U.S. Dept Commerce/NOAA/NMFS/NWFSC/Publications
NOAA Technical Memorandum NMFS-NWFSC-10
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Status Review for Oregon's Illinois River Winter Steelhead
Peggy J. Busby, Orlay W. Johnson, Thomas C. Wainwright, F. William Waknitz, and Robin S. Waples
National Marine Fisheries Service
Northwest Fisheries Science Center
Coastal Zone and Estuarine Studies Division
2725 Montlake Blvd. E.
Seattle WA 98112
May 1993
U.S. DEPARTMENT OF COMMERCE
Ronald H. Brown, Secretary
National Oceanic and Atmospheric Administration
John A. Knauss, Administrator
National Marine Fisheries Service
William W. Fox, Jr., Assistant Administrator for Fisheries
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CONTENTS
SUMMARY
This report summarizes biological information gathered in conjunction with an Endangered
Species Act (ESA) status review for winter steelhead (Oncorhynchus mykiss) from the Illinois River, a
tributary of the Rogue River in southern Oregon. The National Marine Fisheries Service (NMFS)
received a petition in May 1992 asking that this population be listed as a threatened or endangered
species under the ESA. In evaluating the petition, two key questions had to be addressed: Do Illinois
River winter steelhead represent a species as defined by the ESA? and, if so, is the species threatened
or endangered? With respect to the first question, the ESA allows listing of "distinct population
segments" of vertebrates as well as named species and subspecies. NMFS policy on this issue for
Pacific salmon and steelhead 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.
The petitioners argued that geographic isolation of the Illinois River spawning grounds, the
partial barrier of Illinois River Falls, life history differences between steelhead from the Illinois
and Rogue Rivers, and evidence for genetic differences between steelhead from southern and northern
Oregon demonstrate reproductive isolation of Illinois River winter steelhead. Distinctive life
history and habitat characteristics were the primary factors identified by the petitioners as evidence
that Illinois River winter steelhead contribute substantially to the species' ecological/genetic diversity. A tenfold decline in angler catch of Illinois River winter steelhead since 1971 was cited as evidence that the population qualifies for
listing under the ESA.
In evaluating the status of Illinois River winter steelhead, NMFS focused on information for
coastal steelhead populations from southern Oregon and northern California. The National Marine
Fisheries Service concluded that available information does not make a strong case for reproductive
isolation of Illinois River winter steelhead. Genetic data, including new data gathered for this
status review, fail to show that Illinois River winter steelhead as a group are distinct from other
coastal steelhead populations. Although this does not prove that Illinois River winter steelhead are
not reproductively isolated, it does mean that evidence to support reproductive isolation must be
found elsewhere. Other lines of information are largely inconclusive in this regard. Straying data
for naturally spawning steelhead in the region are largely nonexistent. Geographic features such as
the Illinois River Falls are potential isolating mechanisms, but evidence that they operate in this
way is lacking. Although other explanations are possible, life history characteristics suggest some
degree of reproductive isolation from Rogue River steelhead. However, these same characteristics fail
to show differences between Illinois River winter steelhead and most other coastal steelhead
populations.
With respect to the second criterion for defining an ESU, several phenotypic and life history
characteristics show modest differences between Illinois River winter steelhead and steelhead from
the Rogue River. These differences suggest that either a) there are some genetic differences between
steelhead from the two rivers, b) the natural environments of the two rivers differ in at least some
respects, or c) artificial propagation has affected life history
characteristics of Rogue River steelhead, thus causing them to differ from Illinois River winter
steelhead. In any case, in the larger context of coastal steelhead from southern Oregon and northern
California, it is the Rogue River fish, rather than the Illinois River winter steelhead, that appear to
be somewhat anomalous. That is, steelhead from the Illinois River appear to be somewhat distinctive in
comparison to Rogue River steelhead, but not in comparison to other coastal steelhead populations.
We therefore conclude that although Illinois River winter steelhead may be locally distinctive
within the Rogue River basin, they do not by themselves represent an evolutionarily significant unit
of the biological species Oncorhynchus mykiss.
