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

NOAA-NMFS-NWFSC TM-33: Sockeye Salmon Status Review (1997)

EXECUTIVE SUMMARY

The Endangered Species Act (ESA) allows listing of "distinct population segments" of vertebrates as well as named species and subspecies. The policy of the National Marine Fisheries Service (NMFS) on this issue for Pacific salmon and other anadromous salmonids is that a population will be considered "distinct" for purposes of the ESA if it represents an Evolutionarily Significant Unit (ESU) of the species as a whole. To be considered an ESU, a population or group of populations must 1) be substantially reproductively isolated from other populations, and 2) contribute substantially to ecological/genetic diversity of the biological species. Once an ESU is identified, a variety of factors related to population abundance are considered in determining whether a listing is warranted.

In September 1994, in response to a petition seeking protection for Baker Lake (Washington) sockeye salmon under the ESA, NMFS initiated a coastwide status review of sockeye salmon (Oncorhynchus nerka) (Walbaum, 1792) in Washington, Oregon, and California, and formed a Biological Review Team (BRT) to conduct the review. This report summarizes biological and environmental information gathered in that process.

West Coast Sockeye Salmon ESUs

The BRT examined genetic, life history, biogeographic, geologic, and environmental information in the process of identifying ESUs. In particular, genetic data; physical, chemical, and biological characteristics of nursery lakes; sockeye salmon river entry and spawn timing; and smolt outmigration timing were found to be most informative for this process. Based on this examination, the BRT identified six sockeye salmon ESUs and one provisional ESU in Washington, as follows:

1) Okanogan River

This ESU is named after the Okanogan River in the Columbia River drainage of Washington and includes all sockeye salmon that spawn in areas upstream from Lake Osoyoos, in Lake Osoyoos, or the downstream tributary Similkameen River (below Enloe Dam). The spawning and main rearing area for this ESU is in British Columbia, while the migration corridor for both juveniles and adults is through the Columbia River in Washington and Oregon. Important factors that differentiate this population as a separate ESU include: 1) the use of a very eutrophic lake-rearing environment (Lake Osoyoos), which is unusual for sockeye salmon, 2) the tendency for a relatively large percentage of the Okanogan River sockeye salmon population to return as 3-year-olds (age 1.1), 3) the juvenile outmigration-timing differences between Okanogan River and Lake Wenatchee-origin fish, 4) the adaptation of Okanogan River sockeye salmon to much higher temperatures during adult migration in the Okanogan River, and 5) protein electrophoretic data that indicate that this population is genetically distinct from other sockeye salmon currently in the Columbia River drainage. If "kokanee-sized" O. nerka observed spawning with sockeye salmon in the Okanogan River are identified as residual or resident sockeye salmon, then they are to be considered as part of the Okanogan River sockeye salmon ESU.

2) Lake Wenatchee

This ESU is named after Lake Wenatchee on the Wenatchee River in the Columbia River drainage of Washington and includes all sockeye salmon that spawn above or in Lake Wenatchee and rear in Lake Wenatchee. Important factors that distinguish this ESU include electrophoretic data that indicate this population is genetically the second most distinctive population (after Redfish Lake, ID) within the contiguous United States, and life history and environmental differences with sockeye salmon from the Okanogan River ESU (juvenile outmigration timing, environmental differences in lake-rearing habitat, and age composition). If "kokanee-sized" O. nerka observed spawning with sockeye salmon in Lake Wenatchee tributaries are identified as residual or resident sockeye salmon, then they are to be considered as part of the Lake Wenatchee sockeye salmon ESU.

3) Quinault Lake

This ESU is named after Quinault Lake on the Olympic Peninsula of Washington and includes all sockeye salmon that spawn in the Quinault River drainage and rear in Quinault Lake. Early river-entry timing, protracted adult run timing, extended lake residence prior to spawning, unusually lengthy spawn timing, unusual skin pigmentation of spawners, and genetic differences from other coastal Washington sockeye salmon are important factors in identifying this ESU.

4) Ozette Lake

This ESU is named after Ozette Lake on the Olympic Peninsula of Washington and includes all sockeye salmon that spawn in the Ozette River drainage and rear in Ozette Lake. Important factors that distinguish this ESU include electrophoretic data that indicate this population is genetically distinct from all other sockeye salmon stocks in the Northwest, early river-entry timing, and the relatively large adult body size and large average smolt size of sockeye salmon in Ozette Lake compared to other coastal Washington sockeye salmon populations. If "kokanee-sized" O. nerka observed spawning with sockeye salmon in Ozette Lake are identified as residual or resident sockeye salmon, then they are to be considered as part of the Ozette Lake sockeye salmon ESU.

