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

NOAA-NWFSC Tech Memo-27: Status Review of West Coast Steelhead
Analysis of Biological Information

Coastal Steelhead ESUs

1) Puget Sound--Previous assessments of steelhead within the range of this ESU have identified several stocks as being at risk or of concern. Nehlsen et al. (1991) identified nine stocks as at some degree of risk or concern (Table 9). WDF et al. (1993) considered 53 stocks within the ESU, of which 31 were considered to be of native origin and predominantly natural production. Their assessment of these 31 stocks was 11 healthy, 3 depressed, 1 critical, and 16 unknown. Their assessment of the remaining (not native/natural) stocks was 3 healthy, 11 depressed, and 8 unknown (Appendix E).

No estimates of historical (pre-1960s) abundance specific to the Puget Sound ESU are available. Total run size for Puget Sound in the early 1980s can be calculated from estimates in Light (1987) as approximately 100,000 winter steelhead and 20,000 summer steelhead. Light provided no estimate of hatchery proportions specific to Puget Sound streams, but for Puget Sound and coastal Washington combined, he estimated that 70% of steelhead in ocean runs were of hatchery origin. The percentage in escapement to spawning grounds would be substantially lower due to differential harvest and hatchery rack returns.

Recent 5-year average natural escapements for streams with adequate data range from less than 100 to 7,200, with corresponding total run sizes of 550-19,800 (Table 10). Total recent run size for major stocks in this ESU was greater than 45,000, with total natural escapement of about 22,000. The geographic distribution of escapement is illustrated in Figure 19.

There are substantial habitat blockages by dams in the Skagit and Elwha River Basins, and minor blockages, for example, impassable culverts, throughout the region. The Washington State salmon and steelhead stock inventory (SASSI) (WDF et al. 1993) appendices note habitat problems, including flooding, unstable soils, and poor land management practices, for most stocks in this region. In general, habitat has been degraded from its pristine condition, and this trend is likely to continue with further population growth and resultant urbanization in the Puget Sound region. Because of their limited distribution in upper tributaries, summer steelhead appear to be at more risk from habitat degradation than are winter steelhead.

Of the 21 independent stocks for which we had adequate adult escapement information to compute trends (Appendix E), 17 have been declining and 4 increasing during the available data series, with a range from 18% annual decline (Lake Washington winter steelhead) to 7% annual increase (Skykomish River winter steelhead). Eleven of these trends (9 negative, 2 positive) were significantly different from zero. Note that these trends are for the late run wild component of winter steelhead populations; no adult trend data are available for summer steelhead. In addition, most of these trends are based on relatively short data series and may be influenced by recent climate conditions. The two basins producing the largest numbers of steelhead (Skagit and Snohomish Rivers) both have overall upward trends. Trends for individual river basins are summarized in Table 10 and Figure 20.

Hatchery fish are widespread, spawn naturally throughout the Puget Sound region, and are largely derived from a single stock (Chambers Creek). The proportion of spawning escapement comprised of hatchery fish ranged from less than 1% (Nisqually River) to 51% (Morse Creek). In general, hatchery proportions are higher in Hood Canal and the Strait of Juan de Fuca than in Puget Sound proper (Table 10). Most hatchery fish in this region originated from stocks indigenous to the ESU, but they are generally not native to their local river basins. WDFW has provided information supporting substantial temporal separation between hatchery and natural winter steelhead in this region. Given the lack of strong trends in abundance for the major stocks and the apparent limited contribution of hatchery fish to production of the late-run winter stocks, most winter steelhead stocks in the Puget Sound ESU appear to be naturally self-sustaining at this time. However, there are clearly isolated problems with sustainability of some steelhead runs in this ESU, notably with Deer Creek summer steelhead (although juvenile abundance for this stock increased in 1994) and with Lake Washington winter steelhead. Summer steelhead stocks within this ESU are all small, occupy limited habitat, and in most cases are subject to introgression by hatchery fish. While there are few data to assess the status of these summer runs, there is cause for concern regarding their sustainability.

At present, the major threat to genetic integrity for Puget Sound steelhead comes from past and present hatchery practices. Risk factors relating to hatchery practices were discussed previously in the Background section.

