U.S. Dept Commerce/NOAA/NMFS/NWFSC/Publications

NOAA-NWFSC Tech Memo-27: Status Review of West Coast Steelhead
Conclusions

The BRT concluded that of the 14 ESUs reviewed here, 5 ESUs are presently in danger of extinction: Central California Coast, South-Central California Coast, Southern California, Central Valley, and Upper Columbia River. Four were classified as likely to become endangered in the foreseeable future: Lower Columbia River, Oregon Coast, Northern California, and Snake River Basin. The Puget Sound, Olympic Peninsula, Southwest Washington, and Upper Willamette ESUs were classified as not presently likely to become extinct or endangered. The BRT concluded that the remaining ESU (Middle Columbia River) was not presently in danger of extinction, but BRT members failed to agree on a conclusion regarding its likelihood of becoming endangered. A 15th ESU (Klamath Mountains Province) was reviewed previously (Busby et al. 1994) and is discussed here only for comparison.

Because of the requirements of the ESA, we have focused on factors contributing to risk of extinction or endangerment, rather than on more positive indicators of population "health." We identified some risk factors that are of concern for natural populations in all ESUs considered. Primary concerns for ESUs identified as either in danger of extinction or likely to become so are outlined for each ESU.

The other ESUs (those not judged to be in danger nor likely to become so) are generally distinguished by three characteristics. First, although population abundance in these ESUs may be below historical levels, naturally reproducing steelhead still occupy most of the historical range of the ESU in numbers that are sufficient to avoid most small-population risk problems. Second, while trends in the past few years may be downward, we did not find evidence that natural populations have failed to maintain themselves over longer time spans. Third, hatchery production does not appear to pose a major genetic risk to the natural populations in these ESUs, either because the level of hatchery production is relatively low or because there is evidence of substantial reproductive isolation between hatchery and natural populations.

Several factors relating to the status of steelhead populations were of substantial concern in all ESUs. Population trends since the mid-1980s have been downward in almost all ESUs. While this may reflect recent changes in regional climate patterns, it is unclear whether climate change is the sole cause of declines. It is also unclear if or when climate conditions may improve. Widespread degradation of both freshwater and estuarine habitats within the region is a concern, as are the potential results of continuing habitat destruction. The widespread production of hatchery fish raises concern for genetic integrity in most ESUs and is also of concern in determining the sustainability of natural production. Although in most cases available data are not sufficient to tell whether hatchery fish are having a strong negative impact on naturally produced steelhead, competition with introduced stocks for limited habitat could mask problems with the sustainability of natural stocks. Finally, many of the conclusions for specific ESUs involve a substantial degree of uncertainty resulting from lack of information on population abundance, trends, resident fish, and interactions between hatchery and natural fish.

Coastal Steelhead ESU Conclusions

1) Puget Sound--The BRT concluded that the Puget Sound steelhead ESU is neither presently in danger of extinction nor likely to become endangered in the foreseeable future. Despite this conclusion, the BRT has several concerns about the overall health of this ESU and about the status of certain stocks within the ESU. Recent trends in stock abundance are predominantly downward, although this may be largely due to recent climate conditions. Yet trends in the two largest stocks (Skagit and Snohomish Rivers) have been upward.

The majority of steelhead produced within the Puget Sound region appear to be of hatchery origin, but most hatchery fish are harvested, and estimates of hatchery fish escaping to spawn naturally are all less than 15% of total natural escapement, except for the Tahuya and Morse Creek/Independents stocks where the hatchery proportion is approximately 50%. We are particularly concerned that the majority of hatchery production originates from a single stock (Chambers Creek), which could increase genetic homogenization of the resource despite management efforts to minimize introgression of the hatchery gene pool into natural populations via separation of hatchery and natural run timing and high harvest rates focused on hatchery runs.

The status of certain stocks within the ESU is also of concern, especially the depressed status of most stocks in the Hood Canal area and the steep declines of Lake Washington winter steelhead and Deer Creek summer steelhead.

These conclusions are tempered by two substantial uncertainties. First, there is very little information regarding the abundance and status of summer steelhead in the Puget Sound region. Although the numbers of summer steelhead have historically been small relative to winter steelhead, they represent a substantially different life history strategy and loss of these fish would diminish the ecological and genetic diversity of the entire ESU. Second, there is uncertainty regarding the degree of interaction between hatchery and natural stocks. Although WDFW's conclusion that there is little overlap in spawning between natural and hatchery stocks of winter steelhead throughout the ESU is generally supported by available evidence, for many basins it is based largely on models and assumptions regarding run timing rather than empirical data.

