danger of extinction, five (Lower Columbia River, Oregon Coast, Klamath Mountains Province, Northern California, and Snake River Basin) are likely to become endangered in the foreseeable future, and four steelhead ESUs (Puget Sound, Olympic Peninsula, Southwest Washington, and Upper Willamette River) are not presently in significant danger of becoming extinct or endangered, although some individual stocks within these ESUs may be at risk. The BRT concluded that the remaining steelhead ESU (Middle Columbia River) is not presently in danger of extinction but was unable to reach a conclusion as to its risk of becoming endangered in the foreseeable future.
The BRT concluded that, in general, the ESUs described below include resident O. mykiss in cases where they have the opportunity to interbreed with anadromous fish. Resident populations above long-standing natural barriers, and those that have resulted from the introduction of non-native rainbow trout, would not be considered part of the ESUs. Resident populations that inhabit areas upstream from human-caused migration barriers (e.g., Grand Coulee Dam, the Hells Canyon Dam complex, and numerous smaller barriers in California) may contain genetic resources similar to those of anadromous fish in the ESU, but little information is available on these fish or the role they might play in conserving natural populations of steelhead. The status, with respect to steelhead ESUs, of resident fish upstream from human-caused migration barriers must be evaluated on a case-by-case basis as more information becomes available.
Coastal Steelhead ESUs
1) Puget Sound--This ESU occupies river basins of the Strait of Juan de Fuca, Puget Sound, and Hood Canal, Washington. Included are river basins as far west as the Elwha River and as far north as the Nooksack River. This ESU is primarily composed of winter steelhead but includes several populations of summer steelhead. The steelhead in this ESU generally smolt at age 2 years, whereas most steelhead in British Columbia smolt at age 3. Steelhead from this area are genetically distinct from those in other areas of Washington, both chromosomally and electrophoretically. Habitat in the Puget Sound region is dominated by glacial effects, including extensive alluvial floodplains, and the fjord-like structure of Puget Sound itself may promote distinctive steelhead migration patterns. Recent population trends within the Puget Sound ESU are predominantly downward; however, trends in the two largest stocks (Skagit and Snohomish Rivers) have been upward. The BRT was concerned about the large proportion of hatchery steelhead in Puget Sound and their origination primarily from a single stock; however, most hatchery fish appear to have advanced run timing and to be harvested prior to spawning, thus limiting their interactions with naturally spawning steelhead. Another concern of the BRT was the lack of information on the abundance and status of summer steelhead in this ESU.
2) Olympic Peninsula--This ESU occupies river basins of the Olympic Peninsula, Washington, west of the Elwha River and south to, but not including, the rivers that flow into Grays Harbor on the Washington coast. The Olympic Peninsula ESU is primarily composed of winter steelhead but includes several populations of summer steelhead in the larger rivers. Olympic Peninsula steelhead are genetically distinct from other steelhead ESUs; this isolation is also supported by zoogeographic patterns of other species of fish and amphibians, indicating a faunal shift in the vicinity of the Chehalis River Basin. Population trends within this ESU are generally upward, with some stocks declining. As was the case with the Puget Sound ESU, there is very little information regarding the abundance and status of summer steelhead in this region, and there is also uncertainty regarding the degree of interaction between hatchery and natural stocks.
3) Southwest Washington--This ESU occupies the tributaries to Grays Harbor, Willapa Bay, and the Columbia River below the Cowlitz River in Washington and below the Willamette River in Oregon. This ESU is primarily composed of winter steelhead but includes summer steelhead in the Humptulips and Chehalis River Basins. Genetic data show differentiation between steelhead of this ESU and those of adjacent regions. The ecological connectivity of the region occupied by the Southwest Washington ESU is demonstrated by similarities in riverine and estuarine ichthyofauna and current-driven sediment transfer from the Columbia River to Grays Harbor and Willapa Bay. Most population trends within this ESU have been declining in the recent past. There is very little information regarding the abundance and status of summer steelhead in this region, and there is also uncertainty regarding the degree of interaction between hatchery and natural stocks.
