i
ii

Most NOAA Technical Memorandums NMFS-NWFSC

are available on-line at the Northwest Fisheries Science

Center web site (http://www.nwfsc.noaa.gov)

Copies are also available from:

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

phone orders (1-800-553-6847)

e-mail orders (orders@ntis.fedworld.gov)
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EXECUTIVE SUMMARY

In 1994, the Northwest Region of the National Marine Fisheries Service (NMFS)

received three petitions to list distinct populations of chum salmon (Oncorhynchus keta) from

Puget Sound and the Strait of Juan de Fuca as threatened or endangered species under the

Endangered Species Act (ESA). In response to these petitions and the more general concerns for

the status of Pacific salmon throughout the region, NMFS announced that it would initiate ESA

status reviews for all species of anadromous salmonids in the Pacific Northwest. These

comprehensive reviews will consider all populations in the states of Washington, Idaho, Oregon,

and California. This report summarizes the conclusions of the NMFS Biological Review Team

(BRT) for the ESA status review of chum salmon.

According to NMFS policy, populations of Pacific salmon will be considered “distinct”

(and hence “species” as defined by the ESA) if they represent evolutionarily significant units

(ESUs) of the biological species. Based on ecological, genetic, and life-history information

developed during this status review from across the species range, the BRT identified four ESUs

of chum salmon in the Pacific Northwest: 1) Puget Sound/Strait of Georgia ESU, which includes

all chum salmon populations from Puget Sound, the Strait of Georgia, and the Strait of Juan de

Fuca up to and including the Elwha River, with the exception of summer-run chum salmon from

Hood Canal and the Strait of Juan de Fuca; 2) Hood Canal summer-run ESU, which includes

summer-run populations from Hood Canal, Discovery Bay, and Sequim Bay on the Strait of Juan

de Fuca; 3) Pacific coast ESU, which includes all natural populations from the Pacific coasts of

California, Oregon, and Washington, west of the Elwha River on the Strait of Juan de Fuca; and

4) Columbia River ESU.

The BRT also evaluated patterns of abundance and extinction risk for chum salmon for

all ESUs. The team concluded that the Puget Sound/Strait of Georgia ESU is not presently at

risk of extinction, nor is it likely to become so in the foreseeable future. Current abundance is at

or near historic levels, with a total annual run size averaging over 1 million fish during the past 5

years. The majority of populations within this ESU have stable or increasing population trends,

and all populations with statistically significant trends are increasing.

The Puget Sound/Strait of Georgia ESU encompasses a great deal of diversity in chum

salmon life-history patterns, including summer, fall, and winter runs. Only two populations of

winter-run chum salmon were identified throughout the worldwide range of chum salmon, both

of which are present in this ESU and spawn within a few miles of each other in southern Puget

Sound. These winter-run populations are not large in size, and although they appear to be

healthy with stable escapements, they represent a life-history pattern which is important to

conserve. The BRT expressed concern that maintaining present population sizes of summer-run

chum salmon in the Puget Sound/Strait of Georgia ESU may depend on supplementation

programs. Concern was also expressed about effects on naturally spawning fish of high levels of

supplementation and enhancement in the southern part of Puget Sound and Hood Canal and the

high representation of non-native stocks in the ancestry of many hatchery stocks.
xiv

The BRT has concluded that the Hood Canal summer-run ESU is in danger of extinction.

In 1994, petitioners identified 12 streams in Hood Canal that recently supported spawning

populations of summer chum salmon. At the time of the petition, chum salmon runs in 5 of these

streams may already have been extinct, and those in 6 of the remaining 7 showed strong

downward trends. Similarly, summer chum salmon in Discovery and Sequim Bays were also at

low levels of abundance. A variety of threats to the continued existence of these populations was

identified, including degradation of spawning habitat, low river flows, possible competition

among hatchery and naturally-produced juvenile chum salmon in Hood Canal, and high levels of

incidental harvest in salmon fisheries in Hood Canal and the Strait of Juan de Fuca.

New information from state and federal agencies demonstrated substantial increases in

returning summer chum salmon to some streams in Hood Canal and the Strait of Juan de Fuca in

1995 and 1996. However, serious concerns for the health of this ESU remain. First, the

population increases in 1995 and 1996 were limited to streams on the west side of Hood Canal,

especially the Quilcene River system, while streams on the south and east sides of Hood Canal

continued to have few or no returning spawners. Second, a hatchery program initiated in 1992

was at least partially responsible for adult returns to the Quilcene River system. Third, the strong

returns to the west-side streams are the result of a single, strong year class, while declines in

most of these streams have been severe and have spanned two decades. Last, greatly reduced

incidental harvest rates in recent years probably contributed to the increased abundance of

summer chum salmon in this ESU. In Hood Canal, these reductions have been implemented

because of greatly reduced abundance of the target species, coho salmon (O. kisutch), rather than

as a specific conservation measure for summer chum salmon. If coho salmon in the area

rebound, and fishery management policies are not implemented to protect summer chum salmon,

these populations could again face high levels of incidental harvest.

