U.S. Dept Commerce/NOAA/NMFS/NWFSC/Publications
NOAA-NMFS-NWFSC TM-33: Sockeye Salmon Status Review (cont)
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As outlined previously in the "Introduction,"
NMFS considers a variety of information in evaluating the level
of risk facing an ESU. Aspects of several of these risk considerations
are common to all sockeye salmon ESUs. These are discussed in
general below; more specific discussion of factors for each of
the ESUs under consideration here can be found in the following
sections. Because we have not taken future effects of conservation
measures into account (see "Introduction"), we have
drawn scientific conclusions about the risk of extinction faced
by identified ESUs under the assumption that present conditions
will continue. Future effects of conservation measures will be
taken into account by the NMFS Northwest Regional Office in making
listing recommendations.
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) (see 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 lake or
river basins and at the scale of spawning areas within basins
("metapopulation" structure). Temporal distribution
is important both among years, as an indicator of the relative
health of different brood-year lineages, and within seasons, as
an indicator of the relative abundance of different life-history
types or runs.
Traditionally, assessment of salmonid
populations has focused on the number of harvestable 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, in this review
we attempted to distinguish natural fish from hatchery-produced
fish. 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. 14): "Hatchery produced" fish are reared as juveniles
in a hatchery but return as adults to spawn naturally; "Natural"
fish are progeny of naturally spawning fish.
The relationship of current abundance
and habitat capacity to that which existed historically is an
important consideration in evaluating risk for several reasons.
Knowledge of historical population conditions provides a perspective
of the conditions under which present stocks evolved. Historical
abundance also provides the basis for establishing long-term trends
in populations. Comparison of present and past habitat capacity
can also indicate long-term population trends and problems of
population fragmentation.
Although the relationship of present abundance
to present carrying capacity is important for understanding the
health of populations, the fact that a population is near its
current capacity does not in itself mean that it is healthy.
If a population is near capacity, there will be limits to the
effectiveness of short-term management actions in increasing abundance,
and competition and other interactions between hatchery and natural
fish may be an important consideration because hatchery fish will
further increase population density in a limited habitat.
All populations of sockeye salmon in this region have been affected by substantial loss and degradation of freshwater habitat, although the causes vary among populations. Much of the original sockeye salmon habitat in the Columbia River Basin has been blocked by irrigation diversions, hydroelectric development, and other human actions: accessible nursery lake habitat in the upper Columbia River is now only 4% (by surface area) of historical habitat, and only one remnant population remains in the Snake River (Mullan 1986, TAC 1991, Fryer 1995). This has resulted in widespread extinctions of populations that formerly occupied these areas. Coastal populations have also been affected by a variety of habitat factors, particularly hydroelectric development (Baker River) and forest management practices.
Short- and long-term trends in abundance
are a primary indicator of risk in salmonid populations. Trends
may be calculated from a variety of quantitative data, including
dam or weir counts, stream surveys, and catch
data. These data sources and methods are discussed in more detail
below (see "Approach").
The important role of artificial propagation
(in the form of hatcheries) for Pacific salmon requires careful
consideration in ESA evaluations. Artificial propagation has
implications for evaluating both production trends and the genetic
integrity of populations. 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. A fundamental
question in ESA risk assessments for mixed-production stocks is
whether natural production is sufficient to maintain the population
without the continued infusion of artificially produced fish.
A full answer to this question is difficult without extensive
studies of relative production and interactions between hatchery
and natural fish. When such information is lacking, the presence
of hatchery fish in natural populations leads to substantial uncertainty
in evaluating the status of the natural population.
Long-term trends in abundance of sockeye
salmon in the Pacific Northwest can only be approximated from
historical records of commercial fishery landings (Fig. 15).
However, these trends largely reflect the harvest of Fraser River
sockeye salmon in British Columbia and Washington, and therefore
do not provide a good indication of the status of ESUs we are
considering here. To the extent that landings reflect population
abundance, these records suggest fairly constant populations of
sockeye salmon in this region except for large short-term fluctuations
(discussed in the next section). Harvest was somewhat higher
near the turn of the century than during 1920-1980, and increasing
harvest in British Columbia since 1980 has restored harvest levels
to near those of the early 1900s.
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 precisely predict the population-scale effects
of habitat loss or degradation, 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 (1996) identified habitat
concerns as one of a suite of factors affecting the decline of
salmon within the range of west coast steelhead. Some of the
habitat impacts identified were: 1) the fragmentation and loss
of available spawning and rearing habitat; 2) alteration of stream
flows and stream-bank and channel morphology; 3) migration delays;
4) degradation of water quality; 5) alteration of ambient stream
water temperatures; 6) sedimentation; 7) loss of spawning gravels,
pool habitat and large woody debris; 8) removal of riparian vegetation;
and 9) decline of habitat complexity.
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." Their concerns relative to
sockeye salmon are 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.
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, will continue into the future. These
facts indicate that there will be some continuing losses of salmon
habitat in the foreseeable future. Balancing this, 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.
Abundance of sockeye salmon populations
tends to fluctuate around a general level, either displaying predictable
cyclic fluctuations or unexpected upward or downward changes (Burgner
1991). In some populations, a large part of this variability
is attributable to the phenomenon of brood-cycle dominance, which
is the tendency of single year-classes to consistently dominate
abundance trends in populations that return to spawn largely at
a single age (Ricker 1950, Ward and Larkin 1964, Eggers and Rogers
1987). This phenomenon was seen in the 1901-brood cycle of sockeye
salmon in the Fraser River in the early 1900s (Fig. 15), which
clearly displayed dominance. This pattern in the overall Fraser
River run was disrupted by the Hells Gate slide, but is still
apparent in the abundance trends of individual Fraser River stocks.
