180 ASSESSMENT OF EXTINCTION RISK Background The U. S. Endangered Species Act ( ESA) ( Section 3) defines the term " endangered species" as " any species which is in danger of extinction throughout all or a significant portion of its range." The term " threatened species" is defined as " any species which is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range." NMFS considers a variety of information in evaluating the level of risk faced by an ESU. Important considerations include 1) absolute numbers of fish and their spatial and temporal distribution; 2) current abundance in relation to historical abundance and carrying capacity of the habitat; 3) trends in abundance, based on indices such as dam or redd counts or on estimates of spawner recruit ratios; 4) natural and human influenced factors that cause variability in survival and abundance; 5) possible threats to genetic integrity ( e. g., selective fisheries and interactions between hatchery and natural fish); and 6) recent events ( e. g., a drought or a change in management) that have predictable short term consequences for abundance of the ESU. Additional risk factors, such as disease prevalence or changes in life history traits, may also be considered in evaluating risk to populations.

According to the ESA, the determination of whether a species is threatened or endangered should be made on the basis of the best scientific information available regarding its current status, after taking into consideration conservation measures that are proposed or are in place. In this review, we did not evaluate likely or possible effects of conservation measures. Therefore, we do not make recommendations as to whether identified ESUs should be listed as threatened or endangered species, because that determination requires evaluation of factors not considered by us. Rather, we have drawn scientific conclusions about the risk of extinction faced by identified ESUs under the assumption that present conditions will continue ( recognizing, of course, that natural demographic and environmental variability is an inherent feature of " present conditions"). Conservation measures will be taken into account by the NMFS Northwest and Southwest Regional Offices in making listing recommendations. Also, as noted in the " Introduction" above, this review does not attempt to fully evaluate causal factors leading to the present status of chinook salmon, nor to rank the importance of such factors. In this report, such factors are considered only to the extent that they contribute to an evaluation of risk presently facing these stocks. A separate document identifies factors for decline of chinook salmon from Washington, Oregon, California, and Idaho, and is prepared subsequent to any proposed listing recommendation.

Aspects of several of these risk considerations are common to all chinook salmon ESUs. These are discussed in general below; more specific discussion of factors for each of the 15 ESUs under consideration here can be found in the following sections. Status reviews have previously 181 been conducted for some of the ESUs identified. Reevaluation of the risk faced by these ESUs was limited.

Absolute Numbers The absolute number of individuals in a population is important in assessing two aspects of extinction risk. 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). 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 broodyear 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 and/ 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 focus here on measures of the number of adults escaping to spawn in natural habitat. However, total run size ( spawning escapement + harvest) is also of interest 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 a supplemental indicator 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 are based on data that indicate total numbers or density of adults that spawn in natural habitat (" naturally spawning fish"). The total of all naturally spawning fish (" total escapement") is divided into two components ( Fig. 28): " hatchery produced" fish are reared as juveniles in a hatchery but return as adults to spawn naturally; and " natural" fish are progeny of naturally spawning fish. This approach does not distinguish natural fish of hatchery heritage from those of strictly native, natural origin. Although, such a distinction would be useful, in our experience there is rarely information available on which to make such a distinction. To the extent that stocking records and/ or hatchery practices shed light on this distinction, that information is taken into account in considering genetic integrity of the population ( discussed below). 182 Figure 28. Schematic diagram of mixing of naturally ( N) and hatchery ( H) produced fish in natural habitat. Ovals represent the total spawning in natural habitat each generation. This total is composed of naturally produced and hatchery produced offspring of individuals in the previous generation. 183 Historical Abundance and Carrying Capacity Knowing the relationship of present abundance to present carrying capacity is important for evaluating the health of populations; but the fact that a population is near its current capacity does not necessarily signify full health. A population near capacity implies that short term management may not be able to increase fish abundance. This also implies that competition and other interactions between hatchery and natural fish may be an important consideration for increasing the abundance of naturally spawning populations, because releases of hatchery fish may further increase population density in a limited habitat.

The relationship of current abundance and habitat capacity to historical levels is an important consideration in evaluating risk. Knowledge of historical population conditions provides a perspective for understanding the conditions under which present populations evolved. Historical abundance also provides the basis for scaling long term trends in populations. Comparison of present and past habitat capacity can also indicate long term population trends and problems of population fragmentation.

In this review, application of these principles was limited by lack of reliable estimates of historic abundance and historic or current capacity for most chinook salmon populations.

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. Regular sampling, of one kind or another, has been conducted on chinook salmon populations in the larger basins within the reviewed area. These data sources and methods are discussed in more detail below, under " Approach." Interpretation of trends in terms of population sustainability is difficult for a variety of reasons: First, chinook salmon are harvested in heavily managed fisheries, and shifting harvest goals directly affect trends in spawning escapement. Second, environmental fluctuations on short timescales affect trend estimates, especially for shorter trends; this is a particular problem in this review because numerous abundance data series began in the mid 1980s, a period of relatively high chinook salmon abundance throughout much of the West Coast. Third, artificial propagation has a strong influence on trends of many chinook salmon populations.

Naturally spawning hatchery fish Waples ( 1991a, b) and Hard et al. ( 1992) discussed the role of artificial propagation in ESU determination and emphasized the need to focus on natural production in the threatened or endangered status determination. Because of the ESA's emphasis on ecosystem conservation, this analysis focuses on naturally reproducing fish. An important question in evaluating risk is 184 thus: Is natural production sufficient to maintain the population without the constant 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 the natural population. One method of approaching this issue involves calculating 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. Data for chinook salmon are rarely sufficient for this calculation, and we have not attempted 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. 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 in this review.

Habitat A major determinant of trends in salmon abundance is the condition of the freshwater, estuarine, and ocean habitats on which salmon depend. While we rarely have sufficient information to predict the population scale effects of habitat loss or degradation with any precision, it is clear that habitat availability imposes an upper limit on the production of salmon, and any reduction in habitat reduces potential production. Even in areas where we have no information on trends in population abundance, evidence of widespread loss of habitat can indicate a serious risk for sustainability of natural populations. The National Research Council Committee on Protection and Management of Pacific Northwest Anadromous Salmonids ( NRCC 1996) identified habitat problems as a primary cause of declines in wild salmon runs. NMFS ( 1996b) identified habitat concerns as one of a suite of factors affecting the decline of salmon occurring within the range of West Coast steelhead. Some of the habitat impacts identified were the fragmentation and loss of available spawning and rearing habitat, alteration of streamflows and streambank and channel morphology, migration delays, degradation of water quality, alteration of ambient stream water temperatures, sedimentation, loss of spawning gravel, pool habitat and large woody debris, removal of riparian vegetation, and decline of habitat complexity ( CACSST 1988, FEMAT 1993, NMFS 1996b). The Pacific Fishery Management Council ( PFMC 1995) also identified loss of habitat as one of the main reasons for declines in salmon stocks, and identified fourteen " vital habitat concerns": California's Central Valley Water Project, San Francisco Bay and Sacramento San Joaquin River water quality standards, Columbia Snake River hydropower operations, instream flow, unscreened or inadequately screened water diversions, inadequate fish passage at road culverts, water spreading ( unauthorized use of federally developed water supplies), upland land use practices and polluted runoff, fish passage at existing hydroelectric projects, agricultural practices, urban growth and land conversion, contaminants in coastal wetlands and estuaries, offshore oil and gas development and transportation, and dredge spoil disposal. Several regional reports summarize many of the problems related to habitat for chinook salmon ( for example, Bottom et al. 1985, Reynolds et al. 1993, Bishop and Morgan 1996). There are numerous other studies of habitat 185 problems in local areas, many of which are cited in the " Analysis of Biological Information" below. However, a full evaluation of the extent to which habitat conditions or other factors contribute to the status of chinook salmon stocks, and identification which factors that are most important contributors to risk, is beyond the scope of this review.

Assessing the effects of habitat changes on future sustainability of populations is difficult. Human populations are projected to continue increasing in most areas of the West Coast, and water impoundments and diversions, as well as logging and agricultural activities, can be expected to continue into the future ( Gregory and Bisson 1997). These facts indicate that there will be some continuing losses of salmon habitat for the foreseeable future. By contrast, recent changes in forest and agricultural practices and improved urban planning have reduced the rate of habitat loss in many areas, and many areas are recovering from severe past degradation. Whether natural recovery and active restoration in some areas will compensate for continued losses in other areas is unknown.

Regional perspective Recent trends in coastwide chinook salmon abundance provide a larger perspective for this review. From the early part of the century through the 1980s, coastwide commercial landings of chinook salmon have declined by roughly half, but this may reflect changes in fisheries as much as declines in abundance. In the early part of the century, nearly all commercial fisheries in this region operated in freshwater, where they harvested only mature salmon. Most recent commercial harvest of chinook salmon in the region considered in this review occurs in saltwater troll fisheries, where immature fish are harvested at smaller sizes than mature fish. Over the same period, the fraction of the total harvest taken by recreational fisheries has grown. By all accounts, however, there has been significant replacement of natural production with hatchery fish. Over a large region ( British Columbia, Washington, Oregon, California, and Idaho), chinook salmon stocks ( both natural and hatchery) have exhibited recent decreases in survival which may be due at least in part to changes in climate and ocean productivity.

Factors Causing Variability Variation in production and/ or survival is, along with trend and abundance, a primary determinant of demographic extinction risk. Salmon abundance tends to be highly variable, with interannual fluctuations in the range of 40 70% ( Bisson et al. 1997). Variability 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). Recent changes in ocean condition are discussed below. Because salmon have evolved and are adapted to variable systems ( Bisson et al. 1997), variation in itself is not an indicator of risk to healthy populations. Habitat degradation and harvest have probably made stocks less resilient to poor climate conditions, but these effects are not easily quantifiable. 186 Threats to Genetic Integrity Artificial propagation poses a number of genetic risks for natural salmon and steelhead populations in addition to the complications it brings to evaluation of natural replacement rates. These risks have been known for some time ( e. g., Hynes et al. 1981, Allendorf and Ryman 1987, Hindar et al. 1991, Waples 1991a), but no consensus has emerged on how best to incorporate these concerns into adaptive management because of difficulties in quantifying the risks, a paucity of empirical data, and disagreements about how to proceed given these uncertainties ( Cuenco et al. 1993, Campton 1995, Hard 1995, Currens and Busack 1995). In this section we describe some of the adverse genetic effects for natural populations that can occur as a result of artificial propagation and briefly discuss the factors that were used in this status review to evaluate these risks. This is an important component to the overall risk analysis because these effects generally would not be reflected in other indices of population health ( e. g., abundance and trends). For example, interbreeding with hatchery fish might reduce fitness and productivity of a natural population, but whether this had occurred would be difficult to determine if hatchery fish continued to spawn naturally.

Busack and Currens ( 1995) and Campton ( 1995) identified several types of genetic risk from hatcheries and alternative ways of describing such risks. Interbreeding of hatchery and natural fish can lead to loss of fitness in local populations. Grant ( 1997) reviews and discusses genetic concerns regarding straying by non native hatchery fish. Ricker ( 1972) and Taylor ( 1991) summarized some of the evidence for local adaptations in Pacific salmonids that may be at risk from interbreeding of hatchery and natural fish. Hatchery wild interbreeding can also lead to loss of genetic diversity among populations. Interpopulational genetic diversity can help maintain long term viability of an ESU because it buffers overall productivity against periodic or unpredictable changes in the environment ( Fagen and Smoker 1989, Riggs 1990).

Various fish culture and management practices can affect the frequency and magnitude of hatchery wild genetic interactions. For example, stock transfers or other aspects of hatchery programs that lead to substantial straying into natural populations can result in much higher rates of genetic exchange than would naturally occur among populations. Because the consequences of hatchery straying are determined by the proportion of natural spawners of hatchery origin rather than by the proportion of hatchery fish that stray ( Grant 1997), the effects of a successful hatchery program can be substantial even if stray rates are modest. Management actions such as avoiding stock transfers, adopting release strategies that minimize straying, and marking and selectively harvesting hatchery fish can substantially reduce adverse effects on natural populations. The degree to which such actions succeed in isolating natural and hatchery production varies considerably from program to program and depends on a variety of factors.

