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

NOAA-NWFSC Tech Memo-27: Status Review of West Coast Steelhead
ASSESSMENT OF EXTINCTION RISK

Background

As outlined in the Introduction above, NMFS considers a variety of information in evaluating the level of risk facing an ESU. Aspects of several of these risk considerations are common to all west coast steelhead ESUs. These are discussed in general below; more specific discussion of factors for each of the 14 ESUs under consideration here can be found in the following sections. The status of the Klamath Mountains Province ESU (ESU 7), has already been considered (Busby et al. 1994), and is referred to here only for comparison.

Absolute Numbers

The absolute number of individuals in a population is important in assessing two aspects of extinction risk. First, for small populations that are stable or increasing, population size can be an indicator of whether the population can sustain itself into the future in the face of environmental fluctuations and small-population stochasticity; this aspect is related to the concept of minimum viable populations (MVP) (Gilpin and Soulé 1986, Thompson 1991). Second, for a declining population, the present abundance is an indicator of the expected time until the population reaches critically low numbers; this aspect is related to the concept of "driven extinction" (Caughley 1994).

In addition to total numbers, the spatial and temporal distribution of adults is important in assessing risk to an ESU. Spatial distribution is important both at the scale of river basins within an ESU and at the scale of spawning areas within basins ("metapopulation" structure). Temporal distribution is important both among years, as an indicator of the relative health of different brood-year lineages, and within seasons, as an indicator of the relative abundance of different life history types or runs.

Traditionally, assessment of salmonid populations has focused on the number of harvestable or reproductive adults, and these measures comprise most of the data available for Pacific salmon and steelhead. In assessing the future status of a population, the number of reproductive adults is the most important measure of abundance, and we focussed on measures of the number of adults escaping to spawn in natural habitat. However, total run size (spawning escapement + harvest) is also important because it indicates potential spawning in the absence of harvest. Data on other life history stages (e.g., freshwater smolt production) can be used as supplemental indicators of abundance.

Because the ESA (and NMFS policy) mandates that we focus on viability of natural populations, we attempted to distinguish natural fish from hatchery produced fish in this review. All statistics were based on data that indicated the total number or density of adults spawning in natural habitat (i.e., "naturally spawning fish"). The total of all naturally spawning fish (i.e., "total escapement") is divided into two components (Fig. 18): "Hatchery produced" fish which are reared as juveniles in a hatchery but return as adults to spawn naturally; and "natural" fish which are progeny of naturally spawning fish.

Figure 18
Figure 18. Schematic diagram of mixing of naturally and hatchery produced fish in natural habitat. Ovals represent the total spawning in natural habitat each generation. This total can be composed of naturally produced (N) and hatchery produced (H) offspring of individuals in the previous generation.

Historical Abundance and Carrying Capacity

The relationship of current abundance and habitat capacity to that which existed historically is an important consideration in evaluating risk. Knowledge of historical population conditions provides a perspective of the conditions under which present stocks evolved, as well as the basis for establishing long-term trends in populations. Comparison of present and past habitat capacity can also indicate long-term population trends and problems of population fragmentation. The relationship of present abundance to present carrying capacity is important for understanding the health of populations, but the fact that a population is near its current capacity does not in itself mean that it is healthy. For a population that is near capacity, there may be limits to the effectiveness of short-term management actions in increasing abundance. For such a population, competition and other interactions between hatchery and natural fish may also be important considerations because the addition of hatchery fish may further increase population density in a limited habitat.

For steelhead, quantitative abundance estimates are rarely available for periods before the 1950s. The main exceptions are long-term counts at dams in the Columbia River Basin and northern California that extend back to the 1930s or 1940s. Quantitative assessments of habitat are quite rare, although rough estimates of carrying capacity are frequently made for setting management goals. From the evidence available, it is clear that production of natural steelhead is now substantially below historical levels for all ESUs considered here, although this decline in natural production has been offset to a variable extent by increasing hatchery production in many areas.

Although no analysis of the proportion of total habitat lost due to blockages has been attempted by us, there have been significant blockages of freshwater habitat in every ESU. Freshwater and estuarine habitats are also degraded throughout the entire region considered here, although the severity of degradation varies among ESUs and is described in the individual ESU summaries below.

