i

NOAA Technical Memorandum NMFS-NWFSC-37

Status Review

of Coastal Cutthroat Trout

from

Washington, Oregon,

and California

Orlay W. Johnson, Mary H. Ruckelshaus, W. Stewart Grant, F.

William Waknitz, Ann M. Garrett, Gregory J. Bryant, Kathleen

Neely, and Jeffrey J. Hard

Conservation Biology Division

Northwest Fisheries Science Center

National Marine Fisheries Service

2725 Montlake Blvd. E

Seattle, WA 98112-2097

January 1999

U.S. DEPARTMENT OF COMMERCE

William M. Daley, Secretary

National Oceanic and Atmospheric Administration

D. James Baker, Administrator

National Marine Fisheries Service

Rolland A. Schmitten, Assistant Administrator for Fisheries
ii
iii
iv
v
vi
vii
viii
ix
x
xi
xii
xiii

EXECUTIVE SUMMARY

This status review examines coastal cutthroat trout (Oncorhynchus clarki clarki) in

California, Oregon, and Washington to determine whether they face a risk of extinction if present

conditions continue. The National Marine Fisheries Service (NMFS) initiated this status review,

which was also requested by a 1997 petition seeking listing of all O. c. clarki in those three states

as threatened or endangered under the federal Endangered Species Act (ESA). The NMFS

decision to conduct this status review follows the agency’s announcement, in response to earlier

petitions and to general concerns about the status of Pacific salmon throughout the region, to

initiate ESA status reviews for all species and populations of anadromous salmonids, including

coastal cutthroat trout, in Washington, Idaho, Oregon, and California.

The ESA allows listing “distinct population segments” of vertebrates and named species

and subspecies. The policy of the NMFS on this issue for anadromous Pacific 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 the ecological or 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.

A team of NMFS scientists conducted this status review, which the ESA stipulates be

based on the best available scientific and commercial information. This Biological Review

Team (BRT) reviewed and evaluated information from federal, state, and tribal fisheries

agencies, as well as individuals.

The BRT did not as part of this review 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. The BRT did, however, draw conclusions about the risk of

extinction faced by ESUs under the assumption that present conditions will continue.

Umpqua River Coastal Cutthroat Trout

A status review of coastal cutthroat trout from the Umpqua River basin in southern

Oregon was conducted by the NMFS in 1994. The BRT for that review concluded that all lifehistory forms in the Umpqua River were part of the same ESU but was unable to reach a

conclusion on the ESU’s geographic extent. The BRT also concluded that the anadromous

portion of the ESU was precarious and that its loss would be an ESA concern; anadromy is based

(at least in part) on genetics and contributes substantially to the ESU’s ecological/genetic

diversity.

In July 1996, the NMFS published a final rule listing Umpqua River cutthroat trout as an

endangered species. However, in doing so, NMFS committed to reevaluate the status of the
xiv

species within 2 years. This current coastwide review of coastal cutthroat trout reevaluates

biological data on the status of the Umpqua River species and identifies Umpqua River coastal

cutthroat trout as part of a larger Oregon Coast ESU, which is evaluated as part of this review.

This review, however, does not completely resolve the Umpqua River ESU boundary question,

and the possibility that smaller ESUs should be recognized has not been excluded.

Difficulties in Reviewing Coastal Cutthroat Trout Status

Reviewing the status of coastal cutthroat trout was difficult because they are one of the

most biologically diverse and least-studied groups of West Coast salmonids. Two factors made

ESU determination and risk assessment for this group especially challenging:

• Relevant biological information on the subspecies is meager compared to data collected for

Pacific salmon because, as cutthroat trout are not a commercial species, much of the

information useful for their management and conservation is obtained only incidentally

during biological surveys for commercially caught Pacific salmon species.

• Coastal cutthroat trout express a wide diversity of life-history attributes. This diversity

includes several migratory pathways: They may migrate to estuaries and other marine

environments (a form known either as “anadromous” or “sea run”); they may remain in fresh

water (freshwater forms) as river/lake migrants or in upper headwater tributaries as

nonmigrants; or they may follow migratory pathways that combine these behaviors. Genetic

and environmental influences on these migratory pathways and life-history attributes are

poorly understood.

The BRT felt strongly that life-history forms in each ESU represent diverse genetic and

phenotypic resources important to its evolutionary ecology, and the BRT unanimously concluded

that each ESU include all of these life-history forms. Team members concurred that loss of any

individual life-history form could increase risk to the ESU as a whole.

Another challenging problem for the BRT was to evaluate the significance of various

migration barriers that separate the different life-history forms of coastal cutthroat trout in some

watersheds. The BRT was divided on whether populations above long-standing barriers (i.e.,

those that effectively preclude migration for hundreds or even thousands of years) should be

included in ESUs. The primary argument for inclusion centered on the fact that populations

above barriers are often most closely related to those below them; this close relationship makes it

unclear to which ESU above-barrier populations would belong if not to the ESU including

below-barrier populations. The argument for exclusion focused on the complete reproductive

isolation between the above- and below-barrier populations and, consequently, the different

evolutionary trajectories followed by these groups of populations. Only under very special

circumstances would the above-barrier populations be useful in recovery of the below-barrier

populations.

This problem also involved barriers that permit some one-way migration (i.e.,

downstream migration of smolts but not upstream passage of adults). The majority of BRT
xv

members believed that populations above these barriers should be included in ESUs. The basis

for this conclusion is two-fold: 1) populations above barriers may contribute demographically

and genetically to populations below them, even if the frequency of successful one-way migrants

per generation is low, and 2) populations above barriers may represent genetic resources shared

by populations below them (and thus may be a significant component of diversity for an ESU).

Coastal Cutthroat Trout ESUs

The BRT considered several possible ESU configurations for this subspecies based on

biogeographic, life history, and genetic information. After considerable discussion, a majority of

BRT members supported a scenario involving six ESUs: Puget Sound, Olympic Peninsula,

Southwestern Washington/Columbia River, upper Willamette River, Oregon Coast, and Southern

Oregon/California Coasts. Alternative scenarios considered at length by the BRT were 1) a

single ESU corresponding with the range of coastal cutthroat trout and 2) multiple ESUs

corresponding to small geographic units, such as major river basins. However, the BRT

ultimately concluded that available information best supported the scenario of six ESUs. These

six ESUs show strong similarities to ESUs designated for other species, especially coho

(O. kisutch) and chinook (O. tshawytscha) salmon, and steelhead (O. mykiss); however, there are

significant dissimilarities that reflect species differences in genetic structure and life-history

variation.

Figure ES-1 shows the six ESUs; descriptions follow.

1) Puget Sound ESU

This proposed ESU includes populations of coastal cutthroat trout that enter protected

marine waters in northwestern Washington; its boundaries correspond roughly with the Puget

Lowland ecoregion.

Life-history data indicate that coastal cutthroat trout from Puget Sound generally smolt at

a smaller size and younger age than those entering coastal marine waters. Genetic data indicate

that these populations are separated from those in southwestern Washington and farther south.

Populations in Puget Sound and Hood Canal and on the Olympic Peninsula are highly

heterogeneous genetically; nevertheless, some evidence exists for coherent genetic separation of

Olympic Peninsula populations from those in the eastern Strait of Juan de Fuca, northern Puget

Sound, and Hood Canal. Populations in Hood Canal and along the Strait of Juan de Fuca are

distinctive but show no clear evidence of a transition zone between Puget Sound and

southwestern Washington. There are genetic distinctions between populations from the upper

Nisqually River (a system in southern Puget Sound with strong glacial influences) and other

southern Puget Sound populations. Based primarily on these life-history and genetic patterns, the

BRT concluded that this ESU includes all streams in Puget Sound and the Strait of Juan de Fuca

west to, and including, the Elwha River. The northern boundary for this ESU is unclear, but
xvi

Figure ES-1. Proposed Evolutionarily Significant Unit (ESU) designations for cosatal cutthroat

trout.
xvii

unpublished data lend support to the hypothesis that this ESU extends into southern British

Columbia, including populations along eastern Georgia Strait north of Vancouver.

In general, this ESU’s boundaries reflect an ecoregion in which river drainages have

relatively high flows due largely to high precipitation, snow melt, and temperatures moderated

by the marine environment. The southern and western boundaries are similar to those previously

identified for chinook, coho, chum (O. keta), and pink (O. gorbuscha) salmon, and steelhead.

The northern boundary differs from the one for chinook and coho salmon (which does not extend

into Canada) and for pink, chum, and coho salmon (which does not include eastern Vancouver

Island).

2) Olympic Peninsula ESU

This proposed ESU includes coastal cutthroat trout in populations from the Strait of Juan

de Fuca west of the Elwha River and coastal streams south to, but not including, streams that

drain into Grays Harbor. The proposed boundaries of this ESU are similar to those for steelhead

and coho salmon. Support for this ESU relies primarily on the ecological distinctiveness of this

area, which is characterized by high precipitation, cool water temperatures, and relatively short

high-gradient streams entering directly into the open ocean.

Coastal cutthroat trout from this area are relatively large as smolts, and a higher

proportion appears to mature at first return from seawater than is the case in most Puget Sound

populations. Olympic Peninsula populations are genetically distinctive, but show a greater

similarity to populations in Puget Sound and Hood Canal than to those along the Strait of Juan de

Fuca east of the Elwha River.

Based primarily on these genetic data, a minority of the BRT concluded that populations

from the Olympic Peninsula should be considered part of a combined Puget Sound-Olympic

Peninsula ESU. Other BRT members pointed out that the Olympic Peninsula ESU may

represent a genetic transition zone between the Puget Sound and Southwestern Washington/

Columbia River ESUs.

3) Southwestern Washington/Columbia River ESU

The proposed boundaries of this ESU are similar to the Southwestern Washington/Lower

Columbia River ESU for coho salmon and extend upstream in the Columbia River to Celilo

Falls. Support for this ESU designation comes primarily from ecological and genetic

information. Ecological characteristics of this region include the presence of extensive intertidal

mud and sandflats, similarities in freshwater and estuarine fish faunas, and substantial

differences from estuaries north of Grays Harbor and south of the Columbia River. The coastal

cutthroat trout samples from southwestern Washington show a relatively close genetic similarity

to samples from the Columbia River.
xviii

A minority of the BRT supported a split of Columbia River from southwestern

Washington coastal cutthroat trout populations. Tagging and recovery data for chinook, coho,

and chum salmon indicate different marine distributions for fish from the two areas. The limited

dispersal ability of anadromous cutthroat trout may restrict genetic exchange among populations

in the two areas, which exhibit different physical estuarine characteristics. Also, an important

salmonid parasite, Ceratomyxa shasta, occurs in the Columbia River but has not been observed

in Willapa Bay or Grays Harbor. However, the majority of BRT members concluded that

available data did not provide compelling evidence for splitting populations along the

southwestern Washington coast from those in the Columbia River.

4) Upper Willamette River ESU

Cutthroat trout are one of only three species of anadromous Pacific salmonids that

historically occurred above Willamette Falls. Upper Willamette River populations of the other

two species (spring chinook salmon and winter steelhead) have been identified as separate ESUs

in previous status reviews, based on ecological factors, substantial genetic differences from other

Columbia River populations, and physical and hydrological conditions.

The upper Willamette River above the falls encompasses a large area with considerable

habitat complexity that evidently supports several different populations of coastal cutthroat trout.

Based on information provided by the Oregon Department of Fish and Wildlife, Willamette Falls

in its present configuration is a nearly complete barrier upstream and downstream in summer and

early fall to anadromous fish, including summer steelhead as well as coastal cutthroat trout. The

BRT concluded that the upper Willamette River has probably never supported a substantial

anadromous population of cutthroat trout, although freshwater forms are common. Upper

Willamette River coastal cutthroat trout exhibit a genetic structure consistent with the hypothesis

that the falls is a strong reproductive barrier between populations above and below it.

Ceratomyxa shasta in the Willamette River below the Marys River and high temperatures in the

lower Willamette River in summer and fall probably limit the survival of the very few migrants

known to drop over the falls. Although the populations above the falls are highly heterogeneous

genetically with several outlier populations, they form a somewhat coherent cluster of

apparently isolated and semi-isolated populations.

A number of factors—physical and genetic evidence of a migration barrier, habitat and

ecological differences above and below Willamette Falls, and the lack of anadromous

populations and prevalence of freshwater migratory forms above the falls—led the majority of

the BRT to conclude that coastal cutthroat trout above Willamette Falls should be considered a

separate ESU.

5) Oregon Coast ESU

Genetic data indicate marked genetic differences between coastal cutthroat trout from

coastal Oregon and those in the Columbia River and along the Washington coast. Samples of
xix

coastal cutthroat trout south of the Columbia River indicate a large heterogeneous group of

populations along the Oregon coast. Furthermore, several ecological differences exist between

rivers along the Oregon coast and those farther north. The Oregon coast is characterized by

relatively high precipitation, moderate temperatures, and short low-gradient streams with few

migration barriers. Tagging studies in Alaska and elsewhere indicate that anadromous cutthroat

trout follow shorelines when in seawater; thus, the known migratory patterns of this species are

consistent with the hypothesis that the Columbia River, which is several miles wide and relatively

deep at its mouth, is a migratory barrier between coastal populations in Oregon and Washington.

The proposed boundaries of this ESU are similar to the ESUs identified for coho and

chinook salmon and steelhead. The southern boundary of this proposed ESU is at Cape Blanco,

Oregon. Genetic data provide only weak evidence for a split between populations north or south

of Cape Blanco, but ecological data support it. The Cape Blanco area is a major biogeographic

boundary for many marine and terrestrial species and has been identified as an ESU boundary for

chinook and coho salmon and steelhead on the basis of strong genetic, life-history, ecological,

and habitat differences north and south of this landmark. Also, unpublished meristic data point

to a difference between coastal cutthroat trout populations north and south of Cape Blanco

(Williams unpubl. data).

6) Southern Oregon/California Coasts ESU

A majority of the BRT members concluded that populations of coastal cutthroat trout

from Cape Blanco south to the southern extent of the subspecies’ range represent a separate ESU.

Several members did not consider the genetic and ecological data strong enough to support this

split. However, as described above, meristic (and, to some extent, genetic) information lends

support for a separate coastal cutthroat trout ESU south of the major biogeographic boundary at

Cape Blanco. In addition, the limited dispersal capability of coastal cutthroat trout and anecdotal

evidence for marked differences in population dynamics for populations north and south of Cape

Blanco support a split at that landmark. Finally, the majority of river systems in this ESU are

relatively small with limited estuaries and heavily influenced by a maritime climate. Many of

these systems are characterized by physical and thermal barriers to movement by anadromous

fish; notable systems that lack such barriers are the Eel, Klamath, Rogue, and Trinity rivers.

Assessment of Extinction Risk

The ESA defines “endangered species” as “any species which is in danger of extinction

throughout all or a significant portion of its range.” “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 of whether a

species is threatened or endangered should be made on the basis of the best scientific information

available regarding the species’ status, after taking into consideration conservation measures

proposed or in place.
xx

One of the most challenging aspects of risk assessments for coastal cutthroat trout is the

scarcity of available information. This lack of data is far more pervasive than for other species of

Pacific salmonids. Current or historical abundance information, especially for adult coastal

cutthroat trout, is available for only a very small proportion of the known populations within any

ESU. In contrast to status reviews of the other species of Pacific salmonids, the BRT for coastal

cutthroat trout had to base its risk evaluations more heavily on abundance estimates for a small

number of populations spanning only a few years, on presence/absence data, and on professional

judgements by biologists familiar with coastal cutthroat trout in specific geographic regions.

Information on risks from hatchery-origin fish and on hybridization with steelhead and rainbow

(the freshwater form of O. mykiss) trout also is very limited for coastal cutthroat trout.

The BRT wrestled with a fundamental dilemma stemming from the lack of data, which

can result in two alternative conclusions:

• There is insufficient evidence to demonstrate that coastal cutthroat trout are at significant risk

of extinction

• There is insufficient evidence to demonstrate that coastal cutthroat trout are not at significant

risk of extinction

This dilemma existed for many of the coastal cutthroat trout ESUs. For some BRT

members, uncertainty about a given ESU’s status stemming from insufficient information and

from a collective sense among many local biologists that coastal cutthroat trout were in decline

led to a conclusion that there is a risk of extinction. For other BRT members, insufficient

information led to a conclusion that there is not significant risk. The BRT stressed that the latter

conclusion does not necessarily indicate that an ESU is healthy; rather, it may simply indicate

that there is insufficient information to demonstrate that it is not healthy.

Summary of BRT Risk Conclusions

• A majority of BRT members concluded the Puget Sound, Olympic Peninsula, and Southern

Oregon/California Coast ESUs are not presently in danger of extinction, nor are they likely to

become so in the foreseeable future. For each of these three ESUs, a minority of the BRT

believed there is a likelihood of endangerment in the foreseeable future.

• All BRT members agreed that the Oregon Coast ESU is not presently at risk of extinction,

but the team was evenly split on whether the ESU is likely to become endangered in the

foreseeable future.

• The BRT unanimously concluded that the Southwestern Washington/Columbia River ESU is

likely to become endangered in the foreseeable future. The conservation status of the ESU in

the upper Willamette River, a tributary of the Lower Columbia River, was not formally

evaluated by the BRT because available evidence indicates that few if any anadromous

coastal cutthroat trout are produced in this ESU.

A summary of the rationale for risk conclusions for each ESU follows.
xxi

Puget Sound ESU

The BRT noted with concern that there are few existing data relative to those for

steelhead and Pacific salmon concerning historical and present abundance of coastal cutthroat

trout in the Puget Sound ESU region. Anecdotal reports suggest relatively high abundance of

coastal cutthroat trout in northern Puget Sound and low abundance in southwestern Puget Sound

streams. There are some data indicating that juvenile coastal cutthroat trout are relatively well

distributed in the Skagit and Stillaguamish river basins and along the Strait of Juan de Fuca. The

BRT acknowledged that widespread habitat degradation and loss has occurred in the Puget

Sound region. This reduction in habitat capacity constitutes an important and ongoing risk to

coastal cutthroat trout that has not been well quantified.

Trend data for this ESU available to the BRT were from downstream migrant and adult

counts for a few streams. Apparent declines in downstream migrants in the Skagit River basin

may not accurately depict coastal cutthroat trout abundance—but may at best be rough indicators

of true trends—because the trap locations and dates trapped were designed to estimate coho

salmon smolt numbers. Increases in coastal cutthroat trout smolt numbers in some eastern Hood

Canal streams coincided with declines in coho salmon abundance, suggesting to the BRT that

interactions between these two species may be reducing the abundances of coastal cutthroat trout

in some streams. Historical estimates of smolt abundance were not available, so no definitive

conclusions about the risks to coastal cutthroat trout populations could be made from smolt count

data.

In addition to information about population sizes and trends in abundance for coastal

cutthroat trout in this ESU, the BRT considered another important risk factor—the potential loss

of life-history diversity. The anadromous life-history type in particular appears to be declining in

some streams. However, the BRT believed that risks to the ESU’s integrity and long-term

sustainability due to loss of life-history diversity were relatively low compared to those of the

other five coastal cutthroat trout ESUs, which have more streams with documented declines in

anadromous life-history types. The influence of hatchery coastal cutthroat trout in the Puget

Sound ESU is probably low compared to the scale of hatchery propagation of other Pacific

salmon.

A majority of the BRT members believed the Puget Sound ESU is not presently in danger

of extinction, nor is it likely to become so in the foreseeable future. A minority believed that the

ESU is likely to become endangered in the foreseeable future. The uncertainty underlying these

assessments was high: most BRT members reported certainty scores of 2 or 3 for their risk

evaluations. The BRT concluded that widespread, often irreversible, degradation of freshwater

and estuarine habitat has occurred, due to effects of development, logging, and agriculture.

Thus, extant habitat capacity is clearly lower than historical levels. A number of biologists

familiar with coastal cutthroat trout believe fishing mortality on cutthroat trout is an important

source of risk. The BRT expressed concern that historical and continuing reduction in habitat

quality, combined with very little information with which to assess status, led to great

uncertainty in evaluating risk for Puget Sound coastal cutthroat trout.
xxii

Olympic Peninsula ESU

The BRT had very little information to estimate population abundances for coastal

cutthroat trout in this ESU. The general impression from state and tribal fisheries biologists is

that juvenile coastal cutthroat trout are widely distributed in streams along the western Strait of

Juan de Fuca and northern Washington coast, and the BRT believed there are probably some

highly productive coastal cutthroat trout streams in this region. On the other hand, the BRT

acknowledged that ongoing habitat destruction, primarily from logging and associated activities

continue to be a source of risk to coastal cutthroat trout in many Olympic Peninsula streams.

The only quantitative data available to the BRT for this ESU were counts of downstream

migrants on tributaries of the Clearwater (1978-present), Dickey (1992-1994), and Hoko (1986-

1989) rivers and in Salt Creek along the Strait of Juan de Fuca (1998). The trends among

Clearwater tributaries were mixed. The BRT did not weigh increasing trends from the Hoko

River heavily in its risk determinations because these data are not current; the Dickey River

trends were also not weighed heavily because they are based on only 3 years of trapping

designed to estimate coho salmon production. It was difficult to interpret outmigrant data

because of a lack of smolt-to-adult survival estimates and because production declines may have

occurred before 1981, when earliest data collection began.

The BRT indicated that the risks to the Olympic Peninsula ESU from loss of life-history

diversity were relatively low. This ESU received a lower risk score for this source of risk than

did any other ESU. Risks associated with hatchery coastal cutthroat trout also are considered

low in this ESU.

A majority of the BRT concluded that the Olympic Peninsula ESU is not presently in

danger of extinction, nor is it likely to become so in the foreseeable future. One member

considered the ESU likely to become endangered in the foreseeable future. These risk

evaluations, however, must be considered in light of the very high uncertainty expressed by the

BRT. Certainty scores for this risk assessment were the lowest of all of the cutthroat trout ESUs,

with most of them 1 or 2. The BRT believed that there are indications of productive cutthroat

trout habitat to support this ESU, but information was not available to confirm such a possibility.

Continuing habitat degradation throughout the region was a significant source of concern to the

BRT.

Southwestern Washington/Columbia River ESU

According to the Washington Department of Fish and Wildlife, the southwestern

Washington-Lower Columbia River region historically supported healthy and highly productive

coastal cutthroat trout populations. Coastal cutthroat trout, especially the freshwater forms, may

still be widely distributed in most river basins in this region, although probably in numbers lower

than historical population sizes. Severe habitat degradation throughout the Lower Columbia

River area has contributed to dramatic declines in anadromous coastal cutthroat trout populations

and two near extinctions of anadromous runs in the Hood and Sandy rivers. The BRT was
xxiii

concerned about the extremely low population sizes of anadromous cutthroat trout in Lower

Columbia River streams indicated by low incidental catch in salmon and steelhead recreational

fisheries and low trap counts in a number of tributaries throughout the region. In contrast, local

biologists told the BRT that freshwater forms of coastal cutthroat trout are widespread in streams

throughout the region.

In the southwestern Washington portion of this ESU, trends in anadromous adults and

outmigrating smolts are all declining. Returns of both naturally- and hatchery-produced coastal

cutthroat trout in almost all Lower Columbia River streams have been declining markedly for the

last 10 to 15 years.

A significant risk factor for coastal cutthroat trout in this ESU is reduction in life-history

diversity. The limited information available suggests that, in many streams, freshwater forms of

coastal cutthroat trout are widely distributed and in high abundances relative to anadromous

cutthroat trout in the same stream. The BRT believed that smolt production by freshwater forms

does occur, but that it has not resulted in demonstrably successful reestablishment of anadromous

forms. Habitat degradation in stream reaches accessible to anadromous cutthroat trout and poor

ocean and estuarine conditions probably have combined to severely deplete this life-history form

throughout the Lower Columbia River Basin. Without the appropriate freshwater and estuarine

habitat for expression of the anadromous life history, a greater risk of extinction may occur. The

significance of this reduction in life-history diversity to the integrity of the ESU and the

likelihood of its long-term persistence were major sources of concern to the BRT.

Negative effects of hatchery coastal cutthroat trout may be contributing to the risks facing

natural coastal cutthroat trout in this ESU. The Lower Columbia River tributaries are the only

streams in Washington still receiving hatchery-origin coastal cutthroat trout, although the total

numbers of released hatchery fish have been substantially curtailed recently. The BRT

emphasized that the ultimate effects of hatchery fish depend on the relative sizes of hatchery and

natural populations, the spatial and temporal overlap of hatchery and natural fish throughout their

life cycles, and the actual extent to which hatchery fish spawn naturally and interbreed with

naturally produced fish. In addition, the extent to which natural coastal cutthroat trout are

incidentally harvested in fisheries targeting hatchery coastal cutthroat trout and other salmonids

also affect the magnitude of the risks to coastal cutthroat trout due to hatchery fish.

The BRT was unanimous in concluding that the Southwestern Washington/Columbia

River ESU was likely to become endangered in the foreseeable future. Certainty scores ranged

from 2 to 4; although these scores reflect only a moderate degree of certainty regarding the risk

assessment, they were on average higher than for any other ESU. The BRT was especially

concerned about the widespread declines in abundance and small population sizes of anadromous

cutthroat trout throughout the Lower Columbia River. The severe reductions in abundance of

this life-history form could have deleterious effects on the ability of this ESU to recover from

widespread declines. Reductions in the quantity and quality of nearshore ocean, estuarine, and

riverine habitat have probably contributed to declines, but the relative importance of these risk

factors is not well understood. The BRT was encouraged by recent steps taken by the states of
xxiv

Washington and Oregon to reduce mortality in this ESU due to directed and incidental harvest of

coastal cutthroat trout.

Upper Willamette River ESU

The conservation status of this ESU was not formally evaluated by the BRT. Since few

anadromous cutthroat trout are produced in this ESU, the U.S. Fish and Wildlife Service has

jurisdiction for these populations.

Oregon Coast ESU

Coastal cutthroat trout in the Oregon coastal region occur mostly in small populations

that are relatively widely distributed. Most of the abundance information considered by the BRT

for this ESU was for juveniles and smolts, with the prominent exception of adult counts at

Winchester Dam on the North Umpqua River. In general, the BRT was encouraged by the

numbers of juveniles in coastal streams with relatively large basins. These data are available for

only the last 2 years, however, so it is not known how well these juvenile counts translate into

adult abundances or longer-term population trends.

Conflicting information about the abundance and distribution of coastal cutthroat trout in

the South Umpqua River basin suggested to the BRT that there is insufficient information to

determine the status of coastal cutthroat trout in that drainage. The numbers of adults returning

to the North Umpqua River have been critically low in recent years (5-year geometric mean = 18

fish), although the last 3 years have produced counts of 79, 81, and 135 (through November 15,

1998) at Winchester Dam on the North Umpqua River. The BRT noted that widespread habitat

degradation due to logging, road construction, and development along coastal streams probably

constitutes a significant reduction in habitat capacity relative to historical conditions.

Smolt production in two small drainages (Cummins and Tenmile creeks) in central

Oregon has shown an increasing trend over the past 7 years. All other streams on the Oregon

coast for which data were available are experiencing moderate declines in adults and juveniles.

In some areas, declines may have occurred primarily in anadromous cutthroat trout populations,

and the BRT was concerned about such reductions throughout this ESU. The BRT believed risks

associated with possible reductions in historical connections among streams by migratory coastal

cutthroat trout could be a significant threat to the ESU.

Risks due to interactions with hatchery coastal cutthroat trout are probably moderately

low in this ESU. Nevertheless, widespread releases of Alsea River hatchery broodstock in

Oregon coastal streams have stopped only recently. Hybrids between coastal cutthroat trout and

O. mykiss were detected in genetic samples from the Coquille River Basin and a few other

streams in this ESU. Some degree of hybridization between O. mykiss and coastal cutthroat trout

may occur naturally without the direct influence of hatchery-origin fish. However, risks to

coastal cutthroat trout populations due to hybridization may increase if either changes in habitat
xxv

conditions or an increase in the abundance of hatchery-origin O. mykiss increase the frequency of

natural hybridization or change its fitness consequences.

All BRT members agreed the Oregon Coast ESU is not presently at risk of extinction.

However, the BRT was evenly split in determining whether or not the ESU is likely to become

endangered in the foreseeable future. The certainty in this assessment was fairly low: the

certainty scores were mostly 2 or 3. The BRT was concerned about habitat degradation that

continues within this region, and the scarcity of abundance information for major drainages

limited the BRT’s efforts to conduct a risk evaluation. Hatchery records indicate that the Alsea

River coastal cutthroat trout stock was released widely in streams throughout the Oregon coastal

region. Recent reductions in releases of hatchery-origin coastal cutthroat trout and coho salmon

fry, coupled with a statewide catch-and-release recreational fishery policy for “wild” coastal

cutthroat trout, may have reduced risks associated with those factors. The BRT noted that

reduced nearshore ocean habitat quality is probably a significant threat to coastal cutthroat trout

in this region, but quantifying those effects on coastal cutthroat trout abundance is very difficult.

Finally, the BRT was concerned about incidental mortality of coastal cutthroat trout in this ESU

due to fishing pressure on Pacific salmon and steelhead.

Southern Oregon/California Coasts ESU

Coastal cutthroat trout in this ESU are thought to be widely distributed in many small

populations. Two possible exceptions are populations in the Rogue and Smith river basins,

where abundance may be comparatively large. Population sizes are thought to be relatively

small in other streams throughout this region, in part because it is the southern limit of this

subspecies. The BRT believes that severe habitat degradation has occurred in this region,

primarily due to activities associated with agriculture, flood control, logging, road construction,

and some local development that have contributed to a reduction in habitat capacity relative to

historical levels. In addition, seasonal dewatering of stream mouths occurs naturally in Northern

California, sporadically blocking access to the sea for anadromous fish in those streams. Also,

large water withdrawals in several of the larger coastal river basins (e.g., the Rogue, Klamath/

Trinity, and Eel rivers) and several of the smaller coastal rivers have reduced the quantity and

quality of the remaining riverine and estuarine environments in this ESU.

Biologists familiar with this region believe, and anecdotal evidence suggests, that major

declines in coastal cutthroat trout populations have occurred since historical times, but that some

populations appear to have been relatively stable or increasing. The data available to the BRT

indicate increasing short-term trends in smolt abundance in Mill Creek as well as increasing

short-term trends in adult abundance in the lower Klamath River tributaries and its estuary and in

the Smith River Basin. Exceptions include recent declines in the incidence of coastal cutthroat

trout in Redwood Creek.

Reductions in the anadromous form of coastal cutthroat trout are not thought to be a

significant source of risk to the overall ESU. Although declines in some anadromous runs have
xxvi

occurred, there was no evidence presented to the BRT that these declines have occurred

throughout a significant portion of the ESU.

Risks due to interactions with hatchery coastal cutthroat trout are probably low in this

ESU. Other risks the BRT noted for coastal cutthroat trout in this region were possible

deleterious interactions with naturally occurring or hatchery-derived coho salmon and steelhead,

and incidental catch of coastal cutthroat trout in sport fisheries targeting steelhead and coho

salmon. The BRT was encouraged by recent changes in harvest regulations aimed at reducing

risks to natural trout from direct and indirect harvest mortality.

A majority of the BRT believed that the Southern Oregon/California Coasts ESU is not

presently in danger of extinction, nor is it likely to become so in the foreseeable future. A

minority concluded that the ESU was likely to become endangered in the foreseeable future.

Most BRT members indicated their risk evaluations were associated with a low level of certainty

(scores ranged from 1 to 4, but most members indicated a score of 2). As in considerations of

many other ESUs for coastal cutthroat trout, the BRT was hindered here by the scarcity of

abundance information for this ESU. The BRT emphasized that continuing threats to the quality

of freshwater and estuarine habitat for coastal cutthroat trout in this region are sources of

concern.
xxvii

ACKNOWLEDGEMENTS

This document represents the combined efforts of hundreds of people who provided

information to the National Marine Fisheries Service (NMFS), attended Pacific Salmon

Technical Biological Committee, Co-Manager, and Biological Review Team (BRT) meetings,

and answered seemingly endless questions from the authors and BRT members.

Collection of information used in this coastwide status review began with the Umpqua

River Cutthroat Trout status review, which is updated here. Many biologists from the Umpqua

River region in Oregon kindly provided us with updated information, data, opinions, field

observations, and advice, particularly David Loomis, District Biologist at the Roseburg Oregon

Department of Fish and Wildlife (ODFW) District office; Jeff Dose from the United States

Forest Service (USFS) Umpqua National Forest Supervisor’s Office; Elijah Waters from the

Roseburg Bureau of Land and Management District office; and Frank Bird and Craig Burns from

the Roseburg NMFS Northwest Regional Office. Other ODFW biologists who provided

assistance with tissue collection or other information include Robert Buckman, Mark Chilcote,

Todd Confer, Robert Hooton, Steve Johnson, Kathryn Kostow, and Paul Reimers. Dr. Paul

Spruell of the University of Montana and David Teel of the Northwest Fisheries Science Center

(NWFSC) also helped with collection of Oregon tissue samples. Jerry Winterbotham provided

an historical perspective on artificial propagation in the Umpqua River basin and fascinating

films of cutthroat trout.

In Washington, biologists who provided information, sample collection, and analysis

included Jim Ames, Bruce Baker, Wolf Damers, Howard Fuss, Pat Hanratty, Jay Hunter, Thom

Johnson, Curt Kraemer, Stevan Phelps, Dan Rawding, Bruce Sanford, David Seiler, and Tim

Tynan from the Washington Department of Fish and Wildlife (WDFW); Gary Graves from the

Northwest Indian Fisheries Commission (NWIFC); and Robert Furstenberg and Jim Mitilla from

the King County Surface Water Management Division. Special thanks are due Dr. Pat Trotter

for information, discussions, and insights regarding cutthroat trout.

In California, Dan Gale from Yurok Tribal Fisheries and Eric Gerstung from the

California Department of Fish and Game (CDFG) provided helpful interpretation and data.

We also wish to thank those who reviewed drafts of this and related documents, including

Drs. Eric Loudenslager, Humboldt State University; Fred Allendorf and Paul Spruell, University

of Montana; Jason Dunham, Oregon State University, and Robert Gresswell, U.S. Geological

Survey, Corvallis, Oregon. Co-manager reviews were provided by the CDFG, ODFW, WDFW,

NWIFC, and U.S. Fish and Wildlife Service (USFWS).

At the NWFSC, we are grateful to Paul Aebersold, Eric Iwamoto, Delia Patterson and

David Teel for alloyzme analysis. Also significant contributions in the compilation, analysis, and

editing of data were made by Tod McCoy, Cameron Fisher, Martha Burdick, Sue Joerger, and
xxviii

Kathleen Jewett. At the NMFS Northwest Regional Office in Portland, special thanks to James

Lynch and Garth Griffin for assistance in data collection and coordination.

The BRT for coastal cutthroat trout consisted of the following members from NWFSC:

Peggy Busby, F. William Waknitz, and Laurie Weitkamp, and Drs. Stewart Grant, Jeffrey Hard,

Robert Iwamoto, Orlay Johnson, Conrad Mahnken, Mary Ruckelshaus, Michael Schiewe, Robin

Waples, and John G. Williams; from the NMFS Northwest Region, Jim Lynch; from the USFS,

Dr. Gordon Reeves; from the USFWS, Dr. Donald Campton; from the NMFS Southwest

Fisheries Science Center, Tommy Williams; and from the NMFS Southwest Region, Greg

Bryant and Craig Wingert.
1

INTRODUCTION

The U.S. Endangered Species Act (ESA) is intended to conserve threatened and endangered species in their native habitats. The ESA allows listing of named species, subspecies, and

distinct vertebrate populations segments. According to National Marine Fisheries Service

(NMFS) policy, a salmonid population or group of populations is considered “distinct” and a

“species” under the ESA if it represents an evolutionarily significant unit (ESU) of the biological

species.

In response to earlier petitions for ESA listing of a variety of salmonid species and to

more general concerns about the status of Pacific salmon throughout the Pacific coast, NMFS

(1994) announced that it would initiate ESA comprehensive status reviews for all species of

anadromous salmonids in the Pacific Northwest. This proactive approach was intended to facilitate more timely, consistent, and comprehensive evaluation of the ESA status of Pacific salmonids than would be possible in a series of reviews of individual populations. Since 1994, the

Northwest Fisheries Science Center (NWFSC) has conducted a series of status reviews to identify ESUs in these species and evaluate their risk of extinction. These status reviews include coho

salmon (Oncorhynchus kisutch) (Weitkamp et. al. 1995), pink salmon (O. gorbuscha) (Hard et

al. 1996), steelhead (the sea-run form of O. mykiss) (Busby et al. 1996), chum salmon (O. keta)

(Johnson et al. 1997), sockeye salmon (O. nerka) (Gustafson et al. 1997), and chinook salmon

(O. tshawytscha) (Myers et al. 1998). This review of coastal cutthroat trout (O. clarki clarki) is

the final coastwide review in this series.

This status review also addresses a petition received by NMFS on December 5, 1997,

from the Oregon Natural Resources Council (ONRC) and others (listed in “Summary of Coastal

Cutthroat Trout Petition,” p. 5) to “list the sea-run cutthroat trout as threatened or endangered

throughout its range in the states of California, Oregon, and Washington” (ONRC 1997, p. 2).1

A third purpose of this status review is to update information gathered for an earlier status

review of Oregon’s Umpqua River coastal cutthroat trout (Johnson et al. 1994), which was

initiated in response to a petition to NMFS by the ONRC, the Wilderness Society, and the

Umpqua Valley Audubon Society (ONRC et al. 1993) to list the North and South Umpqua River

sea-run cutthroat trout as a threatened or endangered species under the ESA. NMFS accepted the

petition and conducted a status review, concluding that coastal cutthroat trout in the Umpqua

River basin did constitute an ESU (Johnson et al. 1994). On August 9, 1996, NMFS issued a

final ruling that listed the Umpqua River coastal cutthroat trout as an endangered species under

the ESA (61 Fed. Reg. 41514). However, at the time of this determination, NMFS indicated that

it would reconsider this determination in 2 years or as new scientific information became available (61 Fed. Reg. 41521). Consequently, the portion of this status review that pertains to

1 “Sea-run cutthroat trout,” one of several common names for O. c. clarki and the name used in the

petition, refers only to one life-history form in the subspecies (fish that migrate to seawater). This report

uses coastal cutthroat trout (or cutthroat trout) as the common name for this subspecies (see

 “Terminology,” p. 6).
2

Umpqua River coastal cutthroat trout will focus on new information developed for this ESU

since the 1994 status review.

Scope and Intent of the Present Document

This document reports results of the comprehensive ESA status review of all life-history

forms (both anadromous and nonanadromous) of coastal cutthroat trout from Washington,

Oregon, and California. To provide a context for evaluating U.S. populations of coastal cutthroat

trout, biological and ecological information for coastal cutthroat trout in British Columbia and

Alaska were also considered. Therefore this review encompasses, but is not restricted to, contiguous U.S. sea-run populations identified in petitions for coastal cutthroat trout received by

NMFS in 1997.

Because the ESA stipulates that listing determinations should be made on the basis of the

best available scientific and commercial information, NMFS formed a team of scientists with

diverse backgrounds in salmonid biology to conduct this review. This Biological Review Team

(BRT) reviewed and evaluated scientific information compiled by NMFS staff from published

and unpublished literature. Information was also considered that was presented at a series of

public meetings in 1997 and 1998 in Arcata, California; Gleneden Beach, Corvallis, Portland,

and Roseburg, Oregon; and Seattle and Olympia, Washington. In addition, the BRT reviewed

technical information submitted to the ESA administrative record.

Key Questions in ESA Evaluations

In determining whether a listing under the ESA is warranted, two key questions must be

addressed:

1. Is the entity in question a “species” as defined by the ESA?

2. If so, is the species threatened or endangered?

These two questions are addressed in “Information Relating to the Species Question”

(p. 21) and “Assessment of Extinction Risk” (p. 135). 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) overutilization 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.
3

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 approaches for considering vertebrate populations. 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 coastal cutthroat

trout and steelhead (NMFS 1991). A more detailed discussion of this topic appeared in the

NMFS “Definition of Species” paper (Waples 1991a,b). NMFS policy stipulates that a salmon

population (or group of populations) will be considered “distinct” for purposes of the ESA if it

represents an ESU of the biological species. An ESU is defined as a population that 1) is

substantially reproductively isolated from nonspecific 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—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.

For each of the two criteria (reproductive isolation and evolutionary legacy), NMFS

policy advocates a holistic approach that considers all types of available information as well as

their strengths and limitations. Important types of information to consider for reproductive

isolation 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. Isolation does not

have to be absolute, but it must be strong enough to permit evolutionarily important differences

to accrue in different population units.

The key question with respect to the evolutionary legacy criterion is this: Would

extinction of the population represent a significant loss to the ecological/genetic diversity of the

species? Again, a variety of types of information should be considered. Phenotypic and lifehistory 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 analyses 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.
4

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,b). 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, transfers of fish from one area to another 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 lifehistory characteristics such as smolt age, migration, and spawn timing. Second, artificial

propagation poses risks to natural populations that may affect their risk of extinction or

endangerment (see “Assessment of Extinction Risk,” p. 135). 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, for the most part, 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 further in this document.

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 considered a
5

variety of information in evaluating the level of risk faced by an ESU. Important considerations

included: 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 recruit-to-spawner

ratios; 4) natural and human-influenced factors that cause variability in survival and abundance;

5) possible threats to genetic integrity (e.g., selective fisheries and interactions between hatchery

and natural fish); and 6) recent events (e.g., a drought or a change in management) that have

predictable short-term consequences for abundance of the ESU. Additional risk factors, such as

disease prevalence or changes in life-history traits, may also be considered in evaluating risk to

populations.

According to the ESA, the determination of whether a species is threatened or endangered

should be made on the basis of the best scientific information available regarding its current

status, after taking into consideration conservation measures that are either proposed or currently

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 we

did not consider. 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 NMFS Northwest and

Southwest Regional Offices in making listing recommendations.

Summary of Coastal Cutthroat Trout Petition

On December 5, 1997, NMFS received a petition to list what petitioners called sea-run

cutthroat trout (O. c. clarki) along the coasts of California, Oregon, and Washington under the

ESA. The petitioners were the ONRC, Coast Range Association, Native Fish Society, Northwest

Ecosystem Alliance, Save the West, Siskiyou Regional Education Project, Siskiyou Audubon,

Trout Unlimited of California, Western Ancient Forest Campaign, Salmon Defense Association,

Salmon Forever, California Sportfishing Alliance, Oregon Wildlife Federation, Clark-Skamania

Fly Fishermen, and the Washington Rivers Council. A summary of their petition follows.

The biological information in the ONRC et al. (1997) petition consists of two short

sections that summarize an extensive 38-page status review of O. c. clarki written by a private

fisheries consultant, Patrick C. Trotter. From data presented in Trotter’s status review, the

petitioners concluded that coastal cutthroat trout abundance was reduced from historic levels

across the subspecies range, especially in the Willamette River and the Lower Columbia River

on both the Oregon and Washington sides. They believe that available data show that abundance

of “wild” populations is “dangerously low” in these two rivers.

The petitions asserted that available data indicate natural coastal cutthroat trout

populations along the California and Oregon coasts are at “seriously low levels” and “in danger
6

of becoming threatened or endangered.” Exceptions to this scenario are populations in the Smith

and Winchuck rivers on the California-Oregon border, which the petitioners asserted are “more

robust than any of those around them.”

The petitioners also concluded that the only “healthy populations” of O. c. clarki along

the West Coast are north of the Snohomish River in Puget Sound, Washington.

Terminology

Coastal cutthroat trout are the least studied of the seven Oncorhynchus species native to

the Pacific Northwest. Both sport and scientific literature often do not differentiate coastal

cutthroat trout from other species of salmonids (especially steelhead, the sea-run form of O.

mykiss) and simply categorize them as “trout” or “other fish.” Another difficulty is that these

sources of information often refer to coastal cutthroat trout with a variety of confusing local

names, including “harvest” (perhaps most common historically), “blueback,” “salmon,”

“steelhead cutthroat,” and “sea” trout (Schultz 1936, Roth 1937, Clemens and Wilby 1946).

In fresh water, the subspecies has often been simply identified as “trout,” but also as “native,”

“mountain,” “speckled,” or “brook” trout (Behnke 1972, 1992).

Because O. clarki is a polytypic species (Allendorf and Leary 1988; see also the “Life

History” section, p. 38) with different life-history forms that are often difficult or impossible to

distinguish, even the recent biological literature can be confusing. Several life-history forms

have been identified (see Trotter 1989) (Fig. 1), with a variety of regional names. For example,

coastal cutthroat trout observed in rivers have been identified as “resident,” “fluvial,” “adfluvialfluvial,” “river-migrating,” and “potamodromous” (Trotter 1989, 1991). However, “resident”

and “fluvial” have also been used to refer only to trout that inhabit upper headwater tributaries

and are considered “nonmigrants.” “Potamodromous” has been used to mean all freshwater

forms (Northcote 1997b) or any of those migrating within river (Tomason 1978). Also, although

all life-history forms of the subspecies O. c. clarki may possess the ability to go to sea and could

be considered anadromous, “sea-run cutthroat trout” usually refers only to fish in the subspecies

that regularly enter seawater. Coastal cutthroat trout also migrate from sea water to fresh water

not only to spawn but also for winter refuge and perhaps to feed. For this subspecies,

“amphidromous” (Stearley 1992, Williams et al. 1997a) is more scientifically correct than

“anadromous.” However, “anadromous” has broad general acceptance in the scientific

community, and we will use it in this document to describe coastal cutthroat trout migrating

between fresh water and sea water.

This document uses a simplified and consistent terminology for the subspecies and its

life-history forms (Fig. 1). The entire subspecies (all life-history forms) will be referred to as

coastal cutthroat trout (or simply cutthroat trout). Fish that migrate to sea water (estuary or open

ocean) will be termed sea run or anadromous. Fish that do not enter sea water are freshwater

forms, which may be migrants within river systems (riverine) or lake systems (lacustrine), or

nonmigrants moving only short distances within headwater tributaries. We have avoided the
Figure 1. Terminology of coastal cutthroat trout life-history forms used in this document and a description of the

and behaviors (adapted from Garrett 1998).
8

terms “resident,” “fluvial,” and “potamodromous” due to their ambiguity. Our terminology is

only a general guide as fish from any life-history form may, under the right set of circumstances,

become any other form. (See the “Life History “ section, p. 38, for a detailed description of these

life-history forms).

Another source of confusion from the literature arises from the use of the terms “wild

fish” and “natural fish.” In a number of management contexts, it is useful to distinguish fish

returning to a river based on their origin (e.g., offspring of parents from the local stream, from a

different stream, or from a hatchery) and whether they spawn naturally in available habitat or in a

hatchery. Different state and tribal entities have very different definitions for these terms (WDF

et al. 1993, Kostow 1995), so, to avoid confusion, this document uses a simplified and consistent

terminology for the origin and spawning location of coastal cutthroat trout. We use natural to

describe those fish produced by parents spawning in a river or lake rather than in a controlled

environment (such as a hatchery). Natural fish may include what are sometimes called wild fish;

wild in that usage usually refers to fish native to a stream and naturally spawning with little or no

hatchery ancestry. However, because local and regional interpretations of wild fish vary, we

avoid using the term in this status review. (See “Assessment of Extinction Risk,” p. 135, for

discussion of natural fish in the context of risk evaluations).

General Biology

Coastal cutthroat trout are found in the coastal plains of western North America from

southeastern Alaska to northern California (Trotter 1989) (Fig. 2). They belong to the same

genus as Pacific salmon and steelhead, but are generally smaller, rarely overwinter in the sea, and

do not usually make extensive oceanic migrations. Unlike Pacific salmon, coastal cutthroat trout

are iteroparous rather than semelparous, and adults have been known to spawn each year for

more than 6 years (Trotter 1989).

Various phylogenies or evolutionary histories of coastal cutthroat trout have been

proposed (e.g., Stearley and Smith 1993, Behnke 1992, 1997). Based upon fossil records,

Stearley (1992) and Stearley and Smith (1993) suggested that trout diverged from a common

salmonid ancestor somewhere in eastern Asia, probably more than 6 million years ago. Behnke

(1992, 1997) suggested cutthroat and rainbow trout were native to western North America and

diverged from a common “trout” ancestor somewhere in what is now the Snake/Columbia River

Basin (Fig. 3) at the beginning of the Pleistocene Era, approximately 2 million years ago.

Behnke (1997) argued that in the middle of the Pleistocene Era, approximately 1 million years

ago, the cutthroat trout group diverged again into a coastal group (presently O. c. clarki) with a

characteristic 68- or 70-chromosome karyotype set and an interior group (presently the westslope

cutthroat trout group, O. c. lewisi) with a characteristic 66-chromosome set. The coastal group

has essentially remained intact, colonizing coastal rivers from northern California to Prince

William Sound in Alaska. The interior group evidently diverged again into a third component

with a 64-chromosome set. This group contained two isolated groups: the Lahontan cutthroat
9

Figure 2. Range of coastal cutthroat trout (Oncorhynchus clarki clarki) (shading on coast) and of

13 interior subspecies (O. c. subspp.) (shading inland). Framed area represents

Umpqua River Basin.
10
11

trout in the Lahontan Basin of the western Rocky Mountain range (O. c. henshawi), and the

Yellowstone cutthroat trout in the Snake River Basin (O. c. bouvieri).

Based upon this evolutionary scenario, Behnke (1992, 1997) proposed 14 extant

subspecies of O. clarki grouped into what he describes as four “major” subspecies (coastal,

westslope, Lahontan, and Yellowstone cutthroat trout). These subspecies have a genetic

divergence time of more than 500,000 years, while what Behnke calls the 10 “minor” subspecies

were recently derived from the Lahontan or Yellowstone ancestors (Behnke 1992, 1997). The

coastal subspecies occurs in the coastal rainforests of North America and east to the Cascade

crest. The interior subspecies have not successfully penetrated the coastal mountains and

generally remain in the northern river basins of the western Rocky Mountains.

The coastal subspecies differs from other cutthroat trout in a variety of ways. For one,

O. c. clarki has a karyotype (2n) of 68 (Gold et al. 1977) or 70 (Simon 1963, 1964, Simon and

Dollar 1964) that is unique among cutthroat trout subspecies (Simon and Dollar 1964, Gold et al.

1977, Loudenslager and Thorgaard 1979, Thorgaard 1983, Behnke 1992), as well as

several unique alleles detected by protein electrophoresis (Leary et al. 1987, Allendorf and Leary

1988). Phenotypically, coastal cutthroat trout differ from all other trout by their profusion of

small- to medium-sized spots of irregular shape (Behnke 1992). In addition, they do not develop

the coloration associated with interior cutthroat trout. Further, while at sea and during seaward

migrations, this coloration and spotting are obscured by the silvery skin color common to

anadromous salmonids. At maturity, freshwater life-history forms of coastal cutthroat trout tend

to be darker, with a “coppery or brassy” sheen (Behnke 1992).

The life history of coastal cutthroat trout may be the most diverse of any Pacific salmonid

(Northcote 1997a; also see “Life History” section, p. 38). Their populations show a bewildering

diversity in size and age at migration, timing of migrations, age at maturity, and frequency of

repeat spawning. Part of this diversity reflects the way individual fish can move between

feeding, refuge, and spawning areas. Even populations where the vast majority of fish are

anadromous may have members that do not migrate to sea every year. In other populations,

some coastal cutthroat trout simply remain in headwater tributaries, while others may migrate

within rivers or lakes and return to headwater tributaries only to spawn. Some lake forms remain

in the lakes for their entire life cycle, spawning in shallow inlets or outlets (e.g., Crescent Lake,

Washington) (reviewed in Trotter 1989, 1997; Behnke 1992, 1997; Northcote 1997a).

Historically, interior and coastal cutthroat trout subspecies represented one of the most

broadly distributed salmonid species in western North America (Behnke 1979, 1992). Interior

cutthroat trout were often the only salmonid present (sometimes the only fish) in many lakes and

streams throughout the interior American west, and they were far more broadly distributed than

steelhead, rainbow trout, or other salmonids (Behnke 1979, 1992). In recent years these interior

subspecies have been precipitously replaced by rainbow trout or other introduced species in

many parts of their range (Gresswell 1988, Young 1995). Perhaps most destructive was the

widespread release of hatchery rainbow trout (O. mykiss) throughout the native range of interior

cutthroat trout (Gresswell 1988, Young 1995). The two species readily hybridize, often to the

extreme detriment of O. clarki, and it has been estimated that “just within the last century
12

perhaps 99 percent of the unique cutthroat strains of interior drainages have been lost forever”

(Willers 1991, p. 10). Behnke (1988, p. 1) estimated that “in less than 100 years after the first

[United States] settlements in the West, the cutthroat trout vanished from most of its vast range.”

This hybridization with rainbow trout, habitat degradation, and other factors have caused many

of these interior subspecies to decline in numbers to the extent that they are now protected by

state and federal endangered species legislation (Table 1) (Johnson 1987).

Some authors have suggested that coastal cutthroat trout are the healthiest subspecies of

cutthroat trout because they have experienced the least amount of habitat destruction,

hybridization with introduced species, or overfishing (reviewed in Pauley et al. 1989, Trotter

1989, Trotter et al. 1993). Still, the Endangered Species Committee of the American Fisheries

Society (AFS) identified all populations of anadromous coastal cutthroat trout as being at some

risk of extinction and coastal cutthroat trout from all Oregon streams as being at moderate risk of

extinction (Nehlsen et al. 19911 ). NMFS has listed coastal cutthroat trout in the Umpqua River

basin as an endangered species under the ESA (Johnson et al. 1994, Fed. Register Notice 50 CFR

Part 222).

The incongruity of being considered the “healthiest” cutthroat trout subspecies while

being identified by the AFS as having a moderate risk of extinction across its range reflects in

part a lack of information on the status of the fish. There has never been a coastwide effort to

collect the type of information about coastal cutthroat trout traditionally collected on commercially important species of Pacific salmon and routinely used by management agencies to

manage stocks. Consequently, data on the subspecies are generally collected incidentally, during

studies targeting other salmonids (e.g., smolt traps for coho salmon [Garrett 1998] or dam counts

[Loomis et al. 1993]) and to provide information most pertinent to the recreational angler (e.g.,

creel counts, presence/absence, feeding habitats).

The lack of information about coastal cutthroat trout in the Umpqua River was noted in

1946 by the Oregon State Fish Commission (FCO and OSGC 1946, p. 25) in a comment that is

still apt for much of the subspecies range:

Very little is yet known about these fish and they have been rightly called the “problem

children” of the State Game Commission . . .

Ironically, the Umpqua River Basin is one of the few areas across the range of O. c. clarki

where long-term counts of migrating coastal cutthroat trout have been made. For example,

Pacific salmonids have been counted since 1946 (the same year as the commission report) at

Winchester Dam on the North Umpqua River near Roseburg, Oregon (Table 2, Fig. 4). These

counts revealed two dramatic declines in coastal cutthroat trout passage, in the late 1950s and the

late 1970s (Fig. 5). In fact, more coastal cutthroat trout were counted passing Winchester Dam

in 1946 (1,138) than from 1977-93 combined (fewer than 1,049 in total) (Loomis et al. 1993).

2

 The authors of Nehlsen et al. (1991) were members of the AFS Endangered Species Committee and the

paper “states the opinions of the Committee and does not necessarily reflect AFS policy” (p.4).
13
14
15
16
17
18

However, it has been suggested (Cramer 1998, Loomis footnote 3) that fish in some of the earlier

counts may not have been coastal cutthroat trout, but were instead misidentified hatchery

rainbow trout or even coho salmon jacks (Bauer 1998). In the mid-1990s, few to no coastal

cutthroat trout were counted passing Winchester Dam, but more recent data suggests a

relative resurgence, with more than 80 fish per year counted in 1996 and 1997 (Loomis footnote

3). In 1998, 135 fish were counted by November 15 passing Winchester Dam for the highest

count since 1982. On most days only a single coastal cutthroat trout was counted passing the

dam, but 43 coastal cutthroat trout passed the dam over 2 days (30 on 28 July, 13 on 29 July).

These two days also coincided with the warmest water temperatures of the year (24.5°C) up to

that time.

Geographic Distribution

The distribution of coastal cutthroat trout is broader than that of any other cutthroat trout

subspecies. It extends along the Pacific coast of North America from the Eel River in northern

California (DeWitt 1954) to the Prince William Sound area of Alaska, extending to Gore Point

on the Kenai Peninsula (Scott and Crossman 1973, Behnke 1992). The eastern range of the

subspecies rarely extends farther inland than 160 km and usually is less than 100 km. The

eastern range appears to be bounded by the Cascade Mountain Range in California, Oregon, and

Washington, and by the Coast Range in British Columbia and southeastern Alaska (Fig. 2). This

range coincides closely with the coastal temperate rain forest belt defined by Waring and

Franklin (1979). The subspecies appears highly adapted to this region; even when the fish have

access beyond the coastal rainforest, as in the Columbia or Stikine rivers, they penetrate only a

limited distance inland (Sumner 1972; Trotter 1987, 1989).

The distribution of coastal cutthroat trout on the Pacific coast is reviewed in Hall et al.

(1997) by the following authors: for California by Gerstung (1997), for Oregon by Hooton

(1997), for Washington by Leider (1997), for British Columbia by Slaney et al. (1997), and for

Alaska by Schmidt (1997). As reported by Gerstung (1997), California coastal cutthroat trout

have been observed in 182 named streams (approximately 71% of the 252 named streams within

their range in California) and an additional 45 streams (17% of the named streams) likely support

populations. Reproducing populations occur throughout most of the Humboldt Bay tributaries,

the Smith and Little river basins, the lower portions of Redwood Creek and the Klamath, Mad,

and Eel rivers, and numerous small named and unnamed coastal tributaries (Gerstung 1997).

They also occur in five coastal lagoons and ponds—Big, Stone, and Espa lagoons, and the Lake

Earl-Talawa complex—with about 1875 ha of occupied habitat (Gerstung 1997). Gerstung

(1997) also reported that in California almost 46% of coastal cutthroat trout occupied habitats in

the Smith and Klamath river drainages. Historically, coastal cutthroat trout have been distributed

farther south along the northern California coastline down through the Russian River in Sonoma

County. There are still anecdotal reports of coastal cutthroat trout in several streams from the

Mattole River down to the Garcia River (Gerstung 1997); however, there are currently no known

self-sustaining populations south of the Mattole River or Cape Mendocino. Recently, snorkel
19

surveys of entire stream drainages throughout the state have been initiated to provide more

complete information on the subspecies distribution in California.

In Washington and Oregon, coastal cutthroat trout are widespread west of the crest of the

Cascade Mountains. Historically, the range of anadromous O. c. clarki may have extended past

the Cascade Crest into tributaries of the Columbia River, as far eastward as the Klickitat River at

River Kilometer (Rkm) 290 (Bryant 1949). At present, freshwater forms (migrants and

nonmigrants) of O. c. clarki are found at least to the Klickitat River on the Washington side of

the Columbia River (WDFW 1998a), and to 15-Mile Creek on the Oregon side (K. Kostow2 ).

Leider (1997) indicated that current distribution of sea-run fish appears to be confined to

tributaries downstream from Bonneville Dam (Rkm 235). At present the Washington

Department of Fish and Wildlife (WDFW) has identified 46 “stock complexes” in Washington

(WDFW 1998a).

In Oregon, two interior subspecies of O. clarki are also present: the Lahontan cutthroat

trout in southeastern Oregon, and the westslope cutthroat trout in the John Day River basin of

northeastern Oregon (Hooton 1997). Both of these interior subspecies live east of the Cascades

and neither has an anadromous component (Hooton 1997). In Washington, westslope cutthroat

trout reportedly occur naturally in the Lake Chelan drainage (Behnke 1988) and perhaps

throughout isolated headwater streams in the upper Columbia River basin (Behnke 1992). A

variety of interior subspecies have also been planted in numerous streams and lakes throughout

the Pacific Northwest.

The apparent lack of coastal cutthroat trout in Asia is puzzling. It seems unlikely that a

fish that thrives in nearshore coastal waters did not successfully invade Asia when the Beringia

land bridge was present during the ice ages. A potential solution to this mystery was uncovered

in 1994 when several specimens of a “new” trout were caught in the Tigil River of western

Kamchatka (in Eastern Russia, off the Bering Sea). These fish had the distinguishing physical

characteristics that separate a cutthroat from a rainbow trout (e.g., basibranchial teeth and nine

pelvic fin rays) (Savvaitova et al. 1995, Behnke 1996). However, analysis of the mitochondrial

DNA in 12 of these presumptive coastal cutthroat trout from the Tigil River, using a set of

markers developed at the NWFSC in Seattle, indicate that these fish are O. mykiss, not O. clarki

(J. Baker3 ).

4

 K. Kostow, ODFW, Fish Division, 2501 SW First Ave., PO Box 59, Portland, OR 97207. Pers.

commun. to O. Johnson. Oct. 1998.

5

 J. Baker, University of Washington School of Fisheries, Marine Molecular Biotechnology Laboratory,

3707 Brooklyn Ave. NE, Seattle, WA 98195. Pers. commun. to O. Johnson. May 1998.
20
21

INFORMATION RELATING TO THE SPECIES QUESTION

This section summarizes environmental and biological information relevant to

determining the nature and extent of coastal cutthroat trout ESUs in the Pacific Northwest. The

focus of this document is on populations in the contiguous United States; however, information

from Alaska and British Columbia was also considered to provide a broader context for

interpreting results. Furthermore, ESU boundaries are based on biological and environmental

information and do not necessarily conform to state or national boundaries.

Environmental Information

Environmental information was used to indicate possible ESU boundaries. We identified

areas where the physical environment appeared to change based on environmental characteristics

(i.e., river flow patterns, ocean conditions, water temperatures, climate, etc.), and on the

distributions of other organisms. Areas with different habitat types may have different selective

pressures that may lead to local adaptations within specific areas. The distributions of organisms

sympatric with coastal cutthroat trout were considered because the distributions may reflect

environmental, ecological, or historical processes that also affect these trout.

Geological and Climatic Events

The climatic events of the last 20,000 years have provided opportunities for isolation,

colonization, and population interbreeding. In determining ESU boundaries, it is useful to

understand the factors that may have shaped present-day coastal cutthroat trout population

distributions. Much of the present distribution of aquatic and terrestrial species in western North

America is a legacy of the volcanic, tectonic, and glacial forces that shaped this region. Events

such as headwater transfer or stream capture altered the flow of major rivers and the aquatic

species that inhabit them.

The Cordilleran ice sheet was the last major glacial event to affect the distribution of

coastal cutthroat trout and other salmonids in the Pacific Northwest. At its height (10-15,000

years ago), the ice sheet covered vast areas of Alaska, British Columbia, Washington, and Idaho

(McPhail and Lindsey 1970), creating a discontinuous distribution of salmonid populations.

Two major ice-free refugia existed: Beringia, composed of the Bering land bridge connecting

Eastern Siberia and Western Alaska, and Cascadia, composed of the lands south of the midColumbia River drainage (McPhail and Lindsey 1970). An additional ice-free refuge existed on

the coast of the Olympic Peninsula in the area of the Chehalis River. The drop in sea level

during the glacial periods may have created minor refugia along the coast of Vancouver Island or

the present-day Queen Charlotte Islands. As the ice sheet receded, salmonids from the Cascadia and

Beringia refugia began to colonize the newly exposed freshwater habitat (McPhail and Lindsey 1986).
22

Coastal cutthroat trout conduct extensive freshwater migrations, which may have allowed

them to quickly colonize the headwaters of new streams emerging from retreating glaciers

(c. 10,000 years ago). This colonization may have occurred in a number of ways. Coastal

cutthroat trout may have entered newly opened rivers on overwintering or feeding migrations.

Ice dams and land expansion after the retreat of glacial ice sheets caused rivers to alter course

and change watersheds. Spawning adults may have strayed into these new habitats by chance or

because their natal streams were inaccessible. As an example, during the last deglaciation, parts

of the Fraser River drainage flowed into the Columbia River via the Okanogan River and

Shuswap Creek (McPhail and Lindsey 1986). Further, several southeastern Alaskan and

northern British Columbia rivers (e.g., the Stikine, Skeena, and Nass) that now flow westerly into

the Gulf of Alaska drained, at various times, easterly into the Fraser River Basin (McPhail and

Lindsey 1986). These watershed exchanges may have allowed a mixture of species among the

Columbia River, Fraser River, coastal Washington and Puget Sound, and southeastern Alaskan

coastal rivers.

Ecoregions

The fidelity with which anadromous salmonids, including coastal cutthroat trout, return

to their natal stream implies a close association between a specific population and its freshwater

environment. The selective pressures of different freshwater environments may be responsible

for differences in life-history strategies among populations. As an example, Miller and Brannon

(1982) hypothesized that local temperature regimes are the major factors influencing variables

such as time of emergence, food availability, growth, and other life-history traits. Gresswell et al.

(1994) suggested that local adaptations in interior cutthroat trout may occur at a river basin or

stream tributary scale. Boundaries of distinct freshwater habitats coinciding with differences in

life histories would suggest a degree of local adaptation. Therefore, identifying distinct

freshwater, terrestrial, and climatic regions may help identify coastal cutthroat trout ESUs.

The ecoregions used in the document are a compilation of relevant information;

ecoregions for the contiguous United States retain designations assigned by the Environmental

Protection Agency (EPA) to its ecoregion system (Omernik 1987). The EPA system of

ecoregion designations is based on soil content, topography, climate, potential vegetation, and

land use. These ecoregions are similar to the physiographic provinces determined by the Pacific

Northwest River Basins Commission (PNRBC 1969) for the Pacific Northwest. Historically, the

distribution of coastal cutthroat trout in Washington, Oregon, and California included six of the

present-day EPA ecoregions (Fig. 6). Hughes et al. (1987) noted a strong relationship between

ecoregions and freshwater fish assemblages.