2) Olympic Peninsula--The BRT concluded that the Olympic Peninsula steelhead ESU is neither presently in danger of extinction nor likely to become endangered in the foreseeable future. Despite this conclusion, the BRT has several concerns about the overall health of this ESU and about the status of certain stocks within it. The majority of recent abundance trends are upward (including three of the four largest stocks), although trends in several stocks are downward. These downward trends may be largely due to recent climate conditions. There is widespread production of hatchery steelhead within this ESU, largely derived from a few parent stocks, and this could increase genetic homogenization of the resource despite management efforts to minimize introgression of the hatchery gene pool into natural populations. Estimates of the proportion of hatchery fish on natural spawning grounds range from 16% to 44%, with the two stocks with the largest abundance of natural spawners (Queets and Quillayute) having the lowest hatchery proportions.

These conclusions are tempered by substantial uncertainties. As for the Puget Sound ESU, there is very little information regarding the abundance and status of summer steelhead in this region and the degree of interaction between hatchery and natural stocks.

3) Southwest Washington--The BRT concluded that the Southwest Washington steelhead ESU is neither presently in danger of extinction nor likely to become endangered in the foreseeable future. The latter conclusion was not unanimous, and a minority concluded that downward trends, coupled with introductions of hatchery fish from outside the ESU, indicated likelihood of becoming endangered. Almost all stocks for which we have data within this ESU have been declining in the recent past, although this may be largely due to recent climate conditions. The BRT members had a strong concern about the pervasive opportunity for genetic introgression from hatchery stocks within the ESU, and a great concern for the status of summer steelhead in this ESU. There is widespread production of hatchery steelhead within this ESU, largely from parent stocks outside the ESU. This production could substantially change the genetic composition of the resource, despite management efforts to minimize introgression of the hatchery gene pool into natural populations. Estimates of the proportion of hatchery fish on natural spawning grounds range from 9% in the Chehalis River, the largest producer of steelhead in the ESU, to 82% in the Clatskanie River.

As for the Puget Sound and Olympic Peninsula ESUs, these conclusions are tempered by substantial uncertainties regarding the abundance and status of summer steelhead in this region, and the degree of interaction between hatchery and natural stocks.

4) Lower Columbia River--The BRT concluded that the Lower Columbia River steelhead ESU is not presently in danger of extinction, but it is likely to become endangered in the foreseeable future. The latter conclusion was not unanimous, and there were two distinct minority opinions: one minority of the BRT concluded that there was little likelihood that this ESU will become endangered, while another minority was uncertain whether native steelhead still exist in this region. 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 those of 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 are quite short, so the preponderance of downward trends may reflect the general coastwide decline in steelhead in recent years. The BRT members had strong concern about the pervasive opportunity for genetic introgression from hatchery stocks within the ESU, and strong concern for the status of summer steelhead in this ESU. There is widespread production of hatchery steelhead within this ESU, and several stocks for which we have estimates of hatchery composition average more than 50% hatchery fish in natural escapement. Concerns about hatchery influence are especially strong for summer steelhead and Oregon winter steelhead stocks, where there appears to be substantial overlap in spawning between hatchery and natural fish.

The major area of uncertainty in this evaluation is the degree of interaction between hatchery and natural stocks within the ESU. WDFW's conclusion that there is little overlap in spawning between natural and hatchery stocks of winter steelhead throughout the ESU is generally supported by available evidence; however, with the exception of detailed studies of the Kalama River winter stock, it is based largely on models and assumptions regarding run timing rather than empirical data. There is apparently strong overlap in spawning between hatchery and natural summer steelhead in Washington tributaries. We have no information regarding potential spawning separation between hatchery and natural fish in Oregon tributaries to the Lower Columbia River.

5) Upper Willamette--The BRT concluded that the Upper Willamette steelhead ESU is neither presently in danger of extinction, nor likely to become endangered in the foreseeable future. The latter conclusion was not unanimous, and a minority of the BRT concluded that the small numbers and declining trend in the native stock, coupled with other risk factors, indicate a likelihood of becoming endangered. While historical information regarding this ESU is lacking, geographic range and historical abundance are believed to have been relatively small compared to other ESUs, and current production probably represents a larger proportion of historical production than is the case in other Columbia River Basin ESUs.