Similarly, a number of approaches can be used in fish culture to minimize genetic changes and hence reduce the consequences of hatchery wild genetic interactions when they do occur. For example, inbreeding and genetic drift are well understood at the theoretical level, and researchers have found inbreeding depression in various fish species, including some salmonids 187 ( Allendorf and Ryman 1987). There is also good reason to believe that inbreeding can be an important concern for Pacific salmon hatcheries ( Waples and Teel 1990, Ryman and Laikre 1991, Waples and Do 1994). However, we are not aware of empirical evidence for inbreeding depression or substantial loss of genetic variability in any natural or hatchery populations of Pacific salmon or steelhead ( Hard and Hershberger 1995). Furthermore, some fairly straightforward fish culture practices ( especially suitable broodstock collection and mating protocols) can significantly reduce the likelihood that hatchery populations will increase levels of inbreeding ( Simon et al. 1986, Allendorf and Ryman 1987, Withler 1988, Waples and Do 1994). In contrast, selective changes arising from fish culture cannot be avoided even with the best fish culture practices. Because the selective regime in the hatchery environment differs in many important ways from that in the wild, and because a successful salmon hatchery profoundly changes the mortality profile of the population, some genetic divergence of a cultured population from a natural population is inevitable ( Waples 1991a, Busack and Currens 1995, Campton 1995). The changes that do occur as a result of fish culture are unlikely to be beneficial to locally adapted natural populations.

In supplementation programs, which involve the intentional integration of hatchery and natural production, genetic risks posed by fish culture must be weighed against potential benefits to the natural population such as reducing short term extinction risk and speeding recovery. Conducting a comprehensive risk/ benefit analysis for salmon supplementation should be an integral part of adaptive management. We did not attempt such an exercise here because the focus of this report is on evaluating the status of natural populations rather than the merits of hatchery programs. Although a successful supplementation program might help move a natural population toward recovery, the existence of a hatchery program designed to assist recovery can be taken as an indication that the natural population is presently at some risk in its natural habitat, and that is an important consideration in the status review.

Finally, 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 and/ or mates and, if they are successful in spawning with natural fish, may divert production from more productive natural X natural crosses ( Chapman et al. 1995). The presence of large numbers of hatchery juveniles or adults may also alter the selective regime faced by natural fish.

To evaluate genetic risks posed by artificial propagation, we consider a variety of factors related to the nature, scale, and duration of the hatchery programs that may interact with natural populations. These factors include the source of hatchery broodstock, the number of hatchery fish released, the number of years hatchery fish have been released into the system, differences in genetic and life history characteristics ( e. g., age structure and body size) between hatchery and natural fish, and the effectiveness of management strategies to isolate hatchery and natural fish. In cases where it is available, information on the numbers and proportions of hatchery and natural fish spawning naturally and their relative reproductive success is also considered. Studies that 188 monitor genetic characteristics over time can also provide valuable insight into the consequences of hatchery wild interactions.

Human actions other than artificial propagation can also affect the genetic characteristics and integrity of salmon populations. These factors include size selective harvest regimes ( Nelson and Soulé 1987, Thorpe 1993), introduction of non native species, alterations of freshwater migration corridors by hydropower development, and other types of habitat modification. Unfortunately, empirical information for these types of genetic changes is even more sparse than it is for the effects of artificial propagation.

Recent Events A variety of factors, both natural and human induced, affect the degree of risk facing salmonid populations. Because of timelags in these effects and variability in 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, but 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 do we evaluate the risk that a population may not persist?

Climate conditions are known to have changed recently in the Pacific Northwest. Most Pacific salmonid stocks south of British Columbia have been affected by changes in ocean production that occurred during the 1970s. Pearcy ( 1992) and Lawson ( 1993) attribute this decline largely to ocean factors, but do not identify specific effects. Much of the Pacific Coast has also experienced drought conditions in recent years, which may depress freshwater production. At this time, we do not know whether these climate conditions represent a long term shift in conditions that will continue affecting stocks into the future or short term environmental fluctuations that can be expected to be reversed in the near future. Although recent conditions appear to be within the range of historic conditions under which local salmon populations have evolved, the risks associated with poor climate conditions may be exacerbated by human influence on these populations ( Lawson 1993).

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. Such factors may be important for individual populations, as noted in the ESU summaries below. 189 Approach None of the elements of risk outlined above are easy to evaluate, particularly in light of the great variety in quantity and quality of information available for various populations. Two major types of information were considered: previous assessments that provided integrated reviews of the status of chinook salmon populations in our region, and data regarding individual elements of population status, such as abundance, trend, hatchery influence, and habitat conditions.

A major problem in evaluations of risk for salmon is combining information on a variety of risk factors into a single overall assessment of risk facing a population. Formal model based population viability analysis ( PVA) attempts to do this integration in a quantitative manner, resulting in a single estimate of extinction risk. Current models of salmon populations are inadequate for this type of analysis. In the absence of integrative models, it is still possible to define criteria for some individual risk categories, and use these criteria to devise simple rules for categorizing risk levels; Allendorf et al. ( 1997) advocated such an approach. However, this limits assessment to those factors for which adequate measurements are available for all population units under consideration. As our ability to measure some of the important risk and other factors is limited, data is often lacking for the populations most at risk. Our researchers need methods that allow inclusion of both quantitative and qualitative information. In this review, we have used a risk matrix approach through which the BRT members applied their best scientific judgement to combine qualitative and quantitative evidence regarding multiple risks into an overall assessment. The matrix is more fully described in Appendix F.

It is also possible to construct simple demographic models to evaluate risks associated with population abundance, trend, and variability ( e. g., Goodman in press). Such models can provide a partial quantification of risks if adequate data are available. We have not attempted to construct such models for this review but have considered results from such efforts where available ( e. g., Emlen 1995, Ratner et al. 1997).

Previous Assessments In considering the status of the 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 chinook salmon stocks ( Nehlsen et al. 1991, Higgins et al. 1992, Nickelson et al. 1992, WDF et al. 1993, Huntington et al. 1996). These evaluations are summarized in Appendix E. Additional information presented by the petitioners ( ONRC and Nawa 1995) was considered, as discussed under " Summary of Information Presented by the Petitioners" above. 190 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 do not appear in their summary were either not at risk of extinction or the researchers lacked sufficient information to classify them. Nehlsen et al. ( 1991) 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). Nehlsen et al. ( 1991) 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 had recent spawning escapements less than 200. Stocks were classified as at moderate risk of extinction if they had declined from historic levels but presently appear to be stable at a level above 200 spawners. They felt that stocks in this category had reached the threshold for threatened under the ESA. They classified stocks as of special concern if a relatively minor disturbance could threaten them, insufficient data were available for them, they were influenced by large releases of hatchery fish, or they possessed some unique character. For chinook salmon, they classified 112 stocks as follows: 49 extinct, 10 possibly extinct, 27 high risk, 14 moderate risk, and 12 special concern ( Appendix E).

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 Southern Oregon and California Coastal and Upper Klamath and Trinity Rivers ESUs. They classified 15 chinook salmon populations in these two ESUs as follows: 6 high risk, 1 moderate risk, and 8 as stocks of special concern ( Appendix E).

Nickelson et al. ( 1992) rated wild coastal ( excluding Columbia River Basin) Oregon salmon and steelhead stocks on the basis of their status over the past 20 years, classifying stocks as " healthy" ( spawning habitat fully seeded and stable or increasing trends), " depressed" ( spawning habitat underseeded, declining trends, or recent escapements below long term average), " of special concern" ( 300 or fewer spawners or a problem with hatchery interbreeding), or " unknown" ( insufficient data). The following additional comments were noted for salmonid populations when relevant: " 1" ( may not be a viable population), " 2" ( hatchery strays), and " 3" ( small, variable run). They classified 55 chinook salmon populations in coastal Oregon as follows: 30 healthy ( 2 with small, variable runs), 8 depressed, 8 special concern due to hatchery strays, and 9 unknown ( 4 of which they suggested may not be viable) ( Appendix E).

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 106 chinook salmon stocks identified, 54 were 191 classified as healthy, 5 as critical, 35 as depressed, and 12 as unknown ( Appendix E). Most of those classified as unknown are small stocks without large fisheries.

Huntington et al. ( 1996) surveyed the condition of healthy native/ wild stocks of anadromous salmonids in the Pacific Northwest and California. Stocks were classified as healthy based upon abundance, self sustainability, and not having been previously identified as facing a substantial risk of extinction. Healthy stocks were separated into two levels: Level I ("... adult abundance at least two thirds as great as would be found in the absence of human impacts") and Level II ("... adult abundance between one third and two thirds as great as expected without human impacts"). Of the 35 healthy chinook salmon stocks identified, 9 were classified as Level I and 26 as Level II ( Appendix E).

There are problems in applying results of these studies to ESA evaluations. A major problem is 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, complex river basins ( e. g., " Sacramento River" in Nehlsen et al. 1991), to minor coastal streams and tributaries. A second problem is 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. WDF et al. ( 1993) used general terms describing status of stocks that cannot 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 that is at substantial extinction risk due to loss of habitat, hatchery fish interactions, and/ or environmental variation, although this does not appear to be the case for any Washington chinook salmon 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 discuss 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 chinook salmon, 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, giving an incomplete evaluation of chinook salmon utilizing natural habitat.

Data Evaluations Quantitative evaluations of data included comparisons of current and historical abundance of chinook salmon, calculation of recent trends in escapement, and evaluation of 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 escapement, percent annual change in total escapement ( both long term and the most recent ten years), recent naturally produced spawning escapement, and average percentage of natural spawners that were of hatchery origin. 192 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, data to separate hatchery production from natural production were also limited. Specific limitations of the data are discussed under the individual ESUs as part of the " Analysis of Biological Information" below.

Quantitative methods Information on stock abundance was compiled from a variety of state, federal, and tribal agency records. We believe it to be complete in terms of long term adult abundance records for chinook salmon in the region covered. Principal data sources were angler catch estimates, dam or weir counts, and stream surveys. None of these provides a complete measure of adult spawner abundance for any of the streams. Specific problems are discussed below for each data type.

Data types For chinook salmon, quantitative abundance estimates are available on a limited basis and the quality of these estimates varies considerably. Quantitative assessments were based on historical and recent run size estimates, time series of freshwater spawner survey data, harvest rate estimates, and counts of adults migrating past dams. Juvenile survey data were available in some areas but data coverage was insufficient for quantitative assessment. We considered this information separately for each ESU. Because of the disparity of data sources and quality in the different ESUs, the data sources and analysis are described separately for each ESU; here we present only a brief regional overview of information types considered.

Quantitative estimates of spawning escapement are available for the Sacramento San Joaquin and the Klamath River Basins in California and for most coastal and Puget Sound rivers in Washington. Within the Columbia River Basin, quantitative estimates are available for many lower Columbia River tributaries in Washington and for the Willamette and Deschutes Rivers in Oregon. On the mainstem of the Columbia and Snake Rivers, dam counts provide quantitative estimates of run size, but in most cases, these counts cannot be resolved to the individual population level and are subject to errors stemming from fallback, run classification, and unaccounted mortality. Run reconstructions providing estimates of both adult spawning abundance and fishery recruits are being prepared for many stream type chinook salmon populations in the Columbia River Basin ( Beamsderfer et al. 1997 unpubl. draft report), but were not available in final form for this review.

Sport harvest and peak index spawner survey information were 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 193 abundance trends from sport harvest data; for this reason, angler catch was used only for estimating recent abundance, not for trend analyses.

Dam and weir counts are available in several river basins along the coast. These counts are probably the most reliable estimates available of total spawning run abundance, but often represent only small portions of the total population in each river basin and may be biased by incomplete ( less than 24 hours per day) counting, fallback, and reascension. As with angler catch, 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 chinook salmon 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 the general reliability of these surveys as population indices. For most streams where these surveys are conducted, they are the best local indication we have of population trends.

Information on harvest impacts were compiled from a variety of sources ( see citations for specific ESUs below). In presenting this information, we have tried to maintain a clear distinction between harvest rates ( usually calculated as catch divided by catch plus escapement for a cohort or brood year) and exploitation rates ( age specific rates of exploitation in individual fisheries). Most of the estimates presented here are for harvest rate. We have also classified harvest as " low" ( average harvest rate less than 40%), " moderate" ( rate between 40% and 60%) or " high" ( rate above 60%) as an aid in summarizing information; this classification is not meant to imply an associated degree of risk.