Trends in Abundance

Short- and long-term trends in abundance are a primary indicator of risk in salmonid populations. Trends may be calculated from a variety of quantitative data, including dam or weir counts, stream surveys, and catch data. These data sources and methods are discussed in more detail below, under Approach to Risk Assessment. Regular sampling has not been conducted for many steelhead populations, and data series are quite short for most of those populations with sampling data. Where data series were lacking, we inferred general trends by comparing historical and recent abundance estimates, or by considering trends in habitat quantity or condition.

The important role of artificial propagation (in the form of hatcheries) for Pacific salmon and steelhead requires careful consideration in ESA evaluations. Artificial propagation has implications both for evaluating production trends and for evaluating the genetic integrity of populations. Waples (1991b) and Hard et al. (1992) discussed the role of artificial propagation in ESU determinations and emphasized the need to focus on natural production in a threatened or endangered status determination. To address this need, and because of the ESA's emphasis on ecosystem conservation, our analysis focused on naturally reproducing steelhead. A fundamental question in ESA risk assessments is whether natural production is sufficient to maintain the population without the continued infusion of artificially produced fish. A full answer to this question is difficult without extensive studies of relative production and interactions between hatchery and natural fish. When such information is lacking, the presence of hatchery fish in natural populations leads to substantial uncertainty in evaluating the status of a natural population.

One method of approaching this issue is to calculate the natural cohort replacement ratio, defined as the number of naturally spawning adults that are naturally produced in one generation divided by the number of naturally spawning adults (regardless of parentage) in the previous generation. Because data for steelhead are rarely sufficient for this calculation, we did not attempt to estimate this ratio in this report. However, the ratio can be approximated from the average population trend if the degree of hatchery contribution to natural spawning can be estimated (Busby et al. 1994, Appendix B). Where such estimates were available, the presence of hatchery fish among natural spawners was taken into consideration in evaluating the sustainability of natural production for individual populations within the ESUs identified.

Recent coastwide trends in steelhead abundance provided a larger perspective for this review. Between the 1890s and the 1960s, total U.S. commercial catch of steelhead declined sevenfold, but this may reflect restrictions on the fishery more than declines in abundance. Rough estimates of total coastwide steelhead run size made in 1972 and 1987 were similar (Sheppard 1972, Light 1987). By all accounts, however, there has been significant replacement of natural production with hatchery fish. Throughout British Columbia, Washington, and Oregon, both natural and hatchery steelhead stocks have exhibited recent decreases in survival, which may be due at least in part to climate and ocean production (Cooper and Johnson 1992).

Factors Causing Variability

Variations in the freshwater and marine environments is thought to be a primary factor driving fluctuations in salmonid run size and escapement (Pearcy 1992, Beamish and Bouillon 1993, Lawson 1993). Changes in ocean condition are discussed below under Recent Events Affecting Extinction Risk. Habitat degradation and harvest have probably made stocks less resilient to poor climate conditions, but these effects are not easily quantifiable.

Threats to Genetic Integrity

In addition to its effect on natural replacement rates, artificial propagation can have a substantial impact on the genetic integrity of natural salmon and steelhead populations. This can occur in several ways. First, stock transfers that result in interbreeding of hatchery and natural fish can lead to loss of fitness in local populations and loss of diversity among populations. The latter is important to maintaining long-term viability of an ESU because genetic diversity among salmonid populations helps to buffer overall productivity against periodic or unpredictable changes in the environment (Riggs 1990, Fagen and Smoker 1989). Ricker (1972) and Taylor (1991) summarized some of the evidence for local adaptations in Pacific salmonids that may be at risk from stock transfers.

Second, because a successful salmon or steelhead hatchery dramatically changes the mortality profile of a population, some level of genetic change relative to the wild population is inevitable even in hatcheries that use local broodstock (Waples 1991a). These changes are unlikely to be beneficial to naturally reproducing fish.

Third, even if naturally spawning hatchery fish leave few or no surviving offspring, they still can have ecological and indirect genetic effects on natural populations. On the spawning grounds, hatchery fish may interfere with natural production by competing with natural fish for territory or mates and, if they are successful in spawning with natural fish, may divert production from more productive natural X natural crosses. The presence of large numbers of hatchery juveniles or adults may also alter the selective regime faced by natural fish.

