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

NOAA-NWFSC Tech Memo-27: Status Review of West Coast Steelhead
9) Central California Coast--Previous assessments within this ESU have identified several stocks as being at risk or of special concern. Nehlsen et al. (1991) identified two stock groups as at high risk of extinction: Napa River and San Francisco Bay Tributaries (Table 9). Titus et al. (in press) provided a more detailed analysis of stocks south of San Francisco Bay and identified numerous stocks that were declining.

Only two estimates of historical (pre-1960s) abundance specific to this ESU are available: the first reported an average of about 500 adults in Waddell Creek in the 1930s and early 1940s (Shapovalov and Taft 1954), and the second estimated 20,000 steelhead in the San Lorenzo River before 1965 (Johnson 1964) (Table 19). In the mid-1960s, CDFG (1965, table S-3) estimated 94,000 steelhead spawning in many rivers of this ESU (Table 17). We have comparable recent estimates for only the Russian and San Lorenzo Rivers, which contain the two largest stocks in the ESU. Recent total abundance in these two rivers is estimated to be less than 15% of their abundance 30 years ago (Table 17). Additional recent estimates are available for several other streams (Table 20, Fig. 26), but we have no recent estimates for total run size for this ESU.

McEwan and Jackson (1996) noted that steelhead in most streams tributary to San Francisco and San Pablo Bays have been extirpated, although small "fair to good" runs of steelhead reportedly occur in coastal Marin County tributaries (Cox, Smith).

Two substantial habitat blockages are documented: Coyote and Warm Springs Dams in the Russian River Basin (McEwan and Jackson 1996), and other minor blockages (smaller dams, impassable culverts, etc.) are likely throughout the region Titus et al. (in press) reported blockages on 12 of 46 tributaries in the southern portion of this ESU, and he noted fish passage problems in most other tributaries. Streams in this region probably suffer from a variety of habitat factors, including urbanization and poor land management practices in both forestry and agriculture.

Habitat throughout the north coast of California, including portions occupied by this ESU, was severely impacted by catastrophic flooding in 1964. Damage from this flood was probably exacerbated by poor land use practices prior to the event (McEwan and Jackson 1996). Forest practices have also contributed to incremental degradation of stream habitats (McEwan and Jackson 1996). Dewatering due to irrigation and urban water diversions is also a problem. Titus et al. (in press) documented some of these problems for specific tributaries in the southern portion of this ESU. Other habitat problems similar to those cited for the Oregon Coast ESU probably also occur in this region.

Adequate adult escapement information was not available to compute trends for any stocks within this ESU (Table 20, Fig. 27). However, general trends can be inferred from the comparison of 1960s and 1990s abundance estimates provided above, and these indicate substantial rates of decline in the two largest steelhead stocks (Russian and San Lorenzo Rivers).

Presently, the principal hatchery production in this ESU is from Warm Springs Hatchery on the Russian River and the Monterey Bay Salmon and Trout Project located at Big Creek Hatchery off Scott Creek and at other facilities. There are other small private and cooperative programs producing steelhead within the range of this ESU. Most of the hatchery stocks used in this region originated from stocks indigenous to the ESU, but many are not native to their local river basins (Bryant 1994).

We have little information on the actual contribution of hatchery fish to natural spawning, and little information on present total run sizes or trends for this ESU. However, given the substantial negative trends in the stocks for which we do have data, it is likely that the majority of natural production in this ESU is not self-sustaining. It appears that most of the recent declines in steelhead abundance within this ESU have occurred in the larger river systems, while populations in many smaller streams are relatively healthy and probably have not experienced significant recent changes in abundance (Cox footnote 18, Smith footnote 19).