As noted above, we attempted to distinguish natural and hatchery production in our evaluations. Doing this quantitatively would require good estimates of the proportion of natural escapement that was of hatchery origin, and knowledge of the effectiveness of spawning by hatchery fish in natural environments. Unfortunately, this type of information is rarely available, and for most ESUs we have been limited to reporting whatever estimates of escapement of hatchery fish to natural systems that were made available to us.

Computed statistics Recent average abundance is reported as the geometric mean of the most recent five years of data. Where totals are given for an ESU they are the sum of these geometric means. Because the year of the most recent abundance estimate often differs for components of an individual ESU, if abundances were totaled for the ESU and a geometric mean calculated from the total, the most recent years would be incomplete in most cases. We opted instead to calculate sums for components with different time periods. 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 194 methods and harvest rate estimates of Nicholas and Hankin ( 1988). Where time series data were not available, we have relied on recent estimates from state agency reports. Time periods included in such estimates varied considerably.

Historic run size estimates from cannery pack data were made by converting the largest number of cases of cans packed in a single season to numbers of fish in the spawning run ( Big Eagle et al. 1995, based on summary tables in Shepard et al. 1985). The conversion was made by assuming each case of 48 packed ( 454 g) cans represented 80 lb ( 36.3 kg) of salmon landed, the average weight of chinook salmon was 10 kg ( Rich 1940b), and the fishery harvested 50% of the run ( PSC 1994).

Population trends were calculated by least squares linear regression of the natural logarithm of abundance on year, using all data collected after 1950. This assumes that the individual data series is increasing or decreasing exponentially over the entire period of record, and generates an estimate of the rate of increase or decrease as a fraction of abundance per year. We also calculated recent trends from the most recent 10 years, using data collected after 1984 for series having at least 7 observations since 1984. No attempt was made to account for the influence of hatchery produced fish on these estimates, so the estimated trends include any contribution of hatchery fish to escapement.

Analysis of Biological Information Biological information related to risk assessments is presented below. This section is organized by broad geographic regions, with general information for each region summarized before the specific analysis for each ESU within the regions.

Central Valley Region Historically, chinook salmon were abundant in the Central Valley. Early estimates did not differentiate run timing, so the following estimates are assumed to be totals for all runs. Eggs were collected from at least 30,000 adults in the upper Sacramento River in 1905; the total run in the Sacramento River could have been 10 times higher ( ca. 300,000) ( Reynolds et al. 1993). Gillnet catches suggest peak Central Valley chinook salmon in river runs may have been 800,000 to 1,000,000 fish, with average run size about 600,000 fish prior to 1915 ( Reynolds et al. 1993). Total Central Valley chinook salmon spawning escapement was estimated in 1965 to be about 192 421,000 fish ( 332,000 fall & late fall run, 61,000 winter run, and 28,000 spring run) ( CDFG 1995).

Chinook salmon in this region have been strongly affected both by losses and alterations of freshwater and estuarine habitats and by a long history of hatchery production. Reynolds et al. ( 1993) discussed habitat problems extensively. They reported a 95% loss of Central Valley freshwater salmon habitat due to damming, migration blockages, or severe degradation. The most severe losses began in 1849 with the discovery of gold, and culminated in the 1970s with the completion of major water diversion and conveyance facilities. Hydraulic mining caused sedimentation of spawning grounds, water diversions blocked migrations and depleted flows, and explosive human population growth led to major settlement and disturbance ( including logging and agricultural activities) along Central Valley streams and rivers ( CSLC 1993). Construction of levees for flood protection reduced off channel habitat availability. By the 1930s, only 25% of the valley floor was subject to periodic inundation. Dam and water project construction further reduced habitat substantially between the 1930s and 1960s.

Direct relationships exist between water temperature, water flow, and survival of juvenile salmonids. Elevated water temperature in the Sacramento River has limited the survival of young salmon ( Mitchell 1987, DWR 1988). Survival of juvenile salmon in the Sacramento River is also positively correlated with June streamflow and June and July delta outflow ( Dettman et al. 1987).

Since 1872, chinook salmon have been continuously produced at a number of hatchery facilities. Millions of eggs were exported from the region during the 1800s. The majority of fish released prior to 1913 were unfed fry, whose contribution to the run was probably minimal ( Clark 1929). By 1919, some 1.3 billion chinook salmon fry had been released into the Sacramento River Basin ( Cobb 1930). Artificial propagation resources have been devoted primarily to fall run chinook salmon. In the last 50 years, 1.6 billion fall run fish have been released into the Central Valley; this is approximately 40 times more than the number of spring run fish and 600 times more than the number of winter run fish released ( Table 6, Appendix D). The production of springand winter run chinook salmon has been limited by the lack of suitable facilities for holding returning adults during the summer months.

Three hatcheries   Coleman NFH ( 1946), Feather River Hatchery ( 1969), and Nimbus Hatchery ( 1955)   have been responsible for most of the chinook salmon produced in the latter half of this century. Fish from these hatcheries have been released throughout the Sacramento and San Joaquin River Basins and in San Francisco Bay.

1) Sacramento River Winter Run ESU This ESU has been extensively reviewed by NMFS ( 1987, 1989, 1990a, b, 1994b), and that information is briefly summarized and updated here. 193 Historically, the winter run was abundant and comprised populations in the McCloud, Pit, Little Sacramento, and Calaveras Rivers. Construction of Shasta Dam in the 1940s eliminated access to all of the historic spawning habitat for winter run chinook salmon in the Sacramento River Basin. Since then, the ESU has been reduced to a single spawning population confined to the mainstem Sacramento River below Keswick Dam ( Reynolds et al. 1993). The last documented sighting of adult winter run chinook salmon in the Calaveras River was made in 1984 ( CDFG 1984).

Historic abundance has been estimated from anecdotal accounts, habitat capacity, and river gillnet fishery landings, but quantitative estimates of run size are not available for the period prior to the completion of Red Bluff Diversion Dam in 1966. CDFG ( 1965) estimated spawning escapement of Sacramento River winter run chinook salmon at 61,300 ( 60,000 mainstem, 1,000 in Battle Creek, and 300 in Mill Creek) in the early 1960s, but this estimate was based on " comparisons with better studied streams" rather than actual surveys. Fish ladders at Red Bluff Diversion Dam permitted counting of the spawning runs after 1966. During the first 3 years of operation of the counting facility ( 1967 69), the spawning run of winter run chinook salmon averaged 86,500 fish. The most recent 3 year ( 1994 96) average run size wa s 830 fish. Since counting began in 1967, the population has been declining at an average rate of 18% per year, or roughly 50% per generation ( Fig. 29). The trend in the most recent 10 years has been the same as the trend over the entire 27 years of data ( Fig. 30, Appendix E).

The focus of artificial propagation efforts for winter run chinook salmon has been a supplementation and captive broodstock program initiated in 1989. Recently, hatchery efforts may have resulted in the hybridization of spring and winter run chinook salmon 194 Figure 29. Recent 5 year geometric mean spawning escapement for chinook salmon populations in Sacramento River Winter Run ( 1), Central Valley Spring Run ( 2), and Central Valley Fall Run ( 3) ESUs ( see Appendix E for details). 195 Fig ure 30. Trends ( percent annual change) in abundance for chinook salmon populations in 196 Sacramento River Winter Run ( 1), Central Valley Spring Run ( 2), and Central Valley Fall Run ( 3) ESUs ( see Appendix E for details). 197 ( Hedgecock 1995). Furthermore, the fish reared at Coleman NFH ( Battle Creek) were released into the mainstem Sacramento River where the winter run naturally spawns ( USFWS 1996b), but rather than returning to their point of release they returned to Battle Creek where no suitable spawning habitat exists.

Freshwater harvest is negligible, but there is moderately high ocean harvest on this stock. In 1994, the ratio of ocean harvest to ocean harvest plus escapement ( catch /( catch + escapement)) was estimated from CWT recoveries to be 0.54. This estimate was similar to one developed in the early 1970s from a fin clip study. The recent reductions in ocean harvest are intended to insure that winter run chinook salmon have a positive population growth rate, on average.

Historically, contribution of hatchery fish to this population has been negligible. Recently a captive broodstock and smolt supplementation program has been initiated as part of recovery efforts.

The fact that this ESU is comprised of a single population with very limited spawning and rearing habitat increases its risk of extinction due to local catastrophe or poor environmental conditions. There are no other natural populations in the ESU to buffer it from natural fluctuations.

This ESU is currently listed as endangered under the California Endangered Species Act and was listed as threatened in 1989 and reclassified as endangered in 1994 under the US Endangered Species Act ( NMFS 1990a, NMFS 1994b). The only other assessment of risk to stocks in this ESU was that made by Nehlsen et al. ( 1991), who identified one stock ( Calaveras River) as extinct. Due to lack of information on chinook salmon stocks that are presumed to be extinct, the relationship of this stock to the existing Sacramento River winter run is uncertain. It is listed here based on geography and to give a complete presentation of the stocks identified by Nehlsen et al. ( 1991) ( Appendix E).

2) Central Valley Spring Run ESU Historically, spring run chinook salmon were abundant in the Sacramento River system and constituted the dominant run in the San Joaquin River Basin ( Reynolds et al. 1993). Clark ( 1929) estimated that there were historically 6,000 stream miles of salmonid habitat in the Sacramento San Joaquin River Basin, but only 510 miles remained by 1928. Subsequently, elimination of access to spawning and rearing habitat resulting from construction of impassable dams has extirpated spring run chinook salmon from the San Joaquin River Basin and the American River. Construction of impassible dams has also curtailed access to habitat in the upper Sacramento and Feather Rivers.

In 1939, an estimated 5,786 spring run chinook salmon passed the Cottonwood Anderson Dam ( Redding) on the upper Sacramento River ( Hanson et al. 1940). Calkins et al. ( 1940) 198 estimated a spawning escapement of 38,792 fish for the Sacramento River based on fishery landings. In the mid 1960s, CDFG ( 1965) estimated total spawning escapement of spring run chinook salmon to be 28,500, with the majority ( 15,000) spawning in the mainstem Sacramento River and the remainder scattered among Battle, Cottonwood, Antelope, Mill, Deer, Big Chico, and Butte Creeks and the Feather River. CDFG ( 1965) reported spring run chinook salmon to be extinct in the Yuba, American, Mokelumne, Stanislaus, Tuolumne, Merced, and San Joaquin Rivers. Today, spawner survey data are available for the mainstem Sacramento River, Feather River, Butte Creek, Deer Creek and Mill Creek ( Big Eagle & Assoc. and LGL Ltd 1995). Small populations are also reported in Antelope, Battle, Cottonwood, and Big Chico Creeks ( Campbell and Moyle 1990, Reynolds et al. 1993, Yoshiyama et al. 1996).

Spawning escapement has been estimated by a combination of methods, including snorkel surveys, aerial surveys, boat surveys, foot surveys, and fishway counts at Red Bluff Diversion Dam ( Reavis 1985). The California Department of Fish and Game has estimated spawning escapement since the late 1940s or 1950s for the remaining populations except those in the mainstem Sacramento River, which has been counted at Red Bluff Diversion Dam since 1967. The sum of the 5 year geometric mean escapements for this ESU is 6,700 spawners, of which 4,300 ( 64%) have returned to the Feather River ( Fig. 29, Appendix E). The Feather River Hatchery releases several million spring run chinook salmon annually, with the bulk of their production released off site into the Sacramento River Delta. Therefore, the origin of the fish returning to the Feather River is uncertain, and fish from these releases may stray to other parts of the valley. Of the remaining 2,400 spawners, 435 are in the mainstem Sacramento River where their spawning overlaps in both time and space with the more abundant fall run. Sacramento River mainstem spawners have declined sharply since the mid 1980s, from 5,000 15,000 to a few hundred fish. The Feather River population is believed to be hybridized with the fall run in the Sacramento River ( Reynolds et al. 1993), and probably includes many hatchery strays from the Feather River Hatchery program. The remaining three natural populations ( Butte, Deer, and Mill Creeks) are small, and all have long term declining trends in abundance ( Fig. 30, Appendix E).