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%. The BRT members had strong concern about the pervasive opportunity for genetic introgression from hatchery stocks within the ESU, and strong concern for potential ecological interactions between introduced stocks and native stocks. There is widespread production of hatchery steelhead within the range of this ESU, predominantly of non-native summer and early-run winter steelhead.

There are two major areas of uncertainty in this evaluation. First, the degree of interaction between hatchery and natural stocks within the ESU is unknown. We have no information regarding potential spawning separation between hatchery and natural fish. Second, some of the trends for these populations are based on angler catch data, which may not be a good indicator of actual trends in population (see discussion in the Background section above).

6) Oregon Coast--The BRT concluded that the Oregon Coast steelhead ESU is not presently in danger of extinction, but that it is likely to become endangered in the foreseeable future. The latter conclusion was not unanimous, with a minority of the BRT concluding that there is little likelihood that this ESU will become endangered. Most steelhead populations within this ESU have been declining in the recent past (although this may be largely due to recent climate conditions), with increasing trends restricted to the southernmost portion of the ESU, south of Siuslaw Bay. The BRT members had strong concern about the pervasive opportunity for genetic introgression from hatchery stocks within this ESU and strong concern for potential ecological interactions between introduced stocks and native stocks. 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 in abundance, it is likely that natural stocks are not replacing themselves throughout the ESU.

There are two major areas of uncertainty in this evaluation. First, the degree of interaction between hatchery and natural stocks within the ESU is unknown. We have no information regarding potential spawning separation between hatchery and natural fish, nor about the spawning success of hatchery produced fish. Second, the majority of trends for these populations are based on angler catch data, which may not be a good indicator of actual trends in population abundance.

7) Klamath Mountains Province--The BRT has previously concluded that this ESU is not presently in danger of extinction, but that it is likely to become endangered in the foreseeable future (Busby et al. 1994). Although historical trends in overall abundance within the ESU are not clearly known, there has been substantial replacement of natural fish with hatchery produced fish. While absolute abundance remains fairly high, since about 1970 trends in abundance have been downward in most steelhead populations for which we have data within the ESU, 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. Most natural populations of steelhead within the area experience a substantial infusion of naturally spawning hatchery fish each year. After accounting for the contribution of these hatchery fish, we were unable to identify any steelhead populations that are naturally self-sustaining.

8) Northern California--The BRT concluded that the Northern California steelhead ESU is not presently in danger of extinction, but that it is likely to become endangered in the foreseeable future. Population abundances are very low relative to historical estimates (1930s dam counts), 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. There is particular concern regarding sedimentation and channel restructuring due to floods, apparently resulting in part from poor land management practices. The abundance of introduced Sacramento squawfish as a predator in the Eel River is also of concern. For certain rivers (particularly the Mad River), the BRT is concerned about the influence of hatchery stocks, both in terms of genetic introgression and of potential ecological interactions between introduced stocks and native stocks.

There are two major areas of uncertainty in this evaluation. First, we lack information on steelhead run sizes throughout the ESU. Our conclusions were based largely on evidence of habitat degradation and the few dam counts and survey index estimates of stock trends in the region. Second, the genetic heritage of the natural winter steelhead population in the Mad River is uncertain.

9) Central California Coast--The BRT concluded that the Central California Coast steelhead ESU is presently in danger of extinction. The southernmost portion of the ESU (south of Scott and Waddell Creeks, including one of two major rivers within the ESU) and the portion within San Francisco and San Pablo Bays, appears to be at extreme risk. In the northern coastal portion of the ESU, 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. There is particular concern about sedimentation and channel restructuring due to floods, apparently resulting in part from poor land management practices.

There are two major areas of uncertainty in this evaluation. First, due to the lack of information on steelhead run sizes throughout the ESU, our conclusions were based largely on evidence of habitat degradation and the few estimates of abundance and stock trends in the region. Second, the genetic heritage of the natural populations in tributaries to San Francisco and San Pablo Bays is uncertain, making it difficult to determine which of these populations should be considered part of the ESU.

10) South-Central California Coast--The BRT concluded that the South-Central California Coast steelhead ESU is presently in danger of extinction. Total abundance is extremely low, and most stocks for which we have data in the ESU show recent downward trends. There is particular concern about sedimentation and channel restructuring due to floods, which apparently result in part from poor land management practices. There is also concern about the genetic effects of widespread stocking of rainbow trout.

The major area of uncertainty in this evaluation is the lack of information on steelhead run sizes throughout the ESU. Our conclusions were based largely on evidence of habitat degradation and the few estimates of abundance and stock trends in the region.