The Pacific Coast ESU includes chum salmon from a large geographic area of

considerable diversity. In the southern portion of the coastal ESU, neither the historic nor the

present limit of spawning and distribution of chum salmon is known with certainty. Thus, it is

unclear whether the historic range has been reduced. On the Oregon coast, almost all current

production of chum salmon is natural, although abundance is low relative to historic levels.

Habitat degradation appears to be the primary cause of the depressed status of these Oregon

populations.

On the outer Washington coast, little information is available on the abundance of natural

populations, although annual adult escapements to Grays Harbor and Willapa Bay number in the

tens of thousands. The percentage of hatchery fish in these escapements is unknown.

Throughout the ESU there has been considerable hatchery enhancement and some transfer of fish

or eggs both within and outside of the ESU. However, hatchery production has been relatively

minor compared to natural production, and hatchery programs have used primarily local

populations. Therefore, although the BRT had several concerns regarding the paucity of

information, the majority conclusion is that the Pacific coast ESU is not presently at risk of

extinction nor likely to become so.

The Columbia River ESU historically supported commercial landings of hundreds of
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thousands of chum salmon, with annual landings of nearly half a million fish as recently as 1942.

However, beginning in the mid-1950s, commercial catches declined drastically and now rarely

exceed 2,000 per year (less than 50 fish per year have been caught since 1994). Historically,

chum salmon also spawned in many Columbia River tributaries. Currently, the Washington

Department of Fish and Wildlife (WDFW) recognizes and monitors only three natural

populations in the Basin, one in Grays River and two in small streams near Bonneville Dam. All

of these populations have been influenced by hatchery programs and fish transfers, including a

hatchery on the Chinook River near the mouth of the Columbia River that had a return of 3,000

fish in 1993. Present-day populations in the Columbia River represent only a small portion of

the historic chum salmon abundance and diversity. Substantial habitat loss in the Columbia

River, its tributaries, and estuary was presumably an important factor in the decline and also

represents a significant continuing risk for this ESU. Taking all of these factors into

consideration, the BRT unanimously agreed that this ESU is at some risk. About half the

members concluded that this ESU is at risk of extinction. The remaining members, citing

population trends in recent years that indicate the monitored populations may be stable (albeit

small), concluded that the ESU is not at substantial short-term risk of extinction but is likely to

become so in the foreseeable future.
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ACKNOWLEDGMENTS

This document represents the combined efforts of dozens of people who submitted

information on chum salmon directly to the National Marine Fisheries Service, attended

Biological and Technical Committee meetings, and answered seemingly endless questions from

the authors and BRT members in person and by telephone. The authors particularly wish to

acknowledge James Ames, Howard Fuss, Tim Tynan, and Stevan Phelps of the Washington

Department of Fish and Wildlife, Nick Lampsakis and Dr. Robert Springborn of the Point No

Point Treaty Council, and Carrie Cook, Tom Kane, and Dave Zajac of the U.S. Fish and Wildlife

Service for generously sharing newly emerging data. We also wish to thank those who reviewed

drafts of this and related documents.

Significant contributions to the compilation and analysis of data were made by Ted

Parker, Steve Lambert, and Tod McCoy, from the NMFS, Northwest Fisheries Science Center

(NWFSC). The Biological Review Team for chum salmon consisted of the following members

from the NWFSC: F. William Waknitz; Drs. Stewart Grant, Jeffrey Hard, Robert Iwamoto,

Orlay Johnson, Robert Kope, Conrad Mahnken, Michael Schiewe, Robin Waples, and John G.

Williams; and from the NMFS, Alaska Fisheries Science Center, Dr. John Helle.
xviii
1

INTRODUCTION

The U.S. Endangered Species Act (ESA) is intended to conserve threatened and

endangered species in their native habitats. Under the ESA, vertebrate populations are

considered “species” if they are “distinct.” On 14 March 1994, the National Marine Fisheries

Service (NMFS) was petitioned by the Professional Resources Organization-Salmon (PROSalmon) to list Washington’s Hood Canal, Discovery Bay, and Sequim Bay (Figs. 1-2) summerrun chum1,2 salmon (Oncorhynchus keta) as threatened or endangered species under the ESA

(PRO-Salmon 1994). A second petition, received 4 April 1994 from the “Save Allison Springs”

Citizens Committee (1994), requested listing of fall chum salmon found in the following

southern Puget Sound streams or bays: Allison Springs, McLane Creek, tributaries of McLane

Creek (Swift Creek and Beatty Creek), Perry Creek, and the southern section of Mud Bay/Eld

Inlet (Figs. 1-2). A third petition, received by NMFS on 20 May 1994, was submitted by Trout

Unlimited (1994). This petition requested listing for summer chum salmon that spawn in 12

tributaries of Hood Canal (Figs. 1-3).

In response to these petitions and to the more general concerns about the status of Pacific

salmon throughout the region, NMFS (1994) announced that it would initiate ESA status reviews

for all species of anadromous salmonids in the Pacific Northwest. These comprehensive reviews

will consider all populations in the states of Washington, Idaho, Oregon, and California. This

proactive approach should facilitate more timely, consistent, and comprehensive evaluation of

the ESA status of Pacific salmonids than would be possible in a series of reviews of individual

populations.