The major present threat to genetic integrity for steelhead in this ESU comes from past and present hatchery practices. General risk factors relating to hatchery practices were discussed previously in the Background section. Within this ESU, we have little information regarding present hatchery production and no information regarding spatial or temporal separation of spawning hatchery and natural fish. However, there is probably sufficient overlap in spawning for some genetic introgression to occur. Habitat fragmentation and population declines resulting in small, isolated populations also pose genetic risk from inbreeding, loss of rare alleles, and genetic drift.

In evaluating the status of this ESU, we have not accounted for abundance or trends in populations of resident O. mykiss (rainbow trout), which may be a significant part of the ESU. We have received insufficient information regarding resident trout in this region to reasonably evaluate their status or their interactions with anadromous steelhead.

10) South-Central California Coast--Previous assessments within this ESU have identified several stocks as being at risk or of special concern. Nehlsen et al. (1991) identified five stocks as at risk (Table 9). Titus et al. (in press) provided a more detailed analysis of stocks south of San Francisco Bay and identified numerous stocks that were declining (Appendix E).

Historical estimates of steelhead abundance are available for a few streams in this region (Table 21). The California Advisory Committee on Salmon and Steelhead (CACSS 1988) cited an estimate of 20,000 steelhead in the Carmel River in 1928. In the mid-1960s, CDFG (1965, table S-3) estimated 27,750 steelhead spawning in many rivers of this ESU (Table 17). However, comparisons with recent estimates for these rivers show a substantial decline during the past 30 years. In contrast to the CDFG (1965) estimates, McEwan and Jackson (1996) reported runs ranging from 1,000 to 2,000 in the Pajaro River in the early 1960s, and Snider (1983) estimated escapement of about 3,200 steelhead for the Carmel River for the 1964-75 period.

While we have no recent estimates of total run size for this ESU, recent run-size estimates are available for five streams (Table 22, Fig. 26). The total of these estimates is less than 500, compared with a total of 4,750 for the same streams in 1965, which indicates a substantial decline for the entire ESU from 1965 levels.

Minor habitat blockages (smaller dams, impassable culverts, etc.) are likely throughout the region. Titus et al (in press) reported blockages on 28 of 66 tributaries in this ESU, and some passage impairments on most other tributaries. Streams in this region probably suffer from a variety of habitat factors similar to those affecting neighboring ESUs. Forest practices have contributed to incremental degradation of stream habitats (McEwan and Jackson 1996), and dewatering due to irrigation and urban water diversions is also a problem. Titus et al. (in press) have documented some of these problems for specific tributaries in the southern portion of this ESU.

Adequate adult escapement information was available to compute a trend for only one stock within this ESU: Carmel River above San Clemente Dam (Table 22, Fig. 27). These data show a significant decline of 22% per year from 1963 to 1993, with a recent 5-year average count of only 16 adult steelhead at the dam. However, general trends for the region can be inferred by comparing the 1960s and 1990s abundance estimates provided above.

Presently, there is little hatchery production within this ESU. There are small private and cooperative programs producing steelhead within this ESU, as well as one captive broodstock program intended to conserve the Carmel River steelhead strain (McEwan and Jackson 1996). Most hatchery stocks used in this region originated from stocks indigenous to the ESU, but many are not native to their local river basins (Bryant 1994). We have little information on the actual contribution of hatchery fish to natural spawning, and little information on present total run sizes or trends for this ESU. However, given the substantial reductions from historical abundance and the recent negative trends in the stocks for which we do have data, it is likely that the majority of natural production in this ESU is not self-sustaining.

Past and present hatchery practices probably pose some risk to steelhead in this ESU as discussed previously in the Background section. Habitat fragmentation and population declines resulting in small, isolated populations also pose genetic risk from inbreeding, loss of rare alleles, and genetic drift.

In evaluating the status of this ESU, we have not accounted for abundance or trends in populations of resident O. mykiss (rainbow trout), which may be a significant part of the ESU. We have received insufficient information regarding resident trout in this region to reasonably evaluate their status or their interactions with anadromous steelhead.