5) Baker River

This ESU is named after the Baker River in the Skagit River drainage in northern Puget Sound, Washington and includes sockeye salmon that return to the Baker River. Important factors that distinguish this ESU include electrophoretic data that indicate that Baker River sockeye salmon are genetically distinct from sockeye salmon populations from the lower Fraser River and from other localities in Washington, the limnology of old Baker Lake (typically cold, oligotrophic, well-oxygenated, and influenced by glacial runoff, in contrast to other sockeye salmon systems under review with the exception of Lake Wenatchee), and the very large average smolt size of sockeye salmon in Baker Lake compared to other Washington sockeye salmon populations.

6) Lake Pleasant

This ESU is named after Lake Pleasant on the Olympic Peninsula of Washington and includes sockeye salmon that ascend the Quillayute and Sol Duc Rivers and Lake Creek to spawn in Lake Pleasant. Important factors that differentiate this population as a separate ESU include: 1) protein electrophoretic data that indicate that this population is genetically distinct from other Washington sockeye salmon populations, 2) the distinctive small body size of adult spawners, and 3) the unusual age structure of the population, with significant numbers of juveniles remaining for 2 years in freshwater and/or spending only 1 year at sea. If "kokanee-sized" O. nerka observed spawning with sockeye salmon in Lake Pleasant are identified as residual or resident sockeye salmon, then they are to be considered as part of the Lake Pleasant sockeye salmon ESU.

Big Bear Creek

The Big Bear Creek provisional ESU is named after a tributary of the Sammamish River in the Lake Washington/Lake Sammamish Basin and includes sockeye salmon that spawn in Big Bear Creek and its two tributaries, Cottage Lake Creek and Evans Creek. Genetically, sockeye salmon from Big Bear and Cottage Lake Creeks are distinct from other stocks of sockeye salmon in the Lake Washington/Lake Sammamish drainage. A great deal of uncertainty remains concerning the historical presence of sockeye salmon within the Lake Washington/Lake Sammamish drainage prior to sockeye salmon transplants, which occurred in the 1930s-1950s. The relationship of this stock to native and transplanted kokanee is also uncertain, although genetically it is unlike the current parent stock from which these kokanee transplants originated (Lake Whatcom). If "kokanee-sized" O. nerka observed spawning with sockeye salmon in Big Bear Creek are identified as residual or resident sockeye salmon they are to be considered as part of the provisional Big Bear Creek sockeye salmon ESU.

Other Population Units

Historical records, stocking history, and genetic data indicate that sockeye salmon that spawn in the Cedar River, Issaquah Creek, and on lakeshore beaches in Lake Washington in the Lake Washington Basin and in the Methow and Entiat Rivers in the Columbia River Basin originated from transplants from outside these basins. Therefore, the BRT concluded that these populations are not presently considered as ESUs or as part of any other ESUs and are therefore not an ESA issue. The ESU status of two other population units could not be determined due to a lack of biological and historical information. These units are classified as follows:

1) Riverine-spawning sockeye salmon

This population unit consists of multiple aggregations of small numbers of sockeye salmon that spawn in Washington rivers without lake-rearing habitat. Although genetic data were available for riverine spawners in the Nooksack, Skagit, and Sauk Rivers, the data were insufficient to eliminate the possibility that these sockeye salmon may be derived from recent or historical straying of British Columbia lake-type or sea/river-type sockeye salmon. Genetic data were unavailable for riverine spawners in other Washington rivers on the west side of the Cascade Mountains. The BRT concluded that insufficient information exists concerning riverine-spawning sockeye salmon to make a decision as to this group's ESU status.

2) Deschutes River, Oregon

This population unit consists of sockeye salmon that are observed at the base of Pelton Re-regulating Dam on Oregon's Deschutes River, a tributary of the lower Columbia River. The BRT concluded that sockeye salmon that historically migrated up the Deschutes River via the Columbia River to spawn in Suttle Lake were a separate ESU, but due to lack of genetic and life-history information, it is uncertain whether remnants of this ESU exist.