Ricker (1997) reviewed cycles in Fraser River sockeye salmon,
and suggested that interactions among dominant and other brood
lines are the most plausible cause of the cycles. Brood-cycle
dominance is less evident in the U.S. populations we are considering
here, possibly because spawning age-structure is more variable
in most of these populations or because relative abundance has
not been high enough to establish the pattern. Where it occurs,
however, cyclic dominance could be a major influence in abundance
analysis and recovery planning.
Variations in the freshwater and marine
environments are also 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 conditions are an additional factor and
are discussed in the "Recent Events" section. Habitat
degradation and harvest have probably made stocks less resilient
to poor climate conditions, but these effects are not easily quantifiable.
In addition to being a factor in evaluating
natural replacement rates, artificial propagation can have a substantial
impact on genetic integrity of natural salmon and steelhead populations.
This can occur in several ways. First, stock transfers that
result in interbreeding of hatchery and natural fish can lead
to loss of fitness in local populations and loss of diversity
among populations. The latter is important to maintaining long-term
viability of an ESU because genetic diversity among salmonid populations
helps to buffer overall productivity against periodic or unpredictable
changes in the environment (Riggs 1990, Fagen and Smoker 1989).
Ricker (1972) and Taylor (1991) summarized some of the evidence
for local adaptations in Pacific salmonids that may be affected
by stock transfers.
Second, because a successful salmon hatchery
dramatically changes the mortality profile of a population, some
level of genetic change relative to the wild population is inevitable
even in hatcheries that use local broodstock (Waples 1991b).
These changes are unlikely to be beneficial to naturally reproducing
fish.
Third, even if naturally spawning hatchery
fish leave few or no surviving offspring, they still can have
ecological and indirect genetic effects on natural populations.
On the spawning grounds, hatchery fish may interfere
with natural production by competing with natural fish for territory
and/or mates. If they successfully spawn with natural fish, they
may divert production from more productive natural x natural crosses.
The presence of large numbers of hatchery juveniles or adults
may also alter the selective regime faced by natural fish.
Not all of these concerns will apply to
every hatchery population, and the seriousness of the concerns
that do apply can vary considerably among different programs.
For example, although stock transfers are a major issue for some
hatchery programs, many others have exclusively used local broodstock.
Some hatchery programs have also taken a number of measures (e.g.,
in broodstock collection, spawning, rearing, and release protocols)
to minimize adverse effects on natural populations. Therefore,
threats posed by hatchery programs should be evaluated on a casebycase
basis whenever available data allow such an evaluation. It should
be recognized, however, that some changes associated with fish
culture cannot be avoided, and some risks are also inescapable
because they involve a tradeoff with other risks. For example,
changing the hatchery environment to more closely mimic selective
regimes faced in the wild can reduce opportunities for domestication,
but there is a limit to how far this process can go without sacrificing
the early life history survival advantage that is the primary
benefit of a salmon hatchery. Similarly, although releasing hatchery
fish as smolts reduces opportunities for ecological interactions
with natural fish, it also increases opportunities for genetic
change associated with fish culture compared to releases at an
earlier life history stage.
For smaller salmon stocks (either natural
or hatchery), small-population effects (inbreeding, genetic drift)
can also be important concerns for genetic integrity. Inbreeding
and genetic drift are well understood at the theoretical level,
and researchers have found inbreeding depression in various fish
species (reviewed by Allendorf and Ryman 1987). Other studies
(e.g., Simon et al. 1986, Withler 1988, Waples and Teel 1990)
have shown that hatchery practices commonly used with anadromous
Pacific salmonids have the potential to affect genetic integrity.
However, we have not found empirical evidence for inbreeding
depression or loss of genetic variability in any natural or hatchery
populations of Pacific salmon.
A variety of factors, both natural and
human-induced, affect the degree of risk facing salmonid populations.
Because of time-lags 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. However, 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?
For example, climate conditions are known
to have changed recently in the Pacific Northwest, and Pacific
salmon stocks south of British Columbia have been affected by
changes in ocean production that occurred during the 1970s (Pearcy
1992, Lawson 1993). There is mounting evidence that salmon populations
are influenced by decadal-scale shifts in climate patterns; such
effects were discussed at a recent workshop sponsored by NMFS
and Oregon State University (Emmett and Schiewe 1997). Beamish
et al. (1997) have related production of Fraser River sockeye
salmon to decadal-scale shifts in ocean productivity. Much of
the Pacific coast has also been experiencing drought conditions
in recent years, which may depress freshwater production. However,
at this time we do not know whether these climate conditions represent
a long-term change that will continue to affect stocks in the
future or whether these changes are short-term environmental fluctuations
that can be expected to be reversed in the near future.
Other risk factors typically considered
for salmonid populations include disease prevalence, predation,
and changes in life history characteristics such as spawning age
or size.
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 of population
status by agencies or conservation groups of the status of west
coast sockeye salmon stocks (Nehlsen et al. 1991, WDF et al. 1993).
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 were not classifiable due to insufficient information. They
classified stocks as extinct, possibly extinct, at high risk of
extinction, at moderate risk of extinction, or of special concern.
They considered it likely that stocks at high risk of extinction
have reached the threshold for classification as endangered under
the ESA. Stocks were placed in this category if they had declined
from historic levels and were continuing to decline, or had 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 sockeye salmon, they classified 22 stocks as follows:
16 extinct, 1 possibly extinct, 2 high risk, 1 moderate risk,
and 2 special concern (Table 4).
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 nine sockeye
salmon stocks identified, three (Quinault, Wenatchee, and Okanogan)
were classified as healthy, four (Cedar, Lake Washington/Sammamish
Tributaries, Lake Washington Beach, and Ozette) as depressed,
one (Baker) as critical, and one (Lake Pleasant) as unknown.