Efforts to enhance runs of Sacramento River spring run chinook salmon through artificial propagation date back over a century, although programs were not continuously in operation during that period. We found no recent records of introduction of spring run fish from outside the Sacramento San Joaquin River Basin. In the 1940s, trapping of adult chinook salmon that originated from areas above Keswick and Shasta Dams may have resulted in stock mixing, and further mixing with fall run fish apparently occurred with fish transferred to Coleman Hatchery. Deer Creek, one of the locations generally believed most likely to retain essentially native springrun fish, was a target of adult outplants from the 1940s trapping operation, but the success of those transplants is uncertain. Since 1967, artificial production has focused on the program at the Feather River Hatchery ( discussed above). Cramer ( 1996) reported that half of the hatcheryreared spring run fish returning to the Feather River did not return to the hatchery, but spawned naturally in the river. Given the large number of juveniles released off station, the potential contribution of straying adults to rivers throughout the Central Valley is considerable. The termination of CWT marking programs for hatchery derived spring run fish and the absence of 199 spring run carcass surveys for most river systems prevented the accurate estimation of the contribution of naturally spawning hatchery strays. Cramer ( 1996) reported that up to 20% of the Feather River spring run chinook salmon are recovered in the American River sport fishery. Furthermore, the use of a fixed date to distinguish returning spring and fall run fish at the Feather River Hatchery may have resulted in considerable hybridization between the two runs ( Campbell and Moyle 1990).

Harvest rates appear to be moderate. Ocean fishery management focuses on the fall run, with no defined management objectives for spring run fish. Because of the similarity in ocean distribution with fall run fish and smaller average size, spring run harvest rates are probably lower than those for the fall run.

Reynolds et al. ( 1993) reported that spring run fish were likely to have interbred with fallrun fish in the mainstem Sacramento and Feather Rivers, but the extent of hybridization was unknown. They also reported that pure strain spring run fish may still exist in Deer and Mill Creeks.

The only previous assessment of risk to stocks in this ESU is that of Nehlsen et al. ( 1991), who identified several stocks as being at risk or of special concern ( Appendix E). Four stocks were identified as extinct ( spring/ summer run chinook salmon in the American, McCloud, Pit, and San Joaquin [ including tributaries] Rivers) and two stocks ( spring run chinook salmon in the Sacramento and Yuba Rivers) were identified as being at a moderate risk of extinction. Due to lack of information on chinook salmon stocks that are presumed to be extinct, the relationship of these stocks to existing 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).

3) Central Valley Fall Run ESU The historical abundance of Central Valley fall and late fall run chinook salmon is poorly documented. For the San Joaquin River, Reynolds et al. ( 1993) reported recent abundance to be only a remnant of the historical abundance. They estimated that production ( ocean run size) of San Joaquin River fall and late fall run chinook salmon historically approached 300,000 adults and probably averaged approximately 150,000 adults. In the mid 1960s, escapement to the San Joaquin River Basin totaled only about 2,400 fish, spawning in the Stanislaus, Tuolumne, and Merced Rivers.

Calkins et al. ( 1940) estimated abundance at 55,595 fish in the Sacramento River Basin during the period 1931 39. In the early 1960s, adult escapement was estimated to be 327,000, predominantly in the mainstem Sacramento River ( 187,000), but with substantial populations in the Feather ( 50,000), American ( 36,000), and Yuba ( 22,000) Rivers and in Battle Creek ( 21,000); remaining escapement was scattered among numerous tributaries ( CDFG 1965). At that time, 200 total Central Valley fall run chinook salmon escapement ( including the Sacramento, Mokelumne, and San Joaquin River Basins) was estimated at 331,700 adults ( CDFG 1965).

Much of the historical fall run spawning area in the Sacramento River was below major dam sites, and therefore the fall run was not as severely affected by early water projects as were spring and winter runs ( Reynolds et al. 1993). Extreme stream temperatures are a major limiting factor in juvenile production; gravel depletion, fluctuating flows, flow reversals in the delta, point and non point source pollution, rearing habitat limitations, and losses at diversions also limit natural production ( Dettman et al. 1987, CACSST 1988).

Spawning escapement has been estimated using a variety of survey methods. The larger spawning populations are estimated using modified Schaeffer or Jolly Seber multiple markrecapture methods with tagged carcasses ( Reavis 1984). The fall and late fall runs in the mainstem Sacramento River have been monitored since 1967 by counts in the fishways at Red Bluff Diversion Dam. Since 1992, the dam reservoir has been drawn down until May to allow the winter run to pass unimpeded. This has precluded counting the late fall run since 1992 and has only permitted monitoring the last 15% of the winter run.

The bulk of the spawning escapement has been to the Feather and American Rivers and to Battle Creek ( Fig. 29, Appendix E). The long term trends in escapement are relatively stable, while the recent trends are mixed ( Fig. 30, Appendix E). These are all streams with major salmon hatcheries. State hatcheries on the American and Feather Rivers transport their smolts to saltwater for release to avoid mortality in the delta due to flow reversals, unscreened diversion dams, and predators. Transportation of smolts increases the straying rate of adults when they return and makes it more difficult to account for hatchery strays in the spawning escapement ( Cramer 1989). In the San Joaquin River Basin, homing fidelity may be more dependent on the presence of sufficient instream flows ( CDFG 1997f).

Estimates of the relative contribution of hatchery and natural fish to spawning escapements are difficult to obtain. According to Dettman et al. ( 1987), for 1978 84 an average of 20% of the ocean catch of Central Valley salmon, originated at Feather River Hatchery and 24% at Nimbus Hatchery. For the same period, total Sacramento River spawning escapement was comprised of 22% Feather River Hatchery origin and 26% Nimbus Hatchery origin; 78% of the total Feather River run and 87% of the American River run were hatchery fish. For this period, natural production averaged only 12,000 fish in the Feather River and 8,000 fish in the American River. An alternative analysis ( Cramer 1989) concluded that total hatchery contribution to the Sacramento River run for 1978 87 was only about one third, and hatchery proportions in escapement were only 26% in the Feather River and 29% in the American River. Methods used in both studies have biases; Dettman and Kelley's estimates were biased toward hatchery fish and Cramer's estimates toward natural fish. Cramer suggested that the true proportions are probably somewhere between the two groups of estimates. 201 Fall and late fall run chinook salmon in the Central Valley have been propagated for more than a century. In general, a relatively small number of hatcheries have accounted for the tens of millions of fall run fish planted annually. The overwhelming majority of fish used have come from stocks within this ESU ( Table 6, Appendix D). However, the practice of releasing fish off station, especially into the Sacramento River Delta region, has resulted in widespread straying by hatchery reared fish ( Bartley and Gall 1990, Fisher 1995). Hatchery strays represent a considerable proportion of fish spawning naturally in many rivers, even those without hatcheries. Straying, in conjunction with frequent exchanges of surplus eggs between hatcheries, may be responsible for the low levels of genetic differentiation among fall run chinook salmon stocks in the Central Valley ( Bartley and Gall 1990). The high contribution of hatchery fish to naturally spawning escapement may be due, in part, to the high survival of hatchery fish that are transported to the Sacramento River Delta ( Dettman et al. 1987).

In contrast to the situation with the fall run, the culture of late fall run fish has been relatively limited. The majority of production has come from one hatchery ( Coleman NFH) and only within the last 20 years. Late fall run fish releases constituted less than 2% of the combined fall and late fall run releases for this ESU.

Recent ( 1990 94) ocean harvest rate indices ( Central Valley Index= catch / [ catch + escapement]) have been in the range of 71 79% ( PFMC 1996b). Freshwater recreational harvest is believed to be increasing and approaching 25% ( PFMC 1997). Late fall fish are larger in size and experience higher harvest rates. The Central Valley Index is not a true harvest rate since it does not distinguish between races or cohorts, does not include freshwater catch or ocean catch landed north of Point Arena, California, and does not include shaker mortality ( hook and release mortality of undersized fish).

Angler harvest in the Sacramento River Basin was estimated by creel census in 1991, 1992, and 1993 ( Wixom see footnote 10, Wixom et al. 1995). The creel census data provide a harvest estimate of approximately 20% in freshwater.

The only previous assessment of risk to stocks in this ESU is that of Nehlsen et al. ( 1991), who identified two stocks ( San Joaquin and Cosumnes Rivers) as of special concern ( Appendix E). The Cosumnes River has had no documented spawning escapement of fall run chinook salmon since 1989, and surveys in 1991 through 1994 have failed to find spawning salmon ( Big Eagle & Assoc. and LGL Ltd. 1995).

Southern Coastal Region Historically, chinook salmon were abundant in this region. Early estimates based on peak cannery pack suggest a total run size in excess of 300,000 fish in the 1910s. Total chinook salmon spawning escapement for the California portions of this region was estimated to be about 202 256,000 ( 168,000 in the Klamath River Basin and 88,000 elsewhere) in 1965 ( CDFG 1995). An escapement of 250,000 fish in 1969 was estimated by expanded angler catch.

Chinook salmon in this region have been strongly affected both by losses and alterations of freshwater habitats and by a long history of hatchery production. PFMC ( 1995) identified all of the major rivers in this area as having chronic instream flow problems. Bottom et al. ( 1985) cited low stream flows and high summer temperatures as problems throughout the southern Oregon coastal area. Timber harvesting and associated road building occur throughout the region on federal, state, tribal and private lands. These activities may increase sedimentation and debris flows and reduce cover and shade, resulting in aggradation, embedded spawning gravel, and increased water temperatures ( CACSST 1988, NMFS 1996b). The Rogue and Klamath River Basins have been sites of active mining since the mid 1800s and suction dredge mining still occurs.

Hatchery facilities in this area began operations late in the nineteenth century. These early hatcheries were operated by private companies and state and federal agencies with the goal of restoring declining fisheries. With the exception of operations on the Rogue River, which propagated spring run chinook salmon, these hatcheries primarily reared fall run chinook salmon. Dam construction and habitat degradation reduced or eliminated several runs and forced the closure of a number of hatcheries. Currently the Cole Rivers Hatchery and Trinity River Hatchery produce the majority of all spring run chinook salmon in this area. A number of smaller hatcheries release locally derived fall run chinook salmon, but the major proportion of fall run releases comes from the Iron Gate Hatchery ( 197 million since 1966) and Trinity River Hatchery ( 69 million since 1969) ( Appendix D).

4) Southern Oregon and California Coastal ESU The peak historic cannery pack of chinook salmon in the range of this ESU was 31,000 cases in 1917, indicating a run size of about 225,000 at that time. CDFG ( 1965) estimated escapement for the California portion of the ESU at about 88,000 fish, predominantly in the Eel River ( 55,500) with smaller populations in the Smith River ( 15,000), Redwood Creek, Mad River, Mattole River ( 5,000 each), Russian River ( 500), and several smaller streams in Del Norte and Humboldt counties. Based on the 1968 angler catch records for the Oregon portion of the ESU ( which estimated escapements of about 90,000 fish), the average escapement for the entire ESU in the 1960s was estimated to be 178,000 fish.

Within this ESU, recent abundance data vary regionally. Dam counts of upstream migrants are available on the South Fork Eel River at Benbow Dam from 1938 to 1975, and at Gold Ray Dam on the Rogue River from 1944 to the present. Counts at Cape Horn Dam on the upper Eel River are available from the 1940s to the present, but they represent a small, highly variable portion of the run. 203 In the Oregon portion of this ESU, coastal rivers are monitored by surveys of index reaches. Surveys were begun in 1948 with the intent of monitoring trends in escapement rather than estimating total escapement ( Cooney and Jacobs 1994). Because the original selection criteria for index reaches included ease of access and availability of spawners, spawner densities in these index reaches are not representative of spawner densities in other areas. Consequently, though the spawner counts in index reaches may be relatively precise, they are not accurate for assessing abundance.

In 1953 Oregon began using catch report cards, called " punch cards," to report angler catch in rivers and estuaries ( Nicholas and Hankin 1988). This reporting system provides precise estimates of catch on a river by river basis, which can be expanded by the harvest rate for each river to provide estimates of terminal run size. Unfortunately, freshwater and estuarine harvest rates are poorly known for most rivers, and vary considerably. Harvest rates depend on fishing effort and angler success rates. Fishing effort varies with run size, weather, river conditions, and angler success rate. Angler success rates, in turn, depend on weather and river conditions, as well as run size. Nicholas and Hankin ( 1988) used estimates of average angler harvest rates to convert angler catch to run size. These estimates, although imprecise, are probably more accurate for estimating average run size than expansions based on peak index counts.