The ecoregions for the contiguous United States include physiographic information

presented by PNRBC (1969), present-day water use information (USGS 1993), river flow

information (Hydrosphere Products, Inc. 1993), and climate data from the U.S. Department of

Commerce (1968) into the appropriate ecoregion description (Omernik and Gallant 1986,
23
24

Omernik 1987). Additional information for British Columbia (Environment Canada 1977, 1991)

and Alaska (ADFG 1978, Alaska Geographic Society 1978) is included for comparative

purposes. The ecoregions we use are wholly or partially within the historical natural range of

coastal cutthroat trout in Washington, Oregon, and California.

Ecoregion descriptions follows. As noted earlier, names and associated numbers reflect

the EPA system (Omernik 1987).

Coast Range Ecoregion (#1)

Extending from the Olympic Peninsula through the Coast Range and south to the

Klamath Mountains and San Francisco Bay, the Coast Range ecoregion is influenced by medium

to high rainfall levels due to adiabatic cooling as marine weather systems intercept mountains of

the region. Topographically, the region averages 500 m in elevation, with mountains less than

1,200 m high. These mountains are generally rugged with steep canyons. Between the ocean

and mountains lies a narrow coastal plain composed of sand, silt, and gravel. Tributary streams

are short and have a steep gradient; therefore, surface runoff is rapid and water storage is

relatively short term during periods of no recharge. These rivers are especially prone to low

flows during times of drought. Regional rainfall averages 200-240 cm per year (up to 380 cm in

the Olympic Mountains) (Fig. 7), with generally lower levels along the southern Oregon coast

and northern California. Average annual river flows for most rivers in this region are among the

highest found on the West Coast when adjusted for watershed area (Fig. 8). River flows peak

during winter rain storms common in December and January (Fig. 9). Snow melt adds to the

surface runoff in the spring, providing a second peak in flows, and there are long periods when

the river flows maintain at least 50% of peak flow (Fig. 10). There is usually very little

precipitation in July or August, a dry period that may expand to 3 months every few years. River

flows are correspondingly at their lowest (Fig. 11) and temperatures at their highest during

August and September (Fig. 12).

This region is heavily forested, primarily with Sitka spruce (Picea sitchensis), western

hemlock (Tsuga heterophylla), Douglas fir (Pseudotsuga menziesii) and western red-cedar

(Thuja plicata). Forest undergrowth is composed of numerous types of shrubs and herbaceous

plants.

Primary land use in this region has been timber harvesting and agricultural development.

Splash dams were common features on many coastal streams throughout Washington and

Oregon at the turn of the century. Extensive stream cleaning and channelization occurred in

many coastal rivers to facilitate log drives (Sedell and Luchessa 1982), and the legacy of these

activities continues to influence conditions in many coastal streams today (Reeves et al. 1997).
25
26

Figure 8. Average annual flow per area (m3seconds(s)-1km-2) for selected river basins in Alaska, British

Columbia, Washington, Oregon, California, and Idaho. Values were calculated as the average

annual flow for each gauging station divided by the reported gauged area. Based on United

States Geological Survey (USGS) streamflow data (Hydrosphere Data Products, Inc. 1993) and

Inland Water Directorate streamflow data (Environment Canada 1991) (modified from

Weitkamp et al. 1995).
27
28
29
30
31

Puget Lowland Ecoregion (#2)

Situated between the Coast Range and Cascade Range ecoregions, this region

experiences reduced rainfalls (50-120 cm) from the rain-shadow effect of the Coast Mountains.

The area is generally flat, with high hills (600 m) at the southern margin of the ecoregion. Soils

are alluvial and lacustrine deposits. These deposits are glacial in origin north of Centralia,

Washington. This area tends to have large groundwater resources, with groundwater from the

bordering mountain ranges helping to sustain river flows during drought periods. Peak river flow

varies from December to June, depending on the decadal climate cycle and the contribution of

snowpack to surface runoff for each river system. Rivers tend to have sustained flows

(5 to 8 months of flows at 50% of the peak or more), and low flows are generally 10-20% or

more of the peak flows.

Douglas fir is the primary subclimax forest tree species, with other coniferous species

such as lodgepole (Pinus contorta), western white (P. monticola), and ponderosa pine

(P. ponderosa) locally abundant. Prairie, swamp, and oak, birch, and alder woodlands are also

common. The land is heavily forested, and wood-cutting activities (such as building roads and

splash dams) contribute to soil erosion, river siltation, and river flow and temperature alteration.

Because the Puget lowland surrounds one of North America’s largest protected bays with

access to marine shipping, it has been become heavily urbanized, especially along the western

slopes of the Cascade Mountains and the shore of Puget Sound (major cities surrounding Puget

Sound include Everett, Seattle, Tacoma, Olympia, and Bremerton). Domestic and industrial

wastes, urban runoff, and sewage treatment degrade the quality of local water systems.

Exceptions are river systems draining into the Hood Canal region and northern Puget Sound.

However, even here, extensive diking, agricultural use, logging operations, housing

developments, and other changes have altered the physical geography and flows of river systems

(Brody 1991, Ashbaugh 1994). Glacial sediment also influences water quality, especially in the

Skagit, North Fork Nooksack, Nisqually, and Puyallup/White river basins.

Willamette Valley Ecoregion (#3)

The Willamette Valley, which adjoins the southern border of the Puget Lowland

ecoregion at the Lewis River, was not glacially influenced. A rainshadow effect, similar to the

one influencing the Puget Lowland ecoregion, limits rainfall to about 120 cm per year. River

flows peak in December and January and are sustained for 6-7 months of the year. Low flows

occur in August and September, although the volume is generally 20% of the peak flow.

Much of the land has been converted to agricultural use, with Douglas fir and Garry oak

(also known as Oregon white oak [Randall et al. 1990]) (Quercus garryana) stands in lessdeveloped areas. Irrigation is common, and stream flows, especially in the southern portion of

this ecoregion, can be significantly reduced as a result. Agricultural and livestock practices

contribute to soil erosion and fertilizer/manure deposition into stream systems.
32

As in the Puget Lowland ecoregion, water quality in the Willamette Valley is degraded

by agricultural, timber, and urban activities, especially near at the mouth of the Willamette River

and along parts of the Lower Columbia River (e.g., Portland, Oregon, and Longview,

Washington). Many water quality problems are exacerbated by low water flows and high

temperatures during the summer. Pulp and paper mill discharges of dioxin into the Columbia

and Willamette rivers are considered another water quality concern, although this situation has

improved (USGS 1993).

Cascades Ecoregion (#4)

The Cascades ecoregion is composed of the Cascade Range in Washington and Oregon

and contains the headwater tributaries of many coastal cutthroat bearing rivers, including the

Skagit, Stillaguamish, Willamette, Umpqua, and Rogue. Mountain peaks above 3,000 m are

distributed throughout the region. The crest of the Cascade Range (averaging 1,500 m) captures

much of the ocean moisture moving eastward and poses a biological barrier to many terrestrial

and aquatic animals. Precipitation can average 280 cm per year, much of it in the form of heavy

snowfall. Intense rainstorms (those depositing more than 2.5 cm per hour) are rare. Rainfall is

generally spread over the year, with most of it between October and March. There is little

capacity for long-term groundwater storage except where porous rock substrate exists. In these

porous areas, streams receive 75-95% of their average discharge as groundwater and are able to

maintain flows during dry periods. Surface water flow originating in the Cascade Range

influences river flows throughout this region.

The area is primarily forested with Douglas, noble (Abies procera), and Pacific silver fir

(A. amabilis) (all subclimax species), whereas western hemlock and western red-cedar are

common climax species. At higher elevations, these trees are replaced by Engelmann spruce

(Picea engelmannii), whitebark pine (P. albicaulis), grand fir (A. grandis), and mountain

hemlock (Tsuga mertensiana). Forest undergrowth tends to be dense on the western slopes of

this region and sparse on the eastern slopes. A combination of heavy rainfall and wood-cutting

activities has increased soil erosion.

Sierra Nevada Ecoregion (#5)

South of the Cascades Ecoregion is a similar ecoregion comprised of portions of the

Klamath, Sierra, Trinity, and Siskiyou mountains. The Sierra Nevada ecoregion includes the

present-day southern extent of coastal cutthroat trout (at the Eel River in California). Annual

rainfall varies considerably, from 40 cm to more than 150 cm, depending on elevation and the

degree of rainshadowing. Most of the rain falls in winter, with summers being hot and dry.

Topographically, the region rises to over 2,000 m, with an average elevation of 1,000 m.

This ecoregion contains the headwaters for the Rogue, Klamath, and Sacramento rivers.

Historically, peak flows occurred in February, with lowest flows in August, September, or

October; however, water diversion and impoundment activities changed this pattern and flows
33

are now more evenly distributed throughout the year. This change occurred primarily through

irrigation/flood-mitigation-related reductions in peak flows and less so through increased spillage

during the historical time of minimum flows.

Douglas fir is the predominant tree species, but mixed coniferous/oak stands are

common. Soils tend to be unstable, and timber harvest or livestock grazing can result in severe

erosion. Hydraulic placer mining has had a considerable impact on stream quality and hillslope

stability.

Eastern Cascades Slopes and Foothills Ecoregion (#9)

Anadromous coastal cutthroat trout are believed to have historically inhabited this

ecoregion at least as far east as the Klickitat River (Bryant 1949), but only freshwater forms are

now believed to be present (Leider 1997). This ecoregion marks the transition between the high

rainfall areas of the Cascades Ecoregion and the drier basin ecoregions to the east. The area

receives 30-60 cm of rainfall per year. Streamflow is intermittent, especially during the summer

dry season. Surface and groundwater contributes to flows in the Yakima, Deschutes, Klickitat,

and White Salmon rivers.

Ponderosa and lodgepole pine are common throughout the region, with little forest

undergrowth. Soils tend to be volcanic, young, and highly prone to erosion. Primary land uses

are timber harvest and mixed grazing/timber areas. Agriculture is limited to valleys and

irrigation is commonly employed.

Coastal British Columbia

The maritime climate of the Olympic Peninsula continues north along the west coast of

Vancouver Island and along the British Columbia mainland north of Vancouver Island. The

Fraser River, which drains into the Strait of Georgia at Vancouver, dominates about one-fourth

of the province of British Columbia and is the largest single river producer of Pacific salmon in

the world (Northcote and Atagi 1996).

Limited hydrographic data (Farley 1979) indicate that river flow patterns in coastal

British Columbia are similar to those on the Olympic Peninsula, with relatively high flows

throughout the year. There is a general decrease in summer air temperatures to the north—the

Olympic Peninsula coast is generally a few degrees warmer than the southwest coast of

Vancouver Island, which is a few degrees warmer than the northwest coast and the mainland

north of Vancouver Island. Annual rainfall and snowfall average 111 cm and 55 cm respectively

in Vancouver and 240 cm and 140 cm respectively in Prince Rupert (Environment Canada 1996).

Anadromous cutthroat trout are found in at least 756 streams throughout the region, but

information was available for only 120 populations in a recent assessment of population status

(Slaney et al. 1997). More than half of the 120 populations were determined to be at some level

of risk, and several populations within the lower Fraser River and Georgia Strait were considered
34

extinct. Habitat degradation attributed to urban development was reported as posing the greatest

threat to coastal cutthroat trout populations (Slaney et al. 1997).

Southeastern and southcentral Alaska

A maritime climate dominates the southeastern coast of the Alaska panhandle and

continues north along the coast to the southcentral region of Prince William Sound. This area

marks the northern extent of the distribution of coastal cutthroat trout. Average annual rainfall

and snowfall for Annette Island in southeastern Alaska are 260 cm and 130 cm, respectively,

while Cordova in southcentral Alaska receives an average of 240 cm of rainfall and 300 cm of

snowfall per year (CDC 1961-98).

The crest of the Coast Range in southeastern Alaska forms the Alaska-Yukon-British

Columbia boundary (ADFG 1978). This coastal area is characterized by numerous islands, bays,

and short steep stream channels. The southcentral region includes the drainages that enter the

Gulf of Alaska and is dominated by the Copper River basin. The estuary of the Copper River,

numerous islands, and hundreds of small coastal streams create thousands of miles of habitat in

Prince William Sound for rearing salmonids, including coastal cutthroat trout (ADFG 1978).

Western hemlock and Sitka spruce dominate the forests, with some western red-cedar,

Alaska-cedar (Chamaecyparis nootkatensis), and red alder (Alnus rubra) scattered throughout

the region. Natural resources have long dominated the economy including forest products,

mining, fishing, tourism and recreation (Alaska Geographic Society 1978).

Biogeography

Vegetation

Forest communities have specific requirements, which means that dominant vegetation

types are a valuable indicator of relative precipitation, temperature, soil type, solar radiation, and

altitude. Changes in vegetation types indicate changes in the physical environment, which may

affect freshwater coastal cutthroat trout habitat. The following discussion of vegetation was

compiled from Viereck and Little (1972), Franklin and Dyrness (1973), Barbour and Major

(1977), Farley (1979), and Whitney (1985).

Sitka spruce zone

Coastal regions in Oregon, Washington, and British Columbia are forested with a Sitka

spruce-dominated floral community, which includes western hemlock, western red-cedar, red

alder, and Douglas fir as major species. This vegetation type is restricted to coastal regions and

river valleys; only over coastal plains does it extend more than a few kilometers inland, even
35

then exceeding elevations of 150 m only in areas immediately adjacent to the ocean. This

vegetation type is typified by a uniformly wet and mild climate. Sitka spruce forests could be

considered a variant of western hemlock forests of higher elevations and inland areas, but are

distinguished by frequent summer fogs, higher moss concentrations, lichen abundance, and

proximity to the ocean (Franklin and Dyrness 1973).

Along the coast, Sitka spruce forests grade into redwood forests in southern Oregon and

northern California, and into western hemlock-dominated forests along the Strait of Juan de Fuca

to the north. Sitka spruce forests also extend up the Columbia River to approximately the

Clatskanie River (RKm 80), beyond which point the vegetation increasingly reflects the drier

climate east of the Coast Range.

Redwood zone

Beginning in the Chetco River basin in southern Oregon (Fig. 3), Sitka spruce and

western hemlock are replaced by redwood forests slightly inland and in river bottoms along the

coast. This forest type forms the dominant coastal vegetation south to Monterey at elevations

between 30 and 800 m. From the redwood zone along the coast, vegetation on the moist western

slopes changes to Douglas fir/hardwood forests at lower elevations, followed by Shasta red

(A. magnifica shastensis) and white fir (A. concolor), and finally mountain hemlock at higher

elevations. Vegetation in the upper basins of the Rogue and northern California rivers is adapted

to a more arid climate than those closer to the coast, and consequently is distinct from upperbasin vegetation types either north or south. These vegetation types include areas with Garry

oak, mixed evergreen, and Klamath montane, coastal montane, and oak/pine forests and

chaparral. South of the Mattole River, upper basins are not as arid and the vegetation is more

like the coastal type: primarily redwoods with patches of mixed evergreens and mixed

hardwoods, and coastal prairie-scrub around the San Francisco Bay area.

Western hemlock zone

Along the Washington and Oregon coasts, the western hemlock-dominated plant

community replaces Sitka spruce at elevations above 150 m. In the Puget Sound/Strait of

Georgia area, the western hemlock community forms the dominant vegetation from sea level to

700-1,000 m. This vegetation type includes western hemlock, Douglas fir, red alder, and western

red-cedar as major species. The transition point between Sitka spruce and western hemlock

along the Strait of Juan de Fuca appears to be approximately the Elwha River on the U.S. side

and Sooke Inlet on the Canadian side. South of the Columbia River, the western hemlock zone

extends southward along the Coast Range to the Klamath Mountains and southward along the

Cascade Mountains to the Umpqua River (Fig. 3). Forests in the Puget Sound area are often

considered a special type of western hemlock community: the area’s lower precipitation and

glacial soils make drought-stress-tolerant western white, lodgepole, and occasionally ponderosa

pine major species, whereas they are considered minor species elsewhere in the western hemlock

zone.
36

Alpine and subalpine zones

The headwaters of rivers draining higher mountains, such as the Olympic and Cascade

mountains and the British Columbia and Oregon Coast ranges, begin in alpine meadows and

subalpine parklands before the change to western hemlock-dominated forests below 700 to

1,000 m. The higher alpine regions are typified by a mosaic of meadows and tree patches with

extensive and deep snow cover. The subalpine zone is dominated by mountain hemlock and

subalpine fir, has less extensive snow cover than higher alpine areas, and is wetter and colder

than areas at lower elevations.

Analyses of vegetation types

In his factor analysis of western U.S. floras based on the distribution of more than 9,000

plant species, McLaughlin (1989) defined three floristic areas within the range of coastal

cutthroat trout: the Vancouverian, Sierra Nevada, and California areas. The Vancouverian area

includes the Sitka spruce zone described above, the western hemlock zone (excluding the central

and southern Oregon Cascade Mountains), and the redwood zone from its northern boundary to

approximately Cape Mendocino. The California floristic area includes the redwood zone south

of Cape Mendocino and lower elevation portions of the Sacramento/San Joaquin Valley, while

the Sierra Nevada area covers the central and south Oregon Cascade Mountains, the interior

Klamath Mountain Province, and the Sierra Nevada Mountains. In a similar analysis based

solely on Pacific coast beach vegetation, Breckon and Barbour (1974) identified a “temperate”

eco-floristic zone from lat. 54° N to lat. 36°30' N. This zone is subdivided into a northern North

Coastal Zone and a southern Mediterranean Zone with the boundary at lat. 43°30' N (approximately the Coos River, about 70 km north of Cape Blanco).

Zoogeography

Like vegetation types, the distribution patterns of marine and freshwater species indicate

variations in the physical environment these species share with coastal cutthroat trout. These

variations in the physical environment may affect coastal cutthroat trout habitat and put different

selective pressures on coastal cutthroat trout in different zoogeographical areas.

Marine fishes

There are two distinct faunal boundaries for marine fishes within the range considered in

this status review: Point Conception in California (lat. 34°30' N) and the northern tip of

Vancouver Island (approximately lat. 50° N) (Allen and Smith 1988). Marine fishes north of

Vancouver Island are primarily coldwater subarctic species, those between lat. 50° N and lat.

34°30' N primarily temperate species, and those south of Point Conception primarily subtropical.

Although not a distinct faunal boundary, Cape Mendocino represents a southern limit beyond

which many northern species do not routinely occur (Horn and Allen 1978).
37

Marine invertebrates

The distribution of marine invertebrates shows transition points between major faunal

communities similar to those for marine fishes (Hall 1964, Valentine 1966, Hayden and Dolan

1976, Brusca and Wallerstein 1979). Invertebrate faunal boundaries along the west coast of

North America occur at approximately Dixon Entrance (directly west of Prince Rupert), the

Strait of Juan de Fuca, and Point Conception, with a minor boundaries at Cape Mendocino and

Monterey Bay (Hall 1964, Valentine 1966). The primary cause of this zonation is attributed to

temperature (Hayden and Dolan 1976), but other abiotic (Valentine 1966) and biotic (Brusca and

Wallerstein 1979) factors may also influence invertebrate distribution patterns.

Freshwater fishes

Freshwater fishes in southern and central British Columbia, Washington, and most of

coastal Oregon are populations of Columbia River origin (McPhail and Lindsey 1986, Minckley

et al. 1986). Variation in the makeup of freshwater fish communities in these areas reflects the

varied dispersal patterns of fishes between river basins. The Stikine River in northern British

Columbia is the point at which freshwater fishes from the north displace the Columbia River fish

fauna (McPhail and Lindsay 1986). The Sixes River in southern Oregon marks the southern

extent of the Columbia River freshwater fish fauna (Snyder 1907, Minckley et al. 1986).

Freshwater fishes in the Klamath-Rogue Ichthyofaunal Region, which includes the Klamath and

Rogue rivers, differ from the Columbia River-dominated assemblages to the north and the

Sacramento/San Joaquin River-dominated faunas to the south (Snyder 1907, Moyle 1976,

Minckley et al. 1986). Freshwater fishes in northern and central California between Redwood

Creek and Carmel River are derived from the Sacramento-San Joaquin River system. However,

many of the smaller basins have no exclusively freshwater fishes, but only species that move

readily through salt water (Moyle 1976).

Estuarine fishes

Estuarine fishes also show regional differences based on presence or absence of species

and can be roughly divided into five groups within Washington, Oregon, and northern and

central California (Monaco et al. 1992). Two large groups with considerable overlap extend

from Willapa Bay in Washington to the Eel River in California. The differences between these

two groups appear related to the size of the estuaries. In Washington, two groups have been

identified: one overlaps to some extent with the two large groups and encompasses Grays

Harbor, Willapa Bay, and the Columbia River estuary; a second group is restricted to Puget

Sound and Hood Canal. Differences between these two groups also appear to be related to the

size of the estuaries. A final group extends from Tomales Bay to Morro Bay in California.
38

Amphibians

Many amphibian species have very restricted distributions and may serve as indicators of

subtle differences in environmental conditions and historical distributions. The distributions of

many amphibians appear to begin and end at several common geographical areas within the

range of coastal cutthroat trout in Washington, Oregon, and California. For example, the Strait

of Georgia and Vancouver Island is the northern extent of the distributions of many amphibians,

including tailed (Ascaphus truei) and red-legged (Rana aurora) frogs and Pacific giant

(Dicamptodon tenebrosus), western long-toed (Ambystoma macrodactylum macrodactylum),

western red-backed (Plethodon vehiculum), Oregon (Ensatina eschscholtzii oregonensis), and

brown (A. gracile gracile) salamanders (Cook 1984). The Cape Blanco area of southern Oregon

is the northern extent of southern long-toed (A. m. sigillatum), Del Norte’s (P. elongatus), and

California slender (Batrachoseps attenuatus) salamanders, and the southern extent of western

red-backed salamanders (Stebbins 1985, Leonard et al. 1993). Cape Mendocino is the northern

extent of the southern red-legged frog (R. a. draytonii), red-bellied newt (Taricha rivularis), and

arboreal salamander (Aneides lugubris), and the southern extent of the northern red-legged frog

(R. a. aurora) and Del Norte’s salamander (Stebbins 1985). Additionally, the Olympic torrent

salamander (Rhyacotriton olympicus) occurs only on the Olympic Peninsula, while the Pacific

giant and Dunn’s (P. dunni) salamanders occur in most areas in western Washington and Oregon

except the Peninsula (Leonard et al. 1993).

Life History

Several types of life-history information were considered in evaluating the diversity of

coastal cutthroat trout. Life-history traits examined included smolt size and outmigration timing,

age, river entry timing, size, and frequency of spawning. However, the use of such traits to help

define coastal cutthroat trout ESUs is complicated by several factors.

First, long-term data sets are rare, and data collected from different locations during

different years may obscure regional patterns in life-history traits. Moreover, differences in

collection methods can hinder meaningful comparisons. For example, traits such as age and size

at migration will likely be very different for fish caught by angling and for those caught in rotary

traps or tributary weir traps. Nearly all gear types are selective for size and species (Hayes et al.

1996). For coastal cutthroat trout, tributary weir traps can be more selective than rotary traps for

both size and age of captured fish (Garrett 1998).

Second, the difficulties with aging cutthroat trout by scale analysis may hinder

meaningful comparisons among studies. Coastal cutthroat trout scales are notoriously difficult to

read and interpretations of scale patterns often vary greatly between readers (Knudsen 1980).

Cutthroat trout tend to easily lose their scales and the rate of regeneration has been shown to

increase as the fish gets older. Cooper (1970) examined the proportion of regenerated scales to

nonregenerated scales from cutthroat trout of several size classes. In his study, Cooper found
39

that about 40% of the scales collected from yearling fish (40-49 mm FL) were regenerated,

whereas more than 80% of the scales collected from fish larger than 140 mm showed

regeneration. Furthermore, evidence suggests that large spacing between annuli is not a clear

indicator that the fish has spent time in salt water. Highly productive freshwater habitats may

confer scale patterns in cutthroat trout that are indistinguishable from saltwater growth

(Tomasson 1978, D. Saiget6). In a study in Petersburg Lake, Alaska, Jones (1977) found very

little difference in age and length data between freshwater and sea-run cutthroat trout. This

problem was also discussed by Sumner (1962), who expected that tidewater growth should be

intermediate between stream and saltwater patterns. Rather, Sumner (1962) and Giger (1972)

found that tidewater growth was similar to stream growth patterns. Otolith analysis may provide

a more reliable means of establishing life history patterns and ages, but the technique has not

been widely applied in cutthroat research as it is costly, time consuming, and requires killing the

fish.

Third, fish exhibiting different life histories are often morphologically indistinguishable,

particularly as juveniles (Tomasson 1978, Fuss 1982). Direct comparisons of coastal cutthroat

trout life-history traits between stocks have not been made under controlled conditions.

Differentiating life-history forms is further complicated by a lack of definitive terms in the

literature to distinguish between these forms (see “Terminology,” p. 6).

Fourth, the sensitivity of life-history traits to environmental and genetic influences may

allow their alteration by anthropogenic activities such as land-use practices (Hartman et al. 1984,

Holtby 1987), harvesting (Ricker 1981), or artificial propagation (Steward and Bjornn 1990,

Hard et al. 1992, Campton 1995, Flagg et al. 1995). The effects of anthropogenic activities on

coastal cutthroat trout life-history traits are unclear and consequently difficult to factor out. To

help limit any bias introduced by artificial propagation, life-history trait comparisons in this

status review have focused on naturally spawning populations. Life-history trait information

from hatchery populations was used only when information from naturally spawning populations

was insufficient.

Finally, relatively less is known of the migratory pathways of coastal cutthroat trout than

of pathways for the other species of Pacific salmon. Research into Pacific salmonid migrations

has been dominated for decades by studies on the long-distance transoceanic aspects of the life

cycle. Much of the research into long-distance migrations has focused on the migrational timing

and pathways important to the commercial fishing industry. Coastal cutthroat trout do not make

transoceanic migrations, nor are they a commercial species. For these reasons, minimal attention

has been given to the short-distance estuarine or freshwater migrations of these fish.

6 

D. Saiget, U.S. Dep. of Agriculture, Forest Service, Zig Zag Ranger District, 70220 E. Hwy 26, Zig Zag,

OR 97049. Pers. commun. to A. Garrett, Aug. 1998.
40

Patterns of Life-History Variation

The life history of coastal cutthroat trout is perhaps the most complex of the Pacific

salmonids (Northcote 1997a), with reproductive and migratory behaviors at least as diverse as

those of steelhead and sockeye salmon and perhaps more similar to some species in the genera

Salmo (e.g., Atlantic salmon [S. salar] and brown trout [S. trutta]), Salvelinus (e.g., bull trout

[S. confluentus], Dolly Varden [S. malma], and Arctic char [S. alpinus]), and Hucho (Stearley

and Smith 1993). Unlike many Pacific salmonids where all (e.g., chum or pink salmon) or

almost all (e.g., coho and chinook salmon and steelhead) members are anadromous, coastal

cutthroat trout populations may contain both migratory and nonmigratory individuals within the

same population (reviewed in Hall et al. 1997). Although all coastal cutthroat trout populations

with access to the sea are believed to have an anadromous component, not all members of the

subspecies migrate to the sea (Giger 1972, Sumner 1972, Trotter 1989). Most cutthroat trout that

do enter seawater do so as 2- or 3-year-olds, but some remain in fresh water for up to 5 years

before entering the sea (Giger 1972, Sumner 1972). Other coastal cutthroat trout never

outmigrate at all, but remain in small headwater tributaries. Still others migrate only into rivers

or lakes (Nicholas 1978a, b; Tomasson 1978; Moring et al. 1986; Trotter 1989) even when they

have seawater access (Tomasson 1978). For example, anadromous, freshwater migratory, and

nonmigratory life-history forms of coastal cutthroat trout have all been reported in southern

Oregon’s Umpqua River Basin (Trotter 1989, Loomis and Anglin 1992, Loomis et al. 1993,

Hooton 1997).

Multiple life-history forms frequently coexist within the same watershed and even the

same stream (June 1981, Johnston 1982). Where multiple forms exist together, spatial and

temporal differences in reproductive behaviors may be large enough to promote genetic

differentiation (June 1981, Zimmerman 1995). On the other hand, similar environmental

conditions (such as water temperature and velocity) may facilitate reproductive overlap of lifehistory forms. Allelic and meristic variation among coastal cutthroat trout populations in the

Nisqually River’s Muck Creek basin led Zimmerman (1995) to suggest that the expression of

anadromy probably differs among populations within a basin even when no geologic barrier

exists. Thus, some populations may be entirely anadromous some may be entirely freshwater

forms, and some may have multiple life-history forms.

Direct comparisons of coastal cutthroat trout life-history traits among populations or

individuals have not been made under controlled conditions; even so, it is unclear to what extent

such comparisons would be applicable to natural populations. Information from other species

suggests that anadromous forms may occasionally have nonanadromous progeny, and vice versa

(Nordeng 1983, Kaeriyama et al. 1992, Burgner et al. 1992, Mullan et al. 1992). Both of these

relationships may occur in coastal cutthroat trout, according to otolith microchemistry analysis of

fish in Oregon’s Elk River (Griswold 1996). Griswold (1996) found that some sea-run cutthroat

trout had signals in the otolith primodia that indicated their maternal parent was in fresh water at

the time of yolk formation and that they migrated to the marine environment. Other fish had

strontium/calcium signals that indicated their maternal parent was in the marine environment at

the time of yolk formation and that they also migrated to the marine environment.
41

Only in a few instances, however, have larger migratory (possibly sea-run) female coastal

trout been observed paired with small “cryptically colored” males during spawning periods

(Northcote 1997a, Saiget et al. in prep). Females observed by Saiget et al. (in prep.) ranged from

300 to 359 mm and males ranged from 100 to 180 mm. It is unclear what the observations of

these five fish might imply for the reproductive behaviors of coastal cutthroat trout. Two

possibilities are that some males in anadromous populations may mature at a young age and

small size (precocious maturation) and perhaps never migrate to sea, or that fish of one lifehistory form will readily interbreed with other life-history forms. However, information about

other species suggests that behavioral differences in mate selection would probably promote

some degree of assortative mating between sympatrically spawning anadromous and freshwater

forms (Neave 1944, Foote and Larkin 1988).

The migratory patterns of coastal cutthroat trout suggest that patterns may vary within as

well as among populations. Some populations of coastal cutthroat trout are split into migratory

and nonmigratory individuals, a phenomenon termed “partial migration” by Jonsson and Jonsson

(1993). For example, Heggenes et al. (1991) studied local movements and spatial stability of

413 coastal cutthroat trout in the Musqueam-Cutthroat Creek system, British Columbia. A total

of 587 recaptures were made of marked coastal cutthroat trout between winter and late summer.

Heggenes et al. (1991) found that nearly two-thirds of the marked fish had not moved more than

10 m; only 17.9% moved more than 50 m. The authors acknowledged that within this “resident”

group some proportion was likely to be anadromous, though the correlation (based on 246

observations) between distance moved and fish size was weak (r2

 = 0.0333, P = 0.0039). These

authors also found that large fish were still in the stream after anadromous spawners typically

would have emigrated, which led them to speculate that a substantial proportion of the mobile

individuals were not anadromous (Heggenes et al. 1991). In other studies describing movements

of presumably freshwater migratory coastal cutthroat trout, Waters (1993) (Table 3) and Moring

et al. (1986) observed that fewer than 10% of the fish moved extensively; Moring et al. (1986)

found that 93% of the recaptured coastal cutthroat trout were recovered in the same pool or riffle.

These studies illustrate that while the vast majority of fish within a population probably

behave similarly, some individuals may exhibit migratory behaviors that differ from their

cohorts. The notion that all fish in a population fit neatly into one category or the other may not

be true (Gowan et al. 1994). In a study on brown trout, Harcup et al. (1984) found no evidence

to suggest that the migratory component of the population was composed of permanently mobile

individuals. Rather, they found that individual brown trout switched between migrating and not

migrating, and migratory fish were no more likely to move in subsequent sampling periods than

nonmigratory fish.

Environmental conditions, particularly those affecting growth rate, have been shown to

markedly alter the degree of residency expressed in some salmonid species (Jonsson 1985,

Hindar et al. 1991, Northcote 1992). In an intensive study on Arctic char, Nordeng (1983) reared

the progeny of experimentally produced crosses of freshwater and anadromous individuals under

different feeding regimes and found that increasing the amount of food significantly increased

the proportion of freshwater individuals to anadromous fish. Not only could each form produce
42
43

progeny of any form, but single individuals could also change forms during their lifetimes. The

age at sexual maturity of the parents, however, influenced the age at sexual maturity of their

offspring. Thus, the offspring of small freshwater fish produced more early maturing

(nonmigratory) offspring and fewer smolts than did the offspring of anadromous parents

(Nordeng 1983).

Some salmonids, as illustrated in the above example, have a behavioral flexibility that

allows them to respond to environmental conditions. There is some empirical evidence to

suggest that coastal cutthroat trout migratory behaviors may be flexible, but the extent to which

such a strategy occurs is unknown. In an ongoing study that began in the spring of 1997, the

Alaska Department of Fish and Game (ADFG) started PIT (passive integrated transponder)

tagging coastal cutthroat trout as they outmigrated to sea from Auke Lake (D. Jones7 ). During

the fall of 1997, an upstream migrant trap was operated and all immigrating coastal cutthroat

trout were counted. Previously tagged fish were individually identified and recorded by their

PIT tag number and immigration date. Again, in the spring of 1998 coastal cutthroat trout were

recorded leaving the lake and all unmarked fish were tagged. During the summer of 1998,

ADFG surveyed the lake for freshwater forms of coastal cutthroat trout and found three fish that

had been PIT tagged on their emigration to sea in 1997, returned to the lake in the fall of 1997,

and apparently opted to remain in the lake in 1998.

Other empirical evidence supports the idea that life-history patterns can vary within

individual coastal cutthroat trout over time. For example, some sea-run cutthroat trout may

spawn before their first saltwater migration (Giger 1972, Tomasson 1978, Fuss 1982, Jones

footnote 7), and others may not return to sea after spawning but may instead remain in fresh

water for a year (Tomasson 1978).

Research on other species suggest that even very small individual differences in behavior

and physiology, particularly during the first few weeks of life, can affect life-history patterns

(Metcalfe 1993). Thorpe (1989) proposed that there is a critical period in which some

characteristic of performance, such as a threshold level of growth, will define the direction of

individual development. The role that growth plays in determining life-history patterns is

complex, as residualization may occur in fish that grow either too quickly or too slowly. An

abundant food supply may promote residency (Northcote 1992) and may induce early or

precocious maturation. Furthermore, at any point along the migratory path or even at the

microhabitat level, individuals of a cohort may respond differently to environmental factors (e.g.,

temperature, food availability, and predation). The ability of an individual to modify its behavior

in response to food abundance, threat of competition, risk of predation, and experience suggests

many fish species possess some degree of adaptive flexibility (Dill 1983).

This diversity in life history may reflect an adaptive generalist strategy that allows coastal

cutthroat trout to exploit habitats not fully utilized by other salmonids (Johnston 1982, Northcote

1997a). For example, their small size at maturity may give coastal cutthroat trout an adaptive

7

 D. Jones, ADFG, Div. of Sport Fish, Douglas, AK 99824. Pers. commun. to A. Garrett. Oct.

1998.
44

advantage for using small streams for spawning and rearing and reduce interspecific competition

with other anadromous spawning salmonids (Pearcy et al. 1990). Conversely, post-spawning

coastal cutthroat trout or those on feeding migrations are larger than outmigrating juveniles of

other Pacific salmon species, which allows coastal cutthroat trout to prey on these fish in a

variety of freshwater and estuarine habitats (Pearcy et al. 1990, Northcote 1997a). For these

reasons, Northcote (1997a) suggested that, historically, coastal cutthroat trout were probably

present year round in a wider variety of climatological conditions and diversity of marine and

freshwater habitats than any other salmonid in the coastal Pacific Northwest (Northcote 1997a).

Life-history forms

The diversity of migratory behaviors in coastal cutthroat trout makes identification of fish

by life-history form particularly challenging. One way to separate coastal cutthroat trout into

population groupings is to classify them by the physical locations where they are caught (e.g.,

Wyatt 1959, Tomasson 1978, June 1981, Moring et al. 1986). These classifications, however,

are somewhat arbitrary as fish may move from one area to another (Northcote 1997a).

Consequently, the location and timing of sampling may affect which life-history category

migratory individuals are chosen to represent (Fausch and Young 1995). For instance, coastal

cutthroat trout believed to be freshwater forms one year may migrate to sea another year (e.g.,

some fish do not make their initial migration to sea until age 6 (Sumner 1962, Giger 1972) and

some sea-run cutthroat trout may not enter saltwater every year after their initial smolt migration,

but may instead stay in fresh water (Tomasson 1978, Jones footnote 7). For these reasons, we

define the three general life-history forms of coastal cutthroat trout as follows (see also Fig. 1).

Nonmigratory coastal cutthroat trout—This life-history form includes fish generally found in

small streams and headwater tributaries near spawning and rearing areas. These fish typically

undertake only small-scale migrations and maintain relatively small home territories compared to

forms that make more extensive migrations. In general, nonmigratory coastal cutthroat trout

appear to grow more slowly than other life-history forms of trout (Tomasson 1978, Trotter 1989),

are smaller at maturity (seldom larger than 150-200 mm in length), and rarely live longer than 2

to 3 years (Wyatt 1959, Nicholas 1978a, June 1981). However, as June (1981) points out, the

lack of older fish in his study may be due not only to age-dependent mortality, but also to scaleaging problems or outmigration of older larger fish from the study area.

The proportion of coastal cutthroat trout within a basin that exhibit this nonmigratory life

history is often difficult to determine. As an example, in a study by Wyatt (1959) of presumably

nonmigratory coastal cutthroat trout in Lookout Creek, a small tributary of Oregon’s Willamette

River, only 14% of 1,112 fish originally marked were recovered. Of these 155 recoveries, 150

(97%) had not moved more than 180 m from the original point of marking. No fish marked in

the three upper seining stations were recovered in the lowermost stations, which led Wyatt to

suggest that probably no major downstream movement occurred during the study period of June

1955 to September 1957. The distribution of the remaining marked fish was not determined.
45

Freshwater-migratory coastal cutthroat trout—This freshwater or potamodromous (e.g.,

Myers 1949, Tomasson 1978) life-history form includes fish that migrate entirely within fresh

water. A variety of distinctive population migrations are frequently recognized within this

general classification, including populations that migrate from large tributaries to small

tributaries to spawn (fluvial-adfluvial), populations that inhabit lakes and migrate upstream to

spawn in the lake inlet (lacustrine-adfluvial), and populations that live in lakes and migrate

downstream to spawn in the lake outlet (allucustrine) (Varley and Gresswell 1988, Trotter 1991).

These freshwater-migratory populations are best documented in rivers and lakes with

physical barriers to anadromous fish, such as above Willamette Falls in the Willamette River.

Historically, these falls apparently barred access of anadromous fish to the upper river; above

this barrier, schools of coastal cutthroat trout were found to migrate from natal spawning areas to

mainstem feeding areas and back (Dimick and Merryfield 1945; Nicholas 1978a,b; Moring et al.

1986). River-migrating coastal cutthroat trout have also been reported as schooling in large

streams above migration barriers in southwest Oregon (e.g., upper Chetco River and upper Silver

Creek [Illinois Basin]) (ODFW 1993b).

Only rarely have nonanadromous river-migrating schools of coastal cutthroat trout been

reported below barriers or in locations with access to anadromous fish. The Rogue and Umpqua

rivers are two locations where this behavior has been documented. Tomasson (1978) was first to

identify migratory coastal cutthroat trout in the Rogue River with access to seawater that did not

enter the marine habitat, but moved only within the river. He was also first to identify potamodromous fish sympatric with sea-run fish, and to document that at least some sea-run fish in

the Rogue River migrated only to the estuary and did not enter the open ocean. It is unclear how

widely this form occurs in sympatry with anadromous cutthroat trout, partly because the two

forms are indistinguishable at the juvenile stage, and differences in growth and appearance may

not always be apparent in adults (Jones 1977, Tomasson 1978). In his work on the Rogue River,

Tomasson differentiated between the anadromous and nonanadromous fish by chemical analysis

of scale tissue.

Saltwater-migratory coastal cutthroat trout—In most areas, this is the most familiar lifehistory form of coastal cutthroat trout, and most of the biological information presented in

“General Biology” (p. 8) and the following sections was derived from studies on saltwater

migratory individuals. The juvenile fish migrate from freshwater natal areas in the late winter

and spring to feed in marine environments (estuarine or nearshore) during the summer. They

then enter fresh water in the winter to feed, seek refuge, or spawn, typically returning to sea

water in the spring.

Trophic migratory model

The classification of coastal cutthroat trout into life-history forms may be based more on

convenience than on true biological categories (e.g., Gross 1987), considering the inherent

difficulty in distinguishing between forms and the wide variability in migratory patterns. One

way to consider migratory movement in coastal cutthroat trout is proposed by Northcote (1997a)

in terms of functional processes in a “migratory/residency spectrum” or cycle (Fig. 13). Not all
46
47

individuals in a population may be involved in such a cycle, and in some systems two or more

different migratory cycles may be present.

In Northcote’s model (1997a), juveniles migrate from natal rearing areas to feeding

habitats, which may be an ocean, estuary, river, or small headwater tributary. They may then

migrate to a refuge area for overwintering; the migration may be from the sea to the river or from

the river to the headwater tributary. In the spring, the individual may migrate back to a feeding

habitat (and repeat this for several years), or may migrate to the spawning area and begin the

cycle all over again. This individual behavior does not exclude the likelihood that natural

selection has led to adaptations in some populations primarily for anadromous migrations or for

remaining in headwater areas. The migratory cycles suggested for coastal cutthroat trout by

Northcote may be considerably more complex than those proposed for anadromous Dolly Varden

in Alaska by Armstrong and Morrow (1980) and Bernard et al. (1995). Armstrong and Morrow

(1980) hypothesized that Dolly Varden may follow two basic migratory pathways. The first

pathway applies if the fish spawn in a watershed with a lake: they simply move in the spring to

the marine environment and in the fall to a lake in their natal watershed. They feed during the

summer in the marine environment and overwinter (and eventually spawn) in the natal

watershed. The second pathway occurs if the natal watershed lacks a lake. In this case, the fish

follow the first pathway until the fall, when they must find a nonnatal watershed with a lake for

overwintering. They return to the natal watershed only to spawn and must leave after spawning

to return to the lake in their nonnatal watershed. Bernard et al. (1995) suggested these pathways

may be oversimplified, and argued that some fish (14-58% in their study) may overwinter at sea

for at least 1 year.

Mechanisms of life-history expression

For any organism, life-history diversity represents both opportunities for and constraints

to adaptive evolution. An organism’s life history is its repertoire of attributes affecting its fitness

(Roff 1992, Stearns 1992), what Williams (1966) called its “design for survival.” These

attributes are those affecting development, growth, dispersal, and reproduction, including traits

such as fecundity, offspring size, migratory propensity, size and age at maturity, and

reproductive schedule. The high degree of genetic differentiation (at presumably neutral genes)

among some coastal cutthroat trout populations demonstrates that there is also ample opportunity

for local adaptations to arise. The complexity of life-history variation in coastal cutthroat trout

undoubtedly reflects in part such adaptations, but major life-history trait variations also can occur

due to genetic drift in isolated populations or in those founded by few individuals. Understanding the underlying basis of variation in life-history traits is necessary in order to make

predictions about the responses of coastal cutthroat trout populations to changes in their

environment.

Life-history traits, like most quantitative traits, are thought to reflect expression of several

(perhaps very many) genes, many of which have small effects on the phenotype (Falconer 1989).

The form of gene expression can be very complex; in addition, life history traits are typically

sensitive to environmental as well as genetic influences (Hard 1995). The observation that
48

heritabilities of life-history traits in fishes are generally low has been used to infer that genetic

variation is lower for these traits than for other quantitative traits (Kirpichnikov 1981, Allendorf

et al. 1987, Tave 1993, Hard and Hershberger 1995), possibly owing to past selection. However,

because it is a relative measure, low heritability may reflect high environmental variance more

than low genetic variance (Price and Schluter 1991); therefore, life-history traits may have

substantial genetic variance and can still respond rapidly to selection. Consequently, life-history

variability can represent a potentially enormous store of genetic resources in a population.

The range of total phenotypic variation observed in a population is due to the net effects

of genotypic and environmental variation and the interaction between genotypes and their

environment (Falconer 1989). Understanding the underlying causes of phenotypic variation is

important for predicting individual and population-level responses to changes in the selective

environment. At one extreme, phenotypic variation in a population could be due entirely to

genetic variation—that is, novel phenotypes each are associated with a novel genotype. At the

other extreme, phenotypic variation could be purely a reflection of variation in environmental

conditions, with absolutely no genetic variation existing among individuals. In this latter

scenario, a population fixed for a particular genotype could still exhibit a broad phenotypic

distribution because of high levels of spatial or temporal environmental variation experienced by

individuals. Phenotypic variation resulting from the range of phenotypic responses from a

particular genotype under different environmental conditions is called “phenotypic plasticity”

(Stearns 1989, Via 1993). The actual underlying control of the variation observed in many

phenotypic traits is likely to be a combination of these two scenarios.

Regardless of the mechanisms producing phenotypic variation in a population, changes in

the environment will result in a shift in the range of observed phenotypes in a population.

However, the expected longer-term response of a population to environmental change will be

greatly influenced by the underlying control of phenotypic variation. If the range of phenotypic

variation observed in a population is due to genetic variation, changes in the environment would

result in a shift in the observed phenotypic distribution because certain genotypes would be

favored over others. In such a case, the range of phenotypes that could be produced in the future

is reduced during every generation of selection. Alternatively, a population whose phenotypic

variation is due to phenotypically plastic responses of genotypes to environmental variation can

continue to produce a broad array of phenotypes generation after generation.

 Phenotypic plasticity can be a less costly means of increasing a population’s phenotypic

repertoire without the genetic costs incurred by polymorphism and appears to be favored in

environments that are highly variable, either spatially or temporally (Bradshaw 1965, Via 1987).

However, the evolutionary benefit afforded by phenotypic plasticity depends in part on how

reliably organisms can “anticipate” environmental change (Bradshaw 1986): if organisms cannot

produce an appropriate phenotype in response to an environmental challenge, plasticity provides

no advantage over genetic polymorphism as a mechanism for maintaining phenotypic variation.

Phenotypic plasticity may manifest itself as the “flexibility” in life history that an

individual might express over the course of its life cycle. Such flexibility probably involves
49

more than simple behavioral or physiological adjustment to environmental variation. This

plasticity should be most pronounced when the temporal variability in the environment within

generations is greater than that between generations. But the effect on the phenotypic response

of individual genotypes also depends on the degree of spatial environmental heterogeneity,

which tends to lead to higher specialization if the spatial component is large and the withingeneration temporal component is small (Lynch and Gabriel 1987). For coastal cutthroat trout,

some evidence supports the existence of “generalist” life-history phenotypes, which could arise

rapidly if both spatial and temporal heterogeneity in the environment are substantial.

There is evidence that at least some individual coastal cutthroat trout adopt a complex

(and perhaps plastic) migratory strategy. For example, an individual might spend several years

in a nonmigratory or freshwater migratory phase before migrating to seawater for a period of up

to a few months, return to fresh water to spawn or overwinter, and then repeat this cycle (or a

variation of it) one or more times (see Giger 1972, Tomasson 1978, Fuss 1982). This diversity

expressed by individual fish may represent several possible responses to environmental

conditions, options that are rare in Pacific salmon. Why? It is possible that Pacific salmon

exhibit fewer migratory behaviors because reproductive options are limited, especially after

smoltification (Thorpe 1987).

There are a number of possible adaptive explanations for the observed range of

phenotypic variation in life history traits in coastal cutthroat trout. Behavioral or physiological

adjustment (including dispersal or migration) that allows individuals to cope with environmental

variation probably occurs to some degree. The success of such adjustments is typically highest

when environmental variation is relatively weak and/or the spatial scale of environmental

variation is small relative to the scale over which dispersal occurs. Selection also may favor a

form of “bet hedging” when individuals must spread their reproductive risk (den Boer 1968,

Stearns 1976) by producing a wide array of offspring phenotypes, only a fraction of which might

be able to cope with the environment they encounter (Kaplan and Cooper 1984, Bull 1987). This

tactic has a high cost, however, and is expected to be favored only in highly unpredictable

environments (Hard 1995). For salmonids like coastal cutthroat trout that show mixed migration

strategies, Jonsson and Jonsson (1993) suggested that in a single mating parents may produce

offspring with different migratory strategies, but this has not been confirmed experimentally for

coastal cutthroat trout.

The observed complexity in life-history traits in coastal cutthroat trout likely reflects (at

least in part) unique adaptations to local environments–attributes that are important to the

diversity of an ESU. Another significance of this complexity may be to provide populations with

a fundamental means of coping with environmental change. In fact, the extent of this variation

in systems in which migratory fish are present may also constitute our most reliable indicator of

population resilience and ESU status. For example, anecdotal evidence for several river basins

points to relatively healthy nonmigratory coastal cutthroat trout populations but weak or

declining anadromous populations, which strongly suggests that saltwater migratory–and even

freshwater migratory–coastal cutthroat trout within the same river basin can experience selective

regimes that are markedly different from their nonmigratory counterparts. However, the
50

consequences of this disparity in population trends depend heavily on the extent to which this

life-history variation is genetically controlled. Unfortunately, we are unaware of any information

that bears directly on the genetic basis of life-history variation in any coastal cutthroat trout

population.

Life-History Stages

Spawning

Anadromous cutthroat trout spawning typically starts in December and continues through

June, with peak spawning in February (reviewed in Pauley et al. 1989, Trotter 1989). In

California, spawning is reported to begin in November, with peak spawning in late December in

larger river basins and late January and February in the smaller coastal rivers and streams (e.g.,

Howard and Albro 1995, 1997; Gale 1996, 1997; Taylor 1997). Redds are primarily built in the

tails of pools in streams with low stream gradient and low flows, usually less than 0.3 m3/s

during the summer (Johnston 1982). The size of coastal cutthroat spawning streams is well

summed up by R. Dimick, founder of Oregon State University’s Department of Fisheries and

Wildlife: “You can step across a cutthroat spawning stream, but you have to jump a steelhead

stream” (C. Bond8 ).

Generally, spawning occurs upstream of coho salmon and steelhead spawning zones,

although some overlap may occur (Lowry 1965, Edie 1975, Johnston 1982). It is believed that

this choice by coastal cutthroat trout of spawning sites in small tributaries at the upper limit of

spawning and rearing sites of coho salmon and steelhead has evolved to reduce competition for

suitable spawning sites and reduce competitive interactions between young-of-the-year coastal

cutthroat trout and other salmonids. Reduction of juvenile competition may be particularly

important at this early life-history stage, as coastal cutthroat trout typically emerge later and at a

smaller size than fry of these other species (Johnston 1982, Griffith 1988). These spatial

separations may limit hybridization between coastal cutthroat trout and rainbow trout or

steelhead. In many drainages where rainbow and coastal cutthroat trout coexist, a slight

difference in spawn timing between the two species is believed to reduce the opportunity for

hybridization (Cramer 1940, DeWitt 1954, Sumner 1972, Glova and Mason 1977, Johnston

1982). However, as discussed in “Hybridization between cutthroat trout and O. mykiss” (p. 76),

hybridization between coastal cutthroat and rainbow trout has been documented in a variety of

locations throughout Washington, Oregon, and California where spawning areas and time of

spawning overlap (Campton and Utter 1985, Hawkins 1997, Taylor 1997; see also “Genetic

Information,” p. 70).

Cutthroat trout are iteroparous, and the incidence of repeat spawning appears to be higher

than in steelhead (Sumner 1953, Giger 1972, Busby et al. 1996). Some fish have been

8

 C. Bond, Department of Fisheries and Wildlife, Oregon State University, Corvallis, OR 97331-

3803. Pers. xommun. to O. Johnson. February 1994
51

documented to spawn each year for at least 5 years (Giger 1972), although some do not spawn

every year (Tomasson 1978) and some do not return to seawater after spawning but instead

remain in fresh water for at least a year (Giger 1972, Tomasson 1978). In general, coastal

cutthroat trout exhibit considerable variation in age and size at maturity. Nonmigratory coastal

cutthroat trout typically mature at an early age (2 to 3 years) whereas sea-run cutthroat rarely

spawn before age 4 (Trotter 1991). Larger fish, because of their size, can obtain the best

spawning sites and produce larger eggs (Trotter 1997). In two British Columbia lakes, Jonsson

et al. (1984) found significant differences between sexes, with mature females significantly

larger than mature males. Furthermore, the sex ratio of upstream migrant coastal cutthroat trout

shows a preponderance of females in the migrants (Sumner 1953; Jones 1974, 1975; Wenburg

1998). This observation, combined with anecdotes about large “sea-run” females spawning with

small “cryptically colored” males (discussed in “Patterns of Life-History Variation,” p. 40),

suggest that male coastal cutthroat trout may possess the alternative reproductive tactic of

precocious maturation, similar to coho salmon (Gross 1984) or brown trout (Jonsson 1985).

Although large males tend to be the principal spawners in most populations, small males can dart

in and fertilize some of the eggs. This tactic could be particularly successful for coastal cutthroat

trout because they spawn in small streams that often have numerous places for a small male to

hide near a spawning pair (Jonsson et al. 1984). When large migrant males are absent, small

males may become principal spawners (Jonsson 1985).

Spawners may experience high postspawning mortality due to weight loss of as much as

38% of prespawning mass (Sumner 1953) and other factors (Cramer 1940, Sumner 1953, Giger

1972, Scott and Crossman 1973). Still, in one Oregon stream, over 39% of one year’s spawning

population returned to spawn the next year, 17% for the third year, and 12% for the fourth year

(Sumner 1953). However, in another stream with an intense sport fishery, only 14% returned to

spawn in the second year (Giger 1972).

Cutthroat trout are among the salmonids most vulnerable to overharvest by angling

(Gresswell and Harding 1997) (see “Assessment of Extinction Risk,” p. 135), especially during

postspawning outmigrations to summer feeding areas. This relatively heavy harvest mortality on

repeat spawners has been a concern of biologists in the Pacific Northwest for many years (Giger

1972, Johnston 1982, Gresswell and Harding 1997), especially as first-year coastal cutthroat

spawners often have fewer and poorer quality eggs than do repeat spawners (J. Hunter9

).

Incubation and emergence

Eggs begin to hatch within 6-7 weeks of spawning, depending on temperature; alevins

emerge as fry between March and June, with peak emergence in mid-April (Giger 1972, Scott

and Crossman 1973). At emergence, fry quickly migrate to channel margins and backwaters,

where they remain throughout the summer (Glova and Mason 1976, Moore and Gregory 1988).

Coastal cutthroat trout are found in streams with channel gradients that vary from low (< 2%) to

9 J. Hunter, WDFW, 600 Capitol Way N., Olympia, WA 98501-1091. Pers. commun. to O.

Johnson. June 1998.
52

moderate (2-3%) or steep (> 4%), with narrow widths (0.7-3.0 m) (Hartman and Gill 1968, Edie

1975, Glova 1978, Moore and Gregory 1988, Jones and Seifert 1997), and often in small

watersheds with drainage areas under 13 km2 (Hartman and Gill 1968).

There is some disagreement in the literature regarding the preferred habitat type of

coastal cutthroat trout fry. When they are the only salmonid in the stream, age-0 coastal

cutthroat trout are more abundant in pools, but use riffles and glides as well (Glova 1984). In

contrast, in sympatry with coho salmon fry and sculpins, coastal cutthroat trout are fairly evenly

distributed between all three habitat types (Glova 1978, 1987). The reduced use of pools while

in sympatry has been interpreted as evidence that coastal cutthroat trout are relegated to riffles by

socially dominant coho salmon (Glova 1978, 1984; Johnston 1982; Trotter 1997). Other authors

have found that underyearling coastal cutthroat trout select the shallower and faster waters in

riffles (June 1981, Bisson et al. 1982, Bisson and Sedell 1984, Mitchell 1988) but may reduce

their use of this habitat type in the presence of steelhead (Bisson et al. 1982). In winter, coastal

cutthroat trout move to pools near log jams or overhanging banks (Bustard and Narver 1975).

Juvenile movements

Coastal cutthroat trout parr generally remain in upper tributaries until they are 1 year of

age, when they may begin moving more extensively throughout the river system. Once these

movements begin, it is difficult to determine whether fish caught in upstream or downstream

traps are parr making a freshwater migration, or smolts on a seawater-directed migration; many

unpaired coastal cutthroat trout of similar size caught in these traps have characteristics of either

life-history stage or intermediate characteristics (Tomasson 1978, Fuss 1982). In Oregon, Lowry

(1965) and Giger (1972) found that downstream-directed movement by juveniles in the Alsea

River system began with the first spring rains, usually in mid-April with peak movement in midMay. Giger (1972) also reported that some juveniles entered the estuary and remained there over

the summer but apparently did not smolt or migrate to the open ocean. He was unable to

determine how many of these “parr” continued moving seaward and how many remained in the

estuaries. Such movement further confounds the difficulty in separating nonanadromous

downstream migrations from seaward migrations.

In Oregon, Washington, and British Columbia, upstream movement of juveniles with parr

marks from estuaries and mainstems to tributaries began with the onset of winter freshets during

November (Giger 1972, Moring and Lantz 1975, Cederholm and Scarlett 1982, Hartman and

Brown 1987, Garrett 1998) and continued through the spring, frequently peaking during late

winter and early spring (Cederholm and Scarlett 1982, Hartman and Brown 1987, Garrett 1998).

Many of these yearling fish averaged less than 200 mm in length (Moring and Lantz 1975,

Garrett 1998) and were found in streams that ran through ponds or sloughs (Hartman and Gill

1968, Garrett 1998).
53

Smoltification and seawater entry

Smoltification involves a number of behavioral, morphological, and physiological

changes that prepare juvenile salmonids for their trophic migration to the sea (Fontaine 1975,

reviewed in Clarke and Hirano 1995). Some authors consider the transformation of juvenile

salmon from freshwater parr to seaward-migrating smolt as a “metamorphosis” (Wald 1958). An

essential part of smoltification is an increase in euryhalinity, which allows the smolt to live in

salinities varying from fresh water to full-strength seawater. For Pacific salmon and steelhead,

the biochemical transformation during smoltification has been well studied (Clark and Hirano

1995), and several “smoltification indices” have been developed (e.g., Zaugg and McLain 1970,

1972; Zaugg and Wagner 1973; Folmar and Dickhoff 1980, 1981; Zaugg 1981). Visually,

smoltification is characterized by morphological changes in color and body shape. The first

change is most obvious: smolts lose their juvenile parr marks (oval-shaped and darkly

pigmented melanin bars on the lateral surface) and take on a silvery sheen caused by the

accumulation of guanine and purine in the scales and superficial dermal layers of the skin.

Secondly, the weight-to-length ratio declines, resulting in a more streamlined body shape.

No studies have been conducted to develop a biochemical “smoltification index” for

coastal cutthroat trout. Furthermore, some coastal cutthroat trout migrate to estuaries in the

spring and, at least on the Oregon coast (Giger 1972, Sumner 1972, Tomasson 1978) and in the

Cowlitz River on the Lower Columbia River (Tipping 1981), will remain in the estuary

throughout the summer, returning to fresh water in the fall. In the Rogue River, Tomasson

(1978) concluded from chemical analysis of scales that coastal cutthroat trout did not enter the

open sea, but remained in the estuary throughout the summer. Tomasson (1978) speculated that

sea-run Rogue River coastal cutthroat trout may remain in the estuary to avoid predation by

steelhead called “half-pounders” that do not conduct long oceanic migrations, instead residing

during the summer in the nearshore ocean where sea-run cutthroat trout usually occur. Still, all

fish that enter and reside in an estuary for several months need to be able to adapt to varying

concentrations of salt water, especially during summer months when freshwater flow and runoff

is minimal.

Some coastal cutthroat trout do undergo complete smoltification, and these fish have been

best identified from open ocean samples. Loch and Miller (1988) and Pearcy et al. (1990) both

report capturing sea-run cutthroat trout as far as 66 km offshore that lacked the marking of searun O. c. clarki caught in estuaries. The fish caught in the open ocean were “very silvery, and

could only reliably be distinguished from steelhead by the presence of basibranchial teeth”

(Pearcy 1997).

Researchers have found that coastal cutthroat trout that enter the sea generally do so after

2-4 years in the freshwater environment (Sumner 1962, Lowry 1965, Giger 1972, Michael 1980,

Fuss 1982) (Table 4, Fig. 14). (Notable exceptions to this are summarized in studies from Alaska that

indicate a majority of the emigrants are between 4 and 6 years of age at initial seawater entry

(Armstrong 1971, Jones 1978) (Table 4, Fig. 14). Time of initial seawater entry of smolts bound

for the ocean generally occurs between March and July (Table 4, Fig. 15), varies by locality, and
54
55
56
57
58
59

may be related to marine conditions or food sources (Sumner 1953, 1972; Lowry 1965, 1966;

Giger 1972; Johnston and Mercer 1976; Trotter 1989). In California, smolt emigration typically

begins in March and continues through June and July, with peak migration in April and May

(Redwood National Park 1983, 1988-1993, 1997, 1998; Brown 1988; Mitchell 1988; Lintz and

Noble 1990; Lintz and Kisanuki 1991; Shaw and Jackson 1994; Gale 1996, 1997; Simondet

1997; Voight and Hayden 1997). In Washington and Oregon, entry begins as early as March,

peaks in mid-May, and is essentially over by mid-June (Sumner 1953, 1972; Lowry 1965; Giger

1972; Moring and Lantz 1975; Johnston 1982). In Alaska, the migration begins in April and

peaks in late May or early June (Baade 1957, Armstrong 1971, Jones 1976), although two

additional surges may occur in mid-June and mid-July. Jones reported that the mid-June surge

was composed of outmigrating coastal cutthroat trout over 250 mm and indicated “these were not

believed to be initial migrant smolts.” Jones (1976) also found that the average size of

outmigrants in a mid-July migration peak at Petersburg Creek in Alaska was less than 200 mm

(Table 4). This run occurred at night on moderate stream flows and stopped during extreme high

or low stream flows.

It has been suggested that seaward migration of smolts to more protected areas (e.g.,

Puget Sound or the Columbia River) occurs at an earlier age and smaller size than migration to

more exposed areas (e.g., the outer Washington coast) (Johnston 1982). Johnston (1982) also

reported that in Puget Sound and the Columbia River smolts make their first migration at age 2,

at a mean size of about 160 mm (Table 4). On the California, Oregon, and Washington coasts,

coastal cutthroat trout make their initial seawater migration between ages 2 and 3, with a few

age-4 migrants of mean sizes ranging from 150 to 255 mm (Lowry 1965; Giger 1972; Sumner

1972; Fuss 1982; Redwood National Park 1983, 1988-93; USFS 1995). However, studies on age

and size at initial seawater entry are rare (Table 4, Figure 14; see also Table C-2 in Appendix C

for additional life-history data acquired after the final BRT meeting), and ages or lengths at

initial entry are often back-calculated using scales from returning adults in creel surveys

(Knudsen 1980). These back-calculations are difficult and may often be inaccurate (Knudsen

1980). While Johnston’s hypothesis (1982) is plausible, more studies are needed to confirm its

validity. The oldest recorded initial age of seawater entry was a 6-year-old 280-mm fish from

the Alsea River in Oregon (Giger 1972).

Estuary and ocean movement/migration

Coastal cutthroat trout that enter nearshore waters reportedly move moderate distances

along the shoreline but do not cross large bodies of open water (e.g., Jones and Seifert 1997,

Pearcy 1997). Sumner (1953, 1972) reported that, in the Nestucca River and Sand Creek,

Oregon, coastal cutthroat trout moved from stream to stream for more than 68 km. Studies by

Giger (1972) in Oregon and Jones (1973, 1974, 1975) in Alaska indicated that coastal cutthroat

trout, whether initial or seasoned migrants, remained at sea an average of only 91 days, with a

range of 5 to 158 days. In these studies, the majority of coastal cutthroat trout seemed to migrate

in similar patterns from year to year, rarely crossed bodies of water more than 8 km in width, and

closely followed shorelines, sometimes for up to 71 km. Jones and Seifert (1997) radio-tagged

coastal cutthroat trout in Auke Lake and Lake Eva in southeastern Alaska to monitor their
60

movement. These fish traveled a maximum of 52 and 26 shoreline km, respectively, but did not

cross extensive open-water channels.

However, these shoreline migratory patterns may not represent the behavior of all coastal

cutthroat trout. For example, two fish captured and tagged offshore migrated much further

distances (Pearcy et al. 1990): One fish, released near Cape Disappointment on the northern

Oregon coast, was recovered in the Umpqua River, 290 km to the south; another fish released off

Yaquina Head was recovered 43 days later in the Siuslaw River, 72 km to the south. Pearcy

(1997) argued that these and other data (e.g., Giger 1972, Pearcy and Fisher 1988) suggest that

sea-run cutthroat trout along the Oregon coast may swim and/or be transported with the

prevailing currents long distances during the summer.

It is not clear how far offshore coastal cutthroat trout migrate. Most researchers have

found that the subspecies remains in nearshore waters. Sumner (1953, 1972) reported that

coastal cutthroat trout were routinely caught up to 6 km off the mouth of the Nestucca River.

Jaenicke and Celewycz (1994) did not catch any cutthroat trout using offshore purse seines in

southeastern Alaska, but these fish were captured with beach seines inshore of the same area

(Pearcy 1997).

The hypothesis that coastal cutthroat trout will not cross large bodies of open water may

not hold true near the Columbia River plume. In offshore sampling studies with fine-meshed

purse seines, coastal cutthroat trout were captured between 10 and 46 km offshore (Dawley et al.