Because Illinois River winter steelhead are therefore not a "species" as defined by the ESA,
the question of whether they should be listed as threatened or endangered under the Act need not be
addressed. Nevertheless, steelhead from the Illinois River are undoubtedly part of a larger ESU whose
boundaries remain to be determined. Whether the larger ESU that contains Illinois River winter
steelhead would merit protection under the ESA cannot be determined until the nature and extent of the
ESU are identified and additional information about patterns of abundance in coastal steelhead is
compiled. This status review, therefore, should be viewed as the first step in a process to define the
larger ESU and determine whether it qualifies for protection under the ESA.
ACKNOWLEDGMENTS
The status review for the Illinois River winter steelhead was conducted by a team of scientists
from the Northwest Fisheries Science Center (NWFSC). The biological review team relied on an
extensive ESA public record developed pursuant to this review and comprised of public comments and
research reports submitted by dedicated citizens and by state and federal agencies. Special
acknowledgment should be extended to the Oregon Department of Fish and Wildlife (ODFW) and the U.S.
Forest Service, who bore the burden of supplying the review team with a large number of publications
required for this review.
The review team would also like to acknowledge the assistance of personnel from ODFW's Rogue
River and Gold Beach District Offices, California Department of Fish and Game (CDFG) Region 1, Redwood
National Park, and Six Rivers and Rogue River National Forests in the collections of steelhead for
genetic analysis. Norman Buroker generously shared with us his unpublished data on steelhead
mitochondrial DNA. We also would like to acknowledge personnel from the Genetics Project at the NWFSC
for assistance with field collection and electrophoresis of collected samples: Paul Aebersold, Mary
Ann Brainard, Jeffrey Hard, Kathleen Neely, Cynthia Shiflett, Frederick "Bud" Welch, and Stephanie
Woods. Garth Griffin of the NMFS Northwest Region in Portland provided invaluable assistance in
facilitating information exchange. Paul Moran and Linda Park assisted with reviewing DNA data.
Members of the biological review team were Peggy Busby, David Damkaer, Robert Emmett, Steve
Grabowski, Orlay Johnson, Conrad Mahnken, Gene Matthews, Michael Schiewe, Thomas Wainwright, William
Waknitz, Robin Waples, John Williams, and Gary Winans.
INTRODUCTION
The name steelhead refers to the anadromous form of Oncorhynchus mykiss. Endemic distribution
of steelhead extends from the Kamchatka Peninsula in Asia, east to Alaska, and south along the Pacific
coast of North America to northern Baja California (Barnhart 1986, Burgner et al. 1992).
Steelhead are commonly described as either summer-run (summer steelhead) or winter-run
(winter steelhead), based on time and duration of spawning migration and state of sexual maturity at
the time of river entry. Summer steelhead enter fresh water between May and October, in a sexually
immature condition. After several months in fresh water, summer steelhead mature and spawn. Winter
steelhead enter fresh water between November and April with well developed gonads and spawn shortly
thereafter. Both summer and winter steelhead are found in some drainages, including the Rogue River
basin of southwest Oregon. The Illinois River, a tributary to the Rogue River (Fig. 1), is generally
considered to have only winter-run steelhead.
Illinois River winter steelhead were identified as being "at moderate risk of extinction" in a
report on Pacific salmon stocks at risk (Nehlsen et al. 1991). Declining catch of winter steelhead
from the Illinois River and public comment resulted in the imposition of no-take fishing regulations
for Illinois River steelhead by the Oregon Department of Fish and Wildlife (ODFW) in 1992
(M. Jennings). In response to indications that the population is declining, Oregon Natural Resources
Council, Siskiyou Regional Education Project, Federation of Fly Fishers, Kalmiopsis Audubon Society,
Siskiyou Audubon Society, Klamath/Siskiyou Coalition, Headwaters, The Wilderness Society, North Coast Environmental Center, Oregon Chapter of
The Sierra Club, and The National Wildlife Federation petitioned the National Marine Fisheries Service
(NMFS) to list the Illinois River winter steelhead as a threatened or endangered "species" (ONRC et al.
1992) under the U.S. Endangered Species Act (ESA or Act) of 1973 as amended (U.S.C. 1531 et seq.). This
report summarizes a review of the status of Illinois River winter steelhead conducted by the NMFS
Northwest Region biological review team.
KEY QUESTIONS IN ESA EVALUATIONS
Two key questions must be addressed in determining whether a listing under the ESA is
warranted:
- Is the entity in question a "species" as defined by the ESA?
- If so, is the "species" threatened or endangered?