There are problems in applying results
of these studies to ESA evaluations. One problem is the definition
of categories used to classify stock status. Nehlsen et al. (1991)
used categories intended to relate to ESA "threatened"
or "endangered" status; however 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 west coast sockeye salmon
stocks. Another problem is the selection of stocks or populations
to include in the review. Nehlsen et al. (1991) did not evaluate
(or even identify) stocks not perceived to be at risk, so it is
difficult to determine the proportion of stocks they considered
to be at risk in any given area. There is also disagreement regarding
status of some stocks; for example, IDFG (1996) disagrees with
the classification of Alturas and Stanley Lakes' populations as
extinct by Nehlsen et al. (1991).
Quantitative evaluations of data included
comparisons of current and historical abundance of west coast
sockeye 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, although estimates based on commercial
harvest are available for some coastal populations (Rounsefell
and Kelez 1938).
Time series data were available for many
populations, but data extent and quality varied among ESUs. We
compiled and analyzed this information to provide several summary
statistics of natural spawning abundance, including (where available)
recent total spawning run-size and escapement, percent annual
change in total escapement, recent naturally produced spawning
run-size and escapement, and average percentage of natural spawners
that were of hatchery origin. Information on harvest and stock
abundance was compiled from a variety of state, federal, and tribal
agency records (Foy et al. 1995a, b). Additional data were provided
directly to us by state and tribal agencies and private organizations.
We believe these records to be complete in terms of long-term
adult abundance for sockeye salmon in the region covered. Principal
data sources were adult counts at dams or weirs and spawner surveys.
To represent current run size or escapement
where recent data were available, we have computed the geometric
mean of the most recent 5 years reported (or fewer years if the
data series is shorter than 5 years). We tried to use only estimates
that reflect the total abundance for an entire river basin or
tributary, avoiding index counts or dam counts that represent
only a small portion of available habitat.
Where adequate data were available, trends
in total escapement (or run-size if escapement data were not available)
were calculated for all data sets with more than 7 years of data,
based on total escapement or an escapement index (such as fish
per mile from a stream survey). Separate trends were estimated
for each full data series and for the 1985-1994 period within
each data series. As an indication of overall trend in individual
sockeye salmon populations, we calculated average (over the available
data series) percent annual change in adult spawner indices within
each river basin. Trends were calculated as the slope (a)
of the regression of ln(abundance) against years corresponding
to the biological model N(t) = beat. Slopes
significantly different from zero (P<0.05) were noted. The
regressions provided direct estimates of mean instantaneous rates
of population change (a); these values were subsequently
converted to percent annual change, calculated as 100(ea
- 1). No attempt was made to account for the influence of hatchery
produced fish on these estimates, so the estimated trends include
any supplementation effect of hatchery fish.
These computed statistics, along with
published estimates of historical abundance and results of previous
status assessments, are summarized in Appendix Table E-1 for all
stocks examined in this review.
The major abundance data series for Okanogan
River sockeye salmon consists of spawner surveys conducted in
the Okanogan River above Lake Osoyoos since the late 1940s, counts
of adults passing Wells Dam since 1967, and records of tribal
harvest (Colville and Okanogan) since the late 1940s. Longer-term
data were available for dams lower on the Columbia River (notably
Rock Island Dam counts starting in 1933), but these counts represent
a combination of this ESU with the Wenatchee populations and other
historical ESUs from the upper Columbia River above Grand Coulee
Dam.
Blockage and disruption of freshwater
habitat pose some risk for this ESU. Adult passage is blocked
by dams above Lake Osoyoos, prohibiting access to former habitat
in Vaseux, Skaha, and Okanagan Lakes (Chapman et al. 1995). (However,
it is not known whether sockeye salmon in these upper lakes belonged
to the same ESU as those in Lake Osoyoos.) Other problems in
the Okanogan River include inadequately screened water diversions
and high summer water temperatures (Chapman et al. 1995), and
channelization of spawning habitat in Canada. Mullan (1986) stated
that hydroelectric dams accounted for the general decline of sockeye
salmon in the mainstem Columbia River, while Chapman et al. (1995)
suggested that hydropower dams have "probably" reduced
runs of sockeye salmon to the Columbia River, particularly to
Lake Osoyoos.
The most recent 5-year average annual
escapement for this ESU was about 11,000 adults, based on 1992-1996
counts at Wells Dam (see Appendix Table E-1). No historic abundance
estimates specific to this ESU are available. However, analyses
conducted in the late 1930s indicated that less than 15% of the
total sockeye run in the upper Columbia River went into Lakes
Osoyoos and Wenatchee (Chapman et al. 1995). At that time, the
total run to Rock Island Dam averaged about 15,000, suggesting
a combined total of less than 2,250 adults returning to the Okanogan
River and Lake Wenatchee ESUs. Thus, abundance for the Okanogan
River ESU during the late 1930s was clearly substantially lower
than recent abundance. Trend estimates for this stock differ
depending on the data series used (see Appendix Table E-1), but the recent
(1986-1995) trend has been steeply downward (declining at 2-20%
per year); however, this trend is heavily influenced by high abundance
in 1985 and low points in 1990, 1994, and 1995, which may reflect
environmental fluctuations (Fig. 17). The long-term trend (since
1960) for this stock has been relatively flat (-3% to +2% annual
change).
For the entire Columbia River basin, there
has been a considerable decline in sockeye salmon abundance since
the turn of the century. Columbia River commercial sockeye salmon
landings that commonly exceeded 1,000,000 pounds in the late 1800s
and early 1900s had been reduced to about 150,000 pounds by the
late 1980s (TAC 1991). Since 1988, harvest has been fewer than 3,500 fish each year.
The TAC (1991) attributes this decline to habitat degradation
and blockage, overharvest, hydroelectric development, and nursery
lake management practices. The two remaining productive stocks
(Okanogan and Wenatchee) occupy less than 4% of historic nursery
lake habitat in the upper Columbia River basin.