Assessment of Extinction Risk

The 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." According to the ESA, the determination 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, the BRT did not evaluate likely or possible effects of conservation measures, and therefore did not make recommendations as to whether identified ESUs should be listed as threatened or endangered species; rather, the BRT drew scientific conclusions about the risk of extinction faced by identified ESUs under the assumption that present conditions will continue.

The BRT concluded that five sockeye salmon ESUs (Okanogan River, Lake Wenatchee, Quinault Lake, Baker River, Lake Pleasant) and one provisional ESU (Big Bear Creek) are not in danger of extinction, nor are they likely to become so in the foreseeable future. The BRT also concluded that one sockeye salmon ESU (Ozette Lake), although not presently in danger of extinction, is likely to become so if present conditions continue into the foreseeable future. Information used by the BRT in coming to these conclusions follow for each ESU.

1) Okanogan River

Major concerns regarding health of this ESU were the channelization of spawning habitat in Canada, the summer high water-temperatures that periodically block migration in the lower Okanogan River, and effects of hydropower development in the Columbia River. The run-size for this ESU has been highly variable over time, with recent 5-year average annual escapement at about 11,000. Recent (1986-1995) abundance, as demonstrated by the abundance trend, has declined at about 2-20% per year. This is heavily influenced by high abundance in 1985 and low abundance in 1990, 1994, and 1995. Although the BRT concluded that sockeye salmon in this ESU are not in danger of extinction, nor are they likely to become so in the foreseeable future, they had several concerns about the overall health of this ESU and they concluded that the status of this ESU bears close monitoring.

2) Lake Wenatchee

There was unanimous agreement among the BRT that sockeye salmon in this ESU are not in danger of extinction and are not likely to become endangered in the foreseeable future if present trends continue. Despite this conclusion, the BRT had concerns about the overall health of this ESU, including the effects of hydropower development in the Columbia River and the effects of hatchery production and potential interbreeding with non-native kokanee on genetic integrity of the unit. Although production is apparently limited by the oligotrophic conditions in Lake Wenatchee, habitat conditions are generally considered good in this basin. The recent 5-year average annual escapement for this ESU was about 19,000 adult sockeye salmon, and recent (1986-1995) abundance has been declining by about 10% per year, with years of very low abundance in 1994 and 1995. The long-term (1961-1996) abundance trend for this ESU is flat.

3) Quinault Lake

The BRT concluded that sockeye salmon in this ESU are not in danger of extinction, nor are they likely to become endangered in the future if present trends continue. Despite this conclusion, the BRT was concerned that this ESU is presently near the lower end of its historical abundance range. This condition may be largely attributed to severe habitat degradation in the upper Quinault River that contributes to poor spawning habitat quality and possibly impacts juvenile rearing conditions in Quinault Lake. Recent (1991-1995) 5-year average annual escapement was about 32,000 sockeye salmon for this ESU. While abundance data from 1967-1995 show an increase of about 1% per year, the period from 1986-1995 shows a decrease in abundance of about 3% per year. Recent escapement is probably near the low end of historical abundance for this ESU; historical escapement estimates ranged from 20,000 to 250,000 in the 1920s, while run sizes in the early 1900s ranged from 50,000 to 500,000.


4) Ozette Lake

Major concerns that led the BRT to conclude that if present conditions continue into the future, Ozette Lake sockeye salmon are likely to become in danger of extinction in the foreseeable future include: siltation of beach spawning habitat, very low abundance compared to harvest in the 1950s, overall downward trend in abundance coupled with large fluctuations in abundance, and potential genetic effects of ongoing hatchery production and past practices of sockeye salmon being interbred with genetically dissimilar kokanee. Current escapements average below 1,000 adults per year, with little room for further declines before abundances would be critically low. The most recent (1992-1996) 5-year average annual escapement (based on weir counts) for this ESU was 700 adults, while historical run-size estimates range from a few thousand sockeye salmon in the mid-1920s to a peak recorded harvest of about 18,000 in the late 1940s. Abundance decreased by about 3% per year from 1977-1995 and by about 10% per year between 1986-1995.