1978, 1979, 1980; Loch and Miller 1988; Pearcy et al. 1990). These fish may have been carried

out to sea in the freshwater plume of the Columbia River, or they may have moved offshore in

search of prey. As previously discussed, these fish were silvery in color, lacking the spotting of

their nonmigratory or estuarine counterparts, and could only be distinguished from steelhead by

the presence of basibranchial teeth (Pearcy 1997). These reports might imply that sea-run

cutthroat trout are more common offshore than previously reported but are often misidentified as

steelhead.

The relatively brief exposure of sea-run cutthroat trout to seawater, compared to other

anadromous salmonids, should not necessarily be construed as an indication that the marine

phase of the life cycle is less important for sea-run cutthroat trout. The relative importance of the

marine phase may vary among populations, at least on relatively large geographic scales,

depending on conditions in estuaries and nearshore habitats (Reeves et al. 1997). In some coastal

cutthroat trout populations, only a small proportion of the individuals may be anadromous

(DeWitt 1954, Gerstung 1997), a condition also found in O. nerka and O. mykiss but rare in other

Pacific salmonid species. Thus, although the marine phase can be very important to sea-run

cutthroat trout in enhancing opportunities for growth and dispersal to neighboring drainages, the

freshwater phase may be relatively more important for juvenile growth and survival in sea-run

cutthroat trout than for other anadromous salmonids, at least in some populations where estuaries

are small or nearshore habitat is limited.
61

Adult freshwater migrations

Coastal cutthroat trout may return to freshwater feeding/spawning areas from late June

through the following April (Table 5, Fig. 15, and Table C-2). Re-entry timing has been found to

be temporally consistent from year to year within streams, but varying widely between streams

(Giger 1972). As in other species of anadromous salmonids, entry to large rivers seem to occur

consistently earlier than to shorter coastal rivers (Giger 1972, Johnston and Mercer 1976,

Johnston 1982). In small streams, such as Carnation Creek in British Columbia, Minter Creek in

Washington, and Sand Creek in Oregon, peak returns occur in December and January, and fish

may continue to return through March (Sumner 1953, Anderson and Narver 1975, Johnston

1982). These streams usually have low flows (< 0.6 m3/s). Sumner (1953) found fall-winter

movements in Sand Creek, first with large adults (up to 10 years old), followed by smaller (<25

cm) mature freshwater migrants coming from the lower reaches of the estuary. In the Nestucca

River, Sumner reported a late reproductive migration in early to mid-May, with large ripe

females in rivers as late as June.

In large river systems within Washington and Oregon (such as the Stillaguamish,

Columbia, Cowlitz, Alsea, and Umpqua rivers), coastal cutthroat trout return migrations usually

begin as early as late June and continue through October, with peaks in late September and

October (Lavier 1963; Bulkley 1966; Hisata 1971, 1973; Duff 1972; Giger 1972; Wright 1973;

Tipping and Springer 1980; Tipping 1981, 1986; ODFW 1993a). On the Alsea River, for

example, Giger (1972) reported that the earliest known entrance dates of sea-run cutthroat trout

into the Alsea River between 1965 and 1970 ranged from June 23 to July 21. Giger also noted

that these first fish were the “forerunners of larger runs which peaked at later dates” and that

“smaller numbers of fish were known to enter as late as early October” (Giger 1972, p. 11). He

also suggested that the early run of fish in the Alsea River may consist of older fish, with firsttime spawners making up the later October-November run. Similarly, in the Umpqua River,

Oregon Department of Fish and Wildlife (ODFW) biologists (ODFW 1993a) reported that

coastal cutthroat trout at Winchester Dam historically began upstream migrations in late June and

continued to return through January (Fig. 15), with bimodal peaks in late July and October.

In California rivers with year-round access to the Pacific Ocean, adult immigration

typically begins in late July and continues through December, with peak migration in September

and October (CDFG 1980-89; Voight and Hayden 1997; McCain unpubl. data; Gale 1996, 1997;

Simondet 1997). In smaller California rivers and coastal lagoons with seasonal river sand bars

that block access to the ocean, adult immigration begins with the first opening of the sand bar

(usually with the first large freshet in November or December) and continues through March,

with peak migration typically in January and February (Redwood National Park 1983, 1988-93;

Taylor 1997).
62
63
64
65
66

Straying and refuge or feeding migrations versus reproductive straying

Few tagging studies of coastal cutthroat trout (e.g., Giger 1972; Jones 1975,1976; Jones

and Seifert 1997) address the question of straying rates. Studies that have been conducted often

use hatchery fish (Giger 1972), whose behaviors may differ from natural fish. Most studies are

also confounded by the difficulty in distinguishing overwinter nonreproductive migrations from

spawning migrations (Jones 1975, 1976; Jones and Seifert 1997).

In tagging studies on Petersburg Creek in southeastern Alaska, Jones (1975, 1976)

reported that many tagged natural fish wandered to nearby streams during their first year’s return

to fresh water. As second-year migrants, a much higher proportion of tagged fish were captured

in their home stream. Overall, Jones (1976) found that less than 50% of initial returning

migrants were sexually mature and suggested that first-year fish found wandering to nonnatal

rivers were on feeding runs.

From 1966 to 1970, Giger (1972) conducted more than 23 separate releases of marked

Alsea River hatchery fish into the Nestucca, Alsea, and Siuslaw rivers in Oregon. A planned

comparative study with natural fish could not be assessed because of low numbers of

outmigrants tagged and tag losses at sea. Unfortunately, most of the data collection occurred in

the same year or the year following the release, and it is not possible to tell whether these were

true strays or juveniles on feeding or refuge migrations. However, extensive data were collected

and analysis reveals a complex pattern of coastal cutthroat trout movement among these three

rivers. Apparent directional straying southward along the coast was found in four of the five

years studied. Giger attributed the directionality in straying to marine conditions such as ocean

currents rather than to behavioral characteristics. He also suggested the straying may result from

poor imprinting on rivers where the fish are released due to the speed of out-migration after

release. The average percentage of fish straying varied from 0% (Siuslaw to Nestucca rivers) to

18.4% (Alsea to Siuslaw rivers). The greatest magnitude of straying for a single release (out of a

total of 23 separate release groups) was for a May 1967 Alsea River release from which nearly

30% of the fall returns were taken in the Siuslaw River fishery.

Like Jones (1976), Johnston (1982) suggested that sexually immature first-year migrant

coastal cutthroat trout may conduct feeding runs to nonnatal rivers. Johnston also proposed that

the fish will home to natal streams the following year, when a larger proportion are sexually

mature.

Interactions of Coastal Cutthroat Trout with Other Salmonids

Studies of the fossil record and natural distributions of Pacific salmon and trout suggest

that coastal cutthroat trout may have been the first salmonid to colonize the western United

States (Behnke 1992). Many coastal cutthroat trout populations became well established before

other species of salmonids were abundant, and they remained isolated from these other species

for thousands of years (Behnke 1979, 1992; Johnston 1982). As an example, the only native fish
67

historically present with the Yellowstone cutthroat trout in Yellowstone Lake, Wyoming, was the

longnose dace (Rhinichthys cataractae) (Gresswell and Varley 1988). In another example, only

eight other fish species historically occurred in the Lahontan Basin in Nevada and California

along with the Lahontan cutthroat trout (Behnke 1992).

Because of this isolation, many interior species of cutthroat trout never competed with

other salmonid species, and introductions of other salmonids (primarily rainbow trout) into the

American west resulted in a dramatic decline of many interior cutthroat trout populations

(Greswell 1988, Behnke 1992). This decline occurred in part through habitat modification and

destruction (e.g., Clancy 1988), but is primarily attributed to interspecific interactions such as

introgressive hybridization (Behnke 1992; Allendorf and Leary 1988), predation (reviewed in

Marnell 1988), and competition (Griffith 1988).

It is worthwhile noting that one study (Platts 1974) found that westslope cutthroat trout

density peaked at a channel gradient of about 10%, a steeper gradient than is associated with

peak densities of bull trout, rainbow trout, or brook trout (Salvelinus fontinalis). Platts suggested

that the cutthroat trout in this study represented populations in gradients least preferred by other

salmonids.

Coastal cutthroat trout are believed to have been less severely affected by these

interspecific interactions because they evolved in close contact with other salmonids. Coastal

cutthroat trout have developed a variety of habitat-partitioning techniques and life histories, all of

which may reduce competition with other species and help reduce opportunities for hybridization

(Johnston 1982, Campton and Utter 1987, Griffith 1988).

Cutthroat trout have been documented to change their behavior in the presence of other

salmonids such as steelhead/rainbow trout (reviewed in Griffith 1988), char (Andrusk 1968,

Andrusak and Northcote 1970, Northcote 1995) and coho salmon (Glova 1984, 1986). In studies

where cutthroat and rainbow trout or steelhead occupied the same watersheds, cutthroat trout

have been found primarily in the headwater tributaries, while steelhead and rainbow trout

occupied the larger river reaches (Hartman and Gill 1968, Edie 1975, Hanson 1977, Jones 1978,

Nicholas 1978a, Johnson et al. 1986). Nicholas (1978a) also found that cutthroat trout in western

Oregon streams grew more slowly and matured at an earlier age than did sympatric rainbow

trout. Cutthroat trout also spawned earlier in the spring and in smaller or different tributaries

than did rainbow trout. Nicholas believed this resource partitioning reduced the opportunity for

hybridization and helped maintain the integrity of the cutthroat trout populations.

In a study of lacustrine populations, Nilsson and Northcote (1981) found that coastal

cutthroat trout showed changes in behavior, prey, and growth in the presence of rainbow trout.

In laboratory studies, the rainbow trout were consistently more aggressive and quickly killed

coastal cutthroat trout when paired together. However, the two species successfully coexisted in

natural lake environments (Nilsson and Northcote 1981).
68

Dolly Varden and bull trout have also evolved sympatrically with coastal cutthroat trout

in the Pacific Northwest (Brown 1992). Like coastal cutthroat trout, these char may use a variety

of habitats, including lakes, marine areas, rivers, ponds, and headwater tributaries. However,

these species seem to be partitioned by a temperature gradient, and char are seldom found in

streams with summer temperatures exceeding 18°C (Allan 1980, Shepard et al. 1984). In

northern Puget Sound tributaries, Dolly Varden apparently also spawn and rear higher in

headwater tributaries than do coastal cutthroat trout. Kraemer11 suggests this is due to an

8°C spawning threshold for Dolly Varden. In Washington, Wydoski and Whitney (1979) report

Dolly Varden spawning activity was most intense at 5°C to 6°C. Studies of Dolly Varden and

coastal cutthroat trout occurring together in lakes have generally concluded that, in competitive

situations, the char tend to be excluded from the upper water column and feed on benthic prey

while coastal cutthroat feed on surface prey (Andrusak and Northcote 1971, Schutz and

Northcote 1972).

Juvenile coho salmon have also been shown to be dominant over juvenile cutthroat trout

in field (Giger 1972, Glova 1984) and laboratory studies (Glova 1986, Sabo and Pauley 1997).

However, in both kinds of studies, coho salmon were dominant only when they were larger than

cutthroat trout (Sabo and Pauley 1997). In the absence of larger coho salmon, cutthroat trout

prefer to rear in pools (Giger 1972). When coho salmon are present, they virtually always

dominate cutthroat trout fry because the juvenile coho salmon emerge from redds earlier and are

large (Giger 1972, Sabo and Pauley 1997). Cutthroat trout juveniles then move to less-preferred

lower-gradient riffle areas, where they remain until winter flows force changes because of

displacement (Glova 1984, 1987; Glova and Mason 1977).

At least one subspecies of interior cutthroat trout has evolved sympatrically with other

Pacific salmonid species; westslope cutthroat trout and rainbow trout/steelhead coexist in the

Snake River Basin (Hanson 1977). In a study of abundance and distribution of the two species,

Hanson (1977) found that in drainages where both occurred, cutthroat trout occupied upper

portions of the stream and O. mykiss the lower portions. Hanson also determined that age-0

steelhead were larger than age-0 cutthroat trout and displaced previously established age-0

cutthroat trout, but that the smaller cutthroat trout could not displace steelhead. Hanson

suggested there is “interactive segregation” of the co-occurring species despite–or because of–

their apparent coexistence for thousands of years.

The effect of these interactions is not clearly understood and may differ depending on a

variety of factors. Although cutthroat trout may be competitively excluded from preferred

rearing habitats by larger coho salmon (Glova 1984, 1986, 1987) and steelhead (Hartman and

Gill 1968), it has been suggested that in some cases this interaction may be positively correlated

to anadromous cutthroat trout abundance. In Cummins Creek, which is contained within a

wilderness area on the Oregon coast, cutthroat trout seem to grow more slowly and fewer smolts

outmigrate in years with poor coho salmon runs. Coho salmon may consume some age-0

cutthroat trout, but it has been suggested that this may allow the remaining cutthroat trout to

11 C. Kraemer, WDFW, 16018 Mill Creek Blvd., Mill Creek, WA 98012-1296. Pers. commun. to O.

Johnson. July 1998.
69

grow faster and result in better survival of anadromous cutthroat trout populations

(T. Nickelson12 ).

Temperature Tolerance in Coastal Cutthroat Trout

Coastal cutthroat trout are exposed to a wide range of water temperatures across their

distribution and, relative to other salmonids, little information on their habitat requirements is

available (Hunter 1973, Golden 1975, Bjornn and Reiser 1991). Still, like other salmonids,

coastal cutthroat trout have evolved to take advantage of temperature regimes in their home

ranges. When abrupt changes occur in water temperatures or other physical factors, the fish

usually compensate by seeking refugia, but changes from the normal pattern can reduce their

survival (Golden 1975, Bjornn and Reiser 1991).

In several studies (Hunter 1973, Golden 1975, Behnke and Zarn 1976, Behnke 1992),

cutthroat trout, like other salmonids, were not usually found in water temperatures higher than

22°C, although they could tolerate temperatures as high as 26°C for brief periods. Typically,

adult fish appeared stressed when water temperatures rose above 22°C. At 28°C to 29°C the fish

lost equilibrium and died, even if temperatures were gradually increased 1-2°C per day (Behnke

and Zarn 1976). Juvenile cutthroat trout preferred water temperatures around 15°C. They also

lost equilibrium and died between 28°C and 30°C (Heath 1963). A literature review by Bell

(1986) reported lower and upper lethal temperatures of 0.5°C and 23°C for coastal cutthroat

trout. Optimum temperatures for spawning ranged from 6.1°C to 17.2°C and for egg incubation

from 4.4°C to 12.7°C.

Golden (1975) conducted experiments specifically on coastal cutthroat trout to determine

the effects of fluctuating temperatures on lethal tolerance limits. He found acclimation

significantly affected survival in the subspecies. Fish acclimated to temperatures of 13 to 23°C

had lower survival rates when exposed to high temperatures than did fish acclimated only to

23°C or to temperatures ranging from 13 to 25°C. He also found that fish acclimated to both the

23°C and 13 to 23°C temperatures could withstand exposures to large diel cycles of up to 13 to

27°C daily variation with 10% or less mortality over 7 days.

Dwyer and Kramer (1975) calculated metabolic rates and scope for activity for an interior

subspecies of cutthroat trout from a hatchery in Logan, Utah. In their experimental fish, active

metabolism and the scope for activity was greatest at 15°C and lowest at 5°C. There was also a

metabolic decline at 24°C, which the authors concluded is near the upper lethal temperature for

this subspecies of cutthroat trout.

Temperature tolerance is difficult to study. Behnke (1992) described redband trout

(O. mykiss newberrii) in eastern Oregon that seem to have adapted over thousands of years to

high water temperatures. He reported that these fish actively feed and apparently thrive in waters

12 T. Nickelson, ODFW, P.O. Box 59, Portland, OR 97207. Pers. commun. to O. Johnson. Nov. 1993.
70

of 28.3°C. Other populations do not seem to successfully adapt to high temperatures. In the

Firehole River, Yellowstone National Park, introduced redband trout have lived for 60-70 years

in water temperatures that may reach 29.5°C (Kaya 1977). Adaptation to this warm water might

be expected, but in a series of experiments Kaya (1978) found that these redband trout survived

less than 2 hours at 29.5°C and stopped feeding at 23°C to 24°C, even when water temperature

was gradually increased. He suggested that the fish, rather than adapting to the hot water, were

able to find refuge in cooler water and avoid the higher temperatures.

Based on the above information, the biological significance of temperature, as seen in

southern Oregon and northern California (e.g., the Rogue and Umpqua rivers) and discussed in

the “River Water Temperature” section in Johnson et al. (1994), remains unclear.

Genetic Information

Previous sections examined evidence for phenotypic and life-history differences between

populations or groups of populations of coastal cutthroat trout that might be used to identify

ESUs. The genetic basis of many phenotypic and life-history traits, however, is often weak or

unknown, and consequently population differences in these traits provide little information on

reproductive isolation between populations. The BRT considered molecular genetic evidence

that might be used to define reproductively isolated populations or groups of populations of

coastal cuttroat trout. These genetic markers are presumably unaffected by selection but may

change in response to mutation, genetic flow, and genetic drift. The analysis of the geographical

distributions of these markers may reveal historical dispersals, equilibrium levels of migration

(gene flow), and past isolation. Most of this evidence is based on the analysis of protein variants

(allozymes), microsatellite loci (variable numbers of short tandem deoxyribonucleic acid [DNA]

repeats), and mitochondrial DNA (mtDNA). Genetic variability among populations of coastal

cutthroat trout has been examined throughout much of the geographical range of this species

with allozyme electrophoresis, and in some regions with mtDNA or microsatellite loci.

Available genetic data were also used to assess the relationship between migratory and

nonmigratory populations to understand the effects that nonmigratory populations might have on

anadromous populations. The BRT’s deliberations on defining population units also considered

the effect hybridization with steelhead or rainbow trout would have on genetic population

structure. Unlike other West Coast species of Pacific salmon, coastal cutthroat trout show

evidence of widespread hybridization with O. mykiss.

Statistical Methods

Several standard statistical methods have been used to analyze molecular genetic data to

detect reproductive isolation between populations. Comparisons of genotypic frequencies in a

sample with frequencies expected under random mating (Hardy-Weinberg proportions) may be

used to infer the breeding structure of a population or to detect population mixing (Wahlund’s
71

effect). Contingency table comparisons of allozyme or microsatellite allele frequencies among

population samples with chi-square or G (log likelihood ratio) test statistics or with randomization tests have been used to detect significant differences between populations, which may be

evidence of reproductive isolation.

Another way of assessing genetic isolation between populations is to analyze genetic

distances based on allele-frequency estimates. Several genetic distance measures (e.g., CavalliSforza and Edwards 1967; Nei 1972, 1978) have been used to study the population genetic

structure of anadromous salmonids. It is unclear, however, which measure is most appropriate in

a particular case or whether one measure is always most appropriate. Discussions of the features

of genetic distances appear in Nei (1978), Rogers (1991), and Hillis et al. (1996). Most of this

discussion has focused on the merits of the various measures for phylogenetic reconstruction

among species or higher taxa. To our knowledge, no one has quantitatively evaluated the

performances of these distances in assessing genetic differentiation among populations within

species such as anadromous salmonids, which typically show small genetic distances between

conspecific populations (populations of the same species). An attractive feature of CavalliSforza and Edwards’ distance (Dc) is that it satisfies the triangle inequality; that is, given three

populations (A, B, C), the sum of the distances between A and B and between B and C is always

greater than the distance between A and C. Neither of these genetic distance measures, however,

employs a correction for sample size, so distances are biased upward, especially for small sample

sizes. In contrast, Nei’s (1978) unbiased genetic distance, Dn, corrects for this bias but does not

always satisfy the triangle inequality.

Sample sizes and heterozygosity may also influence the power of the genetic distance

approach to resolve genetic population structure. When sample sizes used to estimate allelic

frequencies are 50 individuals or more, the difference between Nei’s genetic distance (Nei 1972)

and Nei’s unbiased genetic distance (Nei 1978) is small, but might still be a substantial

proportion of D if D is small. When genetic distances between populations are also small, as

they often are between populations of both salmon and anadromous trout, low but significant

levels of genetic differentiation may not be detected by an unbiased distance measure because

sample size corrections may reduce estimates of genetic distance to zero. Another consideration

is that Dn may be affected by different levels of heterozygosity between populations, whereas Dc

apparently is not.

Since it is unclear which distance measure is most appropriate in any given application,

we analyzed sets of data with Nei’s unbiased and Cavalli-Sforza and Edwards’ genetic distances

to identify results that were robust to the choice of the distance measure used. Dn tends to

minimize distances between genetically similar samples consisting of only a few individuals and

ranges from 0.0 (no difference) to infinity. Dc, on the other hand, tends to magnify distances

between closely related samples and diminish distances between distantly related samples. This

measure ranges from 0.0 (identity) to 1.0 (complete dissimilarity). In most cases, the different

genetic distance measures yield highly correlated results.
72

The degree of reproductive isolation between populations can be inferred from an

analysis of the pattern of genetic distances between populations. Clustering methods, such as the

unweighted-pair group method with averages (UPGMA), (Sneath and Sokal 1963) and the

neighbor-joining method (Saitou and Nei 1987), find hierarchical groupings of genetically

similar populations. Multivariate methods, such as multidimensional scaling (MDS) (Kruskal

1964) or principal components analysis (PCA), find groupings of genetically similar populations

in several dimensions, which are depicted here in two or three dimensions. MDS analysis

produces a plot of samples in which the distances between samples in the plot are linearly related

to the genetic distances between them. When the geographical distribution of genetic variability

is not hierarchical or disjunct, such as in a clinal or reticulate pattern of differentiation, MDS and

PCA more accurately depict relationships among samples than do agglomerative methods such

as the UPGMA (Lessa 1990). In a UPGMA analysis, information about the relationship between

the incoming sample and the individual samples already in the cluster is lost; this algorithm

compares the genetic distance of an incoming sample to the average genetic distance between

samples already in a cluster. MDS, on the other hand, is a nonmetric ordination technique that

attempts to find the shortest genetic distances between samples in n-dimensional space without

averaging. A related technique, applying PCA to allelic frequencies, can also be used to examine

genetic relationships among populations. In our experience, the results of a PCA are usually

similar to MDS ordinations for a set of data. A minimum spanning tree between samples can be

used to detect distortions in three-dimensional views of a PCA or MDS ordination. Samples that

appear to be close to one another in one view of an ordination may be far apart in another view.

Reproductive isolation between populations can be inferred from a visual examination of these

plots to find clusters of genetically related populations that were consistent with sample

geography in the clusters.

Various studies have estimated levels of genetic variability within populations because

the level of within-population variability may reflect evolutionary or historical differences in

population size and migration patterns between populations. Within-population gene diversity

was measured by the expected proportion of heterozygous genotypes in a population of randomly

mating individuals averaged over the number of loci examined (H). Estimates of H based on a

small number of individuals are usually accurate, as long as enough loci (>30) are surveyed for

variability (Nei 1978).

Genetic differentiation between populations at various hierarchical levels has been

estimated in many studies with a gene diversity analysis (Nei 1973, Chakraborty 1980), which

apportions allele frequency variability among populations into its geographical or ecological

components. For example, the proportion of the total genetic variability in a set of samples that

is due to differences among populations may be estimated with GST = (HT - HS)/HT, where HS is

the average within-population heterozygosity and HT is the total heterozygosity in the pooled

samples disregarding geographical subdivision. The standardized variance of allele frequencies

among populations, FST, is equivalent to GST when only two alleles occur at a locus. Most

genetic variability in salmonids occurs as genotypic differences among individuals within a

population (Ryman 1983). A smaller proportion of the total variability is due to hierarchical

differences between regions, river systems, tributaries and streams within a river system,
73

between years, or between run types. The range 0.05-0.15 for GST or FST indicates moderate

differentiation, and the range 0.15-0.25 indicates strong genetic differentiation among

populations (Wright 1978). These statistics facilitate comparisons among groups of populations

that may reveal regional differences in gene flow between populations, or the effects of hatchery

strays on levels of differentiation between populations.

Migratory vs. Nonmigratory Populations

One important consideration in defining population units for conservation is to

understand the genetic relationships between the various life-history types of coastal cutthroat

trout, which often occur in the same river drainage. Freshwater migratory and nonmigratory

forms have also been observed in other salmonids, including Arctic char, brook trout, brown

trout, rainbow trout, and sockeye salmon. Small (but significant) allele frequency differences

have been observed between landlocked and anadromous populations of brown trout (Hindar et

al. 1991, Skaala and Naevdal 1989), sockeye salmon (Foote et al. 1989), rainbow trout

(Allendorf and Utter 1979, Currens et al. 1990, Northcote 1970), and Atlantic salmon (Ståhl

1987). The relationship between migratory and nonmigratory individuals, however, varies

between species and between populations of the same species.

For example, Northcote’s study (1969) of migratory behavior in rainbow trout

populations in the Pacific Northwest found a greater tendency for downstream migration in

juvenile rainbow trout from populations below waterfalls than for juveniles from populations

above waterfalls. Rivers below waterfalls would be expected to be more productive than rivers

above falls, due in part to nutrients contributed by returning anadromous fish. More productive

rivers result in faster-growing juveniles with perhaps a greater tendency to outmigrate. A genetic

tendency for nonmigratory behavior would be advantageous at localities above waterfalls and

where downstream migration would lead to the loss of individuals from the upstream population

(Northcote 1992). Historical biogeographic considerations imply that landlocked populations in

each species have been derived from anadromous populations in the same general area, even

though detectable genetic differences occur between nonmigratory brown and rainbow trout

populations isolated by falls or in lakes and nearby sea-run populations of the same species.

The variability of relationships between migratory and nonmigratory individuals is

illustrated by several studies of brown trout in Scandinavia. In a study of allozyme variability,

Hindar et al. (1991) found that samples of sea-run and nonmigratory brown trout (identified by

scale patterns) clustered by locality, rather than by life-history type. Jonsson (1982) found that

juvenile brown trout captured in a lake with sea access migrated downstream more often than

fish captured in a lake above an impassable waterfall migrated upstream. Nevertheless, Jonsson

(1982) found that both sea-run and nonmigratory parents gave rise to progeny that could follow

either life-history pattern. In another study of brown trout, Jonsson (1985) measured migration,

age distribution, age at sexual maturity, growth, and fecundity in migratory and nonmigratory

individuals, and concluded that different life-history types were components of the same genetic

population. In a study of brown trout populations in France, Bagliniére et al. (1989) found both
74

spatial and temporal separation in spawning between migratory and nonmigratory segments of a

population in the same stream.

In coastal cutthroat trout, the genetic significance of nonmigratory, freshwater migratory,

or anadromous fish in populations has been difficult to assess. It is not always possible to

identify individuals in a genetic sample that have migrated or may have been destined to migrate

to the ocean. Scale analysis can be used to infer whether coastal cutthroat trout have migrated to

sea, but analysis of scale growth patterns is not always a reliable means of establishing migratory

behaviors (see “Life History,” p. 38, for a brief discussion of the problems in coastal cutthroat

trout scale analysis). Analysis of otolith growth patterns or microchemistry may provide more

accurate results, but is costly and time consuming and has not been widely used to identify searun fish in genetic studies. Based on studies of other salmonids with sea-run and nonmigratory

life-history patterns, nonmigratory individuals may co-occur with anadromous individuals in the

same stream (e.g., Hindar et al. 1991). The extent to which sea-run and nonmigratory life-history

forms of coastal cutthroat trout co-occur in a particular stream is unknown. Most assessments of

the genetic relationships between migratory and nonmigratory populations of coastal cutthroat

trout have been made by comparing populations above and below barrier waterfalls. Although

the fish may not be able to swim upstream, downstream migration over some waterfalls may still

be possible and may lead to at least one-way gene flow between migratory and nonmigratory

populations.

The level of genetic divergence between migratory and nonmigratory populations of

coastal cutthroat trout also appears to be variable, as are the levels of divergence between lifehistory types in other trouts. Some freshwater populations of coastal cutthroat trout above barrier

waterfalls (possibly nonmigrants or freshwater migrants) show strong genetic differences from

below-barrier populations in the same area. For example, in a study of allozyme variability in

coastal cutthroat trout populations in Hood Canal and northern Puget Sound, Campton and Utter

(1985) found that sea-run populations tended to be genetically more similar to one another than

to an above-barrier freshwater population (Howe Creek) in the Hood Canal drainage.

A study of coastal cutthroat trout populations in a tributary of Washington’s Nisqually

River by Zimmerman (1995) also showed the largest genetic differences between sea-run and

putative nonmigratory populations. Zimmerman (1995) surveyed allele frequency variability at

14 polymorphic allozyme-encoding loci in samples from six localities in Muck Creek and found

the greatest number of significant differences in allele frequency between a sample from

Chambers Lake (with sea-run individuals) and samples taken upstream (considered by their size

and appearance to be from nonmigratory populations). No clear barriers to migration were

present between these sea-run and apparently nonmigratory populations. The amount of

divergence between these two groups, however, was small; genetic distances between the

anadromous population and nonmigratory populations averaged about Dn = 0.01.

Other studies show variable degrees of divergence between sea-run and freshwater

migratory/nonmigrant populations of coastal cutthroat trout. Griswold (1996) sampled coastal

cutthroat trout above and below waterfall barriers (populations below the barrier had access to
75

the ocean) to measure genetic divergence between putative sea-run and freshwater coastal

cutthroat trout populations in the same stream. Griswold (1996) collected samples in two widely

separated river drainages: Vixen Inlet in southeastern Alaska and Elk River, Oregon. Samples

were examined for variability at 41 allozyme loci; 12 were polymorphic in the Elk River samples

and 9 were polymorphic in the Vixen Inlet samples. One of the below-barrier Elk River samples

appeared to contain genetic markers indicating a large number of O. clarki × O. mykiss hybrids

and was not used to make comparisons. For the Elk River samples, the sums of chi square

contingency table tests of allele frequencies between samples were significant for all pairs of

samples except one above- and below-barrier comparison. However, a correction for multiple

tests of the same hypothesis apparently was not made, so the significance of some of these tests

may be due to Type I error. In the Vixen Inlet drainage, all chi square tests were significant

except for one comparison between below- and above-barrier samples. These data together

indicate that below- and above-barrier populations may or may not be genetically different from

each other.

In summary, the few existing studies of cutthroat trout show that, although both allele

frequencies and morphology may differ between populations above barriers and potentially searun populations below barriers, these life-history forms generally show close genetic relatedness

in the same drainage relative to genetic population differences among drainages. These results

indicate that sea-run and freshwater migratory/nonmigratory populations appear to represent a

single evolutionary lineage in which the various life-history patterns have repeatedly appeared in

different geographic regions. Variability in migratory behavior within populations may

nonetheless have some genetic basis.

Hybridization and Introgression

Genetic divergence among subspecies of cutthroat trout

As many as 15 subspecies of cutthroat trout have been recognized, and all but one,

O. c. clarki, are limited to inland waters. A phylogenetic analysis of seven of these subspecies

and of rainbow trout indicated that Yellowstone cutthroat trout consisted of at least five closely

related nominal subspecies (Yellowstone, Colorado, Snake River, greenback, and Rio Grande)

that, as a group, showed substantial biochemical genetic divergence from westslope, Lahontan,

and coastal cutthroat trout (Allendorf and Leary 1988). Nei’s genetic distance between the

Yellowstone complex of subspecies and the remaining three subspecies averaged 0.212

(Allendorf and Leary 1988), which is typical of values between related fish species. Westslope,

Lahontan, and coastal cutthroat trout showed considerably greater divergence from one another

than did the five subspecies of Yellowstone trout. Unexpectedly, a sample of Westslope,

Lahontan, and coastal cutthroat trout were as similar to rainbow trout as they were to the

subspecies in the Yellowstone complex. Coastal cutthroat trout showed nearly the same level of

divergence from rainbow trout (Dn = 0.099) as it did from Lahontan cutthroat trout (Dn = 0.077).

In contrast, morphological (Behnke 1992), karyotypic (Gold et al. 1977, Loudenslager and

Thorgaard 1979, Thorgaard 1983), and mtDNA (Gyllensten et al. 1985, Shedlock et al. 1992)
76

data indicate that the major subspecies of cutthroat trout are more closely related to one another

than they are to rainbow trout. The reason for the close relatedness of rainbow trout to some

subspecies of cutthroat trout is unclear, but may be the result of persistent hybridization in areas

where the species have come into contact with one another.

Hybridization between cutthroat trout and O. mykiss

Several studies have reported hybridization between various subspecies of cutthroat and

rainbow trout and between coastal cutthroat trout and steelhead. Although there is a substantial

genetic (Loudenslager and Gall 1980, Leary et al. 1987, Allendorf and Leary 1987) and

karyotypic divergence in chromosome number between westslope cutthroat (2n = 66) and

Yellowstone cutthroat (2n = 64) trout (Loudenslager and Thorgaard 1979) and between these

subspecies and rainbow trout (2n = 60, Gold 1977), westslope cutthroat trout hybridize with both

taxa. Allendorf and Leary (1988) found evidence of hybridization between westslope cutthroat

trout and Yellowstone or rainbow trout (or both) in 32 of 80 samples (40%) considered to be

pure westslope trout. A genetic analysis of samples from the Flathead River drainage in

Montana showed that only 2 of 19 headwater lakes harbored populations of pure westslope

cutthroat trout and that gene flow was occurring between introgressed and downstream

populations (Marnell et al. 1987). Extensive hybridization has also been documented between

Yellowstone cutthroat trout and rainbow trout (Allendorf et al. 1987, Martin et al. 1985),

between Paiute and coastal cutthroat trout (Busack and Gall 1981), and between coastal cutthroat

trout (2n = 68, Gold 1977) and steelhead (Campton and Utter 1985). Although chromosome

numbers may differ between these taxa, the total number of arms (104-106) is similar among

taxa, and Robertsonian (chromosome arm fusion) polymorphisms are common within these trout

species (e.g., Thorgaard 1983). Similarity in chromosomal arm number and substantial gene

duplication in salmonids permits these taxa to hybridize without major developmental

incompatibilities (Ferguson et al. 1985, 1988).

Hybridization between coastal cutthroat trout and O. mykiss has been detected with

molecular methods in many West Coast drainages (Table 6). Neillands (1990) surveyed genetic

variability in nine tributaries to Prairie Creek and in five tributaries to Redwood Creek (both in

Northern California), and in a sample from the Redwood Creek embayment. The Campton and

Utter (1985) hybrid index (relative probability that the multilocus genotype of a particular fish

could have arisen by random mating within two species) was used to identify pure and hybrid

individuals from allozyme genotypes, and gametic disequilibrium (nonrandom association of

alleles between loci) was used to measure the consequences of hybridization. Four loci

(IDDH-2*, IDHP-3,4*, MEP-4*, and PEP-A*) appeared to distinguish between coastal cutthroat

trout and O. mykiss. The hybrid index indicated that 8 of the 15 samples had hybrid index values

that indicated the presence of hybrid individuals. Departures from Hardy-Weinberg genotypic

proportions in some samples indicated they were composed of individuals from more than one

population. Estimates of gametic disequilibrium were significantly greater than zero in the

coastal cutthroat trout components in four streams and for the hybrid component in one stream.

None of the O. mykiss subsamples showed evidence of gametic disequilibrium. These results

indicate that hybridization in the Redwood Creek drainage is extensive and that introgression
77
78
79
80

between coastal cutthroat trout and steelhead in some streams has been occurring over several

generations, which is long enough for the decay of gametic phase disequilibrium by

chromosomal recombination.

An analysis of paired interspersed nucleotide elements (PINEs) of genomic DNA was

used to identify coastal cutthroat trout, O. mykiss, and hybrids between these taxa in 29 samples

from the Clackamas, Sandy, and Hood rivers and from streams entering the Lower Columbia

River (P. Spruell13 ). Seven samples contained individuals of only O. mykiss, while 11 samples

contained only coastal cutthroat trout. Seven samples contained a substantial proportion of

hybrid fish in addition to apparently pure coastal cutthroat trout and O. mykiss. Some streams

appear to harbor hybrid swarms between the two taxa. These results showed a mosaic

distribution of coastal cutthroat trout, O. mykiss, and hybrids among streams.

In a survey of genetic variability in coastal cutthroat trout, Campton and Utter (1985)

found hybrids between cutthroat trout and O. mykiss in 2 of 23 streams. To estimate the extent

of hybridation in these two streams and to understand the nature of hybridization, they sampled

Big Mission Creek in Hood Canal at three sites, 0.8, 5.4, and 8.8 km from the mouth, and Harvey

Creek, a tributary to the Stillaguamish River, at 1.9, 2.4, 2.9, and 3.2 km from the mouth. They

found that the geographic pattern of the occurrence of hybrids differed between these streams. In

addition to these occurrences of hybridization in natural populations, they found a large

proportion of hybrids in the Beaver Creek Hatchery coastal cutthroat trout brood stock. Given

the distributions of genotypes among individuals, it appeared that many of the hybrid fish

represented backcrosses and matings between first-generation (F1) hybrid individuals. However,

few fish with coastal cutthroat trout × O. mykiss features or hybrid genotypes have been observed

as adults. Although hybridization occurs extensively, as evidenced by the many underyearling

(0+) hybrids, natural selection among older fish may greatly reduce the numbers of hybrids

reaching maturity.

Hawkins (1997) used allozyme and mtDNA variability to identify hybrids in samples

collected in 1992-94 from Big Beef and Big Mission creeks in Hood Canal and from Harvey

Creek in the Stillaguamish River. The number of steelhead and coastal cutthroat trout mtDNA

haplotypes among 23 individuals identified as hybrids with allozyme markers was similar; 12

had cutthroat mtDNA haplotypes and 11 had steelhead. Nine of the 12 hybrids with cutthroat

haplotypes were identified as backcrosses or introgressed individuals with allozymes. Five of

the 11 hybrids with steelhead haplotypes were backcrosses or introgressed individuals.

Hawkins (1997) also studied several behavioral, morphological, and performance traits in

artificially produced hybrids between hatchery strains of coastal cutthroat trout and steelhead. In

one study, Hawkins measured egg size and time of emergence in pure strains of coastal cutthroat

trout and steelhead from the Aberdeen (Washington) Hatchery and Eels Springs Hatchery,

Shelton, Washington, and in hybrid individuals. These results indicated that decreased

fertilization success or decreased embryonic viability did not appear to act as a post zygotic

isolating mechanism between these coastal cutthroat trout and steelhead. Most of the differences

13 P. Spruell, University of Montana, Div. Biol. Sciences, Missoula, MT 59812-1002. Pers. commun. to

S. Grant. Sept. 1998.
81

between coastal cutthroat trout and steelhead early development were correlated with larger egg

size in steelhead. Hybrid individuals were intermediate between the pure strains for mortality

from fertilization to hatching, time to hatching, body weight at hatching, body weight at

emergence, growth 40-52 days post fertilization, and time to 50% change in yolk mass.

In a study of hybrids between hatchery strains of coastal cutthroat trout and steelhead,

Hawkins and Quinn (1996) made reciprocal cutthroat-steelhead crosses and measured critical

swimming speed in pure and hybrid individuals. Since migration is a pervasive and important

feature of salmonid life histories, selective disadvantages in hybrid individuals may be apparent

as swimming impairment. They found that hybrid fish had critical swimming speeds that were

intermediate to speeds in pure hatchery strains, and that no paternal or maternal effects were

apparent in hybrid performance. They also found that hybrid body shape was intermediate

between coastal cutthroat trout and steelhead. These results are consistent with inherited

differences in life-history patterns between coastal cutthroat trout and steelhead.

Several of these parameters may have fitness consequences in natural populations. In

pure strains of coastal cutthroat trout and steelhead, the rate of development is presumably

matched to larval body size and yolk size so that alevins emerge from the gravel when the stage

of development is most conducive to survival. Hybrids, however, appear to develop too slowly

from small eggs or too quickly from large eggs, depending on maternity, so they emerge with too

little or too much yolk. The mismatch between egg characteristics and emergence time may

limit the success of hybrids in natural populations and may therefore limit introgression.

Swimming speed may also influence fitness. Steelhead tend to inhabit faster-moving water than

do coastal cutthroat trout, and steelhead make longer marine migrations than do coastal cutthroat

trout.

In summary, the results of these studies lead to these conclusions:

1. Hybridization between coastal cutthroat trout and steelhead is widespread throughout

the range of coastal cutthroat populations on the West Coast.

2. Hybrid individuals have been detected most often among age 0+ and 1+ fish, but

seldom among adults. However, the presence of introgressed individuals implies that

hybrids can grow to maturity and reproduce.

3. Repeated sampling after about five generations in the same stream indicates that

hybridization is ongoing in some areas (Big Mission Creek in the Hood Canal and

Harvey Creek in the Stillaguamish River) and is not a sporadic event.

4. No developmental abnormalities (except for too much or too little yolk) appear to

occur in hybrids. However, morphological and behavioral characteristics of hybrids

may be disadvantageous in the natural environment, and may tend to limit the success

of hybrids in the wild.
82

Studies of Regional Patterns of Genetic Variability

Only a limited number of studies of the genetic population structure of coastal cutthroat

trout populations in the Pacific Northwest have been published in the last few years. Other

studies are in graduate theses that have not yet been published. All but one of these studies

included samples from a limited geographic range. NMFS, WDFW, and ODFW recently

initiated a coastwide study of biochemical genetic variability in coastal cutthroat trout to help

delineate groups of populations for management and conservation. Samples collected for this

study were analyzed in the laboratory by NMFS and WDFW, and these data have been combined

and summarized in this review. The NMFS/WDFW/ODFW study is discussed in “New Genetic

Data” (p. 85); summaries of previous studies follow.

In the earliest genetic study of coastal cutthroat trout, Campton and Utter (1987) surveyed

genetic variability with protein electrophoretic methods in populations of coastal cutthroat trout

in 21 streams in Hood Canal and North Puget Sound. Analysis of allele frequencies at 31 loci in

these samples revealed considerable within- and between-population genetic diversity. Twentyone loci (68%) were polymorphic in at least one population, and sample heterozygosities

(H, averaged over loci) ranged from 0.080 to 0.129 and averaged 0.097 among samples. A gene

diversity analysis of allele frequencies reflected the results of the analysis of variance (ANOVA);

diversities for year classes, streams, drainages, and regions were 1.17, 2.41, 1.01, and 1.24%,

respectively. Seven of the 12 loci analyzed in the ANOVA were significant for stream effects,

two for drainage effects, and seven for regional effects. A principal coordinate analysis (Everitt

1978) in two dimensions resolved at least two groups: 1) a north Puget Sound group including

the Skagit and Stillaguamish rivers, and 2) a Hood Canal group. These results indicate that not

only does significant regional differentiation between Puget Sound and Hood Canal exist on a

scale of about 300 km, but also that significant small-scale differences exist between streams on

a scale of a few kilometers.

On a geographic scale of about 20 km, Zimmerman (1995) measured genetic and

morphological variability in six unreplicated samples of coastal cutthroat trout in Muck Creek of

the lower Nisqually River, Washington. Fourteen of the 52 allozyme encoding loci examined

with electrophoresis for Mendelian variability were polymorphic with a common allele

frequency of p < 0.95. Average sample heterozygosities ranged from 0.042 to 0.057 and

averaged 0.051 over samples. No geographic pattern appeared in the distribution of H among

samples. Pairwise tests for allele-frequency differences and UPGMA cluster analyses of Nei’s

(1972) genetic distance indicated that the largest divergence was between the Chambers Lake

sample and the remaining samples. These results show that significant, but weak, allelefrequency differences can arise between populations separated by only a few kilometers in the

same drainage.

The analysis of microsatellite loci also indicated that allele-frequency shifts can occur

over short distances. Wenburg et al. (1998) examined geographic variability at six highly

polymorphic microsatellite loci in samples from 13 presumed sea-run populations of cutthroat

trout in Washington State and in an outgroup sample of Yellowstone cutthroat trout. The

sampled populations extended from southwestern Washington through the Strait of Juan de Fuca
83

to Hood Canal and southern Puget Sound and were a subset of samples examined with protein

electrophoresis by the WDFW (1998a). Individuals that appeared to be hybrids between coastal

cutthroat trout and O. mykiss were identified by diagnostic alleles at two microsatellite loci and

excluded from the statistical analyses. After removal of hybrid individuals, sample sizes for the

microsatellite analysis averaged 38 fish each and therefore provided moderately precise estimates

of allele frequencies.

High levels of microsatellite variability were detected. Mean sample heterozygosity

averaged 0.67 with an average of 24 alleles per locus. Excluding the Yellowstone cutthroat trout

outgroup sample, a gene diversity analysis of variance components indicated that 87.9% of the

total gene diversity was due to within-sample variability, 5.4% was due to allele-frequency

differences between streams within the six regions, and 6.7% was due to differences between the

six regions in Washington State. Estimates of gene flow (private-allele method, Slatkin 1985)

between streams within six regions averaged 1.7 fish per generation. The estimate of the number

of effective migrants between all streams sampled was 3.2 fish per generation. This latter value

may underestimate gene flow between neighboring streams if the pattern of exchange between

streams follows the stepping-stone (rather than the island) model of migration.

In the Wenburg et al. (1998) study, Mantel’s tests for association between geographic

distance and pairwise FST and RST (an analogue of FST developed for microsatellite data)

estimates of divergence were not significant, indicating an apparent lack of isolation by distance

on the geographic scale of the study. However, geographically nearby samples tended to cluster

together in a neighbor-joining tree of Cavalli-Sforza and Edwards (1967) distance; an exception

was Covington Creek (southern Puget Sound), which clustered most closely with Salt Creek

(Strait of Juan de Fuca). The neighbor-joining tree depicted an outer coastal group of samples

and a group consisting of samples from Strait of Juan de Fuca, Hood Canal, and northern and

southern Puget Sound. These results together indicate that migration between streams is

sufficiently restricted on different geographic scales so that genetic differences can arise between

streams as well as between regions.

On a small geographic scale, Wenburg (1998) examined variability at 10 microsatellite

loci in 10 samples collected in Hood Canal, Washington that were separated by 2-100 km of

shoreline distance. One sample was collected from a population located above a barrier falls.

O. mykiss alleles appeared in seven of the 10 samples (24 of 472 fish). After removing putative

hybrid individuals, he found large sample heterozygosities that ranged from 0.66 to 0.73 and

averaged 0.69. Tests for genotype-frequency differences between two age-class samples

collected from Stavis Creek were not significant for five of six microsatellite loci, indicating that

(at least for this stream) annual variability was small compared to variability between streams.

Wenburg (1998) also estimated gene flow between streams along the eastern shore of

Hood Canal in two ways. First, tag and recapture experiments provided an estimate of gene flow

by recording the physical movements of fish between streams. Corrections were made for

incomplete tagging, tag loss, and sampling efficiency. Expansions of direct counts of migrants

between Big Beef Creek and three adjacent streams (Stavis, Little Anderson, and Seabeck

creeks) ranged from 0 to 32.1 fish per generation. The physical presence of a fish in a stream is a
84

necessary but not sufficient condition for estimating gene flow, and may substantially

overestimate actual levels of gene flow. Second, indirect genetic estimates of gene flow were

made by the private-allele method (Slatkin 1985) and by observed estimates of genetic

differentiation between populations and the island model of migration. These indirect estimates

of gene flow between Big Beef Creek and each of the three adjacent streams averaged 11.8

(range 3.8-22.1) fish per generation and were similar to direct estimates of straying from tag and

recapture experiments. On a larger geographic scale, including nine streams in Hood Canal,

indirect estimates of gene flow ranged from 6.0 (private alleles model) to 8.4 (FST and island

model) fish per generation. These latter estimates were larger than previously estimated by

Wenburg et al. (1998) between streams scattered over a similar geogaphic scale.

WDFW (1998a) presented the results of an allozyme analysis of 47 samples collected

from seven broadly defined regions in Washington: 1) northern Puget Sound, 2) southern Puget

Sound, 3) Hood Canal, 4) Strait of Juan de Fuca, 5) Olympic Peninsula, 6) southwestern

Washington coast, and 7) Lower Columbia River. Most streams were sampled only once. A

subset of samples from each of these regions was analyzed by Wenburg (1998) for microsatellite

variability. After the removal of hybrids, WDFW (1998a) analyzed the samples in two ways.

First, a contingency-table analysis (G-test) of allele frequencies was used to search for

reproductive isolation between populations, but without Bonferroni corrections for multiple tests

of the same hypothesis with different polymorphic loci. These results, therefore, probably

overestimate the amount of reproductive isolation between populations and between population

groups, due to Type I error (chance significance). Generally, contingency table tests of allele

frequencies showed highly significant (p < 0.001) differences at all 33 polymorphic loci tested

between samples within drainages except samples in Harvey Creek (Stillaguamish River)

collected 1.2 km from each other. Highly significant differences were also found between

samples from each of the seven regions, apparently indicating a high degree of reproductive

isolation between regions.

The second approach used to search for distinct population groups was to construct

UPGMA dendrograms from Cavalli-Sforza and Edward’s (1967) genetic distances, Dc, between

samples. Although dendrogram analysis is not a formal test of stock structure, such an analysis

may be useful for depicting genetic relationships among stocks and for summarizing levels of

genetic diversity among stocks. The dendrogram indicated the presence of two large groupings

of coastal cutthroat trout populations, which was consistent with the results of Wenburg et al.

(1998) for microsatellite variability. In addition to the two large groups, four samples, each from

different regions, were outliers that fell outside the two major groups. One major group

consisted of populations in Puget Sound, Hood Canal, and the Strait of Juan de Fuca. Within this

group, the samples from northern Puget Sound formed one cluster and samples from southern

Puget Sound, Hood Canal, and the Strait of Juan de Fuca formed another. Some samples from

southern Puget Sound clustered most closely with samples from Hood Canal and the Strait of

Juan de Fuca. A second major group consisted of populations from coastal Washington and the

Lower Columbia River. In this group, samples from the Olympic Peninsula were distinct from

samples from southwestern Washington and the Lower Columbia River.
85

Williams et al. (1997a, b) examined allele frequency variability and meristic characters in

populations ranging from Northern California to Prince William Sound, Alaska. In an analysis

of allelic frequencies for 43 populations, they found that coastal cutthroat trout were

characterized by higher levels of genetic heterogeneity among local populations than were

populations of Pacific salmon and other trout. Williams et al. (1997b) reported a GST value of

0.19 for the 43 populations surveyed and found that estimates of genetic distances (Nei 1978)

between populations ranged from 0.01 to 0.063. Sample heterozygosities averaged 0.102 (range

0.071 - 0.157) (T. Williams11 ). In addition, Williams et al. (1997a, b) reported consistent genetic

differences among populations in Alaska, Washington, Oregon, and California, but apparently

less geographical structure within regions than has been observed among populations of other

Pacific salmon and trout. A preliminary cluster analysis of Nei’s (1978) genetic distances

between populations in British Columbia indicated that southern mainland populations were

genetically similar to coastal cutthroat populations in northern Puget Sound. Populations on

Vancouver Island clustered separately from populations in Washington and mainland British

Columbia (Williams footnote 14).

New Genetic Data

In our assessment of the degree of reproductive isolation between populations or groups

of populations of coastal cutthroat trout, NMFS and WDFW jointly analyzed tissue samples

collected from 97 localities in British Columbia (n = 1), Washington (n = 45), Oregon (n = 45),

and California (n = 6) (Table 7, Fig. 16). We also included in some analyses comparable data for

westslope cutthroat trout collected from hatchery broodstock (Anaconda, Montana), and

steelhead trout from the Yaquina River, Oregon. A complete set of data is available for these

50 loci:

mAAT-1* sAAT-1* sAAT-3* ADA-1* ADA-2* ADH*

mAH-1* mAH-3* sAH* CKA-1* CKB* FH*

bGLUA* bGALA* GDA-2* GPIA* GPIB-2* G3PDH-1*

GR* IDDH-1* mIDHP-1* mIDHP-2* sIDHP-1* sIDHP-2*

LDHA-1* LDHA-2* LDHB-1* LDHB-2* LDHC* sMDHA-1*

sMDHB-1* sMEP-1* sMEP-2* mMEP-1* MPI* NTP*

PEPA* PEPB-1* PEPD-1* PEPLT* PGDH* PGK-1*

PGK-2* PGM-1* PGM-2* sSOD-1* TPI-1* TPI-2*

TPI-3* TPI-4*

Only the Alsea River (Oregon) was sampled in more than one year (1995 and 1997), but these

samples were not combined for the analyses. Several factors, including the presence of hybrid

individuals, uneven geographic sampling, and genetic outliers, dictated an extensive genetic

14 T. Williams, NMFS, SWFSC, PO Box 271, La Jolla, CA 92038. Pers. commun. to S. Grant. Oct.

1998.
86
87
88
89
90

analysis. In our analysis, we used multidimensional scaling, in two and three dimensions, of

Nei’s (1978) unbiased and Cavalli-Sforza and Edward’s (1967) chord genetic distances between

samples to search for genetically discrete population groups.

Sampling of hybrids

Species identifications of small fish in the field were difficult because some of the

characters distinguishing coastal cutthroat trout from O. mykiss in larger individuals are

undeveloped in smaller individuals. We therefore used variability at three loci (ADA-2*,

mAH-2*, CKA-2), which were fixed or nearly fixed for different alleles in coastal cutthroat trout

and O. mykiss, to identify O. mykiss individuals that had been inadvertently included in the

samples. These individuals were excluded from all of the remaining analyses. A threedimensional scaling of Nei’s (1978) genetic distances between samples, with O. mykiss

individuals removed, showed that most of the samples of coastal cutthroat trout were tightly

clustered together and were genetically well differentiated from westslope cutthroat trout and

steelhead (Fig. 17). Nei’s (1978) genetic distances between the sample of Yaquina River

steelhead and coastal cutthroat trout samples ranged from 0.091 to 0.184, except for the

Aberdeen Fish Hatchery (Dn = 0.062), Multnomah Creek (Oregon) (Dn = 0.022), and Pass Creek

(Oregon) (Dn = 0.056). These latter three samples contained a high proportion of coastal

cutthroat trout × O. mykiss hybrids that apparently produced the smaller genetic distances with

the Yaquina River steelhead sample. Genetic distances between the westslope cutthroat trout

sample and coastal cutthroat trout samples ranged from 0.113 to 0.200. The genetic distance

between the westslope cutthroat trout sample and the steelhead sample was 0.141. These Nei’s

genetic distances between coastal cutthroat trout, westslope cutthroat trout, and steelhead are

slightly greater than those reported by Allendorf and Leary (1988) for similar subspecies, and

this difference may be due to differences in the set of loci in the two studies that were used to

estimate Dn. The present results confirm previous results of allozyme studies in depicting as

much genetic divergence between coastal cutthroat trout and westslope cutthroat trout as between

coastal cutthroat trout and O. mykiss.

Comparisons of genotypes between coastal cutthroat trout and O. mykiss indicated that

several samples collected to represent cutthroat trout populations contained hybrid individuals.

Figure 18 shows an enlarged view of a two-dimensional scaling of Nei’s (1978) distances

between 99 samples, including westslope cutthroat and steelhead. Several samples lay outside

the enlarged portion of the graph. Some regional clustering is apparent in this two-dimensional

scaling: samples from Puget Sound, Hood Canal, and the Strait of Juan de Fuca tended to occupy

the upper portion of the graph; samples from coastal Oregon and California occupied the lower

portion of the graph; and samples from southwestern Washington and the Lower Columbia and

Willamette rivers clustered between samples from Washington and those from Oregon and

California.
91
92
93

We attempted to remove hybrid individuals from the genetic data base because the

objective of this analysis was to infer the genetic population structure of coastal cutthroat trout

from allozyme data. The presence of hybrids would most likely introduce error in estimating

levels of genetic divergence between coastal cutthroat trout populations. We used eight loci

(sAAT-4*, ADA-2*, mAH-2*, mAH-3, CKA-2*, IDDH-1*, sIDH-2*, and sMEP-2*) that showed

strong frequency differences between coastal cutthroat trout and O. mykiss in an attempt to

identify hybrid individuals. Some alleles might be shared between coastal cutthroat trout and O.

mykiss because of common phylogenetic ancestry, while other alleles might be shared because of

recent hybridization. Therefore, to minimize the chances of excluding individuals of coastal

cutthroat trout naturally carrying O. mykiss alleles, we used a 50% rule in which individuals with

at least one steelhead allele at four of these eight loci were considered to be hybrids. The

50% rule almost certainly allowed some introgressed individuals into the coastal cutthroat

samples and alternatively excluded true coastal cutthroat trout. With this rule, 28 of 97 (29%) of

our samples contained hybrids (Fig. 19). The percentage of estimated hybrid individuals in

28 samples containing hybrids ranged from about 1% to 84% (Multnomah Creek). The samples

from Pass Creek (82%) and the Aberdeen Creek Hatchery (48%) also contained a high

proportion of hybrids. Most of the hybrid individuals appeared to represent introgression from

the second generation or later, since only a single individual was found in this study with

heterozygous genotypes at all diagnostic loci. We removed hybrid individuals from the database

and recalculated allelic frequencies to estimate genetic distances between samples. We also

removed the sample from Multnomah Creek because it consisted chiefly of hybrid individuals

and represented a population isolated above impassable falls.

These results permit two tentative conclusions. First, samples with hybrid individuals

were distributed over most of the sampling area and did not appear to be associated with any

particular area or kind of habitat, although no attempt was made to quantitatively assess the

habitats from which samples were collected. Second, the proportions of hybrids in these samples

probably represent minimal estimates of the extent of hybridization between coastal cutthroat

trout and O. mykiss, since the samples were collected to represent coastal cutthroat trout and not

to assess the extent of hybridization (i.e., sampling attempted to avoid steelhead and hybrids).

Additional sampling, without regard to identifying hybrids in the field, is required to assess the

full extent of hybridization between coastal cutthroat trout and O. mykiss.

A two-dimensional scaling of chord distances between samples of only coastal cutthroat

trout with hybrids removed appears in Fig. 20. The chord distance is based on a model that

assumes only random drift as the cause of population divergence and may be more appropriate

than distances, such as Nei’s genetic distance, which are based on models that also incorporate

mutation. The same general clusters appeared as in Figure 18, but with greater separation

between clusters. British Columbia, Puget Sound, Hood Canal, and Strait of Juan de Fuca

samples appeared in one cluster; southwestern Washington, Lower Columbia River, and

Willamette River samples appeared in another cluster; and coastal Oregon and California

samples appeared in a third cluster. However, some samples were unusual. One group of these

unusual samples included extreme outliers unlike the other samples and included Nos. 9, 30, 35,
94
95
96

50, 55, 56, 68, and 91. Another group included several samples that were genetically similar to

samples from other geographic areas.

Uneven geographical sampling

One caution in inferring genetic relationships among samples is that the outcome of an

analysis may be influenced by uneven geographical sampling. Four river drainages were

sampled much more than others in this data set. Seven samples were collected in the Skagit

River, six were collected in the Stillaguamish River, eight were collected in the Umpqua River,

and nine were collected in the Coquille River. An enlarged view of the two-dimensional scaling

shown in Figure 20 appears in Figure 21. This enlargement shows that most of the samples from

the Skagit and Stillaguamish rivers clustered more tightly than did multiple samples from other

rivers. However, the overrepresentations of samples from these rivers could possibly distort the

positions of the other samples from drainages with fewer samples.

Ideally, a jacknife or bootstrap analysis of multidimensional scaling results might have

assessed this problem quantitatively but was not feasible within the constraints of this study. To

aid in understanding the effects of uneven sampling on clustering topology, we reanalyzed two

smaller sets of samples that excluded all but two samples from each of these four river drainages.

Two samples with the largest sample sizes were selected from each of these four drainages for

one set of samples, and two different samples from each drainage, also with large sample sizes,

were selected for a second set of samples. Enlarged views of two-dimensional scalings of these

two reduced data sets appear in Figures 22 and 23. Both of these analyses depicted the same

three major clusters that appeared in a two-dimensional scaling of the complete set of samples.

A comparison of the positions of samples common to the two-dimensional scalings shown in

Figures 21, 22, and 23 indicates only slight variations in the positions of these samples relative to

one another. We conclude that the uneven representation of some river drainages in the coastal

cutthroat genetic data set did not obscure genetic patterns among samples in our analyses or

create spurious relationships. The following analysis of genetic population structure, therefore,

included all of the samples in these four drainages.

Genetic outliers

After removal of hybrid individuals, a two-dimensional scaling of chord distances

between the remaining samples revealed three large clusters of samples. Fifteen samples

(Nos. 9, 24, 33, 35, 48, 50, 55, 56, 57, 66, 68, 74, 80, 87, and 91) were not close to their

geographically nearest neighbors (Fig. 20). Several factors may have produced these genetic

outliers. First, three of these samples (Nos. 56, 68, and 80) consisted of only 10-12 individuals,

and sample error may have produced larger-than-expected genetic distances between these

samples and the remaining ones. These samples were still strong outliers when Nei’s unbiased

genetic distance was used (Fig. 18), so sample size per se may not be the reason for apparent

genetic uniqueness. The remaining 12 genetic outliers, however, consisted of sample sizes
97
98
99
100

ranging from 26 to 111 individuals (median = 50) and were similar in size to the remaining samples.

Genetic outliers may also have arisen because the samples included the progeny of only a few

individuals from a larger population. The presence of linkage disequilibrium between loci might

provide evidence of offspring from the same parents in a sample, but the constraints of this study

did not permit this analysis.

Random genetic drift in isolated populations and founder effects can lead to populations

with unusual genetic makeups. Allele frequencies can shift substantially from those of nearby

populations if some populations have been initiated with only a few founders. Large genetic

divergences can also arise as a consequence of isolation by natural barriers to migration such as

waterfalls and landslides, by manmade barriers such as impassable culverts and dams, or by the

fragmentation or loss of sea-run migrants that would otherwise facilitate gene flow between

populations. Theory indicates that average heterozygosity (H) of selectively neutral genes is lost

at a rate of 1/2Ne each generation (Crow and Kimura 1970), where Ne is the effective population

size (the size of a hypothetical population with equal sexes in which gene diversity is lost at the

same rate as it is in the population in question). The loss of heterozygosity over time is greater

for small populations than it is for large populations (Fig. 24). For example, an isolated

population consisting of an effective population size of 40 will lose 40% of its gene diversity

(H) in about 40 generations. In the coastal cutthroat trout data set, several genetic outliers had

heterozygosities that were smaller than the mean heterozygosities of samples collected in the

same drainage or area (Fig. 25). Reduced heterozygosity values are consistent with greater

physical isolation in some populations. Heterozygosity values for sample Nos. 33 (Strait of Juan

de Fuca), 35 (Olympic Peninsula), 50 (Willamette River), 66 (Umpqua River), and 80 (Coquille

River) were less than the range of heterozygosities in nearby samples. These results are

consistent with greater physical isolation in these samples.

Random drift also accelerates genetic divergence from neighboring or from parental

populations following colonization (Fig. 26). Divergence from drift is most important in small

populations. In populations with effective sizes of 80 or fewer fish, FST (a measure of genetic

differentiation) increases rapidly in only a few generations. For example, FST is expected to

increase to about 0.20 in 20 generations, which represents about 60 years for cutthroat trout. At

smaller population sizes, divergence from neighboring populations increases even more rapidly.

Divergence between coastal cutthroat populations in a river drainage averaged about 0.074 in the

present study, with extreme values between genetic outliers and neighboring populations

reaching 0.20 or more. These extreme levels of divergence could appear in just a few

generations in completely isolated populations, with the small effective population sizes

expected in coastal cutthroat trout. Strong allele-frequency shifts observed in a sample from

Cripple Creek (No. 50, Clackamas River), for example, would be consistent with complete

isolation for tens of generations.

Another reason for genetic outliers may be allele frequency shifts because of

introgression by migrants or outplanted fish from genetically differentiated populations. One

piece of evidence that outplants can genetically influence local populations is the genetic

similarity between Alsea Hatchery coastal cutthroat trout and populations in streams in the
101
102
103
104

Coquille River that received Alsea Hatchery fish (P. Reimers15 ). In these cases, however, the

outplantings acted like gene flow to make local populations more similar to one another and to

Alsea Hatchery fish than they would otherwise be with natural levels of straying between

populations. Hybridization with O. mykiss may also distort allelic frequencies in a sample. Even

though putatively hybrid individuals were removed before allele frequencies were calculated in

this analysis, O. mykiss alleles may still be present in these samples.

Lastly, genetic outliers may represent undersampled groups of genetically distinct

populations. For example, the three samples (Nos. 19, 20, and 21) from the upper Nisqually

River were very different from a sample in the lower reaches of the river (No. 18) similar to other

southern Puget Sound populations. If only one sample had been collected from the upper

Nisqually River, it would have been considered a genetic outlier. However, the genetic

similarity between these three samples indicates that populations in the upper Nisqually River as

a whole are genetically divergent from other Puget Sound populations.

Regional patterns of genetic variability

To facilitate resolving the genetic population structure, we excluded nine populations

from the data set that were extreme graphical outliers (Nos. 9, 33, 35, 50, 55, 56, 57, 68, and 91

[Fig. 20]). These populations were omitted from the graphs that follow because it was not

possible to enlarge the view of three-dimensional scalings of genetic distances with NTSYS-pc.

Omitting these nine outlying samples from the analysis does not exclude the possibility of

additional genetic (as opposed to graphical) outliers in the remaining sample space. A threedimensional scaling of genetic distances might reveal genetic population structure in a third

dimension.

The upper view of a three-dimensional scaling of the chord distance appears in Figure 27

and is similar to the two-dimensional scaling of populations in Figure 21, which depicted three

major groups of populations. A side view of this three-dimensional scaling appears in Figure 28.