2) Olympic Peninsula--Previous assessments of stocks within this ESU have not identified any stocks as being at risk or of special concern. Nehlsen et al. (1991) identified no stocks as at risk (Table 9). WDF et al. (1993) considered 31 stocks within the ESU, of which 23 were considered to be of native origin and predominantly natural production. The status of these 23 stocks was assessed as 11 healthy and 12 unknown, while the status of the eight remaining (not native/natural) stocks was two healthy and six unknown (Appendix E).

No estimates of historical (pre-1960s) abundance specific to the Olympic Peninsula ESU are available. Total run size for the major stocks in the Olympic Peninsula ESU during the early 1980s was calculated from estimates in Light (1987) as approximately 60,000 winter steelhead. Light provided no estimate of hatchery proportion in these streams, but for Puget Sound and coastal Washington together, he estimated that 70% of steelhead were of hatchery origin. Recent 5-year average natural escapements for streams with adequate data range from 250 to 6,900, with corresponding total run sizes of 450-19,700 (Table 11, Appendix E). Total recent (1989-93 average) run size for major streams in this ESU was approximately 54,000, with a natural escapement of 20,000 fish. The geographic distribution of this escapement is illustrated in Figure 19.

No major habitat blockages are known for these streams, but minor blockages (such as impassable culverts) are likely throughout the region. SASSI appendices (WDF et al. 1993) note freshwater habitat problems largely relating to poor land management practices, and recent poor ocean productivity affecting most stocks in this region. Clearcut logging has been extensive throughout most watersheds in this area, with the exception of the upper reaches of the larger rivers that drain Olympic National Park. Because of their limited distribution in upper tributaries, summer steelhead appear to be at more risk from habitat degradation than winter steelhead.

Of the 12 independent stocks for which we had adequate adult escapement information to compute trends (Appendix E), 7 have been declining and 5 increasing during the available data series, with a range from 8% annual decline to 14% annual increase. Three of the downward trends were significantly different from zero, but three of the four river basins producing the largest numbers of natural fish have upward trends in basinwide total numbers (Table 11, Fig. 20). Note that these trends are all for winter steelhead populations; no adult trend data are available for summer steelhead.

Hatchery fish are widespread and escaping to spawn naturally throughout the region, with hatchery production largely derived from a few parent stocks. Estimated proportions of hatchery fish in natural spawning habitat range from 16% (Quillayute River) to 44% (Quinault River). However, the two largest producers of natural fish (Quillayute and Queets Rivers) had the lowest proportions. WDFW has provided information supporting substantial temporal separation between hatchery and natural winter steelhead in this region. Given the lack of strong trends in abundance and the apparent limited contribution of hatchery fish to production of the late-run winter stocks, most winter steelhead stocks in the Olympic Peninsula ESU appear to be naturally sustaining at this time. However, there are clearly isolated problems with sustainability of some winter steelhead runs in this ESU, notably the Pysht/Independents stock, which has a small population with a strongly declining trend over the available data series (even though it has been exceeding harvest management goals recently), and the Quinault River stock, which has a declining trend and substantial hatchery contribution to natural spawning.

At present, the major threat to genetic integrity for Olympic Peninsula steelhead comes from past and present hatchery practices. Risk factors relating to these hatchery practices were discussed previously in the Background section.

3) Southwest Washington--Previous assessments within this ESU have identified several stocks as being at risk or of special concern. Nehlsen et al. (1991) identified three stock groups as at risk or of concern: moderate risk for small Columbia River tributaries and special concern for the Grays and Elochoman Rivers (Table 9). WDF et al. (1993) considered 22 stocks within the ESU, of which 19 were considered to be of native origin and predominantly natural production. The status of these 19 stocks was 6 healthy, 6 depressed, and 7 unknown. The status of the remaining three stocks (not native/natural or unknown origin) was one healthy, one depressed, and one unknown. Most healthy stocks were in tributaries to Grays Harbor, and most depressed stocks were in lower Columbia River tributaries (Appendix E).

No estimates of historical (pre-1960s) abundance specific to this ESU are available. Recent 5-year average natural escapements in individual tributaries with adequate data range from 150 to 2,300, with the Chehalis River and its tributaries representing the bulk of production (Appendix E). Total recent (5-year average) natural escapement for major streams in this ESU was approximately 13,000 (Table 12). The geographic distribution of escapement is illustrated in Figure 19.