Scope and Intent of the Present Document

This document reports results of the comprehensive ESA status review of chum salmon

from Washington, Oregon, and California (chum salmon do not occur in Idaho). To provide a

context for evaluating U.S. populations of chum salmon, biological and ecological information

for chum salmon in British Columbia is also considered. This review thus encompasses, but is

not restricted to, the populations identified in petitions for chum salmon received by NMFS in

1994.

1

 Seasonal designations such as “summer-run,” “summer chum salmon,” or “summers” are used

synonymously in this report.

2

 The terms “run,” “stock,” and populations” are used synonymously in this report and generally refer to a

group of salmon that spawn at a particular place and time. These terms are problematical because they

have been used in a variety of ways by salmon biologists and managers throughout the Pacific Northwest.

For examples, WDFW (1997:A-4) uses the same definition for “stock” and “population” but defines

“run” as “the sum of stocks of a single salmonid species which migrates to a particular region, river, or

stream of origin at a particular time” (p. A-4).
2
3
4
5

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 salmon 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 presented at public meetings held in Seattle in December

1994 and February 1995 was also considered. In addition, the BRT reviewed 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 separate sections of this report. 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 (NMFS 1996).

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 sea-run cutthroat

trout (O. clarki clarki) and steelhead (O. mykiss) (NMFS 1991). A more detailed discussion of

this topic appeared in the NMFS “Definition of Species” paper (Waples 1991). The NMFS

policy stipulates that a salmon population (or group of populations) will be considered “distinct”

for purposes of the ESA if it represents an evolutionarily significant unit (ESU) of the biological

species. An ESU is defined as a population that 1) is substantially reproductively isolated from

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”—that is, something

received from the past and carried forward into the future. Specifically, the evolutionary legacy

of a species is the genetic variability that is a product of past evolutionary events and that
6

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), the 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 include natural rates

of straying and recolonization, evaluations of the efficacy of natural barriers, and measurements

of genetic differences among 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 second criterion is: If the population became

extinct, would this represent a significant loss to the ecological/genetic diversity of the species?

Again, a variety of types of information should be considered. Phenotypic and life-history traits

such as size, fecundity, migration patterns, and age and time of spawning may reflect local

adaptations of evolutionary importance, but interpretation of these traits is complicated by their

sensitivity to environmental conditions. Data from protein electrophoresis or DNA 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.

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 et al. 1991). 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 and migration and spawn timing. Second, artificial

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

or endangerment. (These risks are discussed below in “Assessment of Extinction Risk,” p. 144.)

In contrast to most other types of risk for salmon populations, those arising from artificial
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propagation are often not reflected in traditional indices of population abundance. For example,

to the extent that habitat degradation, overharvest, or hydropower development have contributed

to a population’s decline, these factors will already be reflected in population abundance data and

accounted for in the risk analysis. The same is not true of artificial propagation. Hatchery

production may mask declines in natural populations that will be missed if only raw population

abundance data are considered. Therefore, a true assessment of the viability of natural

populations cannot be attained without information about the contribution of naturally spawning

hatchery fish. Furthermore, even if such data are available, they will not in themselves provide

direct information about possibly deleterious effects of fish culture. Such an evaluation requires

consideration of the genetic and demographic risks of artificial propagation for natural

populations. The sections on artificial propagation in this report are intended to address these

concerns.

Finally, if any natural populations are listed under the ESA, then it will be necessary to

determine the ESA status of all associated hatchery populations. This latter determination would

be made following a proposed listing and is not considered 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 considers a variety

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

1) absolute numbers of fish and their spatial and temporal distribution; 2) current abundance

relative 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 proposed or in place. In this

review, we do not evaluate likely or possible effects of conservation measures. Therefore, we do

not make recommendations as to whether identified ESUs should be listed as threatened or

endangered species, because that determination requires evaluation of factors not considered by

us. Rather, we have drawn scientific conclusions about the risk of extinction faced by identified

ESUs under the assumption that present conditions will continue (recognizing, of course, that

natural demographic and environmental variability is an inherent feature of “present
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conditions”). Conservation measures will be taken into account by the NMFS Northwest

Regional Offices in making listing recommendations.

Summary of Petitioners’ Arguments to List Chum Salmon

In 1994, NMFS received three petitions to list specific groups of chum salmon in

Washington State under the ESA. The petitioners were PRO-Salmon, “Save Allison Springs”

Citizens Committee, and Trout Unlimited. Below is a summary of their petitions.

PRO-Salmon Petition

The petition by PRO-Salmon (1994) requested protection of Hood Canal and Strait of

Juan de Fuca summer chum salmon populations identified in the Washington State Salmon and

Steelhead Stock Inventory (SASSI) reports (WDF et al. 1993) of the Washington Department of

Fish and Wildlife (WDFW) and Western Washington Treaty Indian Tribes (WWTIT) (Figs. 1-2).