A cluster in the right-hand portion of these graphs consists of samples from British Columbia,

Puget Sound, Hood Canal, and the Strait of Juan de Fuca (Nos. 1-33, except genetic outliers

Nos. 9, 24, and 33). The samples from drainages in southern Puget Sound (Nos. 16-24), Hood

Canal (Nos. 25-28), and the Strait of Juan de Fuca (Nos. 29-33) formed a more diffuse cluster

than did samples from northern Puget Sound drainages. The samples from the Strait of Juan de

Fuca, however, are not close to their closest geographical neighbors in northern Puget Sound or

on the Olympic Peninsula. In the third dimension, the three upper Nisqually River populations

(Nos. 19, 20, and 21) were genetically more divergent from other Puget Sound populations than

was apparent in the two-dimensional scaling.

Samples from the northern Washington coast on the Olympic Peninsula (Nos. 34-39)

formed a widely scattered group, but were nonetheless closely connected in the minimum

15 P. Reimers, ODFW, 4475 Boat Basin Drive, PO Box 5430, Charleston, OR 97420. Pers. commun. to

S. Grant. March 1997.
105
106
107

spanning network. This group was genetically intermediate between southwestern Washington

samples and samples from northern Puget Sound, but was, as noted previously, distinct from the

geographically neighboring Strait of Juan de Fuca samples. This geographic group contained

one genetically very dissimilar sample, Bear Creek (No. 35, Sol Duc River).

A second major cluster in Figure 27 included samples from the southwestern Washington

coast, the Lower Columbia River, and the Willamette River (Nos. 40-58). The minimum

spanning network indicated that southwestern Washington and Lower Columbia River samples

(Nos. 40-48) were more closely related to one another than to other samples. No consistent

separation appeared between samples from natural populations in southwestern Washington

(Nos. 40, 42, and 43) and populations in the Lower Columbia River (Nos. 46, 47, and 48).

Samples from the Beaver Creek and Cowlitz River hatcheries were genetically very similar to

each other, and this similarity may reflect exchanges between these hatcheries. Although the

samples from the Willamette River drainage (Nos. 50-58) were related to those from

southwestern Washington and the Lower Columbia River, the minimum spanning network

indicated they were generally more closely related to one another than to other samples in this

cluster. Even so, the samples from Cripple Creek (No. 50, Clackamas River), and from the

southern portion of the Willamette River were extreme outliers (Nos. 55-57).

The third major cluster on the left side of the three-dimensional scaling depicted in

Figures 27 and 28 included samples from coastal Oregon and California drainages (Nos. 59-97).

Little genetic differentiation appeared between samples from different river drainages or between

geographic areas. One feature of this cluster in three-dimensional scaling is that the level of

genetic divergence between populations within the Umpqua, Coquille, and Klamath rivers was

much greater on average than the level of genetic divergence between populations within

drainages in Puget Sound. This trend holds whether or not genetic outliers are included in the

analysis.

The three-dimensional scaling of Nei’s (1978) genetic distances between samples

confirmed these general groupings (Figs. 29 and 30). A two-dimensional view of the threedimensional scaling showed less separation between Puget Sound-Hood Canal-Strait of Juan de

Fuca samples and southwestern Washington-Lower Columbia River samples than was apparent

in the three-dimensional scaling of chord distances. However, these two groups showed a greater

amount of separation in the third dimension. The Strait of Juan de Fuca samples (Nos. 29-32)

were also not genetically similar to their closest geographical neighbors in this three-dimensional

scaling. Populations within the drainages of coastal Oregon and Northern California showed a

greater amount of divergence from one another than was apparent between populations within

rivers draining into Puget Sound. Although the minimum spanning tree indicated that

populations within coastal Oregon and Northern California drainages were generally more

closely related to one another than to populations in other drainages, no clear pattern of

separation appeared between drainages.

A gene diversity analysis of allele-frequency variability (Nei 1973, Chakraborty 1980)

indicated that 18% of the total variability was due to variability among populations, while 82%
108
109
110

was due to genetic differences between individuals within populations, on average. Variability

between populations can be broken down further. About 5.4% was due to differences among the

six major groups, 5.1% was due to differences among rivers within the six major groups, and

7.4% of the total variability was due to differences among populations within rivers, on average.

Only about 0.1% of the total variability was due to differences between sea-run and nonmigratory coastal cutthroat trout within streams. This estimate, however, was based on only

three above- and below-waterfall comparisons and probably underestimates the average level of

genetic differentiation among these life-history types. A population isolated above an

impassable barrier to migration may show considerable divergence from populations below the

barrier. However, this data set provided few paired comparisons for above and below barriers.

Some features of coastal cutthroat trout genetic population structure require explanations.

First, a coastwide pattern of isolation by distance is apparent in the distributions of allelic

frequencies. Samples from each region tended to cluster together and geographically

intermediate samples from southwestern Washington and the Lower Columbia River tended to

appear in an intermediate position in the cluster analysis between northern samples and southern

samples. This pattern appeared in all of the results, including analyses of data sets with hybrids

and with and without graphical outliers. However, a notable exception appeared within this

general pattern of isolation by distance. The Strait of Juan de Fuca populations tended to be

more closely related to Hood Canal and southern Puget Sound populations populations than they

were to northern Puget Sound populations or to Olympic Peninsula populations. These genetic

relationships may reflect recolonization patterns following the retreat of glaciers about 13,000

years ago (Thorson 1980).

Another feature of coastal cutthroat trout genetic population structure was that the

amount of genetic divergence between populations differed between drainages. Samples

collected within the Skagit and Stillaguamish rivers tended to be much more similar to one

another than were samples collected in the Willamette, Umpqua, and Coquille rivers. One

possible explanation is that, since southern drainages have long histories uninterrupted by

glaciation, a greater amount of genetic divergence has accumulated between populations than has

accumulated between populations in drainages that were covered with glaciers. Another possible

explanation is that the sea-run life-history component of coastal cutthroat trout has been lost in

southern river systems and that this loss has increased the degree of isolation, and hence genetic

differentiation, among populations. Additional ecological and life-history information is needed

to determine which of these nonexclusive explanations is most important.

Genetic Information Summary

Coastal cutthroat trout differ from most other West Coast salmonids in that several

different life-history patterns are expressed by different populations or by different individuals in

the same population. Some fish remain in freshwater streams or lakes over their lifetimes, while

others migrate into the lower reaches of rivers or to the ocean at various times in their life cycle.

Although genetic differences that are often substantial can arise between populations consisting
111

of different life-history types, similar life-history types did not cluster together as a groups and

probably do not represent distinct taxa or distinct evolutionary lineages.

Hybridization between coastal cutthroat trout and steelhead appears widespread along the

West Coast. About one-third of the samples collected by NMFS, ODFW, or WDFW in British

Columbia, Washington, Oregon, and California that were thought (and intended) to be coastal

cutthroat trout contained hybrid individuals. Detailed studies of hybridization show that hybrid

swarms can occur in one part of a stream, while steelhead and coastal cutthroat trout coexist in

other parts apparently without interbreeding. Most hybrid individuals detected with molecular

genetic methods are usually 0+ and 1+ age-class fish and are seldom seen as adults. The

occurrence of introgressed populations, however, implies that hybrids can mature and reproduce.

Hybrid individuals tend to be intermediate between steelhead and coastal cutthroat trout in

several morphological and behavioral characteristics and may have lower fitness as a result.

The NMFS et al. unpublished genetic data set consisting of 99 samples contained several

apparent outliers. The origin of these outliers may be due to several factors, including

1) error in estimating allelic frequencies with small sample sizes, 2) random genetic drift in small

isolated population above barriers, 3) introgression from steelhead into coastal cutthroat trout,

4) introgression from the introduction of nonnative strains of cutthroat trout, 5) and incomplete

sampling of genetically divergent groups of populations. Sampling error could account for only

a few of the outliers in this data set. The observation of reduced levels of gene diversity in many

of the outliers (relative to neighboring populations) and genetic heterogeneity over short

distances are consistent with a history of reproductive isolation for some genetically unusual

populations. Allele frequency changes due to hybridization with O. mykiss or to introgression

from nonnative cutthroat trout may also account for large genetic distances between some

genetically unusual populations.

Coastal cutthroat trout differ from other anadromous Pacific salmonids in the genus

Oncorhynchus in the distribution of genetic variation among population and life-history

components (Fig. 31). For example, only a small proportion (2.5-3.5%) of the total variability

among chum and coho salmon populations is due to differences, on average, between

populations within major groups. A smaller proportion (0.3-1.9%) of the total diversity is due to

differences between major groups. Although a similar level of diversity (2.8-2.9%) exists

between populations within major groups in coastal populations of chinook salmon and

steelhead, a larger proportion (10.8-6.4%) of the total diversity is due to differences among the

major population groupings. Coastal cutthroat trout differ from these other salmonids in having

a greater level of among-population variability (18%) over a similar geographic area. The largest

proportion of this variability (7.4%) is found among streams within rivers, with smaller

proportions due to differences among rivers within groups (5.1%), and among major groups

(5.4%). The higher levels of genetic diversity among local populations may be due to greater

amounts of reproductive isolation between populations, to genetic differences between lifehistory types, to higher levels of random drift in small populations, or to combinations of these

factors.
112
113

The genetic groupings of coastal cutthroat trout in our analyses of the coastwide set of

allozyme frequencies is largely consistent with previous studies, which for the most part have

included samples from only limited geographic areas. The three-dimensional scalings of the

chord and Nei’s unbiased genetic distances between samples revealed several geographic

groupings of populations:

1. The northernmost group included samples from southern British Columbia, Puget

Sound, Hood Canal, and the Strait of Juan de Fuca. Some geographic structure among

these samples was also apparent and has been previously observed in other genetic

studies (Campton and Utter 1987, Wenburg et al. 1998).

2. Another group consisted of populations on the Olympic Peninsula that did not cluster

with their nearest neighbors in the Strait of Juan de Fuca. The genetic characteristics

of the Olympic Peninsula populations nonetheless appeared to be transitional between

populations in Puget Sound and those in southwestern Washington.

3. One group consisted of populations associated with large coastal estuaries in

southwestern Washington and the Lower Columbia River.

4. Populations in the Willamette River Basin were allied with populations in

southwestern Washington and the Lower Columbia River, but were distinct from

them.

5. A group consisting of a large number of populations in Oregon coastal drainages

extended from the mouth of the Columbia River presumably to Cape Blanco. Included

in this group were populations from northern Oregon coastal streams and rivers and

the Umpqua and Coquille rivers.

6. Only weak genetic support existed for a separate group consisting of populations

distributed south of Cape Blanco in southern Oregon and Northern California.

Artificial Propagation

NMFS policy (Hard et al. 1992, NMFS 1993) stipulates that determination of 1) whether

a population is distinct for purposes of the ESA and 2) whether an ESA species is threatened or

endangered should focus on “natural” fish, which are defined as the progeny of naturally

spawning fish (Waples 1991a,b). This approach directs attention to fish that spend their entire

life cycle in natural habitat and is consistent with the ESA mandate 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 so that the population seems either less or more distinctive than it was

historically. Artificial propagation can also alter life-history characteristics such as smolt age

and migration and spawn timing (e.g., NRC 1996). Second, artificial propagation poses a
114

number of risks to natural populations that may affect their risk of extinction or endangerment.

(These risks are discussed in “Assessment of Extinction Risk,” p. 135.) Finally, if any natural

populations are listed under the ESA, it will be necessary to determine the ESA status of all

associated hatchery populations. This determination would be made following a proposed listing

and is not considered further in this document. The remainder of this section summarizes the

nature and scope of artificial propagation activities for coastal cutthroat trout and attempts to

identify influences of artificial propagation on natural populations.

Scale of Hatchery Production

West Coast hatchery production of anadromous cutthroat trout is summarized in

Appendix A, which is based on a database developed under contract to NMFS (NRC 1996) and

on state agency reports. Plantings of eggs or fish weighing less than 1.0 gram at release are not

included in Appendix A.

Artificial propagation of coastal cutthroat trout in the Pacific Northwest has generally

attempted to provide fish for recreational harvest, primarily in Puget Sound, Grays Harbor, the

Lower Columbia River, and the Oregon coast (Hooton 1997, Leider 1997). In addition, starting

in the mid-1970s, several programs propagated local stocks of coastal cutthroat trout

(Stillaguamish River, Hood Canal tributaries, and North Fork Nehalem River, to name a few) to

supplement natural spawning populations (Hooton 1997, Leider 1997, Mercer and Johnston

1979). These programs were generally considered unsuccessful and were discontinued by 1993.

The ratio of hatchery to naturally produced coastal cutthroat trout on the West Coast

varies from region to region and from watershed to watershed within a particular ESU, with

coastal cutthroat trout populations dominated by hatchery production in some areas and

maintained by natural production in others (WDFW 1998a, Kostow 1995). Even small (but

persistent) contributions from hatchery fish can affect the genetic makeup of local populations

(Hard et al. 1992). In most cases, however, hatchery programs for coastal cutthroat trout have

been small and of short duration compared to programs for other anadromous salmonids (Hooton

1997, Leider 1997) and have not produced substantial numbers of coastal cutthroat trout relative

to natural production.

Introduction of Nonnative Coastal Cutthroat Trout into Hatcheries

In addition to the outplanting of locally derived stocks, coastal cutthroat trout have often

been transferred within or between watersheds, regions, and states to either initiate or maintain

existing hatchery populations. Eggs, fry, parr, and smolts from nonnative populations have also

been introduced into streams to enhance recreational fishing opportunities.

It is often difficult to determine the proportion of native and nonnative hatchery fish

released into a given watershed. The number and percentage of nonnative fish in a stream are
115

often underestimated for three reasons. First, hatchery or outplanted fish designated as “origin

unknown” in Appendix A (NRC 1996) were counted as native fish, even though their origin may

have been unknown because they were not native. Second, transplanted hatchery fish routinely

acquire the name of the river system into which they have been transferred. For example, coastal

cutthroat trout released from the Tokul Creek Hatchery in the Snohomish River Basin in

Washington are primarily descendants of stock that originated from Lake Whatcom near

Bellingham, Washington (Crawford 1979), but were designated as Tokul Creek stock when

released or transferred there (NRC 1996). Third, this report’s release summary (Appendix A)

does not include releases of coastal cutthroat trout fry smaller than 1 gram and of juveniles from

egg-box programs, in part because of the presumed lower survival of smaller fish. However,

unsmolted fish have been released for decades in many river basins (such as the Chehalis River

Basin), sometimes in relatively large numbers, and some of these programs continue today; these

fish may make some contribution to adult abundance. The validity of this premise, however, has

not been evaluated.

Until recently, the transfer of hatchery stocks of coastal cutthroat trout between distant

watersheds and facilities was a common management practice in Oregon and Washington

watersheds (Appendix A) (Crawford 1979, WDFW 1998a, Kostow 1995). Growing concern

about the genetic and ecological consequences of this practice prompted management agencies to

institute policies to reduce the exchange of coastal cutthroat trout stocks among watersheds,

primarily by terminating releases of fish in all but a few locations (discussed in “West Coast

Artificial Propagation Activities,” which follows). Coastal cutthroat trout programs in California

have generally used local stocks to supplement natural populations (Gerstung 1997).

West Coast Artificial Propagation Activities

Alaska

Hatchery experimentation with coastal cutthroat trout in Alaska has been restricted to

intermittent releases of smolts from Auke Creek, near Juneau, between 1983 and 1994 (Schmidt

1997). At present, no artificial propagation programs for coastal cutthroat trout are operating in

Alaska.

British Columbia

Coastal cutthroat trout have been propagated in British Columbia hatcheries since 1979.

Since then, about 3.1 million fish have been released, mostly into the lower Fraser River and

streams entering Georgia Strait (NRC 1996). Currently, 17 hatcheries produce coastal cutthroat

trout in British Columbia, using mostly local stocks to enhance recreational fisheries and

supplement native spawning populations (NRC 1996).
116

Washington, Oregon, and California

1) Puget Sound—Before the late 1950s, hatchery production of coastal cutthroat trout in

Washington consisted of nonanadromous forms. Westslope cutthroat trout, the first

nonanadromous salmonid cultured in Washington state, were released into lakes and streams in

eastern and western Washington as early as 1895 (Crawford 1979). The first state hatchery for

coastal cutthroat trout was built in 1905 at Lake Whatcom, near Bellingham, for local

distribution of fish from that lake. These fish were presumably a lacustrine form. The Lake

Crescent Hatchery was built in 1913 and propagated a lacustrine strain unique to that lake until

1946 (Crawford 1979). Between 1932 and 1946, coastal cutthroat trout used to stock waters in

western Washington were obtained from Cultus Lake, British Columbia, as well as from Lake

Crescent, Lake Whatcom, Lake Padden (near Bellingham), and Lake Washington, in Washington

State. Between 1934 and 1954, a captive broodstock of westslope cutthroat trout was reared at

the Vancouver Hatchery for release in Washington waters (Crawford 1979). In the 1930s and

1940s, several hundred thousand coastal cutthroat trout eggs were taken from fish in Lake

Washington tributaries and reared at the University of Washington for planting in local lakes

(Lynch 1941, Donaldson 1947). Since 1949, a captive broodstock derived from fish trapped in

Lake Whatcom tributaries has been held at the Tokul Creek Hatchery (Crawford 1979). Unlike

several sea-run cutthroat trout stocks in Washington, this nonanadromous stock has not been

mixed with other stocks at the hatchery (WDFW 1998b). In the late 1970s, this stock was

augmented with wild coastal cutthroat trout eggs obtained from Lake Whatcom tributaries

(Crawford 1979). These fish are used extensively for planting lowland streams, lakes, and

beaver ponds in the Puget Sound region.

There may be some potential for genetic interactions between the Lake Whatcom/Tokul

Creek hatchery coastal cutthroat trout stock and naturally spawning Puget Sound coastal

cutthroat trout stocks. For example, it was possible to cross Lake Whatcom fish with Lake

Washington fish for genetic studies at the University of Washington due to the fact that both

stocks spawned at the same time (Hansler 1958). However, no studies have been conducted that

demonstrate the extent of genetic exchange between coastal cutthroat trout populations in natural

environments.

Releases of anadromous cutthroat trout began in the mid-1960s in Puget Sound

tributaries, primarily as smolted fish. The stock source for most of these initial releases was

listed in Appendix A as “unknown” because it was identified as such on the WDFW electronic

database submitted to NMFS for this status review (NRC 1996). However, evidence from two

reports suggests that many of these unknown releases were actually stock transfers from the

Beaver Creek Hatchery in the Lower Columbia River (Johnston 1979, Hisata 1973). These early

transfers did not succeed in enhancing harvest in the Stillaguamish River (Johnston 1979, Leider

1997). However, in Hood Canal streams, the short-term impact of these large-scale plants on

sport harvest was apparent immediately: most fish caught in local streams were of the Beaver

Creek Hatchery stock, with a substantial degree of wandering or straying from the release site

(Hisata 1973). However, the overall catch rate of these Lower Columbia River fish in Hood

Canal was only 0.5% (Royal 1972). Few of these fish were recaptured in seawater; most
117

appeared to have residualized in fresh water (Hisata 1973). Royal (1972) observed that

residualism of hatchery coastal cutthroat trout was far more prevalent than in steelhead, perhaps

reflecting the more diverse life-history strategies exhibited by coastal cutthroat trout. Overall,

the introduction of Beaver Creek sea-run cutthroat trout into Hood Canal streams appears to have

had little direct effect on native populations, as few fish of spawning age were observed (Hisata

1973). Royal (1972) hypothesized that differences in rearing areas meant that hatchery-reared

coastal cutthroat trout residualizing in lower river sections would not compete with most

naturally produced native coastal cutthroat trout.

Anadromous cutthroat trout programs using local Puget Sound stocks were developed in

the early 1970s. An early-returning (September-October) Stillaguamish River stock was reared

at the Whitehorse facility on the North Fork Stillaguamish River. In addition, a late-returning

Stillaguamish River stock (December-January) and a Hood Canal stock were reared in seawater

net pens at the NMFS Manchester Laboratory (Crawford 1979). The Stillaguamish River

broodstock was especially difficult to adapt to seawater and was phased out in 1979 (Mercer and

Johnston 1979).

When it became apparent that introductions of hatchery coastal cutthroat trout had little

or no effect on the abundance of coastal cutthroat trout in Puget Sound tributaries, hatchery

programs were terminated. No plants of anadromous forms have been made in north Puget

Sound streams since 1985, and none have been planted in south Puget Sound or Hood Canal

streams since 1994 (Leider 1997, NRC 1996, WDFW 1998a).

Several hatcheries rear nonmigratory coastal cutthroat trout for planting in lowland lakes

or westslope cutthroat trout for use in alpine lakes, including the Lake Whatcom, Bellingham,

Arlington, Tokul Creek and Eells Springs hatcheries (Fuss and Ashbrook 1995). In 1998, coastal

cutthroat trout are scheduled for releases in just a few western Washington lakes—all of which

drain into Hood Canal—including Horseshoe, Tarboo, Koeneman, Wye, Benson, Cady Haven,

and Trails End lakes (WDFW 1998b).

2) Olympic Peninsula—There are no hatcheries dedicated to rearing coastal cutthroat trout in

this region, although occasional releases of fish reared in Lower Columbia River or Grays

Harbor facilities have occurred in area streams (NRC 1996).

3) Southwestern Washington/Lower Columbia River—The principal sea-run cutthroat trout

facility in Southwestern Washington is the Lake Aberdeen Hatchery, which began rearing a

mixed coastal cutthroat trout captive broodstock in the early 1980s (NRC 1996, Ashbrook and

Fuss 1996). This stock is a mixture of coastal cutthroat trout from tributaries of Grays Harbor

and other nearby coastal streams (Ashbrook and Fuss 1996). Every few years, additional genetic

material is introduced from naturally produced native adults captured in local streams.

As observed in the Puget Sound discussion about Hood Canal, releases of Beaver Creek

hatchery stock resulted in extensive wandering in the North River (Hisata 1973). In total, Grays

Harbor and Willapa Bay tributaries currently receive about 37,000 fish annually, primarily from
118

the mixed stock of coastal cutthroat trout reared at the Aberdeen Hatchery (NRC 1996, Leider

1997). This accounts for about 14% of the recent hatchery effort for coastal cutthroat trout in

Washington (Leider 1997).

Artificial propagation of the sea-run form of coastal cutthroat trout began in the Lower

Columbia River at the Beaver Creek Hatchery in 1958, with stocks obtained from the Nemah,

Green (Toutle River), and Elochoman rivers (Crawford 1979, Randolph 1986). Few returns

resulted from this mixture, and the stock was not used after 1965 (Crawford 1979). Between

1963 and 1968, eggs were imported from the captive broodstock held at the ODFW Alsea

Hatchery; after 1972, these fish were incorporated into the Beaver Creek Hatchery stock

(Randolph 1986). In addition, cutthroat x steelhead hybrid trout were mixed into the hatchery

stock in the late 1960s (Crawford 1979). However, the return rate was only 1.8%, there appeared

to be a high degree of residualism, and the straying rate was high (about 30%) (Randolph 1986).

To purge the hatchery stock of steelhead influence, “silvery” fish were not propagated at Beaver

Creek Hatchery. Instead, only heavily spotted individuals were spawned, as these fish were

thought more likely to be pure coastal cutthroat trout due to their coloration (Crawford 1979).

However, this procedure may have contributed to the high rate of residualism at this hatchery, as

it has been observed that anadromous cutthroat trout are silvery colored, while nonmigratory

coastal cutthroat trout, which need to be cryptically colored for freshwater residence, tend to be

coppery and more heavily spotted (Kostow 1995). The initial failure of the Beaver Creek

Hatchery program resulted in the realization that hatchery programs for coastal cutthroat trout

must be based on an appreciation of the genetic diversity of native stocks, with special

considerations given to local adaptations (Behnke 1992). Returns did not improve significantly

until introduction of the Cowlitz Hatchery stock in 1982, which increased returns dramatically

and enabled a self-sustaining program at the Beaver Creek Hatchery.

Time of spawning of natural coastal cutthroat trout in the Elochoman River is

significantly correlated with that of fish in the hatchery (Randolph 1986), which may indicate a

substantial contribution of hatchery fish in the naturally spawning component. For example,

between 1960 and 1965, natural and hatchery fish spawned in mid-January. After the early

1970s, natural and hatchery fish were spawning in December (Randolph 1986) due to a 3-week

advancement in spawn timing that may have resulted from broodstock selection at the hatchery

(Royal 1972).

The sea-run cutthroat trout program at the WDFW Cowlitz Hatchery was begun in 1968

with the Beaver Creek Hatchery stock and a few eggs from native Cowlitz River coastal

cutthroat trout (Crawford 1979). This program continued until 1975 and resulted in few returns

to the hatchery. After 1976, only fish returning to the Cowlitz Hatchery were spawned, resulting

in an increase in returns to the fishery and to the hatchery (Tipping and Springer 1980). For

example, by 1979, 60% of the Cowlitz in-river catch was hatchery fish, with a total return of

9,000 fish. Spawn timing in the hatchery stock has been advanced about 2 months earlier than in

naturally produced fish since the program’s start (Tipping and Springer 1980).
119

Currently, the largest component of hatchery efforts for coastal cutthroat trout in

Washington occurs in the Lower Columbia River with about 200,000 fish released annually,

mostly from the Cowlitz Hatchery (Leider 1997, NRC 1996). Approximately 75% of the total

effort in Washington is dedicated to this area (Leider 1997). In 1997, coastal cutthroat trout were

released into the Abernathy and Beaver creeks and the Coweeman, Cowlitz, and Lewis rivers

(WDFW 1997). In addition to state hatchery programs, a cooperative project between Clark

Public Utilities, Vancouver/Clark Parks and Recreation, WDFW, and Trout Unlimited is now in

its fifth year of releasing fish from net pens in a pond adjacent to Salmon Creek. About 10,000

coastal cutthroat trout from the Skamania Hatchery are released from this facility each year

(Shutt 1998). Leider (1997, p. 74) has suggested these hatchery releases “may also have

increased the occurrence of intraspecific ecological interactions or the incidence of maladaptive

gene flow from hatchery to wild sea-run cutthroat trout stocks.”

The Big Creek Hatchery sea-run cutthroat trout stock, developed from the natural

population in that stream, has been the primary stock used in Oregon Lower Columbia River

programs (Hooton 1997, Kostow 1995); numerically, however, Alsea Hatchery stock has been

used more often in the Lewis and Clark, Youngs, and Hood rivers and Gnat, Milton, and

Scappoose creeks (NRC 1996). In addition, a coastal cutthroat trout stock from the North Fork

Nehalem River has also been frequently introduced into Lower Columbia River streams in

Oregon (NRC 1996). The effects of long-term hatchery releases of coastal cutthroat trout on

natural production in Lower Columbia River tributaries in Oregon is unknown (Kostow 1995).

In Oregon, the planting of hatchery coastal cutthroat trout was discontinued in Lower

Columbia River streams by 1994. Currently, only standing bodies of water such as lakes and

ponds in the Lower Columbia River area are planted with hatchery fish (Hooton 1997, Kostow

1995).

4) Willamette River—Historically, tributaries of the Willamette River above Willamette Falls

received hatchery coastal cutthroat trout from a variety of sources. Coast Range tributaries

tended to get plants of anadromous stocks (mostly Alsea Hatchery fish), while Cascade Range

tributaries tended to receive the Leeburg stock, which appears to have been derived from a local

Willamette River freshwater strain native to the Long Tom River (NRC 1996). Most of the

hatchery effort in Willamette River tributaries occurred in the 1950s and 1960s (NRC 1996).

Currently, the only plants of hatchery coastal cutthroat trout in the Willamette River

basin are in Cascade Mountain lakes, using a native brood stock of coastal cutthroat trout known

as the Hackleman stock (Hooton 1997). The effects, if any, of these introductions on naturally

spawning stocks are unknown but are currently under investigation by ODFW (Kostow 1995).

5) Oregon Coast—The most notable feature of past coastal cutthroat trout hatchery programs in

Oregon coastal tributaries was the decades-long reliance on the Alsea Hatchery broodstock for

planting in lakes and streams over the entire Oregon coast, from Coffenbury Lake just below the

mouth of the Lower Columbia River to the Chetco River near the California border (Hooton

1997, NRC 1996). Several other hatchery stocks were occasionally used, such as the North Fork
120

Nehalem River, Nestucca River, Roaring River, and Coquille Hatchery (derived from Alsea

Hatchery) stocks (NRC 1996). The Alsea Hatchery stock has been in culture for about 40 years

(Kostow 1995, Randolph 1986). The genetic consequences of these programs on the hatchery

broodstocks is largely unknown (Kostow 1995).

 In the last 10 years, there has been a switch from planting hatchery coastal cutthroat

trout into streams to restricting plants to lakes and ponds on the Oregon coast (Kostow 1995,

Hooton 1997). Planting was discontinued in south Oregon coastal streams in the 1980s, in north

Oregon coastal streams in the early 1990s, the Rogue River basin in 1993, and most mid-Oregon

coastal streams in 1996 (Hooton 1997). Since 1997, no hatchery coastal cutthroat trout have

been planted in streams containing anadromous cutthroat trout (Hooton 1997).

6) Southern Oregon/California Coasts—Small numbers of Alsea Hatchery coastal cutthroat

trout were released in South Oregon streams prior to 1985 (NRC 1996). However, few releases

have occurred since then, and recent releases have been restricted to standing bodies of water.

No major programs for the enhancement or supplementation of coastal cutthroat trout

stocks have taken place in Northern California, although recent interest in the species has led to

the establishment of several small hatchery projects for anadromous cutthroat trout.

Coastal cutthroat trout have been reared at a hatchery facility associated with Humboldt

State University since at least the early 1990s. Some of these fish have been used in a joint effort

between the University, the California Department of Fish and Game (CDFG), and the City of

Arcata to develop a coastal cutthroat broodstock for enhancing recreational fisheries in northern

California coastal lagoons (AMWS 1998).

Between 1988 and 1992, very small releases of anadromous cutthroat trout (about 775

juveniles in total) were made from the CDFG COOP site on Prairie Creek, a tributary of

Redwood Creek (CDFG 1984-97). In 1993 and 1994, eight and five adult coastal cutthroat trout,

respectively, were collected at the weir on Rowdy Creek, but there is no indication that these fish

were spawned (CDFG 1984-97).

Discussion of and Conclusions about ESU Determinations

As discussed below, several factors make identification of ESUs particularly challenging

for coastal cutthroat trout.

Diversity of Life History

The life history of coastal cutthroat trout is perhaps the most complex of all the Pacific

salmonids. Coastal cutthroat trout exhibit a diverse array of migratory behaviors and a wide
121

range in the timing of migration and reproduction. Coastal cutthroat trout also do not necessarily

die after spawning. The life-history diversity of coastal cutthroat trout poses two formidable

challenges in ESU determinations: 1) understanding the factors that limit and promote this

diversity within and among populations, and 2) identifying geographically based conservation

units based in part on life-history variation. Unfortunately, we are not aware of direct

information on the genetic basis of life-history variation in any coastal cutthroat trout population

that would help address the first challenge, and the factors underlying life-history differences

among populations have not been characterized well enough to help resolve the second.

For coastal cutthroat trout, it is not known to what extent behavioral or physiological

adjustment, genetic polymorphism, or phenotypic plasticity contribute to life-history variation; it

is also unknown whether or to what extent individual fish express different life-history strategies

at different times. Possible mechanisms underlying expression of life-history variation include

these: 1) the variation expressed is completely environmentally determined, 2) the variation is

genetically hard wired, or 3) the variation reflects a combination of (perhaps many and small)

genetic and environmental influences. In the first case, information on life-history variation

would clearly be of little use in identifying meaningful ESU boundaries. At the opposite

extreme, ESU determinations would be facilitated considerably by knowledge that life-history

variation is genetically determined. As was discussed in “Life History” (p. 38), however, reality

almost certainly lies between these extremes. The focal issue for ESU determination is the

relative importance of genetic and environmental influences on life-history expression. Because

data that directly address this issue are not available for coastal cutthroat trout, it is prudent to

assume that both influences are important.

Consideration of life-history characteristics such as migratory behavior suggests two

possible (and at least partially conflicting) implications for the evolutionary ecology of coastal

cutthroat trout. On one hand, the relatively limited opportunities for marine dispersal may

promote stronger reproductive isolation in coastal cutthroat trout than occurs with Pacific salmon

and steelhead. Isolation of coastal cutthroat trout populations also may occur on a finer spatial

scale: groups of populations from different tributaries within the same large river basin may

experience reduced gene flow. All else being equal, strong reproductive isolation will promote

genetic divergence more rapidly than if gene flow is more frequent. Available genetic

information suggests that reproductive isolation of local populations has been a prominent

feature of the evolutionary ecology of coastal cutthroat trout. Because appreciable gene flow can

act to limit genetic differentiation under selection, reproductive isolation should foster more

rapid development of adaptations to individual watersheds or reaches within them. The genetic

evidence indicates that many of the coastal cutthroat trout populations sampled have been

isolated sufficiently to permit important adaptive differences to arise (see “Genetic Information”

section, p. 70).

On the other hand, although substantial reproductive isolation provides opportunities for

adaptive differentiation, it may not necessarily lead to marked local adaptations in freshwater

populations of coastal cutthroat trout. Marked adaptive differences among isolated freshwater

populations have been difficult to detect in some salmonids that contain both migratory and
122

nonmigratory forms. Stock transfers of kokanee (the freshwater form of O. nerka) and rainbow

trout, for example, have been successful over broad ranges in temperate North America and on

other continents, while stock transfers of anadromous sockeye salmon and steelhead within their

historic range have rarely been successful (Withler 1982, Busby et al. 1996, Gustafson et al.

1997). Wood (1995) and Allendorf and Waples (1996) suggested that this result can be

explained by the more complex life history of the anadromous populations. To complete its life

cycle and survive to reproduce, a Pacific salmon or steelhead must perform a long series of

precisely timed events, including freshwater residence, smoltification and outmigration, marine

feeding and migration, and the return migration to fresh water and spawning. Disruption of a

single link in this chain can substantially affect the fitness of a population. According to this

argument, freshwater populations of O. nerka and O. mykiss generally have a simpler life history,

with fewer conditions requiring local adaptation. On the other hand, salmonids will never be the

top predator in the ocean, which is a much larger arena than a freshwater lake; the opportunity in

the ocean for directed or stochastic mortality is also almost infinitely higher.

It is not clear to what extent these empirical observations for nonmigratory populations of

O. nerka and O. mykiss (and inferences about the importance of local adaptations) apply to

coastal cutthroat trout. Depending on the factors controlling the phenotypic expression of life

history, coastal cutthroat trout may be able to respond to a wide range of conditions at several

points in the life cycle. If environmental or ecological conditions are unfavorable for one

phenotype, it may be possible for the population to cope with these conditions–without serious

demographic or genetic consequences–through some form of life-history plasticity. This

capacity to adapt to changing conditions can be found to a limited degree in some populations of

O. nerka and O. mykiss, but the life-history options are generally fewer and their expression not

as pervasive as in coastal cutthroat trout. One result of this life-history diversity is that coastal

cutthroat trout populations may be buffered to some extent against extreme selective pressures

that promote local adaptations, resulting in selection for a more generalist phenotype.

Alternatively, the selection regime experienced by coastal cutthroat trout may control the degree

of plasticity itself that is expressed or the range of variation in phenotypes produced by a

particular mating. Available evidence is insufficient to discriminate between these alternatives,

and any of them could be responsible for the observed lack of strong geographic life-history

patterns for coastal cutthroat trout.

Paucity of Data

Although important data gaps have been identified in all of our coastwide status reviews

of Pacific salmon and steelhead, in general these gaps apply to particular types of information

and/or only to certain geographic areas. In contrast, coastal cutthroat trout are characterized by a

pervasive lack of quantitative information of almost all types across the range of the subspecies.

This is not to say that there is no information about coastal cutthroat trout: in fact, as discussed in

the preceding sections, there is a considerable amount of information about the biology of this

subspecies. However, much of this information is qualitative or descriptive, rather than

quantitative. Comprehensive sets of quantitative data, such as distribution, abundance, age
123

structure, and run timing, are largely absent for coastal cutthroat trout. The fact that coastal

cutthroat trout do not constitute a commercially important species, with fewer directed

recreational fisheries than for co-occurring Pacific salmon and steelhead, no doubt has much to

do with the paucity of these data. Furthermore, spawning coastal cutthroat trout are more

difficult to observe than spawning salmon, and there are almost no large runs that are clear

targets for systematic monitoring.

In the last few years, several studies have attempted to characterize the population genetic

structure of coastal cutthroat trout using allozyme and DNA markers. Although the various

genetic datasets in combination are not as large as for many species of Pacific salmon, they do

provide quantitative information for much of the range of the subspecies. In the other species of

anadromous Pacific salmonids reviewed by NMFS under the ESA, patterns of population genetic

differentiation were often substantiated by congruent patterns of life-history variation, thus

providing at least two lines of evidence to support ESU determinations. For coastal cutthroat

trout, this is generally not the case. A lack of life-history information, or the failure of existing

life-history data to show clear geographic patterns, means that the kind of genetic, ecological,

and environmental information that has proven useful for ESU determinations for Pacific salmon

assumes a relatively greater importance in ESU evaluations for coastal cutthroat trout. This lack

of information contributed to uncertainty in the ESU determinations, particularly for cases in

which the genetic data are somewhat equivocal.

Genetic Outliers

The genetic data set for coastal cutthroat trout is distinctive in having a number of

samples with allele frequencies that appear to represent extreme outliers. These outliers cover a

wide geographic range, are not characterized by any particular type of collection, and are

genetically distinctive, each in a unique way. It is difficult to determine how to deal with these

outliers in ESU determinations without a better understanding of the reason(s) for their

occurrence. Possible explanations involve four factors: sampling artifacts, founder effect/genetic drift, hybridization, and artificial propagation.

Sampling artifacts

The outlier samples could be nonrandom samples, perhaps representing progeny of just a

few individuals from a larger population, or a few spawning aggregations from a larger set within

a drainage. Alternatively, even random samples can seem unusual in their genetic makeup if

they are based on a small number of breeding individuals.

Founder effect/genetic drift

If some populations have been recently colonized by a very few founders, allele

frequencies could be shifted substantially from those of nearby populations; a similar pattern
124

could result from substantial isolation. The outliers examined in this analysis tend to have lowerthan-expected heterozygosity, suggesting that several of these populations may have experienced

founder effects or appreciable genetic drift.

Hybridization

Natural hybridization with O. mykiss is known to complicate the genetic analysis of

coastal cutthroat trout, and undetected hybridization (particularly involving backcross

generations) could result in substantial allele frequency shifts from typical coastal cutthroat trout

profiles. If, as hypothesized by Neillands (1990) and Hawkins (1997), hybrids tend to be

selected against during the anadromous phase, hybrids would then be expected to be more

prevalent in juvenile samples, such as those used in several genetic analyses of coastal cutthroat

trout. If different populations of O. mykiss were involved to varying degrees in the various

hybridization events, the genetic effects on coastal cutthroat trout populations would not

necessarily be uniform and could create outliers with varying genetic signatures.

Artificial propagation

Introductions of nonnative or artificially propagated fish into a natural population may

also change the genetic character of a natural population. However, the genetic influence of

outplanted hatchery coastal cutthroat trout on natural populations has been largely discounted by

WDFW (1998a) because hatchery fish generally have poor survival rates and are generally

highly exploited by anglers. Nevertheless, genetic similarities between some populations in

Oregon’s Coquille River and Alsea Hatchery fish appear to be attributable to the outplanting of

Alsea Hatchery fish into streams harboring these populations. These patterns could contribute to

some of the genetic outliers observed in our analyses.

Collectively, these four factors do not satisfactorily explain all, or even most, of the

genetic outliers. Many outliers, then, appear to reflect important aspects of the population

genetic structure of coastal cutthroat trout, and probably reflect a population structure that has

resulted from a wide range in the degree of reproductive isolation over small as well as large

geographic distances.

In summary, the genetic and life-history characteristics of coastal cutthroat trout differ

from those of other anadromous Pacific salmonids, but the implications of these differences for

ESU determinations are not clear. Considering only the opportunities for strong reproductive

isolation of individual populations, one might conclude that ESUs for coastal cutthroat trout

would be relatively small. On the other hand, available data for life-history and other

characteristics do not show strong geographic differences in traits likely to be involved in local

adaptations. This lack of geographic difference among the characters may reflect common

selective pressures for a generalist or highly plastic life-history strategy (in which case ESUs

might be relatively large), or it may reflect an inability of available information to reveal lifehistory patterns that exist on small scales within a highly diverse subspecies.
125

There is little doubt that the distinctive life-history characteristics of coastal cutthroat

trout result in interactions between the fish and their physical and biotic environments that differ

from those of other anadromous Pacific salmonids. Unfortunately, this fact alone provides little

information to aid ESU determinations. ESU boundaries that are congruent across several other

salmon species (reflecting similar historical processes and similar responses to physical/ecological habitat factors) may not be as relevant for coastal cutthroat trout, but the existing biological

data do not clearly reveal how coastal cutthroat trout ESUs should differ from those of the other

species, if indeed they should differ at all.

ESU Determinations

The BRT considered several possible ESU configurations for coastal cutthroat trout.

After considerable discussion, a majority of BRT members supported a scenario involving six

ESUs: Puget Sound, Olympic Peninsula, Southwestern Washington/Columbia River, Upper

Willamette River, Oregon Coast, and Southern Oregon/California Coasts (Fig. 32). Alternative

scenarios considered at length by the BRT were 1) a single ESU corresponding with the range of

coastal cutthroat trout and 2) multiple ESUs corresponding to small geographic units, such as

major river basins. Although the six ESUs supported by a majority of the BRT showed strong

similarities to those designated for other species (especially coho and chinook salmon and

steelhead), there are a few significant differences that reflect differences in genetic structure and

life-history variation.

Two general issues stimulated considerable discussion by the BRT; a summary of those

issues follows.

Life-history forms

The BRT was unanimous in concluding that each ESU include all life-history forms

(nonmigratory, freshwater migratory, and saltwater migratory) present. BRT members felt

strongly that the diversity of life-history forms occurring in each ESU represented genetic and

phenotypic resources characteristic of and important to its evolutionary ecology.

Barriers to migration

Barriers to migration separate the different life-history forms of coastal cutthroat trout in

some watersheds, and evaluating the significance of these barriers proved to be a challenging

problem. The BRT was divided regarding whether populations above long-standing natural

barriers (i.e., those that effectively preclude all migration for hundred or thousands of years)

should be included in ESUs. The primary argument for inclusion centered on the fact that

populations above barriers are often most closely related to those below them; it is therefore
126
127

unclear what ESU populations above barriers would belong in, if not in the ESU that includes

populations below the barrier. The argument for exclusion focused on the complete reproductive

isolation between populations above and below barriers and, consequently, the different

evolutionary trajectories followed by these groups of populations. Therefore, only under special

circumstances would the above-barrier populations be useful in recovering below-barrier ones.

With respect to barriers that permit some one-way migration (i.e., downstream migration

of smolts but not upstream passage of adults), the majority of BRT members felt that populations

above these barriers should be included in ESUs. The basis for this conclusion is twofold:

1) populations above barriers may contribute demographically and genetically to populations

below them, even if the frequency of successful one-way migrants per generation is low, and

2) populations above barriers may represent genetic resources shared by populations below these

barriers (and potentially a significant component of diversity for an ESU). In the case of the

upper Willamette River, however, the BRT unanimously concluded that populations of coastal

cutthroat trout above Willamette Falls are part of an ESU separate from those in the Columbia

River. A primary reason for this conclusion is that the river above the falls encompasses a large

area with considerable habitat complexity, and this area evidently supports several different

populations of coastal cutthroat trout.

ESU Descriptions

1) Puget Sound ESU

This proposed ESU includes populations of coastal cutthroat trout that enter protected

marine waters in northwestern Washington; its boundaries correspond roughly with the Puget

Lowland Ecoregion. Life-history data indicate that coastal cutthroat trout from Puget Sound

generally smolt at a smaller size and possibly a younger age than those entering coastal marine

waters, and genetic data indicate that these populations are separated from those in southwestern

Washington and farther south. Populations in Puget Sound and Hood Canal and on the Olympic

Peninsula are highly heterogeneous genetically; nevertheless, some evidence exists for coherent

genetic separation of populations on the Olympic Peninsula from those in the eastern Strait of

Juan de Fuca, northern Puget Sound, and Hood Canal. Populations in Hood Canal and along the

Strait of Juan de Fuca are distinctive but show no clear evidence of a transition zone between

Puget Sound and southwestern Washington. Populations from the upper Nisqually River (a

heavily glacially influenced system in southern Puget Sound) are markedly genetically distinct

from their nearest geographic neighbors. The BRT was unable to ascertain the source of this

distinctiveness; possibilities include strong and long-standing reproductive isolation, sharp

habitat differences, or a combination of these factors.

Based primarily on somewhat distinctive life-history patterns, the BRT concluded that

this ESU includes all streams in Puget Sound and the Strait of Juan de Fuca west to, and

including, the Elwha River. Available genetic data are consistent with this ESU boundary. The

northern boundary for this ESU is unclear, but unpublished genetic data (Williams unpubl. data)
128

lend support to the hypothesis that this ESU extends into southern British Columbia to include

populations along eastern Georgia Strait north of Vancouver. Williams’ data indicate that

Vancouver Island populations are genetically distinct from those on the mainland, providing

evidence for reproductive isolation of these groups. In general, this ESU’s boundaries reflect an

ecoregion in which river drainages have relatively high flows due largely to high precipitation,

snow melt, and temperatures moderated by the marine environment. The southern and western

boundaries are similar to those previously identified for chinook, coho, chum, pink salmon, and

steelhead; the northern boundary differs from those for chinook and coho salmon (which do not

extend into Canada) and pink, chum, and coho salmon (which do not include eastern Vancouver

Island).

2) Olympic Peninsula ESU

This proposed ESU includes coastal cutthroat trout in populations from the Strait of Juan

de Fuca west of the Elwha River and coastal streams south to, but not including, streams that

drain into Grays Harbor. The proposed boundaries of this ESU are similar to those for steelhead

and coho salmon. Support for this ESU relies primarily on the ecological distinctiveness of this

area, which is characterized by high precipitation, cool water temperatures, and relatively short

high-gradient streams that enter directly into the open ocean. Coastal cutthroat trout from this

area are relatively large as smolts, and a higher proportion appear to mature at first return from

seawater than is the case in most Puget Sound populations.

Genetic data for this ESU are limited. Populations sampled from the Olympic Peninsula

are genetically distinctive but show a stronger genetic affinity to neighboring populations in

Puget Sound and Hood Canal than to those along the Strait of Juan de Fuca (east of the Elwha

River). On the other hand, at least some of the Olympic Peninsula populations are not strongly

differentiated from those in northern or southern Puget Sound, and they are well differentiated

from populations to the south. Based primarily on these genetic data, a minority of the BRT

concluded that populations from the Olympic Peninsula should be considered part of a combined

Puget Sound-Olympic Peninsula ESU. Other BRT members pointed out that the Olympic

Peninsula ESU may represent a genetic transition zone between the Puget Sound and

southwestern Washington/Columbia River ESUs.

3) Southwestern Washington/Columbia River ESU

The proposed boundaries of this ESU are similar to the Southwestern Washington/Lower

Columbia River ESU for coho salmon (Weitkamp et al. 1995). Support for this ESU designation

comes primarily from ecological and genetic information. Ecological characteristics of this

region include the presence of extensive intertidal mud and sandflats, similarities in freshwater

and estuarine fish faunas, and substantial differences from estuaries north of Grays Harbor and

south of the Columbia River. The coastal cutthroat trout samples from southwestern Washington

show a relatively close genetic affinity to the samples from the Columbia River.
129

A minority of the BRT supported a split of Columbia River from southwestern

Washington coastal cutthroat trout populations. Tagging and recovery data for chinook, coho,

and chum salmon indicate different marine distributions for fish from the two areas. The limited

dispersal ability of anadromous cutthroat trout may restrict genetic exchange among populations

in the two areas, and the areas exhibit differences in their physical estuarine characteristics. An

important salmonid parasite, Ceratomyxa shasta, occurs in the Columbia River but has not been

observed in Willapa Bay or Grays Harbor. The WDFW, based on an unpublished analysis of a

small number of southwestern Washington populations, observed greater genetic differentiation

of populations in this ESU than was observed in the analyses described in “Regional patterns of

genetic variability” (p. 104). Furthermore, WDFW argued that extensive hatchery influence in

some populations may have obscured natural genetic differences between southwestern

Washington and Lower Columbia River coastal cutthroat trout. However, the majority of BRT

members felt that WDFW’s analyses were limited and that, collectively, available data did not

provide compelling evidence for a split between populations along the southwestern Washington

coast and those in the Columbia River.

4) Upper Willamette River ESU

Coastal cutthroat trout is one of only three species of anadromous Pacific salmonids that

historically occurred above Willamette Falls. Upper Willamette River populations of the other

two species—spring chinook salmon and winter steelhead—have been identified as separate

ESUs in previous status reviews, based on ecological factors, substantial genetic differences

from other Columbia River populations, and physical and hydrological conditions (Busby et al.

1996, Myers et al. 1998). Based on information provided by ODFW (1998), Willamette Falls is

a nearly complete barrier to anadromous fish (summer steelhead as well as coastal cutthroat

trout) during summer and early fall. The BRT concluded that the upper Willamette River has

probably never supported a substantial anadromous population of cutthroat trout; the primary

life-history form above Willamette Falls appears to be freshwater migratory, a type that seems

relatively rare below the falls.

Moreover, upper Willamette River coastal cutthroat trout exhibit a genetic structure

consistent with the hypothesis that the falls is a strong barrier to reproduction between

populations above and below the falls. The parasite Ceratomyxa shasta in the Willamette River

below the Marys River and high temperatures in the lower Willamette River in summer and fall

probably limit the survival of the very few migrants known to drop over the falls. Although the

populations above the falls are highly heterogeneous genetically, they do form a somewhat

coherent cluster of apparently isolated and semi-isolated populations.

The physical and genetic evidence of a barrier, habitat and ecological differences above

and below the falls, and the lack of anadromous populations and prevalence of freshwater

migratory forms above the falls led the majority of the BRT to conclude that coastal cutthroat

trout above Willamette Falls should be considered a separate ESU.
130

5) Oregon Coast ESU

Genetic data indicate marked genetic differences between coastal cutthroat trout from

coastal Oregon and those in the Columbia River and along the Washington coast. Samples of

coastal cutthroat trout south of the Columbia River indicate a large heterogeneous group of

populations along the Oregon coast. Furthermore, several ecological differences exist between

rivers along the Oregon coast and those farther north. The Oregon coast is characterized by a

strong maritime influence, including relatively high precipitation, moderate temperatures, and

short low-gradient streams with few migration barriers. Tagging studies in Alaska and elsewhere

indicate that anadromous cutthroat trout follow shorelines when in seawater; thus, the known

migratory patterns of this species are consistent with the hypothesis that the Columbia River,

which is several miles wide and relatively deep at its mouth, is a migratory barrier between

coastal populations in Oregon and those in Washington. The proposed boundaries of this ESU

are similar to the ESUs identified for coho and chinook salmon and steelhead.

The southern boundary of this proposed ESU is at Cape Blanco, Oregon. Although

genetic data provide only weak evidence for a split between populations north or south of Cape

Blanco, Oregon, ecological data do support such a split. The Cape Blanco area is a major

biogeographic boundary for many marine and terrestrial species, and has been identified as an

ESU boundary for chinook and coho salmon and steelhead on the basis of strong genetic, lifehistory, ecological, and habitat differences north and south of this landmark. Unpublished

meristic data (Williams, unpubl. data) also point to a difference between coastal cutthroat trout

populations north and south of Cape Blanco.

6) Southern Oregon/California Coasts ESU

A majority of the BRT concluded that populations of coastal cutthroat trout from Cape

Blanco south to the southern extent of the subspecies’ range represent a separate ESU. Several

members felt that the genetic and ecological data were not strong enough to support this split.

However, as described above, meristic (and, to some extent, genetic) information lends some

support for a separate coastal cutthroat trout ESU south of the major biogeographic boundary at

Cape Blanco. In addition, the limited dispersal capability of coastal cutthroat trout and anecdotal

evidence for marked differences in population dynamics for populations north and south of Cape

Blanco support a split at that landmark. Finally, most river systems in this ESU are relatively

small with limited estuaries and heavily influenced by a maritime climate. Many of these

systems are characterized by physical and thermal barriers to movement by anadromous fish;

notable exceptions that lack such barriers are the Eel, Klamath, Rogue, and Trinity rivers.

Alternative ESU Scenarios

The BRT considered several alternative ESU scenarios for coastal cutthroat trout. These

range from a single ESU corresponding to the entire subspecies to numerous small ESUs

corresponding to individual river basins. The BRT concluded that none of these scenarios is
131

completely satisfactory, but focused substantial discussion on two widely divergent scenarios

that some members felt merited serious consideration. Although neither was favored by a

majority of BRT members, the fact that both of these contrasting scenarios were taken seriously

is an indication of the considerable uncertainty associated with ESU determinations for coastal

cutthroat trout. These alternative ESU designations are outlined below.

Single ESU corresponding to the subspecies O. c. clarki

This scenario reflects one interpretation of the pattern of genetic and life-history diversity

in coastal cutthroat trout. The genetic diversity of this species illustrates strong differences

among populations from neighboring drainages but also substantial differences among putative

populations within these drainages. Indeed, coastal cutthroat trout exhibit a substantially greater

proportion of genetic variation expressed among populations than do most species of Pacific

salmon (sockeye salmon is an exception). When combined with the complexity of life-history

variation in coastal cutthroat trout, this pattern tends to obscure geographic patterns of

differentiation.

Several lines of reasoning could support determination of a single ESU. First, it may be

that, biologically, there are no conservation units of coastal cutthroat trout smaller than the

subspecies that can be considered separate ESUs under guidelines in NMFS policy. Second,

even if there are multiple ESUs within the subspecies, it may not be possible with current

information to identify their boundaries with any certainty; in this case, treating them

provisionally as a single ESU may be reasonable until better information is developed. Third, as

pointed out previously, populations of coastal cutthroat trout often exhibit high degrees of

genetic heterogeneity, with many genetic outliers occurring over relatively short geographic

distances. These results suggest a mosaic population structure that reflects varying levels of

reproductive isolation over a large range of geographic distances. This genetic heterogeneity

may thus be masking, at least partially, evolutionary affinities associated with biogeographic

provinces and potential adaptations within those provinces, making identification of smaller

ESUs difficult to justify.

The high degree of genetic differentiation among coastal cutthroat trout populations

inhabiting different river basins relative to that among ESUs (on average) could support an

argument for a single heterogeneous ESU corresponding to the range of coastal cutthroat trout.

However, an argument for a single coastwide ESU based on the substantial degree of genetic and

life-history variation among populations (including those within basins) is problematic because

available genetic evidence provides some support for a hypothesis that many populations of

coastal cutthroat trout coastwide are evolving largely independently of one another. Some BRT

members thought that the available data are equally consistent with a contrasting scenario

involving a larger number of small ESUs. It is unclear whether additional genetic data would

resolve this problem; several BRT members thought more comprehensive life-history information for coastal cutthroat trout populations probably would be helpful.
132

In the end, the majority of BRT members rejected this scenario in favor of one based on

six smaller units because of the combination of ecological, biogeographic, and genetic evidence

for finer-scale structure. Under either scenario, the BRT felt strongly that operational

conservation units would likely be substantially smaller than the ESUs.

Separate ESUs in major river basins

This ESU configuration recognizes the possibility that coastal cutthroat trout in major

river basins can be strongly isolated from populations in other basins and have a close affinity to

local freshwater environments. Although available life-history data do not show major interbasin differences among coastal cutthroat trout populations, environmental and ecological

differences among several basins have been documented and might form the basis for

adaptations of local populations. In addition, although the genetic differences observed among

coastal cutthroat trout populations within an ESU tend to be greater on average than those among

ESUs, substantial variation can also be detected within drainages. Thus, appreciable

reproductive isolation of individual breeding populations may occur on smaller geographic scales

than for other species of Pacific salmon. The genetic and life-history data are therefore not

entirely consistent with ESUs based on major river basins; indeed, it is not clear what criteria

would be used to identify basins that could be considered separate ESUs, or where to include

populations from smaller systems not associated with major basins. However, many BRT

members felt that major river basins might be useful as a template for identifying operational

conservation units within larger ESUs.

Umpqua River Coastal Cutthroat Trout

In the status review of Umpqua River coastal cutthroat trout (Johnson et al. 1994), the

BRT concluded that all life-history forms in the Umpqua River were part of the same ESU but

was unable to reach a conclusion on the geographic extent of the ESU. This more comprehensive review has not completely resolved this question. Although Umpqua River coastal

cutthroat trout are provisionally identified here as part of a larger Oregon Coast ESU, the

possibility that ESUs should be recognized on a smaller scale has not been excluded.

Relationship to State Conservation Management Units

State conservation management units have not yet been completed for coastal cutthroat

trout in California, Oregon, or Washington, although WDFW has proposed preliminary stock

groupings as part of their draft “1998 Coastal Cutthroat Stock Inventory” (WFDW 1998a). This

document follows the format of the “Salmon and Steelhead Stock Inventory” (SASSI), but its

name has been changed to “Salmonid Stock Inventory” (SaSI) to reflect the inclusion of coastal

cutthroat trout. The stock definition criteria used in SaSI is similar to that in SASSI, but rather
133

than identifying “stocks,” SaSI identifies groupings defined as “stock complexes.” Stock

complexes were developed “because of the significant uncertainties regarding the life-history,

genetic, and evolutionary relationships among life-history types in local areas” for coastal

cutthroat trout (WDFW 1998a, p. 31), and represented the aggregation of fish from adjacent

areas with common habitat characteristics (e.g., eastern Hood Canal). The stock complexes in

the SaSI draft were based on known differences in spatial or temporal distribution, “primarily in

river basins in which spawning is known to occur,” and “used available information on unique

biological characteristics (e.g., genetic stock identification data)” (WDFW 1998a, p. 31). These

stock complexes were considered preliminary, and as “additional information on genetics, life

histories and ecological relations” become available, this information will be incorporated into

future versions of SaSI.

Based on these criteria, SaSI (WDFW 1998a) identified 46 coastal cutthroat trout stock

complexes (23 in Puget Sound and the Strait of de Fuca, 12 on the Washington Coast, and 11 in

the Lower Columbia River). Stock complexes in the Puget Sound region represented 50% of the

state’s number, while complexes from the Washington Coast and Columbia River each contained

approximately 25%.

The ESUs for coastal cutthroat trout proposed by the BRT are larger than the stock

complexes proposed in SaSI (the Puget Sound ESU, for example, includes approximately 22

stock complexes). The SaSI it was concluded that “the number of individual coastal cutthroat

stocks may be very large [in Washington] and that identification of stock complexes is

appropriate as a first step in understanding coastal cutthroat population structure” (WDFW

1998a, p. 31-32).

In conjunction with SASSI on Pacific salmon and steelhead, WDFW identified Major

Ancestral Lineages (MALs) and Genetic Diversity Units (GDUs, which represent subsets of

MALs) in Washington (e.g., Busack and Shaklee 1995). According to Busack and Shaklee

(1995), GDU designations were based on a combination of genetic, life-history/ecological, and

physiographic/ecoregion data. The authors also said they expected that individual ESUs would

often include multiple GDUs but would be unlikely to include multiple MALs. No GDUs or

MALs have yet been identified by WDFW for coastal cutthroat trout.
134
135

ASSESSMENT OF EXTINCTION RISK

The ESA (Section 3) defines “endangered species” as “any species which is in danger of

extinction throughout all or a significant portion of its range.” “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 distributions, 2) current abundance in relation to

historical abundance and carrying capacity of the habitat, 3) trends in abundance, based on

indices such as dam or redd counts or on estimates of spawner-recruit ratios, 4) natural and

human-influenced factors that cause variability in survival and abundance, 5) possible threats to

genetic integrity (e.g., selective fisheries and interactions between hatchery and natural fish), and

6) recent events (e.g., a drought or a change in management) that have predictable short-term

consequences for abundance of the ESU. Additional risk factors, such as disease prevalence or

changes in life-history traits, also may be considered in evaluating risk to populations.

According to the ESA, the determination of whether a species is threatened or endangered

should be based on the best scientific information available regarding its status after taking into

consideration conservation measures that are proposed or in place. The BRT did not evaluate

likely or possible effects of conservation measures. Therefore, they did 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 the BRT. However,

the BRT did draw scientific conclusions about the risk of extinction faced by identified ESUs

under the assumption that present conditions will continue (recognizing, of course, that natural

demographic and environmental variability is an inherent feature of present conditions).

Conservation measures will be taken into account by the NMFS Northwest and Southwest

Regional Offices in making listing recommendations.

Approach

Previous Assessments

Several recent reviews have been conducted of the status of coastal cutthroat trout

populations (Nehlsen et al. 1991, Chilcote et al. 1992, Nickelson et al. 1992, Kostow 1995,

Gerstung 1997, Hooton 1997, WDFW 1998a). These reviews used a variety of methods and

criteria for evaluating the status of coastal cutthroat trout stocks. Nehlsen et al. (1991)

considered the status of populations coastwide and evaluated their risk of extinction, but reported

the status only of populations they considered to be at risk of extinction, categorizing them as

“possibly extinct,” at “high risk of extinction,” at “moderate risk of extinction,” or of “special

concern.”
136

Nehlsen et al. (1991) considered populations at high risk of extinction to have likely

reached the threshold for classification as endangered under the ESA. Stocks were placed in this

category if they had declined from historic levels, were continuing to decline, or had spawning

escapements of less than 200. Populations were classified at moderate risk of extinction if they

had declined from historic levels, but presently appeared to be stable at a level of more than 200

spawners. Nehlsen et al. (1991) felt that populations in this category had reached the threshold

to be considered threatened under the ESA. Populations were classified to be of special concern

if a relatively minor disturbance could threaten them, insufficient data were available for them

but available information suggested a decline, large releases of hatchery fish influenced them, or

they possessed some unique characteristic. Nehlsen et al. (1991) also included a partial list of

populations they believed to be extinct. The other reviews are limited to individual states and are

thus more limited in area, but they are intended as inventories of populations and are more

thorough within the areas they cover.

Washington

As noted earlier, WDFW (1998a) has extended the SASSI effort (WDF et al. 1993) to

include a Salmonid Stock Inventory (SaSI) that reports on the status of char and coastal cutthroat

trout in Washington State. Stock “complexes” were identified for coastal cutthroat trout because

of the difficulty in identifying individual stocks. A stock complex is a “group of stocks typically

located within a single watershed or other relatively limited geographic area,” and includes

information on genetic similarity among river systems from genetic analyses (WDFW 1998a,

p. 21). The SaSI classified stock complexes by origin (native, nonnative, mixed, or unknown),

production (wild, composite, or unknown), and status (healthy, depressed, critical, or unknown).

Stock status was classified as healthy if recent production was consistent with current habitat

conditions. The status report is complicated, however, by the WDFW (1998a) practice of

combining hatchery with natural production if a hatchery was located on a stream that supported

natural spawning; the status report considered only recent production status, and thus did not

consider possible negative impacts of hatchery production on natural populations. WDFW

(1998a) recognized 46 coastal cutthroat trout stock complexes in Washington. Of these

complexes, 2 were rated healthy, 6 were depressed, none were critical, and 38 were of unknown

status. The proportion of stock complexes with unknown status is much higher than for any

other salmonid species inventoried in Washington (WDF et al. 1993).

Nehlsen et al. (1991) considered coastal cutthroat trout in Washington coastal and Puget

Sound tributaries, as well as the Elochoman, Cowlitz, Toutle, Coweeman, Kalama, and

Washougal rivers, to be of special concern. Coastal cutthroat trout populations in small

tributaries on the Lower Columbia River below Bonneville Dam were considered to be at

moderate risk of extinction. The stock in Rock Creek in Washington was considered to be at

high risk of extinction. In contrast, WDFW (1998a) listed the status of most Puget Sound and

coastal Washington coastal cutthroat trout runs as unknown. Finally, SaSI concluded that coastal

cutthroat trout in the Lower Columbia River streams and smaller tributaries were depressed,

which is similar to the findings of Nehlsen et al. (1991).
137

Oregon

Within Oregon, Nehlsen et al. (1991) considered coastal cutthroat trout in the Hood River

to be at high risk of extinction. In addition, coastal cutthroat trout in Lower Columbia River

streams below Bonneville Dam and in Oregon coastal streams were listed at moderate risk of

extinction.

Chilcote et al. (1992) inventoried anadromous and nonanadromous coastal cutthroat trout

runs in Oregon and evaluated them for gene conservation purposes under the Oregon Wild Fish

Policy (Chilcote et al. 1992). This policy has two compliance criteria: a hatchery criterion that

naturally spawning populations have no more than 10% strays from a genetically dissimilar

hatchery stock or 50% strays from a genetically similar hatchery stock, and a numerical criterion

requiring a minimum average of 300 spawners. Kostow (1995) is a revision of Chilcote et al.

(1992), with newer information on stock presence or absence. Chilcote et al. (1992) considered

3 of 128 populations of sea-run cutthroat trout and 35 of 630 populations of either freshwater

migratory or nonmigratory coastal cutthroat trout to be in compliance with the Wild Fish Policy

criteria. For sea-run cutthroat trout populations, 6 were not in compliance due to violation of the

percentages of hatchery strays and their genetic constitution, 1 population was not in compliance

because its population had fewer than 300 individuals, and the remaining 118 populations were

not in compliance because of lack of information. For freshwater coastal cutthroat trout

populations, 595 populations were not in compliance because of insufficient information.

Nickelson et al. (1992) evaluated the status of coastal populations of coastal cutthroat

trout in Oregon. They stated that most coastal populations of coastal cutthroat trout in Oregon

were of unknown status due to insufficient data. They discussed anecdotal information, results

from creel surveys, and fish counts at dams that all indicated that anadromous cutthroat trout

populations “may be experiencing widespread decline” (p. 58).