Both Okanogan and Wenatchee runs have
been highly variable over time. For harvest purposes, these two
ESUs are managed as a single unit, with an escapement goal of
65,000 adults returning to Priest Rapids Dam (TAC 1991). This
goal has been achieved only ten times since 1970, and has been
met in 2 of the last 5 years. Examination of the historical trend
in total sockeye salmon escapement to the upper Columbia River
(Fig. 16) shows very low abundance (averaging less than 20,000
annually) during the 1930s and early 1940s, followed by an increase
to well over 100,000 per year in the mid-1950s. Since the mid-1940s,
abundance has fluctuated widely, with noticeable low points reached
in 1949, 1961-62, 1978, and 1994. The escapement of about 9,000
fish to Priest Rapids Dam in 1995 was the lowest since 1945, but
1996 escapement (preliminary estimate, Fish Passage Center 1996)
was considerably higher, although still far below the goal. Escapement
to Wells Dam (i.e., this ESU) was at its lowest recorded value
in 1994, but increased in both 1995 and 1996.
Past and present artificial propagation
of sockeye salmon poses some risk to the genetic integrity of
this ESU. The GCFMP (discussed in the "Artificial Propagation"
section above) interbred fish from this ESU with those from adjacent
basins for several years, with unknown impacts on the genetic
composition of this ESU. Current artificial propagation efforts
use local stocks and are designed to maintain genetic diversity,
but there is some risk of genetic change resulting from domestication.
There is only one record of introduction of sockeye salmon from
outside the Columbia River Basin into this ESU: 395,420 mixed
Quinault Lake/Rock Island Dam stock released in 1942 (Mullan 1986)
(see Appendix Table D-2). Records of kokanee transplants are
most likely incomplete (see Appendix Table D-5).
In previous assessments of this stock,
Nehlsen et al. (1991) considered Okanogan River sockeye salmon
to be of special concern because of "present or threatened
destruction, modification, or curtailment of its habitat or range,"
including mainstem passage, flow, and predation problems. While
WDF et al. (1993) classified this stock as of native origin, wild
production, and healthy status they also suggested that this "native"
classification will be changed to "mixed" in the future
(WDFW 1996).
The major abundance data series for Wenatchee
River sockeye salmon consists of spawner surveys conducted in
the Little Wenatchee River and the White River since the late
1940s, counts of adults passing Tumwater Dam (sporadic counts
1935 to present), and reconstructions based on adult passage counts
at Priest Rapids, Rock Island, and Rocky Reach Dams (early 1960s
to present). Longer-term data are available for dams lower on
the Columbia River (notably Rock Island Dam counts starting in
1933), but these counts represent a combination of this ESU with
the Okanogan River ESU and other historic potential ESUs from
the upper Columbia River above Grand Coulee Dam.
There are no substantial blockages of
sockeye salmon habitat in the Wenatchee basin, and habitat condition
in the basin is generally regarded as good, although production
is limited by the oligotrophic nature of Lake Wenatchee (Chapman
et al. 1995). Mullan (1986) and Chapman et al. (1995) concluded
that the main freshwater-habitat problem presently facing this
ESU is hydropower dams in the mainstem Columbia River, which have
probably reduced runs of sockeye salmon.
The most recent 5-year average annual
escapement for this ESU was about 19,000 adults, based on the
1992-1996 difference in adult passage counts at Priest Rapids
and Rocky Reach Dams (see Appendix Table E-1). No historic abundance
estimates specific to this ESU are available. However, as discussed
above for the Okanogan River ESU, abundance of the Lake Wenatchee
ESU during the late 1930s was clearly substantially lower than
recent abundance. The recent (1986-1995) trend in abundance has
been downward (declining at 10% per year), but this trend was
heavily influenced by 2 years of very low abundance in 1994 and
1995 (Fig. 17). The long-term (1961-1996) trend for this stock
is flat. Escapement to this ESU in 1995 (counts at Priest Rapids
Dam minus those at Rocky Reach Dam) was the lowest since counting
began in 1962, but 1996 escapement was somewhat higher (Fig. 17).
Other risk factors common to this ESU and other Columbia River
Basin sockeye salmon populations were discussed under the Okanogan
River ESU above.
Past and present artificial propagation
of sockeye salmon poses some risk to the genetic integrity of
this ESU. As for the Okanogan River ESU, the GCFMP interbred
fish from this ESU with those from adjacent basins for several
years and introduced many sockeye salmon descended from Quinault
Lake stock (Mullan 1986) (Appendix D-2), with unknown impacts
on the genetic composition of this ESU. Current artificial propagation
efforts use local stocks and are designed to maintain natural
genetic diversity, but there is some risk of genetic change resulting
from domestication. Hatchery-raised kokanee have been released
in Lake Wenatchee, including native Lake Wenatchee stock and nonnative
Lake Whatcom stock (Mullan 1986) (see Appendix Table D-5). The
effect of Lake Whatcom kokanee introductions on the genetic integrity
of this ESU is unknown.
Previous assessments of this ESU are similar
to those for the Okanogan River ESU. Nehlsen et al. (1991) considered
Wenatchee River sockeye salmon to be of special concern because
of "present or threatened destruction, modification, or curtailment
of its habitat or range," including mainstem passage, flow,
and predation problems. WDF et al. (1993) classified this stock
as of mixed origin, wild production, and healthy status. Huntington
et al. (1996) identified this stock as "healthy-Level I,"
indicating that current abundance is high relative to what would
be expected without human impacts.
The major abundance data series for Quinault
River sockeye salmon consists of escapement estimates derived
from hydroacoustic surveys conducted in Quinault Lake since the
mid-1970s, supplemented with earlier estimates (beginning in 1967)
based on spawner surveys. The most recent (1991-1995) 5-year
average annual escapement for this ESU was about 32,000 adults,
with a run-size of about 39,000 (see Appendix Table E-1 and
Fig.