11) Southern California--The BRT concluded that the Southern California steelhead ESU is presently in danger of extinction. Steelhead have already been extirpated from much of their historical range in this region. The BRT members had 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 is also concern about the genetic effects of widespread stocking of rainbow trout.

There are two major areas of uncertainty in this evaluation. First, accurate run size and trend estimates are lacking for natural steelhead stocks in this ESU. Second, the relationship between resident and anadromous forms of the biological species is unclear.

12) Central Valley--The BRT concluded that the Central Valley steelhead ESU is presently in danger of extinction. 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 members also had strong concerns about the pervasive opportunity for genetic introgression from hatchery stocks within the ESU and about potential ecological interactions between introduced stocks and native stocks. There is widespread production of hatchery steelhead within this ESU.

There are two major areas of uncertainty in this evaluation. First, there is a total lack of recent run-size estimates for natural steelhead stocks in this ESU. Second, there is a substantial question regarding the genetic heritage of remaining natural populations, making it difficult to determine which populations should be considered part of the ESU.

Inland Steelhead ESU Conclusions

13) Middle Columbia--The BRT concluded that the Middle Columbia steelhead ESU is not presently in danger of extinction, but reached no conclusion regarding its likelihood of becoming endangered in the foreseeable future. All BRT members felt special concern for the status of this ESU and concluded that NMFS should carefully evaluate conservation measures affecting this ESU and continue monitoring its status. There is particular concern about Yakima River stocks and winter steelhead stocks. Winter steelhead are reported within this ESU only in the Klickitat River and Fifteenmile Creek; we have no abundance information for winter steelhead in the Klickitat River, but they have been declining in abundance in Fifteenmile Creek.

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. The BRT members expressed strong concern about the pervasive opportunity for genetic introgression from hatchery stocks within the ESU. There is widespread production of hatchery steelhead within this ESU, but it is largely based on within-basin stocks. Estimated proportion of hatchery fish on spawning grounds ranges from low, in the Yakima, Walla Walla, and John Day Rivers to moderate in the Umatilla and Deschutes Rivers. Habitat degradation due to grazing and water diversions has been documented throughout the ESU.

There are three major areas of uncertainty in this evaluation. First, run-size estimates are lacking for most populations. Second, the degree of interaction between hatchery and natural stocks within the ESU is uncertain; we have little information regarding potential spawning separation between hatchery and natural fish. Third, the relationship between anadromous and resident forms of O. mykiss is unclear; we have little information regarding abundance of resident fish or their interactions with anadromous fish, but resident forms may play an important role in some areas of this ESU.

14) Upper Columbia--The BRT concluded that the Upper Columbia steelhead ESU is presently in danger of extinction. While total abundance of populations within this ESU has been relatively stable or increasing, this appears to be occurring 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 members are also strongly concerned about problems of genetic homogenization due to hatchery supplementation within the ESU and 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.

There are two major areas of uncertainty in this evaluation. First, the relationship between resident and anadromous forms of the biological species is unclear, both in terms of native rainbow trout in the streams presently supporting steelhead and in terms of potential residualized (footnote 5) steelhead above Grand Coulee Dam. Second, there is uncertainty regarding the genetic heritage of naturally spawning fish within the ESU.

15) Snake River Basin--The BRT concluded that the Snake River Basin steelhead ESU is not presently in danger of extinction, but it is likely to become endangered in the foreseeable future. The latter conclusion was not unanimous, and a minority of the BRT concluded that there was little likelihood that this ESU will become endangered. While total (hatchery + natural) run size has increased since the mid-1970s, 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 has a strong concern about the pervasive opportunity for genetic introgression from hatchery stocks within the ESU. There is widespread production of hatchery steelhead within this ESU. The total Snake River steelhead run at Lower Granite Dam is estimated to average 86% hatchery fish in recent years. Estimates of proportion of hatchery fish in spawning escapement for Snake River tributaries range from 0% in Joseph Creek to above 80% in the upper Salmon River (IDFG 1995). The BRT members also were concerned about the degradation of freshwater habitats within the region, especially the effects of grazing, irrigation diversions, and hydroelectric dams.

There are three major areas of uncertainty in this evaluation. First, there is a lack of run-size estimates for most populations. Second, the degree of interaction between hatchery and natural stocks within the ESU is unknown. We have little information regarding interactions between hatchery and natural fish. Third, the relationship between anadromous and resident forms of O. mykiss is unclear; we have little information regarding abundance of resident fish or their interactions with anadromous fish.


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