The 1994 biennial report on wild fish status in Oregon (Kostow 1995) provided a list of

all coastal cutthroat trout populations and the life-history forms of coastal cutthroat trout in each

stream. The abundance of anadromous cutthroat trout in the Lower Columbia River Basin was

described as having declined significantly, and populations of sea-run cutthroat trout in the

Sandy and Hood rivers were described as very small to nonexistent, respectively, in 1994. The

report also stated that anadromous cutthroat trout occurred only in the lower Willamette River

below Willamette Falls and that occurrences in the Clackamas River were much less abundant

than in the past, although freshwater forms of coastal cutthroat trout were described as “abundant

and well distributed throughout headwater and lower Clackamas River tributaries” (p. 162). No

abundance information was available for coastal cutthroat trout in coastal Oregon streams except

for counts of fish over Winchester Dam on the North Umpqua River.

ODFW’s “Status of Coastal Cutthroat Trout in Oregon” (Hooton 1997) reviewed

abundance and trend information for all life-history forms of coastal cutthroat trout. Nonmigratory coastal cutthroat trout were reported to be widespread and “the dominant trout in most

headwater tributaries”; however, population sizes were described as likely to be lower in

abundance than in the past due to habitat degradation and loss (p. 1). River- and lake-migrating
138

forms of coastal cutthroat trout were reported to have mixed status: some populations were

considered healthy, but for many, information was insufficient to determine population health.

Anadromous cutthroat trout in Oregon were likely to have suffered significant declines in the

past decade, according to the review. Details provided in Hooton (1997) for specific coastal

cutthroat trout populations are discussed for each ESU in the “Biological Information by ESU”

section (p. 158), which describes biological information used in making risk evaluations.

Umpqua River sea-run cutthroat trout status review

As discussed earlier, a status review of sea-run cutthroat trout in the North and South

Umpqua rivers was conducted in 1993-94 in response to a petition NMFS received in 1993 to list

those fish under the ESA (Johnson et al. 1994). The primary abundance information available

for evaluating the conservation status of coastal cutthroat trout in the entire Umpqua River Basin

was counts of migrating fish passing Winchester Dam on the North Umpqua River. The

numbers of coastal cutthroat trout at Winchester Dam declined precipitously in the late 1950s,

then increased in 1961-76, coincident with a period of releases of hatchery coastal cutthroat trout

in the North Umpqua River. After hatchery releases were terminated in the mid-1970s, the

numbers of coastal cutthroat trout at Winchester Dam declined rapidly. Abundances remained

very low: 34, 10, and 0 coastal cutthroat trout were counted at the dam from 1991 to 1993,

respectively. Angler creel censuses for 1977, 1990, and 1992 were available for freshwater

forms of coastal cutthroat trout caught in the Umpqua River Basin; however, estimates of fishing

effort or harvest rate were not available, so angler catch data were not expanded to estimate

nonanadromous coastal cutthroat trout abundance for the basin.

In addition to declining trends in abundance, the Umpqua River coastal cutthroat trout

probably also faced risks due to the effects of hatchery fish. The Umpqua River Basin has a long

history of hatchery releases for a number of species, including steelhead, rainbow trout, and

coastal cutthroat trout. These releases date back to the late 1880s, and their impact is unknown.

Because hatchery practices were not well developed prior to the early 1950s, it is generally

believed that most of these early hatchery plants had few permanent impacts on native fish

populations (Johnson et al. 1994). During the period of extensive releases of Alsea River coastal

cutthroat trout broodstock into the North Umpqua River (1961-73), the return timing of coastal

cutthroat trout at Winchester Dam shifted to reflect the later return times characteristic of the

Alsea River broodstock (Johnson et al. 1994). The shift in the run-time distribution suggested

that, during the years when hatchery coastal cutthroat trout were released in the North Umpqua

River, the relative abundance of native Umpqua River coastal cutthroat trout was depressed. No

genetic data were available to determine whether genetic introgression between the Alsea River

broodstock and coastal cutthroat trout native to the Umpqua River Basin had occurred, or

whether the hatchery fish had replaced the native fish.
139

Scarcity of information on the status of coastal cutthroat trout in the Umpqua River Basin

brought the BRT to note that a listing determination for these fish could come to one of two

conclusions:

1. Since the petition was for “sea-run” coastal cutthroat trout, and nonanadromous coastal

cutthroat trout were determined to be part of the Umpqua River Basin ESU, “the petition

could be denied because the petitioned entities (North and South Umpqua River sea-run

cutthroat trout) are not by themselves ESA ‘species’” (Johnson et al. 1994, p. viii).

2. Because the anadromous portion of the ESU was suffering severe declines in abundance, the

coastal cutthroat trout in the Umpqua River Basin could be considered at significant risk.

Even if it were assumed that coastal cutthroat trout in the Umpqua River constitute an ESU,

the second conclusion would also involve assuming that either all life-history forms of coastal

cutthroat trout in the basin were depressed, or that the anadromous portion was “a substantial and

important component of the ESU and its loss would compromise the distinctness and viability of

the inclusive ESU” (Johnson et al. 1994, p. ix). The BRT concluded that there was not enough

information to resolve these issues with any certainty.

After considering the BRT’s report, NMFS in 1994 proposed that the Umpqua River searun cutthroat trout be listed as endangered under the ESA. The final listing was effective in

August 1996.

California

Nehlsen et al. (1991) characterized coastal cutthroat trout populations in California

coastal streams as being at moderate risk of extinction.

Gerstung (1997) reviewed the status of coastal cutthroat trout in California. He

concluded that most populations were depressed relative to historical abundance. Population

abundance and trend data were scarce, but for those river systems with data available, trends

were described as stable or increasing over the last few decades. Details provided in Gerstung

(1997) for specific coastal cutthroat trout populations are discussed in this document under

individual ESUs in “Biological Information by ESU” (p. 158).

Data Evaluations

Quantitative evaluations of data amassed as part of this status review included

comparisons of current and historical abundance of coastal cutthroat trout and calculation of

recent trends in abundance estimates. Historical abundance information for the six ESUs

proposed in this report is largely anecdotal. Time-series data were available for very few

populations, and the amount and quality of the data varied among ESUs. We compiled and

analyzed this information to provide several summary statistics of the abundance of natural
140

spawning populations, including (where available) recent total spawning run size and

escapement, abundance indices for smolts and adults, percent annual change in abundance, and

separate estimates of hatchery-derived and naturally spawning populations.

Although this evaluation used the best data available, it should be recognized that there

are limitations to the few data sets that do exist and not all summary statistics were available for

all populations. For example, abundance in some cases was estimated from recreational catch

(which may not always have been measured accurately) or from limited survey data. In some

cases, data indicating abundance of coastal cutthroat trout were incidental catch of cutthroat in

traps or sport fisheries targeting other species of Pacific salmon or steelhead. In many cases,

limited data also were used to separate hatchery production from natural production.

Information on stock abundance was compiled from records in a variety of state, federal,

and tribal agencies. We believe this information to be largely complete with respect to long-term

adult abundance records for coastal cutthroat trout in the regions included in this review.

Principal data sources were fishery statistics from recreational fisheries, escapement estimates

from dam and weir counts, and smolt abundance estimates from downstream migrant traps.

However, although the types of data described above provide the “best” estimates of coastal

cutthroat trout production for fishery comanagers, actual run size may vary from these estimates.

Specific problems are discussed below for each data type.

Computed Statistics

To represent current abundance where recent data were available, we computed the

geometric mean of the most recent 5 years reported (or fewer years, if the data series was for less

than 5 years). Where adequate data were available, trends in abundance estimates were

calculated for all data sets with more than 5 years of data, based on total escapement or an

escapement index (such as fish per mile from a stream survey).

As an indication of overall trends in coastal cutthroat trout populations in individual

streams, we calculated average percent annual change (over the available data series) in

abundance data or 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.

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.

Except in cases where data were separated into hatchery and natural fish, estimated trends

include any supplementation effects of hatchery fish. Trend analysis can also be influenced by

climate regime shifts and other factors.
141

Overall Evaluation of Risk and Uncertainty

To tie the various risk considerations into an overall assessment of extinction risk for

each ESU, the BRT members scored risks in a number of categories using a matrix form.

The general risk categories evaluated were those outlined earlier: abundance, trends in

abundance/productivity/variability, genetic integrity, and “other risks”. More detailed

explanation of these categories and of the nature and use of this matrix approach is provided in

Appendix B.

The summary of overall risk to an ESU uses categories that correspond to ESA

definitions: in danger of extinction, likely to become endangered in the foreseeable future, or

neither. Note, however, that these votes on overall risk do not correspond to recommendations

for a particular listing action. They are based only on the past and present biological condition of

the populations and do not completely evaluate conservation measures as the ESA requires for a

listing determination. The risk summary votes do not reflect a simple average of the risk factors

for individual categories, but rather a judgement of overall risk based on likely interactions

among risk factors and their cumulative effects. A single factor with a “high risk” score may be

sufficient for an overall conclusion of “in danger of extinction,” but such an overall

determination could result from a combination of several factors with low or moderate risk

scores.

The BRT used two methods to characterize the uncertainty underlying their risk

evaluations. Because information relating to the abundance, life history, and distribution of

coastal cutthroat trout is unavailable in many areas, risk evaluations were especially challenging

(see “Paucity of information relating to risk,” p. 195). One way the BRT captured the levels of

uncertainty associated with overall risk evaluations was for each member to attach a certainty

score (1=low, 5=high) to their overall risk evaluation for each ESU. For example, a BRT

member who believed an ESU was very likely to become endangered in the foreseeable future

(or was not currently at significant risk) would vote for that category of risk and assign a

certainty score of 4 or 5; a member less certain about a given level of risk would assign a lower

certainty score.

The second method for characterizing uncertainty was fashioned after an approach used

by the Forest Ecosystem Management Assessment Team (FEMAT 1993). Each BRT member

was given 12 total “likelihood” points to distribute in any way among the three risk categories.

For example, complete confidence that an ESU should be in one risk category would be

represented by most or all of the 12 points allocated to that category. Alternatively, a BRT

member who was undecided about whether the ESU was likely to become endangered but who

believed the ESU was at some risk could allocate the same (or nearly the same) number of points

into each of the “likely to become endangered” and “not likely to become endangered”

categories. This assessment process follows well-documented peer-reviewed methods for

making probabilistic judgements (references in FEMAT 1993, p. iv:40-45). The BRT

interpretation of these scores was similar to FEMAT’s, which said the likelihoods were “not

probabilities in the classical notion of frequencies. They represented degrees of belief [in risk
142

evaluations], expressed in a probability-like scale that could be mathematically aggregated and

compared across [ESUs]” (FEMAT 1993 p. iv:44).

The outcomes of the two methods for evaluating uncertainty in risk evaluations were

generally consistent (see “Summary and Conclusions of Risk Assessments,” p. 194). The BRT

felt that clear presentation of the scientific and personal uncertainty underlying risk assessments

could allow BRT members and managers to better understand the issues and make informed

listing decisions.

Analysis of Biological Information

Species-wide Risk Factors Considered

Detailed information on the nature of risks in specific geographic regions is not available

for a number of risk factors affecting coastal cutthroat trout. However, there is some information

that provides an indication of the likely effects of these risk factors on coastal cutthroat trout or

on Pacific salmonids in general. Aspects of several of these risk considerations are common to

all coastal cutthroat trout ESUs. In this section, we briefly summarize information the BRT

considered regarding the potential effects of each risk factor on coastal cutthroat trout. More

specific discussion of factors for each of the ESUs under consideration can be found in the

following sections.

Absolute numbers

The absolute number of individuals in a population is important in assessing two aspects

of extinction risk. First, for small populations that are stable or increasing, population size can

be an indicator of whether the population can sustain itself into the future in the face of

environmental fluctuations and small-population stochasticity; this aspect is related to the

concept of minimum viable populations (MVP) (see Gilpin and Soulé 1986, Thompson 1991).

Second, for a declining population, present abundance is an indicator of the time expected until

the population reaches critically low numbers; this aspect is related to the idea of “driven

extinction” (Caughley 1994).

In addition to total numbers, the spatial and temporal distributions of adults are important

in assessing risk to an ESU. Spatial distribution is important both at the scale of river basins

within an ESU and at the scale of spawning areas within basins (“metapopulation” structure).

Temporal distribution is important both among years, as an indicator of the relative health of

different brood-year lineages, and within seasons, as an indicator of the relative abundance of

different life-history types or runs.

Traditionally, assessment of salmonid populations has focused on the number of

harvestable and/or reproductive adults, and these measures compose most of the data available
143

for Pacific salmonids. 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 the size of the potential spawning

population if there is no 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.

The offspring of all coastal cutthroat trout artificially spawned for a hatchery, restoration, or egg

box program are included under the NMFS category “hatchery provided,” although we recognize

that different types of propagation programs will have different results. 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 comprised of

two components (Fig. 33): “hatchery-produced fish,” which are reared as eggs or juveniles in a

hatchery but return as adults to spawn naturally, and “natural” fish, which are progeny of

naturally spawning fish.

Life-history diversity and risk

The variety of migratory and life-history patterns observed in coastal cutthroat trout

means that abundance estimates do not indicate status as clearly as they might for other species

of salmonids. First, it is not a simple matter to identify a “run” of coastal cutthroat trout and

count adult or juvenile individuals that contribute to that run. Because both adults and juveniles

can migrate extensively within a stream or lake system throughout a year, it is difficult to

determine how many downstream or upstream migrants passing a particular location should be

attributed to a specific spawning population.

Second, since coastal cutthroat trout spawn multiple times, risk thresholds associated

with particular levels of population size cannot be estimated in the same way as they are for

Pacific salmon, which are semelparous. For example, a spawning population of salmon

estimated at 100 fish per year might translate into approximately 400-500 chinook salmon per

generation, accounting for multiple age classes. In contrast, 100 fish per year in a cutthroat trout

population might reflect closer to 200 individuals per generation because of the relatively high

frequency of repeat spawners in the population. The consequences of iteroparity exhibited by

coastal cutthroat trout must be taken into consideration when evaluating estimates of population

sizes.

Third, it is not clear to what extent a diversity of life-history forms within a river basin or

ESU may buffer coastal cutthroat trout populations from risk. In a practical sense, this gap in our

knowledge means that it also is not a simple matter to evaluate the status of coastal cutthroat

trout ESUs. As discussed earlier (see “ESU Determinations,” p. 125), the diversity of lifehistory strategies exhibited by coastal cutthroat trout may make these fish more able to adjust to

changes in habitat quantity and quality. If this diversity is important, declines in one or more
144
145

life-history forms within an ESU may represent a significant threat to the persistence of coastal

cutthroat trout in that ESU. For example, loss of the anadromous form would reduce the number

of larger and more fecund individuals in the population. A reduction in the number of

anadromous individuals in a population would probably also have significant effects on the

population age structure, spawn timing, age and size at first reproduction, degree of iteroparity,

sex ratio, spatial distribution of individuals, and mate selection. In particular, migratory fish

have opportunities for habitat, prey, and mate selection that may not be available to

nonmigratory fish. Likewise, loss of freshwater forms would lead to a loss of potential colonists

or recolonists, leading to increased genetic and demographic isolation of populations. The

reduction in potential within-basin recolonists could disrupt existing metapopulation dynamics,

change the spatial distribution of populations over a geographic region, and lead to a loss of

unique local adaptations in nonmigratory populations. Finally, migration can provide a

population with an “escape in space” (Slobodkin 1961) if rearing or spawning habitat is lost or

degraded by permitting a population to persist when it otherwise might be locally extirpated

(Taylor and Taylor 1977).

As an illustration of the potential consequences of reducing life-history diversity, most

biologists would agree that the anadromous life-history type is crucial to the ability of coastal

cutthroat trout populations to colonize new habitat (or to recolonize previously occupied habitat).

Reduced opportunities for dispersal among coastal cutthroat trout populations due to reductions

in the anadromous form could cause dramatic increases in local population extinctions due to the

demographic and genetic effects of isolation. If too many local populations are extirpated, the

metapopulation dynamics in a region may be severely disrupted, leading to the eventual

extinction of an entire ESU. Unfortunately, it is not a simple matter to evaluate this possibility–

abundance estimates that include a mix of life-history types may mask declines in one form that

is critical to ESU persistence. In addition, even if the status of a life-history form can be

determined, the risk implications of a change in relative abundance of a life-history type depend

in part on the genetic control of the life history (see “Mechanisms of Life-History Expression,”

p. 47). In the example above, if the anadromous portion of a coastal cutthroat trout run is lost,

the significance of such a loss will depend on the extent to which freshwater forms of coastal

cutthroat trout in the same (or nearby) river basin can replace anadromous fish that were lost.

A related question is if the anadromous form is selected against (e.g., if an artificial

barrier is imposed where there previously was none), how long will it take for the genetic

variation allowing anadromy to be lost from a population? There is some indication from other

species of Pacific salmon that strong selective differences on anadromous and freshwater forms

can lead to rapid genetic divergence (e.g., sockeye salmon and kokanee). It also has been

observed in O. nerka that populations above a long-standing barrier can still give rise to

anadromous individuals if the conditions for migrating to sea are provided (e.g., Cultus Lake

kokanee) (Foerster 1968). However, the pertinence of these case studies of other species of

salmonids to coastal cutthroat trout is unknown.

Many biologists familiar with coastal cutthroat trout feel that this subspecies is well

distributed in freshwater habitats throughout its range. The few data available for this status

review mostly support this contention for freshwater forms of coastal cutthroat trout (see
146

“Biological Information by ESU,” p. 158). In addition, there is some information suggesting that

freshwater forms of coastal cutthroat trout in some streams can produce outmigrating juveniles

that have a silvery “smolt-like” appearance (see “Patterns of Life History Variation,” p. 40 and

“Biological Information by ESU,” p. 158). The ability of these fish to successfully migrate to

salt water and return to spawn is not well quantified. In some cases, it is suspected that current

habitat conditions in the lower reaches of streams or in nearshore marine environments are not of

sufficient quality to allow survival of these outmigrants (e.g., in the Willamette River, ODFW

1998). In this case, freshwater life-history types would not be able to replenish anadromous

forms under current habitat conditions. On the other hand, ODFW (1998) and WDFW (1998c)

believe that smolts from freshwater forms of coastal cutthroat trout are contributing to adult

returns in several Oregon coastal streams and in some streams in the Lower Columbia River

Basin. Currently, there is not enough information to evaluate the likelihood that these alternative

scenarios occur throughout the range of coastal cutthroat trout. Presumably, the ability of

freshwater forms of coastal cutthroat trout to contribute to anadromous forms varies with river

basin characteristics and the genetic composition of the populations within each basin.

A key question for risk evaluations of coastal cutthroat trout is whether current habitat

and population characteristics (e.g., habitat quality and quantity, population sizes, age and size

structure) allow for the full expression of life-history types that would be observed under pristine

conditions. It is likely that human activities have altered life-history profiles of coastal cutthroat

trout, but predicting the magnitude of these effects is difficult (see “Life History,” p. 38). For

example, impoundments in many streams throughout much of the range of coastal cutthroat trout

have resulted in lower flows and higher water temperatures, conditions favorable to the parasite

Ceratomyxa shasta. Some populations of coastal cutthroat trout in the Lower Columbia River

Basin are highly susceptible to C. shasta, which can cause very high mortalities. It is possible

that the anadromous form of coastal cutthroat trout has declined in some tributaries to the Lower

Columbia River because of the effective barrier to migration posed by the presence of C. shasta

in lower reaches of streams (ODFW 1998). Similarly, a combination of anthropogenic effects

such as 1) reduced habitat quality in freshwater, estuarine and nearshore marine environments

(see “Historical abundance, habitat and carrying capacity,” p. 147), 2) size-selective fishing

pressures from coastal cutthroat trout and salmonid fisheries, and 3) interactions between natural

coastal cutthroat trout and hatchery-derived coastal cutthroat trout, steelhead, and coho salmon

have probably caused a shift in the distribution of life-history forms within river basins since

historical times. The incremental increase in risk due to these changes in life-history diversity is

an important consideration in our conservation assessments, but it is difficult to evaluate.

In summary, as discussed earlier (see “ESU Determinations,” p. 125), it is important to

recognize that the observed population- or stream-level variation in life history may be due to a

combination of within-individual flexibility in behavior or physiology as well as to differences

among individuals in their responses to the environment. Understanding the extent of withinindividual and among-individual lability in life-history expression is important for assessing

responses of coastal cutthroat trout populations experiencing threats. If an ESU contains a

diversity of life-history forms represented by different individuals that cannot change from one

form to the other, enough individuals from each life-history form may need to be conserved to
147

ensure persistence of the ESU. Alternatively, if an individual is flexible enough to exhibit a wide

range of life histories, the numbers and types of fish needed to maintain the full expression of

life-history diversity may be less, assuming habitat conditions necessary for the full expression

of life-history types are achieved. Abundances needed to minimize extinction risk depend on the

genetic architecture underlying these life-history traits and the ways in which the life-history

diversity is maintained in populations.

Historical abundance, habitat, and carrying capacity

For coastal cutthroat trout, quantitative estimates of historical abundance generally are

lacking. The relationship of present abundance to present carrying capacity is important for

understanding the health of populations, but the fact that a population is near its current capacity

does not in itself mean that it is healthy. The fact that a population is near capacity implies that

there are limits to the effectiveness of short-term management actions in increasing its

abundance. Another implication is that competition and other interactions between hatchery and

natural fish may be an important consideration for increasing the abundance of naturally

spawning populations because releases of hatchery fish may further increase population density

in a limited habitat.

The relationship of current abundance and habitat capacity to that which existed

historically is an important consideration in evaluating risk. Knowledge of historical population

conditions provides a perspective of the conditions under which present populations 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.

Freshwater habitat conditions—Coastal cutthroat trout spend more time in the freshwater

environment and make more extensive use of this habitat than do most other Pacific salmonids.

The amount of time coastal cutthroat trout spend in fresh water depends on local and regional

environmental conditions and on life-history strategy. Those that are anadromous typically

spend 2-5 years rearing in fresh water before making their initial seaward migration. Generally,

anadromous coastal cutthroat trout spend only brief periods offshore during summer months and

return to estuaries and fresh water by fall or winter (Trotter 1989, Pearcy et al. 1990). Coastal

cutthroat trout use a large variety of habitat types, including large and small river systems with a

diversity of stream gradients, estuaries, sloughs, ponds, and lakes (see “Life-History Stages,”

p. 50). Because these fish make extensive use of river basins throughout all or a large portion of

their life cycle, they are exposed to a variety of potentially adverse conditions associated with

land-use activities.

Fisheries biologists familiar with coastal cutthroat trout believe that degradation and

outright destruction of riverine and estuarine habitat for the subspecies has been widespread

(Gerstung 1997, Hooton 1997, WDFW 1998a). Specific quantitative assessment of habitat

degradation or attempts to evaluate the response of coastal cutthroat trout populations to specific

changes in habitat are rare (Reeves et al. 1991). This lack of biological information has been
148

attributed to two factors: 1) coastal cutthroat trout numbers are generally low relative to other

salmonid species and 2) the dynamics and interrelationships between different life-history forms

and their specific habitat requirements are poorly understood (Reeves et al. 1997, Williams and

Nehlsen 1997).

Degraded habitat has been associated with more than 90% of documented extinctions or

declines of Pacific salmon stocks (Gregory and Bisson 1997). Major land-use activities,

including agriculture, forestry, urban and industrial development, road construction, and mining,

have resulted in the alteration and loss of salmonid habitat and a subsequent loss in salmon

production (Meehan 1991, NRCC 1996). The small streams often used by coastal cutthroat trout

are particularly sensitive to changes in riparian vegetation, and they also are the ones most easily

altered by human activities (Chamberlin et al. 1991). Evidence from two long-term studies, the

Alsea Watershed study in Oregon and the Carnation Creek study in British Columbia, suggests

that coastal cutthroat trout populations may be slow to recover from land-use activities such as

timber harvest. Both of these studies have shown that coastal cutthroat trout numbers declined

considerably after timber harvest and had not returned to their previous levels more than 10 years

later (Moring and Lantz 1975, Hartman and Scrivener 1990, Gregory et al. in press cited in

Reeves et al. 1997). On the other hand, coastal cutthroat trout abundance can increase following

logging in shady headwater streams, presumably because of increased primary productivity

under more intense sunlight (Hall et al. 1978, Murphy and Hall 1981).

The effects of urbanization also may be seen in coastal cutthroat trout population

structure. Scott et al. (1986) compared two streams near Bellevue, Washington: land use in one

basin was primarily urban development, while upland areas in the other basin were largely rural.

The species composition of the fish community in the two drainages was not the same, and one

striking difference was the predominance of early life-history stages of coastal cutthroat trout in

the urbanized creek drainage. However, the difference in fish community structure was not

matched by an expected increase in outmigration rates and decreased growth rates of coastal

cutthroat trout in the urbanized creek relative to the control creek.

Since coho salmon and coastal cutthroat trout habitat use overlaps a great deal, effects of

changes in habitat quantity and quality on coho salmon probably have had similar effects on

coastal cutthroat trout production. Beechie et al. (1994) estimated that since European

settlement, 24-34% of coho salmon rearing habitat has been lost in the Skagit River,

Washington, with most of the habitat lost from side channels and sloughs. Three major causes of

coho salmon habitat loss identified by Beechie et al. (1994) are, in decreasing order of

importance, hydromodification (diking and dredging), blocking culverts, and forest practices.

Similarly, McHenry (1996) estimated that since European settlement, Chimacum Creek,

Washington, (northwestern Puget Sound) has lost 12%, 94% and 97% of its spawning, summerrearing, and winter-rearing habitats for coho salmon, respectively. McHenry (1996) stated that

these habitat losses were due to logging, agricultural clearing, channelization, drainage ditching,

groundwater withdrawal, and lack of woody debris.
149

Only in the last 25-30 years has the importance of riparian vegetation to the aquatic

ecosystem received much attention. Riparian vegetation provides several functions important to

healthy salmonid habitat such as providing cover, maintaining stream temperatures, stabilizing

streambanks and channels, maintaining undercut banks, providing an allochthonous source of

energy, and contributing structural components that influence channel morphology (Murphy and

Meehan 1991). In its assessment of factors leading to steelhead declines, NMFS (1996) reported

that approximately 80-90% of the original riparian habitat in most western states has been

eliminated. In Washington and Oregon, up to 75% and 96% of the original coastal temperate

rainforest has been logged, respectively (Kellogg 1992). Only 10-17% of old-growth forests

reportedly remain in the Douglas fir regions of these two states (Speis and Franklin 1988, Norse

1990). California has reportedly lost 89% of the state’s riparian woodland to various land use

practices (Kreissman 1991). Fisk et al. (1966) stated that over 1,600 km of streams within

California had been damaged or destroyed as fish habitat by 1966.

One of the most important structural components of small streams in coastal watersheds

that is contributed by riparian vegetation is large woody debris (LWD). In most river basins, the

frequency and distribution of LWD has been altered through a number of human activities, many

related to logging (NRCC 1996). The loss of LWD from streams results in subsequent declines

in pool frequency and increases in riffle habitat (Swanson and Lienkaemper 1978, Bisson and

Sedell 1984, Bisson et al. 1987, Gregory et al. 1991). FEMAT (1993) reported that there has

been a 58% reduction in the number of large deep pools on national forest lands within the range

of the northern spotted owl in western and eastern Washington. Similarly, there has been as

much as an 80% reduction in the number of large deep pools in streams on private lands in

coastal Oregon (FEMAT 1993). Overall, the frequency of large pools has decreased by almost

two-thirds between the 1930s and 1992 (FEMAT 1993, Murphy 1995). Reductions in pool

habitat are often related to declines in the number of age-1 and older coastal cutthroat trout

(Bisson and Sedell 1984, Hartman and Scrivener 1990, Fausch and Northcote 1992, Reeves et al.

1993, Connolly 1997).

Descriptions of predevelopment conditions of rivers in Washington and Oregon that had

abundant salmonid populations suggest that even big rivers had large amounts of instream LWD,

which contributed significantly to trapping sediments and nutrients, impounding water, and

creating many side channels and sloughs (Sedell and Luchessa 1982, Sedell and Froggatt 1984).

Stream cleaning of LWD for navigation, flood control, and transport of logs occurred from the

mid-1800s through the mid-1970s in many areas. In addition, past logging practices sometimes

left excessive accumulations of debris in small streams that adversely affected fish production

(Narver 1971, Brown 1974). Debris in streams was often viewed as something that would either

impede or block fish passage and destroy channels by scour during storm-induced logjam

failures. Until about 25 years ago, up to 90% of the funds for fish-habitat enhancement went for

removal of wood debris in streams (Sedell and Luchessa 1982).

Beavers also had a key role in creating and maintaining many of these off-channel

habitats. Beaver dams obstructed and redirected channel flows, flooded side-channels, and

created large depositional areas for fine sediment storage (NRCC 1996). The use of these
150

sloughs and other off-channel habitats by coastal cutthroat trout was probably extensive, as

suggested by their present use of these freshwater habitats for overwintering and feeding

(Cederholm and Scarlett 1982, Hartman and Brown 1987, Reimchen 1990, Garrett 1998).

Some of the most productive salmonid habitat has been lost by blockages to migration.

The most recognized barriers to migration are dams, but many smaller barriers exist as well.

Blocked or improperly maintained culverts present obstacles to coastal cutthroat trout migration

and seriously reduce the amount of habitat available for spawning and rearing. In Washington,

an estimated 2,400 blocked culverts have eliminated more than 3,000 miles of stream habitat

(WDFW 1995). Studies by Washington Trout (unpubl. data cited in White 1997) suggested the

problem may be underestimated and that 80% of all culverts in the Puget Sound basin may block

fish passage. Furthermore, culverts designed to allow the passage of adult salmon may create

water velocities that exceed the swimming ability of juveniles except during periods of low flow

(NRCC 1996). The impact of migrational barriers on coastal cutthroat trout production may be

particularly severe since the majority of their life cycle is spent in fresh water, and they depend

upon a variety of habitats for every life-history stage. Another potential migration barrier

identified by NRCC (1996) is unscreened water diversions that may entrain downstream migrants.

The declines in the number of returning Pacific salmon and the nutrients they contribute

to streams also may have placed additional limitations on coastal cutthroat trout production in

fresh water. Consumption of carcasses and eggs by coastal cutthroat trout may have been

particularly important in nutrient-poor headwater streams (Bilby et al. 1996), where coastal

cutthroat trout spawning and early rearing typically occurs. The decreased availability of this

nutrient-rich food source may have contributed to a reduction in growth and overwintering

survival of coastal cutthroat trout juveniles.

Conditions of freshwater habitats in which coastal cutthroat trout live today are very

different from historical conditions. The 1998 “Washington State Coastal Cutthroat Stock

Inventory” (WDFW 1998a) identified numerous land-use practices or habitat factors that have

had a detrimental impact on coastal cutthroat trout habitat for 20 recognized coastal cutthroat

trout stock complexes in Washington. Dominant land-use practices and habitat factors cited in

this report include logging practices, road building, passage obstructions (e.g., dams and

blocking culverts), water diversions, mining, livestock grazing, harvesting, and poaching. In

Oregon, activities identified as impacting critical coastal cutthroat trout habitat are logging,

grazing, road building, and land-development activities that impact water quality and flows

(Kostow 1995). In most cases, separating the relative impact of one land-use activity from

another is difficult since most salmon populations are subject to the cumulative effects of

multiple land uses (Palmisano et al. 1993). Generally, the changes from each land use activity

affect fish habitat similarly, despite differences in the activities themselves (Meehan 1991).

Development and land-modification activities can act concurrently or sequentially to limit

coastal cutthroat trout population size or growth during different life-history phases. In

Washington, Oregon, and Northern California, the cumulative effect of these activities has led to

large reductions in spawning habitat and in summer- and winter-rearing habitat for coastal

cutthroat trout (Gerstung 1997, Hooton 1997, WDFW 1998a).
151

Estuaries—The extensive use of estuaries by coastal cutthroat trout makes them more

susceptible to changes in the productivity of that environment than many other Pacific salmonid

species (Giger 1972, Pearcy 1997). Although little is known about the habitat requirements or

preferences of coastal cutthroat trout in estuarine habitat, estuaries are believed to provide

important feeding opportunities and overwintering refuge to juveniles and adults (see “Life

History,” p. 38).

Estuaries historically contained large amounts of woody debris (Gonor et al. 1988).

Giger (1972) suggested that temperature may be the most influential factor in determining the

migration and distribution of coastal cutthroat trout in estuaries. Declines in woody debris in

estuaries have likely resulted in detrimental effects on coastal cutthroat trout due to a resulting

temperature increase and reduction in refuge sites. Coastal cutthroat trout are known to use such

areas for protection from intense sunlight and high flows (Maser and Sedell 1994).

The loss of coastal wetlands to urban or agricultural development also would directly

reduce the productivity of cutthroat populations. The primary losses in estuarine habitat are

attributed to the ditching, draining, diking, and filling associated with agricultural and urban

development. The degree of habitat lost in the estuarine or nearshore marine environment is

difficult to quantify as there are few historical studies that include useful baseline information

(Levings and Thom 1994). One of the first attempts to inventory estuarine areas in the Puget

Sound region was a U.S. Department of Agriculture survey by Nesbit (1885). He surveyed

267 km2

 of tidal marshes and swamps in nine counties bordering Puget Sound, and reported

approximately 320 km of dikes enclosing 4.1 km2 of marsh. In Skagit and Stillaguamish river

areas, Nesbit (1885) found that tidelands covered 520 km2 and extended 20 km inland from the

present shoreline. Nesbit found that tide marshes across the Puget Sound region in the 1880s

greatly exceeded tide flats in area and that nontidal freshwater marsh area exceeded that of tide

marsh by three to four times. In the 1980s, Boule et al. (1983) estimated Puget Sound had only

54.6 km2 of intertidal marine or vegetated habitat in the entire basin and that this represented

58% of the state’s total estuarine wetlands.

More recently, attempts have been made to quantify changes in estuaries within the range

of coastal cutthroat trout. Bortelson et al. (1980) estimated historical changes in natural habitats

in eleven major estuaries, where they found an average decrease in estimated area of subaerial

wetland of 64% (SD 35%). Estimated wetland losses in the Puyallup River drainage were 100%,

Duwamish River Basin losses were 99%, and Samish River Basin losses were 96%. Only in the

Nooksack River drainage did wetland area increase, and that was only by 0.2%. Simenstad et al.

(1982) used similar methods to calculate losses of wetland area in Grays Harbor and found a

decrease of 30.3%. Hutchinson et al. (1989) estimated change in area of intertidal marshes

around the Strait of Georgia and Puget Sound from the time of European settlement to the

present. They found overall losses of 18% around the Strait of Georgia and 58% around Puget

Sound. Dahl (1990) reported that over 33% of total (freshwater and estuarine) wetland area in

Washington and Oregon has been lost and that much of the remaining wetland habitat is

degraded. Levings and Thom (1994) also estimated a loss of at least 76% in marsh/riparian

habitat types in eleven major deltas in Puget Sound (from 732 km2 prior to the mid-1800s to
152

176.1 km2 in the early 1990s). Dahl (1990) reported that California has lost 94% of its wetlands.

Similar reductions from historical times have been reported in Washington and Oregon wetlands:

70% loss in Puget Sound, 50% in Willapa Bay, and 85% in Coos Bay (Refalt 1985).

Most reviews of estuarine modification have focused on major estuaries and at river

mouths near high-intensity industrial and urban development, but this development affects only

2% of the approximately 3,620 km of Puget Sound shoreline (Canning 1997). Perhaps a better

estimate of overall historical changes in intertidal and nearshore habitats are inventories of

shoreline armoring (e.g., construction of rock, concrete, and timber bulkheads or retaining walls),

as these habitat modifications occur primarily with residential development in relatively rural

areas (Shipman 1997). Armoring has a cumulative environmental impact that eventually results

in loss of riparian vegetation, burial of the upper beach areas, altered wave interaction with the

shoreline, and obstruction of sediment movement (Shipman 1997). Morrison et al. (1993) found

a more than 100% increase in the length of shoreline armored from 1977 to 1993 in Thurston

County, Washington. Kathey (1994) inventoried armoring along Bainbridge Island in Puget

Sound and found that 42-67% of the entire shoreline was armored. Estuarine habitat quality also

has been negatively affected by alteration of river hydrographs due to human activities. Water

withdrawals, blockages, and diversions have reduced the total amount and the timing of peaks in

freshwater inflow into estuaries throughout the range of coastal cutthroat trout. These shifts in

the magnitude and timing of freshwater flows have a wide range of potentially deleterious effects

ranging from decreases in estuarine primary and secondary productivity, increases in the stress

on salmonids waiting to migrate upriver to spawning and feeding habitat, and seasonal blockages

to outmigrating salmonids during summer months with extremely low flows.

Marine habitat—Although marine migrations of coastal cutthroat trout are generally limited to

nearshore habitats, these areas can be influenced by general ocean productivity. The productivity

of various ocean regions has been correlated with the degree of wind-driven upwelling (Bakun

1973, 1975). Upwelling brings cold nutrient-rich waters to the surface, resulting in an increase

in plankton and ultimately salmonid production (Beamish and Bouillon 1993). El Niño events

suppress coastal upwelling off the Washington, Oregon, and California coasts and tend to bring

warmer water and warm-water species northward (McLain 1984). The Southern Oscillation

Index (an index of El Niños) reveals that these warm-water events have been occurring well

above average in frequency and intensity since 1976. The Pacific Northwest Index (an index of

precipitation and sea temperatures in Washington) also reveals that the period following 1976

was warm and dry compared to the cool-wet period from 1945 to 1975 (Ebbesmeyer and

Strickland 1995).

These long-term climate fluctuations have resulted in periodically unfavorable ocean and

nearshore conditions for salmonids in California, Oregon, and Washington. As discussed in the

“Life History” section (p. 38), coastal cutthroat trout display a variety of life-history strategies

that may allow them to use more productive parts of the marine/freshwater environment and

avoid unfavorable ones. As the evolution of these life-history strategies has, in part, been in

response to long-term geographic and seasonal differences in marine productivity and estuarine
153

availability, these conditions may be one cause of changes in overall coastal cutthroat trout

abundance or in the relative abundance of different life-history types (Pearcy 1997; W. Pearcy16 ).

Trends in abundance

Short- and long-term trends in abundance are a primary indicator of risk in salmonid

populations. Trends may be calculated from a variety of quantitative data, including dam or weir

counts, stream surveys, and catch data. Regular sampling has not been conducted for many

coastal cutthroat trout populations, and data series are quite short for many of those populations

for which sampling has been conducted. When data series are lacking, general trends may be

inferred by comparing historical and recent abundance estimates, or by considering trends in

habitat quantity or condition.

The role of hatcheries and other forms of artificial propagation (in the form of hatcheries)

for Pacific salmonids requires careful consideration in ESA evaluations. Artificial propagation

has implications for evaluating both production trends and the genetic/ecological integrity of

populations. Waples (1991a,b) and Hard et al. (1992) discussed the role of artificial propagation

in ESU determination, emphasizing the need to focus on natural production in the threatened or

endangered status determination. Because of the ESA emphasis on ecosystem conservation, this

analysis focuses on naturally reproducing fish. An important question in the threshold

determination is thus: Is natural production sufficient to maintain the population without the

constant infusion of artificially produced fish? A full answer to this question is difficult without

extensive studies of relative production and interactions between hatchery and natural fish.

When such information is lacking, the presence of hatchery fish in natural populations leads to

substantial uncertainty in evaluating the status of the natural population. Hatchery production of

coastal cutthroat trout in the contiguous United States has been relatively minor compared with

natural production and with other species of Pacific salmonids. In most cases, therefore, there

are not large numbers of naturally spawning hatchery fish to complicate the issue of

sustainability of natural populations.

Factors causing variability in abundance

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 number of 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. 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?

16

W. Pearcy, Oregon State University, Corvallis, OR 97333. Pers. commun. to O. Johnson. Oct. 1998.
154

Variations in the freshwater and marine environments are thought to be a primary factor

driving fluctuations in salmonid run-size and escapement (Pearcy 1992, Beamish and Bouillon

1993, Lawson 1993). Artificial propagation can also contribute to fluctuations in natural

abundance as well as having less obvious genetic and ecological effects. These factors are

assessed below and have probably made some populations less resilient to a variety of poor

conditions, but these effects are not easily quantified.

Oceanic and climatic conditions are also known to have changed recently in the Pacific

Northwest. Most Pacific salmonids south of British Columbia have been affected by changes in

ocean production that occurred during the 1970s (Pearcy 1992, Lawson 1993). Changes in

productivity in the nearshore marine environment have been implicated in declines in chinook

and coho salmon abundance and productivity. Coastal cutthroat trout tend to migrate closer to

shore than chinook and coho salmon, and might have been affected more significantly by

changes in the nearshore environment. However, the migration patterns for coastal cutthroat

trout are still poorly understood. At this time, we do not know whether these climate conditions

represent a long-term shift in conditions that will continue affecting salmonids into the future, or

short-term environmental fluctuations that can be expected to reverse in the near future.

Threats to genetic integrity

Artificial propagation of coastal cutthroat trout—In addition to being a factor in evaluating

natural replacement rates, artificial propagation can have a substantial influence on genetic/

ecological integrity of natural salmonid populations. This influence can be expressed in several

ways. First, stock transfers that result in interbreeding of hatchery and natural fish can lead to

loss of fitness within and loss of diversity among populations. The latter may be important in

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 (Fagen and Smoker 1989, Riggs 1990). Ricker (1972) and Taylor (1991)

summarized some of the evidence for local adaptations in Pacific salmonids that may be at risk

from stock transfers.

Second, because a successful salmonid hatchery dramatically changes the mortality

profile of a population, some level of genetic change relative to the native, naturally produced

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, adult

spawners can still 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 hatchery fish that are not adapted to local conditions are

successful in spawning with natural fish, production may be diverted from more productive

natural crosses. The presence of large numbers of hatchery juveniles or adults may also alter the

selective regime faced by natural fish.
155

Although past hatchery practices may have substantially influenced some coastal

cutthroat trout populations, the relatively small magnitude of most current hatchery programs

suggests that ongoing hatchery practices are unlikely to threaten the genetic integrity of most

coastal cutthroat trout populations considered in this review. Large programs have taken place in

the Lower Columbia River Basin and in a few streams along the Oregon coast, and genetic

concerns in these areas are proportionally greater. It is difficult to directly assess the influence

that population transfers of hatchery coastal cutthroat trout have had on natural populations

because, in most cases, information is lacking. However, the results from a recent genetic

analysis suggest that natural and hatchery coastal cutthroat trout have been interacting in the

Coquille River Basin (NMFS et al., unpubl. data). Coastal cutthroat trout in several streams in

the Coquille River drainage are genetically most similar to coastal cutthroat trout in the Alsea

River Hatchery broodstock. Whether this genetic similarity is due to introgression resulting from

hatchery-natural matings or due to displacement of native coastal cutthroat trout by straying

hatchery fish cannot be determined from the data.

For populations with low abundance (either natural or hatchery), small-population effects

(inbreeding, genetic drift) also can be important concerns for genetic integrity. Inbreeding and

outbreeding depression 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, Hard and Hershberger 1995). Other studies (e.g., Simon et al. 1986, Withler 1988,

Waples and Teel 1990) have shown that hatchery practices commonly used in the past with

anadromous Pacific salmonids have the potential to affect genetic integrity. In addition,

Allendorf and Phelps (1980) detected a significant reduction in genetic variation at isozyme loci

in a hatchery stock of westslope cutthroat trout when compared to the natural population from

which it was derived. The reduction in genetic variation took the form of a lower proportion of

polymorphic loci, average number of alleles per locus, and in the average heterozygosity per

individual. Small-population effects (such as genetic drift, mutation, and introgression) may

influence coastal cutthroat trout in many of the streams throughout their range.

Hybridization between coastal cutthroat trout and O. mykiss—As mentioned earlier (see

“Hybridization between cutthroat trout and O. mykiss,” p. 76), coastal cutthroat trout hybridize

with steelhead and rainbow trout. Risks to coastal cutthroat trout populations from hybridization

with O. mykiss include reduction in reproductive success of coastal cutthroat trout producing

hybrid offspring. Production of hybrid offspring can reduce fitness of the parental species

simply by decreasing the number of parental genes passed on to the next generation; this direct

loss in fitness is most rapid when hybrid offspring fitness is lower than that of pure coastal

cutthroat trout offspring. Indirect fitness losses can result from hybridization if hybrid offspring

are superior competitors (even if only in a particular life stage) when interacting with pure

coastal cutthroat trout offspring. In addition, introgression of O. mykiss alleles into O. c. clarki

genomes can contribute to risk for coastal cutthroat trout populations. The concomitant loss or

alteration of “pure” coastal cutthroat trout alleles (and resulting phenotypic traits) can lead to

reduced fitness if introgressed alleles alter traits contributing to local adaptation in coastal

cutthroat trout. The important question to address is what the fitness consequences of hybrids

are to coastal cutthroat trout in their natural environment. To date, studies on the relative
156

selective advantages or disadvantages of coastal cutthroat trout × O. mykiss hybrids have been

conducted only in laboratory environments. Generally, hybrids have been shown to be

intermediate in performance compared to either parental species, but some hybrids exhibited

early life-history traits that were expected to be selected against under natural conditions

(Hawkins 1997; see also “Hybridization between cutthroat trout and O. mykiss,” p. 76). In

addition, based on allozyme samples of juvenile and adult coastal cutthroat trout, Campton and

Utter (1985) and Neillands (1990) hypothesized that selection against hybrids in anadromous

populations might be occurring. Furthermore, biologists familiar with coastal cutthroat trout

have noted that hybrids are detected more frequently in juvenile samples than in adults,

suggesting that there are negative-fitness consequences associated with coastal cutthroat trout ×

O. mykiss hybridization events. On the other hand, some hybrids detected with genetic markers

appear to be offspring of backcrossed individuals, suggesting that selection against F1 hybrids is

not universally strong.

The extent of hybridization between coastal cutthroat trout and O. mykiss and the

environmental characteristics with which it is correlated are not well understood. Identifying

hybrids is not straightforward without multiple genetic markers. In addition, historical (i.e.,

background or “natural”) levels of coastal cutthroat trout × O. mykiss hybridization have not been

distinguished from levels of present-day hybridization. To fully address the hybridization risk,

we need to know how human activities may have affected both the frequency of coastal cutthroat

trout × O. mykiss hybridization events and the fitness consequences of such hybridizations. For

example, human actions can alter the relative abundance of coastal cutthroat trout and O. mykiss

or increase the incidence of sympatry. In addition, it is important to ask whether recent changes

in physical or biotic environmental conditions have resulted in significant changes in the survival

of coastal cutthroat trout × O. mykiss hybrid offspring. These possibilities remain important for

evaluating the risks to coastal cutthroat trout from hybridization with O. mykiss.

Harvest

Coastal cutthroat trout are not targeted in commercial fisheries and, in many areas, the

only catch of coastal cutthroat trout is incidental in recreational fisheries for other species of

salmonids. Because of harvest restrictions on naturally produced coastal cutthroat trout in many

areas and the lack of targeted fisheries, direct mortality due to fishing pressure is thought to be

relatively low, at least in recent years (Hooton 1997, Gerstung 1998, WDFW 1998a).

Nevertheless, the catch of coastal cutthroat trout in recreational fisheries targeting the species

directly and in fisheries aimed at Pacific salmon was probably a significant source of mortality in

the past. Cutthroat trout are especially susceptible to fishing pressure because of their high

“catchability” throughout their life history (Gresswell and Harding 1997). In addition, fishing

regulations establishing size and bag limits are relatively recent, and biologists familiar with

coastal cutthroat trout feel that in some areas their abundance has begun to increase only recently

due to imposition of these more restrictive fishing limits (WDFW 1998c, Dunham 1998). In

Washington, recent fishing regulations require the release of all coastal cutthroat trout, except

adipose clipped hatchery fish, in Puget Sound, Hood Canal, the mainstem of the Chehalis,

Toutle, Coweeman, Cowlitz, and Grays rivers, and in several smaller streams in the Lower

Columbia River Basin. Bag and size limits on recreational catch of coastal cutthroat trout are in
157

effect in the Strait of Juan de Fuca, in coastal streams, and in all Lower Columbia River Basin

streams not subject to catch and release regulations (WDFW 1998a). Hatchery coastal cutthroat

trout fisheries are still fairly active in the Lower Columbia River Basin. In Oregon, catch and

release regulations recently were imposed in the Rogue, Hood, and Lower Columbia rivers and

in portions of the Willamette and Sandy rivers. More restrictive bag and size limits were

imposed on other Oregon streams in 1995, and in 1996, harvest of coastal cutthroat trout in the

Umpqua River Basin was stopped in response to the federal listing under the ESA (Hooton 1997,

ODFW 1998). More restrictive bag and size limits were placed on coastal cutthroat trout in

Humboldt Bay and in Stone Lagoon in California (Gerstung 1997). Active coastal cutthroat trout

recreational fisheries still exist in the Smith and Little rivers and in coastal lagoons in northern

California (Gerstung17 ). However, recently imposed harvest restrictions by CDFG and CFGC

aimed at protecting “wild trout” in northern California should have a positive (but not yet

quantified) effect on coastal cutthroat trout (Bryant 1998).

Other risk factors

Other risk factors typically considered for salmonid populations include disease

prevalence, predation, and changes in life-history characteristics such as spawning age or size.

With the exception of reduction in the percentage of repeat spawners in some areas and evidence

for predation by marine mammals on hatchery coastal cutthroat trout in the Lower Columbia

River (WDFW 1998a), there is no clear evidence for general effects of other risk factors on

coastal cutthroat trout in Washington, Oregon, and California. Some of these factors may be

important for individual populations or ESUs, as noted in “Discussion of and Conclusions about

ESU Determinations” (p. 120).

Coastal cutthroat trout populations can also suffer as a result of ecological interactions

with competitors and predators. As discussed earlier (see “Life History” section, p. 38) coastal

cutthroat trout compete with other species of Pacific salmonids as juveniles for feeding and

rearing sites and as adults for spawning sites (Hartman and Gill 1968, Glova and Mason 1977,

Glova 1987). Both inter- and intraspecific competition can occur in freshwater habitats during

early rearing, and in estuarine habitats after smoltification has occurred. Adult coastal cutthroat

trout can experience inter- and intraspecific competition in nearshore marine, estuarine, and

freshwater habitats. Natural levels of competition can be disrupted by changes in the relative

abundance of the species with which coastal cutthroat trout interact. These changes in relative

abundance can be due to natural shifts in environmental conditions or human-induced changes in

interacting species. For example, estuaries may be “overgrazed” when large numbers of

salmonid juveniles enter the estuary at the same time (Reimers 1973, Healey 1991). Also,

coastal cutthroat trout released from hatcheries often “residualize,” increasing the pressure on

freshwater-habitat rearing capacity for natural coastal cutthroat trout (Royal 1972). The extent to

which such residualized fish decrease abundance of natural coastal cutthroat trout has not been

quantified.

17

E. Gerstung, CDFG, 1416-9th St., Sacramento, CA 95814. Pers. commun. to M. Ruckelshaus. Sept.

1998.
158

 A major source of human-caused change in the relative abundance of competitors is

releases of hatchery-reared salmonids into coastal cutthroat trout habitats. For example, coastal

cutthroat trout have been shown to compete with coho salmon during the juvenile-rearing phase,

and coho salmon hatchery fry are planted into a number of coastal cutthroat trout streams. The

increased competition from hatchery coho salmon may be a prominent risk factor for juvenile

coastal cutthroat trout (Tripp and McCart 1983, Peters et al. 1996a, but see Peters et al. 1996b).

In support of this possibility, a majority of those streams in Washington with continuing releases

of hatchery coho salmon fry after 1986 also show declining trends in coastal cutthroat trout

abundance (Fig. 34). Conversely, those streams without coho fry plants had mixed trends in

abundance over the same time period. We were unable to do a similar graphical analysis with

Oregon streams because we did not have data on coho fry releases and coastal cutthroat trout

abundance for the same streams at appropriately small geographic scales. The potential also

exists for large-scale hatchery releases of fry and fingerling salmon to overwhelm the production

capacity of estuaries (Lichatowich and McIntyre 1987). Finally, hatchery and natural adults with

sympatric spawning distributions can compete inter- and intraspecifically for redd sites and, as

habitat conditions deteriorate in a number of streams, the opportunities for increased competition

at this life-history stage also may be increasing.

 Predation on coastal cutthroat trout also can limit population abundances. Dramatic

population increases in sea lions and harbor seals have occurred in the Columbia River, due in

part to their protection under the Marine Mammal Protection Act of 1972 (WDFW 1998a).

Hatchery coastal cutthroat trout returning to the Beaver Creek Hatchery in the Lower Columbia

River are scored for marine mammal marks. The percentage of returning adults with scars from

marine mammals has ranged from 0 to 16% (mean = 7%) since 1982 (WDFW 1998a). It is not

known whether these exceed historical predation rates, but these indicators of predator-prey

encounter rates suggest that in some years coastal cutthroat trout mortality due to marine

mammal predation may be high.

Biological Information by ESU

Puget Sound ESU

The BRT did not receive any estimates of adult coastal cutthroat trout population sizes

for streams in the Puget Sound region except for a rough estimate of 13,000 spawners returning

to the Skagit River Basin in 1997 (Kraemer unpubl. data). In addition, the percentage of mature

fish that are repeat spawners has declined in the Stillaguamish (from 12% in 1991 to 5.4% in

1997) and Snohomish (from 12.4% in 1996 to 8.2 % in 1997) rivers (Kraemer unpubl. data).

Although these data were collected over very short time periods, the lost opportunity for multiple

spawning events by older (and larger, more fecund) fish should have a negative impact on

population abundance, depending on total population size.
159
160

Indices of coastal cutthroat trout abundance in a number of Lake Washington tributaries

were estimated in 1996 (Ludwa et al. 1997). The numbers of coastal cutthroat trout per 50 m of

stream ranged from 8 in McAleer Creek to almost 30 in Lyon Creek. Coastal cutthroat trout

numbers in Kelsey Creek were 4-5 fish per 50 m of stream in 1979 (Scott et al. 1986) and

increased to 23 fish/50 m in 1996 (Ludwa et al. 1997).

The only other abundance information available to the BRT for adult runs was a data set

from the Oyster River in British Columbia. The Oyster River is on the eastern side of Vancouver

Island, and represents one of the largest anadromous cutthroat trout runs in that area (BE and

LGL 1995). Numbers of total adults (natural + hatchery) in the lower 8 km of the river ranged

from 12-84 fish, of which 5-48 were estimated to be naturally produced fish (Fig. 35).

Abundances in recent years have been highly variable, but the general trend has been positive

since catch and release of nonhatchery coastal cutthroat trout became mandatory in British

Columbia waters in 1985.

Reduction in habitat capacity for coastal cutthroat trout in the Puget Sound region has

been widespread (WDFW 1998a; see also “Historical abundance, habitat, and carrying capacity”

section, p. 147). In particular, numerous small streams were channelized or otherwise modified

in the late 1800s and early 1900s for agricultural development. Historical records do not exist

for coastal cutthroat trout in many lowland streams that were most likely very productive habitats

for these fish. Estimates that 20-90% of salmonid habitat has been lost in the Puget Sound

region (see “Historical abundance, habitat, and carrying capacity” section, p. 147) suggest that

reduction in habitat capacity for coastal cutthroat trout is a critical, but not yet quantified, risk

factor for this ESU.

All other quantitative data the BRT received for this ESU were useful only for evaluating

trends in adult and smolt population sizes (Table 8, Fig. 36). Trends were mixed in the number

of adults caught per hour by WDFW fisheries biologists in three northern Puget Sound rivers

over the past 2-7 years (WDFW 1998a) (Fig. 37A). The Stillaguamish and Snohomish rivers

showed increasing trends in catch per unit effort (CPUE), and the CPUE in the Skagit River has

been declining over the past 4 years. The extremely short time periods covered by these data

(especially for the Snohomish River sampling, conducted only since 1996) makes interpretation

of the significance of the trends difficult. In addition, WDFW believes that much of the variation

among years in adults caught was due to variable fishing conditions (WDFW 1998c).

In the Skagit River, data are available from 1990 to the present indicating the numbers of

juvenile and adult coastal cutthroat trout caught in mainstem traps designed to estimate coho

salmon production (Seiler et al. 1998). Both scoop and screw trap data are available for

downstream migrants (1990-97 for scoop traps and 1993-97 for screw traps) (Table 8) and

upstream migrants (1995-97 for scoop traps and 1996-97 for screw traps). These data are

considered indices of coastal cutthroat trout abundance because trap efficiencies were estimated

only for coho salmon and because the proportion of the coastal cutthroat trout population trapped

is not known. Numbers of upstream and downstream migrants are likely to be underestimated

because of the relatively narrow time periods during which traps were in place each year (i.e., the
161
162
163
164
165
166
167
168

traps were installed during periods of known coho immigration and emigration, which occur over

a more predictable and narrower window of time than do coastal cutthroat trout migration

patterns) (Seiler18). Nevertheless, the overlap in emigration times for coho salmon and coastal

cutthroat trout can be very high in some streams (Cederholm and Scarlett 1982), so underestimation for coastal cutthroat trout numbers may not be high in all instances. Trends in coastal

cutthroat trout downstream migrant abundance from 1990 to present have declined by 12-30%

per year; in contrast, upstream migrants increased dramatically (3-198%) over the past 3 years.

It is difficult to interpret the significance of the upstream migrant data because of the high

variability and short time period over which these fish have been sampled in this river basin.

Additional trend information is available for adult coastal cutthroat trout in the Deschutes

River in southern Puget Sound. Immigrant coastal cutthroat trout adults trapped in a weir

designed to estimate coho abundance have been counted since 1981, and their numbers have

been increasing by 10% over the long term and by 26% over the most recent 5 years (Topping

unpubl. data) (Table 8, Fig. 37B). Again, the absolute abundance of individuals should be

considered to be an index number because the trap efficiency for coastal cutthroat trout is not

known.

Data from traps for southern Puget Sound outmigrant smolts are available from the late

1970s to the late 1980s (WDFW 1998a) (Fig. 37C). Data are from Wildcat Creek (Dyes Inlet),

Perkins Creek (Eld Inlet), and Mill Creek (Hammersley Inlet). Trends in smolt numbers in

Wildcat and Mill creeks during this period were slightly declining (a 2-5% decrease in

abundance), while Perkins Creek smolt numbers increased by 15% over roughly the same time

period. No information was available to the BRT indicating the current status of coastal

cutthroat trout smolts in these creeks.

 Smolt abundance data from the late 1970s to the present were available from a number of

streams in eastern Hood Canal (WDFW 1998a) (Fig. 38). The trends in smolt abundance were

mixed, ranging from a 6.6% decline per year over 15 years to an almost 30% increase over 4

years. Smolts in the Skokomish River declined by over 68% per year from 1986-1989 (PNPTC

1994). No information about present trends in smolt abundance in the Skokomish River was

available to the BRT. Upstream weir counts for one of the creeks draining into Hood Canal, Big

Beef Creek, were 190 coastal cutthroat trout in 1993-94 and 86 coastal cutthroat trout in 1994-95

(Seiler et al. 1995). Additional data from Snow and Salmon Creeks in eastern Hood Canal have

been submitted to NMFS but were not available for BRT deliberations (see Table C-1 in

Appendix C).

 No anadromous coastal cutthroat trout are presently released from hatcheries into the

Puget Sound ESU. Historical information on the numbers and origin of hatchery coastal

cutthroat trout released into streams in this region (see “Artificial Propagation,” p. 113) provides

an indication of the potential risks due to interactions with hatchery coastal cutthroat trout. For

18 D. Seiler, WDFW, P.O. Box 43151, Olympia, WA 98504. Pers. commun. to M. Ruckelshaus. Sept.

1998.
169
170

example, as discussed in the section on artificial propagation, the overlap in spawning times of

the Lake Whatcom/Tokul Creek coastal cutthroat trout broodstock and native coastal cutthroat

trout in Lake Washington suggest that the potential existed for interbreeding between native and

hatchery fish within this ESU. In addition, WDFW considers several of the streams in northern

Puget Sound to be of mixed origin (e.g., the Stillaguamish, Snohomish, and Nooksack rivers)

and composite production (Nooksack River), indicating that hatchery fish of nonnative origin

could potentially contribute to naturally spawning populations, depending on the release

locations of hatchery coastal cutthroat trout relative to spawning grounds of native fish (WDFW

1998a, c). Hatchery coastal cutthroat trout from the Beaver Creek Hatchery in the Lower

Columbia River were reported to stray when released in Hood Canal streams (Hisata 1973; see

“Artificial Propagation,” p. 113). On the other hand, releases of hatchery sea-run cutthroat trout

were stopped in 1985 in northern Puget Sound streams, and in 1994 in southern Puget Sound and

Hood Canal (WDFW 1998a). Also, some hatchery broodstocks from the Lower Columbia River

released into Puget Sound did not succeed in enhancing harvest (see “Artificial Propagation,” p.

113), suggesting that at least some coastal cutthroat trout of hatchery origin were not adapted to

environmental conditions in Puget Sound. Finally, releases of hatchery coho salmon and

steelhead continue to occur in Puget Sound and Hood Canal (WDFW 1998a).

Harvest of coastal cutthroat trout in the Puget Sound region was probably significant in

the past, but most biologists familiar with salmonids in this area feel that direct and indirect

fishing pressure on coastal cutthroat trout in this ESU has probably declined (WDFW 1998c).

One possible exception is the continued incidental catch of coastal cutthroat trout in local gillnet

fisheries targeting Pacific salmon (WDFW 1998c). Drought conditions in the mid-1980s and

early 1990s also probably severely stressed coastal cutthroat trout in this region (WDFW 1998c).

Olympic Peninsula ESU

Very few quantitative data were available to the BRT for the Olympic Peninsula ESU,

and the vast majority of the information came from downstream migrant traps on several

tributaries to the Clearwater River, which is a tributary of the Queets River (Garrett 1998)

(Table 8, Figs. 36, 39a, and 39b). Downstream migrant adult and juvenile coastal cutthroat trout

have been sampled in the Clearwater River basin with a scoop trap in the mainstem and with

weirs in the tributaries; trap efficiencies for coastal cutthroat trout caught in these traps are not

known. The data are presented as the numbers of downstream migrants trapped per number of

days the trap was operated each year. Downstream migrants in the mainstem Clearwater River

have been sampled with a scoop trap since 1981, and their numbers are showing a 13% decline

per year. The tributary data span 8-20 years, and they represent downstream migrant smolts and

adults in streams and ponds used as feeding and overwintering habitat. The trends in abundance

are mixed—some are relatively stable over the sampling period, others show declines, and

coastal cutthroat trout numbers in one pond have been steadily increasing since 1988.

The other abundance data for coastal cutthroat trout in the Olympic Peninsula ESU were

from the Lake Dickey screw trap, which captures downstream migrants (Seiler et al. 1997). This

trap is designed to estimate coho salmon production, and the trap efficiency for coastal cutthroat
171
172
173

trout is not known. The numbers of coastal cutthroat trout caught in the trap from 1992-94 were

285, 138, and 269, respectively. WDFW reported high coastal cutthroat trout habitat quality in

the Quinault River Basin (WDFW 1998a). In addition, the Point No Point Treaty Council

coordinated sampling of downstream migrants on the Hoko River from 1986-89 (Table 8,

Fig. 40) (PNPTC 1994). Weirs trapped downstream migrants at RKm 10 on the mainstem Hoko

River and on the Little Hoko River at its mouth. The numbers of downstream migrants were

highly variable–they increased by almost 32% per year over the time period sampled, but the

high variance in the numbers of fish means this trend is not statistically significant.

Finally, WDFW has 1998 downstream migrant data for coastal cutthroat trout as a result

of new sampling of coho salmon in a number of streams along the Strait of Juan de Fuca. The

traps are designed to estimate coho smolt production and so were in place from April to June.

Trap efficiencies for coastal cutthroat trout are not known; the proportion of the total coastal

cutthroat trout population trapped in the downstream migrant traps also is not known. WDFW

believes that most of the coastal cutthroat trout trapped were smolts, but a few larger fish also

were caught. In 1998, the numbers of outmigrating coastal cutthroat trout in these creeks ranged

from 55 in Valley Creek to 756 in Mattrotti Creek (Hanratty unpubl. data). WDFW plans to

continue sampling in these streams, which should provide good indices of smolt production for

coastal cutthroat trout in this area.

No information on the percentage of hatchery coastal cutthroat trout in natural spawning

escapements in the Olympic Peninsula ESU was available to the BRT. There is some

information on the numbers and origin of hatchery coastal cutthroat trout released into streams in

this region (see “Artificial Propagation,” p. 113), which provides an indication of the potential

risks due to interactions with hatchery coastal cutthroat trout. In addition, releases of hatchery

coho salmon and steelhead continue to occur in a few Olympic Peninsula streams.

Southwestern Washington/Columbia River ESU

Information on coastal cutthroat trout abundance was available from a few streams in the

southwestern Washington portion of the geographic region encompassing this ESU (Table 8, Fig.

36). The number of adults trapped in the west branch of the Hoquiam River has ranged from 25

to 68 over the past 10 years (most recent 5-year geometric mean = 33 fish) (WDFW 1998a).

Abundance in the Hoquiam River has declined by 5% per year over the past 10 years (Fig. 41A).

Downstream migrants in Stevens Creek, a tributary to the Humptulips River, have been declining

by 15% per year since 1982 (Table 8, Fig. 41C). The numbers of coastal cutthroat trout counted

in the Stevens Creek trap should be considered an index count because the trap efficiency and the

proportion of total outmigrants trapped is not known for this weir, which is designed to estimate

coho salmon production. WDFW biologists who run the trap believe that most of the

outmigrating coastal cutthroat trout caught in the trap were smolts, but that a few larger fish also

are included in the total counts (Seiler and Hanratty unpubl. data). Smolt counts from Bingham

Creek, a tributary to the Satsop River, have been variable over the past 13 years, with no clear

trend in abundance (WDFW 1998a, Table 8). Over the full data set, the abundance of smolts
174
175
176

declined by 5% per year, but over the last 5 years, smolt abundance increased by 3% (Fig. 41B).