The SASSI reports group all summer chum salmon spawning in Hood Canal, except those in the

Union River, as one stock designated as Hood Canal summer chum salmon. The status of the

Hood Canal summer chum salmon stock is listed in the SASSI reports as “critical” and the Union

River stock as “healthy.” The origin of both stocks is listed as native and the production type as

wild.

PRO-Salmon petitioners argue that these SASSI stocks meet the two criteria established

by NMFS to define a “species” of Pacific salmon under the ESA: reproductive isolation and

evolutionary significance. The petitioners claim that genetic data support distinctiveness from

other fall/summer chum salmon populations, that the petitioned stocks are geographically

isolated from other summer chum salmon, and that migrational and spawning timing differences

isolate them from other fall chum salmon in Hood Canal.

With respect to the “evolutionary significance” criterion for species status under the ESA,

the PRO-Salmon petitioners point out that summer chum salmon were historically present in

Hood Canal and may have represented a larger portion of the overall chum salmon run to this

basin than the fall-run type. They also point out that summer chum salmon in Washington are

unique to the Puget Sound drainage area, inclusive of streams draining to the eastern Strait of

Juan de Fuca, and that they were never present in Washington coastal drainages, the Columbia

River Basin, or in Oregon or California. The petitioners further assert that summer chum salmon

are unique among chum salmon run types in that they are found only in smaller, independent (not

part of a large river basin) drainages of non-glacial origin and were absent historically in larger

and/or glacial Puget Sound river systems. They also state that summer chum salmon, to a much

greater extent than fall chum salmon, spawn within a short distance of tidal influence and do not

require long estuarine transitions.

The petitioners claim that Hood Canal summer chum salmon meet the threshold criteria

for protection under the ESA because, as detailed in the SASSI report, escapement goals for
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Hood Canal summer chum salmon have not been met since 1968, and abundance has declined

significantly through the 1980s.

The petitioners suggest that habitat loss (Lichatowich 1993) and overfishing are the major

causes of the stock decline. They discuss in detail habitat losses due to channel excavations,

dewatering, channelization, flood control, major water diversions, poor forestry practices, and

bulkheading of nearshore marine habitats. The petitioners also state that not only has overfishing

been a major cause of decline, but until recently no attempt has been made by WDFW or

WWTIT to protect summer chum salmon. They conclude that summer chum salmon are

severely overfished as incidental catch in mixed-fishery harvests of coho, sockeye, chinook (O.

tshawytscha), and pink salmon (O. gorbuscha).

The petitioners maintain that, as with Hood Canal summer chum salmon, summer chum

salmon populations in the Strait of Juan de Fuca, Discovery Bay (Snow and Salmon Creeks), and

Sequim Bay (Jimmycomelately Creek) are reproductively isolated by geographic distance from

other summer chum salmon and have a different run timing from fall chum salmon found in the

same region. The petitioners also claim that genetic studies published in the SASSI report (WDF

et al. 1993) show these populations to be genetically different from other fall and summer chum

salmon populations analyzed.

The petitioners claim that chum salmon in Discovery and Sequim Bays meet the criterion

of “evolutionary significance” in the same manner as do Hood Canal summer chum salmon. The

petitioners report that the abundance of summer chum salmon in Discovery and Sequim Bays has

declined severely in recent years. Discovery Bay summer chum salmon escapement levels as

reported in SASSI for the years 1968 to 1986 ranged from 3,700 to 4,500 fish per year. From

1989 to 1991, Discovery Bay escapements were less than 300 fish per year.

“Save Allison Springs” Citizens Committee Petition

The petition by the “Save Allison Springs” Citizens Committee requests ESA protection

for southern Puget Sound fall chum salmon found in Allison Springs, McLane Creek, tributaries

of McLane Creek (Swift Creek and Beatty Creek), Perry Creek, and the southern section of Mud

Bay/Eld Inlet (Figs. 1-2). The petitioners present no specific information on reproductive

isolation or evolutionary legacy, but contend that the fish are a conglomerate of a number of

chum salmon populations in the area. They argue that these populations are genetically isolated

from other chum salmon due to the ability of salmon to home and adapt to unique environments.

The petition states that although surrounding chum salmon populations are abundant and

healthy, escapement of chum salmon to Allison Springs has been depleted due to damming and

is presently only about 200 fish per year. Further, the petitioners argue that Allison Springs

chum salmon are in imminent danger of extinction due to proposed land development, poor

environmental regulations in the area, and a lack of understanding or response from local and

state governments.
10

Trout Unlimited Petition

The petition by Trout Unlimited requests ESA protection for summer chum salmon

spawning in 12 tributaries to Hood Canal, Washington (Figs. 1-3). The petitioners contend that

these fish are reproductively isolated from other chum salmon populations in Washington, based

on their life history and on genetic studies conducted by WDFW (Phelps et al. 1993, WDF et al.