For smaller steelhead stocks (either natural or hatchery), small-population effects (inbreeding, genetic drift) can also be important concerns for genetic integrity. Inbreeding and genetic drift are well understood at the theoretical level, and researchers have found evidence of inbreeding depression in various fish species (Allendorf and Ryman 1987). Other studies have shown that hatchery practices commonly used with anadromous Pacific salmonids have the potential to affect genetic integrity (e.g., Simon et al. 1986, Withler 1988, Waples and Teel 1990). However, we are not aware of empirical evidence for inbreeding depression or loss of genetic variability in any natural or hatchery populations of Pacific salmon or steelhead.

One type of genetic change in hatchery populations--advancement of run timing--is particularly relevant to west coast steelhead because it is a commonly used management strategy, particularly in Washington state. The logic behind this strategy is that displacing the run timing of hatchery fish from that of natural populations will reduce the possibility for genetic interactions between hatchery and natural fish and will allow for selective harvest of hatchery fish. For coastal steelhead in Washington, WDFW has provided information indicating substantial separation in peak run timing between hatchery and natural winter steelhead, and this pattern may occur in other coastal areas as well. However, run timing separation is seldom complete, and WDFW has found genetic evidence for substantial hatchery introgression in several winter steelhead populations (Phelps et al. 1994; see discussion under Steelhead Genetics, page 37). This issue is discussed further below under Approach to Risk Assessment (see page 103).

Recent Events Affecting Extinction Risk

A variety of factors, both natural and human-induced, affect the degree of risk facing salmonid populations. Because of time lags between these events and their effects, as well as variability within populations, recent changes in any of these factors may affect current risk without any apparent change in available population statistics. Thus, consideration of these effects must go beyond examination of recent abundance and trends. Unfortunately, forecasting future effects is rarely straightforward and usually involves qualitative evaluations based on informed professional judgement. Events affecting populations may include natural changes in the environment or human-induced changes, either beneficial or detrimental. Possible future effects of recent or proposed conservation measures have not been taken into account in this analysis, but we have considered documented changes in the natural environment. A key question regarding the role of recent events is, given our uncertainty regarding the future, how we evaluate the risk that a population may not persist.

Most Pacific salmonid stocks south of British Columbia have been affected by changes in ocean production that occurred during the 1970s (Pearcy 1992, Lawson 1993). Cooper and Johnson (1992) described a widespread decline in both natural and hatchery steelhead production since 1985, extending from British Columbia through Oregon. They attributed this decline largely to ocean factors but did not identify specific effects. However, climate conditions are known to have changed recently in the Pacific Northwest and much of the Pacific coast has also been experiencing drought conditions in recent years, which may have depressed freshwater production. We do not know whether these climate conditions represent a long-term shift in conditions which will continue affecting stocks into the future, or whether they indicate short-term environmental fluctuations which may be reversed in the near future.

Other Risk Factors

Other risk factors typically considered for salmonid populations include disease prevalence, predation, and changes in life history characteristics such as spawning age or size. We have not found evidence that any of these factors are widespread throughout any steelhead ESU. Various diseases have been reported as problems in some hatcheries, but we have found no reports of substantial disease problems in natural steelhead populations.

Bacterial kidney disease, Ceratomyxa shasta, and infectious hematopoietic necrosis are reported to be problems within steelhead hatcheries in northern California (Foott et al. 1994). Chapman et al. (1994) reported several diseases in Columbia River Basin steelhead hatcheries. Predation by marine mammals or introduced freshwater fishes is important for individual populations, as noted in the ESU summaries below.

Approach to Risk Assessment

Previous Assessments

In considering the status of ESUs, we evaluated both qualitative and quantitative information. Qualitative evaluations included aspects of several of the risk considerations outlined above, as well as recent, published assessments by agencies or conservation groups of the status of west coast steelhead stocks (Nehlsen et al. 1991; Higgins et al. 1992; Nickelson et al. 1992; WDF et al. 1993; USFS 1993a,b; Titus et al. in press). These evaluations are summarized in Appendix E.