No major habitat blockages are known for these streams, but minor blockages (such as impassable culverts) are likely throughout the region. Habitat problems for most stocks in this ESU are similar to those in adjacent coastal ESUs. Clearcut logging has been extensive throughout most watersheds in this area. Because of their limited distribution in upper tributaries, summer steelhead appear to be at more risk from habitat degradation than are winter steelhead.

All but one (Wynoochee River) of the 12 independent stocks for which we had adequate adult escapement information to compute trends (Appendix E) have been declining during the available data series, with a range from 7% annual decline to 0.4% annual increase. Six of the downward trends were significantly different from zero. However, most of the data series used for trend calculations were short, beginning in the mid-1980s; thus, the trends may largely reflect the effects of recent climate conditions.

For Washington streams, these trends are for the late run wild component of winter steelhead populations; Oregon data included all stock components. Most of the Oregon trends are based on angler catch data, and so may not reflect trends in underlying population abundance (see discussion for the Oregon Coast ESU). In general, stock condition appears to be healthier in southwest Washington than in the lower Columbia River Basin (Appendix E). Trends for individual river basins are summarized in Table 12 and Figure 20.

Hatchery fish, largely from parent stocks outside the ESU, are widespread and escaping to spawn naturally throughout the region. This 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 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. WDFW has provided information supporting substantial temporal separation between hatchery and natural winter steelhead in this region. However, some Washington stocks (notably lower Columbia River tributaries-- Table 12) appear to have received substantial hatchery contributions to their wild spawning components, and Nehlsen et al. (1991) identified two stocks in this ESU as of special concern due to hatchery influence (Table 9).

The preponderance of negative trends in abundance, the contribution of non-native hatchery fish to production, and the poor condition of stocks in lower Columbia River tributaries are causes for concern for the future of this ESU.

Again 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.

4) Lower Columbia River--Previous assessments within this ESU have identified several stocks as being at risk or of special concern. Nehlsen et al. (1991) identified 19 stocks as at risk or of concern (Table 9). WDF et al. (1993) considered 23 stocks within the ESU, of which 19 were considered to be of native origin and predominantly natural production. The status of these 19 stocks was 2 healthy, 10 depressed, and 7 unknown. All four of the remaining (not native/natural or unknown origin) stocks were classified as depressed.

No estimates of historical (pre-1960s) abundance specific to this ESU are available. Total run size for the major stocks in the lower Columbia River (below Bonneville Dam, including the upper Willamette ESU) for the early 1980s can be calculated from the estimates of Light (1987) as approximately 150,000 winter steelhead and 80,000 summer steelhead. Light estimated that 75% of the total run (summer and winter steelhead combined) was of hatchery origin. Recent 5-year average natural escapements for streams with adequate data range from less than 100 to 1,100 (Table 13, Appendix E). Total recent (5-year average) run size for major streams in this ESU was greater than 16,000, but this total includes only the few basins for which estimates are available. The geographic distribution of escapement is illustrated in Figure 19.

Significant habitat blockages resulted from dams on the Sandy River, and minor blockages (such as impassable culverts) are likely throughout the region. Habitat problems for most stocks in this ESU are similar to those in adjacent coastal ESUs. Clearcut logging has been extensive throughout most watersheds in this area, and urbanization is a substantial concern in the Portland and Vancouver areas. Because of their limited distribution in upper tributaries, summer steelhead appear to be at more risk from habitat degradation than are winter steelhead.

Of the 18 stocks for which we had adequate adult escapement information to compute trends (Appendix E), 11 have been declining and 7 increasing during the available data series, with a range from 24% annual decline to 48% annual increase. Eight of these trends (five negative, three positive) were significantly different from zero. Most of the data series for this ESU are short, beginning only in the late 1970s to the mid-1980s; thus they may be heavily influenced by short-term climate effects. Some of the Washington trends (notably those for the Cowlitz and Kalama River Basins) have been influenced (positively or negatively) by the 1980 eruption of Mount St. Helens; we have not attempted to correct for this here. For Washington streams, these trends are for the late run wild component of winter steelhead populations; Oregon data included all stock components. Most of the Oregon trends are based on angler catch, and so they may not reflect trends in underlying population abundance--see discussion under the Oregon Coast ESU. Trends for individual river basins are summarized in Table 13 and Figure 20.