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 Act 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 Act to
anadromous salmonid species, including steelhead (NMFS 1991). A more detailed description of this
topic appears in the NMFS "Definition of Species" paper (Waples 1991). The NMFS policy stipulates that
a salmon population (or group of populations) will be considered "distinct" for purposes of the Act if
it represents an.evolutionarily significant unit (ESU) of the biological species. An ESU is defined as a population
that (a) is reproductively isolated from conspecific populations and (b) represents an important
component in the evolutionary legacy of the species. Types of information that can be useful in
determining the degree of reproductive isolation include incidence of straying, rates of
recolonization, degree of genetic differentiation, and the existence of barriers to migration.
Insight into evolutionary significance can be provided by data on phenotypic and protein or DNA
characters; life-history characteristics; habitat differences; and the effects of stock transfers or
supplementation efforts.
Thresholds for Threatened or Endangered Status
Neither NMFS nor the U.S. Fish and Wildlife Service (USFWS), which share authority for
administering the ESA, has an official policy regarding thresholds for considering ESA "species" as
threatened or endangered. The National Marine Fisheries Service has published a nonpolicy document on
this topic (Thompson 1991). There is considerable interest in incorporating the concepts of
Population Viability Analysis (PVA) into ESA threshold considerations for Pacific salmon. However,
most of the PVA models require substantial life-history information that often will not be available
for Pacific salmon populations.
Therefore, NMFS considers a variety of information in evaluating the level of risk faced by an
ESU. Important factors include 1) absolute numbers of fish and their spatial and temporal
distribution; 2) current abundance in relation to historical abundance and current carrying capacity
of the habitat; 3) trends in abundance, based on indices such as dam or redd counts or on estimates of
spawner-recruit ratios; 4) natural and human-influenced factors that cause variability in survival
and abundance; 5) possible threats to genetic integrity (e.g., from
strays or outplants from hatchery programs); and 6) recent events (e.g., a drought or improvements in
mainstem passage) that have predictable short-term consequences for abundance of the ESU.
Hatchery Fish and Natural Fish
Because artificial propagation of Pacific salmonids has been widespread for many years, the
influence of hatchery fish needs to be considered in most ESA status reviews. NMFS policy stipulates
that in determining whether a population is "distinct" for purposes of the ESA, attention should focus
on "natural" fish, which are progeny of naturally spawning fish (Waples 1991). This approach directs
attention to fish that spend their entire life cycle in natural habitat and is consistent with the
mandate of the Act 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.
The decision to focus on natural fish is based entirely on ecosystem considerations; the
question of the relative merits of hatchery vs. natural fish is a separate issue. Fish are not
excluded from ESA consideration simply because some of their direct ancestors may have spent time in a
fish hatchery, nor does identifying a group of fish as "natural" as defined here automatically mean
that they are part of an ESU.
Once the natural component of a population has been identified, the next step is to determine
whether this population component is "distinct" for purposes of the ESA. In making this
determination, we used guidelines in the NMFS "Definition of Species" paper (Waples 1991). We
considered factors outlined in the section entitled "Effects of artificial propagation and other human
activities" to determine the extent to which artificial propagation may have affected the natural
fish, through either direct supplementation or straying of
hatchery fish. Thus, fish meeting the definition of "natural" adopted here could be excluded from ESA
considerations.
Threshold determinations also will focus on natural fish, on the premise that an ESU is not
healthy unless a viable population exists in the natural habitat.
PETITION TO LIST ILLINOIS RIVER WINTER STEELHEAD
This section summarizes claims made by the petitioners (ONRC et al. 1992) to support the
designation of the Illinois River winter steelhead as an ESU. Organization of this section, and
references to the criteria of Reproductive Isolation and Evolutionary Significance, follows that of
the petition. After discussing information relevant to each of these issues in the next section of
this status review, we evaluate the merits of the petitioners' arguments in the Discussion and
Conclusions section.
Reproductive Isolation
Geographic Isolation
North-south genetic differences--The petition cited Hatch (1990), who conducted
electrophoretic analyses on steelhead from several Oregon streams and found evidence for a genetic
difference between steelhead populations from northern vs. southern Oregon coastal drainages. The
petitioners argued that these genetic differences presumably reflect reproductive isolation. Hatch
identified Cape Blanco as a genetic break point and suggested that "there is a less than average amount
of straying between the populations north and south of this feature" (Hatch 1990, p. 33-34). The
petitioners pointed out that the mouth of the Rogue River is 43 km south of Cape Blanco.