Nehlsen et al. (1991) considered salmonid stocks throughout Washington, Idaho, Oregon, and California and enumerated all stocks that they found to be extinct or at risk of extinction. Stocks that did not appear in their summary were excluded either because they were not at risk of extinction or there was insufficient information to classify them. They classified stocks as extinct (X), possibly extinct (A+), at high risk of extinction (A), at moderate risk of extinction (B), or of special concern (C). They considered it likely that stocks at high risk of extinction have reached the threshold for classification as endangered under the ESA. Stocks were placed in this category if they had declined from historic levels and were continuing to decline, or if they had spawning escapements less than 200. Stocks were classified as at moderate risk of extinction if they had declined from historic levels but appeared to be stable at a level above 200 spawners. They believed that stocks in this category had reached the threshold for classification as threatened under the ESA. They classified a stock as of special concern if a relatively minor disturbance could threaten it, if insufficient data were available for it, or if it were influenced by large releases of hatchery fish or possessed some unique character. For steelhead, they classified 98 stocks as follows: 23 extinct, 1 possibly extinct, 27 high risk, 17 moderate risk, and 30 special concern (Table 9).


Table 9. Steelhead stocks identified by Nehlsen et al. (1991) as at some risk of extinction.

ESUa

Extinctb
Possibly
extinct
High
risk
Moderate
risk
Special
concern
1-Puget Sound
none none winter steelhead winter steelhead winter steelhead
Dewatto R. Lake Washington
Tahuya R.
Nooksack R.
Skokomish R.
Samish R.
summer steelhead summer steelhead
Tolt R.
Deer Cr.
S.F. Nooksack R.
2-Olympic Peninsula
none none none none none
3-Southwest Washington
none none none winter steelhead winter steelhead
small Columbia
R. tributaries
Grays R.
Elochoman R.
4-Lower Columbia River
summer steelhead summer steelhead winter steelhead winter steelhead winter steelhead
Sandy R. White Salmon R. White Salmon R.
Wind R.
Hood R.
Cowlitz R.
Washougal R.
Clackamas R.
small tributaries
Coweeman R.
Toutle R.
Kalama R.
Lewis R.
summer steelhead summer steelhead summer steelhead
Cowlitz R.
N.F. Lewis R.
Washougal R.
Hood R. Wind R. E.F. Lewis R.
5-Upper Willamette River
none none none none winter steelhead
Calapooia R.
6-Oregon Coast
summer steelhead none none summer steelhead winter steelhead
S. Umpqua R. Siletz R. Tillamook R.
Nestucca R.
Salmon R.
Siletz R.
Yaquina R.
Alsea R.
Yachats R.
Tenmile Cr.
Big Cr.
Siuslaw R.
7-Klamath Mountains Province
none none summer steelhead winter steelhead none
Smith R. Illinois R.
summer steelhead
Rogue R.
Klamath R.
8-Northern California
none none summer steelhead summer steelhead none
Redwood Cr.
Mad R.
Eel R.
9-Central California Coast
none none winter steelhead none none
Napa R.
San Francisco Bay
tributaries
10-South-Central California Coast
none none winter steelhead winter steelhead winter steelhead
Pajaro R.
Carmel R.
Salinas R. Big Sur R.
Little Sur R.
11-Southern California
winter steelhead none winter steelhead none none
Gaviota Cr.
Rincon Cr.
Los Angeles R.
San Gabriel R.
Santa Ana R.
San Diego R.
San Luis Rey R.
San Mateo Cr.
Santa Margarita R.
Sweetwater R.
Maria Ygnacio R.
Santa Ynez R.
Santa Clara R.
Ventura R.
Malibu Cr.
12-Central Valley
none none winter steelhead none none
Sacramento R.
13-Middle Columbia River
none none winter steelhead winter steelhead summer steelhead
Klickitat R.
small tributaries
Fifteenmile Cr. Klickitat R.
Walla Walla R.
summer steelhead
small tributaries
14-Upper Columbia River
summer steelhead none summer steelhead none summer steelhead
Spokane R.
Pend Oreille R.
Entiat R.
Methow R.
Okanogan R.
Wenatchee R.
15-Snake River Basin
summer steelhead none none summer steelhead summer steelhead
Powder R.
Burnt R.
Weiser R.
Payette R.
Malheur R.
Boise R.
Owyhee R.
Bruneau R.
Asotin Cr. Tucannon R.
Salmon R.
Clearwater R.
Imnaha R.
aESU = evolutionarily significant unit.
bDue to lack of information on steelhead stocks that are presumed to be extinct, the relationship of these stocks, and the relationship of any residualized, resident forms, to adjacent steelhead ESUs is uncertain. They are listed here based on geography and to give a complete presentation of the stocks identified by Nehlsen et al. (1991).
Higgins et al. (1992) used the same classification scheme as Nehlsen et al. (1991) but provided a more detailed review of some northern California salmonid stocks. In this review, their evaluation is relevant only to the northern California ESU.