In assessing abundance and trends we used expansions of angler catch from ODFWs punch card database ( ODFW 1993) and Nicholas and Hankin's ( 1988) average harvest rates to calculate geometric means of terminal run size and spawning escapement for the most recent 5 year period ( 1990 94). Trends were calculated from either the peak index counts or from dam counts, where they were available.

Expanded angler catch data produce a 5 year geometric mean spawning escapement of 132,000 ( run size of 148,000) for the Oregon portion of this ESU. The majority of this escapement ( 126,000) has been the spring and fall runs in the Rogue River ( Fig. 31, Appendix E). No total escapement estimates are available for the California portion of this ESU, although partial counts indicate that escapement in the Eel River exceeds 4,000. Data available to assess trends in abundance are limited. Recent trends have been mixed, with predominantly strong negative trends in the Rogue and Eel River basins, and mostly upward trends elsewhere. Longer term trends, where data are available, are flatter ( e. g. Rogue River) ( Fig. 32, Appendix E).

Habitat loss and/ or degradation is widespread throughout the range of the ESU. The California Advisory Committee on Salmon and Steelhead Trout ( CACSST 1988) reported 204 Figure 31. Recent 5 year geometric mean spawning escapement for chinook salmon populations in Southern Oregon and California Coastal ( 4) and Upper Klamath and Trinity rivers ( 5) ESUs. All data are for fall run, except as noted ( see Appendix E for details). 205 206 Figure 32. Trends ( percent annual change) in abundance for chinook salmon populations in Southern Oregon and California Coastal ( 4) and Upper Klamath and Trinity ( 5) ESUs. All data are for fall run, except as noted ( see Appendix E for details). 207 habitat blockages and fragmentation, logging and agricultural activities, urbanization, and water withdrawals as the most predominant problems for anadromous salmonids in California's coastal basins. They identified associated habitat problems for each major river system in California. CDFG ( 1965, Vol. III, Part B) reported that the most critical habitat factor for coastal California streams was " degradation due to improper logging followed by massive siltation, log jams, etc." They cited road building as another cause of siltation in some areas. They identified a variety of specific critical habitat problems in individual basins, including extremes of natural flows ( Redwood Creek and Eel River), logging practices ( Mad, Eel, Mattole, Ten Mile, Noyo, Big, Navarro, Garcia, and Gualala Rivers), and dams with no passage facilities ( Mad, Eel, and Russian Rivers), and water diversions ( Eel and Russian Rivers). We expect that such problems also occur in Oregon streams within the ESU. The Rogue River Basin in particular has been affected by mining activities and unscreened irrigation diversions ( Rivers 1963) in addition to problems resulting from logging and dam construction. Kostow ( 1995) estimated that one third of springrun chinook salmon spawning habitat in the Rogue River was inaccessible following the construction of Lost Creek Dam ( RKm 253) in 1977. Recent major flood events ( February 1996 and January 1997) have probably affected habitat quality and survival of juveniles within this ESU. Although we have little information on the effects of these floods in this ESU, the effects are probably similar to those discussed for the Oregon and Washington Coastal Region below.

Artificial propagation programs have been less extensive in the Southern Oregon and Coastal California ESU than in neighboring regions. The Rogue, Chetco and Eel River Basins and Redwood Creek have received numerous releases, derived primarily from local sources. In contrast, releases into the Russian River have been predominately from a variety of sources from outside the ESU ( Table 6, Appendix D). In the absence of genetic information, it is not possible to evaluate the long term impact of these transfers into the Russian River. San Francisco Bay has also received considerable numbers of introduced fish, the majority of which are off station releases of Central Valley fall run chinook salmon. Information on the impact of hatchery derived fish on naturally spawning populations is limited. For the entire ESU, the hatchery contribution to total spawning escapement is probably low. However, the hatchery to wild ratio of Rogue River spring run chinook salmon, as measured at Gold Ray Dam ( RKm 201), has exceeded 60% in some years ( Kostow 1995). The majority of the hatchery fish counted at Gold Ray Dam probably return to Cole Rivers Hatchery ( located above the dam), but rates of straying into natural spawning habitat are unknown.

Ocean harvest rates for this ESU have not been estimated, but should be comparable to ocean harvest rates on Klamath fall run chinook salmon ( 21% in 1991 [ PFMC 1996a]). Freshwater and estuarine harvest rates are on the order of 25 30% ( calculated from data in PFMC 1996b  Table B4).

Previous assessments of stocks within this ESU have identified several stocks as being at risk or of concern ( Appendix E). Nehlsen et al. ( 1991) identified seven stocks as at high extinction risk and seven stocks as at moderate extinction risk. Higgins et al. ( 1992) provided a more detailed analysis of some of these stocks, and identified nine chinook salmon stocks as at 208 risk or of concern. Four of these stocks agreed with the Nehlsen et al. ( 1991) designations, while five fall run chinook salmon stocks were either reassessed from a moderate risk of extinction to stocks of concern ( Redwood Creek, Mad River, and Eel River) or were additions to the Nehlsen et al. ( 1991) list as stocks of special concern ( Little and Bear Rivers). In addition, two fall run stocks ( Smith and Russian Rivers) that Nehlsen et al. ( 1991) listed as at moderate extinction risk were deleted from the list of stocks at risk by Higgins et al. ( 1992), although the USFWS ( 1997a) reported that the deletion for the Russian River was due to a finding that the stock was extinct. Nickelson et al. ( 1992) considered 11 chinook salmon stocks within the ESU, of which 4 ( Applegate River fall run, Middle and Upper Rogue River fall runs, and Upper Rogue River spring run) were identified as healthy, 6 as depressed, and 1 ( Chetco River fall run) as of special concern due to hatchery strays. Huntington et al. ( 1996) identified three healthy Level II fall run stocks in their survey ( Applegate and Middle and Upper Rogue Rivers).

5) Upper Klamath and Trinity River ESU Peak run size in this ESU was estimated to be about 130,000 chinook salmon in 1912 ( from peak cannery pack of 18,000 cases). CDFG ( 1965) estimated spawning escapement of chinook salmon within the range of this ESU to be about 168,000 adults, split about evenly between the Klamath ( 88,000) and Trinity ( 80,000) Rivers.

Recent spawning escapements and run sizes to the Klamath and Trinity Rivers are monitored by a combination of state, federal and tribal agencies. Hatchery returns to Iron Gate and Trinity Hatcheries are enumerated by the state. CDFG has also estimated escapement to the Trinity River, Scott River, Salmon River, and Shasta River using Petersen estimates from marks applied to upstream migrants at weirs, or tags applied to carcasses in stream surveys ( Pisano 1993, Aguilar et al. 1996). Escapement to smaller tributaries is generally estimated from redd counts. The fall run on the Klamath River was counted at Klamathon Racks beginning in 1929, but these counts were discontinued when Iron Gate Dam was constructed and the mitigation hatchery began operation in the early 1960s. Escapement of fall run chinook salmon to the Shasta River has been counted at a weir, or estimated on the basis of recovery of marks applied at the weir, since 1930 by CDFG. Escapement of spring run chinook salmon to the Salmon River has been estimated by the U. S. Forest Service by snorkel surveys of holding habitat in the summer since 1980. Tribal commercial, subsistence, and ceremonial harvest has been monitored by the U. S. Fish and Wildlife Service, the Hoopa Valley Tribe, and the Yurok Tribe.

The 5 year ( 1992 96) geometric mean of recent spawning escapements to natural spawning areas was about 48,000 fish ( Fig. 31, Appendix E). Fish returning to the two hatcheries in the basin accounted for 38% of the total ( natural + hatchery) spawning escapement. Trends in escapement are relatively stable ( Fig. 32, Appendix E). The long term trend statistics mask the fact that minimal abundances were observed in all areas in 1989 91, and populations have increased sharply since then. 209 For over a hundred years, hatcheries have operated in the Upper Klamath and Trinity River Basins. Several million chinook salmon eggs were introduced into the region from the Central Valley, but the success of these introductions is doubtful, especially given the practice of releasing fry during the early part of this century. Dam construction on the Klamath and Trinity Rivers led to the construction of two major hatchery complexes ( Iron Gate Hatchery and Trinity River Hatchery) to mitigate the loss of spawning and rearing habitat. Within the last 30 years, these 2 mitigation hatcheries have accounted for the overwhelming majority of artificially propagated fish in this region. Between 1964 and 1994, 50 million spring and 236 million fall run chinook salmon ( almost all from local sources) have been released ( Table 6, Appendix D). It has been estimated that 11.2% of the spring run fish and 31.2% of the fall run fish naturally spawning in the mainstem Trinity River were of hatchery origin in 1994 ( Aguilar 1995). Similarly, Barnhart ( 1995) reported that considerable numbers of coded wire tagged fish from the Iron Gate Hatchery are recovered among naturally spawning populations in Bogus Creek, and to a lesser extent in the Shasta River. Information on the contribution of hatchery fish to naturally spawning populations in other tributaries is lacking. Since systematic monitoring of spawning escapement began, the percentage of hatchery returns to total escapement has increased from 18% in 1978 82 to 26% in 1991 95 ( PFMC 1996b).

The current management goal for fall run chinook salmon in the Klamath River Basin is an escapement of 33 34% of potential spawners in each brood while providing a minimum of 35,000 adult spawners to natural spawning areas ( PFMC 1994). Because of low abundance, recent management has been for a minimum escapement goal rather than the brood escapement rate. As a result, ocean fishery impact rates have decreased from 44 65% during the period 1986 to 1990 to 21% in 1991. Ocean fishery impact rates have remained below 20% since 1991 ( PFMC 1996a).

Habitat loss and/ or degradation is widespread throughout the range of the ESU. Upper basin habitat has been blocked by dam construction in both the Klamath and Trinity River Basins ( KRBFTF 1991). NMFS ( 1996b) cited several factors affecting the habitat in this region, including water diversion/ extraction, habitat blockages, hydropower development, and logging, mining, and agricultural activities. CDFG ( 1965, Vol. III, Part B) identified several critical habitat factors: water diversions and resulting low flows and high temperatures ( Shasta, Scott, and Trinity Rivers), logging resulting in log jams and siltation ( Klamath River), and small dams for present water diversion and at abandoned gold mines ( Klamath River). They also cited siltation resulting from past mining activities as a problem in the Scott River, and noted that habitat in the Salmon River Basin was in very good condition. Timber harvesting and associated road building are widespread in the basin and result in increased sedimentation and debris flow and reduced cover and shade ( KRBFTF 1991). Fifty percent of the spawning habitat in the Trinity River Basin was lost following the construction of Lewiston Dam at RKm 249 ( Moffett and Smith 1950). Gold mining has occurred in this area since the mid 1800s. Lode mining for gold, copper, and chromite, which may introduce cyanide into the water and result in fish kills, continued in the Klamath River Basin until 1987. Suction dredge mining, which directly results in gravel disturbance and sedimentation, still continues in the basin ( KRBFTF 1991). 210 Previous assessments of stocks within this ESU have identified several stocks as being at risk or of concern ( Appendix E). Nehlsen et al. ( 1991) identified seven stocks as extinct, two stocks ( Klamath River spring run chinook salmon and Shasta River fall run chinook salmon) as at high extinction risk, and Scott River fall run chinook salmon as of special concern. Due to lack of information on chinook salmon stocks that are presumed to be extinct, the relationship of these stocks to existing 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) provided a more detailed analysis of some of the stocks identified by Nehlsen et al. ( 1991), classifying three chinook salmon stocks as at risk or of concern. Of the three stocks Higgins et al. ( 1992) listed as at high risk of extinction, two matched with the Nehlsen et al. ( 1991) findings ( Klamath River spring run and Shasta River fall run), while one stock was added to the list ( South Fork Trinity River spring run). Additionally, three chinook salmon stocks were identified as of special concern. Of these, Higgins et al. ( 1992) classified one ( Scott River fall run) in agreement with that of Nehlsen et al. ( 1991), while two others ( Trinity River spring run and South Fork Trinity River fall run) were additions to the earlier list.