11) Southern California--Previous assessments within this ESU have identified several stocks as being at risk or of special concern. Nehlsen et al. (1991) identified 11 stocks as extinct and 4 as at high risk (Table 9). Titus et al. (in press) provided a more detailed analysis of these stocks and identified stocks within 14 drainages in this ESU as extinct, at risk, or of concern. They identified only two stocks, those in Arroyo Sequit and Topanga Creek, as showing no significant change in production from historical levels.

Historically, steelhead may have occurred naturally as far south as Baja California. Estimates of historical (pre-1960s) abundance are available for several rivers in this ESU (Table 23): Santa Ynez River, before 1950, 20,000-30,000; Ventura River, pre-1960, 4,000-6,000; Santa Clara River, pre-1960, 7,000-9,000; Malibu Creek, pre-1960, 1,000. In the mid-1960s, CDFG (1965, table S-3) estimated steelhead spawning populations for smaller tributaries in San Luis Obispo County as 20,000, but they provided no estimates for streams farther south.

The present total run sizes for 6 streams in this ESU were summarized by Titus et al. (in press); all were less than 200 adults (Table 24, Fig. 26). Titus et al. (in press) concluded that populations have been extirpated from all streams south of Ventura County, with the exception of Malibu Creek in Los Angeles County. However, steelhead are still occasionally reported in streams where stocks were identified by these authors as extirpated.

Titus et al. (in press) cited extensive loss of steelhead habitat due to water development, including impassable dams and dewatering of portions of rivers. They also reported that of 32 tributaries in this region, 21 have blockages due to dams, and 29 have impaired mainstem passage. Habitat problems in this ESU relate primarily to water development resulting in inadequate flows, flow fluctuations, blockages, and entrainment into diversions (McEwan and Jackson 1996, Titus et al. in press). Other problems related to land use practices and urbanization also certainly contribute to stock conditions.

No time series of data are available within this ESU from which to estimate population trends, but Titus et al. (in press) summarized information for steelhead populations based on historical and recent survey information. Of the populations south of San Francisco Bay (including part of the Central California Coast ESU) for which past and recent information was available, they concluded that 20% had no discernible change, 45% had declined, and 35% were extinct. Percentages for the counties comprising this ESU are given in Table 25 and show a very high percentage of declining and extinct populations.

There is no current hatchery production of steelhead within this ESU. The small run sizes and almost universal declines in these populations strongly suggest that natural production is not self-sustaining.

The influence of hatchery practices on this ESU is not well documented. Common risk factors relating to hatchery practices were discussed previously in the Background section. In some populations, there may be genetic introgression from past steelhead plants and from planting of rainbow trout (Nielsen footnote 9). Habitat fragmentation and population declines have also resulted in small, isolated populations that may face genetic risk from inbreeding, loss of rare alleles, and genetic drift.

In evaluating the status of this ESU, we have not accounted for abundance or trends in populations of resident O. mykiss (rainbow trout), which may be a significant part of the ESU. We do not have sufficient information regarding resident trout in this region to reasonably evaluate their status or their interactions with anadromous steelhead.

12) Central Valley--Only Nehlsen et al. (1991) have provided a status assessment for stocks within this ESU; they identified one stock (Sacramento River) as at high risk (Table 9). However, this stock represents all the known populations of steelhead within the ESU.

Historical abundance estimates are available for some stocks within this ESU (Table 26), but no overall estimates are available prior to 1961, when Hallock et al. (1961) estimated a total run size of 40,000 steelhead in the Sacramento River, including San Francisco Bay. In the mid-1960s, CDFG (1965, table S-3) estimated steelhead spawning populations for the rivers in this ESU, totaling almost 27,000 fish (Table 17).