4) Lower Columbia River--This ESU occupies tributaries to the Columbia River between the Cowlitz and Wind Rivers in Washington and the Willamette and Hood Rivers in Oregon, inclusive. Excluded are steelhead in the upper Willamette River Basin above Willamette Falls (see ESU 5-Upper Willamette River), and steelhead from the Little and Big White Salmon Rivers, Washington (see ESU 13-Middle Columbia River ESU). This ESU is composed of both winter and summer steelhead. Genetic data show distinction between steelhead of this ESU and adjacent regions, with a particularly strong difference between coastal and inland steelhead in the vicinity of the Cascade Crest. The majority of stocks for which we have data within this ESU have been declining in the recent past, but some have been increasing strongly. However, the strongest upward trends are either non-native stocks (Lower Willamette River and Clackamas River summer steelhead) or stocks that are recovering from major habitat disruption and are still at low abundance (mainstem and North Fork Toutle River). The data series for most stocks is quite short, so the preponderance of downward trends may reflect the general coastwide decline in steelhead in recent years.
5) Upper Willamette River--This ESU occupies the Willamette River and its tributaries upstream from Willamette Falls. The native steelhead of this basin are late-migrating winter steelhead, entering fresh water primarily in March and April. This unusual run timing appears to be an adaptation for ascending Willamette Falls, which function as an isolating mechanism for upper Willamette River steelhead. Early migrating winter steelhead and summer steelhead have been introduced to the Upper Willamette River Basin; however, these non-native populations are not components of this ESU. Native winter steelhead within this ESU have been declining on average since 1971 and have exhibited large fluctuations in abundance. The main production of native (late-run) winter steelhead is in the North Fork Santiam River, where estimates of hatchery proportion in natural spawning range from 14% to 54%.
6) Oregon Coast--This ESU occupies river basins on the Oregon coast north of Cape Blanco; excluded are rivers and streams that are tributaries of the Columbia River (see ESU 3- Southwest Washington). Native Oregon Coast steelhead are primarily winter steelhead; native summer steelhead occur only in the Siletz and Umpqua River Basins. Recent genetic data for steelhead in this ESU show a level of differentiation from populations from Washington, the Columbia River Basin, and coastal areas south of Cape Blanco. Ocean migration patterns also suggest a distinction between steelhead populations north and south of Cape Blanco. Steelhead, as well as chinook (O. tshawytscha) and coho (O. kisutch) salmon, from streams south of Cape Blanco tend to be south-migrating rather than north-migrating. Most steelhead populations within this ESU have been declining in the recent past, with increasing trends restricted to the southernmost portion (south of Siuslaw Bay). There is widespread production of hatchery steelhead within this ESU, largely based on out-of-basin stocks, and approximately half of the streams (including the majority of those with upward trends) are estimated to have more than 50% hatchery fish in natural spawning escapements. Given the substantial contribution of hatchery fish to natural spawning throughout the ESU and the generally declining or slightly increasing trends, it is likely that natural stocks are not replacing themselves throughout the ESU.
7) Klamath Mountains Province--This ESU occupies river basins from the Elk River in Oregon to the Klamath and Trinity Rivers in California, inclusive. This ESU includes both winter and summer steelhead. Steelhead from this region are genetically distinct from populations to the north and south. The "half-pounder" life history is reported only from this region. The Klamath Mountains Province is a unique geographical area with unusual geology and plant communities. While absolute abundance of steelhead within the ESU remains fairly high, since about 1970 trends in abundance have been downward in most steelhead populations for which we have data, and a number of populations are considered by various agencies and groups to be at some risk of extinction. Declines in summer steelhead populations are of particular concern. This ESU was previously studied under a separate status review that was completed in December 1994 (Busby et al. 1994).
8) Northern California--This ESU occupies river basins from Redwood Creek in Humboldt County, California south to the Gualala River, inclusive, and includes winter and summer steelhead. Allozyme and mitochondrial DNA data indicate genetic discontinuities between steelhead of this region and those to the north and south. Freshwater fish species assemblages in this region are derived from the Sacramento River Basin, whereas streams to the north include fishes representative of the Klamath-Rogue ichthyofaunal province. Population abundances are very low relative to historical estimates, and recent trends are downward in stocks for which we have data, except for two small summer steelhead stocks. Summer steelhead abundance is very low. Risk factors identified for this ESU include freshwater habitat deterioration due to sedimentation and flooding related to land management practices and introduced Sacramento squawfish as a predator in the Eel River. For certain rivers (particularly the Mad River), the BRT is concerned about the influence of hatchery stocks, both in terms of genetic introgression and potential ecological interactions between introduced stocks and native stocks.