Oregon and Washington Coastal Region This region includes the Oregon Coast, Washington Coast, and Puget Sound ESUs. Chinook salmon were abundant in this region near the turn of the century, when estimates based on peak cannery pack suggested peak runs of near one million fish in the three ESUs combined. This region includes the Coastal Range and Puget Lowlands ecoregions ( see " Ecological Features" above) and is characterized by numerous short rivers and streams draining the coast ranges and west slope of the northern Cascade Mountains, with relatively few large rivers ( Umpqua, Chehalis, and Skagit Rivers).

Chinook salmon in this region have been strongly affected by losses and alterations of freshwater habitats. Bottom et al. ( 1985) and Bishop and Morgan ( 1996) provide thorough reviews of habitat problems. Timber harvesting and associated road building occur throughout the region on federal, state, tribal and private lands. These activities may increase sedimentation and debris flows, reduce cover and shade, and may reduce recruitment of large woody debris to streams, resulting in aggradation, embedded spawning gravel, loss of pools, and increased water temperatures. Agriculture is also widespread in the lower portions of river basins and has resulted in widespread removal of riparian vegetation, rerouting of streams, degradation of streambanks, and summer water withdrawals. Urban development has substantially altered watershed hydrodynamics and affected stream channel structure in many parts of Puget Sound and the Oregon Coast.

This region ( and parts of the southern coastal region discussed above) has experienced severe winter floods in recent years which could have affected chinook salmon habitat and survival of in stream juveniles during the flood events. The following discussion summarizes information available regarding floods in February 1996. 211 Between November 1995 and April 1996, the Pacific Northwest and California experienced a series of storm and flood events. High winds, heavy rainfall, rapid snowmelt, numerous landslides and debris torrents, mobilization of large woody debris and high runoff occurred over portions of California, Oregon, Washington, Idaho, and Montana ( USFS and USBLM 1996). These storms also had a potentially large effect on northern California and Oregon coast coho salmon and their freshwater habitats. Abnormally high rainfall and warm temperature, on top of already elevated stream levels and saturated soils resulted in the floods of February 1996; considered to be 100 year floods in many Oregon coastal basins ( USFS and USBLM 1996, Bush et al. 1997). USFS and USBLM ( 1996) estimated landscape scale habitat impacts from the February 1996 flood on federal lands in Washington and Oregon. They identified the Wilson Trask Nestucca, Siuslaw, and Alsea Basins as experiencing landslides, gullies/ surface erosion, bedload deposition, channel migration, and LWD deposition, and considered the Wilson Trask Nestucca area as one of four areas with the highest rates of disturbance from the flood, and the Siuslaw as one of four areas with the second highest rates of disturbance from the flood. Pacific Watershed Associates ( PWA undated) conducted aerial surveys to provide an assessment of the nature, magnitude and spatial distribution of watershed erosion and impacts to streams channels in the middle Coast Range, including the Smith ( Umpqua), Siuslaw, Alsea, and Yaquina Basins. They report that areas with the greatest impact included Hadsall and Knowles Creeks ( Siuslaw River) and Lobster Creek ( Alsea River), and those watersheds with a combination of steep slopes, unstable bedrock geology, recent timber harvesting, and high road densities within an altitude range where precipitation intensities were probably the greatest ( 500 m. in the Coast Range). They also stressed that landslides were highly correlated with forestry management activities and originated from recent clear cuts and forest roads at much higher frequencies than from wilderness or unmanaged areas. In addition to these observations, PWA concluded that the floods may have had long term effects on watershed habitats. Siuslaw National Forest ( SNF 1996) staff surveyed 500,000 hectares of central Oregon coast forests using aerial photographs to assess the frequency and character of landslides. They detected 1,686 slides, 41% of which were associated with roads, 36% with recent (< 20 year old) clear cuts, and 23% with forested areas. They also found that subbasins in the southern portion of the area assessed ( Coos, Umpqua, Siltcoos and Siuslaw) experienced from 1.5 to 2.5 times more landslides by area than more northern areas. They attribute this difference to both landtype associations of the basins and the differential intensity of the storm as it moved onshore. They also determined that " stabilized" roads ( those treated to reduce failure) were less likely to be the source of large (> 1700 m3) landslides than untreated roads.

With regard to impacts to in stream coho salmon habitat, ODFW has conducted random resurveys of habitat for 105 reaches since the floods ( Moore and Jones 1997). This survey effort indicated that along the North Oregon Coast ( Salmon River to Columbia River), 7.5% of habitats received " no impact" ( no perceivable impact), 60% of habitats received " low impact" ( high water and scour and deposition impacts), 28% received " moderate impact" ( channel modified impact), and 3.4% received " torrents" ( and of these levels associated with debris torrents or dam break floods). Along the mid coast ( Siuslaw River to Devils Lake tributaries), 2% of habitats received " no impact," 91% received " low impact," 7% " moderate impact," and 0.1% " torrents." Habitat 212 changes included both positive and negative effects, depending on the area. Bush et al. ( 1997) noted that there were substantial changes in pool and riffle areas, large woody debris, and streambed substrates in streams following the floods, based on differences in stream reaches initially surveyed in 1992 95 and resurveyed in 1996. Decreases in pool area ranged from 10 to 50%, and largely resulted from a 60% loss of beaver pond habitat. Large woody debris decreased by approximately 25% from the initial surveys, although much of the lost wood had been pushed up onto the floodplain or out of the active channel. Overall, large amounts of gravel were added to most streams, and new gravel bars were common. Dewberry et al. ( 1996) documented changes in salmon habitats in Knowles Creek. ( Siuslaw River). Twenty four debris torrents occurred in anadromous fish bearing reaches of the basin, four of which exceeded 3,000 m2. Although the floods had little impact on parts of the basin, including an old growth section, other areas were highly affected.

Within the last 50 years, over 2.5 billion spring, summer, and fall run chinook salmon have been released from state, federal, and/ or tribal hatcheries in this region, with the fall run constituting the majority of these releases. In addition, large, privately owned sea ranching programs operated in recent years on the Oregon coast. A number of hatcheries already were in existence on rivers around Puget Sound by the turn of the century, and many of those are still in operation. In coastal areas, the earliest and most intense artificial propagation efforts have been, and continue to be, in coastal rivers near the mouth of the Columbia River. The majority of these hatcheries have been built primarily for fisheries enhancement, rather than mitigation for habitat loss. However, hatcheries on the Skagit, White, Skokomish, and Elwha Rivers operate to mitigate the loss of habitat due to dam construction ( WDF et al. 1993, Kostow 1995). Although there have been numerous introductions of lower Columbia River chinook salmon stocks into the region, the majority of fish released have been derived from local stocks ( Table 6, Appendix D). Some artificial propagation programs on the Oregon and Washington coasts have recently begun to alter their primary mission from fisheries enhancement to the supplementation of natural populations.

6) Oregon Coast ESU ODFW has identified 45 populations of chinook salmon in the range of this ESU ( Kostow 1995). Historical abundance estimates for this ESU are available only from cannery pack data. Peak cannery pack was 30,967 cases in 1896, suggesting a peak run size of about 225,000 fish at that time. Abundance at that time does not reflect " pristine" conditions, as extensive logging with associated splash dams were already impacting stream habitat.

Types of data available in this ESU were much the same as within the Oregon portion of the Northern California/ Southern Oregon ESU. Punch card data and average estimated harvest rates were used to estimate recent spawning run size from freshwater angler harvest. Survey data from spawner surveys conducted by ODFW were used to estimate trends in abundance. The only other data available that provided reasonably long time series were fish counts of spring and fall runs at Winchester Dam on the North Umpqua River. 213 The 5 year geometric mean of terminal run size calculated from angler catch was approximately 170,000 fish ( spawning escapement of 136,000) distributed among numerous spawning populations ( Fig. 33, Appendix E). Most long term trends in escapement indices were stable or increasing, with only one population declining at more than 10% per year; short term trends were more variable, with a mix of increases and decreases ( Fig. 34, Appendix E).

Bottom et al. ( 1985) cited low streamflows and high summer temperatures exacerbated by water withdrawals as problems for many streams ( notably Tillamook Bay tributaries and Alsea, Siletz, Siuslaw, and Umpqua Rivers) and noted that agricultural and logging practices have led to serious riparian habitat losses. They also cited serious modification of stream structure by logging, splash dams, and widespread removal of beaver dams, but concluded that recent efforts have resulted in more stream miles being accessible to anadromous fish now than 100 years ago. Effects of recent floods were discussed for the Oregon and Washington Coastal Region above.

The first hatcheries were built in this area in 1902. Since the 1930s, artificial propagation programs have released nearly 400 million fall and spring run fish into this area, with nearly onequarter of all the fish released coming from sources outside the ESU ( Table 6, Appendix D). During much of this period, the impact of these releases may have been reduced by the large size of naturally spawning runs in most rivers. However, during the 1940s and 1950s many rivers were experiencing record low natural runs, and hatchery releases may have had a significant impact on local populations during this period ( Kostow 1995). Chinook salmon from the Trask River have been used to establish hatchery broodstock in other systems in the Tillamook and Nestucca River Basins ( Kostow 1995).

The contribution of hatchery derived fish to total escapement is generally thought to be rather low ( Kostow 1995). In 1990, the hatchery contribution to the Tillamook Bay fishery was only 15% ( Kostow 1995). In contrast, hatchery contribution to total spawning escapement has been reported to be highest ( approximately 50%) among fall run chinook salmon populations in the Salmon and Elk Rivers ( ODFW 1995). Additionally, hatchery reared spring run chinook salmon constituted 50% of the spring run on the North Fork Umpqua River in the 1980s, 214 215 Figure 33. Recent 5 year geometric mean spawning escapement for chinook salmon populations in Oregon Coast ( 6) ESU. All data are for fall run, except as noted ( see Appendix E for details). 216 Figure 34. Trend s ( percent annual change) in abundance for chinook salmon populations in Oregon Coast ( 6) ESU. All data are for fall run, except as noted ( see Appendix E for details). 217 although currently the figure may be as low as 30% ( Kostow 1995). Estimates of the impact of hatchery strays is limited, but in the Sixes River, hatchery strays were reported to constitute up to 20% of the natural spawners ( Kaczynski and Palmisano 1993).

Freshwater/ estuarine harvest rates are on the order of 20 25% ( Nicholas and Hankin 1988). Ocean exploitation rates have ranged from 24% to 48%, with total exploitation rates in the range of 45 68%, and an average near 60% ( brood years 1982 89) ( PSC 1994).

Previous assessments of stocks within this ESU have identified several stocks at risk or of concern; however, the preponderance of stocks have been identified as healthy ( Appendix E). Nehlsen et al. ( 1991) identified two stocks as at high extinction risk ( South Umpqua River and Coquille River spring run), one stock as at moderate extinction risk ( Yachats River fall run) and five stocks as of special concern. Of the 44 stocks within this ESU considered by Nickelson et al. ( 1992), 26 were identified as healthy ( with 2 stocks containing small, variable runs), 2 as depressed ( South Umpqua River and Coquille River spring run chinook salmon), 7 as of special concern due to hatchery strays, and 9 of unknown status ( 4 of which they suggested may not be viable). Huntington et al. ( 1996) identified 18 stocks in their survey: 6 healthy Level I and 12 healthy Level II stocks.

7) Washington Coast ESU Historical harvest of chinook salmon in this ESU reached a peak in 1911, when 26,490 cases were packed at canneries. This corresponds to a peak run size of about 190,000 fish.

At the present time, run size and spawning escapement in this ESU are monitored by WDFW and the Western Washington Treaty Indian Tribes. Management objectives, terminal fisheries and monitoring methods vary considerably over the ESU. Willapa Bay is managed for hatchery production and is monitored by WDFW ( WDF et al. 1993). Since 1988, 65% or more of the natural escapement in Willapa Bay has consisted of hatchery fish ( WDF et al. 1993). Escapement is monitored by redd counts, and natural production is not believed to be selfsustaining Monitoring of Grays Harbor is also conducted by WDFW through redd counts. Most spawning populations in Grays Harbor are believed to have little hatchery influence.