We have limited data on recent abundance for this ESU (Table 27, Fig. 28), but its present total run size based on dam counts, hatchery returns, and past spawning surveys is probably less than 10,000 fish. Both natural and hatchery runs have declined since the 1960s. Counts at Red Bluff Diversion Dam averaged 1,400 fish over the last 5 years, compared with runs in excess of 10,000 fish in the late 1960s. Recent run-size estimates for the hatchery produced American River stock average less than 1,000 fish, compared to 12,000-19,000 in the early 1970s (McEwan and Jackson 1996).

Historically, steelhead occurred naturally throughout the Sacramento and San Joaquin River Basins; however, stocks have been extirpated from large areas of the Sacramento River Basin and possibly from the entire San Joaquin River Basin. The California Advisory Committee on Salmon and Steelhead (CACSS 1988) reported a reduction in Central Valley steelhead habitat from 6,000 miles historically to 300 miles at present. Reynolds et al. (1993, p. III-1) reported that 95% of salmonid habitat in California's Central Valley has been lost, largely due to mining and water development activities. They also noted (p. IV-8) that declines in Central Valley steelhead stocks are "due mostly to water development, inadequate instream flows, rapid flow fluctuations, high summer water temperatures in streams immediately below reservoirs, diversion dams which block access, and entrainment of juveniles into unscreened or poorly screened diversions." Thus, overall habitat problems in this ESU relate primarily to water development resulting in inadequate flows, flow fluctuations, blockages, and entrainment into diversions (McEwan and Jackson 1996). Other problems related to land use practices (agriculture and forestry) and urbanization have also certainly contributed to stock declines.

Adequate adult escapement information was available to compute a trend for only one stock within this ESU: the Sacramento River population above Red Bluff Diversion Dam (Table 27, Fig. 29). This data series showed a significant decline of 9% per year from 1966 to 1992 (Table 27, Appendix E). McEwan and Jackson (1996) cite substantial declines in hatchery returns within the basin as well. Most indigenous natural production of steelhead in this ESU occurs in upper Sacramento River tributaries (Antelope, Deer, and Mill Creeks) below Red Bluff Diversion Dam. Fish passing over that dam are primarily of hatchery origin (70-90%). The American, Feather, and Yuba Rivers, and possibly the upper Sacramento and Mokelumne Rivers, also have naturally spawning populations (CDFG 1995), but these populations have had substantial hatchery influence and their ancestry is not clearly known. The Yuba River had an estimated run size of 2,000 in 1984, and though recent run sizes are unknown the population appears to be stable and supports a fishery (McEwan and Jackson 1996). However, the status of native, natural fish in this stock is unknown: the stock has been influenced by Feather River Hatchery fish, and biologists familiar with the stock report that the Yuba River supports almost no natural production of steelhead (Hallock 1989). Nevertheless, CDFG (1995) asserted that "a substantial portion of the returning adults are progeny of naturally spawning adults from the Yuba River." This stock currently receives no hatchery steelhead plants and is managed as a naturally sustained population (CDFG 1995, McEwan and Jackson 1996).

There are reports of a small remnant steelhead run in the Stanislaus River, steelhead were observed in the Tuolumne River in 1983, and large rainbow trout (possibly steelhead) have been observed at Merced River Hatchery recently (McEwan and Jackson 1996). Wild stocks in Mill, Deer, and Antelope Creeks and other upper Sacramento tributaries may be native or mostly native, but these populations are nearly extirpated. Given the widespread recent declines in abundance and the large proportion of hatchery production in the basin as a whole, natural production in this ESU is unlikely to be self-sustaining.

The major present threat to genetic integrity for steelhead in this ESU comes from past and present hatchery practices. Common risk factors relating to hatchery practices were discussed previously in the Background section. We have little information regarding spatial or temporal separation of spawning hatchery and natural fish within this ESU, but there is probably sufficient overlap for some genetic introgression to occur. There is also a substantial problem with straying of hatchery fish within this ESU (Hallock 1989). Habitat fragmentation and population declines resulting in small, isolated populations also pose genetic risk from inbreeding, loss of rare alleles, and genetic drift.