Hatchery fish are widespread and escaping to spawn naturally throughout the region. Most of the hatchery stocks used originated primarily from stocks within the ESU, but many are not native to local river basins. WDFW has provided information supporting substantial temporal separation between hatchery and natural winter steelhead in this region; however, some Washington stocks (notably Kalama River winter and summer steelhead--Appendix E) appear to have substantial hatchery contribution to wild spawning, and Nehlsen et al. (1991) identified several stocks in this ESU as of special concern due to hatchery influence (Table 9). ODFW estimates of hatchery composition indicate a range from about 30% (Sandy River and Tanner Creek winter steelhead) to 80% (Hood River summer steelhead) hatchery fish in spawning escapements. Estimates for Hood River winter steelhead range from 0% (ODFW 1995b) to greater than 40% (ODFW 1995a). Given the relatively low natural run sizes to individual streams, the preponderance of negative trends in abundance, and the apparent substantial contribution of hatchery fish to production, the BRT had substantial concern that the majority of natural steelhead populations in this ESU (both winter and summer) may not be self-sustaining.

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 under Background above.

5) Upper Willamette River--The only previous assessment of risk to stocks within this ESU is that of Nehlsen et al. (1991), who identified one stock (Calapooia River) as of special concern (Table 9).

No estimates of historical (pre-1960s) abundance specific to this ESU are available. Total recent 5-year average run size for this ESU can be estimated from counts at Willamette Falls for the years 1989-93. Dam counts indicate that the late-run (native) winter steelhead average run size was approximately 4,200, while early-run winter and summer steelhead averaged 1,900 and 9,700, respectively (Table 14, Fig. 21, Appendix E). Only the late-run winter steelhead are included in this ESU; other runs are mentioned because of their possible ecological interactions with the native stock. Adequate angler catch data were available to derive approximate average winter steelhead escapement for three tributaries: Mollala River, 2,300 (predominantly non-native); North Fork Santiam River, 2,000; South Fork Santiam River, 550.

Substantial habitat blockages resulted from Detroit, Big Cliff and Green Peter Dams on the Santiam River, and flood control dams on the mainstem Willamette. Other blockages such as smaller dams or impassable culverts are likely throughout the region. Habitat problems for most stocks in this ESU are similar to those in adjacent coastal ESUs. Clearcut logging has been common throughout most watersheds in this area, and there is extensive urbanization in the Willamette Valley. Bottom et al. (1985) identified specific factors affecting salmon habitat in various areas of Oregon, including streamflow and temperature problems, riparian habitat losses, and instream habitat problems. Within the Willamette Valley, they noted that temperatures and streamflows reach critical levels for salmonids in places where there are significant water withdrawals or removal of streamside vegetation, that loss of riparian vegetation results from agricultural practices and rural and urban development, that bank erosion is severe in several areas of the basin, and that splash dams, debris removal and stream channelization have caused long-term damage to salmonid habitats.

Total basin run size or escapement estimates exhibit declines for both total winter and late winter steelhead, while summer steelhead estimates exhibit an increase (Table 14, Fig. 22). However, all of these basinwide estimates have exhibited large fluctuations (Fig. 23). Of the three tributary winter steelhead stocks for which we had adequate adult escapement information to compute trends, two have been declining and one increasing over the available data series, with a range from 4.9% annual decline to 2.4% annual increase. None of these trends were significantly different from zero (Table 14, Appendix E). Note that two of these trends, those from the North and South Forks of the Santiam River, are based on angler catch, and so may not reflect trends in underlying population abundance--see discussion for the Oregon Coast ESU.