Nickelson et al. (1992) rated coastal Oregon (excluding Columbia River Basin) salmon and steelhead stocks on the basis of their status over the past 20 years. They used the following classifications: depressed (spawning habitat underseeded, declining trends, or recent escapements below long-term average), healthy (spawning habitat fully seeded and stable or increasing trends), or of special concern (300 or fewer spawners or a problem with hatchery interbreeding). They classified 27 steelhead populations in coastal Oregon as follows: 21 depressed, 1 special concern, and 5 healthy.

WDF et al. (1993) categorized all salmon and steelhead stocks in Washington on the basis of stock origin (native, non-native, mixed, or unknown), production type (wild, composite, or unknown) and status (healthy, depressed, critical, or unknown). Status categories were defined as follows: healthy, "experiencing production levels consistent with its available habitat and within the natural variations in survival for the stock;" depressed, "production is below expected levels ... but above the level where permanent damage to the stock is likely;" and critical, "experiencing production levels that are so low that permanent damage to the stock is likely or has already occurred." Of the 141 steelhead stocks identified, 36 were classified as healthy, 1 as critical, 44 as depressed, and 60 as unknown. Most of those classified as unknown are small stocks without large fisheries.

USFS (1993a,b) provided verbal descriptions of the status of steelhead stocks on Forest Service lands and noted their agreement or disagreement with status designations in other reviews. In Appendix E, we have grouped their comments into status categories based on key phrases used in their descriptions: stable or healthy (S); unknown (U); depressed, declining, low, or moderate risk of extinction (D); critical, high risk of extinction, or severely depressed (C); extinct (X); and not present (N).

Titus et al. (in press) provided a detailed review of steelhead populations south of San Francisco Bay, classifying them by categories based on presence or absence of the species and general trends in abundance. They used special symbols to categorize population status, as follows: steelhead present, no discernable change from historical levels (X); production reduced from historical levels, or likely so (<); current presence or absence unknown (?); extinct (E).

We encountered several problems in applying results of these studies to ESA evaluations, with a major problem being that the definition of "stock" or "population" varied considerably in scale among studies, and sometimes among regions within a study. Identified units range in size from large river basins (e.g., "Sacramento River" in Nehlsen et al. 1991), to minor coastal streams and tributaries (Titus et al. in press).

A second problem was the definition of categories used to classify stock status. Only Nehlsen et al. (1991) and Higgins et al. (1992) used categories intended to relate to ESA "threatened" or "endangered" status, and they applied their own interpretations of these terms to individual stocks, not to ESUs as defined here. Nickelson et al. (1992) and WDF et al. (1993) used general terms describing the status of stocks that could not be directly related to the considerations important in ESA evaluations. For example, the WDF et al. (1993) definition of healthy could conceivably include a stock at substantial extinction risk due to loss of habitat, hatchery fish interactions, or environmental variation (although this does not appear to be the case for any steelhead stocks).

A third problem is the selection of stocks or populations to include in the review. Nehlsen et al. (1991) and Higgins et al. (1992) did not evaluate (or even identify) stocks not perceived to be at risk, so it is difficult to determine the proportion of stocks they considered to be at risk in any given area. For steelhead, WDF et al. (1993) included only stocks considered to be substantially wild and included data only for the wild component for streams that have both hatchery and natural fish escaping to spawn (Johnson) , giving an incomplete evaluation of steelhead utilizing natural habitat.