In evaluating the status of this ESU, we have not accounted for abundance or trends in populations of resident O. mykiss (rainbow trout), which may be a significant part of the ESU. We do not have sufficient information regarding resident trout in this region to reasonably evaluate their status or their interactions with anadromous steelhead.

Inland Steelhead ESUs

13) Middle Columbia River--Previous assessments within this ESU have identified several stocks as being at risk or of special concern. Nehlsen et al. (1991) identified six stocks as at risk or of concern (Table 9). WDF et al. (1993) considered six stocks within the ESU, four of which were considered to be of native origin and predominantly natural production. They considered the status of these four stocks as one depressed and three unknown. The remaining two stocks were considered depressed.

Estimates of historical (pre-1960s) abundance specific to this ESU are available for the Yakima River, with an estimated run size of 100,000 (WDF et al. 1993, Appendix 3). If we assume that other basins had comparable run sizes for their drainage areas, the total historical run size for this ESU might have been in excess of 300,000. Total run sizes for the major stocks in the Columbia River above Bonneville Dam, including stocks in the Upper Columbia River and Snake River Basin ESUs and parts of the Southwest Washington and Lower Columbia River ESUs, were estimated by Light (1987) as approximately 4,000 winter steelhead and 210,000 summer steelhead in the early 1980s. Based on dam counts for this period, the Middle Columbia River ESU represented the majority of this total run estimate, so the run returning to this ESU was probably somewhat below 200,000 at that time. Light estimated that the total run (summer and winter steelhead combined) was of 80% hatchery origin. We have estimated run sizes for this ESU by subtracting adult steelhead counts at Lower Granite and Priest Rapids Dams from those at Bonneville Dam for the period 1975-93 (Fig. 30). The most recent 5-year average run size was 142,000, with a naturally produced component of 39,000. These data indicate approximately 74% hatchery fish in the total run to this ESU.

We have recent escapement or run size estimates for only the following five basins in this ESU (Table 28, Fig. 31). 1) For the main Deschutes River (counted at Sherars Falls), total recent 5-year average run size was approximately 11,000, with a natural escapement of 3,000. Hatchery escapement to spawning grounds, calculated by subtracting Pelton Ladder and other hatchery returns from the counts at Sherars Falls has averaged about 4,000 adults over the last five brood years (BPA 1992). 2) For Warm Springs River steelhead passing above Warm Springs NFH, escapement has averaged 150 adults over the last 5 years. 3) In the Umatilla River, escapement counted at Three Mile Dam has averaged 1,700 adults over the last 5 years. 4) In the Yakima River, total escapement has averaged 1,300 adults, with a natural escapement of 1,200 adults over the last 5 years. 5) ODFW (1995a) suggested that five subbasins of the John Day River each have runs in excess of 1,000, so the total run size for the John Day River is probably in excess of 5,000 fish.

The only substantial habitat blockage at present in this ESU is at Pelton Dam on the Deschutes River, but minor blockages from smaller dams, impassable culverts, etc., are likely throughout the region. Several dams in the John Day River Basin previously blocked habitat, but they have since been modified with ladders (CBFWA 1990); however, there is a possibility that local native stocks were extirpated before these ladders were built.

Bottom et al. (1985) noted that high summer and low winter temperatures are limiting factors for salmonids in many streams in this region. They noted that flows below recommended levels occur in the Umatilla and John Day Rivers, that extreme temperature conditions exist in the lower John Day River, and that water withdrawals and overgrazing have seriously reduced summer flows in the principal summer steelhead spawning and rearing tributaries of the Deschutes River. There is little or no late summer flow in sections of the lower Umatilla and Walla Walla Rivers. Riparian vegetation is heavily impacted by overgrazing and other agricultural practices, timber harvest, road building, and channelization. Of stream segments inventoried within this ESU, riparian restoration is needed for between 37% and 84% of the river bank in various basins. Instream habitat is also affected by these same factors, as well as by past gold dredging and severe sedimentation due to poor land management practices.