9) Central California Coast--This ESU occupies river basins from the Russian River to Soquel Creek, Santa Cruz County (inclusive) and the drainages of San Francisco and San Pablo Bays; excluded is the Sacramento-San Joaquin River Basin of the Central Valley of California. Mitochondrial DNA and allozyme data indicate genetic differences between the steelhead from this region and those from adjacent areas. Environmental features (e.g., precipitation patterns, vegetation, and soils) show a transition in this region from the northern redwood forest ecosystem to the more xeric southern chaparral and coastal scrub ecosystems. Steelhead populations within the major streams occupied by this ESU appear to be greatly reduced from historical levels; for example, steelhead abundance in the Russian River has been reduced roughly sevenfold since the mid-1960s, but abundance in smaller streams appears to be stable at low levels. The primary risk factor for this ESU is deteriorated habitat due to sedimentation and flooding related to land management practices. Uncertainty regarding the genetic heritage of the natural populations in tributaries to San Francisco and San Pablo Bays makes it difficult to determine which of these populations should be considered part of the ESU.
10) South-Central California Coast--This ESU occupies rivers from the Pajaro River, Santa Cruz County to (but not including) the Santa Maria River. Mitochondrial DNA data provide evidence for a genetic transition in the vicinity of Monterey Bay. Both mtDNA and allozyme data show large genetic differences between populations in this area, but do not provide a clear picture of population structure. The climate in this region is drier and warmer than it is to the north, resulting in chaparral and coastal scrub vegetation and stream mouths that are closed seasonally by sand berms. In addition to vegetation transitions, the northern end of this region is the southern limit of the distribution of coho salmon. The southern boundary of this ESU is near Point Conception, a well-recognized transition area for the distribution and abundance of marine flora and fauna. Total abundance of steelhead in this ESU is extremely low and declining. Risk factors for this ESU are habitat deterioration due to sedimentation and flooding related to land management practices and potential genetic interaction with hatchery rainbow trout.
11) Southern California--This ESU occupies rivers from the Santa Maria River to the southern extent of the species range. Steelhead occur at least as far south as Malibu Creek, Los Angeles County, and may have historically occurred as far south as the U.S.-Mexico border. Genetic data show large differences between steelhead populations within this ESU as well as between these and populations to the north. Average rainfall is substantially lower and more variable in southern California than in 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 lower reaches of these streams from late spring through fall. This affects steelhead migration patterns, as well as the ability to residualize and survive elevated water temperatures. Steelhead have already been extirpated from much of their historical range in this region. The BRT had a strong concern about the widespread degradation, destruction, and blockage of freshwater habitats within the region, and the potential results of continuing habitat destruction and water allocation problems. There was also concern about the genetic effects of widespread stocking of rainbow trout.
12) Central Valley--This ESU occupies the Sacramento and San Joaquin Rivers and their tributaries. Recent allozyme data show that samples of steelhead from Deer and Mill Creeks and Coleman National Fish Hatchery on the Sacramento River are well differentiated from all other samples of steelhead from California. 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 ocean to spawning streams can exceed 300 km, providing unique potential for reproductive isolation among steelhead in California. Steelhead have already been extirpated from most of their historical range in this region. Habitat concerns in this ESU focus on the widespread degradation, destruction, and blockage of freshwater habitats within the region, and the potential results of continuing habitat destruction and water allocation problems. The BRT also had a strong concern about the pervasive opportunity for genetic introgression from hatchery stocks within the ESU, and a strong concern for potential ecological interactions between introduced stocks and native stocks.
Inland Steelhead ESUs
13) Middle Columbia River--This ESU occupies the Columbia River Basin from above the Wind River in Washington and the Hood River in Oregon upstream to include the Yakima River, Washington. Steelhead of the Snake River Basin are not included. This ESU includes the only populations of winter inland steelhead in the United States, in the Klickitat River and Fifteenmile Creek. Some uncertainty exists about the exact boundary between coastal and inland steelhead, and the western margin of this ESU reflects currently available genetic data. There is good genetic and meristic evidence to separate this ESU from steelhead of the Snake River Basin. The boundary upstream of the Yakima River is based on limited genetic information and environmental differences including physiographic regions, climate, topography, and vegetation. All BRT members felt special concern for the status of this ESU, particularly Yakima River and winter steelhead stocks. Total steelhead abundance in the ESU appears to have been increasing recently, but the majority of natural stocks for which we have data within this ESU have been declining, including those in the John Day River, which is the largest producer of wild, natural steelhead. There is widespread production of hatchery steelhead within this ESU, but it is largely based on within-basin stocks. Habitat degradation due to grazing and water diversions has been documented throughout the range of the ESU.