WDFW (1998a) reported that the Weyerhaueser Corporation has coastal cutthroat trout density

data from more than 80 sites throughout the Chehalis River Basin, and has found that coastal

cutthroat trout densities averaged 0.22-0.23 fish/m2. These densities were higher than those

found in other western Washington river drainages, such as the adjacent Willapa River Basin.

The number of anadromous adult cutthroat trout in Lower Columbia River streams is

almost universally very low (Hooton 1997, WDFW 1998a) (Table 8, Fig. 42). The anadromous

cutthroat trout runs in the Hood and Sandy rivers are considered to be severely depressed. Very

few adults have been collected at Powerdale Dam on the Hood River—4 and 2 were collected in

1992 and 1993, respectively, and none have been collected since then except for 3 adults in 1997

(Hooton 1997, ODFW 1998). There have been no verified observations of anadromous cutthroat

trout on the Sandy River in recent years (R. Hooton19).

The most recent 5-year geometric mean escapement of naturally produced adults in

Abernathy Creek and in the Elochoman and North Fork Toutle rivers ranged from less than 1 to

5 coastal cutthroat trout (WDFW 1998a). The 5-year geometric mean abundance in the Kalama

and North Fork Toutle rivers were 4 and 50 coastal cutthroat trout, respectively. The adult

coastal cutthroat trout caught at the Kalama River are trapped at the falls in a trap whose spacing

allows small coastal cutthroat trout to pass undetected, so the numbers are considered to be an

index of abundance (WDFW 1998c). The number of coastal cutthroat trout caught at the North

Fork Toutle River Fish Collection Facility is viewed as total escapement of the population

following the Mt. Saint Helens eruption (WDFW 1998c). The escapement in the Cowlitz River

has been higher (5-year geometric mean = 1,400 fish), but an unknown fraction of these fish are

of hatchery origin. In addition, there has been a reduction in the percentage of 2-year migrants

returning to the Cowlitz Hatchery from 1980-97, and the numbers of coastal cutthroat trout

smolts released from the Cowlitz Hatchery have been variable but increasing over that time

period (NRC 1996). Smolt-to-adult survival for Cowlitz Hatchery anadromous cutthroat trout

have been 2-7% in 1991 and 1% in 1997, which are similar to estimates for wild fish: smolt-toadult survival was 3.5% on the North Fork of the Toutle River in 1991, and it was 0.84% at

Cowlitz Falls in 1997 (WDFW 1998c).

There is little information about the distribution of freshwater forms of coastal cutthroat

trout in this ESU, and almost no information about relative abundances of migratory and

nonmigratory freshwater forms. The WDFW (1998c) reported that observations of cutthroat

trout above impassable barriers are common in a number of streams in the Lower Columbia

River Basin, including the West Fork of the Elochoman River and the Cowlitz River. In their

SaSI for coastal cutthroat trout, WDFW stated that there is very little information about the

abundances of freshwater forms of coastal cutthroat trout in the Lower Columbia River Basin,

but that their status is probably similar to that of coho salmon and winter steelhead, which are

19 R. Hooton, Oregon Dep. Fish. Wildl., P.O. Box 59. Portland, OR 97207. Pers. commun. to M.

Ruckelshaus. Sept. 1998.
177
178

depressed (WDFW 1998a). The ODFW (1998) provided some information on the densities of

coastal cutthroat trout above the anadromous zone in tributaries of the Hood River Basin. The

ODFW data indicate that the freshwater form of coastal cutthroat trout does not occur in all

streams sampled, but when present it can occur in fairly high densities (3-238 fish/1,000 m2 for

fish greater than 85 mm.) The BRT did not have enough information to determine how the

streams sampled were chosen or how representative they were of conditions that could support

local populations of coastal cutthroat trout in the Lower Columbia River Basin.

Both WDFW and ODFW provided information to the BRT indicating the possibility that

freshwater forms of coastal cutthroat trout in this ESU can produce “smolts” that migrate

downstream. The ODFW (1998) reported that 16-24 cutthroat trout smolts per year have been

collected in a screw trap on the mainstem Hood River upstream from Powerdale Dam between

1994-98; this number can be expanded to more than 400 smolts per year after accounting for trap

efficiency (ODFW 1998). The survival of these smolts after passing Powerdale Dam is not

known. The WDFW (1998c) reported that a downstream migrant trap at Mayfield Dam on the

Cowlitz River has captured between 60-812 smolts per year from 1978-98. There was a single

release of hatchery-derived anadromous cutthroat trout above Mayfield Dam in 1981, but all

cutthroat trout presently residing above the barrier are considered to be the freshwater form

(WDFW 1998c). In addition, WDFW (1998c) estimated that 476-1,756 smolts were produced

from the freshwater form of coastal cutthroat trout above Cowlitz Falls in 1997 and 1998. The

WDFW recently has begun tagging all cutthroat trout smolts originating above Cowlitz Falls,

and the otolith microchemistry was analyzed from one returning tagged fish to show that it did

spend time in salt water. Additional information about the history of the population of coastal

cutthroat trout above the dam was not available to the BRT. The significance of the smolt

production from the freshwater form of coastal cutthroat trout depends on additional information

such as how long the dam has been in place and whether there were anadromous cutthroat trout

above the dam before its construction. If the freshwater form of coastal cutthroat trout above

Mayfield Dam has been isolated for many generations and is still producing smolts, the potential

for the freshwater form to mitigate losses in lower reaches would be greater than if the fish above

the barrier have been isolated very recently. This WDFW information was received too late for

discussion by the BRT, and ODFW/WDFW data lacked sufficient information for detailed BRT

evaluation. Together, however, the information suggests it is possible in at least some cases for

freshwater forms of coastal cutthroat trout to produce juveniles that can become anadromous,

provided habitat conditions allow their survival in the lower reaches of streams and nearshore

marine environments.

 A number of activities have reduced habitat quantity and quality in the Lower Columbia

River Basin. For example, water development projects on the Willamette and Sandy rivers and

in smaller creeks in the Lower Columbia River Basin have resulted in numerous barriers that are

impassable by anadromous salmonids, reducing the amount of available habitat (Kostow 1995).

Dewatering below Marmot Dam on the Sandy River between 1910 and 1970 probably

contributed to reduced population size of the anadromous run in that river. In addition, Kostow

(1995) stated that habitat impacts due to logging activities probably have led to declines in
179

coastal cutthroat trout population productivity in Lower Columbia River tributaries downstream

of the Willamette River.

Trends in anadromous cutthroat trout abundance for Lower Columbia River streams are

all negative (ranging from 5 to 11% per year declines) with the exception of fish returning to the

North Fork Toutle River collection facility, which have increased by nearly 30% per year since

the late 1980s decimation by the Mount Saint Helens eruption (WDFW 1998a). In addition to

declines in naturally produced coastal cutthroat trout populations, hatchery populations in

Abernathy Creek and the Elochoman River also have been declining precipitously over the past

6-10 years (20-60% declines). Trends in incidental catch of coastal cutthroat trout in steelhead

and salmon recreational fisheries in the Lower Columbia River are similar to long-term trends

estimated from escapement to streams (StreamNet 1998) (Fig. 43). The recreational catch of

coastal cutthroat trout in the Lower Columbia River was approximately 5,000 fish per year in the

1970s; by the late 1980s, the catch had declined to approximately 500 per year (Kostow 1995).

These catch data are not a good indication of the absolute numbers of coastal cutthroat trout

since there is not good information on changes in fishing effort over the duration of the data set

for this recreational fishery targeting Pacific salmon and steelhead (WDFW 1998a).

Trends in smolt abundance in the Kalama River have shown a 16% decline per year since

1978. Smolt counts in the Kalama River peaked at just over 16,000 fish in 1983 but were just

over 100 in 1994. These smolt estimates are based on trapped fish in a fyke net at Kalama Falls

and the trap efficiency for cutthroat was assumed to be the same as that for steelhead. Due to

variation in trap efficiency, these numbers are considered to be crude estimates of total smolt

production for this portion of the Kalama River (WDFW 1998c).

No information on the percentage of hatchery coastal cutthroat trout in natural spawning

escapements in the Southwestern Washington/Columbia River ESU was available to the BRT.

Estimates of the percentage of hatchery coastal cutthroat trout in Lower Columbia River sport

catch range from 50-80% between 1979 and 1982 (WDFW 1998a). There is some information

on the numbers and origin of hatchery coastal cutthroat trout released into streams in this region

(see “Artificial Propagation,” p. 113), that indicates potential risks due to interactions with

hatchery coastal cutthroat trout. Coastal cutthroat trout released from the Beaver Creek Hatchery

in the Lower Columbia River have been documented to have stray rates of up to 30% in Lower

Columbia River tributaries (Hisata 1973, Randolph 1986). In addition, a shift in spawn timing of

natural coastal cutthroat trout in the Elochoman River after the early 1970s reflected the spawn

timing of the hatchery coastal cutthroat trout released in that river (Randolph 1986), suggesting

that hatchery fish comprised a large fraction of the total run returning to the Elochoman River

(see “Artificial Propagation,” p. 113). Leider (1997) reported that approximately 75% of the

total Washington state coastal cutthroat trout hatchery effort is concentrated in the Lower

Columbia River area. Anadromous cutthroat trout hatchery releases continue in the Elochoman,

Cowlitz, Washougal, and North Fork Lewis River Basins and in several creeks that drain directly

into the Lower Columbia from the Washington side (WDFW 1998a). Hatchery plants of the

freshwater form of coastal cutthroat trout occur in four streams above anadromous areas: Tilton
180
181

River, Skate, and Canyon creeks, and Little White Salmon River (WDFW 1998c). In addition,

releases of hatchery coho salmon and steelhead continue to occur in a number of streams in this

region.

Upper Willamette River ESU

Counts are available for the freshwater form of coastal cutthroat trout in a few tributaries

in the Willamette River Basin (Hooton 1997). Biologists familiar with coastal cutthroat trout in

this region have argued that streams in the Willamette River Basin support only the freshwater

form of coastal cutthroat trout (both river migrating and nonmigrating) (Dimick and Merryfield

1945, Moring and Youker 1986, ODFW 1998). The ODFW (1998) has provided the BRT with

several data sets supporting the idea that uniquely large populations of the river-migrating form

occur in the mainstem areas of the Willamette River and its tributaries. Increasing numbers of

coastal cutthroat trout have been documented by seining in three sites in the mainstem

Willamette River between Corvallis and the mouth of the McKenzie River (RKm 132-175) from

1992-98. The numbers of coastal cutthroat trout longer than 60 mm caught per seine set ranged

from 0.2 to 8 fish. Over the 7 years of sampling, the numbers of fish caught increased by 11%

to83% per year, depending on the location (ODFW 1998). Some of this increase is due to

increase in sampling efficiency (ODFW 1998). In addition, population indices for coastal

cutthroat trout in the lower McKenzie River were estimated using electrofishing from1988-93

(ODFW 1998). The estimated number of river-migrating coastal cutthroat trout per mile of

shoreline ranged from 113 to 333 fish per mile for fish greater than 20 cm.

Combined counts of coastal cutthroat trout and rainbow trout (15-31 cm) in index pools

in the North Fork of the Middle Fork Willamette River increased between 1975 and 1991, and

the counts have remained stable since then. The abundance of juvenile coastal cutthroat trout

(age-1 and -2+) in an index reach of Dead Horse Canyon Creek, a tributary of the Molalla River

was stable from 1981-91. Scattered sampling of the freshwater form of coastal cutthroat trout in

the Santiam and McKenzie river basins in the late 1970s to early 1980s indicated that densities of

all age classes combined ranged from 61 to 2,200 fish per km.

The ODFW (1998) also provided the BRT with summary information from two studies

conducted in the early 1980s that estimated coastal cutthroat trout densities in streams of the

Coast Range subbasin of the Willamette River. Numbers of coastal cutthroat trout ranged from 166

fish/mile in the North Yamhill River to more than 1,700 fish/mile in the Little Luckiamute River

Basin.

Biologists with the ODFW (ODFW 1998) believe that the freshwater form of coastal

cutthroat trout above Willamette Falls is not likely to contribute substantially to the abundance of

the anadromous form in the lower Willamette River Basin. They cite two reasons for this belief:

(1) very few downstream-migrating coastal cutthroat trout have been counted at the Willamette

Falls bypass facility, and (2) the presence of Ceratomyxa shasta in the lower Willamette River

below the confluence of the Marys River is thought to effectively block downstream migration of

freshwater coastal cutthroat trout because of their susceptibility to this parasite (ODFW 1998).
182

In summary, available information indicates that this ESU produces few, if any,

anadromous cutthroat trout. Information on upper Willamette River populations developed as

part of this status review will be provided to USFWS, which has jurisdiction under the ESA for

freshwater fish populations.

Oregon Coast ESU

Estimates of adult abundance in the Oregon Coast ESU were available for only a few

streams (Table 8, Fig. 44). The most extensive data indicating abundance of adult coastal

cutthroat trout in this ESU are the counts of adults at Winchester Dam on the North Umpqua

River (StreamNet 1998, ODFW 1998). These data are summarized at the end of this section

providing an overview of information regarding risk to the Umpqua River coastal cutthroat trout.

Fisheries biologists familiar with coastal cutthroat trout in Oregon believe that coastal

populations by the early 1980s had probably already suffered significant declines due to

reduction in habitat quality and quantity (Kostow 1995, Hooton 1997). Habitat degradation and

increases in stream temperatures have been noted in many small tributaries in the Oregon coastal

region (Kostow 1995). In addition, dam counts for several Pacific salmon species on the North

Umpqua River indicate consistent declines in abundance beginning in the late 1950s (StreamNet

1998).

Information on trends in coastal cutthroat trout abundance is available for a number of streams

along the Oregon coast (Table 8). Catch-per-unit-effort (CPUE) data for coastal cutthroat trout

> 200 mm and those between 100-200 mm in the South Coos and Millicoma rivers were variable

from 1978 to the present. There is no consensus among biologists about an appropriate size

cutoff for smolts and adults in coastal cutthroat trout (ODFW 1998, WDFW 1998c), and the sizestage relationship undoubtedly varies by region. The size categories reported in the South Coos

and Millicoma rivers represent a mixture of life stages. The numbers of larger fish have been

declining over the past 5 years in both rivers, but the trends are highly variable (StreamNet 1998)

(Fig. 45).

Trends in outmigrating juvenile (> 90 mm) and smolt (> 160 mm) abundance in Tenmile

and Cummins creeks have been stable or positive from 1992 to the present (Johnson unpubl.

data) (Fig. 46). These numbers were corrected for efficiencies of screw traps operated on these

streams. The ODFW believes the outmigrants > 160 mm are anadromous because they show

definite smolting characteristics (silvering, loss of condition) and because the traps are

essentially at the mouths of these small creeks that drain directly into the ocean (S. Johnson20).

In addition to the juvenile and smolt data, ODFW also has been monitoring immigrant adults in

Tenmile Creek for the last 2 years from late June through mid-September: 15 and 38 adult

cutthroat returned to Tenmile Creek in 1996 and 1997 respectively (Johnson unpubl. data).

Additional adult cutthroat may have returned to Tenmile in late September through November

when fall freshets forced the removal of the weir (ODFW 1998). The average size of these

20 S. Johnson, ODFW, 2040 SE Marine Science Drive, Newport, OR 97365. Pers. commun. to M.

Ruckelshaus. July 1998.
183
184
185
186

returning adults was similar between years (325 and 332 mm in 1996 and 1997), and these

lengths were similar to those reported by Giger (1972) for cutthroat returning for their initial

spawning migration in several Oregon coastal rivers from 1965-70. Finally, ODFW reported that

scale samples collected from the adults returning to Tenmile Creek in 1996 and 1997 indicated a

survival rate of 6% for coastal cutthroat trout between their first and second years of spawning

(Johnson unpublished data). In contrast, Giger (1972) estimated a 14-39% survival rate for

coastal cutthroat trout during the same life-history transition in Oregon coastal streams in the

1960s and 1970s.

Resting hole count data indicating trends in adult population sizes are available for three

central Oregon coast streams (Table 8). Snorkel surveys in 12 standard pools in the Nestucca,

Trask, and Wilson rivers from 1965-95 indicated that the mean number of anadromous cutthroat

trout per pool declined during the more than 30-year period (StreamNet 1998) (Fig. 47).

Updated resting hole count data through 1998 were provided to NMFS for these three rivers.

These data were received too late for consideration by the BRT, but are reported in Table C-1

(Appendix C).

The ODFW began its Life-Cycle Monitoring Project in 1998 in a number of coastal

Oregon streams. Estimates of the number of downstream-migrating juvenile coastal cutthroat

trout from trapping data are available for the first year of this program (Johnson unpubl. data).

Numbers of fish greater than 160 mm migrating past the traps in 1998 ranged from 140-780, and

the numbers of coastal cutthroat trout smaller than 160 mm ranged from 400-2,200. Numbers of

outmigrating juveniles roughly corresponded with total watershed size.

Additional information on trends in adult and juvenile coastal cutthroat trout abundance

is available in a report compiled by Hooton (1997). The BRT did not have the actual data for

review from these studies, but the trends were considered in the BRT’s deliberations on risks

facing the Oregon Coast ESU, and results from these studies are summarized here. Hooton

(1997) reported the number of coastal cutthroat trout per pool from several central Oregon

coastal streams over a 10-year period; the trends were relatively stable from 1980-90. In

addition, catch of coastal cutthroat trout in recreational fisheries was reported for the Siuslaw,

Alsea, and Yaquina river basins (Hooton 1997). In some instances, changes in angler effort were

known, helping to interpret data on angler catch. In other cases, no information was available on

angler effort during the time period for which angler catch data were collected. Catch of

anadromous cutthroat trout has declined dramatically in all river systems except the Yaquina

River. In some river systems, the recreational catch data showed strong declines despite

increases in hatchery coastal cutthroat trout releases. Hooton concluded “that abundance of wild

coastal cutthroat trout has declined significantly and that this trend is reflected in reduced angler

effort, a lower percent return of hatchery fish to angler creels, and dramatically lower catches of

wild coastal cutthroat trout” (Hooton 1997, p. 11). Declining trends in anadromous cutthroat

trout in recreational fisheries in the Siuslaw and Alsea river basins were not matched by declines

in abundance of nonmigratory coastal cutthroat trout (Hooton 1997). Hooton (1997) cited

several ongoing studies and field observations of nonmigratory coastal cutthroat trout

populations, indicating that their status in these river basins is relatively stable.
187
188

No information on the percentage of hatchery coastal cutthroat trout in natural spawning

escapements in the Oregon Coast ESU was available to the BRT. There is some information on

the numbers and origin of hatchery coastal cutthroat trout released into streams in this region (see

“Artificial Propagation” section, p. 113), which indicates the potential risks due to interactions

with hatchery coastal cutthroat trout. Relative to other coastal cutthroat trout ESUs, the numbers

of hatchery smolts released in Oregon coastal streams over the last few decades are high.

A factor potentially aggravating this risk is that a single source population, the Alsea River

broodstock, was the primary one used for most of the hatchery coastal cutthroat trout released in

this region. Coastal cutthroat trout from several streams within the Coquille River drainage are

closely genetically related to Alsea River broodstock (see “Genetic Information” section, p. 70),

indicating either that introgression between hatchery and natural coastal cutthroat trout has

occurred, or that hatchery coastal cutthroat trout have displaced naturally produced native coastal

cutthroat trout in those streams. Releases of hatchery coastal cutthroat trout were stopped in

Oregon coastal streams by 1997 and, in many streams, much earlier (see “Artificial Propagation”

section, p. 113). Releases of hatchery coho salmon and steelhead continue to occur in a few

Oregon coastal streams.

The Umpqua River sea-run cutthroat trout status review included a risk assessment of

coastal cutthroat trout in this river drainage up through 1993 (Johnson et al. 1994). The

abundance of coastal cutthroat trout at Winchester Dam was variable from 1946-74, peaking at

almost 2,400 fish. After 1974, a severe decline in abundance occurred (StreamNet 1998)

(Fig. 48). Abundance of coastal cutthroat trout at the dam ranged from 0-53 fish between 1986

and 1994; in 1995-98, increases occurred (79, 81, 91, and through November 15, 1998, 135—the

most since 1982) (ODFW 1998; Loomis footnote 3). As noted in the original Umpqua River

sea-run cutthroat trout status review, there is no way to confirm what proportion of the coastal

cutthroat trout passing Winchester Dam have been or will be anadromous (Johnson et al. 1994).

There has been extensive discussion about the possible causes of the dramatic fluctuations and

recent declines in coastal cutthroat trout numbers in the North Umpqua River (reviewed in

Johnson et al. 1994, Hooton 1997). Possible factors contributing to variation in the numbers of

coastal cutthroat trout at Winchester Dam include shifts in freshwater and marine/estuarine

environmental conditions, changes in counting methods at the dam, and releases of hatchery

coastal cutthroat trout in the North Umpqua River. An estimate of the historical abundance of coastal

cutthroat trout in the Umpqua River Basin suggested that the population size was approximately

30,000 fish before the 1970s (Lauman et al. 1972).

Snorkel surveys were conducted in 1997 in small channel streams in each of the three

main drainages within the Umpqua River Basin (Cramer 1998). Numbers of cutthroat trout

(> 20 cm) per unit of stream sampled (a unit = one each of a contiguous pool, riffle, and glide)

were 0.059 in the North Umpqua River Basin, 0.215 in the South Umpqua River Basin, and

0.280 in the lower Umpqua. These numbers were expanded to produce total estimated

abundances of 2,900 coastal cutthroat trout in the North Umpqua, 12,100 in the South Umpqua,

and 17,900 in the lower Umpqua. Cramer (1998) believed these fish were not likely to be

anadromous since the snorkel surveys were conducted during the summer when sea-run cutthroat

typically are feeding in marine or estuarine habitats. A different picture of the status of coastal
189
190

cutthroat trout in the South Umpqua River Basin was provided in information in Kruzic (1998a)

and Roper (1995). In downstream migrant traps in the upper basin, only 14 juvenile and adult

coastal cutthroat trout were trapped in total during 1991-96 (Kruzic 1998b). Trap efficiencies for

coastal cutthroat trout were not calculated because of the low sample sizes, but coastal cutthroat

trout that were marked indicated trap efficiencies roughly equivalent to those for coho and

chinook salmon juveniles (Kruzic 1998b). In contrast to coastal cutthroat trout abundances in

smolt traps, coho and chinook salmon and steelhead numbers were more than 1,000 a year from

1991 to 1996 (Kruzic 1998b). Densities of coastal cutthroat trout in the mainstem and tributaries

were low or zero, which is in stark contrast to abundant cutthroat reported in Roth (1937).

Kruzic (1998a) and Roper (1995) also found that the distribution of coastal cutthroat trout was

not uniform in the South Umpqua River Basin—they occur primarily in headwater tributaries.

Finally, Roper (1995) found that stream habitat within the South Umpqua River Basin has been

degraded due to timber harvest and road construction, leading to a reduction in instream habitat

complexity and a deleterious shift in stream temperature profiles.

Southern Oregon/California Coasts ESU

Information on adult coastal cutthroat trout abundance is available for only a few streams

in the California portion of this ESU (Table 8, Fig. 49). Historical estimates of abundance of

coastal cutthroat trout in the entire Smith River Basin were 8,500 fish (Gerstung 1998).

Expansions from snorkel surveys of index reaches in the three major forks of the Smith River

suggest that approximately 100-400 adult coastal cutthroat trout (> 25 cm) occurred in each of

the North, Middle and South forks of the Smith River (McCain unpubl. data) (Fig. 46). The

trends in abundance as indicated by these expansion estimates were positive, increasing 1-5 %

annually from 1982 through 1998. Thorough surveys of coastal cutthroat trout presence/absence

in a number of streams in the lower Klamath River have found coastal cutthroat trout to be

widely distributed in a number of tributaries (Voight and Gale 1998, Yurok Tribal Fisheries

unpubl. data). Index counts from snorkel surveys on Blue Creek, a tributary to the lower

Klamath River, have found fall peak weekly counts of 10, 32, and 21 adult coastal cutthroat trout

from 1995-97, respectively (Fig. 50) (Gale 1998). Fisheries biologists familiar with this area do

not believe the adults in Blue Creek are spawning there, due in part to consistently negligible

counts of smolts (D. Gale21).

Electroshocking data from a number of streams in California suggest that densities of

juvenile or smolting coastal cutthroat trout (50-200 mm) are consistently between 15 and 30 fish

per kilometer of stream below barriers to anadromy (Gerstung 1998). Densities of coastal

cutthroat trout in the same size range above barriers were much higher, ranging from 60-400 fish

per kilometer of stream. Adult densities below barriers to anadromy in the Smith River were 3-

12 coastal cutthroat trout per kilometer, and 6-12 adults per kilometer were found in the Little

River (Gerstung 1998). The exception to these density patterns is in Redwood Creek, where

there were only 0.5 adults per kilometer of stream below barriers to anadromous fish (Fig. 50).

21 D. Gale, Yurok Tribal Fisheries Program, 15900 Highway 101 North, Klamath, CA 95548. Pers.

commun. to M. Ruckelshaus. Nov. 1998.
191
192
193

Contributing to the low densities of coastal cutthroat trout is the sharp decline in freshwater and

estuarine habitat quality in Redwood Creek over the last decade (Gerstung 1998). In addition,

the once-productive coastal cutthroat trout recreational fishery in the Redwood Creek drainage is

no longer active (Gerstung 1998).

Smolt abundance numbers for the Winchuck River have declined over the past 3 years (2,800,

1,990, and 1,400 smolts trapped during 1996-98, respectively), but the variation in these numbers

is so high that the trend is not statistically significant (Confer unpubl. data). Errors due to trap

efficiencies and the very short time period over which these data have been collected make it

difficult to weigh these data very heavily in risk determinations. Coastal cutthroat trout sampled

in a downstream weir on Jack Creek, a tributary to the Chetco River, were stable in numbers

from 1989-91, ranging from 643-667 total coastal cutthroat trout trapped (Confer unpubl. data).

The BRT has only one estimate of smolt abundance in the Rogue River: from March-May 1998,

a downstream migrant trap on Lobster Creek, a tributary to the lower Rogue River, caught 146

smolts, 66 juveniles and 4 adult coastal cutthroat trout (Confer unpubl. data). Correcting for trap

efficiency, ODFW biologists estimated that 838 coastal cutthroat trout smolts migrated past the

trap. Fisheries biologists familiar with coastal cutthroat trout in the Rogue River Basin believe

that, although the mainstem is undersampled, the fish are fairly well distributed in the Rogue

River. There used to be a substantial recreational coastal cutthroat trout fishery in the Rogue

River, suggesting that the abundance of coastal cutthroat trout in the basin was probably fairly

high (T. Confer, pers. commun.22).

Smolt abundance from Mill Creek, a tributary to the Smith River, has increased since

1994 (Howard and Albro 1995, 1997) (Table 8, Fig. 50). Estimated smolt numbers in this highly

productive tributary ranged from 750 to nearly 4,000 fish over the 4-year sampling period.

Estimates of coastal cutthroat trout smolt abundance in McGarvey (n=3,615) and Hunter (n=706)

creeks in the lower Klamath River in 1997 were encouraging (Gale 1998). Catch-per-unit-effort

data from the lower Klamath River between 1980 and 1991 showed a variable but relatively

stable trend in the number of cutthroat caught per seine haul (Gerstung 1998) (Fig. 50). In

contrast, electrofishing data from the Klamath River estuary indicated a dramatic increase in the

mean number of coastal cutthroat trout caught per minute between 1991 and 1998 (Gerstung

1998) (Fig. 50).

No information on the percentage of hatchery coastal cutthroat trout in natural spawning

escapements in the Southern Oregon/California Coasts ESU was available to the BRT. There is

some information on the numbers and origin of hatchery coastal cutthroat trout released into

streams in this region (see “Artificial Propagation,” p. 113), which indicates the potential risks

due to interactions with hatchery coastal cutthroat trout. Relative to other coastal cutthroat trout

ESUs, the numbers of hatchery smolts released in southern Oregon and California coastal

streams over the past few decades was very low. Hatchery coastal cutthroat trout releases into

streams in the Oregon portion of this ESU were terminated during the mid-1980s. The Prairie

Creek Hatchery, located on a tributary to Redwood Creek, stopped releases of coastal cutthroat

22 T. Confer, ODFW, 742 Airport Way, P.O. Box 642, Gold Beach, OR 97444. Pers. commun. to M.

Ruckelshaus. July 1998.
194

trout in the late 1980s. Returns of coastal cutthroat trout to the hatchery were seven and eight

fish in 1987 and 1988, respectively (Gerstung 1998). Hatchery coastal cutthroat trout were

planted into Stone Lagoon, a coastal lagoon near Redwood Creek, as recently as 1996 (Gerstung

1998). Releases of hatchery coho salmon and steelhead continue to occur in a few southern

Oregon coastal streams and in California coastal lagoons. Recent changes in angling regulations

for “wild trout” in response to the proposed steelhead ESA listings in California may have a

positive effect on coastal cutthroat trout (Bryant 1998).

Summary and Conclusions of Risk Assessments

Recent events considered

Recent events considered in the BRT risk evaluation include Oregon’s change in angling

regulations in 1995 to establish more restrictive bag and size limits on the catch of coastal

cutthroat trout. Similarly, Oregon, California, and Washington have recently imposed more

restrictive bag and size limits on coastal cutthroat trout in some areas. As discussed earlier, both

Oregon and Washington in the early 1990s began requiring release of wild coastal cutthroat trout

landed in some river drainages. In addition, the BRT’s risk assessments considered potential

effects of changes in hatchery management policies that have already been implemented. These

changes include those affecting coastal cutthroat trout and other species of salmonids (e.g., coho

salmon) that potentially interact with coastal cutthroat trout. Specific changes in harvest and

hatchery practices pertinent to a particular ESU are discussed in individual ESU sections. The

effects of recent (1996-97) flooding in the geographic regions included in the Oregon Coast and

the Southern Oregon/California Coasts ESUs also were considered by the BRT.

General risk considerations

Habitat—As described earlier, coastal cutthroat trout tend to be found in both lower and upper

reaches of streams. Coastal cutthroat trout typically utilize small tributaries of low to midgradients for juvenile rearing, winter refuge, and spawning habitat. In addition, juvenile and

spawning adult coastal cutthroat trout are often found in small headwater streams, frequently

upstream of steelhead and coho salmon spawning areas. The BRT believed that reduction in

freshwater and estuarine habitat quality probably has contributed to declines in coastal cutthroat

trout populations (see “Historical abundance, habitat, and carrying capacity,” p. 147). Changes

in nearshore habitat characteristics due to alterations in freshwater runoff, ocean circulation

patterns, abundance of predator and prey species, and shifts in physical conditions could

contribute to declines in coastal cutthroat trout summer growth rates or survival. The BRT noted

that, coincident with continuing declines in estuarine habitat quality, coastal cutthroat trout catch

in estuarine and river mouth sport fisheries has declined in a number of sites throughout the

Pacific Northwest and Northern California. In addition, evidence suggests that logging practices

decrease instream habitat quality due to increases in water temperature and siltation, removal of

LWD that would otherwise provide important habitat structure, changes in river basin hydrology,

and insertion of culverts beneath logging roads. The increased incidence of culverts in many
195

coastal cutthroat trout streams (due to logging and nonlogging-related road construction) is a

serious threat because of their effectiveness in blocking instream migration, especially for

juveniles and smolts. Documented reduction in coastal cutthroat trout abundance following

logging (see “Historical abundance, habitat, and carrying capacity,” p. 147) was a source of

concern to the BRT.

 For other impacts, evidence that links a particular source of freshwater or estuarine

habitat degradation to a response in coastal cutthroat trout populations is largely anecdotal.

These sources include conversion of land surrounding coastal cutthroat trout streams to

agricultural and commercial development, water diversions, habitat blockages, floods, changes in

ocean conditions, dredging, and reduction in the presence of other salmonid carcasses for

nutrient provision. Despite the lack of direct quantification of these effects on coastal cutthroat

trout populations, it is clear that drastic habitat modification due to these factors has occurred in

many areas. The BRT noted that most biologists familiar with coastal cutthroat trout believe that

such habitat modification has led to a reduction in present habitat capacity relative to historical

levels.

Hybridization—In addition to first-generation hybrids between coastal cutthroat trout and

steelhead/rainbow trout, the BRT noted that coastal cutthroat trout with more fully introgressed

genes have been detected in natural populations, indicating that some hybrids do survive and

interbreed (back cross) with parental species. It is not clear what effect these hybridizations have

on coastal cutthroat trout populations. As discussed earlier (see “Hybridization and

introgression,” p. 75), the extent of hybridization between coastal cutthroat trout and O. mykiss

and the environmental characteristics with which hybridization is correlated are not well

understood. In addition, the BRT discussed the importance to risk evaluations of being able to

distinguish historical (i.e., background or “natural”) levels of coastal cutthroat trout × O. mykiss

hybridization from levels of present-day hybridization. Since it is not known how human

activities may have affected both the frequency of coastal cutthroat trout × O. mykiss

hybridization events and the fitness consequences of such hybridizations, evaluating the risks to

native coastal cutthroat trout is difficult.

Ecological interactions—The BRT felt that the increased competition from hatchery coho

salmon may be an important risk factor for juvenile coastal cutthroat trout. The BRT noted with

concern that streams in Washington with continuing releases of hatchery coho salmon fry also

show declining trends in coastal cutthroat trout abundance. In addition, the BRT discussed the

possible effects of dramatic increases in sea lion and harbor seal populations on predation of

coastal cutthroat trout, especially in the Lower Columbia River Basin. Specific information

relating to risks to coastal cutthroat trout from human-induced effects on ecological interactions

was not available.

Paucity of information relating to risk

The dearth of information on risks facing coastal cutthroat trout populations is more

pervasive than data gaps for other species of Pacific salmonids. This situation is similar to the

relative lack of data to guide decisions about ESU boundaries for coastal cutthroat trout, as
196

discussed earlier. Current or historical abundance information, especially for adult coastal

cutthroat trout, is available for only a very small proportion of the known populations within any

ESU. In contrast to the situation for status reviews of the other species of Pacific salmonids, the

BRT for coastal cutthroat trout has had to base its risk evaluations more heavily on abundance

estimates for a small number of populations spanning only a few years, presence/absence data,

and professional judgements by biologists familiar with coastal cutthroat trout in specific

geographic regions. Information on risks from hatchery-origin fish and hybridization with

steelhead and rainbow trout also is very limited for coastal cutthroat trout.

Biologists familiar with coastal cutthroat trout generally believe that, in some areas (e.g.,

Lower Columbia River Basin, Puget Sound, Northern California), anadromous cutthroat trout

populations have experienced significant declines relative to historical levels of abundance (see

“Biological Information by ESU,” p. 158). In many cases, concrete evidence for long- or shortterm declines in abundance is not available. Instead, biologists have based their opinions on

such information as 1) anecdotal reports from anglers familiar with local streams, 2) success of

periodic sampling of streams for coastal cutthroat trout for genetic or other life-history data, and

3) incidental observations of coastal cutthroat trout during surveys for other species of Pacific

salmonids.

The scarcity of information for coastal cutthroat trout has made the risk assessments

especially difficult for the BRT. The BRT wrestled with a fundamental dilemma stemming from

lack of data, which is that insufficient information about key risk factors, such as abundance, can

result in two alternative conclusions: 1) there is not enough evidence to demonstrate that coastal

cutthroat trout are at significant risk of extinction, and 2) there is not enough evidence to

demonstrate that coastal cutthroat trout are not at risk. This uncertainty existed for many of the

coastal cutthroat trout ESUs. For some BRT members, uncertainty about status coupled with a

collective sense among local biologists that coastal cutthroat trout were in decline suggested that

an ESU was at risk of extinction. Finally, the paucity of information led other BRT members to

conclude that one or more ESUs were not at significant risk. The BRT stressed that the latter

risk conclusion does not necessarily indicate that an ESU is healthy; rather, it may simply

indicate that there is insufficient information to demonstrate that it is not healthy.

The BRT continues to wrestle with how to most effectively address the inevitable

uncertainty in making risk evaluations for Pacific salmonids. Developing ways of incorporating

uncertainty into the BRT’s risk evaluations is an evolving process. Elements of uncertainty are

present in risk assessments for any species of conservation concern; the significant paucity of

data for coastal cutthroat trout have made this risk evaluation especially challenging. Summaries

of BRT risk votes are provided in Appendix B.
197

General conclusions

If a man will begin with certainties, he shall end in doubts; but if he will

be content to begin with doubts he shall end in certainties.

Sir Francis Bacon, The Advancement of Learning, 1605

The two methods used by the BRT to characterize uncertainty in risk assessments

generally were consistent in their outcomes (for a description of methods, see “Overall

Evaluation of Risk and Uncertainty,” p. 141). In the first method, each BRT member assigned a

certainty score (1=low, 5=high) to the overall risk vote (in danger of extinction, not at significant

risk of extinction but likely to become so in the foreseeable future, and not presently at

significant risk of extinction or endangerment) for each ESU. The certainty scores for most

ESUs were low (in the range of 1 to 3), reflecting considerable uncertainty regarding the

conservation status of coastal cutthroat trout.

In the second method, BRT members could split their vote and allocate “likelihood

points” among the three risk categories. Results from this method were generally concordant

with and support information provided by the first method. That is, when the majority of BRT

votes fell in a particular risk category, the majority of likelihood points also fell in the same

category. For all ESUs, a small fraction of likelihood votes occurred in the “in danger of

extinction” category. This result reflects the very limited information available for conducting

risk evaluations for coastal cutthroat trout. Although in many cases available information did not

provide conclusive evidence of high risk, it also did not clearly demonstrate that the ESUs were

not at risk. As a result, at least some BRT members felt that they could not completely exclude

the possibility that a particular ESU is presently in danger of extinction. However, when asked

to pick only one risk category (the first method), no BRT members concluded that any ESUs are

presently in danger of extinction.

Only one ESU (Southwestern Washington/Columbia River) was considered to be at

significant risk by a majority of the BRT. The BRT was evenly divided as to whether another

ESU (Oregon Coast) is likely to become endangered in the foreseeable future. The BRT also had

some concerns about the status of coastal cutthroat trout in all of the remaining ESUs, but

available information did not clearly indicate high risk in these cases. In general, although

comprehensive data on the abundance of nonmigratory O. c. clarki are not available in most

cases, qualitative observations suggest that nonmigratory forms of this subspecies are not at high

risk in any ESU. Most of the concerns for the conservation status of coastal cutthroat trout focus

on the depletion or loss of migratory (especially anadromous) life-history forms. Migratory

forms play an important role in the evolutionary ecology of coastal cutthroat trout by forging

genetic and demographic linkages among populations. Available information indicates that these

life-history traits are in part genetically controlled, and their loss can have important

consequences for the sustainability and future evolutionary trajectories of coastal cutthroat trout

ESUs.
198

Summary of ESU-specific conclusions

Puget Sound ESU—Few data exist concerning historical and present abundance of coastal

cutthroat trout in the Puget Sound ESU region. The BRT had almost no estimates of adult

population sizes. Exceptions were a WDFW estimate of the 1997 spawning escapement in the

Skagit River Basin of 13,000 fish and counts of adults at an upstream migrant trap designed for

coho salmon on the Deschutes River in southern Puget Sound (5-year geometric mean = 74

coastal cutthroat trout). Anecdotal reports suggest low abundance of coastal cutthroat trout in

southwestern Puget Sound streams. In general, the BRT noted with concern the lack of

information regarding the distribution and abundance of coastal cutthroat trout throughout the

Puget Sound region. There are some data indicating that juvenile coastal cutthroat trout are

relatively well distributed in the Skagit and Stillaguamish river basins and along the Strait of

Juan de Fuca. The BRT acknowledged that widespread habitat degradation and loss have

occurred in the Puget Sound region. This reduction in habitat capacity constitutes an important

ongoing risk to coastal cutthroat trout that has not been quantified.

Trend data from this ESU available to the BRT were downstream migrant counts from

streams in eastern Hood Canal, the Skagit River basin and in southern Puget Sound (up to 1987

only), adult counts on the Deschutes River and CPUE data for adults over the past 2 to 7 years in

three northern Puget Sound river basins. Trends in smolt numbers were mixed in both Hood

Canal and southern Puget Sound. The BRT did not weigh the southern Puget Sound smolt trends

heavily because no information on recent smolt abundance in those streams exists. In addition,

the downstream migrant trends in the Skagit River basin were considered to be at best rough

indicators of true trends because the trap locations and dates trapped were designed for estimates

of coho salmon smolt production. The numbers of coastal cutthroat trout trapped therefore may

not provide an accurate picture of abundance. Increases in coastal cutthroat trout smolt numbers

in some eastern Hood Canal streams coincided with declines in coho salmon abundance. A

negative correlation between abundances of coastal cutthroat trout and coho salmon suggested to

the BRT that interactions between these two species may be reducing the abundance of coastal

cutthroat trout in some streams. Streams with reduced coho salmon numbers may result in a

relaxation of competition that allows an increase in coastal cutthroat trout abundance.

Unfortunately, there is no information regarding smolt-to-adult survival in this ESU, so

interpretation of the significance of smolt trends for overall risk to these populations is difficult.

Furthermore, as outlined previously, the BRT discussed the possibility that smolt abundance was

already depressed before these trap data were obtained. Historical estimates of smolt abundance

were not available, so no definitive conclusions about the risks to coastal cutthroat trout

populations could be made from the smolt count data.

The CPUE data for the Stillaguamish and Snohomish river populations showed

increasing trends; the Skagit River CPUE has been declining. The BRT felt that the short time

frames (2-7 years) over which these data have been collected and the possibility that significant

declines in abundance occurred before data collection began reduced the usefulness of these

trends in assessing population status. In addition, WDFW biologists feel that the variation in the

adults caught may be due in part to annual variation in fishing conditions. Finally, there are
199

indications that the proportion of repeat spawners in northern Puget Sound river basins has been

declining. The risk posed by this decline has not been quantified and, without good estimates of

the numbers of coastal cutthroat trout in spawning populations each year, the BRT concluded

that the lost opportunity for larger, more fecund fish to contribute to spawning populations

represents a significant threat to continued productivity.

In addition to information about population sizes and trends in abundance for coastal

cutthroat trout in this ESU, the BRT considered another important risk factor—the potential loss

of life-history diversity. In particular, the anadromous life-history type appears to be declining in

some Puget Sound streams containing coastal cutthroat trout. However, the BRT felt that risks

to the integrity and long-term sustainability of the Puget Sound ESU due to loss of life-history

diversity were relatively low compared to other coastal cutthroat trout ESUs, in which there are

more streams with documented declines in anadromous life-history types.

The influence of hatchery coastal cutthroat trout in the Puget Sound ESU is probably

relatively low compared to the impacts of hatchery fish on the productivity of other Pacific

salmon. The proportion of hatchery fish caught in the recreational fisheries for coastal cutthroat

trout in Hood Canal is low. On the other hand, the BRT acknowledged that there are some

hatchery-related threats to native natural coastal cutthroat trout populations in this ESU. The

WDFW considers the northern Puget Sound coastal cutthroat trout populations to be of mixed

origin, indicating that fish of nonnative origin may have contributed to the genetic composition

of those populations (WDFW 1998a). Production in most streams within the ESU is considered

“wild,” indicating that hatchery fish do not contribute significantly to natural spawning

escapements (WDFW 1998a). Finally, the BRT discussed the possibility that interactions

between coastal cutthroat trout and naturally occurring or hatchery-released coho salmon and

steelhead can negatively affect the abundance of coastal cutthroat trout in this ESU.

After considering this information, a majority of the BRT members felt that the Puget

Sound ESU is not presently in danger of extinction, nor is it likely to become so in the

foreseeable future. A minority felt that the ESU was likely to become endangered in the

foreseeable future. The uncertainty underlying these conservation assessments was high: most

BRT members reported certainty scores of 2 or 3 for their risk evaluations. The BRT felt that

widespread, often irreversible, habitat degradation of freshwater and estuarine habitat has been

caused by development, logging, and agriculture. Thus, extant habitat capacity is clearly lower

than historical levels. Population levels and major threats appear to have been relatively constant

over the past 10-15 years, although many of these populations are believed to be depressed

relative to historical levels. Recent flooding events likely have contributed to declines in

cutthroat trout numbers and productivity. In addition, a number of biologists familiar with

coastal cutthroat trout feel that fishing mortality suffered by cutthroat trout is an important source

of risk. The BRT expressed concern that historical and continuing reduction in habitat quality,

combined with very little information with which to assess status, created considerable

uncertainty in evaluating risk for Puget Sound coastal cutthroat trout.
200

Olympic Peninsula ESU—The BRT had little information with which to estimate population

abundances for coastal cutthroat trout in the Olympic Peninsula ESU. The general impression

from state and tribal fisheries biologists is that juvenile coastal cutthroat trout are well distributed

in streams along the western Strait of Juan de Fuca and northern Washington coast, and the BRT

believed there are probably some highly productive coastal cutthroat trout streams in this

geographic region. For example, smolt abundances in Dickey Lake are high relative to numbers

of smolts in Puget Sound and Hood Canal streams. On the other hand, the BRT acknowledged

that ongoing habitat destruction, primarily due to logging and its associated activities (e.g., road

building, stream blockages by culverts), continue to be a source of risk to coastal cutthroat trout

in many Olympic Peninsula streams.

The only quantitative data available to the BRT for the Olympic Peninsula ESU were

counts of downstream migrants on tributaries of the Clearwater (from 1981 to present), Dickey

(1992-1994), and Hoko (1986-1989) rivers and in Salt Creek along the Strait of Juan de Fuca

(1998). The trends among Clearwater tributaries were mixed, suggesting to the BRT that some

tributary streams could be characterized as good producers and that others were declining in

smolt production. The absolute numbers of outmigrants in all streams trapped was encouraging

to the BRT. Nevertheless, the BRT did not weigh trends from the Hoko River heavily in its risk

determinations because these data are not current; in addition, the Dickey River trends were

based on only 3 years of trapping designed to estimate coho salmon production. It was difficult

to interpret the outmigrant data, in part because of a lack of smolt-to-adult survival estimates and

because declines in production may have occurred before 1981, when earliest data collection

began. The BRT believed that continued demonstrations of consistent smolt production from

outmigrant trapping could support the general sense among fisheries biologists that coastal

cutthroat trout are well represented in streams throughout the Olympic Peninsula.

The BRT indicated that risks to the Olympic Peninsula ESU from loss of life-history

diversity were relatively low. This ESU received a lower risk score for this source of risk than

any other ESU.

Risks associated with hatchery coastal cutthroat trout are probably low in this ESU.

Hatchery releases of coho salmon fry occur in some areas on the Olympic Peninsula, which may

increase stress on coastal cutthroat trout due to interspecific competition levels higher than what

might occur naturally.

A majority of the BRT concluded that the Olympic Peninsula ESU is not presently in

danger of extinction, nor is it likely to become so in the foreseeable future. A single member felt

that the ESU is likely to become endangered in the foreseeable future. However, these risk

evaluations must be considered in light of the very high uncertainty expressed by the BRT. The

certainty scores for the Olympic Peninsula ESU risk assessment were the lowest of all of the

coastal cutthroat trout ESUs, with most scores being 1 or 2. The BRT believed there are

indications that there is productive coastal cutthroat trout habitat to support this ESU, but that

information was not available to confirm such a possibility. The continuing habitat degradation

throughout the region was a significant source of concern to the BRT. Without data to evaluate
201

the effects of land-use practices on coastal cutthroat trout abundance in this region, the

conservation status of this ESU remains unclear.

Southwestern Washington/Columbia River ESU—According to WDFW, the southwestern

Washington-Lower Columbia River region historically supported healthy and highly productive

coastal cutthroat trout populations. Coastal cutthroat trout, especially the freshwater forms, may

still be well distributed in most river basins in this geographic region, probably in lower numbers

relative to historical population sizes. Severe habitat degradation throughout the Lower

Columbia River area has contributed to dramatic declines in anadromous cutthroat trout

populations and two near extinctions of anadromous runs in the Hood and Sandy rivers. The

BRT was concerned about the extremely low population sizes of anadromous cutthroat trout in

Lower Columbia River streams, indicated by low incidental catch of coastal cutthroat trout in

salmon and steelhead recreational fisheries and low trap counts in a number of tributaries

throughout the region. Although efficiencies for these traps in catching coastal cutthroat trout

are not known, numbers of adults returning to traps have been consistently below 10 fish in most

streams included in this region over each of the past 6 years. In contrast, the BRT believed that

information on the distribution of freshwater forms of coastal cutthroat trout in this region,

though mostly anecdotal, probably accurately reflected their widespread occurrence in streams

throughout the region.

Trends in anadromous adults and outmigrating smolts in the southwestern Washington

portion of this ESU are all declining. The BRT was aware that WDFW considers streams in this

region to have relatively good coastal cutthroat trout habitat; however, data available to the BRT

do not support the idea that the anadromous cutthroat trout in this area are at low risk. Returns of

both naturally- and hatchery-produced anadromous cutthroat trout in almost all Lower Columbia

River streams have been declining markedly over the last 10-15 years. Indeed, the only

anadromous cutthroat trout population in the Lower Columbia River to show increases in

abundance over the last 10 years is the North Fork Toutle River population, which is thought to

be recovering from the effects of the Mt. Saint Helens eruption. In spite of its increasing trend,

WDFW states that its population numbers are still critically low (approximately 100 total adults

in run). The BRT also was concerned about data for hatchery-origin coastal cutthroat trout in the

Lower Columbia River that indicated declines in smolt-to-adult survival since the 1980s.

A significant risk factor for coastal cutthroat trout in this ESU is reduction in life-history

diversity. Serious declines in the anadromous form have occurred throughout the Lower

Columbia River, and it has been nearly extirpated in at least two rivers on the Oregon side of the

basin. Available information suggests that in many streams the freshwater forms of coastal

cutthroat trout are well distributed and occur in relatively high abundance in comparison to

anadromous forms in the same stream. The BRT discussed evidence presented from ODFW and

WDFW that freshwater coastal cutthroat trout can produce smolts that migrate to saltwater.

Although the BRT acknowledged that this possibility could mitigate risks to anadromous forms

of coastal cutthroat trout, the observation that sea-run cutthroat trout population sizes have

remained consistently low in many areas is a cause for concern. In summary, the BRT believed

that, even if freshwater forms of coastal cutthroat trout have been producing occasional smolts,
202

this production has not resulted in demonstrably successful re-establishment of anadromous

forms. Habitat degradation in stream reaches accessible to anadromous cutthroat trout and poor

ocean and estuarine conditions probably have combined to severely deplete this life-history form

throughout the Lower Columbia River Basin. Without the appropriate freshwater and estuarine

habitat for the expression of the anadromous life history, a greater risk of extinction may occur.

The significance of this reduction in life-history diversity to the integrity of the ESU and the

likelihood of its long-term persistence were major sources of concern to the BRT.

Negative effects of hatchery coastal cutthroat trout may be contributing to the risks facing

native naturally produced coastal cutthroat trout in this ESU. The Lower Columbia River

tributaries are the only streams in Washington still receiving hatchery-origin coastal cutthroat

trout, although the total numbers of released hatchery fish have been substantially curtailed

recently. The BRT was concerned that in the early 1980s an estimated 50-80% of the

recreational catch for coastal cutthroat trout in the Lower Columbia River was composed of

hatchery fish. Biologists familiar with coastal cutthroat trout believe that recreational catch data

reflect true trends in coastal cutthroat trout abundance (Hooton 1997). Furthermore, the largest

returns of coastal cutthroat trout in this region are to the Cowlitz River Basin, and existing

information is consistent with the interpretation that a significant proportion of those fish are of

hatchery origin (WDFW 1998a). The BRT emphasized that the ultimate effects of hatchery fish

depend on the relative sizes of hatchery and native naturally produced populations, the spatial

and temporal overlap of hatchery and native naturally produced fish throughout their life cycles,

and the actual extent to which hatchery fish spawn naturally and interbreed with naturally

produced fish. In addition, the extent to which natural coastal cutthroat trout are incidentally

harvested in fisheries targeting hatchery coastal cutthroat trout and other salmonids also will

affect the magnitude of the risks to coastal cutthroat trout due to hatchery fish.

The BRT was unanimous in concluding that the Southwestern Washington/Columbia

River ESU was likely to become endangered in the foreseeable future. Certainty scores ranged

from 2 to 4. Although these scores reflect only a moderate degree of certainty regarding the risk

assessment, they were on average higher than for any other coastal cutthroat trout ESU. The

BRT was especially concerned about the widespread declines in abundance and the small

population sizes of anadromous cutthroat trout throughout the Lower Columbia River, as

exemplified by near extinctions of anadromous cutthroat trout runs in the Hood and Sandy rivers.

The severe reductions in abundance of this life-history form could have deleterious effects on the

ability of this ESU to recover from widespread declines. Reductions in the quantity and quality

of nearshore ocean, estuarine, and riverine habitat have probably contributed to declines, but the

relative importance of these risk factors is not well understood. In addition, the BRT discussed

the possibility that recent increases in marine mammal and bird predators may be important risk

factors. The BRT was encouraged by recent steps taken by the states of Washington and Oregon

to reduce mortality due to directed and incidental harvest of coastal cutthroat trout.

Upper Willamette River ESU—The conservation status of this ESU was not formally evaluated

by the BRT. As stated earlier, since it is believed by ODFW that few anadromous cutthroat trout

are produced in this ESU, USFWS has jurisdiction for these populations.
203

Oregon Coast ESU—Coastal cutthroat trout in the Oregon coastal region occur mostly in small

populations that are relatively well distributed. Most of the abundance information considered

by the BRT for this ESU was juvenile and smolt abundance, with the prominent exception of the

adult counts at Winchester Dam on the North Umpqua River. In general, the BRT was

encouraged by the numbers of juveniles in coastal streams with relatively large basins. These

data are available for only the last 2 years, however, so how well these juvenile counts translate

into adult abundances or longer-term population trends is not known. The estimated pre-1970s

abundance of anadromous cutthroat trout in the largest river basin contained within this ESU, the

Umpqua River, is 30,000 adults. A recent estimate of total run size, based on expansions of

observed numbers of adults from snorkel surveys, is similar. The BRT expressed concern about

assumptions underlying expansion methods to estimate anadromous run size using snorkel

survey data for freshwater forms of coastal cutthroat trout in the Umpqua River basin.

Conflicting information about the abundance and distribution of coastal cutthroat trout in the

South Umpqua River basin suggested to the BRT that there is insufficient information to

determine the status of coastal cutthroat trout in that drainage. The numbers of adults returning

to the North Umpqua River have been critically low in recent years (5-year geometric mean = 18

fish), although, for the past 3 years, 79, 81, and 135 (through November 15, 1998) (Loomis

footnote 3) adult coastal cutthroat trout have been counted at Winchester Dam. The BRT noted

that widespread habitat degradation due to logging, road construction, and development along

coastal streams probably constitute a significant reduction in habitat capacity relative to

historical conditions.

Smolt production in two small drainages (Cummins and Tenmile creeks) in central

Oregon has shown an increasing trend over the past 7 years. However, the percentage of repeat

spawners has declined in both drainages relative to estimates in the early 1970s. All other

streams on the Oregon coast for which data were available are experiencing moderate declines in

adults and juveniles. In some areas, declines may have occurred primarily in anadromous

cutthroat trout populations. For example, in the Alsea and Siuslaw river basins, declines in

anadromous runs have occurred as indicated by recreational catch data, but ODFW believes there

is no evidence for similar declines in nonmigratory coastal cutthroat trout in those same basins.

The BRT was concerned about reductions in anadromous life-history forms throughout

this ESU. Information available to the BRT indicated that sea-run cutthroat trout are suffering

more serious declines than are freshwater forms along Oregon coastal streams. The BRT

believed that the risks associated with possible reductions in historical connections among

streams by more migratory anadromous cutthroat trout could be a significant threat to the

persistence of the ESU. For example, one possible interpretation of the high levels of genetic

differentiation among populations in the Coquille River Basin is that populations are no longer

connected by gene flow from the anadromous form. ODFW has suggested that freshwater forms

of coastal cutthroat trout may be producing smolts in several coastal streams. The BRT did not

have estimates of the numbers of adult anadromous trout in those streams, so it was difficult to

evaluate the possibility that freshwater forms could buffer anadromous forms from declines.
204

Current risks due to interactions with hatchery coastal cutthroat trout are probably

moderately low in this ESU. Nevertheless, the widespread releases of Alsea River hatchery

broodstock in Oregon coastal streams have stopped only relatively recently. Genetic samples

indicate that hatchery coastal cutthroat trout from the Alsea River broodstock have influenced the

genetic composition of several coastal cutthroat trout populations in the Coquille River drainage.

Hybrids between coastal cutthroat trout and steelhead/rainbow trout were detected in genetic

samples from the Coquille River Basin and a few other streams in this ESU. As discussed

earlier, some degree of hybridization between O. mykiss and coastal cutthroat trout may occur

naturally without the direct influence of hatchery-origin fish. However, risks to coastal cutthroat

trout populations due to hybridization may increase if either 1) changes in habitat conditions or

2) an increase in the abundance of hatchery-origin O. mykiss increase the frequency of natural

hybridization or change its fitness consequences.

All members of the BRT agreed that the Oregon Coast ESU is not presently at risk of

extinction. However, the BRT was evenly split in determining whether the ESU is likely to

become endangered in the foreseeable future or not likely to become endangered. The certainty

in this assessment was fairly low: the certainty scores were mostly 2 or 3. The BRT was

concerned about habitat degradation that continues within this region, and the scarcity of

abundance information for major drainages limited the BRT’s efforts to conduct a risk

evaluation. Hatchery records indicate that the Alsea River coastal cutthroat trout stock was

released widely in streams throughout the Oregon coastal region. Recent reductions in releases

of hatchery-origin coastal cutthroat trout and coho salmon fry, coupled with a statewide catchand-release recreational fishery policy for naturally produced native coastal cutthroat trout, may

have reduced risks associated with those factors. The BRT noted that reduced nearshore ocean

habitat quality was probably a significant threat to coastal cutthroat trout in this region, but

quantifying those effects on coastal cutthroat trout abundance is very difficult. Finally, the BRT

was concerned about incidental mortality of coastal cutthroat trout in this ESU due to fishing

pressure on Pacific salmon and steelhead.

Southern Oregon/California Coasts ESU—Coastal cutthroat trout in this ESU are thought to

be widely distributed in many small populations. Two possible exceptions are populations in the

Rogue and Smith river basins, where the abundance of coastal cutthroat trout may be

comparatively high. Smolt abundance in Lobster Creek, a Rogue River tributary, was estimated

to be over 800 fish in 1998. In addition, fisheries biologists familiar with the Rogue River Basin

believe it supports many well-distributed coastal cutthroat trout populations. The estimated

historical sea-run cutthroat trout population in the Smith River Basin was 8,500 fish. Expansion

estimates of fish greater than 25 cm in the three major forks of the Smith River indicate that each

fork supports at least 300 coastal cutthroat trout. In addition, Mill Creek, considered to be one of

the most productive coastal cutthroat trout tributaries in the Smith River Basin, has had between

1,000 and 4,000 outmigrating smolts over each of the past 4 years. Again, lack of information on

smolt-to-adult survival and trap efficiencies makes interpreting smolt abundance estimates in the

Rogue and Smith river basins difficult. Population sizes are thought to be relatively small in

other streams throughout this region, in part because it is the southern limit of this cutthroat trout

subspecies. The BRT believes that severe habitat degradation has occurred in this region,
205

primarily due to activities associated with agriculture, flood control, logging, road construction,

and local development. These activities have contributed to a reduction in habitat capacity

relative to historical levels. In addition, seasonal dewatering of stream mouths occurs naturally

in Northern California, resulting in sporadic blockages of access to the sea for anadromous fish

in some streams. Also, large water withdrawals in several larger coastal river basins (e.g.,

Rogue, Klamath/Trinity, and Eel rivers) and several of the smaller coastal rivers have reduced

the quantity and quality of the remaining riverine and estuarine environments in the geographic

region encompassing this ESU.

Biologists familiar with this region believe, and anecdotal evidence suggests, that major

declines in coastal cutthroat trout populations have occurred since historical times, and that some

populations appear to have been relatively stable or increasing in size since that time. The data

available to the BRT indicate increasing short-term trends in smolt abundance in Mill Creek, and

increasing short-term trends in adult abundance in the lower Klamath River tributaries and its

estuary and in the Smith River Basin. Exceptions include recent declines in the incidence of

coastal cutthroat trout in Redwood Creek.

Reductions in the anadromous form of coastal cutthroat trout are not thought to be a

significant source of risk to the overall ESU. Although declines in some anadromous runs have

occurred, there was no evidence presented to the BRT that these declines have occurred

throughout a significant portion of the geographic area.

Risks due to interactions with hatchery coastal cutthroat trout are probably low in this

ESU. Other risks the BRT noted for coastal cutthroat trout in this region were possible

deleterious interactions with naturally occurring or hatchery-derived coho salmon and steelhead,

and incidental catch of coastal cutthroat trout in sport fisheries targeting steelhead and coho

salmon. The BRT was encouraged by recent changes in harvest regulations aimed at reducing

risks to natural trout from direct and indirect harvest mortality.

A majority of the BRT believed that the Southern Oregon/California Coasts ESU was not

presently in danger of extinction, nor did they believe it was likely to become so in the

foreseeable future. A minority concluded that the ESU was likely to become endangered in the

foreseeable future. Most BRT members indicated that their risk evaluations were associated with

a low degree of certainty. Certainty scores ranged from 1 to 4, but most of the BRT members

indicated a certainty level of 2. As with many other ESUs for coastal cutthroat trout, the BRT

was hindered by the scarcity of abundance information for this ESU. The BRT emphasized that

continuing threats to the quality of freshwater and estuarine habitat for cutthroat trout in this

region are sources of concern.
206
207

CITATIONS

Alaska Department of Fish and Game (ADFG). 1978. Alaska’s fishery atlas, vol. 1, 40 p.

Alaska Geographic Society, The. 1978. Southeast Alaska’s Panhandle. Alaska Geographic

5(2):2-32.

Allan, J.H. 1980. Life history notes on the Dolly Varden charr (Salvelinus malma) in the upper

Clearwater River, Alberta. Alberta Energy and Natural Resouces, Fish and Wildl. Div.,

Red Deer, Alberta, Canada.

Allen, M.J., and G.B. Smith. 1988. Atlas and zoogeography of common fishes in the Bering Sea

and northeastern Pacific. U.S. Dep. of Commerce, NOAA Tech. Rep. NMFS 66, 151 p. 

Allendorf, F.W., and R.F. Leary. 1988. Conservation and distribution of genetic variation in a

polytypic species, the cutthroat trout. Conserv. Biol. 2:170-184.

Allendorf, F.W., and S.R. Phelps. 1980. Loss of genetic variation in a hatchery stock of cutthroat

trout. Trans. Am. Fish. Soc. 109:537-543.

Allendorf, F.W., and N. Ryman. 1987. Genetic management of hatchery stocks. In N. Ryman

and F. Utter (eds.), Population genetics and fishery management, p. 141-159. Univ.

Washington Press, Seattle.

Allendorf, F.W., and F.M. Utter. 1979. Population genetics. In W.S. Hoar, D.J. Randall and J.R.

Brett (eds.), Fish Physiology, p. 407-454. Academic Press, New York.

Allendorf, F.W., and R.S. Waples. 1996. Conservation and genetics of salmonid fishes. In J.C.

Avise (ed.), Conservation genetics: case histories from nature, p. 238-280. Chapman &

Hall, New York.

Allendorf, F.W., N. Ryman, and F. Utter. 1987. Genetics and fishery management: past, present,

and future. In N. Ryman and F. Utter (eds.), Population genetics & fishery management,

p. 1-19. Univ. Washington Press, Seattle.

Anderson, B.G., and D.W. Narver. 1975. Fish populations of Carnation Creek and other Barkley

Sound Streams—1974. Fish. Res. Board Can., Nanaimo, British Columbia. Manuscr. Rep.

Ser. 1351, 73 p.

Andrusak, H. 1968. Interactive segregation between adult Dolly Varden (Salvelinus malma) and

cutthroat trout (Salmo clarki clarki) in small coastal British Columbia lakes. M.S. Thesis,

Univ. British Columbia, Vancouver, 76 p.

Andrusak, H., and T.G. Northcote. 1970. Management implications of spatial distribution and

feeding ecology of cutthroat trout and Dolly Varden in coastal British Columbia lakes.

British Columbia Fish and Wildl. Branch, Fish. Manage. Publ. No. 13, 14 p.
208

Andrusak, H., and T.G. Northcote. 1971. Segregation between adult cutthroat trout (Salmo

clarki) and Dolly Vardon (Salvelinus malma) in small coastal British Columbia lakes. J.

Fish. Res. Board Can. 28:1259-1268.

Arcata Marsh and Wildlife Sanctuary (AMWS). 1998. Aquaculture fish. Humbolt State Univ.,

Arcata, CA. (Available through Internet, www.humboldt.edu)

Armstrong, R.H. 1971. Age, food, and migration of sea-run cutthroat trout, Salmo clarki, at Eva

Lake, Southeastern Alaska. Trans. Am. Fish. Soc. 100(2):302-306.

Armstong, R.H., and J.E. Morrow. 1980. The Dolly Varden charr, Salvelinus. In E.K. Balon

(ed.), CHARRS - Salmonid fishes of the genus Salvelinus, p. 99-140. W. Junk Publ., the

Hague, the Netherlands.