Data Evaluations

Quantitative evaluations of data included comparisons of current and historical abundance of steelhead and calculation of recent trends in escapement and the proportion of natural spawning attributable to hatchery fish. Historical abundance information for these ESUs is largely anecdotal. Time series data are available for many populations, but data extent and quality varied among ESUs. We compiled and analyzed this information to provide several summary statistics of natural spawning abundance, including (where available) recent total spawning run size and escapement, percent annual change in total escapement, recent naturally produced spawning run size and escapement, and average percentage of natural spawners that were of hatchery origin.

Although this evaluation used the best data available, it should be recognized that there are a number of limitations to these data, and not all summary statistics were available for all populations. For example, spawner abundance was generally not measured directly; rather, it often had to be estimated from catch (which itself may not always have been measured accurately) or from limited survey data. In many cases, there were also limited data to separate hatchery production from natural production.

Data types--Quantitative assessments were based on historical and recent run-size estimates and time series of freshwater spawner and juvenile survey data, harvest rate estimates, and counts of adults migrating past dams. We considered this information separately for each ESU. Because of the disparity of data sources and quality for the different ESUs, data sources and analyses are described separately for each ESU. Information on stock abundance was compiled from a variety of state, federal, and tribal agency records. We believe these records to be complete in terms of existing long-term adult abundance information for steelhead in the region covered. Principal data sources were angler catch estimates, dam or weir counts, and stream surveys. None of these sources provided a complete measure of adult spawner abundance for any of the streams; specific problems are discussed below for each data type.

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. There are a variety of problems in interpreting abundance trends from sport harvest data; these are discussed in detail in the Oregon Coast ESU section below.

Counts of adult steelhead at dams and weirs are available from several river basins along the coast. These counts are probably the most accurate estimates available of total spawning run abundance, but often represent only small portions of the total population in each river basin. As with angler catches, these counts typically represent a combination of hatchery produced and natural fish, and thus are not a direct index of natural population trends.

Stream surveys for steelhead spawning abundance have been conducted by various agencies within most of the ESUs considered here. The methods and time spans of the surveys vary considerably among regions, so it is difficult to assess their general reliability as population indices. However, for most streams where these surveys were conducted, they are the best local indication we have of population trends.

Computed statistics--To represent current run size or escapement where recent data were available, we computed the geometric mean of the most recent 5 years reported (or fewer years if data series is shorter than 5 years). We tried to use only estimates that reflect the total abundance for an entire river basin or tributary, avoiding index counts or dam counts that represent only a small portion of available habitat. For Oregon angler catch data for coastal streams, catch was expanded to total run size and escapement (run size minus catch) using the methods and harvest rate estimates of Kenaston (1989). For the inland streams, we had no estimates of harvest rate to do this expansion. To avoid some local bias problems in areas with few anglers, catch data were used only for streams with an average catch greater than 100 steelhead per year. Where time-series data were not available, we relied on recent estimates from state agency reports; time periods included in such estimates varied considerably.

Where adequate data were available, trends in total escapement (or run size if escapement data were not available) were calculated for all data sets with more than 5 years of data, based on total escapement or an escapement index (such as fish per mile from a stream survey). As an indication of overall steelhead population trends in individual streams, we calculated average (over the available data series) percent annual change in adult spawner indices within each river basin. Trends were calculated as the slope (a) of the regression of ln(abundance) against years, corresponding to the biological model N(t) = b eat, where b is abundance at time t=0. Slopes significantly different from zero (P<0.05) were noted. The regressions provided direct estimates of mean instantaneous rates of population change (a); these values were subsequently converted to percent annual change, calculated as 100 (ea - 1). No attempt was made to account for the influence of hatchery produced fish on these estimates, so the estimated trends include any supplementation effect of hatchery fish.