5) Baker River

Despite the BRT's conclusion that the Baker River sockeye salmon ESU is not presently in danger of extinction, nor likely to become so in the foreseeable future, the BRT had several concerns about the overall health of this ESU that indicate that the ESU bears close monitoring. It is likely that this stock would become extinct if present human intervention (trap, haul, and spawning beach activities) were suspended. In addition, the BRT felt this ESU bears close monitoring due to proposed changes in management (confining spawners to a single artificial spawning beach) that could substantially increase risk to the population. Recent (1990-1994) average annual escapement for this ESU was about 2,700 adult sockeye salmon compared to historical pre-dam estimates of escapement averaging 20,000 fish near the turn of the century; however, other data indicates that this 20,000 figure is a peak value and that the average may have been substantially less than 20,000. Although sockeye salmon escapement in 1994 (about 16,000) was near the historic pre-dam maximum, recent average abundance is probably near the lower end of the historical abundance range for this ESU. Although stock abundance has fluctuated considerably over time, long-term abundance (1926-1995) has decreased by about 2% per year, while recent abundance (1986-1995) has increased at about 32% per year.

6) Lake Pleasant

At the time the BRT met, little information was available concerning recent escapement levels, and the majority of the BRT felt that there was insufficient information to adequately assess extinction risk for the Lake Pleasant ESU. However, a minority concluded that the ESU is not presently in danger of extinction nor likely to become so in the foreseeable future. Spawning ground peak counts from the late 1980s (and data received for the 1990s, subsequent to the BRT meeting) appear roughly comparable to habitat capacity for this small lake. Weir counts in the early 1960s ranged from 763 to 1,485 fish. Recently received spawner survey data (unavailable at the time of the BRT meeting) for the years 1987 to 1996 ranged from highs above 2,000 in 1987 and 1992 to a low of 90 in 1991 (a year with limited sampling). The BRT expressed concerns regarding potential urbanization of habitat and effects of sport harvest during the migration delay in the Sol Duc River.

Big Bear Creek

Relatively high recent average escapement levels between 10,000 and 20,000 spawners led a majority of the BRT to conclude that the Big Bear Creek sockeye salmon provisional ESU is not presently in danger of extinction, nor is it likely to become endangered in the foreseeable future if present conditions continue. A minority of the BRT felt that information was insufficient to adequately assess extinction risk in this ESU. However, several factors led to a second minority opinion that this provisional ESU is likely to become endangered in the foreseeable future. These factors included extreme fluctuations in recent abundances and potential effects of urbanization in the watershed. Recent development of a county growth-management plan was seen by the BRT as a possible benefit to freshwater habitat for this population. The BRT felt that the status of this population bears close monitoring. Recent escapements have ranged from a high of 39,700 in 1994 to a low of 1,800 in 1989. The most recent (1991-1995) 5-year average annual escapement for this provisional ESU was 11,400 adults. Abundance decreased by about 7% per year from 1982-1995 and by about 4% per year between 1986-1995.

Consideration was also given to the condition of the two population units for which ESU status has not been determined. There was insufficient information available to assess the risk of extinction for riverine-spawning sockeye salmon. The BRT concluded that the final population unit (Deschutes River, Oregon sockeye salmon) is clearly in danger of extinction if not already extinct.

ACKNOWLEDGMENTS

The status review for west coast sockeye salmon was conducted by a team of researchers from the National Marine Fisheries Service's (NMFS) Northwest Fisheries Science Center (NWFSC). This biological review team (BRT; technical terms and abbreviations such as "BRT" are defined in Appendix A) relied on the West Coast Sockeye Salmon Administrative Record, which was developed pursuant to this review and is comprised of comments and informational reports submitted by the public and by state, tribal, and federal agencies. The authors acknowledge the efforts of all who contributed to this record, especially the Washington Department of Fish and Wildlife, the Northwest Indian Fisheries Commission, the Quinault Indian Nation, the Makah Tribe, the Quileute Indian Tribe, Oregon Department of Fish and Wildlife, and U.S. Fish and Wildlife Service, and Olympic National Park.