Ashbaugh, J.G. (ed.). 1994. The Pacific Northwest, Geographical Perspectives. Kendall/Hunt

Publishing Co., Dubuque, 526 p.

Ashbrook, C., and H.J. Fuss. 1996. Hatchery operation plans and performance summaries.

Wash. Dep. Fish Wildl., Ann. Rep. 1996, Vol. II, No. 2. (Available from WDFW, 600

Capitol Way N., Olympia, WA 98501-1091.)

Baade, R.T. 1957. Environmental studies of the cutthroat trout, Southeast Alaska. Alaska Game

Comm. Fed. Aid Fish Rest. Proj. F-1-R-6. Alsk. Game Comm. 6(1,2,3): 62-67.

Bagliniére, J.L., G. Maisse, P.Y. Lebail, and A. Nihouarn. 1989. Population dynamics of brown

trout, Salmo trutta L., in a tributary in Brittany (France): spawning and juveniles. J. Fish

Biol. 34:97-110.

Bakun, A. 1973. Coastal upwelling indices, West Coast of North American 1946-1971. U.S.

Dep. of Commerce, NOAA Tech. Rep. NMFS SSRF-671, 103 p. 

Bakun, A. 1975. Daily and weekly upwelling indices, West Coast of North America, 1967-

1973. U.S. Dep. of Commerce, NOAA Tech. Rep. NMFS SSRF-693, 114 p. 

Barbour, M.G., and J. Major (editors). 1977. Terrestrial vegetation of California. Wiley, New

York, 1002p.

Bauer, J. 1998. Affidavit of Jerry Bauer in Support of Plaintiff’s Motion for Summary

Judgment, filed with Plaintiff’s Motion for Summary Judgment in Douglas Co. v Daley,

No. 98-6024-HO (D. Oregon, decided Dec. 14, 1998), June 24, 1998. 3 p. (Available

from Environmental and Technical Services Division, NMFS, 525 NE Oregon St.,

Portland, OR 97232.)

Beamish, R. J., and D.R. Bouillon. 1993. Pacific salmon production trends in relation to

climate. Can. J. Fish. Aquat. Sci. 50(5):1002-1016.
209

Beechie, T., E. Beamer, and L. Wasserman. 1994. Estimating coho salmon rearing habitat and

smolt production losses in a large river basin, and implications for habitat restoration.

N. Am. J. Fish. Manage. 14(4):797-811.

Behnke, R.J. 1972. The systematics of salmonid fishes in recently glaciated lakes. J. Fish. Res.

Board Can. 29:639-671.

Behnke, R.J. 1979. Monograph of the native trouts of the genus Salmo of western North

America. 163 p. (Available Regional Forester, 11177 West 8th Avenue, P.O. Box 25127,

Lakewood, CO 80225.)

Behnke, R.J. 1988. Phylogeny and classification of cutthroat trout. In R.E. Gresswell (ed.),

Status and management of interior stocks of cutthroat trout, p. 1-7. Am. Fish. Soc.

Symp. 4.

Behnke, R.J. 1992. Native trout of western North America. Am. Fish. Soc., Bethesda, 275 p.

Behnke, R.J. 1996. Kamchatkan cutthroats? Trout 37(3):40-41.

Behnke, R.J. 1997. Evolution, systematics, and structure of Oncorhynchus clarki clarki. In J.D.

Hall, P.A. Bisson and R.E. Gresswell (eds.), Sea-run cutthroat trout: biology,

management, and future conservation, p. 3-6. Oregon Chapter, Am. Fish. Soc., Corvallis.

Behnke, R.J., and M. Zarn. 1976. Biology and management of threatened and endangered

western trout. U.S. For. Serv. Gen. Tech. Rep. RM-28, 45 p.

Bell, M.C. 1986. Fisheries handbook of engineering requirements and biological criteria. U.S.

Army Corps of Engineers, Portland, Oregon. Fish Passage Development and Evaluation

Program, North Pacific Division.

Bernard, D.R., K.R. Hepler, J.D. Jones, M.E. Whalen, and D.N. McBride. 1995. Some tests of

the “migration hypothesis” for anadromous Dolly Varden (southern form). Trans. Am.

Fish. Soc. 124:297-307.

Big Eagle & Associates, and LGL Limited (BE and LGL). 1995. Sea-run cutthroat trout catch,

escapement, and historical abundance data. Report prepared for NOAA, NMFS,

Northwest Fisheries Science Center. (Available from NMFS, Northwest Fisheries

Science Center, 2725 Montlake Blvd. E., Seattle, WA 98112.)

Bilby, R.E., B.R. Fransen, and P.A. Bisson. 1996. Incorporation of nitrogen and carbon from

spawning coho salmon into the trophic system of small streams: evidence from stable

isotopes. Can. J. Fish. Aquat. Sci. 53:164-173.
210

Bisson, P.A, and J.R. Sedell. 1984. Salmonid populations in streams in clearcut vs. old-growth

forests of eastern Washington. In W.R. Meehan, Jr., T.R. Merrell and T.A. Hanley (eds.),

Fish and wildlife relationships in old-growth forests, p. 121-129. Institute of Fisheries

Research Biologists, Morehead City, NC.

Bisson, P.A., R.E. Bilby, M.D. Bryant, C.A. Dolloff, G.B. Grette, R.A. House, M.L. Murphy,

K.V. Koski, and J.R. Sedell. 1987. Large woody debris in forested streams in the Pacific

Northwest: past, present, and future. In E.O. Salo and T.W. Cundy (eds.), Streamside

management: forestry and fishery interactions, p. 143-190. Univ. Washington, Institute of

Forest Resources, Seattle.

Bisson, P.A., J.L. Nielsen, R.A. Palmason, and L.E. Grove. 1982. A system of naming habitat

types in small streams, with examples of habitat utilization by salmonids during low

streamflow. In N.B. Armantrout (ed.), Proceedings of a Symposium on the Acquisition

and Utilization of Aquatic Habitat Inventory Information, p. 62-72. The Western

Division, Am. Fish. Soc., Portland, Oregon.

Bjornn, T.R., and D.W. Reiser. 1991. Habitat requirements of salmonids in streams. In W.R.

Meehan (ed.), Influence of forest and rangeland management on salmonid fishes and their

habitats, p. 83-138. Am. Fish. Soc. Spec. Publ. 19, Bethesda.

Bonner, J.T. 1965. Size and cycle: an essay on the structure of biology. Princeton Univ. Press,

Princeton, NJ.

Bortelson, G.C., M.J. Chrzatowski, and P. Hickey. 1980. Historical changes of shoreline and

wetland at eleven major deltas in the Puget Sound region, Washington. Atlas HA-617,

Dep. Interior, U.S. Geological Survey, Wash. D.C.

Boule, M.E., N. Olmstead, and T. Miller. 1983. Inventory of wetland resources to develop an

evaluation of wetland management in Western Washington. Final report to Wash. Dep.

Ecology, Olympia, 102 p.

Bradshaw, A.D. 1965. Evolutionary significance of phenotypic plasticity in plants. Advances in

Genetics 13:115-155.

Bradshaw, W.E. 1986. Pervasive themes in insect life cycle strategies. In F. Taylor and R.

Karban (eds.), The evolution of insect life cycles, p. 261-275. Springer Verlag, London.

Breckon, G.J., and M.G. Barbour. 1974. Review of North American Pacific Coast beach

vegetation. Madrono 22:333-360.

Brody, J. (ed.). 1991. Hood Canal: Splendor at risk. The Sun newspaper. Bremerton, WA,

p. 17-33.

Brown, G.W. 1974. Fish habitat. In Environmental effects of forest residues management in the

Pacific Northwest. U.S. For. Gen. Serv. Gen. Tech. Rep. PNW-24. p. E1-E15.
211

Brown, L.G. 1992. On the zoogeography and life history of Washington’s native charr; Dolly

Varden Salvelinus malma (Walbaum) and bull trout Salvelinus confluentus (Suckley).

Wash. Dep. Wildl., Olympia, WA. Rep. #94-04. (Available from WDFW, 600 Capitol

Way N., Olympia, WA 98501-1091.)

Brown, R.F. 1988. Physical rearing habitat for anadromous salmonids in the Redwood Creek

basin, Humboldt County, California. M.S. Thesis. Humboldt State University, Arcata

CA.

Brusca, R.C., and B.R. Wallerstein. 1979. Zoogeographic patterns of idoteid isopods in the

Northeast Pacific, with a review of shallow water zoogeography of the area. Bull. Biol.

Soc. Wash. 3:67-105.

Bryant, F.G. 1949. A survey of the Columbia River and its tributaries with special reference to

its fishery resources—Part II. Washington streams from the mouth of the Columbia to

and including the Klickitat River (Area I). U.S. Fish. Wildl. Serv. Spec. Sci. Rep. 62,

110 p.

Bryant, G. 1998. Memo from G. Bryant to J. Lecky, C. Wingert, S. Fongner and R. McInnis.

25 May 1998. 18 p. (Available from Environmental and Technical Services Division,

NMFS, 525 NE Oregon St., Portland, OR 97232.)

Bulkley, R.V. 1966. Catch of the 1965 tidewater cutthroat sport fishery and notes on the life

history of the coastal cutthroat trout in the Siuslaw River, Oregon. Research Division,

Oregon Game Commission, Fish. Res. Rep. #4, Oregon State Univ., Corvallis, OR.

Bull, J.J. 1987. Evolution of phenotypic variance. Evolution 41:303-315.

Burgner, R.L., J.T. Light, L. Margolis, T. Okazaki, A. Tautz, and S. Ito. 1992. Distribution and

origins of steelhead trout (Oncorhynchus mykiss) in offshore waters of the North Pacific

Ocean. Int. North Pac. Fish. Comm. Bull. 51:52.

Busack, C.A., and G.A.E. Gall. 1981. Introgressive hybridization in populations of Paiute

cutthroat trout (Salmo clarki seleniris). Can. J. Fish. Aquat. Sci. 38:939-951.

Busack, C., and J.B. Shaklee (eds.). 1995. Genetic diversity units and major ancestral lineages

of salmonid fishes in Washington. Wash. Dep. Fish Wildl., Fish Manage. Prog., Res.

Assess. Div. Tech. Rep. No. RAD 95-02, 188 p. (Available from WDFW, 600 Capitol

Way N., Olympia, WA 98501-1091.)

Busby, P.J., T.C. Wainwright, G.J. Bryant, L. Leirheimer, R.S. Waples, F.W. Waknitz, and I.V.

Lagomarsino. 1996. Status review of west coast steelhead from Washington, Idaho,

Oregon, and California. U.S. Dep. of Commerce, NOAA Tech. Memo. NMFS-NWFSC27, 281 p. 
212

Bustard, D.R, and D.W. Narver. 1975. Preferences of juvenile coho salmon Oncorhynchus

kisutch and cutthroat trout Salmo clarki relative to simulated alteration of winter habitat.

J. Fish. Res. Board Can. 32:681-687.

California Department of Fish and Game (CDFG). 1980-89. Unpubl. data. Annual seining

results. Calif. Dep. Fish Game, Inland Fisheries Admin. Rep., Sacramento, CA. CDFG,

1416-9th St., Sacramento, CA 95814

California Department of Fish and Game (CDFG). 1984-97. Cooperative artificial propagation

programs for salmon and steelhead, series from 1984-1997. Calif. Dep. Fish Game.

Inland Fisheries Administrative Reports, Sacramento, CA. (Available from CDFG,

1416-9th St., Sacramento, CA 95814.)

Campton, D.E. 1995. Genetic effects of hatchery fish on wild populations of Pacific salmon and

steelhead: what do we really know? Am. Fish. Soc. Symp. 15:337-353.

Campton, D.E., and F.M. Utter. 1985. Natural hybridization between steelhead trout (Salmo

gairdneri) and coastal cutthroat trout (Salmo clarki clarki) in two Puget Sound streams.

Can. J. Fish. Aquat. Sci. 42:110-119.

Campton, D.E., and F.M. Utter. 1987. Genetic structure of anadromous cutthroat trout Salmo

clarki clarki populations in the Puget Sound area evidence for restricted gene flow. Can.

J. Fish. Aquat. Sci. 44:573-582.

Canning, D. 1997. Habitat loss and change on Puget Sound shorelines. Puget Sound Notes

40:1-2. Wash. Dep. Ecology.

Caughley, G. 1994. Wildlife ecology and management. Blackwell Sci. Publ., Boston, 334 p.

Cavalli-Sforza, L.L., and A.W.F. Edwards. 1967. Phylogenetic analysis: Models and estimation

procedures. Evolution 21:550-570.

Cederholm, C.J., and W.J. Scarlett. 1982. Seasonal immigrations of juvenile salmonids into four

small tributaries of the Clearwater, Washington, 1977-1981. In E.L. Brannon and E.O.

Salo (eds.), Proceedings of the salmon and trout migratory behavior symposium,

p. 98-110. Univ. Washington, Seattle.

Chakraborty, R. 1980. Gene diversity analysis in nested subdivided populations. Genetics

96:721-726.

Chamberlin, T.W., R.D. Harr, and F.H. Everest. 1991. Timber harvesting, silviculture, and

watershed processes. In W.R. Meehan (ed.), Influence of forest and rangeland

management on salmonid fishes and their habitats, p. 181-205. Am. Fish. Soc. Spec.

Publ. 19, Bethesda.
213

Chilcote, M.C., C. Dale, K. Kostow, H. Schaller, and H. Weeks. 1992. Wild fish management

policy. Oreg. Dep. Fish. Wildl., Portland. Biennial Progress Report, 31 p. (Available

from ODFW, P.O. Box 59, Portland, OR 97207.)

Chilcote, M.W., S.A. Leider, and B.A. Crawford. 1980a. Kalama River salmonid studies 1980.

Wash. Dep. Game, Div. Fish. Manage., 37 p. (Available from WDFW, 600 Capitol Way

N., Olympia, WA 98501-1091.)

Chilcote, M.W., S.A. Leider, and R.P. Jones. 1980b. Kalama River salmonid studies 1980.

Wash. Dep. Game, Div. Fish. Manage. Rep. No. 81-11, 97 p. (Available from WDFW,

600 Capitol Way N., Olympia, WA 98501-1091.)

Clancy, C.G. 1988. Effects of dewatering on spawning by Yellowstone cutthroat trout in

tributaries to the Yellowstone River, Montana. In R.E. Gresswell (ed.), Status and

management of interior stocks of cutthroat trout, p. 37-41. Am. Fish. Soc., Bethesda.

Clarke, W.C., and T. Hirano. 1995. Osmoregulation. In C. Groot, L. Margolis and W.C. Clarke

(eds.), Physiological ecology of Pacific salmon, p. 317-377. UBC Press, Vancouver.

Clemens, W.A., and G.V. Wilby. 1946. Fishes of the Pacific Coast of Canada. Fish. Res. Board

Can. Bull. 68, Ottawa, 368 p.

Climate Diagnostics Center (CDC). 1961-1998. NOAA - CIRES. Boulder, CO. (Available

through Internet, www.cdc.noaa.gov/~cas/climo/polys/alaska.html)

Connolly, P.J. 1997. Influence of stream characteristics and age-class interactions on

populations of coastal cutthroat trout. In J.D. Hall, P.A. Bisson and R.E. Gresswell (eds.),

Sea-run cutthroat trout: biology, management, and future conservation, p. 173-174. Am.

Fish. Soc., Corvallis.

Cook, F.R. 1984. Introduction to Canadian amphibians and reptiles. National Museum of

Natural Sciences, National Museums of Canada, Ottawa, 200 p.

Cooper, E.L. 1970. Growth of cutthroat trout (Salmo clarki) in Chef Creek, Vancouver Island,

British Columbia. J. Fish. Res. Board Can. 27:2063-2070.

Cramer, F.K. 1940. Notes on the natural spawning of cutthroat trout Salmo clarkii clarkii in

Oregon. Proceedings of the Sixth Pacific Science Conference of the Pacific Science

Association 3:335-339.

Cramer, S.P. 1998. Risk of extinction for cutthroat trout in the Umpqua Basin. S.P. Cramer &

Associates, Inc. Submitted to Ronald Yokum, Attorney. (Available from Environmental

and Technical Services Division, NMFS, 525 NE Oregon St., Portland, OR 97232.)
214

Crawford, B.A. 1979. The origin and history of the trout broodstocks of the Washington

Department of Game, Olympia, Washington. Wash. Dep. Game, 76 p. (Available from

WDFW, 600 Capitol Way N., Olympia, WA 98501-1091.)

Crow, J.F., and M. Kimura. 1970. An introduction to population genetics theory. Harper and

Row Publ., New York, 591 p.

Currens, K.P., C.B. Schreck, and H.W. Li. 1990. Allozyme and morphological divergence of

rainbow trout (Oncorhynchus mykiss) above and below waterfalls in the Deschutes River,

Oregon. Copeia 1990(3):730-746.

Dahl, T.E. 1990. Wetlands losses in the United States 1780s to 1980s. U.S. Dep. of the Interior,

Fish Wildl. Serv., Wash. D.C., 13 p.

Dawley, E.M., C.W. Sims, and R.D. Ledgerwood. 1978. A study to define the migrational

characteristics of chinook and coho salmon and steelhead trout in the Columbia River

Estuary. 1978, Annual Report to Pacific Northwest Regional Commission, 23 p. 

(Available from Environmental and Technical Services Division, NMFS, 525 NE Oregon

St., Portland, OR 97232.)

Dawley, E.M., C.W. Sims, R.D. Ledgerwood, D.R. Miller, and F.P. Thrower. 1979. A study to

define the migrational characteristics of chinook and coho salmon and steelhead trout in

the Columbia River Estuary. 1979, Annual Report to Pacific Northwest Regional

Commission, 90 p. (Available from Environmental and Technical Services Division,

NMFS, 525 NE Oregon St., Portland, OR 97232.)

Dawley, E.M., C.W. Sims, R.D. Ledgerwood, D.R. Miller, and J.G. Williams. 1980. A study to

define the migrational characteristics of chinook and coho salmon and steelhead trout in

the Columbia River Estuary. 1979, Annual Report to Pacific Northwest Regional

Commission, 53 p. (Available from Environmental and Technical Services Division,

NMFS, 525 NE Oregon St., Portland, OR 97232.)

den Boer, P.J. 1968. Spreading the risk and stabilization of animal numbers. Acta Biotheor.

18:165-194.

DeWitt, J.W. 1954. A survey of the coastal cutthroat trout, Salmo clarki clarki Richardson, in

California. Calif. Fish Game 40:329-335.

Dill, L.M. 1983. Adaptive flexibility in the foraging behavior of fishes. Can. J. Fish. Aquat. Sci.

40:398-408.

Dimick, R.E., and F. Merryfield. 1945. The fishes of the Willamette River system in relation to

pollution. Oregon State College, Engineering Experiment Station. Bulletin 20, 23 p.
215

Donaldson, L.R. 1947. Letter to D. Clark, Washington Department of Game, 8 April 1947.

(Available from Environmental and Technical Services Division, NMFS, 525 NE Oregon

St., Portland, OR 97232.)

Duff, R.L. 1972. The 1969-70 and 1970-71 sea-run cutthroat tagging and evaluation study at

the Cowlitz Trout Hatchery. Wash. Dep. Game. Fish. Manage. Div. Rep.,

26 p. (Available from WDFW, 600 Capitol Way N., Olympia, WA 98501-1091.)

Dunham, J. 1998. Unpubl. data. Memo from J. Dunham to O. Johnson. 28 Sept. 1998. 6 p.

(Available from Environmental and Technical Services Division, NMFS, 525 NE Oregon

St., Portland, OR 97232.)

Dwyer, W.P., and R.H. Kramer. 1975. The influence of temperature on scope for activity in

cutthroat trout, Salmo clarki. Trans. Am. Fish. Soc. 4:552-554.

Ebbesmeyer, C.C., and R.M. Strickland. 1995. Oyster condition and climate: Evidence from

Willapa Bay. Washington Sea Grant Program, Univ. Washington, Seattle, Publ.

WSG-MR 95-02, 11 p.

Edie, B.G. 1975. A census of the juvenile salmonids of the Clearwater River basin, Jefferson

County, Washington, in relation to logging. M.S. Thesis, Univ. Washington, Seattle,

86 p.

Environment Canada (EC). 1977. Water temperatures: British Columbia and Yukon Territory.

Inland Waters Directorate. Water Resources Branch, Vancouver, Canada, 1874 p.

Environment Canada (EC). 1991. HYDAT: Surface water data to 1990. Version CD Rom 3.0.

Ottawa: Environment Canada, Inland Waters Directorate, Water Resources Branch.

Environment Canada (EC). 1996. 1961-1990 Canadian Climate Normals. Canadian

Meteorological Centre, climate and water information. Climate and Water Products Div.,

Downsview, Ontario. (Available through Internet, www.cmc.ec.gc.ca)

Everitt, B.S. 1978. Graphical techniques for multivariate data. North Holland, New York.

Fagen, R., and W.W. Smoker. 1989. How large-capacity hatcheries can alter interannual

variability of salmon production. Fish. Res. 8:1-11.

Falconer, D.S. 1989. Introduction to quantitative genetics 3rd ed. Longman Scientific &

Technical, Harlow, Essex, U.K., 438 p.

Farley, A.L. 1979. Atlas of British Columbia. UBC Press, Vancouver, 136 p.

Fausch, K.D., and T.G. Northcote. 1992. Large woody debris and salmonid habitat in a small

coastal British Columbia stream. Can. J. Fish. Aquat. Sci. 49(4):682-693.
216

Fausch, K.D., and M.K. Young. 1995. Evolutionarily significant units and movement of resident

stream fishes: a cautionary tale. In J.L. Nielsen (ed.), Evolution and the aquatic

ecosystem: defining unique units in population conservation, p. 360-370. Am. Fish. Soc.

Symp. 17, Bethesda, MD.

Ferguson, M.M., R.G. Danzmann, and F.W. Allendorf. 1985. Absence of developmental

incompatibility in hybrids between rainbow trout and two subspecies of cutthroat trout.

Biochem. Genet. 23(7-8):557-570.

Ferguson, M.M., R.G. Danzmann, and F.W. Allendorf. 1988. Developmental success of hybrids

between two taxa of salmonid fishes with moderate structural gene divergence. Can. J.

Zoo. 66:1389-1395.

Fish Commission of Oregon (FCO), and Oregon State Game Commission (OSGC). 1946. The

Umpqua River study. Joint Report, 33 p. (Available from ODFW, P.O. Box 59,

Portland, OR 97207.)

Fisk, T.A., E. Gerstung, and J. Thomas. 1966. Stream damage surveys-1966. California Dep.

Fish Game, Sacremento. Inland Fish. Div., Admin. Rep. 66-10, 15 p.

Flagg, T.A., F.W. Waknitz, D.J. Maynard, G.B. Milner, and C.V. Mahnken. 1995. The effect of

hatcheries on native coho salmon populations in the lower Columbia River. In H.

Schramm and B. Piper (eds.), Proceedings of the American Fisheries Society Symposium

on the uses and effects of cultured fishes in aquatic ecosystems, March 1-17, 1994,

p. 366-375. Am. Fish. Soc. Symp. 15, Albuquerque, NM.

Foerster, R.E. 1968. The sockeye salmon, Oncorhynchus nerka. Bull. Fish. Res. Board Can.

162, 422 p.

Folmar, L.C., and W.W. Dickhoff. 1980. The parr-smolt transformation (smoltification) and

seawater adaptation salmonids. A review of selected literature. Aquaculture 21:1-37.

Folmar, L.C., and W.W. Dickhoff. 1981. Evaluation of some physiological parameters as

predictive indices of smoltification. Aquaculture 23:309-324.

Fontaine, M. 1975. Physiological mechanisms in the migration of marine and amphihaline fish.

Adv. Mar. Biol. 13:241-355.

Foote, C.J., and P.A. Larkin. 1988. The role of male choice in the assortative mating of

anadromous and non-anadromous sockeye salmon (Oncorhynchus nerka). Behaviour

106(1-2):43-61.

Foote, C.J., C.C. Wood, and R.E. Withler. 1989. Biochemical genetic comparison of sockeye

salmon and kokanee, the anadromous and nonanadromous forms of Oncorhynchus nerka.

Can. J. Fish. Aquat. Sci. 46(1):149-158.
217

Forest Ecosystem Management Assessment Team (FEMAT). 1993. A Federal Agency guide

for pilot watershed analysis. Vers.1.2. Interagency Working Group. U.S. Dep. of

Agriculture, For. Serv., Portland, OR.

Franklin, J.F., and C.T. Dyrness. 1973. Natural vegetation of Oregon and Washington. U.S. For.

Serv. Gen. Tech. Rep. PNW-8, 417 p. U.S. Gov. Printing Office, Washington, D.C.

Fuss, H.J. 1978. Some life history characteristics obtained by scale analysis of sea-run cutthroat

trout (Salmo clarki clarki) from streams near Forks, Washington. In J.R. Moring (ed.),

Proceedings of the Wild Trout-Catchable Trout Symposium, p. 127-133. Oregon Dep.

Fish Wildl., Portland.

Fuss, H.J. 1982. Age, growth and instream movement of Olympic Peninsula coastal cutthroat

trout (Salmo clarki clarki). M.S. Thesis, Univ. Washington, Seattle, 128 p.

Fuss, H.J., and C. Ashbrook. 1995. Hatchery operation plans and performance summaries.

Volume I, Number 2, Puget Sound. Wash. Dep. Fish Wildl. Ann. Rep. 1995. (Available

from WDFW, 600 Capitol Way N., Olympia, WA 98501-1091.)

Gale, D.B. 1996. 1996 Blue Creek summer snorkel surveys. Yurok Tribal Fisheries Program.

Habitat Assessment and Biological Monitoring Division, Stream survey memo., Klamath,

CA. (Available from Environmental and Technical Services Division, NMFS, 525 NE

Oregon St., Portland, OR 97232.)

Gale, D.B. 1997. 1997 Blue Creek summer snorkel surveys. Yurok Tribal Fisheries Program.

Habitat Assessment and Biological Monitoring Division, Stream survey memo., Klamath,

CA. (Available from Environmental and Technical Services Division, NMFS, 525 NE

Oregon St., Portland, OR 97232.)

Gale, D.B. 1998. Memo from the Yurok Tribal Fisheries Program. State fisheries biologist to

R. Waples. 25 Sept. 1998, 6 p. (Available from Environmental and Technical Services

Division, NMFS, 525 NE Oregon St., Portland, OR 97232.)

Garrett, A.M. 1998. Interstream movements of coastal cutthroat trout (Oncorhynchus clarki

clarki) in the Clearwater River, Jefferson County, Washington. M.E.S. Thesis, The

Evergreen State College, Olympia, WA, 212 p.

Gerstung, E.R. 1997. Status of coastal cutthroat trout in California. In J.D. Hall, P.A. Bisson and

R.E. Gresswell (eds.), Sea-run cutthroat trout: biology, management, and future

conservation, p. 43-56. Am. Fish. Soc., Corvallis.

Gerstung, E.R. 1998. Status of coastal cutthroat trout in California plus appendices. California

Dep. Fish Game, Inland Fisheries Division. (Available from CDFG, 1416-9th St.,

Sacramento, CA 95814.)
218

Giger, R.D. 1972. Ecology and management of coastal cutthroat trout in Oregon. Oregon State

Game Comm., Corvallis. Fish. Res. Rep. No. 6, 61 p.

Gilpin, M.E., and M.E. Soulé. 1986. Minimum viable populations: Processes of species

extinction. In M.E. Soulé (ed.), Conservation biology: The science of scarcity and

diversity, p. 19-34. Sinauer Assoc., Sunderland, MA.

Glova, G.J. 1978. Pattern and mechanism of resource partitioning between stream populations

of juvenile coho salmon (Oncorhynchus kisutch) and coastal cutthroat trout

(Oncorhynchus clarki clarki). Ph.D. Dissertation, Univ. B.C., 185 p.

Glova, G.J. 1984. Management implications of the distribution and diet of sympatric

populations of juvenile coho salmon and coastal cutthroat trout in small streams in British

Columbia, Canada. Prog. Fish Cult. 46:269-277.

Glova, G.J. 1986. Interaction for food and space between experimental populations of juvenile

coho salmon (Oncorhynchus kisutch) and coastal cutthroat trout (Salmo clarki) in a

laboratory stream. Hydrobiologia 132:155-168.

Glova, G.J. 1987. Comparison of allopatric cutthroat trout stocks with those sympatric with

coho salmon and sculpins in small streams. Environ. Biol. Fishes 20:275-284.

Glova, G.J., and J.C. Mason. 1976. Interactive ecology of juvenile salmon and trout in streams.

Fish. Res. Board Can., Pacific Biological Station, Nanaimo, B.C. Manuscr. Rep. Ser.

1391, 24 p.

Glova, G.J, and J.C. Mason. 1977. Interactions for food and space between sympatric

populations of underyearling coho salmon and coastal cutthroat trout in a stream

simulator during spring. Fish. Res. Board Can., Nanaimo, B.C. Manuscr. Rep. Ser. 1428,

36 p.

Gold, J.R. 1977. Systematics of western North American trout (Salmo), with notes on the

redband trout of Sheepheaven Creek, California. Can. J. Zool. 55(11):1858-1873.

Gold, J.R., J.C. Avise, and G.A.E. Gall. 1977. Chromosome cytology in the cutthroat trout

series Salmo clarki (Salmonidae). Cytologia 42:377-382.

Golden, J.T. 1975. Lethal temperatures for coastal cutthroat trout under fluctuating temperature

regimes. Oreg. Dep. Fish Wildl. Report. Unpubl. manuscr., 7 p. (Available from Oregon

Dept. Fish Wildl., P.O. Box 59, Portland, OR 97201.)

Gonor, J.J., J.R. Sedell, and P.A Benner. 1988. What we know about large trees in estuaries, in

the sea, and on coastal beaches. In C. Maser, R.F. Tarrant, J.M. Trappe and J.F. Franklin

(eds.), From the forest to the sea: A story of fallen trees, p. 83-112. U.S. For. Serv., Gen.

Tech. Rep. PNW-GTR-229.
219

Gotshall, D.W., G.H. Allen, and R.A. Barnhart. 1980. An annotated checklist of fishes from

Humboldt Bay, California. Calif. Fish Game 66:220-232.

Gowan, C., M.K. Young, K.D. Fausch, and S.C. Riley. 1994. Restricted movement in resident

stream salmonids: a paradigm lost? Can. J. Fish. Aquat. Sci. 51:2626-2637.

Gregory, S.V., and P.A. Bisson. 1997. Degradation and loss of anadromous salmonid habitat in

the Pacific Northwest. In D.J. Stouder, P.A. Bisson and R.J. Naiman (eds.), Pacific

salmon and their ecosystems: status and future options, p. 277-314. Chapman and Hall,

New York.

Gregory, S.V, F.J. Swanson, and W.A. McKee. 1991. An ecosystem perspective of riparian

zones. Bioscience 40:540-551.

Gresswell , R.E. (ed.). 1988. Status and management of interior stocks of cutthroat trout. Am.

Fish. Soc. Symp. 4.

Gresswell, R.E., and R.D. Harding. 1997. The role of special angling regulations in

management of coastal cutthroat trout. In J.D. Hall, P.A. Bisson and R.E. Gresswell

(eds.), Sea-run cutthroat trout: biology, management, and future conservation, p. 151-156.

Am. Fish. Soc., Corvallis.

Gresswell, R.E., and J.D. Varley. 1988. Effects of a century of human influence on the cutthroat

trout of Yellowstone Lake. In R.E. Gresswell (ed.), Status and management of interior

stocks of cutthroat trout, p. 45-52. Am. Fish. Soc. Symp. 4.

Gresswell, R.E., W.J. Liss, and G.L. Larson. 1994. Life-history organization of Yellowstone

cutthroat trout (Oncorhynchus clarki bouvieri) in Yellowstone Lake. Can. J. Fish. Aquat.

Sci. 51(Suppl. 1):298-309.

Griffith, J.S. 1988. Review of competition between cutthroat trout and other salmonids. In R.E.

Gresswell (ed.), Status and management of interior stocks of cutthroat trout, p. 134-140,

Am. Fish. Soc. Symp. 4.

Griswold, K.E. 1996. Genetic and meristic relationships of coastal cutthroat trout

(Oncorhynchus clarki clarki) residing above and below barriers in two coastal basins.

M.S. Thesis, Oregon State Univ., Corvallis, OR, 83 p.

Gross, M.R. 1984. Sunfish, salmon, and the evolution of alternative reproductive strategies and

tactics in fishes. In G. Potts and R. Wootton (eds.), Fish reproduction: strategies and

tactics, p. 55-75. Academic Press, London, England.

Gross, M.R. 1987. Evolution of diadromy in fishes. In M.J. Dadswell, R.J. Klauda, C.M.

Moffitt, R.L. Saunders, R.A. Rulifson, and J.E. Cooper (eds.), Am. Fish. Soc. Symp. 1,

p. 14-25, Boston.
220

Gustafson, R.G., T.C. Wainwright, G.A. Winans, F.W. Waknitz, L.T. Parker, and R.S. Waples.

1997. Status review of sockeye salmon from Washington and Oregon. U.S. Dep. of

Commerce, NOAA Tech. Memo. NMFS-NWFSC-33, 282 p.

Gyllensten, U., R.F. Leary, R.W. Allendorf, and A.C. Wilson. 1985. Introgression between two

cutthroat trout subspecies with substantial karyotypic, nuclear and mitochondrial genomic

divergence. Genetics 111:905-915.

Hall, C.A. 1964. Shallow-water marine climates and molluscan provinces. Ecology

45(2):226-234.

Hall, J.D., P.A. Bisson, and R.E. Gresswell (eds.). 1997. Sea-run cutthroat trout: biology,

management, and future conservation. Am. Fish. Soc., Corvallis, 183 p.

Hall, J.D., M.L. Murphy, and R.S. Aho. 1978. An improved design for assessing impacts of

watershed practices on small streams. Int. Ver. Theor. Angew. Limno. Verh.

20:1359-1365.

Hanratty, P. Unpubl. data. Coastal cutthroat trout adult trap data from the Hoquim River, and

smolt data from Bingham Creek and Stevens Creek (a tributary to the Humptulips).

(Available from WDFW, 600 Capitol Way N., Olympia, WA 98501-1091.)

Hansler, D.D. 1958. Some effects of artificial selection upon a stock of cutthroat trout, Salmo

clarki, with related hybridization studies. M.S. Thesis, Univ. Washington, Seattle, WA.

Hanson, D.L. 1977. Habitat selection and spatial interaction in allopatric populations of

cutthroat and steelhead trout. Ph.D. Dissertation, Univ. Idaho, Moscow.

Harcup, M.F., R. Williams, and D.M. Ellis. 1984. Movements of brown trout, Salmo trutta L.,

in the River Gwyddon, South Wales. J. Fish Biol. 24:415-426.

Hard, J.J. 1995. A quantitative genetic perspective on the conservation of intraspecific diversity.

In J.L. Nielsen (ed.), Evolution and the aquatic ecosystem: defining unique units in

population conservation, Am. Fish. Soc. Symp. 17, p. 304-326. Bethesda, MD.

Hard, J.J., and W.K. Hershberger. 1995. Quantitative genetic consequences of captive

broodstock programs for anadromous Pacific salmon (Oncorhynchus spp.). p. 2-1 - 2-75.

(Available Bonneville Power Administration (Project No. 93 56), P. O. Box 3621,

Portland, OR, 97208-3621.)

Hard, J.J., R.P. Jones, Jr., M.R. Delarm, and R.S. Waples. 1992. Pacific salmon and artificial

propagation under the Endangered Species Act. NOAA Tech. Memo., NMFS-NWFSC2, 56 p. (Available from Environmental and Technical Services Division, NMFS, 525

NE Oregon St., Portland, OR 97232.)
221

Hard, J.J., R.G. Kope, W.S. Grant, F.W. Waknitz, L.T. Parker, and R.S. Waples. 1996. Status

review of pink salmon from Washington, Oregon, and California. U.S. Dep. of

Commerce, NOAA Tech. Memo. NMFS-NWFSC-25, 131 p.

Hartman, G.F., and T.G. Brown. 1987. Use of small, temporary, floodplain tributaries by

juvenile salmonids in a west coast rain-forest drainage basin, Carnation Creek, British

Columbia. Can. J. Fish. Aquat. Sci. 44:262-270.

Hartman, G.F., and C.A. Gill. 1968. Distribution of juvenile steelhead and cutthroat trout

(Salmo gairdneri and S. clarki clarki) within streams in southwestern British Columbia.

J. Fish. Res. Board Can. 25(1):33-48.

Hartman, G.F., and J.C. Scrivener. 1990. Impacts of forestry practices on a coastal stream

ecosystem, Carnation Creek, British Columbia. Can. Bull. Fish. Aquat. Sci. 223:148.

Hartman, G.F., L.B. Holtby, and J.C. Scrivener. 1984. Some effects of natural and loggingrelated winter stream temperature changes on the early life history of coho salmon

(Oncorhynchus kisutch) in Carnation Creek, British Columbia. In W.R. Meehan, Jr., T.R.

Merrill, and T.A. Hanley (eds.), Fish and wildlife relationships in old-growth forests,

 p. 141-149. Am. Instit. Fish. Biol.

Hawkins, D.K. 1997. Hybridization between coastal cutthroat trout (Oncorhynchus clarki

clarki) and steelhead (O. mykiss). Ph.D. Dissertation, Univ. Washington, Seattle, 167 p.

Hawkins, D.K., and T.P. Quinn. 1996. Critical swimming velocity and associated morphology

of juvenile coastal cutthroat trout (Oncorhynchus clarki clarki), steelhead trout

(Oncorhynchus mykiss), and their hybrids. Can. J. Fish. Aquat. Sci. 53:1487-1496.

Hayden, B.P., and R. Dolan. 1976. Coastal marine fauna and marine climates of the Americas.

J. Biogeogr. 3:71-81.

Hayes, D.B., C.P. Ferreri, and W.W. Taylor. 1996. Active fish capture methods. In B.R.

Murphy and D.W. Willis (eds.), Fisheries techniques, Second Ed., p. 193-220. Am. Fish.

Soc., Bethesda.

Healey, M.C. 1991. Diets and feeding rates of juvenile pink, chum, and sockeye salmon in

Hecate Strait, British Columbia. Trans. Am. Fish. Soc. 120(3):303-318.

Heath, W.G. 1963. Thermoperiodism in sea-run cutthroat trout Salmo clarki clarki. Science

142:486-488.

Heggenes, J., T.G. Northcote, and A. Peter. 1991. Spatial stability of cutthroat trout

(Oncorhynchus clarki) in a small, coastal stream. Can. J. Fish. Aquat. Sci. 48:757-762.

Hillis, D.M., C. Moritz, and B.K. Mable (eds.). 1996. Molecular Systematics. Second edition.

Sinauer Assoc., Sunderland, MA, 588 p.
222

Hindar, K., B. Jonsson, N. Ryman, and G. Ståhl. 1991. Genetic relationships among landlocked,

resident, and anadromous brown trout, Salmo trutta L. Heredity 66:83-91.

Hisata, J.S. 1971. An evaluation of stocking hatchery reared sea-run cutthroat trout, (Salmo

clarki clarki) in some tributary streams of Hood Canal. Wash. Dep. of Game. Job Prog.

Rep. AFS 44-1, May, 1970 to June, 1971. (Available from WDFW, 600 Capitol Way N.,

Olympia, WA 98501-1091.)

Hisata, J.S. 1973. An evaluation of stocking semi-natural pond reared sea-run cutthroat trout in

streams of Hood Canal, Washington State. Wash. State Dep. Game. Job Completion

Rep. AFS 44-1,2, Olympia, WA, 38 p. (Available from WDFW, 600 Capitol Way N.,

Olympia, WA 98501-1091.)

Holtby, L.B. 1987. The effects of logging on the coho salmon of Carnation Creek, British

Columbia. In T.W. Chamberlin (ed.), Proceedings of the workshop: Applying 15 years

of Carnation Creek results, p. 159-174. Pacific Biological Station, Nanaimo, B.C.

Hooton, R. 1997. Status of coastal cutthroat trout in Oregon. In J.D. Hall, P.A. Bisson and R.E.

Gresswell (eds.), Sea-run cutthroat trout: biology, management, and future conservation,

p. 57-67. Am. Fish. Soc., Corvallis.

Horn, M.H., and L.G. Allen. 1978. A distributional analysis of California coastal marine fishes.

J. Biogeogr. 5:23-42.

Howard, C., and P. Albro. 1995. Mill Creek report. Habitat and fisheries analysis. Rellim

Redwood, Crescent City, CA. (Available from Rellim Redwood Co., P.O. Box 247,

Crescent City, CA 95531-0247)

Howard, C., and P. Albro. 1997. Juvenile outmigrant monitoring program. Rellim Redwood,

Crescent City, CA. (Available from Rellim Redwood Co., P.O. Box 247, Crescent City,

CA 95531-0247)

Hughes, R.M., E. Rexstad, and C.E. Bond. 1987. The relationship of aquatic ecoregions, river

basins, and physiographic provinces to the ichthyogeographic regions of Oregon. Copeia

1987:423-432.

Hunter, J.W. 1973. A discussion of gamefish in the State of Washington as related to water

requirements. Wash. Dep. Game, Olympia. (Available from WDFW, 600 Capitol Way

N., Olympia, WA 98501-1091.)

Hunter, J. Unpubl. data. Life history data from Southwest Washington, 1986-1998. Wash. Dep.

Fish Wildl., Olympia, 15 p. (Available from Environmental and Technical Services

Division, NMFS, 525 NE Oregon St., Portland, OR 97232.)
223

Hutchinson, I., A.C. Prentice, and G. Bradfield. 1989. Aquatic plant resources of the Strait of

Georgia. In K. Vermeer and R.W. Butler (eds.), The ecology and status of marine and

shoreline birds in the Strait of Georgia, British Columbia, Spec. Publ., Can. Wildl. Serv.

Hydrosphere Data Products, Inc. 1993. Hydrodata Regional CD-ROMs: U.S. Geological

Survey daily values. Vols. West 1, West 2. (Available from Hydrosphere Data Products

Inc., 1002 Walnut, Suite 200, Boulder, CO 80302.)

Jaenicke, H.W., and A.G. Celewycz. 1994. Marine distribution and size of juvenile Pacific

salmon in Southeast Alaska and northern British Columbia. Fish. Bull., U.S. 92:79-90.

Johnson, J.E. 1987. Protected fishes of the United States and Canada. Am. Fish. Soc.,

Bethesda, MD, 42 p.

Johnson, O.W., W.S. Grant, R.G. Kope, K. Neely, F.W. Waknitz, and R.S. Waples. 1997.

Status review of chum salmon from Washington, Oregon, and California. U.S. Dep. of

Commerce, NOAA Tech. Memo. NMFS-NWFSC-32, 280 p.

Johnson, O.W., R.S. Waples, T.C. Wainwright, K.G. Neely, F.W. Waknitz, and L.T. Parker.

1994. Status review for Oregon’s Umpqua River sea-run cutthroat trout. U.S. Dep. of

Commerce, NOAA Tech. Memo. NMFS-NWFSC-15, 122 p.

Johnson, S. Unpubl. data. Coastal cutthroat trout smolt and abundance data from Tenmile and

Cummins Creeks (1992-1998) and selected coastal streams (1997-1998) on the Oregon

Coast. Memo to M. Ruckelshaus, July, 1998. 8 p. ODFW, P.O. Box 59, Portland, OR

97207.

Johnson, S.W., J. Heifetz, and K.V. Koski. 1986. Effects of logging on the abundance and

seasonal distribution of juvenile steelhead in some southeastern Alaska streams. N. Am.

J. Fish. Manage. 6:532-537.

Johnston, J.M. 1979. Sea-run cutthroat Stillaguamish River creel census (1978) and harvest

recommendations. Wash. Dep. Game. Fish. Res. Rep., Olympia, WA, 43 p. (Available

from WDFW, 600 Capitol Way N., Olympia, WA 98501-1091.)

Johnston, J.M. 1982. Life histories of anadromous cutthroat with emphasis on migratory

behavior. In E.L. Brannon and E.O. Salo (eds.), Proceedings of the salmon and trout

migratory behavior symposium, p. 123-127. Univ. Washington, Seattle.

Johnston, J.M., and S.P. Mercer. 1976. Sea-run cutthroat in saltwater pens — broodstock

development and extended juvenile rearing (with life history compendium). Wash. Dep.

Game. Fish. Res. Rep., Project AFS-57-1, Olympia, WA, 92 p. (Available from WDFW,

600 Capitol Way N., Olympia, WA 98501-1091.)

Jones, D.E. 1972. Sport fish studies. A study of steelhead-cutthroat trout in Alaska. Alsk. Dep.

Fish Game. Ann. Prog. Rep., Vol. 14, p. 91-108.
224

Jones, D.E. 1973. Steelhead and sea-run cutthroat trout life history in Southeast Alaska. Alsk.

Dep. Fish Game. Ann. Prog. Rep., Vol. 14, Project AFS-42 (AFS-42-1), 18 p.

Jones, D.E. 1974. The study of cutthroat-steelhead in Alaska. Alsk. Dep. Fish Game. Ann.

Prog. Rep., Vol. 15, Project AFS-42 (AFS-42-2):15-31.

Jones, D.E. 1975. Steelhead and sea-run cutthroat trout life history study in Southeast Alaska.

Alsk. Dep. Fish Game. Ann. Prog. Rep., Vol. 16, Project AFS-42 (AFS-42-3-B):23-55.

Jones, D.E. 1976. Steelhead and sea-run cutthroat trout life history in Southeast Alaska. Alsk.

Dep. Fish Game, Ann. Prog. Rep., Vol. 17, Project AFS-42 (AFS-42-4-B): 29-52.

Jones, D.E. 1977. A study of cutthroat and steelhead in Alaska. Life history of sea-run

cutthroat trout. Alsk. Dep. Fish Game. Ann. Prog. Rep., Vol. 18, Project AFS-42 (AFS42-5-B): 78-105.

Jones, D.E. 1978. A study of cutthroat and steelhead in Alaska. Alsk. Dep. Fish Game.

Anadromous Fish Studies, Vol. 19, Study AFS-42 (AFS 42-5-B): 78-105.

Jones, J.D., and C.L. Siefert. 1997. Distribution of mature sea-run cutthroat trout overwintering

in Auke Lake and Lake Eva in southeastern Alaska. In J.D. Hall, P.A. Bisson and R.E.

Gresswell (eds.), Sea-run cutthroat trout: biology, management, and future conservation,

p. 27-28. Am. Fish. Soc., Corvallis.

Jonsson, B. 1982. Diadromous and resident trout Salmo trutta: is their difference due to

genetics? Oikos 38:297-300.

Jonsson, B. 1985. Life history patterns of freshwater resident and sea-run migrant brown trout

in Norway. Trans. Am. Fish. Soc. 114:182-194.

Jonsson, B., and N. Jonsson. 1993. Partial migration: niche shift versus sexual maturation in

fishes. Rev. Fish Biol. Fish. 3:348-365.

Jonsson, B., K. Hindar, and T.G. Northcote. 1984. Optimal age at sexual maturity of sympatric

and experimentally allopatric cutthroat trout and Dolly Varden charr. Oecologia

61:319-325.

June, J.A. 1981. Life history and habitat utilization of cutthroat trout (Salmo clarki) in a

headwater stream on the Olympic Peninsula, Washington. M.S. Thesis, Univ.

Washington, Seattle, 112 p.

Kaeriyama, M., S. Urawa, and T. Suzuki. 1992. Anadromous sockeye salmon (Oncorhynchus

nerka) derived from nonanadromous kokanees: Life history in Lake Toro. Sci. Rep.

Hokkaido Salmon Hatchery 46:157-174.
225

Kaplan, R.H., and W.S. Cooper. 1984. The evolution of developmental plasticity in

reproductive characteristics: an application of the “adaptive coin flipping” principle. Am.

Nat. 123:393-410.

Kathey, K.S. 1994. An evaluation of the utility of a citizen shoreline survey to shoreline

management plan development on Bainbridge Island, Washington. M.S. Thesis, Univ.

Wash., Seattle, 108 p.

Kaya, C.M. 1977. Reproductive biology of rainbow and brown trout in a geothermally heated

stream: The Firehole River of Yellowstone National Park. Trans. Am. Fish. Soc.

106(4):354-361.

Kaya, C.M. 1978. Thermal resistance of rainbow trout from a permanently heated stream, and

of two hatchery strains. Prog. Fish-Cult. 40(4):138-142.

Kellogg, E. (ed.). 1992. Coastal temperate rain forests: Ecological characteristics, status and

distribution worldwide. Ecotrust and Conservation International, Portland, OR and

Wash. D.C.

Kirpichnikov, V.S. 1981. Genetic bases of fish selection. Springer Verlag, New York.

Knudsen, P. 1980. Variability of sea-run cutthroat (Salmo clarki clarki) scale analysis. In J.J.

DeShazo (ed.), Sea-run cutthroat status report. #80-14, p. 225-237. Wash. Game Dep.,

Fish. Manage. Div. (Available from WDFW, 600 Capitol Way N., Olympia, WA 98501-

1091.)

Kostow, K. (ed.). 1995. Biennial report on the status of wild fish in Oregon. Internal Rep.

Oreg. Dep. Fish Wildl., P.O. Box 59, Portland, OR 97207.

Kraemer, C. Unpubl. data. Life history and abundance estimates from the Skagit River and

Snohomish River, 1997. (Available from WDFW, 16018 Mill Creek, Blvd., Mill Creek,

WA 98012-1296.)

Kreissman, B. 1991. California, an environmental atlas and guide. Bear Klaw Press, Davis,

CA.

Kruskal, J.B. 1964. Multidimensional scaling by optimizing goodness of fit to a nonmetric

hypothesis. Psychrometrika 28:1-27.

Kruzic, L. 1998a. Ecology of juvenile coho salmon within the Upper South Umpqua River

basin, Oregon. M.S. Thesis, Univ. Idaho, Moscow, 97 p.

Kruzic, L. 1998b. Unpubl. manuscr. Summary of cutthroat trout data from studies conducted

within the upper south Umpqua River Basin from 1991-96. (Available from

Environmental and Technical Services Division, NMFS, 525 NE Oregon St., Portland,

OR 97232.)
226

Lauman, J.E., K.E. Thompson, and J.D. Fortune, Jr. 1972. Fish and Wildlife resources of the

Umpqua Basin, Oregon, and their water requirements. Completion Report to the Oregon

State Water Resources Board, Oregon State Game Comm., Portland. Project F-69-R-6,

Job 6, 127 p.

Lavier, D. 1963. The sea-run cutthroat. Wash. Game Dep. Bull 15(3):4.

Lawson, P.W. 1993. Cycles in ocean productivity, trends in habitat quality, and the restoration

of salmon runs in Oregon. Fisheries 18(8):6-10.

Leary, R. F., F.W. Allendorf, S.R. Phelps, and K.L. Knudsen. 1987. Genetic divergence and

identification of seven cutthroat trout subspecies and rainbow trout. Trans. Am. Fish.

Soc. 116:580-587.

Leider, S.A. 1997. Status of sea-run cutthroat trout in Washington. In J.D. Hall, P.A. Bisson

and R.E. Gresswell (eds.), Sea-run cutthroat trout: biology, management, and future

conservation, p. 68-76. Am. Fish. Soc., Corvallis.

Leonard, W.P., H.A. Brown, L.L. Jones, K.R. McAllister, and R.M. Storm. 1993. Amphibians

of Washington and Oregon. Seattle Audubon Society, Seattle, 168 p.

Lessa, E.P. 1990. Multidimensional analysis of geographic genetic structure. Syst. Zool.

39:242-252.

Levings, C.D., and R.M. Thom. 1994. A description of the fish community of the Squamish

River estuary, British Columbia: Relative abundance, seasonal changes and feeding

habits of salmonids. Can. Fish. Mar. Serv. Manuscr. Rep. 1475, 63 p.

Lichatowich, J.A., and J.D. McIntyre. 1987. Use of hatcheries in the management of Pacific

anadromous salmonids. In M.J. Dadswell, R.J. Klauda, C.M. Moffitt, R.L. Saunders,

R.A. Rulifson, and J.E. Cooper (eds.), Am. Fish. Soc. Symp. 1 p. 131-136, Boston.

Lintz, J.D., and T.T. Kisanuki. 1991. Progress report for investigations on the lower tributaries

to the Klamath River; FY 1991. U. S. Fish Wildl. Serv., Coastal California Fishery

Resource Office, Arcata, CA. (Available from USFWS, Klamath River Fishery Resource

Office, P.O. Box 1006, Yreka, CA 96097.)

Lintz, J.D., and S.M. Noble. 1990. Progress report for investigations on the lower tributaries to

the Klamath River, FY 1990. U.S. Dep. of the Interior, Fish Wildl. Serv., Coastal

California Fishery Resource Office, Arcata, CA, 35 p. (Available from U.S. Dep. of

Interior, Fish. Wildl. Serv. Wildl. Serv., Klamath River Fishery Resource Office, P.O.

Box 1006, Yreka, CA 96097.)

Loch, J.J., and P.M. Downing. 1990. 1989 Toutle River fish collection facility operation and

salmonid investigations. WDFW, Fish. Manage. Div., F.M. No. 89-13, 50 p.
227

Loch, J.J., and D.R. Miller. 1988. Distribution and diet of sea-run cutthroat trout captured in

and adjacent to the Columbia River plume, May-July 1980. Northwest Sci. 62(1):41-48.

Loomis, D., and R. Anglin. 1992. North Umpqua river management plan: Progress Rep. 1991-

1992. Oregon Dep. Fish Wildl., Portland, OR, 29 p.

Loomis, D., R. Anglin, and D. Harris. 1993. Fish management review. Oreg. Dep. Fish Wildl.,

Portland, OR, 100 p.

Loudenslager, E.J., and G.A.E. Gall. 1980. Geographic patterns of protein variation and

subspeciation in the cutthroat trout. Syst. Zool. 29:27-42.

Loudenslager, E.J., and G.H. Thorgaard. 1979. Karyotypic and evolutionary relationships of the

Yellowstone (Salmo clarki bouvieri) and west-slope (S. c. lewisi) cutthroat trout. J. Fish.

Res. Board Can. 36:630-635.

Lowry, G.R. 1965. Movement of cutthroat trout (Salmo clarki clarki Richardson) in three

Oregon coastal streams. Trans. Am. Fish. Soc. 94(4):334-338.

Lowry, G.R. 1966. Production and food of cutthroat trout in three Oregon coastal streams.

J. Wildl. Manage. 30(4):754-766.

Ludwa, K., G. Lucchetti, K.L. Fresh, and K. Walter. 1997. Assessing stream-dwelling fishes in

basins of the Lake Washington watershed, Summer 1996. Unpubl. manuscr. (Available

from King Co. Dep. of Natural Resources, Water and Land Resources Division, 700 Fifth

Avenue Suite 2200, Seattle, WA 98104.)

Lynch, J.D. 1941. Letter to C. Pautzke, Washington Department of Game, 4 August 1941.

(Available from Environmental and Technical Services Division, NMFS, 525 NE Oregon

St., Portland OR 97232.)

Lynch, M., and W. Gabriel. 1987. Environmental tolerance. Am. Nat. 129:283-303.

Marnell, L.F. 1988. Status of the westslope cutthroat trout in Glacier National Park, Montana.

In R.E. Gresswell (ed.), Status and management of interior stocks of cutthroat trout,

p. 61-70. Am. Fish. Soc., Bethesda.

Marnell, L.F., R.J. Behnke, and F.W. Allendorf. 1987. Genetic identification of cutthroat trout

(Salmo clarki) in Glacier National Park, Montana. Can. J. Fish. Aquat. Sci. 44:573-582.

Martin, M.A., D.K. Shiozawa, E.J. Loudenslager, and J.N. Jensen. 1985. Electrophoretic study

of cutthroat trout populations in Utah. Great Basin Natur. 45:677-687.

Maser, C., and J.R. Sedell. 1994. From the forest to the sea: The ecology of wood in streams,

rivers, estuaries and oceans. St. Lucie Press, Delray Beach, FL, 200 p.
228

McCain, M. Unpubl. data. Annual direct observation counts for the Smith River basin, Del

Norte County, CA. 1990-1997. Memo to G. Bryant, June 1998. U.S. Dep. of

Agriculture, For. Serv., Six Rivers National Forest, P.O. Box 228, Gasquet, CA 95543.

McHenry, M.L. 1996. Freshwater habitat condition affecting Strait of Juan de Fuca populations

of coho salmon (Oncorhynchus kisutch). Lower Elwha Klallam Tribe. Port Angeles,

Washington, 46 p.

McLain, D.R. 1984. Coastal ocean warming in the northeast Pacific 1976-83. In W.G. Pearcy

(ed.), The influence of ocean conditions on the production of salmonids in the North

Pacific: A workshop, November 8-10, 1983, Newport, Oregon, p. 61-86. Publ.

ORESU-WO-83-001, Oregon Sea Grant Prog., Oregon State Univ., Corvallis.

McLaughlin, S.P. 1989. Natural floristic areas of the western United States. J. Biogeogr.

16:239-248.

McPhail, J.D., and C.C. Lindsey. 1970. Freshwater fishes of northwestern Canada and Alaska.

Fish. Res. Board Can. Bull. 173, Ottawa, 381 p.

McPhail, J.D., and C.C. Lindsey. 1986. Zoogeography of the freshwater fishes of Cascadia (the

Columbia system and rivers north to the Sitkine). In C.H. Hocutt and E.O. Wiley (eds.),

Zoogeography of North American freshwater fishes, p. 615-637. Wiley Interscience

Publications, New York.

Meehan, W.R. 1991. Introduction and overview. In W.R. Meehan (ed.), Influence of forest and

rangeland management on salmonid fishes and their habitats, p. 1-16. Am. Fish. Soc.

Spec. Publ. 19, Bethesda.

Mercer, S.P., and J.M. Johnston. 1979. Sea-run cutthroat: development and evaluation of a new

enhancement technique. Wash. State Game Dep. Fish. Res. Rep. F-68-R-3, Olympia,

WA, 45 p.

Metcalfe, N.B. 1993. Behavioural causes and consequences of life history variation in fish. In

F. A. Huntingford and P. Torricelli (eds.), Behavioral ecology of fishes. Vol. 11,

p. 205-217. Harwood Academic Publishers, Poststrasse 22, 7000 Chur, Switzerland.

Michael, H. 1980. Sea-run cutthroat trout. In J.J. DeShazo (ed.), Sea-run cutthroat status report.

Rep. 80-14, p. 187-190. Wash. State Game Dep., Fish. Manage. Div., Olympia, WA.

Michael, J.H., Jr. 1989. Life history of anadromous coastal cutthroat trout in Snow and Salmon

Creeks, Jefferson County, Washington, with implications for management. Calif. Dep.

Fish Game 75(4):188-190.

Miller, R.J., and E.L. Brannon. 1982. The origin and development of life-history patterns in

Pacific salmon. In E.L. Brannon and E.O. Salo (eds.), Proceedings of the Salmon and

Trout Migratory Behavior Symposium, p. 296-309, Univ. Wash. Press, Seattle, WA.
229

Minckley, W.L., D.A. Hendrickson, and C.E. Bond. 1986. Geography of western North

American freshwater fishes: Description and relationships to intracontinental tectonism.

In C.H. Hocutt and E.O. Wiley (eds.), Zoogeography of North American freshwater

fishes, p. 519-613. Wiley Interscience Publications, New York.

Mitchell, W.T. 1988. Microhabitat utilization and spatial segregation of juvenile coastal

cutthroat and steelhead trout in the Smith River drainage, California. M.S. Thesis,

Humboldt State Univ., Arcata, CA.

Monaco, M.E., T.A. Lowery, and R.L. Emmett. 1992. Assemblages of U.S. West Coast

estuaries based on the distribution of fishes. J. Biogeogr. 19:251-267.

Moore, K.M.S., and S.V. Gregory. 1988. Summer Habitat Utilization and Ecology of Cutthroat

(Salmo clarki) in Cascade Mountain Streams. Can. J. Fish. Aquat. Sci. 45:1921-1930.

Moring, J.R, and R.L. Lantz. 1975. The Alsea watershed study: Effects of logging on the

aquatic resources of three headwater streams of the Alsea River, Oregon. Oregon Dep.

Fish Wildl., Corvallis, OR. Fish. Res. Rep. Number 9, Project AFS-58, Final Rep., 66 p.

Moring, J.R., R.L. Youker, and R.M. Hooton. 1986. Movements of potamodromous coastal

cutthroat trout, Salmo clarki clarki, inferred from tagging and scale analysis. Fish. Res. 4

:343-354.

Morrison, S.W., J.K. Kettman, and D. Haug. 1993. Inventory and characterization of shoreline

armoring, Thurston County, Washington, 1977-1993. Prepared by Thurston Regional

Planning Council for Wash. Dep. Ecology. (Available from Environmental and

Technical Services Division, NMFS, 525 NE Oregon St., Portland, OR 97232.)

Moyle, P.B. 1976. Inland fishes of California. Univ. Calif. Press, Berkeley, 405 p.

Mullan, J.W., K.R. Williams, G. Rhodus, T.W. Hillman, and J.D. McIntyre. 1992. Production

and habitat of salmonids in mid-Columbia River tributary streams. Monograph I, U.S.

Dep. of the Interior, Fish. Wildl. Serv., Box 549, Leavenworth, WA 98826, 489 p.

Murphy, M.L. 1995. Forestry impacts on freshwater habitat of anadromous salmonids in the

Pacific Northwest and Alaska-Requirements for protection and restoration. U.S. Dep. of

Commerce, Coastal Ocean Program, Decision Analysis Series No. 7, 156 p.

Murphy, M.L., and J.D. Hall. 1981. Vaired [sic] effects of clear-cut logging on predators and

their habitat in small streams of the Cascade Mountains, Oregon. Can. J. Fish. Aquat.

Sci. 38:137-145.

Murphy, M.L., and W.R. Meehan. 1991. Stream Ecosystems. In W.R. Meehan (ed.), Influence

of forest and rangeland management on salmonid fishes and their habitats, p. 17-46. Am.

Fish. Soc. Spec. Publ. 19, Bethesda.
230

Myers, G.S. 1949. Usage of anadromous, catadromous and allied terms for migratory fishes.

Copeia 2:89-97.

Myers, J.M., R.G. Kope, G.J. Bryant, D. Teel, L.J. Lierheimer, T.C. Wainwright, W.S. Grant,

F.W. Waknitz, K. Neeley, S.T. Lindley, and R.S. Waples. 1998. Status review of

chinook salmon from Washington, Idaho, Oregon, and California. U.S. Dep. of

Commerce, NOAA Tech. Memo. NMFS-NWFSC-35, 443 p.

Narver, D.W. 1971. Effects of logging debris on fish production. In J.T. Krygier and J.D. Hall

(eds.), Proceedings of the Symposium on Forest Land Uses and Stream Environment.

October 19-20, 1970, p. 100-111, Oregon State Univ., Corvallis.

National Marine Fisheries Service (NMFS). 1991. Notice of policy: Policy on applying the

definition of species under the Endangered Species Act to Pacific salmon. Federal

Register [Docket 9910248-1255, November 1991] 56 (224):58612-58618.

National Marine Fisheries Service (NMFS). 1993. Interim policy on artificial propagation of

Pacific salmon under the Endangered Species Act. Federal Register [Docket 921186-

2286, 5 April 1993] 58 (63):17573-17576.

National Marine Fisheries Service (NMFS). 1994. Listing endangered and threatened species

and designating critical habitat: Initiation of status review for pink salmon, chum salmon,

and sea-run cutthroat trout population in Washington, Oregon, Idaho, and California.

Federal Register [I.D.081694D, 12 September 1994] 59 (175):46808-46810.

National Marine Fisheries Service (NMFS). 1996. Factors for decline: A supplement to the

notice of determination for west coast steelhead under the endangered Species Act.

Protected Species Branch, NMFS, 525 NE Oregon St., Suite 500, Portland, OR 97232.

83 p.

National Marine Fisheries Service (NMFS). Unpubl. data. Coast-wide genetic database for coho

salmon. NMFS, Northwest Fisheries Science Center, 2725 Montlake Blvd. E., Seattle,

WA 98112.

National Marine Fisheries Service (NMFS), Oregon Department of Fish and Wildlife (ODFW),

and Washington Department of Fish and Wildlife (WDFW). Unpubl. data. Coast-wide

genetic data base for coastal cutthroat trout. (Available from NMFS, Northwest Fisheries

Science Center, 2725 Montlake Blvd. E., Seattle, WA 98112.)

National Marine Fisheries Service (NMFS), and Washington Department of Fish and Wildlife

(WDFW). Unpubl. data-a. Coast-wide genetic data base for chinook salmon. (Available

from NMFS, Northwest Fisheries Science Center, 2725 Montlake Blvd. E., Seattle, WA

98112.)
231

National Marine Fisheries Service (NMFS), and Washington Department of Fish and Wildlife

(WDFW). Unpubl. data-b. Coast-wide genetic data base for coastal steelhead.

(Available from NMFS, Northwest Fisheries Science Center, 2725 Montlake Blvd. E.,

Seattle, WA 98112.)

National Research Council Committee on Protection and Management of Pacific Northwest

Anadromous Salmonids (NRCC). 1996. Upstream: salmon and society in the Pacific

Northwest. National Academy Press, Washington, D.C., 452 p.

Natural Heritage Network, The. 1998. Standardized data on endangered species and

communities. (Available through Internet, www.heritage.tnc.org)

Natural Resource Consultants (NRC). 1996. Artificial propagation anadromous Pacific

salmonids 1950 to present. Cutthroat trout. Report to U.S. Dep. of Commerce, NOAA,

NMFS, January 1995. Includes electronic database. (Available from Environmental and

Technical Services Division, NMFS, 525 NE Oregon St., Portland, OR 97232.)

Neave, F. 1944. Racial characteristics and migratory habits in Salmo gardneri. J. Fish. Res.