Hatchery fish are widespread throughout the region. Both summer steelhead and early- run winter steelhead have been introduced to the basin and escape to spawn naturally in substantial numbers. Indigenous late-run winter steelhead are also produced in the Santiam River Basin. Estimates of hatchery composition for winter steelhead escapements are available only for the North Fork Santiam River and the Mollala River. These estimates are variable, ranging from 14% (ODFW 1995b) to 54% (ODFW 1995a) on the North Fork Santiam River alone. There is probably some temporal and spatial separation in spawning between the early and late winter stocks. While we have little information on the actual contribution of hatchery fish to natural production, given the generally low numbers of fish escaping to tributaries and the general declines in winter steelhead abundance in the basin, the BRT had substantial concern that the majority of natural winter steelhead populations in this ESU may not be self-sustaining. All summer steelhead within the range of this ESU are introduced from outside the area, so are not considered as contributing to natural production of the ESU. Natural reproduction by these introduced summer steelhead may be quite limited.

The major present threat to genetic integrity for steelhead in this ESU comes from past and present hatchery practices. While there is some separation in run timing between hatchery and wild winter steelhead, there appears to be sufficient overlap in spawn timing for some genetic introgression from nonlocal hatchery stocks to occur. An additional effect of hatchery production may be directional selection within the natural stocks resulting both from competition with hatchery fish (both winter and summer) and selective fishing pressure that eliminates individuals with early run timing from the natural stocks. Other risk factors relating to hatchery practices were discussed previously in the Background section.

6) Oregon Coast--Previous assessments within this ESU have identified several stocks as being at risk or of special concern. Nehlsen et al. (1991) identified 12 stocks as extinct, at risk, or of special concern (Table 9). Most of the stocks of special concern were classified as such due to hatchery practices. ODFW (Nickelson et al. 1992) considered 21 stocks within the ESU, of which 3, North Umpqua River summer and winter steelhead and Coquille River winter steelhead, were identified as healthy, 17 as depressed, and 1 (Necanicum River) of special concern.

No estimates of historical (pre-1960s) abundance specific to this ESU are available, except for counts at Winchester Dam on the North Umpqua River which began in 1946, and angler catch records which began in 1953. Early angler catch summaries did not distinguish summer and winter steelhead and were not corrected for nonreporting bias, so these have not been relied on in this review. Estimated total run size for the major stocks on the Oregon Coast (including areas south of Cape Blanco) for the early 1980s were given by Light (1987) as approximately 255,000 winter steelhead and 75,000 summer steelhead. Light estimated that 69% of winter and 61% of summer steelhead were of hatchery origin, resulting in naturally produced run sizes of 79,000 winter and 29,000 summer steelhead.

Recent 5-year average total (natural and hatchery) run sizes for streams with adequate data range from 250 to 15,000, corresponding to escapements from 200 to 12,000 (Table 15, Appendix E). Total recent (5-year average) run size for major streams in this ESU was approximately 129,000 (111,000 winter, 18,000 summer), with a total escapement of 96,000 (82,000 winter, 14,000 summer). These totals do not include all streams in the ESU, so they underestimate total ESU run size and escapements. The geographic distribution of escapement is illustrated in Figure 21. Run size and escapement estimates are also based primarily on expansions of angler catch using assumed harvest rates (Kenaston 1989), so they should be viewed as rough approximations.

Regarding freshwater habitat, several minor blockages from dams are documented, and other blockages such as impassable culverts are likely throughout the region. Bottom et al. (1985) identified specific factors affecting salmon habitat in various areas of Oregon, including streamflow and temperature problems, riparian habitat losses, and instream habitat problems. They noted that along the Oregon Coast summer temperatures and streamflow reach critical levels for salmonids in areas where there are significant water withdrawals or removal of streamside vegetation had occurred. They reported notable temperature problems in Tillamook Bay tributaries and the Alsea, Siletz, Siuslaw, and Umpqua Rivers. Bottom et al. (1995) also found that loss of riparian vegetation has resulted from agricultural and forestry practices, and that splash dams, debris removal, and stream channelization had caused long-term damage to salmonid habitats.

Sport harvest information was the main abundance data available for most Oregon coastal populations. In 1952, Oregon instituted a punchcard system to record all salmon and steelhead caught by species. However, methods of estimating and reporting catch changed in 1970, and division of catch statistics among tributaries changed substantially in 1977, so earlier data are not directly comparable to those since 1977. Our analyses for Oregon river basins focussed on data collected since those changes (ODFW 1980, 1992, 1993), although trends from longer-term data have been included for comparison in some basins (Appendix E).