In rivers further north, monitoring is conducted by the Western Washington Treaty Indian Tribes. Time series of spawning escapement estimates are relatively short, and the longest abundance data series are from tribal net fisheries conducted in the estuaries. Most spawning stocks are believed to be of native origin with little hatchery influence. Notable exceptions are Sol Duc River spring run chinook salmon, which are an introduced stock, and the Quinault River fallrun chinook salmon stock, which is propagated as a Pacific Salmon Treaty indicator stock.

Recent average natural spawning escapement, the sum of 5 year geometric means for individual populations, has been over 50,000 spawners ( Fig. 35, Appendix E). Long term trends 218 are about evenly split between increases and declines, but with most larger populations increasing ( Fig. 36, Appendix E). Short term trends are predominantly negative, strongly so in the Quillayute Basin and Willapa Bay tributaries.

All basins are affected ( to varying degrees) by habitat degradation. Tributaries inside Olympic National Park have been least affected by human activities For other areas, major habitat problems are related primarily to forest practices, including mass wasting resulting in sedimentation in spawning grounds, lack of large woody debris, and lack of streamside shade. For example, WDF et al. ( 1993) reported that the Hoko River has been heavily impacted by past logging practices, with over 300 mass wasting events recorded in the last 50 years. Clearing of instream wood was common practice until the 1970s, resulting in channel downcutting and bedload scour and fill which, in combination with moderate to high levels of fine sediments in gravel beds, affects egg survival in many areas. Bishop and Morgan ( 1996) identified a variety of critical habitat issues for streams in the range of this ESU, including changes in flow regime ( Hoko and, Quillayute Rivers), sedimentation ( Chehalis, Hoh, Hoko, and Quillayute Rivers), high temperatures ( Chehalis, Hoko, and Quillayute Rivers), streambed instability ( Hoko and Quillayute Rivers), estuarine loss ( Chehalis River), loss of large woody debris ( Hoko River), and loss of pool habitat ( Hoko River). Of the streams they reviewed, only in the Queets and Quinault River Basins were chinook salmon not considered to be substantially limited by habitat problems. Upper basins of several streams in this region lie within Olympic National Park and are fully protected from effects of logging and most other habitat changes. The Puget Sound Salmon Stock Review Group ( PSSSRG 1997) reviewed causes of declines in western Strait of Juan de Fuca and described habitat conditions for rivers in that portion of this ESU, concluding that timber harvest and hydromodifications have reduced both capacity and quality of salmon habitats.

WDF et al. ( 1993) classified 9 out of 31 stocks in this ESU as having cultured or composite production ( indicating that a stock is sustained to some extent by artificial propagation). Some 319 million chinook salmon have been released into Washington coastal waters since 1952. Fall run chinook salmon have been propagated in much larger numbers than spring run chinook salmon ( 309 vs. 10 million). On average, approximately 19% of all hatchery releases have been from sources outside of the ESU. However, the Pysht, Hoko, and Chehalis Rivers have received proportionally larger introductions of fish from outside the ESU. Releases into these three rivers constitute more than half of the total of all non ESU releases ( Table 6, Appendix D).

Significant numbers of hatchery strays have been found in naturally spawning populations in the Satsop and Willapa Bay Rivers ( Marshall et al. 1995), although their reproductive success is unknown. Furthermore, there has been considerable interbreeding between the non native Sol Duc Hatchery spring run chinook salmon stock and the native 219 Figure 35. Recent 5 year geometric mean spawning escapement for chinook salmon populations in Washington Coast ( 7) ESU ( see Appendix E for details). 220 221 Figure 36. Trends ( percent annual change) in abundance for chinook salmon populations in Washington Coast ( 7) ESU ( see Appendix E for details). 222 summer run chinook salmon run in the Sol Duc River ( WDF et al. 1993). With the exception of the Sol Duc Hatchery spring run, most of the introductions of non native spring run fish are thought to have been unsuccessful ( WDF et al. 1993, Marshall et al. 1995).

Harvest rates on Washington coast chinook salmon stocks have been moderate, with ocean exploitation rates averaging 44 52%, and total exploitation rates averaging 48 56% ( 1982 89) for Hoko and Sooes stocks ( PSC 1994).

Previous assessments of stocks within this ESU have identified several as being at risk or of concern, but more stocks have been identified as healthy than at risk ( Appendix E). Nehlsen et al. ( 1991) identified one stock as extinct ( Pysht River fall run), one as possibly extinct ( Ozette River fall run), and one as at high risk of extinction ( Wynoochee River spring run), although there is some question whether the Wynoochee River spring run ever existed ( WDFW 1997a). WDF et al. ( 1993) considered 31 stocks within the ESU, of which 18 were reported to be of native origin and predominantly natural production. The status of these 18 stocks was 11 healthy, 4 depressed, and 3 unknown. The status of the remaining ( not native/ natural) stocks was nine healthy, two depressed, and two unknown. The Sol Duc River spring run and Raft River fall run chinook salmon were not considered an ESA issue by the BRT ( stocks were not historically present in the watershed or current stocks are not representative of historical stocks) but was included to give a complete presentation of stocks identified by WDF et al. ( 1993). Huntington et al. ( 1996) identified 12 stocks in their survey: 1 healthy Level I stock ( Quillayute/ Bogachiel River fall run) and 11 healthy Level II stocks.

8) Puget Sound ESU The peak recorded harvest landed in Puget Sound occurred in 1908, when 95,210 cases of canned chinook salmon were packed. This corresponds to a run size of approximately 690,000 chinook salmon at a time when both ocean harvest and hatchery production were negligible. ( This estimate, as with other historical estimates, needs to be viewed cautiously; Puget Sound cannery pack probably included a portion of fish landed at Puget Sound ports but originating in adjacent areas, and the estimates of exploitation rates used in run size expansions are not based on precise data.) Recent mean spawning escapements totaling 71,000 correspond to a run entering Puget Sound of approximately 160,000 fish. Based on an exploitation rate of one third in intercepting ocean fisheries, the recent average potential run size would be 240,000 chinook salmon ( PSC 1994).

Currently, escapement to rivers in Puget Sound and Hood Canal is monitored by WDFW and the Northwest tribes. Populations least affected by hatcheries are in the northern part of the sound in the Nooksack, Skagit, Stillaguamish, and Snohomish River systems.

The Nooksack River has spring/ summer runs in the north and south forks. The North Fork escapement is monitored by carcass surveys and is influenced by a hatchery on Kendall Creek 223 ( part of a native stock rebuilding program). Escapement to the South Fork is monitored by redd counts, and the stock is believed to have little hatchery influence. Both stocks are considered critical by WDFW because of chronically low spawning escapements. The Skagit River supports three spring runs, two summer runs, and a fall run. Mean spawning escapement of the summer/ fall run has been below the escapement goal and declining ( Fig. 37 38, Appendix E). Terminal run size has been declining, and escapement has been maintained at the expense of terminal fisheries. Of the five stocks identified by WDF et al. ( 1993), two are rated healthy, two depressed, and one of unknown status. On the Stillaguamish River, two runs have been identified. The combined escapement goal has been met only twice since 1978, and both runs are considered depressed. Of four runs identified in the Snohomish system, two are rated depressed, one unknown, and one as healthy. The single stock identified as " healthy" ( Wallace River) is considered to be derived from hatchery strays and has experienced a severe recent decline.

The 5 year geometric mean of spawning escapement of natural chinook salmon runs in North Puget Sound for 1992 96 is approximately 13,000 ( Fig. 37, Appendix E). Both long and short term trends for these runs were negative, with few exceptions. In south Puget Sound, spawning escapement of the natural runs has averaged 11,000 spawners ( Fig. 37, Appendix E). In this area, both long and short term trends are predominantly positive.

In Hood Canal, summer/ fall run chinook salmon spawn in the Skokomish, Union, Tahuya, Duckabush, Dosewallips and Hamma Hamma Rivers. Because of transfers of hatchery fish, these spawning populations are considered a single stock ( WDF et al. 1993). Fisheries in the area are managed primarily for hatchery production and secondarily for natural escapement; high harvest rates directed at hatchery stocks have resulted in failure to meet natural escapement goals in most years ( USFWS 1997a). The 5 year geometric mean natural spawning escapement has been 1,100 ( Fig. 37, Appendix E), with negative short and long term trends ( except in the Dosewallips River).

The ESU also includes the Dungeness and Elwha Rivers, which have natural chinook salmon runs as well as hatcheries. The Dungeness River has a run of spring/ summer run chinook salmon with a 5 year geometric mean natural escapement of 105 fish ( Fig. 37, Appendix E). The Elwha River has a 5 year geometric mean escapement of 1,800 fish ( Fig. 37, Appendix E), but contains two hatcheries, both lacking adequate adult recovery facilities. Egg take at the hatcheries is augmented from natural spawners, and hatchery fish spawn in the wild. Consequently, hatchery and natural spawners are not considered discrete stocks ( WDF et al. 1993). Both of these populations exhibit downward recent trends ( Appendix E).

Habitat throughout the ESU has been blocked or degraded. In general, upper tributaries have been impacted by forest practices and lower tributaries and mainstem rivers have been 224 Figure 37. Recent 5 year geometric mean spawning escapement for chinook salmon populations in Puget Sound ( 8) ESU. 7A, 10, and 13B designate combined escapements for smaller stream systems within a fishery management region. All data are for summer/ fall run, except as noted ( see Appendix E for details). 225 Figure 38. Trends ( percent annual change) in abundance for chinook salmon populations in Puget Sound ( 8) ESU. 7A, 10, and 13B designate combined escapements for smaller stream systems within a fishery management region. All data are for summer/ fall run, except as noted ( see Appendix E for details). 226 impacted by agriculture and/ or urbanization. Diking for flood control, draining and filling of freshwater and estuarine wetlands, and sedimentation due to forest practices and urban development are cited as problems throughout the ESU ( WDF et al. 1993). Blockages by dams, water diversions, and shifts in flow regime due to hydroelectric development and flood control projects are major habitat problems in several basins. Bishop and Morgan ( 1996) identified a variety of critical habitat issues for streams in the range of this ESU including 1) changes in flow regime ( all basins), 2) sedimentation ( all basins), 3) high temperatures ( Dungeness, Elwha, Green/ Duwamish, Skagit, Snohomish, and Stillaguamish Rivers), 4) streambed instability ( most basins), 5) estuarine loss ( most basins), 6) loss of large woody debris ( Elwha, Snohomish, and White Rivers), 7) loss of pool habitat ( Nooksack, Snohomish, and Stillaguamish Rivers), and 8) blockage or passage problems associated with dams or other structures ( Cedar, Elwha, Green/ Duwamish, Snohomish, and White Rivers). The Puget Sound Salmon Stock Review Group ( PSSSRG 1997) provided an extensive review of habitat conditions for several of the stocks in this ESU. It concluded that reductions in habitat capacity and quality have contributed to escapement problems for Puget Sound chinook salmon. It cited evidence of direct losses of tributary and mainstem habitat, due to dams; of slough and side channel habitat, caused by diking, dredging, and hydromodification; and also cited reductions in habitat quality due to land management activities.

WDF et al. ( 1993) classified 11 out of 29 stocks in this ESU as being sustained, in part, through artificial propagation. Nearly 2 billion fish have been released into Puget Sound tributaries since the 1950s ( Table 6, Appendix D). The vast majority of these have been derived from local returning fall run adults. Returns to hatcheries have accounted for 57% of the total spawning escapement, although the hatchery contribution to spawner escapement is probably much higher than that, due to hatchery derived strays on the spawning grounds. In the Stillaguamish River, summer run chinook have been supplemented under a wild broodstock program for the last decade. In some years, returns from this program have comprised from 30% to 50% of the natural spawners, suggesting that the unaided stock is not able to maintain itself ( NWIFC 1997a). Almost all of the releases into this ESU have come from stocks within this ESU, with the majority of within ESU transfers coming from the Green River Hatchery or hatchery broodstocks that have been derived from Green River stock ( Marshall et al. 1995). The electrophoretic similarity between Green River fall run chinook salmon and several other fall run stocks in Puget Sound ( Marshall et al. 1995) suggests that there may have been a significant effect from some hatchery transplants. Overall, the pervasive use of Green River stock throughout much of the extensive hatchery network, that exists in this ESU, may reduce the genetic diversity and fitness of naturally spawning populations.