18). Approximate historical estimates indicate escapements ranging
between 20,000 and 250,000 in the early 1920s, and run sizes ranging
between 50,000 and 500,000 in the early 1900s (Rounsefell and
Kelez 1938). Comparison of these estimates indicates that recent
abundance is probably near the lower end of the historical abundance
range for this ESU.
This ESU has been substantially affected
by habitat problems, notably those resulting from forest management
activities in the upper watershed outside Olympic National Park.
Early inhabitants of the area described the upper Quinault River
as flowing between narrow, heavily-wooded banks, but by the 1920s
the river was in a wide valley with frequent course changes and
much siltation and scouring of gravels during winter and spring
freshets (Davidson and Barnaby 1936, QIN 1981); resultant loss
of spawning habitat in the Quinault River above Quinault Lake
has continued to recent times (QIN 1981).
While stock abundance has fluctuated considerably
over time (recent escapements ranging from a low of 7,500 in 1970
to 69,000 in 1968), the overall trend has been relatively flat.
For the full data series (1967-1995), abundance has increased
by an average of about 1% per year; for the 1986-1995 period,
abundance declined by about 3% per year.
Artificial propagation of sockeye salmon
in the Quinault River basin has a long history (see "Artificial
propagation" section above). Releases have been primarily
native Quinault Lake stock, although Alaskan sockeye salmon eggs
were brought into the system prior to 1920 (see Appendix Tables
D-1 and D-2). Genetic effects of this introduction are unknown.
Since 1973, all releases have been of local stock, but there
is some risk of genetic change resulting from unnatural selective
pressures.
In previous assessments, Nehlsen et al.
(1991) did not identify Quinault Lake sockeye salmon as at risk,
and WDF et al. (1993) classified this stock as of native origin,
wild production, and healthy status.
The major abundance data series for Ozette
River sockeye salmon consists of escapement estimates derived
from counts at a weir located at the outlet of Ozette Lake. Counting
has occurred in most years since 1977 (Dlugokenski et al. 1981,
WDF et al. 1993). The most recent (1992-1996) 5-year average
annual escapement for this ESU was about 700 adults (see Appendix
Table E-1). Historical estimates indicate run sizes of a few
thousand sockeye salmon in 1926 (Rounsefell and Kelez 1938), with
a peak recorded harvest of nearly 18,000 in 1949 (WDF 1974).
Subsequently, commercial harvest declined steeply to only a few
hundred fish in the mid-1960s and was ended in 1974. A small
ceremonial and subsistence fishery continued until 1981 (Dlugokenski
et al. 1981); there has been no direct fishery on this stock since
1982 (WDF et al. 1993). Assuming that Ozette River harvest consisted
of sockeye salmon destined to spawn in this system, comparison
of these estimates indicates that recent abundance is substantially
below the historical abundance range for this ESU.
Three studies have been undertaken to
evaluate habitat-related factors limiting production of sockeye
salmon in Ozette Lake. The U.S. Fish and Wildlife Service conducted
studies of the decline in this stock during the 1970s, culminating
in a report describing limiting factors and outlining a restoration
plan (Dlugokenski et al. 1981). This report noted that this population
formerly spawned in tributaries but presently only uses the lakeshore,
and that food supply, competition, and predation in the lake are
probably not limiting, but that siltation has caused cementing
of spawning gravels in tributaries. Dlugokenski et al. (1981)
suspected that sedimentation, resulting primarily from logging
and associated road building, coupled with log truck traffic on
weak siltstone roadbeds, have led to decreased hatching success
of sockeye salmon in tributary creeks and creek outwash fans in
Ozette Lake. The authors concluded that "a combination of
overfishing and habitat degradation have reduced the sockeye population
to its current level of less than 1,000 fish" (p. 43).
More recently, Blum (1988) conducted an
assessment of the same problems and concluded that "the absence
of tributary spawners is the paramount problem explaining why
sockeye runs have not increased following the cessation of terminal-area
fishing in 1973." He cited three main problems related to
road-building and logging that limit spawning habitat: increased
magnitude and frequency of peak flows, stream-bed scouring, and
degraded water quality. He also noted that "the logging
of the watershed was so extensive that stream spawning and rearing
conditions are still questionable, despite having 35 years to
recover" (p. 1). Finally, Beauchamp et al. (1995) examined
patterns of prey, predator, and competitor abundance in Ozette
Lake as potential limiting factors for juvenile production of
sockeye salmon and kokanee. They concluded that competition is
unlikely to limit production but that predation could be a limiting
factor; however, data on piscivore abundance were lacking, so
the authors could not evaluate predation impact accurately.
A recent National Park Service Technical
Report (Jacobs et al. 1996) reported the conclusions of a review
panel concerning the status and management of sockeye salmon in
Ozette Lake. The panel was unanimous in expressing great concern
about the future of this population, but was unable to identify
a single set of factors contributing to the population decline.
The panel concluded that declines were likely the result of a
combination of factors, possibly including introduced species,
predation, loss of tributary populations, decline in quality of
beach-spawning habitat, temporarily unfavorable oceanic conditions,
excessive historical harvests, and introduced diseases. They
felt that intra- and inter-specific competition was unlikely as
a contributing factor.
Harvest of sockeye salmon in the Ozette
River fluctuated considerably over time (Fig. 19), which would indicate similar
fluctuations in spawner abundance if harvest rates were fairly
constant. Based on the full weir-count series (1977-1995), abundance
has decreased by an average of about 3% per year; for the 1986-1995
period the decrease averaged 10% per year. However, in recent
years the stock has exhibited dominance by a single brood cycle
returning every 4 years (1984, 1988, 1992, 1996), and this dominant
cycle has remained stable at between 1,700 and 2,200 adults; declines
are apparent only in the smaller returns during off-cycle years
(Fig. 19).