Interpreting population abundance from angler catch data presents several problems. First, numbers of fish caught do not directly represent abundance, which must be estimated by applying assumptions about fishing effort and effectiveness. Fishing effort is largely determined by socioeconomic factors, including fishery regulations. Fishing effectiveness is a function of both the skill of the anglers and environmental conditions which affect behavior of both fish and anglers. Both effort and effectiveness may exhibit long-term trends and interannual fluctuations that can obscure the relationship between catch and abundance.

Second, estimates of catch may not be accurate. In Oregon, catch is estimated from returns of punchcards and estimates are corrected for nonreporting bias. While catch estimates are generated separately for each stream basin, the bias correction is calculated statewide and may not be accurate for any particular stream due to local variations in the tendency to return punchcards.

Third, when fishing effort varies across a river basin, catch may reflect only local abundance rather than the total basin population. However, statewide salmon and steelhead fishing effort, as indexed by number of punchcards issued, has been relatively constant since the late 1970s, indicating that angler catch may accurately reflect trends in abundance over large geographic areas. ODFW (1995b) provided evidence that the relationship of angler catch to spawner abundance is weak in some basins, although there is generally a positive correlation. Additionally, fishing effort has been increasingly focused on hatchery fish in recent years, with wild catch and release regulations imposed in many Oregon coastal streams in January 1992 (ODFW 1995b). Thus, recent trends may reflect hatchery production more than natural production throughout the Oregon coast. Trend estimates reported here include angler catch data through 1992 (Table 15, Appendix E). To test for bias due to wild catch and release regulations, we also calculated trends excluding the 1991 and 1992 run years. While the resulting estimates were often different for individual basins, both upward and downward changes were apparent, and overall patterns were similar to those obtained by using the full data set.

The following analysis was made with the assumption that catch trends reflect trends in overall population abundance. We recognize the many problems with this assumption and that the results may not precisely represent trends in the total population in a river basin. However, angler catch is the only information available for most of these populations, and we believe that changes in catch still provide a useful indication of trends in total population abundance. Where alternate trend data were available, we used those data instead of angler catch.

Adequate adult escapement information was available to compute trends for 42 independent stocks within this ESU. Of these, 36 stocks exhibited declines and 6 exhibited increases during the available data series. Trends ranged from a 12% annual decline in Drift Creek on the Siletz River to a 16% annual increase in North Fork Coquille River. Twenty of these trends were significantly different from zero with 18 decreasing and 2 increasing (Appendix E). Upward trends were found only in the southernmost portion of the ESU (Fig. 22), from Siuslaw Bay south. In contrast, longer term trends in angler catch, using data from the early 1950s to the present, generally were increasing. This may reflect longer term stability of populations, or may be an artifact of long-term increases in statewide fishing effort coupled with the differences in bias correction of catch summaries before and after 1970.

Hatchery fish are widespread and escape to spawn naturally throughout the region. Most hatchery stocks used in this region originated from stocks indigenous to the ESU, but many are not native to local river basins. ODFW estimates of hatchery composition for recent winter steelhead escapements were high in many streams, ranging from 10% in the North Umpqua River to greater than 80% in Drift Creek on the Alsea River and in Tenmile Creek south of Umpqua Bay. For summer steelhead, hatchery composition (where reported) ranged from 38% in the South Umpqua River to 90% in the Siletz River. Several summer steelhead stocks have been introduced to rivers with no native summer runs.

Overall, approximately half of the stocks in this ESU for which we have information have hatchery composition in excess of 50%. Few stocks in the region are documented to have escapements above 1,000 fish and no significant decline (Appendix E); most of those that do are in the southern portion of the ESU and have high hatchery influence. While we have little information on the actual contribution of hatchery fish to natural production, given the substantial presence of hatchery fish in the few stocks that are relatively abundant and stable or increasing, the BRT had substantial concern that the majority of natural steelhead populations in this ESU may not be self-sustaining.

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.

7) Klamath Mountains Province--This ESU has been evaluated previously (Busby et al. 1994), and is not discussed here.