Stock trend data are available for various basins from dam counts, spawner surveys, and angler catch. Because the relationship of angler catch to natural stock abundance is unclear in this region and alternate data were available for most basins, we have not relied on angler catch data in our evaluations of this ESU; trends in angler catch are included in Appendix E for comparison. For these evaluations, spawner survey data for individual tributaries have been aggregated by subbasin to avoid frequent zero counts and to provide more representative regional trends.

Of the 14 independent stock indices for which we could compute trends (Appendix E), 10 have been declining and 4 increasing during the available data series, with a range from 20% annual decline to 14% annual increase (Table 28, Fig. 32). Eight of these trends were significantly different from zero, with seven negative and one positive (Appendix E). Of the major basins, the Yakima, Umatilla, and Deschutes Rivers show upward trends overall, although all trends in the Deschutes River tributaries are downward and the Yakima River is recovering from a period of extremely low abundance in the early 1980s. The John Day River probably represents the largest native, natural spawning stock in the region, and combined spawner surveys for this basin have been declining at a rate of about 15% per year since 1985. However, estimates of total run size for the ESU based on differences in counts at dams (Fig. 30) show an overall increase in steelhead abundance, with a relatively stable naturally produced component. It is likely that recent trends in most basins have been negatively affected by recent drought in the region.

Hatchery fish are widespread and escaping to spawn naturally throughout the region. Hatchery production in this region is derived primarily from within-basin stocks. Recent estimates of the proportion of natural spawners that are of hatchery origin (Table 28, Appendix E) range from low in the Yakima, Walla Walla, and John Day Rivers, to moderate in the Umatilla and Deschutes Rivers. However, we have little information on the actual contribution of hatchery production to natural spawning. The relatively low natural run sizes in individual streams for which we have estimates, the preponderance of negative trends in abundance, and the widespread presence of hatchery fish lead to concern that some natural steelhead populations in this ESU may not be self-sustaining. There is particular concern that Yakima River steelhead and winter steelhead stocks in the Klickitat River and Fifteenmile Creek may be at risk.

The major present threat to genetic integrity for steelhead in this ESU comes from past and present hatchery practices. Risk factors relating to hatchery practices were discussed previously in the Background section.

In evaluating the status of this ESU, we have not accounted for abundance or trends in populations of resident O. mykiss (rainbow trout), which may be a significant part of the ESU. We have insufficient information regarding resident trout in this region to reasonably evaluate their status or their interactions with anadromous steelhead.

14) Upper Columbia River--Previous assessments within this ESU have identified several stocks as being at risk or of special concern. Nehlsen et al. (1991) identified six stocks as at risk or of concern (Table 9). WDF et al. (1993) assessed three stocks within the ESU, of which all were considered to be of mixed origin, wild production, and depressed. WDF et al. considered only the wild component of mixed stocks in reaching their conclusions.

Estimates of historical (pre-1960s) abundance specific to this ESU are available from fish counts at dams. Counts at Rock Island Dam from 1933 to 1959 averaged 2,600-3,700, suggesting a pre-fishery run size in excess of 5,000 adults for tributaries above Rock Island Dam (Chapman et al. 1994). However, runs may already have been depressed by lower Columbia River fisheries at this time. The following recent 5-year (1989-93) average natural escapement estimates are available: 800 steelhead in the Wenatchee River and 450 steelhead in the Methow and Okanogan Rivers (Table 29, Fig. 31). Recent average total escapement estimates 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 steelhead.

Substantial habitat blockages occurred with the construction of Chief Joseph and Grand Coulee Dams, as well as smaller dams on tributary rivers. Habitat problems for this ESU are largely related to irrigation diversions and hydroelectric dams, as well as degraded riparian and instream habitat from urbanization and livestock grazing.