Numerous fishery scientists and managers provided information that aided in preparation of this document and deserve special thanks. These include Jim Ames, Don Hendrick, Larrie LaVoy, Dr. James Shaklee, John Sneva, Gary Sprague, and Sewall Young of the Washington Department of Fish and Wildlife; Dr. Chris Wood and Dr. Kim Hyatt of the Canadian Department of Fisheries and Oceans; Kevin Craig, Dr. Chris Foote, Andrew Hendry, and Dr. Tom Quinn of the University of Washington; Dr. Ernest L. Brannon of the University of Idaho; Dr. Jeffrey K. Freyer of the Columbia River Inter-tribal Fish Commission; Gary Graves and Keith Lutz of the Northwest Indian Fisheries Commission; Eric Warner of the Muckleshoot Indian Tribe, Fisheries Department; Del Boyer Jr. and Scott Chitwood of the Quinault Fisheries Division; Jeff Haymes of Quileute Natural Resources; Ned Currence and Denise Dailey of Makah Fisheries Management; and Kathryn Kostow and John Leppink of Oregon Department of Fish and Wildlife.

The biological review team for this status review included: Thomas Flagg, Dr. Stephen Grabowski, Dr. Richard Gustafson, Dr. Robert Iwamoto, Dr. Conrad Mahnken, Gene Matthews, Dr. Michael Schiewe, Dr. Thomas Wainwright, Dr. Robin Waples, Laurie Weitkamp, Dr. John Williams, and Dr. Gary Winans, all from the NWFSC.

INTRODUCTION

Sockeye salmon, Oncorhynchus nerka (Walbaum, 1792) (locally called blueback salmon in the Columbia and Quinault Rivers, red salmon in Alaska, krasnaya ryba or nerka in Russia, and benimasu or benizake in Japan), occur in North America around the Pacific Rim from the Columbia River in the south to the Nome River (and perhaps the Noatak River), Alaska in the north. In Asia, this species ranges from Hokkaido, Japan, the Kuril and Komandorskiy Islands, and the northwest coast of the Sea of Okhotsk in the south to the Anadyr River in the north (Atkinson et al. 1967, Foerster 1968, Burgner 1991, Forrester 1987). Recent publications (Konkel and McIntyre 1987, Nehlsen et al. 1991, Wilderness Society 1993) reported that a number of local populations of sockeye salmon in Washington, Idaho, and Oregon have become extinct, and the abundance of many others is depressed. The U.S. Endangered Species Act (ESA) is intended to conserve threatened and endangered species in their native habitats. Under the ESA, the term "species" is defined rather broadly to include subspecies as "distinct population segments" of vertebrates (such as salmon) as well as taxonomic species.

On 14 March 1994, the National Marine Fisheries Service (NMFS) was petitioned by the Professional Resources Organization-Salmon (PRO-Salmon) to list Baker River sockeye salmon as a threatened or endangered species under the ESA (PRO-Salmon 1994). At about the same time, NMFS also received petitions for numerous other populations of Pacific salmon in the Puget Sound area. In response to these petitions, and to the more general concerns for the status of Pacific salmon throughout the region, NMFS (1994) announced that it would initiate ESA status reviews for all species of anadromous salmonids in the Pacific Northwest. These comprehensive reviews include all populations in the states of Washington, Idaho, Oregon, and California. This proactive approach should facilitate more timely, consistent, and comprehensive evaluation of the ESA status of Pacific salmonids than would be possible through a long series of reviews of individual populations.

Scope and Intent of the Present Document

This document reports results of the comprehensive ESA status review of sockeye salmon from Washington and Oregon (Fig. 1). Presently, there are no known sockeye salmon populations in California, and a previous review (Waples et al. 1991) considered the ESA status of sockeye salmon from Idaho. To provide a context for evaluating U.S. populations of sockeye salmon, biological and ecological information for populations of sockeye salmon in British Columbia was also considered (Fig. 2, Table 1). This review thus encompasses, but is not restricted to, the single population identified in the PRO-Salmon petition.

Because the ESA stipulates that listing determinations should be made on the basis of the best scientific information available, NMFS formed a team of scientists with diverse backgrounds in salmon biology to conduct this review. This Biological Review Team (BRT)1 discussed and evaluated scientific information presented at public meetings and also reviewed information submitted to the ESA administrative record for west coast sockeye salmon.

Key Questions in ESA Evaluations

An ESA status review involves answering two key questions: 1) Is the entity in question a "species" as defined by the ESA? and 2) If so, is the "species" in danger of extinction or likely to become so? These two questions are addressed in separate sections in the text that follows. If it is determined that a listing(s) is warranted, then NMFS is required by law (1973 ESA Sec. 4(a)(1)) to identify one or more of the following factors responsible for the species' threatened or endangered status: 1) destruction or modification of habitat; 2) over-utilization by humans; 3) disease or predation; 4) inadequacy of existing regulatory mechanisms; or 5) other natural or human factors. This status review does not formally address factors for decline, except insofar as they provide information about the degree of risk faced by the species in the future.