Board Can. 6:245-251.

Nehlsen, W., J.E. Williams, and J.A. Lichatowich. 1991. Pacific salmon at the crossroads:

stocks at risk from California, Oregon, Idaho, and Washington. Fisheries 16(2):4-21.

Nei, M. 1972. Genetic distance between populations. Am. Nat. 106:282-292.

Nei, M. 1973. Analysis of gene diversity in subdivided populations. Proc. Nat. Acad. Sci.

U.S.A. 70:3321-3323.

Nei, M. 1978. Estimation of average heterozygosity and genetic distance from a small number

of individuals. Genetics 89:583-590.

Neillands, W.G. 1990. Natural hybridization between coastal cutthroat trout (Oncorhynchus

clarki) and steelhead trout (Oncorhynchus mykiss) within Redwood Creek, California.

M.S. Thesis, Humboldt State Univ., Arcata, CA.

Nesbit, D.M. 1885. Tide marshes of the United States. U.S. Dep. of Agriculture, Wash. D.C.

Misc. Spec. Rep. 7, 259 p.

Nicholas, J.W. 1978a. Life history differences between sympatric populations of rainbow and

cutthroat trouts in relation to fisheries management strategy. In J.R. Moring (ed.),

Proceedings of the Wild Trout-Catchable Trout Symposium, p. 181-188. Oreg. Dep. Fish

Wildl., Portland.

Nicholas, J.W. 1978b. A review of literature and unpublished information on cutthroat trout

Salmo clarki clarki of the Willamette watershed. Oreg. Dep. Fish Wildl. Info. Rep. Ser.,

Fish. No. 78-1, 22 p.
232

Nickelson, T.E., J.W. Nicholas, A.M. McGie, R.B. Lindsay, D.L. Bottom, R.J. Kaiser, and S.E.

Jacobs. 1992. Status of anadromous salmonids in Oregon coastal basins., Oreg. Dep.

Fish Wildl., Res. Develop. Sect. and Ocean Salmon Manage., Corvallis. (Available from

ODFW, P.O. Box 59, Portland, OR 97207.)

Nilsson, N., and T.G. Northcote. 1981. Rainbow trout (Salmo gairdneri) and cutthroat trout

(S. clarki) interactions in coastal British Columbia Lakes. Can. J. Fish. Aquat. Sci.

38(10):1228-1246.

Nordeng, H. 1983. Solution to the “char problem” based on Arctic char (Salvelinus alpinus) in

Norway. Can. J. Fish. Aquat. Sci. 40:1372-1387.

Norse, E.A. 1990. Ancient forests of the Pacific Northwest. The Wilderness Society and Inland

Press, Wash. D.C.

Northcote, T.G. 1969. Patterns and mechanisms in the lakeward migratory behaviour of

juvenile trout. In T.G. Northcote (ed.), Symposium on salmon and trout in streams,

p. 183-203, Univ. British Columbia, Vancouver.

Northcote, T.G. 1970. Meristic and lactate dehydrogenase genotype differences in stream

populations of rainbow trout below and above a waterfall. J. Fish. Res. Board. Can.

27:1987-1995.

Northcote, T.G. 1992. Migration and residency in stream salmonids - some ecological

considerations and evolutionary consequences. Nordic J. Freshw. Res. 67:5-17.

Northcote, T.G. 1995. Confessions from a four decade affair with Dolly Varden: a synthesis and

critique of experimental tests for interactive segregation between Dolly Varden char

(Salvelinus malma) and cutthroat trout (Oncorhynchus clarki) in British Columbia.

Nordic J. Freshw. Res. 71:49-67.

Northcote, T.G. 1997a. Why sea-run? An exploration into the migratory/residency spectrum of

coastal cutthroat trout. In J.D. Hall, P.A. Bisson and R.E. Gresswell (eds.), Sea-run

cutthroat trout: biology, management, and future conservation, p. 20-26. Am. Fish. Soc.,

Corvallis.

Northcote, T.G. 1997b. Potamodromy in Salmonidae-living and moving in the fast lane.

N. Am. J. Fish. Manage. 17:1029-1045.

Northcote, T.G., and D.Y. Atagi. 1996. Pacific salmon abundance trends in the Fraser River

watershed compared with other British Columbia systems. In D.J. Strouder, P.A. Bisson

and R.N. Naiman (eds.), Pacific salmon ecosystems: status and future options. Chapman

and Hall, New York.

Omernik, J.M. 1987. Ecoregions of the conterminous United States. Ann. Assoc. Am. Geog.

77(1):118-125.
233

Omernik, J.M, and A.L. Gallant. 1986. Ecoregions of the Pacific Northwest. U.S. Environ.

Protec. Agen. Rep. EPA/600/3-86/033, 39 p. (Available from U.S. Environmental

Protection Agency, Environmental Research Laboratory, 200 SW 35th St., Corvallis, OR

97333.)

Oregon Department of Fish and Wildlife (ODFW). 1993a. Letter to ESA Administrative

Record for North and South Umpqua River sea-run cutthroat trout, September 17, 1993,

Enclosure 28, north Umpqua sea-run cutthroat 1991 progress report for compliance with

wild fish management policy (workshop notes). (Available from Environmental and

Technical Services Division, NMFS, 911 NE 11th Ave., Room 620, Portland OR 97232.)

Oregon Department of Fish and Wildlife (ODFW). 1993b. Letter to ESA Administrative

Record for North and South Umpqua River sea-run cutthroat trout, September 17, 1993,

Enclosure 36, Notes on cutthroat trout in south coast Oregon streams: Based on field

observations between 1986-1990. C. Frissell and R. Nawa. (Available from

Environmental and Technical Services Division, NMFS, 911 NE 11th Ave., Room 620,

Portland OR 97232.)

Oregon Department of Fish and Wildlife (ODFW). 1998. Memo from J.W. Greer to R. Waples.

7 Oct. 1998. 19 p. + attach. (Available from Environmental and Technical Services

Division, NMFS, 525 NE Oregon St., Portland, OR 97232.)

Oregon Natural Resources Council (ONRC), Coast Range Association, Native Fish Society,

Northwest Ecosystem Alliance, Save the West, Siskiyou Regional Education Project,

Siskiyou Audubon, Trout Unlimited of California, Western Ancient Forest Campaign,

Salmon Defense Association, Salmon Forever, California Sportfishing Alliance, Oregon

Wildlife Federation, Clark-Skamania Fly Fishermen, and the Washington Rivers Council.

1997. Petition to list sea-run cutthroat trout (Oncorhynchus clarki clarki) as threatened or

endangered throughout its range in the states of California, Oregon, and Washington,

under the Endangered Species Act (ESA) and to designate critical habitat. Unpubl.

manuscr., 38 p. (Document submitted to the USDOC NOAA NMFS Northwest Division,

Seattle, Washington, December 5, 1997). (Available from Oregon Natural Resources

Council, 522 SW 5th Avenue, Suite 1050, Portland OR 97204.)

Oregon Natural Resources Council (ONRC), The Wilderness Society, and Umpqua Valley

Audubon Society. 1993. Petition for a rule to list the North and South Umpqua river searun cutthroat trout as threatened or endangered under the Endangered Species Act and to

designate critical habitat. Document submitted to the USDOC NOAA NMFS Northwest

Division, Seattle, Washington, April 1993. (Available from Oregon Natural Resources

Council, 522 SW 5th Avenue, Suite 1050, Portland OR 97204.)

Oregon State Game Commission (OSGC). 1947. Lower Umpqua River Study. Ann. Rep., L.M.

Mathisen, Field Agent to Dr. P.R. Needham, Director of Fisheries. (Available from

Environmental and Technical Services Division, NMFS, 525 NE Oregon St., Portland,

OR 97232.)
234

Oregon State Game Commission (OSGC). 1949. Summary. Annual Report. Lower Umpqua

River Study 1949. (Available from Environmental and Technical Services Division,

NMFS, 525 NE Oregon St., Portland, OR 97232.)

Pacific Northwest River Basins Commission (PNRBC). 1969. Columbia-North Pacific region

comprehensive framework study of water and related lands. Appendix II. The Region.

Pacific Northwest River Basins Commission, 147 p.

Palmisano, J.F., R.H. Ellis, and V.W. Kaczynski. 1993. The impact of environmental and

management factors on Washington’s wild anadromous salmon and trout. Wash. Forest

Protection Assoc. and Wash. Dep. of Natural Resources, Olympia, WA. January 1993,

371 p.

Pauley, G.B., K. Oshima, K.L. Bowers, and G.L. Thomas. 1989. Species profiles: Life histories

and environmental requirements of coastal fishes and invertebrates (Pacific Northwest)

sea-run cutthroat trout. U.S. Fish. Wildl. Serv. Biol. Rep. 82(11.86). U.S. Army Corps of

Engineers, TR EL-82-4. 21 p.

Pearcy, W.G. 1992. Ocean ecology of North Pacific salmonids. Univ. Washington Press,

Seattle, 179 p.

Pearcy, W.G. 1997. The sea-run and the sea. In J.D. Hall, P.A. Bisson and R.E. Gresswell

(eds.), Sea-run cutthroat trout: biology, management, and future conservation, p. 29-36.

Am. Fish. Soc., Corvallis.

Pearcy, W.G., and J.P. Fisher. 1988. Migrations of coho salmon, Oncorhynchus kisutch, during

their first summer in the ocean. Fish. Bull., U.S. 86:173-195.

Pearcy, W.G., R.D. Brodeur, and J.P. Fisher. 1990. Distribution and biology of juvenile

cutthroat trout Oncorhynchus clarki clarki and steelhead O. mykiss in coastal waters off

Washington and Oregon. Fish. Bull., U.S. 88(4):697-711.

Peoples, M., M. Cenci, and J. Hunter. 1987. Sea-run cutthroat studies in South Puget Sound

tributaries. July 1986 to June 1987. Wash. Dep. Wildl., Fish. Manage. Div., Rep. 88-12,

42 p.

Peters, R.J., E.E. Knudsen, and G.B. Pauley. 1996a. The effects of fry supplementation on the

emigration of salmonids from tributaries of the Clearwater River, Washington. U.S. Dep.

Interior Fish Wildl. Serv., Western Washington Fishery Resource Office, Olympia, 66 p.

Peters, R.J., E.E. Knudsen, and G.B. Pauley. 1996b. The effects of coho salmon fry

supplementation on salmonid densities and growth in tributaries of the Clearwater River,

Washington. U.S. Dep. Interior Fish Wildl. Serv., Western Washington Fishery Resource

Office, Olympia, 37 p.
235

Pettit, R. Unpubl. data. Coastal cutthroat trout smolt data from Chelatchie Cr. tributary of the

lower Columbia River. Collected as part of the Lower Columbia River Coho

Enhancement Project. Wash. Dep. Fish. Wildl., Planning, Research, and Harvest

Management Program, Columbia River Laboratory, 16118 N.E. 219th Street, P.O. Box

999, Battle Ground, WA 98604.

Phelps, S.R., L.L. Le Clair, S. Young, and H.L. Blankenship. 1994. Genetic diversity patterns

of chum salmon in the Pacific Northwest. Can. J. Fish. Aquat. Sci. 51(Suppl. 1):65-83.

Platts, W.S. 1974. Geomorphic and aquatic conditions influencing salmonids and stream

classification, with application to ecosystem classification. USDA Forest Service.

Billings, MT.

Point No Point Treaty Council (PNPTC). 1994. Summary report: Hoko and Skokomish River

coho salmon indicator stock studies 1986-1989. PNPTC Tech. Rep. TR 94-1, (Available

from PNPTC, 7999 NE Salish Lane Kingston, WA 98346.)

Price, T., and D. Schluter. 1991. On the low heritability of life history traits. Evolution 45:853-

861.

Randolph, C. 1986. Characteristics of Skamania and Beaver Creek Hatchery anadromous

stocks. Wash. Dep. Game. Fish. Manage. Div., Olympia, WA. 154 p. (Available from

WDFW, 600 Capitol Way N., Olympia, WA 98501-1091.)

Redwood National Park. 1983, 1988-1993. Unpubl. data. Weekly beach seining operations in

Redwood Creek Estuary, CA. U.S. Dep. of the Interior, Calif. Dep. Parks. Rec.,

Redwood National and State Parks, 219 Hilton Rd., Orick CA 95555.

Redwood National Park. 1997, 1998. Unpubl. data. Weekly screw trap surveys for anadromous

salmonids in Prairie Creek, CA. U.S. Dep. of the Interior, Calif. Dep. Parks. Rec.,

Redwood National and State Parks, 219 Hilton Rd., Orick CA 95555.

Redwood National Park. 1998. Summary of reports and data relating to coastal cutthroat trout

in the Redwood Creek Basin. 2 p. + attach. (Available from Environmental Technical

Services Division, NMFS, 525 NE Oregon St., Portland, OR 97232.)

Reeves, G.H., F.H. Everest, and J.R. Sedell. 1993. Diversity of juvenile anadromous salmonid

assemblages in coastal Oregon basins with different levels of timber harvest. Trans. Am.

Fish. Soc. 122:309-317.

Reeves, G.H., J.D. Hall, and S.V. Gregory. 1997. The impact of land-management activities on

coastal cutthroat trout and their freshwater habitats. In J.D. Hall, P.A. Bisson and R.E.

Gresswell (eds.), Sea-run cutthroat trout: biology, management, and future conservation,

p. 138-144. Am. Fish. Soc., Corvallis.
236

Reeves, G.H., J.D. Hall, T.D. Roelofs, T.L. Hickman, and C.O. Baker. 1991. Rehabilitating and

modifying stream habitats. Am. Fish. Soc. Spec. Publ. 19:519-558.

Refalt, W. 1985. Wetland in extremis: A nationwide survey. Wilderness Winter 1985 :28-41.

Reimchen, T.E. 1990. Size-structured mortality in a threespine stickleback (Gasterosteus

aculeatus)-cutthroat trout (Oncorhynchus clarki) community. Can. J. Fish. Aquat. Sci.

47:1194-1205.

Reimers, P.E. 1973. The length of residence of juvenile fall chinook salmon in the Sixes River,

Oregon. Oreg. Fish Comm. 4:2-43.

Ricker, W.E. 1972. Hereditary and environmental factors affecting certain salmon populations.

In R.C. Simon and P.A. Larkin (eds.), The stock concept in Pacific salmon, p. 19-160.

Univ. British Columbia, Vancouver.

Ricker, W.E. 1981. Changes in the average size and average age of Pacific salmon. Can. J.

Fish. Aquat. Sci. 38:1636-1656.

Riggs, L.A. 1990. Principles for genetic conservation and production quality. Report to

Northwest Power Planning Council, Portland, OR. (Available from Northwest Power

Planning Council, 851 SW Sixth, Suite 1100, Portland, OR 97204-1348.)

Roff, D.A. 1992. The evolution of life histories. Theory and analysis. Chapman & Hall, New

York, 535 p.

Rogers, J.S. 1991. A comparison of the suitability of the Rogers, modified Rogers, Manhattan

and Cavalli-Sforza and Edwards distances for inferring phylogenetic trees from allele

frequencies. Syst. Zool. 40:63-73.

Roper, B.B. 1995. Ecology of anadromous salmonids within the upper South Umpqua River

Basin, Oregon, Univ. Idaho, Moscow.

Roth, A.R. 1937. A survey of the waters of the South Umpqua Ranger District: Umpqua

National Forest. U.S. Dep. of the Interior, For. Serv., Portland, Oregon, 41 p.

Royal, L.A. 1972. An examination of the anadromous trout program of the Washington State

Game Department. Wash. State Game Dep. Final Rep. AFS-49, Olympia, WA. 197 p.

Ryman, N. 1983. Patterns of distribution of biochemical genetic variation in salmonids:

Differences between species. Aquaculture 33:1-4.

Sabo, J.L., and G.B. Pauley. 1997. Competition between stream-dwelling cutthroat trout

(Oncorhynchus clarki) and coho salmon (Oncorhynchus kisutch): effects of relative size

and population origin. Can. J. Fish. Aquat. Sci. 54:2609-2617.
237

Saiget, D., J.K. Hodges, M. Schelske, and D. Schmid. In prep. Migrations and behavior of

Copper River Delta cutthroat trout inferred from radio telemetry. U.S. Dep. of

Agriculture, For. Serv., Cordova Ranger District, Cordova, AK. (Available from USDA,

For. Serv., Zig Zag Ranger Dist., 70220 E. Hwy 26, Zig Zag, OR 97049.)

Saitou, N., and M. Nei. 1987. The neighbor-joining method: a new method for reconstructing

phylogenetic trees. Mol. Biol. Evol. 4:406-425.

Savvaitova, K. A., K.V. Kuzishchin, S.V. Maksimov, and G.G. Novikov. 1995. A new form of

Pacific basin trout of the genus Salmo from Kamchatka. Ikhtiologii 35:565-571 [in

Russian. English translation in Journal of Ichthyology 35(8):198-206].

Schmidt, A.E. 1997. Status of sea-run cutthroat trout stocks in Alaska. In J.D. Hall, P.A. Bisson

and R.E. Gresswell (eds.), Sea-run cutthroat trout: biology, management, and future

conservation, p. 80-83. Am. Fish. Soc., Corvallis.

Schultz, L.P. 1936. Keys to the fishes of Washington and Oregon and closely adjoining regions.

Univ. Wash. Publ. Biol. 2:105-228.

Schutz, D.C, and T.G. Northcote. 1972. An experimental study of feeding behavior and

interaction of coastal cutthroat trout (Salmo clarki clarki) and Dolly Varden (Salvelinus

malma). J. Fish. Res. Board Can. 29:555-565.

Scott, J.B., C.R. Steward, and Q.J. Stober. 1986. Effects of urban development on fish

population dynamics in Kelsey Creek, Washington. Trans. Am. Fish. Soc. 115:555-567.

Scott, W.B., and E.J. Crossman. 1973. Freshwater fishes of Canada. Bull. Fish. Res. Board Can.

966 p.

Sedell, J.R., and J.L. Froggatt. 1984. Importance of streamside forests to large rivers: the

isolation of the Willamette River, Oregon, U.S.A., from its floodplain by snagging and

streamside forest removal. Int. Ver. Theor. Angew. Limno. Verh. 22:1828-1834.

Sedell, J.R., and K.J. Luchessa. 1982. Using the historical record as an aid to salmonid habitat

enhancement. In N.B. Armantrout (ed.), Proceedings of a symposium held October 28-

30, 1981, p. 210-223, The Hague Publishing, Billings, MT, Portland, OR.

Seiler, D., and P. Hanratty. Unpubl. data. Coastal cutthroat trout outmigrant trap data from

selected Strait of Juan de Fuca streams. (Available from WDFW, 600 Capitol Way N.,

Olympia, WA 98501-1091.)

Seiler, D., P. Hanratty, S. Neuhauser, P. Topping, M. Ackley, and L.E. Kishimoto. 1995. Wild

salmon production and survival evaluation annual performance report. October 1993-

September 1994. Wash. Dep. Fish. Wildl., WDFW Progress Report. (Available from

WDFW, 600 Capitol Way N., Olympia, WA 98501-1091.)
238

Seiler, D., P. Hanratty, S. Neuhauser, P. Topping, M. Ackley, and L.E. Kishimoto. 1997.

Annual performance report Oct. 1994-1995, wild salmon production and survival

evaluation. Wash. Dep. Fish. Wildl. Report No. RAD 97-03. (Available from WDFW,

600 Capitol Way N., Olympia, WA 98501-1091.)

Seiler, D., L.E. Kishimoto, and S. Neuhauser. 1998. Annual report - 1997 Skagit River wild 0+

chinook production evaluation. Wash. Dep. Fish. Wildl. (Available from WDFW, 600

Capitol Way N., Olympia, WA 98501-1091.)

Seiler, D., S. Wolthausen, and L.E. Kishimoto. 1992. Evaluation of downstream migrant

passage through the sediment retention structure, North Fork Toutle River, 1991. WDF

Prog. Rep. 297. 45 p.

Shaklee, J. B., F.W. Allendorf, D.C. Morizot, and G.S. Whitt. 1990. Gene nomenclature for

protein-coding loci in fish. Trans. Am. Fish. Soc. 119:2-15.

Shaw, T.A., and C.L. Jackson. 1994. Little River juvenile salmonid monitoring. U.S. Dep.

Interior Fish Wildl. Serv., Fisheries Assistance Office, Arcata, CA.

Shedlock, A.M., J.E. Parker, D.A. Crispin, T.W. Pietsch, and G.C. Burmer. 1992. Evolution of

the salmonid mitochondrial control region. Mol. Phylog. Evol. 1:179-192.

Shepard, B., K. Pratt, and J. Graham. 1984. Life histories of westslope cutthroat and bull trout

in the upper Flathead River Basin, Montana. Montana Department of Fisheries, Wildlife

and Parks, Kalispell, MT.

Shipman, H. 1997. Shoreline armoring on Puget Sound. Puget Sound Notes 40:2-6.

Shutt, M. 1998. Clark Public Utilities news release, 20 January, 1998. (Available through

Internet, www.clarkpud.com/)

Simenstad, C.A., K.L. Fresh, and E.O. Salo. 1982. The role of Puget sound and Washington

coastal estuaries in the life history of Pacific salmon: An unappreciated function. In V.S.

Kennedy (ed.), Estuarine comparisons, p. 343-364. Academic Press, New York.

Simon, R.C. 1963. Chromosome morphology and species evolution in the five North American

species of Pacific Salmon (Oncorhynchus). J. Morph. 112:77-97.

Simon, R.C. 1964. Cytogenetics, relationships and evolution in salmonidae. Ph.D. Dissertation,

Univ. Washington, Seattle.

Simon, R.C., and A.M. Dollar. 1964. Cytological aspects of speciation in two North American

teleosts Salmo gairdneri and S. clarki lewisi. Can. J. Genet. Cyto. 5(1):43-49.
239

Simon, R.C., J.D. McIntyre, and A.R. Hemmings. 1986. Family size and effective population

size in a hatchery stock of coho salmon (Oncorhynchus kisutch). Can. J. Fish. Aquat.

Sci. 43:2424-2443.

Simondet, J. 1997. Habitat preference among coastal cutthroat trout (Oncorhynchus clarki

clarki) in a California stream: Relevant scales of resolution. Unpubl. rep. USDA Forest

Service, Redwood Sciences Lab, Arcata, CA.

Skaala, O., and G. Naevdal. 1989. Genetic differentiation between freshwater resident and

anadromous brown trout, Salmo trutta, within watercourses. J. Fish Biol. 34:597-605.

Slaney, T.L., K.D. Hyatt, T.G. Northcote, and R.J. Fielden. 1997. Status of sea-run cutthroat

trout in British Columbia. In J.D. Hall, P.A. Bisson and R.E. Gresswell (eds.), Sea-run

cutthroat trout: biology, management, and future conservation, p. 77-79. Am. Fish. Soc.,

Corvallis.

Slatkin, M. 1985. Rare alleles as indicators of gene flow. Evolution 39:53-65.

Slobodkin, L. 1961. Growth and regulation of animal populations. Holt, Rinehart and Winston,

New York, 184 p.

Sneath, P.H.A., and R.R. Sokal. 1963. Numerical taxonomy. W.H. Freeman, San Francisco,

573 p.

Snyder, J.O. 1907. The fishes of the coastal streams of Oregon and northern California. U.S.

Bur. Fish, Bull 27:155-189.

Speis, T.A., and J.F. Franklin. 1988. Old growth and forest dynamics in the Douglas fir region

of western Oregon and Washington. Nat. Areas J. 8:190-201.

Spruell, P. Unpubl. data. Cutthroat trout DNA database. (Available from Division of Biological

Sciences, Univ. Montana, Missoula, MT 59812-1002.)

Ståhl, G. 1987. Genetic population structure of Atlantic salmon. In N. Ryman and F. Utter

(eds.), Population genetics and fishery management, p. 121-140. Univ. Washington

Press, Seattle.

Stearley, R.F. 1992. Historical ecology of salmoninae, with special reference to Oncorhynchus.

In R.L. Mayden (ed.), Systematics, historical ecology, and North American freshwater

fishes, p. 622-658. Stanford Univ. Press, Stanford, CA.

Stearley, R.F., and G.F. Smith. 1993. Phylogeny of the Pacific trouts and salmons

(Oncorhynchus) and genera of the Family Salmonidae. Trans. Am. Fish. Soc. 122:1-33.

Stearns, S.C. 1976. Life history tactics: a review of the ideas. Q. Rev. Biol. 51:3-47.
240

Stearns, S.C. 1989. The evolutionary significance of phenotypic plasticity. BioScience 39:436-

445.

Stearns, S.C. 1992. The evolution of life histories. Oxford Univ. Press, Oxford, U.K., 249 p.

Stebbins, R.C. 1985. A field guide to western reptiles and amphibians, 2nd ed. The Peterson

field guide series, Houghton Mifflin, Boston, 279 p.

Steward, C.R., and T.C. Bjornn. 1990. Supplementation of salmon and steelhead stocks with

hatchery fish: a synthesis of published literature. U.S. Dep. of Energy, Bonneville Power

Administration. Tech. Rep. 90-1. (Available from U.S. Dept. of Energy, Bonneville

Power Administration, Fish and Wildlife, P.O. Box 3621, Portland, OR 97208.)

StreamNet. 1998. Electronic Database, Version 98.3. Gladstone, OR. (Available through

Internet, www.streamnet.org)

Sumner, F.H. 1948. The coast cutthroat trout. Oregon Game Comm. Bull 3(12):1, 6-8.

Sumner, F.H. 1953. Migrations of salmonids in Sand Creek, Oregon. Trans. Am. Fish. Soc.

82:139-150.

Sumner, F.H. 1962. Migration and growth of coastal cutthroat trout in Tillamook County,

Oregon. Trans. Am. Fish. Soc. 91(1):77-83.

Sumner, F.H. 1972. A contribution to the life history of the cutthroat trout in Oregon with

emphasis on the coastal subspecies, Salmo clarki clarki Richardson. Oregon State Game

Comm., Corvallis, OR, 142 p.

Swanson, F.J., and G.W. Lienkaemper. 1978. Physical consequences of large organic debris in

Pacific Northwest streams. U.S. For. Serv. Gen. Tech. Rep. PNW-69, 12 p. Pacific

Northwest Forest and Range Experimental Station, Portland, OR.

Tave, D. 1993. Genetics for fish hatchery managers, 2nd ed. Van Nostrand Reinhold, New

York, NY, 415 p.

Taylor, E.B. 1991. A review of local adaptation in Salmonidae, with particular reference to

Pacific and Atlantic salmon. Aquaculture 98:185-207.

Taylor, L.R., and R.A.J. Taylor. 1977. Aggregation, migration and population mechanics.

Nature (London) 265:415-421.

Taylor, R.N. 1997. The spawning ecology of coastal cutthroat trout (Oncorhynchus clarki

clarki) and steelhead trout (O. mykiss irideus) in the Stone Lagoon watershed and the

potential for hybridization. M.S. Thesis, Humboldt State Univ., Arcata, CA.

Thompson, G.G. 1991. Determining minimum viable populations under the Endangered

Species Act. U.S. Dep. of Commerce, NMFS-NWFSC-198, 78 p.
241

Thorgaard, G.H. 1983. Chromosomal differences among rainbow trout populations. Copeia

1983:650-662.

Thorpe, J.E. 1987. Smolting versus residency: developmental conflict in salmonids. In M.J.

Dadswell, R.J. Klauda, C.M. Moffitt, R.L. Saunders, R.A. Rulifson, and J.E. Cooper

(eds.), Am. Fish. Soc. Symp. 1, p. 244-252, Boston.

Thorpe, J.E. 1989. Developmental variation in salmonid populations. J . Fish Biol. 35(Suppl.

A):295-303.

Thorson, R.M. 1980. Ice-sheet glaciation of the Puget lowland, Washington, during the Vashon

stage (late Pleistocene). Quat. Res., Orlando. 13:303-321.

Tipping, J.M. 1981. Cowlitz sea-run cutthroat study 1980-1981. Wash. State Game Dep. Fish.

Manage. Div., Rep. 81-12, Olympia, WA.

Tipping, J.M. 1986. Effect of release size on return rates of hatchery sea-run cutthroat trout.

Prog. Fish-Cult. 48(3):195-197.

Tipping, J.M., and S.G. Springer. 1980. Cowlitz River sea-run cutthroat creel census and life

history study. In Sea-run cutthroat trout census report, p. 106-126. Wash. State Game

Dep. Rep. 80-14, Olympia.

Tomasson, T. 1978. Age and growth of cutthroat trout, Salmo clarki clarki Richardson, in the

Rogue River, Oregon. M.S. Thesis, Oregon State Univ., Corvallis, 75 p.

Topping, P. Unpubl. data. Coastal cutthroat trout adult counts at Tumwater Falls, Deschutes

River, WA. (Available from WDFW, 600 Capitol Way N., Olympia, WA 98501-1091.)

Tripp, D., and P. McCart. 1983. Effects of different coho stocking strategies on coho and

cutthroat trout production in isolated headwater streams. Can. Tech. Rep. Fish. Aquat.

Sci. 1212. 176 p.

Trotter, P.C. 1987. Cutthroat - native trout of the west. Colorado Associated Univ. Press,

Boulder, Colorado, 219 p.

Trotter, P.C. 1989. Coastal cutthroat trout: A life history compendium. Trans. Am. Fish. Soc.

118:463-473.

Trotter, P. 1991. Cutthroat trout. In J. Stolz and J. Schnell (eds.), Trout. The Wildlife Series,

p. 236-265. Stackpole Books, Harrisburg, PA.

Trotter, P.C. 1997. Sea-run cutthroat trout: life history profile. In J.D. Hall, P.A. Bisson and R.E.

Gresswell (eds.), Sea-run cutthroat trout: biology, management, and future conservation,

p. 7-15. Am. Fish. Soc., Corvallis.
242

Trotter, P.C., P.A. Bisson, and B. Fransen. 1993. Status and plight of the searun cutthroat trout.

In J.G. Cloud and G.H. Thorgaard (eds.), Genetic Conservation of Salmonid Fishes,

p. 203-212. Plenum Press, New York.

U.S. Department of Commerce. 1968. [Natl. Oceanic Atmos. Admin. reprint 1983] Climate

atlas of the United States. Natl. Climatic Data Center, Ashville, NC, 80 p.

U.S. Forest Service (USFS). 1995. Jackson Creek watershed analysis and Little River

watershed analysis. Umpqua National Forest, Roseburg, Oregon.

U.S. Geological Survey (USGS). 1993. National water summary 1990-91. Hydrologic events

and stream water quality. U.S. Geological Survey Paper 2400, 590 p. (Available from

U.S. Government Printing Office, Washington D.C.)

University of Washington (UW). 1979. Unpubl. notes. Progress notes from Univ. Washington

lab, Seattle. (Available from Environmental Technical Services Division, NMFS, 525 NE

Oregon St., Portland, OR 97232.)

Valentine, J.W. 1966. Numerical analysis of marine molluscan ranges on the extratropical

northeastern Pacific shelf. Limnol. Oceanogr. 11:198-211.

Varley, J.D., and R.E. Gresswell. 1988. Status and management of Yellowstone cutthroat trout.

In R.E. Gresswell (ed.), Status and management of interior stocks of cutthroat trout,

p. 13-24. Am. Fish. Soc. Symp. 4, Bethesda, MD.

Via, S. 1987. Genetic constraints on the evolution of phenotypic plasticity. In V. Loeschke

(ed.), Genetic constraints on adaptive evolution, p. 47-71. Springer Verlag, Berlin.

Via, S. 1993. Adaptive phenotypic plasticity: target or by product of selection in a variable

environment? Am. Nat. 142:352-365.

Viereck, L.A., and E.L. Little. 1972. Alaska trees and shrubs. USDA Forest Service,

Agriculture Handbook 410, U.S. Gov. Printing, Washington DC, 265 p.

Voight, H.N., and D.B. Gale. 1998. Distribution of fish species in tributaries of the lower

Klamath river: an interim report, FY 1996. Habitat Assessment and Biological

Monitoring Division, Yurok Tribal Fish. Prog. Tech. Rep. No. 3., 71 p. (Available

from Yurok Tribal Fisheries Program, 15900 Hwy 101 N. Klamath, CA 95548.)

Voight, H.N., and T.R. Hayden. 1997. Direct observation assessment of coastal cutthroat trout

abundance and habitat utilization in the South Fork Smith River, California. In J.D. Hall,

P.A. Bisson and R.E. Gresswell (eds.), Sea-run cutthroat trout: biology, management, and

future conservation, p. 175-176. Am. Fish. Soc., Corvallis.

Wald, G. 1958. The significance of vertebrate metamorphosis. Science (NY) 128:1481-1490.
243

Waples, R.S., and D.J. Teel. 1990. Conservation genetics of Pacific salmon. I. Temporal

changes in allele frequency. Conserv. Biol. 4:144-156.

Waples, R.S. 1991a. Definition of “species” under the Endangered Species Act: Application to

Pacific salmon. NOAA Tech. Memo. NMFS, F/NWC-194, 29 p.

Waples, R.S. 1991b. Pacific Salmon, Oncorhynchus spp., and the definition of “species” under

the Endangered Species Act. U.S. Nat. Mar. Fish. Rev., 53 (3): 11-22.

Waring, R.H., and J.F. Franklin. 1979. Evergreen coniferous forests of the Pacific Northwest.

Science 204:1380-1386.

Washington Department of Fish and Wildlife (WDFW). 1995. Fish passage program progress

performance report for the biennium 1993-1995. Wash. Dep. Fish Wildl., Olympia.

(Available from WDFW, 600 Capitol Way N., Olympia, WA 98501-1091.)

Washington Department of Fish and Wildlife (WDFW). 1997. 1997 current brood documents

for cutthroat trout hatcheries, 3 March 1997. 280 p. (Available from WDFW, P.O. Box

43151, Olympia, WA 98504.)

Washington Department of Fish and Wildlife (WDFW). 1998a. 1998 Washington salmonid

stock inventory, coastal cutthroat trout appendix. Wash. Dep. Fish. Wildl., Olympia, WA.

280 p. (Available from WDFW, P.O. Box 43151, Olympia, WA 98504.)

Washington Department of Fish and Wildlife (WDFW). 1998b. Spring 1998 Hatchery trout

stocking plan for Washington lakes and streams. Wash. Dep. Fish. Wildl., Olympia,

WA. (Available through Internet, www.wa.gov/wdfw/)

Washington Department of Fish and Wildlife (WDFW). 1998c. Memo from WDFW (unsigned)

to O. Johnson. 14 Oct. 1998. 7 p. + attach. (Available from Environmental and

Technical Services Division, NMFS, 525 NE Oregon St., Portland, OR 97232.)

Washington Department of Fisheries, Washington Department of Wildlife, and Western

Washington Treaty Indian Tribes, (WDF, WDW, and WWTIT). 1993. 1992 Washington

state salmon and steelhead stock inventory (SASSI). Wash. Dep. Fish Wildl. 212 p. + 3

append. Appendix 1: Hood Canal and Strait of Juan de Fuca (December 1994, 424 p.),

North Puget Sound (June 1994, 418 p.), and South Puget Sound (September 1994, 371 p.)

volumes. Appendix 2: Coastal stocks (August 1994, 587 p.). Appendix 3: Columbia

River stocks (June 1993, 580 p.). (Available from WDFW, P.O. Box 43151, Olympia,

WA 98504.)

Waters, E. 1993. Winter Habitat Utilization of Radio-Tagged Coastal Cutthroat Trout. Thesis,

North Carolina State Univ., Raleigh, 43 p.
244

Weitkamp, L.A., T.C. Wainwright, G.J. Bryant, G.B. Milner, D.J. Teel, R.G. Kope, and R.S.

Waples. 1995. Status review of coho salmon from Washington, Oregon, and California.

U. S. Dep. of Commerce, NMFS-NWFSC-24, 258 p.

Wenburg, J.K. 1998. The coastal cutthroat trout (Oncorhynchus clarki clarki): genetic

population structure, migration patterns and life history traits. Ph.D. Dissertation, Univ.

Washington, Seattle.

Wenburg, J.K., P. Bentzen, and C.J. Foote. 1998. Microsatellite analysis of genetic population

structure in an endangered salmonid: the coastal cutthroat trout (Oncorhynchus clarki

clarki). Mol. Ecol. 7:733-749.

White, J. 1997. The loss of habitat in Puget Sound. People for Puget Sound, 26 p. (Available

from Environmental and Technical Services Division, NMFS, 525 NE Oregon St.,

Portland, OR 97232.)

Whitney, S. 1985. The Audubon Society nature guides. Western forests. Knoph, New York,

671 p.

Willers, W.B. 1991. Trout Biology. Lyons & Burford Publishers, New York, 273 p.

Williams, G.C. 1966. Adaptation and natural selection. A critique of some current evolutionary

thought. Princeton Univ. Press, Princeton, NJ, 307 p.

Williams, J.E., and W. Nehlsen. 1997. Status and trends of anadromous salmonids in the coastal

zone with special reference to sea-run cutthroat trout. In J.D. Hall, P.A. Bisson and R.E.

Gresswell (eds.), Sea-run cutthroat trout: biology, management, and future conservation,

p. 37-42. Am. Fish. Soc., Corvallis.

Williams, T. Unpubl. data for coastal cutthroat trout meristics. NMFS, Southwest Fisheries

Science Center, 3150 Paradise Drive, Tiburon, CA 94920-1299.

Williams, T.H., K.P. Currens, N.E. Ward III, and G.H. Reeves. 1997a. Genetic population

structure of coastal cutthroat trout. In J.D. Hall, P.A. Bisson and R.E. Gresswell (eds.),

Sea-run cutthroat trout: biology, management, and future conservation, p. 16-17. Am.

Fish. Soc., Corvallis.

Williams, T.H., G.H. Reeves, and K.P. Currens. 1997b. Genetic diversity of coastal cutthroat

trout. In R.E. Gresswell, P. Dwyer and R.H. Hamre (eds.), Wild Trout VI, p. 87-88,

Bozeman, MT.

Withler, F.C. 1982. Transplanting Pacific salmon. Can. Tech. Rep. Fish. Aquat. Sci. 1079:27.

Withler, R.E. 1988. Genetic consequences of fertilizing chinook salmon (Oncorhynchus

tshawytscha) eggs with pooled milt. Aquaculture 68:15-25.
245

Wood, C.C. 1995. Life history variation and population structure in sockeye salmon. In J.L.

Nielsen (ed.), Evolution and the aquatic ecosystem: defining unique units in population

conservation, Am. Fish. Soc. Symp. 17, p. 195-216. Bethesda, MD.

Wright, S. 1973. Resident and anadromous fishes of the Chehalis and Satsop Rivers in the

vicinity of Washington Public Power Supply System’s proposed nuclear project No. 3.

Wash. Dep. Fish. Rep., Olympia. 26 p. (Available from WDFW, 600 Capitol Way N.,

Olympia, WA 98501-1091.)

Wright, S. 1978. Evolution and the genetics of populations: variability within and among

natural populations. Univ. Chicago Press, Chicago, 580 p.

Wyatt, B. 1959. Observations on the movements and reproduction of the Cascade form of

cutthroat trout. M.S. Thesis, Oregon State College, Corvallis.

Wydoski, R.S., and R.R. Whitney. 1979. Inland fishes of Washington. Univ. Washington

Press, Seattle.

Young, M.K. 1995. Summer movements and habitat use by Colorado River cutthroat trout

(Oncorhynchus clarki pleuriticus) in small, montane streams. Can. J. Fish. Aquat. Sci.

53:1403-1408.

Yurok Tribal Fisheries. Unpubl. data. Presence/absence data for the Klamath River. Yurok

Tribal Fisheries Program, 15900 Highway 101 North, Klamath, CA 95548.

Zaugg, W.S. 1981. Advanced photoperiod and water temperature effects on gill Na-K super(+)

adenosine triphosphatase activity and migration of juvenile steelhead (Salmo gairdneri).

Can. J. Fish. Aquat. Sci. 38(7):758-764.

Zaugg, W.S., and L.R. McLain. 1970. Adenosinetriphosphatase activity in gills of salmonids:

seasonal variations and salt water influences in coho salmon, Oncorhynchus kisutch.

Comp. Biochem. Physiol. 35(587-596).

Zaugg, W.S., and L.R. McLain. 1972. Changes in gill adenosinetriphosphatase activity

associated with parr-smolt transformation in steelhead trout, coho, and spring chinook

salmon. J. Fish. Res. Board Can. 29:167-171.

Zaugg, W.S., and H.H. Wagner. 1973. Gill ATPase activity related to parr-smolt transformation

and migration in steelhead trout (Salmo gairderi): influence of photoperiod and

temperature. Comp. Biochem. Physiol. 45B:955-965.

Zimmerman, C.E. 1995. Population structure of coastal cutthroat trout (Oncorhynchus clarki

clarki) in the Muck Creek Basin, Washington. M.S. Thesis, Oregon State Univ.,

Corvallis.
246
247

APPENDIX A: HATCHERY RELEASES
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265

APPENDIX B: THE RISK MATRIX METHOD
266
267

APPENDIX B: THE RISK MATRIX METHOD

To tie the various risk considerations into an overall assessment of extinction risk for

each evolutionarily significant unit (ESU), Biological Review Team (BRT) members used a

matrix form (Table B-1) to score risks in a number of categories. The following method was

used for scoring and reaching an overall conclusion regarding extinction risk for an ESU:

1. After reviewing previous documents and hearing presentations and discussions during the

meeting, each BRT member filled in as much of the matrix as possible, scoring the

various factors according to the relative degree of risk based on available information.

2. Scores from individual members were tallied on a single sheet and summarized.

3. The BRT reached an overall conclusion regarding the degree of extinction risk facing

each ESU after steps 1 and 2 were completed and discussed.

The following is a list of factors considered. This is not a complete list, but covers

considerations that have been important in past status reviews. Specific considerations within

each area are discussed more fully in the main body of this report.

Risk Assessment Factors

Abundance

Questions regarding abundance can be put into three subcategories:

Small population risks—Is the overall ESU (or discrete populations within the ESU) at such

low abundance that small-population risks (random genetic effects, Allee effects, random

demographic or environmental effects) are likely to be significant?

Distribution—Do present populations adequately represent historical patterns of geographic

distribution and ecological/genetic/life-history diversity? Does fragmentation of previously

connected populations pose a risk? Is the ESU at risk in this subcategory in a significant portion

of its range?

In the status review for coastal cutthroat trout (Oncorhynchus clarki clarki), BRT

members explicitly considered the risk associated with reduction in life-history diversity.

Habitat capacity—Is abundance limited by current habitat capacity? If so, is current habitat

capacity adequate to ensure continued population viability? (Here, only habitat capacity is
268
269

considered. Habitat quality as it affects trends or productivity is considered in the next section,

“Trends, productivity, and variability.”)

Trends, productivity, and variability

Again, considerations can be put into three subcategories:

Population trends—Is the overall ESU (or populations within it) declining in abundance at a

rate that risks extinction in the near future? Is variation in population abundance, in combination

with average abundance and trends, sufficiently high to cause risk of extinction?

Productivity—Has population productivity declined or is it declining toward the point where

populations may not be sustainable? Is there evidence that natural populations are/can be selfsustaining without the infusion of hatchery-reared fish?

Limiting factors—Are there factors (such as poor freshwater or ocean habitat quality, harvest,

human-induced mortality, or interactions with other species) that currently limit productivity to

the point where populations may not be sustainable? Are such factors expected to continue? Are

there natural or anthropogenic factors that have increased variability in reproduction or survival

for populations beyond the historic range of environmental variability? Are there factors that

have increased the vulnerability of populations to natural levels of environmental variability?

Genetic integrity

Genetic integrity can be affected through either random effects (included earlier under

“Small-population risks”) or directional effects. The major sources of directional effects of

concern here are introduced genotypes, interactions with local or non-native hatchery fish, or

artificial selection (e.g., through selective harvest or habitat modification). These directional

effects pose two major types of risk for natural populations:

Loss of fitness—Has interbreeding or artificial selection reduced fitness of natural populations to

the point that this is a significant extinction risk factor?

Loss of diversity—Has there been a substantial loss of diversity within or between populations?

For both types of risk, it may also be important to ask this question: Even if these

interactions are not occurring at present, have past events substantially affected fitness and/or

diversity of natural populations within the ESU to the extent that long-term population

sustainability is compromised?
270

Other risks

Are there other factors that indicate risks to the sustainability of the ESU or component

populations? These factors may include disease prevalence, predation, and changes in lifehistory characteristics such as spawning age or size.

Recent events

This category was included to recognize events (natural or anthropogenic) that have

predictable effects on risk for the ESU but have occurred too recently to be reflected in

abundance, trend, genetic, or other data considered by the BRT. Examples might include recent

changes in management (such as harvest rates or hatchery practices), anthropogenic changes in

the environment (habitat degradation or enhancement), or natural events (such as floods or

volcanic eruptions). Recent changes in management were considered only where they were

already fully or partially implemented and had reasonably predictable consequences.

Scoring Categories

Levels of risk—Individual factors

Risk from individual factors were ranked on a scale of 1 (very low risk) to 5 (high risk):

1) Very low risk—Unlikely that this factor contributes significantly to risk of extinction, either

by itself or in combination with other factors.

2) Low risk—Unlikely that this factor contributes significantly to risk of extinction by itself, but

some concern that it may in combination with other factors.

3) Moderate risk—This factor contributes significantly to long-term risk of extinction, but does

not in itself constitute a danger of extinction in the near future.

4) Increasing risk—Present risk is low or moderate, but is likely to increase to high in the

foreseeable future if present conditions continue.

5) High risk—This factor by itself indicates danger of extinction in the near future.

Levels of risk—Recent events

The “Recent Events” category does not represent specific risk factors, but rather factors

that may alter the overall risk score for an ESU from the conclusion based on data available to

date. This category was scored as follows:
271

++ Expect a strong improvement in status of the ESU

+ Expect some improvement in status

0 Neutral effect on status

- Expect some decline in status

— Expect strong decline in status

Levels of risk—Overall summary

The summary score of overall risk uses categories that correspond to definitions in the

Endangered Species Act (ESA): in danger of extinction, likely to become endangered in the

foreseeable future, or neither. (Note, however, that these scores do not correspond to

recommendations for a particular listing action because they are based only on past and present

biological conditions of the populations and do not completely evaluate conservation measures

as required under the ESA.)

This summary score is not a simple average of the risk factors for individual categories,

but rather a judgment of overall risk based on likely interactions among factors. A single factor

with a score of high risk may be sufficient to result in an overall score of “in danger of

extinction”; this overall score, however, could also result from a combination of several factors

with low or moderate risk scores.

Evaluation of Uncertainty

As discussed in the main document (see “Overall Evaluation of Risk and Uncertainty,”

p. 141), the BRT used two methods to characterize the uncertainty underlying their risk

evaluations. The outcomes of the two methods were generally consistent. Results are described

in “Summary and Conclusions of Risk Assessments,” p. 194.

Results for the Coastal Cutthroat Trout Status Review

BRT scores for the three major categories of risk for each coastal cutthroat trout ESU are

summarized in Table B-2. We do not summarize the “Other Risks” and “Recent Events”

categories here because factors included in these categories varied among ESUs; these factors are

discussed in the main body of this report. The Upper Willamette River ESU was not considered

in risk evaluations because the U.S. Fish and Wildlife Service has jurisdiction over the coastal

cutthroat trout in that ESU.
272
273

APPENDIX C: ADDITIONAL INFORMATION
274
275
276
277
278
279

GLOSSARY
280
281

GLOSSARY

Note: Bold-faced words are defined elsewhere in this glossary.

abiotic

Devoid of life; cf. biotic.

ADFG

Alaska Department of Fish and Game

adfluvial

Fish that migrate between lakes and rivers or streams. These fish may also be called

lacustrine and are sometimes further characterized as to whether they spawn in outlet tributaries

(allacustrine) or inlet tributaries (lacustrine-adfluvial).

AFS

American Fisheries Society

alevin

Life-history stage of a salmonid immediately after hatching and before the yolk-sac is

absorbed. Alevins usually remain buried in the gravel in or near a series of redds until the yolk

sac is absorbed, after which they swim up and enter the water column.

allele

An alternative form of a gene that can occur at the same location (locus) on homologous

(paired) chromosomes. A population can have many alleles for a particular locus, but an

individual can carry no more than two alleles at a diploid locus.

allochthonous

Materials from outside a system, such as leaves and insects that fall from terrestrial plants

into a stream.

allacustrine

Fish that rear in lakes and spawn in outlet tributaries of lakes.

allozymes

Alternative forms of an enzyme that have the same function, are produced by different

alleles, and are often detected by protein electrophoresis.

amphidromy (adj. amphidromous)

Migratory fishes whose migrations between fresh water and sea are not exclusively for

breeding but occur regularly at some other stage of the life cycle.
282

anadromy (adj. anadromous)

The life-history pattern that features early juvenile development in fresh water, migration to

seawater, and a return to freshwater for spawning. The coastal cutthroat trout (Oncorhynchus

clarki clarki) is considered an anadromous subspecies, but not all members of the subspecies

necessarily go to sea each year. Interior subspecies of O. clarki are considered nonanadromous

because no members of those subspecies go to sea.

ANOVA (analysis of variance)

A statistical technique for estimating how much of the variability in a set of observations can

be ascribed to different causes (i.e., partitioning of variance).

anthropogenic

Caused or produced by human action.

artificial propagation

Artificial propagation of salmon refers to the practice of manually spawning adult fish and

rearing the progeny in hatcheries, egg boxes, remote site incubators, or other facilities before

release into the natural environment.

assortative mating

Preference for mating between individuals with like genotypes or phenotypes.

basibranchial teeth

Teeth on the median ventral plate (base of tongue) overlying basibranchial bones between the

gill arches. Basibranchial teeth are often considered a distinguishing feature of cutthroat trout

and used to separate them from rainbow and redband trout or steelhead. However, not all

populations/forms of cutthroat trout have these teeth, and some rainbow/redband populations do

have them. Basibranchial teeth in juvenile fish of all three species may be undetectable.

Biological Review Team (BRT)

The team of scientists who evaluated a scientific information considered in the National

Marine Fisheries Service status review.

biotic

Pertaining to life or living organisms; caused or produced by or comprising living organisms;

cf. abiotic.

CDFG

California Department of Fish and Game

coefficient of condition or condition factor (K)

Numerical index representing the relationship between body weight and length of a fish. The

condition factor can be represented by the equation K = weight/(length)3

, with weight expressed

in grams and length in millimeters.
283

co-managers

Federal, state, county, local, and tribal agencies that cooperatively manage salmonids in the

Pacific Northwest.

continuous variation

Variations between individuals of a population in a character or trait in which the differences

are slight and occur as a continuous series.

CPUE

catch-per-unit effort

dendrogram

Branching diagram, sometimes resembling a tree, that depicts similarities and differences

between groups or samples. See multidimensional scaling.

discrete variation

Variations between individuals of a population in a character or trait in which the differences

are marked and do not occur as a continuous gradient.

DNA (deoxyribonucleic acid)

DNA is a complex molecule that carries an organism’s heritable information. The two types

of DNA commonly used to examine genetic variation are mitochondrial DNA (mtDNA), a

circular molecule that is maternally inherited, and nuclear DNA, which is organized into a set of

chromosomes (see also allele and electrophoresis).

egg boxes

Stream-side boxes where fertilized salmon eggs are incubated until the fry stage, when the

juveniles swim out of the box and enter the stream.

electrophoresis

Electrophoresis is the movement of charged particles in an electric field. This process has

been developed as an analytical tool to detect genetic variation revealed by charge differences on

proteins or molecular weight in DNA. Data obtained by electrophoresis can provide insight into

levels of genetic variability within populations and the extent of genetic differentiation between

them.

endangered species

A species in danger of extinction throughout all or a significant portion of its range.

EPA

U.S. Environmental Protection Agency

ESA

U.S. Endangered Species Act
284

escapement

The fish in a population or run that “escape” all fisheries and return to the freshwater

spawning area.

evolutionarily significant unit (ESU)

An ESU represents a distinct population segment under the Endangered Species Act that 1) is

substantially reproductively isolated from nonspecific populations and 2) represents component

an important component of the evolutionariy legacy of the species.

euryhaline

Organisms that tolerate a wide range of salinities.

FEMAT

Forest Ecosystem Management Assessment Team

fluvial

Pertaining to rivers and river action, this term for a life-history form of cutthroat trout has at

least two regional connotations. The term may mean fish that are nonanadromous but conduct

extensive feeding or spawning migrations within river systems (cf. freshwater migrating,

potamodromous, or riverine). The term may also refer to fish that conduct only small

migrations and reside primarily in headwater streams or upper tributaries (cf. nonmigrant).

Because the term has multiple meanings, its use is avoided in this status review.

freshwater forms

An inclusive description of the life-history forms (freshwater migrants and nonmigrants)of

cutthroat trout that occur within fresh water and do not enter seawater (cf. nonanadromous).

freshwater migrant/migratory

Cutthroat trout that migrate solely within the freshwater environment. These fish primarily

reside in rivers or lakes while feeding or overwintering, but typically return to smaller tributaries

or headwater streams to spawn (cf. nonmigrant/migratory, potamodromous, riverine,

lacustrine).

fry

Stage in the salmonid life history when the juvenile has absorbed its yolk sac and leaves the

gravel of the redd to swim up into the water column.

GDU

Genetic Diversity Unit, which represents subsets of Major Ancestral Lineages (MALs).

genetic distance

A quantitative measure of genetic difference between a pair of samples.

genetic drift

The occurrence of random changes in the gene frequencies of populations.
285

genome (adj. genomic)

The total genetic constitution of an organism.

genotype

The set of genes possessed by an individual organism.

haplotype

The collective genotype of a number of closely linked loci; the constellation of alleles

present at a particular region of genomic or mitochondrial DNA.

hatchery produced

Any fish reared in a hatchery (cf. natural fish, naturally spawning fish).

hatchery stock

A population of fish associated with a hatchery. A hatchery stock is spawned and reared in

a hatchery before release. Historically, hatchery stocks were often transferred among hatcheries,

but this practice is now less common.

heterozygous

The condition of having two different alleles at a given locus of a chromosome pair.

heterozygosity

A measure of allelic diversity at a locus (or averaged over several loci) whereby alternate

alleles at a locus are different.

homologous chromosome

Structurally similar chromosomes with the same sequence of genes and that pair during

division of the cell nucleus.

hybridization

Reproduction between individuals of different genetic compositions, typically belonging to

separate species, that results in hybrid offspring (e.g., cutthroat trout × rainbow trout).

karyotype

The chromosome complement of a cell, individual, or group.

introgression

Introduction by interbreeding or hybridization of genes from one population or species into

another.

isozymes

One of several forms of an enzyme, produced by different nonallelic loci in an individual

organism’s genome. Often misused to mean allozyme.
286

iteroparous

Having the ability to reproduce over more than one reproductive or spawning period. Among

Pacific salmonids in the genus Oncorhynchus, Pacific trout such as O. clarki or O. mykiss are

iteroparous; Pacific salmon, such as O. kisutch or O. keta are typically semelparous and die soon

after spawning.

jacks

Usually used to refer to Pacific salmon; means male salmon that return from the ocean to

spawn a year or more before full-sized adults return.

lacustrine

Having to do with a lake; often used synonymously with adfluvial to describe fish that spend

most of their life in lakes.

life-history form

Used in this status review to describe coastal cutthroat trout based upon the primary activity

or physical location of the fish when sampled (e.g., saltwater migrant, freshwater migrant,

freshwater forms, or nonmigrant).

life-history stage

Used in this status review as a way to describe salmonids based upon the developmental

stage of the fish (e.g., egg, alevin, smolt, or adult).

locus (pl. loci)

The site on a chromosome where a gene is found; often used more or less synonymously with

gene (cf. polymorphic locus, allozymes, isozymes).

LWD

Large woody debris, which is important to trout habitat in small streams in coastal

watersheds.

MAL

Major Ancestral Lineage

meristic trait

A discretely varying and countable trait (e.g., number of fin rays or basibranchial teeth); cf.

traits with continuous variation (e.g., weight, length) or discrete variation (e.g., male, female,

mature, immature).

metapopulation

A group of partially isolated populations (or subpopulations) belonging to the same

biological species (or subspecies) and connected by migratory pathways. These partially isolated

populations or subpopulations can exchange individuals, which are potentially able to recolonize

sites within the metapopulation from which the species or subspecies recently became extinct.
287

migrants

Cutthroat trout that move at regular intervals, usually seasonally, from natal spawning areas

to feeding and refuge areas. Migratory movements may be to the ocean, an estuary, and/or

within freshwater rivers and lakes.

minimum spanning tree (or network)

An undirected network in which all the samples are linked together with the smallest possible

network. Included in the network are linkages between nearest neighbors. The network can be

superimposed on PCA and MDS plots to detect local distortions, in which pairs of points may

appear close in one dimension but far apart in another dimension.

minimum viable population

The smallest number of individuals necessary to give a population a high probability of

surviving over a specified period of time.

mitochondrial DNA (mtDNA)

The DNA genome contained within mitochondria and encoding a small subset of

mitochondrial functions; mtDNA is typically circular and 15-20 kilobases in size, containing

little noncoding information between genes.

morphology (adj. morphological)

Description of an organism’s form and structure, with special emphasis on external features.

multidimensional scaling (MDS)

An ordination technique for analyzing genetic distances between samples in

multidimensional space (usually two or three dimensions for visualization). The technique is

used to reduce the multidimensional space represented by allelic frequencies at several loci to a

few dimensions without losing the complex genetic relationships among samples. MDS is

considered superior to principal component analysis (PCA) for some genetic data because it

does not assume linearity and hence does not potentially distort variation appearing in some

population structures, such as step clines in allelic frequencies. MDS of genetic distances can

detect nonhierarchical geographic structure without precluding detection of hierarchies.

MVP

minimum viable population

native fish

Fish indigenous to a particular region, place, or stream.

natural fish

Fish produced by parents spawning in a river or lake bed, as opposed to a controlled

environment such as a hatchery. Natural fish may include “wild” fish; “wild “ is often defined to

mean fish native to a region and naturally spawning, with little if any hatchery ancestry.

However, “wild” has a variety of local and regional definitions and its use is avoided in this

status review.
288

naturally spawning fish

Fish spawning in a river or lake rather than in a controlled environment (such as a hatchery).

NMFS

National Marine Fisheries Service

nonanadromous

Describes fish that occur within fresh water and do not migrate to saltwater.

nonmigrant

Cutthroat trout that do not make extensive migrations but maintain small home ranges in

upper tributaries or headwater streams. Nonmigrants are sometimes called residents or Cascade

types, but this status review avoids these terms because they may have different regional

connotations.

NWFSC

Northwest Fisheries Science Center

ODFW

Oregon Department of Fish and Wildlife

ONRC

Oregon Natural Resources Council

otolith

Crystalline calcium-carbonate structures within the inner ear of fish. These structures have

distinctive shapes, sizes, and internal and surface features that can be used for age determination

and species identification.

otolith primordia

The core region of the otolith first formed during embryonic development. Growth of the

primordia region begins before hatching and chemical analysis can provide information about

whether the maternal parent went to sea.

phenotype

The appearance (or other measurable characteristic) of an organism that results from

interaction of the genotype and environment.

phylogeny

The evolutionary history of a group or lineage; the description and explanation of the

temporal sequence of morphological, ecological, and biogeographical changes of a taxon.

PINEs

paired interspersed nucleotide elements
289

PIT tag

The PIT (passive integrated transponder) tag is an injectable, internal, radio-type tag that

allows unique identification of a marked fish passing within a few inches of a monitoring site.

The tag has been most effective in providing precise information on migrational timing and

juvenile fish behavior when marked fish can be channeled past a monitoring site at a dam or weir

(e.g., the fish bypass system at Snake River mainstem dams) or recaught above a barrier.

PNRBC

Pacific Northwest River Basins Commission

polymorphic

Having more than one form (e.g., polymorphic gene loci have more than one allele).

polymorphic locus

A locus characterized by more than one allele in a sample. If different alleles can be detected

at a gene locus, the locus is considered polymorphic. If all alleles are of the same type, the locus

is considered monomorphic. Many population genetic analyses are based on the frequency of

different alleles at polymorphic loci.

polytypic

A taxon comprising more than two subordinate principle taxa or distinct life-history forms.

Cutthroat trout are a polytypic species.

population

A group of individuals of a species living in a certain area that maintain some degree of

reproductive isolation.

potamodromous

Description of an organism that either 1) migrates within river systems or 2) is nonanadromous, residing solely in fresh water. Because the term has two common usages, it has

been avoided in this status review and replaced with freshwater migrants and nonmigrants or

the inclusive term freshwater forms (cf. riverine, lacustrine, anadromous, resident).

principal component analysis (PCA)

An ordination technique for analyzing data from several variables, such as allelic frequencies

or morphological data. The method finds linear trends (principal components) through the

clouds of sample points in multidimensional space. These principal components account for the

greatest amount of variation present in the data. The residual variance is removed from the data

with the calculation of each successive principal component, (cf. multidimensional scaling).
290

protein electrophoresis

An analytical laboratory technique that measures differences in the amino acid composition

of proteins from different individuals. Because the amino acid sequence of proteins is coded for

by DNA, data provided by protein electrophoresis provide insight into levels of genetic

variability within populations and the extent of genetic differentiation between them. See

electrophoresis.

redd counts

Most salmonids deposit their eggs in a series of nests called redds, which are dug in the

streambed or lake substrate by the female. Most Pacific salmon redds occur in predictable areas

and are easily identified by an experienced observer by their shape, size, and color (lighter than

surrounding areas because silt has been cleaned away). However, several factors, including

small size, infrequent distribution, and apparent confusion with lamprey redds, make cutthroat

trout redds difficult to detect; cf. spawning surveys.

resident

Life-history form of 1) coastal cutthroat trout that do not conduct extensive movements from

natal spawning areas and tend to remain in upper tributaries and headwater streams; 2) any fish

that does not migrate to seawater (nonanadromous). Because the term may have multiple

meanings, its use is avoided in this status review.

riverine (river migrant)

A freshwater migrating cutthroat trout that primarily resides in rivers during feeding

migrations, but may return to smaller tributaries or headwater streams to spawn or for winter

refuge. Riverine fish may or may not go to estuaries or the open sea in some years.

rKm

river kilometer

RSI

remote site incubator

salmonid

Of, belonging to, or characteristic of the family Salmonidae, which includes the salmon,

trout, char, and whitefish. Pacific salmonid is used in this status review to refer to fish native to

the coast of western North America in either the genus Salvilinus (e.g., char, bull trout, and Dolly

Varden) or Oncorhynchus, including five species of Pacific salmon (sockeye, pink, chum,

chinook, and coho) and species of Pacific trout (e.g. cutthroat, golden, and steelhead/rainbow

trout).

saltwater migrant/migratory

Cutthroat trout that migrate to salt water. Migration to the estuary or ocean environment

generally occurs in the spring. These fish typically return to fresh water to overwinter in rivers

or lakes, then migrate to smaller tributaries or headwater streams to spawn or return to the marine

environment to feed (cf. anadromy).
291

SaSI

Salmonid Stock Inventory, which is a cooperative program by WDFW and WWTIT to

inventory and evaluate the status of Pacific salmonids (salmon, trout, and char) in Washington

State. This program follows the SASSI format. The SaSI report is referenced as “WDFW

1998a” in this status review.

SASSI

Salmon and Steelhead Stock Inventory, which is a cooperative program by WDFW and

WWTIT to inventory and evaluate the status of Pacific salmonids in Washington State. The

SASSI report is a series of publications from this program referenced as “WDF et al. 1993” in

this status review.

sea run

Describes a coastal cutthroat trout that has gone to sea at least once (cf. anadromy).

semelparous

Having only one reproductive or spawning period and dies after spawning. Pacific salmon,

such as O. kisutch or O. keta, are typically semelparous.

smolt

verb -The physiological process that prepares a juvenile salmonid to survive the transition

from fresh water to salt water.

noun - A juvenile anadromous fish that has smolted.

spawning surveys

Counts of redds (and fish carcasses of Pacific salmon) to estimate spawner escapement and

identify habitat being used by spawning fish. Annual surveys can be used to compare the

relative magnitude of spawning activity between years. These surveys are rarely conducted for

cutthroat trout due to the difficulty in identifying cutthroat trout redds and the rarity of carcasses

in iteroparous species.

species

biological - A small group of organisms formally recognized by the scientific community as

distinct from other groups.

legal - National Oceanic and Atmospheric Administration policy considers a species as

defined by the ESA to include biological species, subspecies, and ESUs.

stochasticity

Random events or behaviors that are not deterministic.

swim up

The time in the life cycle of salmon when alevins, having absorbed their yolk sacs, transition

into fry by swimming from the gravel of the redd into the water column.
292

sympatric

Describes populations, species, or taxa occurring together in the same geographical areas

where they may occupy the same habitat (biotic sympatry) or different habitats (neighboring

sympatry) within the same geographical area. Implies, especially when used in a genetic context,

the opportunity to interbreed.

threatened species

A species not presently in danger of extinction but likely to become so in the foreseeable

future.

total escapement

A combination of all counts and estimates of returning fish in a particular group (e.g.,

species, stock, run) for a river or management unit.

trophic

Pertaining to nutrition. A trophic migration would be a movement of fish to a feeding area.

USGS

United States Geological Survey

WDFW

Washington Department of Fish and Wildlife, which co-manages salmonids and salmonid

fisheries in Washington State with WWTIT and other fisheries groups. The agency was formed

in the early 1990s by combining the Washington Department of Fisheries and Washington

Department of Wildlife.

wild

See natural fish.

WWTIT

Western Washington Treaty Indian Tribes, an organization of Native American tribes with

treaty fishing rights recogized by the United States. WWTIT co-manages salmonids and

salmonid fisheries in western Washinton in cooperation with WDFW and other fisheries groups.