Artificial propagation has not been extensive
in this basin, but many of the releases have been non-indigenous
stocks (see "Artificial Propagation" section). Genetic
effects of these introductions are unknown. Recent hatchery production
in Ozette Lake has been primarily from local stock, with the exception
of 120,000 Quinault Lake sockeye salmon juveniles released in
1983. The release of 14,398 kokanee/sockeye salmon hybrids in
1991-1992 (MFMD 1995, NRC 1995) may have had deleterious effects
on genetic integrity of the ESU because Ozette Lake kokanee are
genetically dissimilar to Ozette Lake sockeye salmon (see above
"Genetics" section).
In previous assessments, Nehlsen et al.
(1991) identified Ozette sockeye salmon as at moderate risk of
extinction, citing logging and overfishing in the 1940s and 1950s
as major causes of the decline. WDF et al. (1993) classified
this stock as of native origin, wild production, and depressed
status.
The major abundance data series for Baker
River sockeye salmon consists of escapement estimates derived
from counts of adults arriving at a trap below Lower Baker Dam
beginning in 1926 (Fig. 20). The most recent 5-year average annual
escapement for this ESU was about 2,700 adults (see Appendix Table
E-1). Historical estimates indicate escapements averaging 20,000
near the turn of the century, with a pre-dam low of 5,000 in 1916
(Rounsefell and Kelez 1938), although WDFW data suggest that the
20,000 figure is a peak value, not an average (Sprague
1996a). Comparison of these estimates indicates that recent
average abundance is probably near the lower end of the historical
abundance range for this ESU, although escapement in 1994 (16,000
fish) was near the turn-of-the-century average.
Currently, spawning is restricted to artificial
spawning "beaches" at the upper end of Baker Lake (in
operation since 1957) and just below Upper Baker Dam (beach constructed
in 1990). Spawning on the beaches is natural, and fry are released
to rear in Baker Lake. Before 1925, sockeye salmon had free access
to Baker Lake and its tributaries. Lower Baker Dam (constructed
1925) blocked access to this area, but passage structures were
provided. Upper Baker Dam was completed in 1959 and increased
the size of Baker Lake, inundating most natural spawning habitat;
this was mitigated by construction of artificial spawning beaches.
In most years, all returning adults are trapped below Lower Baker
Dam and transported to the artificial beaches, with no spawning
occurring in natural habitat (WDF et al. 1993). The only recent
exception to this was in 1994, when the large number of returning
adults exceeded artificial habitat capacity, and excess spawners
were allowed to enter Baker Lake and its tributaries (J. Ames58).
At the time of this report, no quantitative reports regarding
offspring resulting from this spawning "experiment"
are available (WDFW 1996).
The artificial nature of spawning habitat,
use of net-pens for juvenile rearing, and reliance on artificial
upstream and downstream transportation poses a certain degree
of risk to the ESU. These human interventions in the life-cycle
have undoubtedly changed selective pressures on the population
from those under which it evolved its presumably unique characteristics,
and thus pose some risk to the long-term evolutionary potential
of the ESU. There have been continuing potential problems with
siltation at the newer (lower) spawning beach (WDF et al. 1993),
and recent proposals to close the two upper beaches in favor of
production at the lower beach would thus be likely to increase
risk of spawning failure in some years. The future use of the
upper beaches is uncertain (WDFW 1996). Problems with operations
of downstream smolt bypass systems have been documented, and there
may be limitations to juvenile sockeye production due to inadequate
lake productivity and interactions with other salmonids (WDF et
al. 1993). IHN has also been a recent problem for this stock
(G. Sprague59).
While stock abundance has fluctuated considerably
over time (recent escapements ranging from a low of about 100
in 1985 to 16,000 in 1994), the long-term trend has been relatively
flat. For the full data series (1926-1995), abundance has decreased
by an average of about 2% per year; for the 1986-1995 period,
abundance increased by about 32% per year.
Artificial production in this ESU began
in 1896 with a state hatchery on Baker Lake; hatchery efforts
at Baker Lake ended in 1933, by which time the hatchery was being
operated by the U.S. Bureau of Fisheries (see "Artificial
Propagation" section, WDF et al. 1993). Current propagation
efforts rely primarily on the spawning beaches and net-pen rearing.
Lake Whatcom kokanee were recently introduced to Lake Shannon
(Knutzen 1995). Genetic consequences of these releases and rearing
programs are unknown, but there is some risk of genetic change
resulting from unnatural selective pressures.
In previous assessments, Nehlsen et al.
(1991) identified Baker River sockeye salmon as at high risk of
extinction, and WDF et al. (1993) classified this stock as of
native origin, artificial production, and critical status.
Although no recent complete escapement
estimates are available for this stock, we recently have received
some spawner-survey data for the period 1987 to 1996 (Mosley 1995,
Tierney 1997). Peak spawner counts ranged from a low of 90 (1991-a
year with limited sampling) to highs above 2,000 (1987 and 1992).
Abundance fluctuated widely during this period, with a slight
negative trend overall.
Complete counts at a trapping station
on Lake Creek in the early 1960s showed escapements of sockeye
salmon ranging from 763 to 1,485 fish, and 65,000 sockeye salmon
smolts were reported to have outmigrated in 1958 (Crutchfield
et al. 1965). This stock supports small sport and tribal commercial
fisheries, with probably fewer than 100 fish caught per year in
each fishery (WDF et al. 1993). Sockeye salmon from Grandy Creek
stock were released in 1933 and 1937; no sockeye salmon have been
introduced since then (see "Artificial Propagation"
section above).
In previous assessments, Nehlsen et al.
(1991) did not identify Lake Pleasant sockeye salmon as at risk,
and WDF et al. (1993) classified this stock as of native origin,
wild production, and unknown status.