1993). Life-history differences between summer and fall chum salmon in Hood Canal cited by

the petitioners are based primarily on timing: time of return to natal streams, time of spawning,

time of juvenile emergence from the gravel, and time of outmigration to Hood Canal and Puget

Sound. The petitioners present data from the studies of Groot and Margolis (1991), Lichatowich

(1993), and the WDF Chum Stock Assessment Unit (WDF et al. 1993) to support these timing

differences. Based on these documents, they report that summer chum salmon in Hood Canal

enter freshwater between mid-August and mid-October, with migration peaking in midSeptember. Fall chum salmon enter the Canal from mid-November to mid-January, with peak

entry about 20 November. Spawning is coincident with river entry. Summer-run fish emerge and

outmigrate from mid-March through early April, but juvenile fall-run chum salmon do not

emerge and outmigrate until mid-April, continuing through mid-May. Based upon this timing,

the petitioners state that summer chum salmon outmigrate before naturally spawning fall chum

salmon (Trout Unlimited 1994).

The petitioners also assert that distinct genetic differences exist between Hood Canal

summer and fall chum salmon. This assertion is based on data developed by WDFW biologists

(Phelps et al. 1994), who reported a Rogers genetic distance of 0.11 between sampled Hood

Canal summer chum salmon and other chum salmon in Washington. The petitioners further

contend, based on this and other data developed by WDFW (Phelps et al. 1994, Phelps3

), that

distinct genetic differences appear among summer chum salmon in each sampled river system in

Hood Canal, except in Quilcene Bay and the Quilcene National Hatchery (Trout Unlimited

1994).

The petitioners believe summer chum salmon in Hood Canal meet the NMFS second

criterion for ESU status (evolutionary and ecological diversity) because the “various runs of

summer chum salmon are part of a unique race of chum salmon that has adapted to a specific

niche in Hood Canal” (Trout Unlimited 1994).

The petitioners present data from WDF et al. (1993), Lichatowich (1993), and their own

observations that address questions about declining abundance of summer chum salmon in Hood

Canal. Based on this information, the petitioners claim that several individual runs of chum

salmon from the Canal have disappeared and that others are in critical condition. As an example,

they present the following general observations from WDFW and WWTIT (WDF et al. 1993).

Escapement numbers were first reported for summer chum salmon beginning in the 1960s, and

3 S. Phelps, Washington Department of Fish and Wildlife, P.O. Box 43151, Olympia, Washington 98504.

Pers. commun., December 15, 1994.
11

these numbers peaked at 43,000 in 1968. From 1968 to 1978, escapement ranged from 10,000 to

43,000 fish. However, since 1978, escapement has not exceeded 5,500 fish per year, with a low

of only 500 returning fish (for the entire Hood Canal Basin) in 1990. Some rivers and

riverbasins, including Anderson and Big Beef Creeks, no longer have any returning summer

chum salmon, and escapements of summer chum salmon to all Hood Canal tributaries, except

those to the Union River, are severely depressed.

Data from two specific river systems are reported by petitioners from Trout Unlimited to

support their general assertion that the abundance of the summer-run populations is critically

depressed. In spawning surveys of the Big Quilcene River (northwestern side of Hood Canal),

escapements were greater than 1,800 fish/mile in 1968 and 1,050 fish/mile in 1976. However,

recent spawning surveys show that the run is “near extinction” (Trout Unlimited 1994), with only

25 fish/mile reported in 1991. Similar trends for the Little Quilcene River (escapements

numbered 1,150 fish/mile in 1968 and 1,250 fish/mile in 1976, but only 100 fish/mile in 1991)

were also used by the petitioners to support the claim that these fish are at critically low levels of

abundance and warrant federal protection under the ESA.

The authors of this petition address what they believe are the causes for the decline of

summer chum salmon in Hood Canal: overharvest, inadequate regulatory efforts, habitat

degradation, predation, and other factors. Finally, the petitioners consider the recovery efforts

now being implemented to be inadequate because there is no guarantee that ongoing recovery

efforts will be continued, and the state-mandated recovery plan is not binding for Treaty Indian

Tribes.
12

INFORMATION RELATING TO THE SPECIES QUESTION

In this section, we summarize biological and environmental information relevant to

determining the nature and extent of chum salmon ESUs in the U.S. Pacific Northwest. The

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

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

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

information, they do not necessarily conform to state or national boundaries, such as the

U.S./Canada border.

Biology of Chum Salmon

Chum salmon belong to the family Salmonidae and are one of eight species of Pacific

salmonids in the genus Oncorhynchus. Chum salmon are semelparous, spawn primarily in

freshwater, and apparently exhibit obligatory anadromy, as there are no recorded landlocked or

naturalized freshwater populations (Randall et al. 1987). The species is best known for the

enormous canine-like fangs and striking body color of spawning males (a calico pattern, with the

anterior two-thirds of the flank marked by a bold, jagged, reddish line and the posterior third by a

jagged black line). Females are less flamboyantly colored and lack the extreme dentition of the

males.