Distance to Illinois River spawning grounds--The petitioners stated that steelhead migrate up
to 121 km up the Illinois River to spawn, which isolates them from other Rogue River basin steelhead
stocks.
Illinois River Falls--The petitioners proposed that navigating the natural falls at River
Kilometer (RKm) 64 may have been a selective factor in the evolution of the Illinois River winter
steelhead. They stated that prior to modification and ladder construction, stray steelhead "would not
arrive at the proper time nor have the persistence to get over the barrier" (ONRC et al. 1992, p. 4).
Distinctive Life History and Body Size Characteristics
Absence of half-pounders--The petitioners described
half-pounders as "a common life history
type found in winter and summer steelhead that spawn in tributaries to the middle and upper Rogue
River" (ONRC et al. 1992, p. 4). They contended that the absence of half-pounders in the Illinois
River supports the theory of genetic isolation of Illinois River winter steelhead.
Timing of peak spawning--The petitioners referenced Rivers (1964), who indicated that peak
spawning for Illinois River winter steelhead occurs 1 April, which he said was 2 weeks earlier than the
peak for the middle Rogue River and 2 weeks later than the peak for the Applegate River. The
petitioners cited timing of spawning as a heritable trait (Ricker.1972) and the importance of "run timing, emergence, and rearing patterns to streams that go dry or
become uninhabitable by mid-summer" (ONRC et al. 1992, p. 4).
Smolt age--Rivers (1964) was cited for describing the Illinois River winter steelhead as
having the longest freshwater phase of Rogue River basin steelhead stocks.
Age and body size at first spawning--The petitioners cited Rivers (1964), who concluded that
"at the time of first spawning, winter steelhead in the Illinois River were older and were heavier at a
given length than counterparts captured in the middle Rogue and in the Applegate River" (ODFW 1990, p.
34). The petition stated that "the larger body size of Illinois River adult steelhead may help them
jump the Illinois River Falls" (ONRC et al. 1992, p. 5).
Effects of Hatchery Fish
The petitioners referred to ODFW records to document a low incidence of straying of hatchery
steelhead into the Illinois River. The petition (ONRC et al. 1992, p. 5) stated that
Scale samples from 52 Illinois River steelhead caught during 1984-85 were all
interpreted as wild fish by ODFW....The Illinois River winter steelhead is the only
winter steelhead population known to be in compliance with the Wild Fish Policy because
of low straying rates of hatchery fish into the Illinois River.
Evolutionary Significance
Geographic Location
The petitioners described the Illinois River as "an interior valley in the southern fourth of
the steelhead species' range" (ONRC et al. 1992, p. 5). They reiterated Hatch's (1990) findings of
"phenotypic differences supporting a separation of steelhead south of Cape Blanco, Oregon" (ONRC et
al. 1992, p. 5).
Thermal Adaptation
The petitioners calculated population size for Illinois River winter steelhead from 1966 to
1990 using ODFW catch data. They contended that the population "historically demonstrated a high
level of productivity in an environment that appears extremely hostile to a cold water fish" (ONRC et
al. 1992, p. 5). They cited ODFW (1990, p. 34) who reported that "adaptations to survive warm water in
the Illinois River basin may be quite different than adaptations to survive in small tributaries of the
Rogue River close to the coast."
Spawning Distribution
"Widely distributed spawning populations located throughout the Illinois Basin ensure genetic
continuity and continued high productivity during natural environmental catastrophes" (ONRC et al.
1992, p. 5).
Anadromous Life History
"The anadromous life history is crucial to the steelhead's high degree of life history
diversity. Anadromy allows Illinois River winter steelhead to colonize streams where local
extinctions have occurred and also confers a competitive advantage through large body size and
increased fecundity" (ONRC et al. 1992, p. 5-6).
Population Trends
The petitioners cited a tenfold decline in angler catch of Illinois River winter steelhead
since 1971. They recognized that trends in catch may be affected by trends in angler effort but
believed that such a dramatic decline in effort was unlikely. They also estimated that Illinois River
winter steelhead survival has been below replacement level in 13 of 16 years (1971-86), with no
prospect for improvement in the near future. The petitioners interpreted
this consistent inability of the population to replace itself as evidence it is endangered according
to the framework of a draft policy statement by NMFS and USFWS (1980).
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