Trends in total (natural and hatchery) adult escapement are available for the Wenatchee River (2.6% annual increase, 1962-93) and the Methow and Okanogan Rivers combined (12% annual decline, 1982-93) (Table 29, Figs. 32 & 33). These two stocks represent most of the escapement to natural spawning habitat within the range of the ESU, although the Entiat River also has a small spawning run (WDF et al. 1993).

Hatchery fish are widespread and escaping to spawn naturally throughout the region. The hatchery stock used in this region originated from stocks indigenous to the ESU during the Grand Coulee Fish Maintenance Project, but represents a blend of fish from all basins within the ESU and from areas above Grand Coulee Dam. Spawning escapement is strongly dominated by hatchery production, with estimates of recent contributions averaging 65% in the Wenatchee River and 81% in the Methow and Okanogan Rivers. WDFW estimated adult replacement ratios of only 0.3:1.0 in the Wenatchee River and 0.25:1.0 in the Entiat River and concluded that both these stocks and the Methow/Okanogan stock are not self-sustaining without substantial hatchery supplementation. WDF et al. (1993) suggested that the original Okanogan stock may be extinct, "except perhaps for resident morphs (rainbow trout) in Salmon and Omak creeks." This ESU might not exist today if there were not hatchery production based on indigenous stocks.

The major present threat to genetic integrity for steelhead in this ESU comes from past and present hatchery practices. Risk factors relating to hatchery practices were discussed previously in the Background section. The stocks above Rock Island Dam are largely driven by hatchery production. Although the major hatchery production in these rivers has been derived from stocks indigenous to the ESU, there are distinct genetic risks associated with hatchery supplementation.

In evaluating the status of this ESU, we have not accounted for abundance or trends in populations of resident O. mykiss (rainbow trout), which may be a significant part of the ESU. We have received insufficient information regarding resident trout in this region to reasonably evaluate their status or their interactions with anadromous steelhead.

15) Snake River Basin--Previous assessments within this ESU have identified several stocks as being at risk or of special concern. Nehlsen et al. (1991) identified 13 stocks as at risk or of concern (Table 9). WDF et al. (1993) assessed three stocks within the ESU, of which all were considered to be of mixed origin and composite production; all three stocks were identified as depressed.

No estimates of historical (pre-1960s) abundance specific to this ESU are available. Light (1987) estimated that 80% of the total Columbia River Basin run above Bonneville Dam (summer and winter steelhead combined) was of hatchery origin. All steelhead in the Snake River Basin are summer steelhead and for management purposes are divided into "A-run" and "B-run" fish. This division is based on several life history differences including spawner size and run timing. Although there is little information for most stocks within this ESU, there are recent run size or escapement estimates for several stocks (Table 30, Fig. 31). Total recent 5-year average escapement above Lower Granite Dam was approximately 71,000, with a natural component of 9,400 (7,000 A-run and 2,400 B-run). Run-size estimates are available for only a few tributaries within the ESU, all with small populations (Table 30, Appendix E).

There have been several substantial habitat blockages in this ESU, the major ones being the Hells Canyon Dam complex on the mainstem Snake River and Dworshak Dam on the North Fork Clearwater River. Minor blockages (from smaller dams, impassable culverts, etc.) are likely throughout the region. Bottom et al. (1985) noted that high summer and low winter temperatures are limiting for salmonids in many streams in eastern Oregon. They noted that flows below recommended levels occur in the Grande Ronde River, especially in late fall through early spring, and that water withdrawals and low flows are severe in several areas of that basin.