8) Northern California--Previous assessments within this ESU have identified several stocks as being at risk or of special concern. Nehlsen et al. (1991) identified three stocks as at risk of extinction: summer steelhead in Redwood Creek, Mad River, and Eel River (Table 9). Higgins et al. (1992) provided a more detailed analysis of some of these stocks and identified 11 summer steelhead stocks as at risk or of concern. They did not evaluate winter steelhead stocks because of insufficient information. The USFS (1993b) identified most stocks on Forest Service lands in this region as either depressed or critical, with only the Little Van Duzen River winter steelhead stock identified as stable (Appendix E).

Estimates of historical (pre-1960s) abundance specific to this ESU were available (Table 16) from dam counts in the upper Eel River (Cape Horn Dam--annual average of 4,400 adult steelhead in the 1930s; McEwan and Jackson 1996), the South Fork Eel River (Benbow Dam--annual average of 19,000 adult steelhead in the 1940s; McEwan and Jackson 1996), and the Mad River (Sweasey Dam--annual average of 3,800 adult steelhead in the 1940s; Murphy and Shapovalov 1951, CDFG 1994). In the mid-1960s, CDFG (1965, table S-3) estimates steelhead spawning populations for many rivers in this ESU totaled 198,000 (Table 17). Estimated total run size for the major stocks in California (entire state) for the early 1980s was given by Light (1987) as approximately 275,000. Of these, 22% were of hatchery origin, resulting in a naturally produced run size of 215,000 steelhead. Roughly half of this production was thought to be in the Klamath River Basin (including the Trinity River), so the total natural production for all ESUs south of Punta Gorda was probably on the order of 100,000 adults. The only current run-size estimates for this area are counts at Cape Horn Dam on the Eel River where an average of 115 total and 30 wild adults were reported (McEwan and Jackson 1996). Summer steelhead snorkel survey data are available for a few tributaries, but they provide no total abundance estimate. Statewide adult summer steelhead abundance is estimated at about 2,000 adults (McEwan and Jackson 1996). Note that estimate apparently refers only to early-summer steelhead entering the rivers in May, June, and July, not including the more numerous "fall-run" steelhead. While we have no overall recent abundance estimate for this ESU (Table 18, Fig. 24), the substantial declines in run size from historic levels at major dams in the region (Table 16) indicate a probable overall decline in abundance from historical levels.

Two substantial habitat blockages are documented: Mathews Dam on the Mad River and Scott Dam on the Eel River (McEwan and Jackson 1996), and other minor blockages (such as impassable culverts) are likely throughout the region. Habitat throughout the north coast of California 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 (Higgins et al. 1992, McEwan and Jackson 1996). Excessive sedimentation and unstable spawning gravels are cited as major habitat problems in this region (CDFG 1991, Higgins et al. 1992). Other habitat problems similar to those cited for the Oregon Coast ESU probably also occur in this region. A high abundance of non-native Sacramento squawfish (Ptychocheilus grandis) has been reported recently in the Eel River Basin (Brown and Moyle 1991, Moyle and Yoshiyama 1992), which would suggest increased risk of predation for juvenile steelhead.

Adequate adult escapement information was available to compute trends for seven stocks within this ESU (Table 18, Fig. 25). Of these, five data series exhibit declines and two exhibit increases during the available data series, with a range from 5.8% annual decline to 3.5% annual increase. Three of the declining trends were significantly different from zero (Appendix E). For one long data set (Eel River, Cape Horn Dam counts), a separate trend for the last 21 years (1971-91) was calculated for comparison: while the full-series trend showed significant decline, the recent data showed a lesser, nonsignificant decline, suggesting that the major stock decline occurred prior to 1970.

Hatchery fish are widespread and escaping to spawn naturally throughout the region. According to McEwan and Jackson (1996, p. 37), "despite the large number of hatchery smolts released, steelhead runs in north coast drainages are comprised mostly of naturally produced fish." We have little information on the actual contribution of hatchery fish to natural spawning, and little information on present total run sizes for this ESU. However, given the preponderance of significant negative trends in the available data, there is concern that steelhead populations in this ESU may not be self-sustaining.

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. Within this ESU, we have no information regarding spatial or temporal separation of spawning hatchery and natural fish, but there is probably sufficient overlap for some genetic introgression to occur.


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