The "Species" Question

As amended in 1978, the ESA allows listing of "distinct population segments" of vertebrates as well as named species and subspecies. However, the ESA provides no specific guidance for determining what constitutes a distinct population, and the resulting ambiguity has led to the use of a variety of criteria in listing decisions over the past decade. To clarify the issue for Pacific salmon, NMFS published a policy describing how the agency will apply the definition of "species" in the ESA to anadromous salmonid species, including sea­run cutthroat trout and steelhead (NMFS 1991). A more detailed discussion of this topic appeared in the NMFS "Definition of Species" paper (Waples 1991a). The NMFS policy stipulates that a salmon population (or group of populations) will be considered "distinct" for purposes of the ESA if it represents an evolutionarily significant unit (ESU) of the biological species. An ESU is defined as a population that 1) is substantially reproductively isolated from conspecific populations and 2) represents an important component of the evolutionary legacy of the species.

The term "evolutionary legacy" is used in the sense of "inheritance"--that is, something received from the past and carried forward into the future. Specifically, the evolutionary legacy of a species is the genetic variability that is a product of past evolutionary events and that represents the reservoir upon which future evolutionary potential depends. Conservation of these genetic resources should help to ensure that the dynamic process of evolution will not be unduly constrained in the future.

The NMFS policy identifies a number of types of evidence that should be considered in the species determination. For each of the criteria, the NMFS policy advocates a holistic approach that considers all types of available information as well as their strengths and limitations. Isolation does not have to be absolute, but it must be strong enough to permit evolutionarily important differences to accrue in different population units. Important types of information to consider include natural rates of straying and recolonization, evaluations of the efficacy of natural barriers, and measurements of genetic differences between populations. Data from protein electrophoresis or DNA analyses can be particularly useful for this criterion because they reflect levels of gene flow that have occurred over evolutionary time scales.

The key question with respect to the second criterion is: If the population became extinct, would this represent a significant loss to the ecological/genetic diversity of the species? Again, a variety of types of information should be considered. Phenotypic and life history traits such as size, fecundity, migration patterns, and age and time of spawning may reflect local adaptations of evolutionary importance, but interpretation of these traits is complicated by their sensitivity to environmental conditions. Data from protein electrophoresis or DNA analysis provide valuable insight into the process of genetic differentiation among populations but little direct information regarding the extent of adaptive genetic differences. Habitat differences suggest the possibility for local adaptations but do not prove that such adaptations exist.

The "Extinction Risk" Question

The 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 spawner­recruit ratios; 4) natural and human­influenced 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 short­term 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 do 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 Regional Office in making listing recommendations.

Artificial Propagation

NMFS policy (Hard et al. 1992, NMFS 1993) stipulates that in determining 1) whether a population is distinct for purposes of the ESA, and 2) whether an ESA species is threatened or endangered, attention should focus on "natural" fish, which are defined as the progeny of naturally spawning fish (Waples 1991a). This approach directs attention to fish that spend their entire life cycle in natural habitat and is consistent with the mandate of the ESA to conserve threatened and endangered species in their native ecosystems. Implicit in this approach is the recognition that fish hatcheries are not a substitute for natural ecosystems.

Nevertheless, artificial propagation is important to consider in ESA evaluations of anadromous Pacific salmonids for several reasons. First, although natural fish are the focus of ESU determinations, possible effects of artificial propagation on natural populations must also be evaluated. For example, stock transfers might change the genetic or life-history characteristics of a natural population in such a way that the population might seem either less or more distinctive than it was historically. Artificial propagation can also alter life-history characteristics such as smolt age and size and migration and spawn timing.

Second, artificial propagation poses a number of risks to natural populations that may affect their risk of extinction or endangerment. These risks are discussed below in the "Assessment of Extinction Risk" section. In contrast to most other types of risk for salmon populations, those arising from artificial propagation are often not reflected in traditional indices of population abundance. For example, to the extent that habitat degradation, overharvest, or hydropower development have contributed to a population's decline, these factors will already be reflected in population abundance data and accounted for in the risk analysis. The same is not true of artificial propagation. Hatchery production may mask declines in natural populations that will be missed if only raw population abundance data are considered. Therefore, a true assessment of the viability of natural populations cannot be attained without information about the contribution of naturally spawning hatchery fish. Furthermore, even if such data are available, they will not in themselves provide direct information about possibly deleterious effects of fish culture. Such an evaluation requires consideration of the genetic and demographic risks of artificial propagation for natural populations. The sections on artificial propagation in this report are intended to address these concerns.