Abundance data for Big Bear Creek sockeye
salmon are derived from spawner surveys conducted by WDFW from
1982 to the present (WDF et al. 1993, J. Ames60). The most recent
(1991-1995) 5-year average annual escapement for this unit was
about 11,400 adults (see Appendix Table E-1). No historical estimates
are available, but comparing habitat areas in these basins with
other sockeye salmon populations suggests that current production
is probably a substantial proportion of freshwater habitat capacity.
Habitat in this basin is subject to effects of urbanization.
Stock abundance has fluctuated considerably
over time, with recent escapements ranging from a low of 1,800
in 1989 to 39,700 in 1994. There has been little overall trend
in this unit; for the full data series (1982-1995), abundance
has decreased by an average of about 7% per year; for the 1986-1995
period, abundance decreased approximately 4% per year. 1995 escapement
was the second lowest on record, but 1994 was the highest.
Releases of non-native sockeye salmon
in this area have occurred on Big Bear and North Creek (tributaries
of the Sammamish River), using Grandy Creek stock from the Skagit
River and Cultus Lake stock from British Columbia, respectively
(see Appendix Table D-2). There have been extensive introductions
of kokanee in this area, a substantial proportion of which were
from Lake Whatcom. Genetic interactions of these kokanee with
sockeye salmon are unknown.
In previous assessments, Nehlsen et al.
(1991) did not identify this stock as at risk, and WDF et al.
(1993) classified this stock as of unknown origin, wild production,
and depressed status.
While the units discussed below are not
presently considered to constitute ESUs, we briefly examined available
information regarding population status and extinction risk.
Three other sockeye salmon stocks (Cedar River, Issaquah Creek,
and Lake Washington beach spawners) are apparently introduced
from outside the Lake Washington drainage and have not been included
in a recognized ESU at this time (see above "Discussion and
conclusions on ESU Determinations" section).
Beyond WDFW Salmon Spawning Ground Survey
Data (Egan 1977, 1995, 1997) and anecdotal reports (see above
section "Information Specific to Sockeye Salmon Populations
Under Review") of small numbers of sockeye salmon observed
regularly spawning in some Puget Sound and coastal Washington
rivers with no access to lake rearing habitat, we have no information
on overall abundance or trends for these stocks.
Counts of sockeye salmon adults reaching
Pelton Dam on the Deschutes River have been made during most years
since the mid-1950s (Fig. 21).
The most recent (1990-1994) 5-year
average annual escapement was only 9 adults (see Appendix Table
E-1). No accurate estimates of historical abundance are available
for this unit, but a substantial run is known to have spawned
in Suttle Lake prior to construction of a dam in the 1930s, and
is believed to have continued to spawn in the Metolius River after
that time (CBFWA 1990, Olsen et al. 1994, ODFW 1995a). Since
construction of Pelton Dam, abundance has reached peaks of about
300 fish in several years (1962, 1963, 1973, 1976-Fish Commission
of Oregon 1967, O'Connor et al. 1993). We have made no evaluation
of abundance of kokanee in the Deschutes River basin, which may
be part of the same evolutionary unit as sockeye salmon in this
basin. Sockeye salmon derived from the GCFMP were introduced
into Suttle Lake and the Metolius River between 1937 and 1961
(see "Artificial Propagation" section) (see Appendix
Table D-3).
Sockeye salmon stock abundance has fluctuated
considerably over time (recent escapements ranging from a low
of 1 in 1993 to 340 in 1963), but there has been a substantial
decline over the years for which data are available. For the
full data series (1957-1994), abundance decreased by an
average of about 3% per year; for the 1985-1994 period, abundance
declined by about 13% per year. Nehlsen et al. (1991) identified
Deschutes River sockeye salmon as at high risk of extinction.
The BRT has concluded that if recent conditions
continue into the future, one ESU (Ozette Lake) is likely to become
endangered, and four ESUs (Okanogan River, Lake Wenatchee, Quinault
Lake, and Baker River) and one provisional ESU (Big Bear Creek)
are not presently in significant danger of becoming extinct or
endangered. For the sixth ESU (Lake Pleasant), there was insufficient
information to reach a conclusion regarding risk of extinction.
Consideration was also given to the status
of two other population units for which ESU status has not been
determined. For one of these (riverine sockeye salmon) there
was insufficient information to reach any conclusions regarding
risk of extinction. For the other unit (Deschutes River sockeye
salmon), the BRT concluded that the anadromous component is clearly
in danger of extinction if not already extinct.
The following paragraphs summarize the conclusions for each ESU or other population unit, and major considerations leading to these conclusions are summarized in Tables 5 and 6.
These conclusions are tempered by uncertainties
in specific critical information. For several units, there are
kokanee (either native or introduced) populations using the same
water bodies as sockeye salmon; potential interbreeding and ecological
interactions could affect population dynamics and (in the case
of non-native kokanee) genetic integrity of the sockeye salmon
populations. With few exceptions, adult abundance data do not
represent direct counts of adults destined to a
single spawning area, so estimates of total population abundance
and trends in abundance must be interpreted with some caution.
The BRT had several concerns about the
overall health of this ESU. Low abundance, downward trends and
wide fluctuations in abundance, land use practices, and variable
ocean productivity were perceived as resulting in low to moderate
or increasing risk for the ESU. Other major concerns regarding
health of this ESU were restriction and channelization of spawning
habitat in Canada, hydrosystem impediments to migration, and water
temperature problems in the lower Okanogan River. Positive indicators
for the ESU were escapement above 10,000, which is probably a
substantial fraction of historical abundance, and the limited
amount of recent hatchery production within the ESU. Recent changes
in hydrosystem management (increases in flow and spill in the
mainstem Columbia River) and harvest management (restrictions
in commercial harvest to protect Snake River sockeye salmon) were
regarded as beneficial to the status of this ESU. The BRT concluded
unanimously that the Okanogan River sockeye salmon ESU is not
presently in danger of extinction, nor is it likely to become
endangered in the foreseeable future. However, the very low returns
in the 3 most recent years suggest that the status of this ESU
bears close monitoring and its status should be reconsidered if
abundance remains low.
