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 National Marine Fisheries Service Northwest Fisheries Science Center Coastal Zone and Estuarine Studies Division 2725 Montlake Blvd. E. Seattle WA 98112-2097 January 1999 U.S. DEPARTMENT OF COMMERCE William Daley, Secretary National Oceanic and Atmospheric Administration D. James Baker, Administrator National Marine Fisheries Service Rolland A. Schmitten, Assistant Administrator for Fisheries

The Northwest Fisheries Science Center of the National Marine Fisheries Service, NOAA, uses the NOAA Technical Memorandum NMFS series to issue informal scientific and technical publications when complete formal review and editorial processing are not appropriate or feasible due to time constraints. Documents published in this series may be referenced in the scientific and technical literature.

The NMFS-NWFSC Technical Memorandum series of the Northwest Fisheries Science Center continues the NMFS-F/NWC series established in 1970 by the Northwest & Alaska Fisheries Science Center, which has since been split into the Northwest Fisheries Science Center and the Alaska Fisheries Science Center. The NMFS-AFSC Technical Memorandum series is now being used by the Alaska Fisheries Science Center.

Reference throughout this document to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA.

This document should be cited as follows:

Johnson, O.W., M.H. Ruckelshaus, W.S. Grant, F.W.
Waknitz, A.M. Garrett, G.J. Bryant, K. Neely, and J.J.
Hard. 1999. Status review of coastal cutthroat trout
from Washington, Oregon, and California. U.S. Dept.
Commer., NOAA Tech. Memo. NMFS-NWFSC-37,
292 p.

This document is available to the public through:

National Technical Information Service
U.S. Department of Commerce
5285 Port Royal Road
Springfield, VA 22161
1-800-553-8647
orders@ntis.fedworld.gov

The BRT for coastal cutthroat trout consisted of the following members from NWFSC: Peggy Busby, Laurie Weitkamp, F. William Waknitz, 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 (SWFSC), Dr. Tommy Williams; and from the NMFS Southwest Region, Greg Bryant and Craig Wingert.

CONTENTS

List of Figures

List of Tables

Executive Summary

Acknowledgements

Introduction

Scope and Intent of the Present Document

Key Questions in ESA Evaluations

The "Species" Question

Artificial Propagation

The "Extinction Risk" Question

Summary of Coastal Cutthroat Trout Petition

Terminology

General Biology

Geographic Distribution

Information Relating to the Species Question

Environmental Information

Geological and Climatic Events

Ecoregions

Coast Range Ecoregion (#1)

Puget Lowland Ecoregion (#2)

Willamette Valley Ecoregion (#3)

Cascades Ecoregion (#4)

Sierra Nevada Ecoregion (#5)

Eastern Cascades Slopes and Foothills Ecoregion (#9)

Coastal British Columbia

Southeastern and southcentral Alaska

Biogeography

Vegetation

Sitka spruce zone

Redwood zone

Western hemlock zone

Alpine and subalpine zones

Analyses of vegetation types

Zoogeography

Marine fishes

Marine invertebrates

Freshwater fishes

Estuarine fishes

Amphibians

Life History

Patterns of Life-History Variation

Life-history forms

Nonmigratory coastal cutthroat trout

Freshwater-migratory coastal cutthroat trout

Saltwater-migratory coastal cutthroat trout

Trophic migratory model

Mechanisms of life-history expression

Life-History Stages

Spawning

Incubation and emergence

Juvenile movements

Smoltification and seawater entry

Estuary and ocean movement/migration

Adult freshwater migrations

Straying and refuge or feeding migrations versus reproductive straying

Interactions of Coastal Cutthroat Trout with Other Salmonids

Temperature Tolerance in Coastal Cutthroat Trout

Genetic Information

Statistical Methods

Migratory vs. Non-migratory Populations

Hybridization and Introgression

Genetic divergence among subspecies of cutthroat trout

Hybridization between cutthroat trout and O. mykiss

Studies of Regional Patterns of Genetic Variability

New Genetic Data

Sampling of hybrids

Uneven geographical sampling

Genetic outliers

Regional patterns of genetic variability

Genetic Information Summary

Artificial Propagation

Scale of Hatchery Production

Introduction of Nonnative Cutthroat Trout into Hatcheries

West Coast Artificial Propagation Activities

Alaska

British Columbia

Washington, Oregon, and California

1) Puget Sound

2) Olympic Peninsula

3) Southwestern Washington/Lower Columbia River

4) Willamette River

5) Oregon Coast

6) Southern Oregon/California Coasts

Discussion and Conclusions about ESU Determinations

Diversity of Life History

Paucity of Data

Genetic Outliers

Sampling artifacts

Founder effect/genetic drift

Hybridization

Artificial propagation

ESU Determinations

Life-history forms

Barriers to migration

ESU Descriptions

1) Puget Sound

2) Olympic Peninsula

3) Southwestern Washington/Columbia River

4) Upper Willamette River

5) Oregon Coast

6) Southern Oregon/California Coasts

Alternative ESU Scenarios

Single ESU corresponding to the subspecies O. c. clarki

Separate ESUs in major river basins

Umpqua River Coastal Cutthroat Trout

Relationship to State Conservation Management Units

Assessment of Extinction Risk

Approach

Previous Assessments

Washington

Oregon

Umpqua River sea-run cutthroat trout status review

California

Data Evaluations

Computed Statistics

Overall Evaluation of Risk and Uncertainty

Analysis of Biological Information

Species-wide Risk Factors Considered

Absolute numbers

Life-history diversity and risk

Historical abundance, habitat, and carrying capacity

Freshwater habitat conditions

Estuaries

Marine habitat

Trends in abundance

Factors causing variability in abundance

Threats to genetic integrity

Artificial propagation of coastal cutthroat trout

Hybridization between coastal cutthroat trout and O. mykiss

Harvest

Other risk factors

Biological Information by ESU

Puget Sound ESU

Olympic Peninsula ESU

Southwestern Washington/Columbia River ESU

Upper Willamette River ESU

Oregon Coast ESU

Southern Oregon/California Coasts ESU

Summary and Conclusions of Risk Assessments

Recent events considered

General risk considerations

Habitat

Hybridization

Ecological interactions

Paucity of information relating to risk

General conclusions

Summary of ESU-specific conclusions

Puget Sound ESU

Olympic Peninsula ESU

Southwestern Washington/Columbia River ESU

Upper Willamette River ESU

Oregon Coast ESU

Southern Oregon/California Coasts ESU

Citations

Appendix A: Hatchery Releases

Appendix B: The Risk Matrix Method

Appendix C: Additional Information

Glossary

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 life-history 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 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 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.

Figure ES-1. Proposed Evolutionarily Significant Unit (ESU) designations for coastal cutthroat trout. (View as PDF)

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 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.

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 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.

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.

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.

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 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

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 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 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.

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 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.

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