Riparian vegetation is heavily impacted by overgrazing and other agricultural practices, timber harvest, road building and channelization. Prime steelhead spawning areas have been degraded by overgrazing in several parts of the Grande Ronde Basin. Of inventoried segments of streams in the Grande Ronde River Basin, restoration is needed for between 38% (upper basin) and 59% (lower basin) of river bank. Instream habitat is also affected by these same factors, as well as past gold dredging and severe sedimentation due to poor land management practices. Although not as clearly documented, similar habitat problems can be expected in other basins within this ESU. One of the most significant habitat problems facing steelhead in this ESU is substantial modification of the migration corridor by hydroelectric power development in the mainstem Snake and Columbia Rivers.

The aggregate trend in abundance for this ESU (indexed at Lower Granite Dam) has been upward since 1975, although natural escapement has been declining during the same period (Fig. 34). However, the aggregate trend has been downward (with wide fluctuations) over the past 10 years, recently reaching levels below those observed at Ice Harbor Dam in the early 1960s. Naturally produced escapement has declined sharply in the last 10 years. Adult abundance trend information is available for several individual stocks from a variety of sources, including spawner surveys, dam counts, and angler catch (Table 30, Fig. 32). Because of the focus of angler catch on hatchery fish in this region and the availability of other estimates, we have not used angler catch trends in our evaluations, although they are included in Appendix E for comparison.

Of the 13 stock indices (excluding the Lower Granite Dam counts discussed above) for which we had adequate information to compute trends, 9 have been declining and 4 increasing during the available data series, with a range from 30% annual decline to 4% annual increase. Four of the negative trends were significantly different from zero (Appendix E). In addition to these adult abundance data, the focus of IDFG's steelhead monitoring program is juvenile (parr) surveys in wild or natural production areas. Most of the individual juvenile data series available to us were too short to compute reliable trends, but summaries presented by Leitzinger and Petrosky (in press) showed declines in average parr density over the past 7 or 8 years for both A- and B-run steelhead in both wild and natural production areas. From 1985 to 1993, estimates of mean percent of rated parr carrying capacity for these surveys ranged from as low as 11.2% (wild-production B-run) to 62.1% (wild-production A-run). The Columbia River Fisheries Management Plan Technical Advisory Committee found that A-run steelhead densities were closer to rated capacities than were B-run steelhead, but noted that "percent carrying capacity indicates that all surveyed areas are underseeded" (CRFMP TAC 1991, p. 6). It is likely that recent trends in most basins have been negatively affected by recent drought in the region.

Hatchery fish are widespread and escape to spawn naturally throughout the region. During the past 5 years, an average of 86% of adult steelhead passing Lower Granite Dam were of hatchery origin. Only two hatchery composition estimates are available for individual stocks: 0% for Joseph Creek (Grande Ronde River), and 57% for the Tucannon River. We have little information on the actual contribution of hatchery production to natural spawning, and on natural escapements for most stocks in this ESU. In general, there are wild production areas with limited hatchery influence remaining in the Selway River, lower Clearwater River, Middle and South Forks of the Salmon River, and the lower Salmon River (Leitzinger and Petrosky in press). In other areas, such as the upper Salmon River, there appears to be little or no natural production of locally native steelhead (IDFG 1995). Given the relatively low natural run sizes to individual streams for which we have estimates, the declines in natural returns at Lower Granite Dam, the declines in parr density estimates, and the widespread presence of hatchery fish, we conclude that the majority of natural steelhead populations in this ESU are probably not self-sustaining at this time.

The major present threat to genetic integrity for steelhead in this ESU comes from past and present hatchery practices, discussed previously. Common risk factors relating to hatchery practices were discussed previously in the Background section.

An additional concern in this ESU is the status of steelhead native to the North Fork of the Clearwater River, now maintained at Dworshak NFH. While this hatchery population is presently fairly large, it represents the only remaining gene pool for steelhead native to that tributary. This population has not had access to its native habitat for 25 years.

In evaluating the status of this ESU, we have not accounted for abundance or trends in populations of resident O. mykiss (rainbow trout), which may be a significant part of the ESU. We have insufficient information regarding resident trout in this region to reasonably evaluate their status or their interactions with anadromous steelhead.


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