Finally, if any natural populations are listed under the ESA, then it will be necessary to determine the ESA status of all associated hatchery populations. This latter determination would be made following a proposed listing and is not considered in this document.

Summary of Information Presented by the Petitioners

The single sockeye salmon population petitioned by PRO-Salmon (1994), Baker River, was characterized as "critical" by WDF et al. (1993). With respect to the two criteria established by NMFS to define a "species" of sockeye salmon in the context of the ESA, the petitioner argued that the Baker River population of sockeye salmon is the only significant remaining population of sockeye salmon in Puget Sound, with the exception of Lake Washington/Lake Sammamish populations. The petitioners argued that Lake Washington/Lake Sammamish populations originated from transplants of Baker River stock. Reproductive isolation was inferred primarily on the basis of geographic separation from other sockeye salmon populations. Other observations of sockeye salmon spawning in the Skagit River drainage were postulated to represent Baker River strays or perhaps small river-type populations. The Washington State Salmon and Steelhead Stock Inventory (SASSI) cited NMFS unpublished genetic data, which is based on protein electrophoresis, and which shows that the Baker River stock is significantly different from all other Washington sockeye salmon stocks (WDF et al. 1993). In its petition, PRO-Salmon provided little information that addresses the criterion of "evolutionary significance." The petitioner argued that since there are few records of introductions of sockeye salmon into this population, and it is separated geographically from other populations, it should be considered an ESU.

The petitioner identified several threats to viability of Baker River sockeye salmon. Access to native spawning habitat is obstructed by two dams, Lower and Upper Baker Dams. Beginning in 1924, adult sockeye salmon returning to the Baker River were trapped and lifted over Lower Baker Dam and released in Lake Shannon to continue their migration to Baker Lake. Native beach-spawning habitat in Baker Lake was eliminated when Upper Baker Dam was constructed in 1959, inundating the original Baker Lake and forming Upper Baker Reservoir, which continues to be called Baker Lake. Since 1958, most adult sockeye salmon returning to the Baker River have been trapped at the barrier dam and fish trap below Lower Baker Dam and hauled by tanker truck to one of several artificial spawning beaches (ponds designed to simulate natural beach spawning habitat).

Major concerns of the petitioners included: 1) Puget Sound Power and Light Company's plans to curtail operation of artificial spawning beaches 2 and 3 and confine sockeye salmon spawning to a single beach (beach 4), 2) the potential for recurrence of the intrusion of silt and sand into the intake water source for spawning beach 4, which has caused siltation of spawning gravels, and 3) the potential for recurrence of the disease, infectious hematopoietic necrosis (IHN), in sockeye salmon confined to spawning beach 4. The water intake on Sulfur Creek for artificial spawning beach 4 is located at the base of a steep, unstable slope, and the petitioners were concerned that intrusion of fine sand present at the intake could trigger the turbidity meter (installed following intrusion of sand and mud into beach 4 in 1990-1991) to cut off the supply of fresh water to the spawning gravel. The petitioners were most concerned that a system to recirculate the water within spawning beach 4, in the event of an intake water shutdown, has not been installed.

The petitioners pointed out that mixed stock fisheries targeting early Fraser River stocks may harvest some Baker River sockeye salmon. The petitioners also suggested that juvenile sockeye salmon are likely taken in the spring recreational kokanee fishery that operates in this reservoir, since the range of fork lengths of 1-year-old sockeye salmon smolts in Baker Lake (up to 200 mm, average of 149 mm) overlaps the minimum retention size (152 mm) for kokanee. Two-year-old sockeye salmon smolts, though rare in Baker Lake, are all longer than 200 mm. In addition, the petitioners pointed out that in years when shore and lower tributary spawning of wild sockeye salmon is allowed to occur in Baker Lake (extensive wild spawning occurred in 1994), the late-fall and winter reservoir drawdowns leave many sockeye salmon redds dewatered (PRO-Salmon 1994).


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