The species has the widest natural geographic and spawning distribution of any Pacific

salmonid, primarily because its range extends farther along the shores of the Arctic Ocean than

other salmonids (Groot and Margolis 1991) (Fig. 4). Chum salmon have been documented to

spawn from Korea and the Japanese island of Honshu, east, around the rim of the North Pacific

Ocean, to Monterey Bay in southern California. The species’ range in the Arctic Ocean extends

from the Laptev Sea in the Russian Federation to the Mackenzie River in Canada (Fig. 4)

(Bakkala 1970, Fredin et al. 1977). Chum salmon may historically have been the most abundant

of all salmonids: Neave (1961) estimated that prior to the 1940s, chum salmon contributed

almost 50% of the total biomass of all salmonids in the Pacific Ocean. Chum salmon also grow

to be among the largest of Pacific salmon, second only to chinook salmon in adult size, with

individuals reported up to 108.9 cm in length and 20.8 kg in weight (Pacific Fisherman 1928)4

.

Average size for the species is around 3.6 to 6.8 kg (Salo 1991).

In Asia, chum salmon are the most abundant and commercially valuable salmon. In

Japan, mean annual harvest since 1952 has been around 25 million fish, compared to 6.9 million

4

 The fish was caught in a Northwestern Fisheries Company trap on 12 July 1928 near the Quadra

cannery in the Ketchikan district of southeast Alaska. It was photographed, weighed, and measured by

the general manager of the company, P.H. McCue. The fish was a bright male in prime condition and

scale data indicated it was 6 years old. The news article in Pacific Fisherman (1928) indicated that a

number of similar-sized fish were caught by the trappers that summer.
13
14

in the United States and 2.4 million in Canada (Bakkala 1970, Salo 1991). But even in North

America, more chum salmon by weight are landed each year than any other salmon species

(INPFC 1993). Major chum salmon fisheries in North America are located in southeast Alaska

and British Columbia, but the commercial salmon catch north of Bristol Bay, Alaska is also

primarily chum salmon (Hale 1981). While the low fat content of chum salmon makes it the

least desirable of the Pacific salmon for canning, it is preferred for smoke curing among many

native peoples. Chum salmon are primarily taken by gill net and purse seine and are usually sold

fresh or frozen.

Chum salmon spend more of their life history in marine waters than other Pacific

salmonids. Chum salmon, like pink salmon, usually spawn in coastal areas, and juveniles

outmigrate to seawater almost immediately after emerging from the gravel that covers their redds

(Salo 1991). This ocean-type migratory behavior contrasts with the stream-type behavior of

some other species in the genus Oncorhynchus (e.g., coastal cutthroat trout, steelhead, coho

salmon, and most types of chinook and sockeye salmon), which usually migrate to sea at a larger

size, after months or years of freshwater rearing. This means that survival and growth in juvenile

chum salmon depend less on freshwater conditions (unlike stream-type salmonids which depend

heavily on freshwater habitats) than on favorable estuarine conditions. Another behavioral

difference between chum salmon and species that rear extensively in freshwater is that chum

salmon form schools, presumably to reduce predation (Pitcher 1986), especially if their

movements are synchronized to swamp predators (Miller and Brannon 1982).

The family Salmonidae is generally thought to have had a freshwater origin (Tchernavin

1939; Hoar 1958, 1976; but see Thorpe 1982, 1987 for the opposing view), with chum and pink

salmon considered the most derivative of the Pacific salmonid species, both because of their

ocean-type life histories (McCormick and Saunders 1987, Salo 1991) and because of their

positions in molecular genetic phylogenies (Utter et al. 1973, Thomas et al. 1986, Shedlock et al.

1992). Genetic studies also suggest that Pacific salmon (coho, chinook, sockeye, masou, pink,

and chum salmon) and Pacific trouts (rainbow/steelhead, and cutthroat trout) are monophyletic.

Analysis of mitochondrial DNA by Shedlock et al. (1992) indicates that extant Pacific salmon

may have arisen 5 or 6 million years ago, and that pink and chum salmon diverged from each

other 4.3 to 3.5 million years ago.

Chum salmon were first scientifically described from the Kamchatka River by Johann

Julius Walbaum in 1792. The species’ scientific name “keta” means “the fish” in the language of

the Nanai people, who live in the borderlands of China and the Russian Federation along the

Amur River. The species is perhaps best known for its unique breeding coloration and spawning

morphology, as reflected in its two most widely used common names: “chum” and “dog”

salmon. “Chum salmon” is the common name accepted by the American Fisheries Society, most

likely derived from a word in the language of the Chinook peoples of the Columbia River area,

cam (also translated as sum or tzum), which means calico (Lampsakis5

). The name refers to the

5 N. Lampsakis, Fisheries Office, Point No Point Treaty Council, 7999 N.E. Salish Lane, Kingston,

Washington 98346. Pers.commun., September 1995.
15

breeding coloration of the species and first came into general use around 1900 as a marketing

name for the canned product (Tabbert 1991).

Early scientific and commercial records in Washington and Oregon often reported chum

salmon as “kings” or “yellow kings.” Chinook salmon are also called “kings” and this confusion

in names makes historical estimates of abundance difficult for both species. In the Yukon River,

fall-run chum salmon are called “silvers” or “silver salmon” because of their bright appearance

(Tabbert 1991). The species is often sold in the United States as “Ocean” or “Silver Brite”

salmon.