14) Upper Columbia River--This ESU occupies the Columbia River Basin upstream from the Yakima River. All upper Columbia River steelhead are summer steelhead. The streams of this region that are utilized by steelhead primarily drain the northern Cascade Mountains of Washington State. Streamflow is supplied by snowmelt, groundwater, and glacial runoff, often resulting in extremely cold water temperatures that retard the growth and maturation of steelhead juveniles, causing some of the oldest smolt ages reported for steelhead and residualization of juvenile steelhead that fail to smolt. All anadromous fish in this region were affected by the Grand Coulee Fish Maintenance Project (1939 through 1943), wherein anadromous fish returning to spawn in the upper Columbia River were trapped at Rock Island Dam, downstream of the Wenatchee River. Some of these fish were then released to spawn in river basins above Rock Island Dam, while others were spawned in hatcheries and the offspring were released into various upper Columbia River tributaries; in both cases, no attempt was made to return these fish to their natal streams, resulting in an undetermined level of stock mixing within the upper Columbia River fish. While total abundance of populations within this ESU has been relatively stable or increasing, this appears to be true only because of major hatchery supplementation programs. Estimates of the proportion of hatchery fish in spawning escapement are 65% (Wenatchee River) and 81% (Methow and Okanogan Rivers). The major concern for this ESU is the clear failure of natural stocks to replace themselves. The BRT also had a strong concern about problems of genetic homogenization due to hatchery supplementation within the ESU. There was also concern about the apparent high harvest rates on steelhead smolts in rainbow trout fisheries and the degradation of freshwater habitats within the region, especially the effects of grazing, irrigation diversions, and hydroelectric dams.
15) Snake River Basin--This ESU occupies the Snake River Basin of southeast Washington, northeast Oregon, and Idaho. This region is ecologically complex and supports a diversity of steelhead populations; however, genetic and meristic data suggest that these populations are more similar to each other than they are to steelhead populations occurring outside of the Snake River Basin. Snake River Basin steelhead spawning areas are well isolated from other populations and include the highest elevations for spawning (up to 2,000 m) as well as the longest migration distance from the ocean (up to 1,500 km). Snake River steelhead are often classified into two groups, A- and B-run, based on migration timing, ocean age, and adult size. While total (hatchery + natural) run size for Snake River steelhead has increased since the mid-1970s, the increase has resulted from increased production of hatchery fish, and there has been a severe recent decline in natural run size. The majority of natural stocks for which we have data within this ESU have been declining. Parr densities in natural production areas have been substantially below estimated capacity in recent years. Downward trends and low parr densities indicate a particularly severe problem for B-run steelhead, the loss of which would substantially reduce life history diversity within this ESU. The BRT had a strong concern about the pervasive opportunity for genetic introgression from hatchery stocks within the ESU. There was also concern about the degradation of freshwater habitats within the region, especially the effects of grazing, irrigation diversions, and hydroelectric dams.
This document represents the combined efforts of dozens of people who submitted information on steelhead directly to NMFS; attended Biological and Technical Committee meetings in Washington, Idaho, Oregon, and California; and answered seemingly endless questions from the authors and biological review team (BRT) members on the telephone. The authors particularly wish to acknowledge Stevan Phelps and Steve Leider of the Washington Department of Fish and Wildlife for generous sharing of newly emerging genetic data, and Jennifer Nielsen of Hopkins Marine Laboratory for sharing her DNA studies in progress. We also wish to thank those that reviewed drafts of this and related documents.
Significant contributions in the compilation and analyses of data were made by Kathleen Neely, Ted Parker, and David Teel, all from NMFS Northwest Fisheries Science Center (NWFSC). The biological review team for this status review included Peggy Busby, Dr. Stephen Grabowski, Dr. Robert Iwamoto, Dr. Conrad Mahnken, Gene Matthews, Dr. Michael Schiewe, Dr. Thomas Wainwright, Dr. Robin Waples, and Dr. John Williams, from NMFS NWFSC; Greg Bryant and Craig Wingert from NMFS Southwest Region (SWR); and Dr. Reg Reisenbichler from the National Biological Service (NBS), Seattle.