Harvest impacts on Puget Sound chinook salmon stocks have been quite high. Ocean exploitation rates on natural stocks average 56 59%; total exploitation rates average 68 83% ( 1982 89 brood years) ( PSC 1994). Total exploitation rates on some stocks have exceeded 90% ( PSC 1994). 227 Previous assessments of stocks within this ESU have identified several stocks as being at risk or of concern ( Appendix E). Nehlsen et al. ( 1991) identified four stocks as extinct, four stocks as possibly extinct, six stocks as at high risk of extinction, one stock as at moderate risk ( White River spring run), and 1 stock ( Puyallup River fall run) as of special concern. WDF et al. ( 1993) considered 28 stocks within the ESU, of which 13 were considered to be of native origin and predominantly natural production. The status of these 13 stocks was: 2 healthy ( Upper Skagit River summer run and Upper Sauk River spring run), 5 depressed, 2 critical ( South Fork Nooksack River spring/ summer run and Dungeness River spring/ summer run), and 4 unknown. The status of the remaining ( composite production) stocks was eight healthy, two depressed, two critical, and three unknown. The Nooksack/ Samish River fall run and Issaquah Creek summer/ fall run were not considered an ESA issue by the BRT ( stocks were not historically present in the watershed or current stocks are not representative of historical stocks) but were included to give a complete presentation of stocks identified by WDF et al. ( 1993).

Lower Columbia River Region The Lower Columbia River Region includes portions of the Coastal Range, Willamette Valley, and Cascades ecoregions ( see " Ecological Features," p. 12) and is characterized by numerous short and medium length rivers and streams draining the coast ranges and west slope of the Cascade Mountains, with a single large river ( Willamette River). We have no estimates of historic abundance of chinook salmon in this region. Peak cannery pack for the entire Columbia River Basin occurred in 1883, when 629,400 cases were packed, suggesting a total run size of about 4.6 million chinook salmon.

Chinook salmon in this region have been strongly affected by losses and alterations of freshwater habitats. Bottom et al. ( 1985), WDF et al. ( 1993), and Kostow ( 1995) provide reviews of habitat problems. Timber harvesting and associated road building occur throughout the region on federal, state, and private lands. These activities may increase sedimentation and debris flows and reduce cover and shade, resulting in aggradation, embedded spawning gravel, and increased water temperatures. Timber harvest in the Oregon portion of the region peaked in the 1930s, but habitat impacts remain ( Kostow 1995). Agriculture is also widespread in the lower portions of river basins, and has resulted in widespread removal of riparian vegetation, rerouting of streams, degradation of streambanks, and summer water withdrawals. Urban development has had substantial impacts in the lower Willamette Valley, including channelization and diking of rivers, filling and draining of wetlands, removal of riparian vegetation, and pollution ( Kostow 1995).

Intensive hatchery programs were initiated more than 100 years ago in this region. Nearly 4.5 billion hatchery derived fish have been released during the last 70 years, equal to the total for all the other regions combined ( Table 6, Appendix D). The majority of these have been " tule" fall run chinook salmon released into the lower Columbia River for fisheries enhancement. Because of the advanced degree of maturation that " tules" exhibit at the time of freshwater entry, 228 the economic value of these fish is rather low; therefore, efforts have been made to introduce Rogue River " bright" fall run chinook and upper Columbia River upriver " bright" fall run chinook into this region ( WDF et al. 1993, Kostow 1995, Marshall et al. 1995). In addition, fall run chinook salmon from the lower Columbia River were introduced into the upper Willamette River Basin beginning in the 1950s to exploit underutilized habitat.

9) Lower Columbia River ESU We have no estimates of historic abundance for this ESU, but there is widespread agreement that natural production has been substantially reduced over the last century. Currently, spawning escapement to populations on the Washington side of the Columbia River are monitored primarily by peak fish counts in index areas ( WDF et al. 1993). Peak index area spawning counts are expanded to estimate total spawning escapement. In most lower Columbia River tributaries in Oregon, foot surveys are conducted and escapement estimates are based on peak spawner counts or redd counts ( Theis and Melcher 1995), with dam counts available for the Sandy and Clackamas Rivers.

For fishery monitoring purposes, these individual spawning populations are combined into stock groupings: Lower Columbia River Wild, Lower Columbia River Hatchery, and Spring Creek Hatchery stocks of fall run chinook salmon designated for fishery management purposes( WDFW and ODFW 1994, PFMC 1996b).

The ESU also includes spring run chinook salmon in the Cowlitz, Lewis, Kalama, Sandy, and Clackamas Rivers. Estimates of spring runs to the mainstem Columbia River tributaries are routinely reported by fishery management agencies ( WDFW and ODFW 1994, PFMC 1996b), with the exception of the spring run to the Clackamas River. For fishery monitoring purposes, the Clackamas River spring run chinook salmon are included with the Willamette River. Cramer et al. ( 1996) reported escapement to the Clackamas River ( as hatchery returns), North Fork Dam counts, and spawners below the dam ( from Bennett 1994).

Recent abundance of spawners includes a 5 year geometric mean natural spawning escapement of 11,200 spring run fish ( 1992 96) ( Fig. 39, Appendix E). The fall run includes 29,000 natural spawners ( Fig. 39, Appendix E) and 37,000 hatchery spawners ( 1991 95), but according to the accounting of PFMC ( 1996b), approximately 68% of the natural spawners are first generation hatchery strays. Long term trends in escapement for the fall run are mixed, with most larger stocks positive, while the spring run trends are positive or stable ( Fig. 40, Appendix E). Short term trends for both runs are more negative.

All basins are affected ( to varying degrees) by habitat degradation. Major habitat problems are related primarily to blockages, forest practices, urbanization in the Portland and 229 230 231 Vancouver areas, and agriculture in floodplains and low gradient tributaries. Substantial chinook salmon spawning habitat has been blocked ( or passage substantially impaired) in the Cowlitz ( Mayfield Dam 1963, RKm 84), Lewis ( Merwin Dam 1931, RKm 31), Clackamas ( North Fork Dam 1958, RKm 50), Hood ( Powerdale Dam 1929, RKm 7), and Sandy ( Marmot Dam 1912, RKm 48; Bull Run River dams in the early 1900s) Rivers ( WDF et al. 1993, Kostow 1995).

Hatchery programs to enhance chinook salmon fisheries in the lower Columbia River began in the 1870s, expanded rapidly, and have continued throughout this century. Although the majority of the stocks have come from within this ESU, over 200 million fish from outside the ESU have been released since 1930 ( Table 6, Appendix D). A particular concern at the present time is straying by Rogue River fall run chinook salmon, which are released into the lower Columbia River to augment harvest opportunities. Available evidence indicates a pervasive influence of hatchery fish on natural populations throughout this ESU, including both spring and fall run populations ( Howell et al. 1985, Marshall et al. 1995). In addition, the exchange of eggs between hatcheries in this ESU has led to the extensive genetic homogenization of hatchery stocks ( Utter et al. 1989).

Harvest rates on fall run stocks are moderately high, with an average total exploitation rate of 65% ( 1982 89 brood years) ( PSC 1994). The average ocean exploitation rate for this period was 46%, while the freshwater harvest rate on the fall run has averaged 20%, ranging from 30% in 1991 to 2.4% in 1994. Harvest rates are somewhat lower for spring run stocks, with estimates for the Lewis River averaging 24% ocean and 50% total exploitation rates in 1982 89 ( PSC 1994). Inriver fisheries harvest approximately 15% of the lower river hatchery stock, 29% of the lower river wild stock, and 58% of the Spring Creek hatchery stock ( PFMC 1996b). The average inriver exploitation rate on the stock as a whole is 29% ( 1991 95).

Previous assessments of stocks within this ESU have identified several stocks as being at risk or of concern ( Appendix E). Nehlsen et al. ( 1991) identified two stocks as extinct ( Lewis River spring run and Wind River fall run), four stocks as possibly extinct, and four stocks as at high risk of extinction. The Sandy River spring run and Hood River spring and fall runs were not considered an ESA issue by the BRT ( stocks were not historically present in the watershed or current stocks are not representative of historical stocks) but were included to give a complete presentation of stocks identified by Nehlsen et al. ( 1991). WDF et al. ( 1993) considered 20 stocks within the ESU, of which only 2 were considered to be of native origin and predominantly natural production ( Lewis River and East Fork Lewis River fall runs). Nehlsen et al. considered the status of these two stocks to be healthy, and the status of the remaining ( not native/ natural) stocks as: 14 healthy and 4 depressed. Huntington et al. ( 1996) identified one healthy Level I stock in their survey ( Lewis River fall run).

10) Upper Willamette River ESU 232 The spring run has been counted at Willamette Falls since 1946 ( ODFW and WDFW 1995) but, counts were not differentiated into adults and jacks until 1952. In the first 5 years ( 1946 50), the geometric mean of the counts for adults and jacks combined was 31,000 fish. The most recent 5 year ( 1992 96) geometric mean escapement above Willamette Falls was 26,000 adults ( Appendix E). Willamette River spring run chinook salmon are targeted by commercial and recreational fisheries in the lower Willamette and Columbia Rivers. During the same 5 year period, the geometric mean of the run size to the mouth of the Columbia River was 48,000 fish ( PFMC 1997). The majority of the Willamette River fish are hatchery produced.

Estimates of the naturally produced run have been made only for the McKenzie River in 1994 and 1995 ( Nicholas 1995). Nicholas ( 1995) estimated the escapement of naturally produced spring run chinook salmon in the McKenzie River to be approximately 1,000 spawners. Primarily on the basis of professional judgement, they estimated the 1994 95 natural escapement of springrun chinook salmon to the entire ESU as approximately 7,700 spawners, with 2,100 to 3,500 naturally produced natural spawners. However, Nicholas ( 1995) included the Sandy and Clackamas Rivers in their Willamette River spring run chinook salmon unit; the BRT does not consider these introduced populations to be part of the ESU. Without these 2 rivers, the remaining escapement was approximately 3,900 natural spawners, with approximately 1,300 of these spawners naturally produced ( Fig. 39, Appendix E). Long term trends of escapement are mixed, ranging from slightly upward to moderately downward ( Fig. 40, Appendix E). Short term trends are all strongly downward.

Although the abundance of Willamette River spring run chinook salmon has been relatively stable over the long term, and there is evidence some of natural production, it is apparent that at present production and harvest levels the natural population is not replacing itself. With natural production accounting for only one third of the natural spawning escapement, it is questionable whether natural spawners would be capable of replacing themselves even in the absence of fisheries. Although hatchery programs in the Willamette River Basin have maintained broodlines that are relatively free of genetic influences from outside the basin, they may have homogenized the population structure within the ESU. Prolonged artificial propagation of the majority of the production from this ESU may also have had deleterious effects on the ability of Willamette River spring run chinook salmon to reproduce successfully in the wild.

Habitat blockage and degradation are significant problems in this ESU. Available habitat has been reduced by construction of dams in the Santiam, McKenzie, and Middle Fork Willamette River Basins, and these dams have probably adversely affected remaining production via thermal effects. Agricultural development and urbanization are the main causes of serious habitat degradation throughout the basin ( Bottom et al. 1985, Kostow 1995).

Historically, only spring run fish were able to ascend Willamette Falls to access the upper Willamette River ( Fulton 1968). Following improvements in the fish ladder at Willamette Falls, some 200 million fall run chinook salmon have been introduced into this ESU since the 1950s. In contrast, the upper Willamette River has received relatively few introductions of non native 233 spring run fish from outside this ESU ( Table 6, Appendix D). Artificial propagation efforts have been undertaken by a limited number of large facilities ( McKenzie, Marion Forks, South Santiam, and Willamette [ Dexter] Fish Hatcheries). These hatcheries have exchanged millions of eggs from various populations in the upper Willamette River Basin. The result of these transfers has been the loss of local genetic diversity and the formation of a single breeding unit in the Willamette River Basin ( Kostow 1995). Considerable numbers of hatchery spring run strays have been recovered from natural spawning grounds, and an estimated two thirds of natural spawners are of hatchery origin ( Nicholas 1995). There is also evidence that introduced fall run chinook salmon have successfully spawned in the upper Willamette River ( Howell et al 1985). Whether hybridization has occurred between native spring run and introduced fall run fish is not known.