A second name, less marketable but more popular among native peoples in Alaska, is

“dog salmon.”6 Tabbert (1991) suggested two possible origins for this name. It may have

derived from the extremely large head, elongated upper jaw, and prominent, canine-like teeth on

mature males, or from the practice of drying large quantities of this species as food for dogsled

teams. Other common names include “dogfish” or just “dog,” although these names usually

refer only to the dried fish preserved for feeding dogs.

In Asia, where chum salmon have historically been the most abundant salmonid, many

common names reflect the polytypic nature of the species (see “Life-History and Ecological

Information,” p. 34). For example, in the Russia Federation the standard common name for

chum salmon is “keta,” but summer-run fish are called “letnyaya keta” and fall-run fish

“osennyaya keta” (Berg 1934). They are also called “Sil’cha” in the Amur Region and “Haiko”

in Kamchatka. In Korea, “yon-o in” or “nyon-o” are common names for the species. In Japan,

“skae” is the standard common name, but Hikita (1962) lists more than nine vernacular names

from different regions of the country.

In Washington, chum salmon are managed jointly by the WDFW (formerly the

Washington Department of Fisheries (WDF) and the Washington Department of Wildlife

(WDW)) and the WWTIT. A variety of seasonal runs are recognized, including summer, fall,

and winter populations. Fall-run fish predominate, but summer runs are found in Hood Canal,

the Strait of Juan de Fuca, and in southern Puget Sound (WDF et al. 1993). Only two rivers have

fish returning so late in the season that the fish are designated as winter-run fish, and both of

these are in southern Puget Sound.

Environmental Information

Historically, chum salmon were distributed throughout the coastal regions of western

Canada and the United States, as far south as Monterey Bay, California. Presently, major

spawning populations are found only as far south as Tillamook Bay on the northern Oregon coast

6 Michael Morgan in an article published in Alaska magazine in 1975 entitled “The Middle Yukon, and

Its Troublesome Tributary, Tanana” quoted a fish buyer who paid $1.25 per chum salmon as saying:

“When I buy ‘em, I call ‘em dogs. When I sell ‘em, I call ‘em chums.”
16

(Fig. 5). Climate and geological features vary markedly in this region, with diverse patterns of

vegetation, weather, soils, and water quality. This section summarizes environmental and

biological information that may be relevant to determinations of the nature and extent of ESUs

for chum salmon in this region.

Physical Features

Physiography and geology

Chum salmon inhabit areas in Oregon and Washington (Fig. 5) that are represented by

two major physiographic regions (McKee 1972). The first is the Coast Range Province, which in

the United States extends from the Strait of Juan de Fuca south to the Klamath Mountains in

northern California and from the Pacific Ocean east to Puget Sound. The second is the PugetWillamette Lowland Province, which covers Puget Sound and the Willamette River Valley,

Oregon. In southern British Columbia, chum salmon occur in three physiographic provinces:

the Coast Mountains on the Mainland Province, the Coastal Trough (which covers the area

surrounding Georgia and Johnstone Straits), and the Outer Mountains of Vancouver Island

(McKee 1972). Although these regions appear quite diverse today, they are unified by their

history of volcanic and glacial activity.

All of the physiographic regions have experienced volcanic eruptions, and volcanic rocks

are a common feature in all regions. The Cascade Range is volcanic in origin and composed of a

wide spectrum of igneous, metamorphic, and sedimentary rock types. The coastal mountains of

both the Olympic Peninsula and British Columbia are composed of volcanic and nonvolcanic

rock, with a foundation of marine basalt and marine sedimentary rocks. The massive foundation

of marine basaltic flow on the Olympic Peninsula is unique in the region (McKee 1972).

Glaciers spread south from British Columbia at least four times during the Pleistocene

Epoch, covering much of the Puget Lowland and pushing high against the flanks of the Olympic

and the Cascade Ranges (McKee 1972). The effects of glaciation on the Puget Lowland were so

great that a preglacial reconstruction of the topography is almost impossible (McKee 1972).

Today, the area is covered by a thick layer of glacial sediment. Even regions not directly

covered by the glaciers were structurally changed by the effects of ice dams, flooding, variation

in sea levels, and climate changes (McKee 1972).

River hydrology

The timing of seasonal changes in river flow and water temperatures is perhaps the most

critical factor in structuring the freshwater life history of anadromous salmonids. In general, the

coastal region of the Pacific Northwest, including northern California, has a mild climate with

warm, relatively dry summers and cool, wet winters. On average, it is cooler and wetter in the

northern part of the region than in the southern part. There is also a seasonal north-to-south
17
18

gradation in the timing of increases in winter precipitation and stream flows. In northern British

Columbia, stream flows are lowest in July and August, with rising flows correlated with the

onset of fall/winter rains in early September. Farther south on the Olympic Peninsula, minimal

stream flows occur in August or September, with rising stream flows and decreasing

temperatures beginning in early to mid-October (Table 1). Variation in run timing of chum

salmon into and within individual river basins can often be correlated with these seasonal

changes in stream flow and water temperature (Salo 1991, WDF et al. 1993, Hiss7).