Percentages of hatchery fish in spawning escapements were computed from 5-year geometric means of hatchery and natural escapement data where estimates of both were available. In most cases, however, we had to rely on recent estimates from state agencies. The time span and methods used in such estimates were often not reported, so the reliability of many of these estimates is unknown. For many Washington winter steelhead populations, we were able to calculate this percentage from WDFW steelhead inventory tables (WDFW 1994b) which provided estimates of both natural (late-run) and hatchery (early-run) spawner abundance. In Oregon, the main source for hatchery percentage estimates was the ODFW 1992 Wild Fish Management Policy report (Chilcote et al. 1992). Many of the estimates in that report were based on scale analysis of fish sampled from angler catches, and thus probably overestimate the proportion of hatchery fish actually spawning because the sport fishery selects for a higher proportion of hatchery fish in many areas. ODFW (1995a,b) has provided improved estimates for several stocks, which we used where available.

Run timing--An issue that may play a significant role in determining the nature and extent of interactions between hatchery and wild steelhead is separation of run timing. It is common for hatchery stocks of steelhead to return and spawn several weeks or months earlier than the natural populations they were derived from. This can occur either through selection for early returning adults in broodstock collection, or through faster growth and higher survival in the hatchery of progeny from early spawning fish. Earlier spawning for hatchery steelhead has at least two advantages from a fishery management perspective. First, the longer growth period makes it easier to produce hatchery fish that smolt in 1 year. Second, separation of spawn timing for natural and hatchery fish provides an opportunity to maximize harvest of hatchery fish while minimizing impacts on natural populations. Because winter steelhead generally spawn later than summer steelhead, winter steelhead provide the greatest opportunity for advancement of run and spawn timing in the hatchery.

State agencies in Washington and Oregon have adopted somewhat different approaches to the issue of run timing in hatchery steelhead. The Washington Department of Fisheries and Wildlife has intentionally developed early spawning hatchery stocks of winter steelhead for planting into coastal and lower Columbia River drainages. The early run timing is meant to accomplish two major objectives: provide an opportunity for high harvest rates on early returning hatchery fish without undue risk to wild fish, and minimize opportunities for interbreeding between naturally spawning hatchery fish and wild fish.

In contrast, the Oregon Department of Fish and Wildlife has not vigorously promoted altered run timing in their hatchery steelhead stocks. Although steelhead from Oregon coastal hatcheries commonly return and spawn somewhat earlier than their natural counterparts, the timing difference is not generally as great as in Washington. It should be noted, however, that WDFW generally uses only a few regional donor stocks (Chambers Creek and Skamania throughout Western Washington; Elochoman, Cowlitz and Skamania in the Lower Columbia River; Wells in the Upper Columbia River), so that stock transfers from a few regional hatcheries provide advanced-run stock to a multitude of rivers. On the other hand, ODFW, although relying on some regional donor stocks, also maintains many individual hatchery populations that are indigenous to the river into which they are planted (e.g., North Umpqua, Chetco, Deschutes, Clackamas Rivers). Therefore, advanced-run fish have not been distributed throughout the Oregon state hatchery system as extensively as have those in Washington.

In reviewing the status of individual ESUs of west coast steelhead, we considered the risks posed by artificial propagation to be important, particularly in combination with other risk factors indicating declines in abundance. Information submitted to the ESA Administrative Record for West Coast Steelhead indicates that, in general, the current WDFW policy to encourage run and spawn time separation between hatchery and natural winter steelhead and to maintain very high (80-90%) harvest rates on hatchery steelhead has resulted in less overlap on the natural spawning grounds than is the case for winter steelhead in Oregon. This factor was a consideration in the BRT's conclusions that some of the ESUs for coastal steelhead in Washington state are not at risk of extinction or endangerment (see below). However, BRT conclusions on this issue should be regarded as preliminary because information about the degree of interactions that actually occur between hatchery and natural fish is still incomplete.

Furthermore, although the WDFW strategy may be effective in reducing opportunities for direct interactions between hatchery and natural steelhead adults, those genetic and ecological interactions that do occur may be more deleterious to the natural population. A considerable body of evidence indicates that run and spawn timing in salmonids can have a strong genetic component, and it is not likely that substantially altered spawn timing would be advantageous to the natural population in the long term. In the short term, juvenile progeny of early spawning hatchery fish that do survive will be larger and may outcompete their natural counterparts. In addition, high harvest rates focused on hatchery fish may eliminate early natural spawners, resulting in a selective shift in natural run timing.


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