The BRT had several concerns about the
overall health of this ESU. Low abundance, downward trends and
wide fluctuations in abundance, and variable ocean productivity
were perceived as resulting in low to moderate risk for the ESU.
Other major concerns regarding the health of this ESU were the
effects of hatchery production, hydrosystem impediments to migration,
and potential interbreeding with nonnative kokanee on genetic
integrity of the unit. Positive indicators for the ESU were escapement
above 10,000, and the limited amount of recent hatchery production
within the ESU. Recent changes in hydrosystem management (increases
in flow and spill in the mainstem Columbia River) and harvest
management (restrictions in commercial harvest to protect Snake
River sockeye salmon) were regarded as beneficial to the status
of this ESU. The majority of the BRT concluded that the Lake
Wenatchee sockeye salmon ESU is not presently in danger of extinction,
nor is it likely to become endangered in the foreseeable future.
A minority concluded that this ESU is likely to become endangered
in the foreseeable future, largely on the basis of extremely low
abundance in the last 3 years. In any case, the very low returns
in the 3 most recent years suggest that the status of this ESU
bears close monitoring and should be reconsidered if abundance
remains low.
All risk factors were perceived as very
low or low for this ESU. However, the BRT had two concerns about
the overall health of this ESU. The ESU is presently near the
lower end of its historical abundance range, a fact that may be
largely attributed to severe habitat degradation in the upper
river, which contributes to poor spawning habitat quality and
possible impacts on juvenile rearing habitat in Quinault Lake.
The influence of hatchery production on genetic integrity is
also a potential concern for the ESU. On the positive side, the
BRT noted that recent escapement averaged above 30,000, harvest
management has been responsive to stock status, and recent restrictions
in logging to protect terrestrial species should have a beneficial
effect on habitat conditions. The BRT concluded unanimously that
the Quinault Lake sockeye salmon ESU is not presently in danger
of extinction, nor is it likely to become endangered in the foreseeable
future.
Perceived risks ranged from low to moderate
for genetic integrity and variable ocean productivity, from low
to moderate and increasing for downward trends and population
fluctuations, and from moderate to increasing for abundance considerations.
Current escapements averaging below 1,000 adults per year imply
a moderate degree of risk from small-population genetic and demographic
variability, with little room for further declines before abundances
would be critically low. Other concerns include siltation of
beach spawning habitat, very low abundance compared to harvest
in the 1950s, and potential genetic effects of present hatchery
production and past interbreeding with genetically dissimilar
kokanee. The BRT concluded that the Ozette Lake sockeye salmon
ESU is not presently in danger of extinction, but if present conditions
continue into the future, it is likely to become so in the foreseeable
future.
The BRT had several concerns about the
overall health of this ESU, focusing on high fluctuations in abundance,
lack of natural spawning habitat, and the vulnerability of spawning
beaches to water quality problems. Large fluctuations in abundance
were a substantial concern. It is also likely that this stock
would go extinct if present human intervention were halted, and
problems related to that intervention pose some risk to the population.
In particular, the BRT concluded that the proposed change in
management to concentrate spawning in a single spawning beach
could substantially increase risk to the population. There was
considerable disagreement regarding the risks associated with
several factors for this ESU. For example, the assessment of
perceived risk for abundance and habitat capacity ranged among
BRT members from very low to high, and classifications for risks
related to water quality and disease also had wide ranges. The
majority of the BRT concluded that the Baker sockeye salmon 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 concluded that this ESU is likely to become
endangered in the foreseeable future, largely on the basis of
lack of natural spawning habitat and the vulnerability of the
entire population to problems in artificial habitats.
Although
escapement monitoring data are sparse, escapements (represented
by peak spawner counts) in the late 1980s, and 1990s appear roughly
comparable to habitat capacity for this small lake (peak spawner
counts for the 1990s were not available at the time the BRT met).
Some concerns were expressed regarding potential urbanization
of habitat and effects of sport harvest during the migration delay
in the Sol Duc River. It was noted that recent restrictions in
logging to protect terrestrial species should have a beneficial
effect on habitat conditions, although little or no old growth
forest is present in the watershed. The majority of the BRT concluded
that there was insufficient information to adequately assess extinction
risk for the Lake Pleasant ESU, although a minority concluded
that the ESU is not presently in danger of extinction nor likely
to become so in the foreseeable future.
The BRT had several concerns about the
health of this provisional ESU and felt that the extreme fluctuations
in recent abundances and potential effects of urbanization in
the watershed suggest that the status of this populations bears
close monitoring. Recent average abundance has been relatively
high, with escapement between 10,000 and 20,000. Recent development
of a county growth management plan was seen as a possible benefit
to freshwater habitat for this population. The majority of the
BRT concluded 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 concluded that this provisional ESU is likely
to become endangered in the foreseeable future, while a second
minority felt that information was insufficient to adequately
assess extinction risk.
There was insufficient information to
reach any conclusion regarding the status of this unit.
The
BRT concluded that if anadromous sockeye salmon recently seen
in the lower Deschutes River are remnants of the historic Deschutes
River ESU, the ESU clearly is in danger of extinction due to extremely
low population abundance. If there is an ESU that includes sockeye
salmon and native kokanee above Round Butte Dam, further evaluation
of the kokanee stock and its relationship to the sockeye salmon
would need to be completed before any conclusions regarding extinction
risk could be made. If these sockeye salmon originated from stocks
outside the Deschutes River Basin, then they are not subject to
protection under the ESA.