Eight distinct regions of differing precipitation, temperature, and hydrology can be

identified within the range of chum salmon in the Pacific Northwest (Franklin and Dyrness

1973). One of these regions, the eastern Olympic Peninsula, contains populations of chum

salmon that are the subjects of two of the ESA chum salmon petitions received by NMFS in

1994; therefore, this region is more extensively discussed than other regions.

California and southern Oregon_It is difficult to determine whether spawning populations of

chum salmon have been historically present in California (English et al. 1995) (Fig. 5).

Presently, California Fish and Game biologists claim there are no viable spawning runs of the

species in their state (English et al. 1995; see “Assessment of Extinction Risk,” p. 144), although

spawned-out chum salmon carcasses (Moyle 1976) and juvenile chum salmon have been

reported in California (Moyle 1976, English et al. 1995). In Oregon, chum salmon were reported

to be widely distributed throughout coastal regions (Snyder 1908), with spawning populations at

least as far south as the Coquille River Basin (Kostow 1995). Presently, chum salmon

populations in Oregon are small and occur only sporadically south of the Tillamook Bay region

(Nickelson et al. 1992, Cooney and Jacobs 1994, Kostow 1995). Nehlsen et al. (1991) reported

that relic chum salmon populations may occur as far south as the Elk and Sixes Rivers.

Rivers in California (from Redwood Creek southward) that may support chum salmon

drain the 500-1,000-meter-high Coast Range, an area underlain by easily eroded sedimentary

rocks of the Franciscan Formation (California State Lands Commission 1993). To the north, the

Rogue and Klamath River Basins cut through the Coast Range to drain the Cascade Mountains

as well. Maximal elevations in this area are typically 1,000-2,000 m. Rivers from the Rogue

River south to the Mattole River exhibit peak flow in late January or early February, whereas

rivers farther south have peak flows in late February. Duration of peak flows in rivers south of

the Mattole is much shorter than in those farther north, although both areas experience relatively

low flows during the summer and early fall.

Northern Oregon coast_Although chum salmon have probably never been as abundant south of

the Columbia River as farther north, populations have been large enough for commercial and

recreational exploitation have occurred in the Tillamook Bay region south to the Nestucca River

(Cleaver 1951; see “Assessment of Extinction Risk,” p. 144) (Figs. 5-6). The species has been

documented to occur as far south as Monterey, California (Fig. 5).

7

 J. Hiss, U.S. Fish and Wildlife Service, Western Washington Fisheries Assistance Office, 2625

Parkmont Lane, Building A, Olympia, Washington 98502. Pers. commun., October 1994.
19
20

All coastal Oregon rivers north of Cape Blanco—with the exception of the Umpqua

River—drain only the west side of the Coast Range (Fig. 6). The Oregon Coast Range is

relatively low, with peaks at 500-1,000 m elevation, in contrast to most Cascade peaks which are

1,000-2,000 m high. Seasonal river flows in this region follow a fairly consistent pattern, with a

single peak in December or January and relatively low flow in summer and fall. The Oregon

coast has relatively high rainfall (120-240 cm/year) compared to areas east of the Coast Range

(60-120 cm/year) or farther south (60-200 cm/year), but receives less rainfall than the extremely

wet Olympic Peninsula farther north (>240 cm/year). Both air and stream temperatures are fairly

consistent along the Oregon coast, with little latitudinal change. Minimal average winter air and

stream temperatures are typically around 4oC and 4-8oC, respectively, whereas maximal average

summer air and stream temperatures are typically around 21o

C and 15-21oC, respectively.

Because of the relatively low elevation, snowfall in the Coast Range is low, averaging 30-60 cm

annually, while the higher Cascade Mountains receive 250-760 cm annually. On average, the

Oregon coast receives more sunshine (1,800-2,200 hours/year) than the wetter Olympic

Peninsula (<1,800 hours/year), but less than northern California and southern Oregon

(2,000-2,200 hours/year).

Columbia River Basin_Small spawning populations of chum salmon are regularly found as far

south as the lower Columbia River and Tillamook Bay (Figs. 5-6). The hydrology and flow

patterns of rivers draining into the lower Columbia River are similar to those of coastal rivers

immediately north and south of the Columbia River, with a single peak in December or January

and relatively low flows in summer and fall. Columbia River tributaries, such as the Willamette

or Cowlitz Rivers draining the Cascade Mountains, have proportionally higher flows in late

summer and early fall than rivers draining the coastal range (e.g., Nehalem River and Tillamook

Bay tributaries), reflecting the greater contribution of snow melt in these Cascade Mountain

systems.

Southwest Washington_Rivers in southwest Washington drain the Willapa Hills, an area

characterized by relatively low elevations (500-1,000 m), with moderate amounts of precipitation

(200-240 cm/year) (Fig. 5). Rivers draining the Willapa Hills are relatively short and flow either

south into the lower Columbia River or west into the Pacific Ocean through Willapa Bay and

Grays Harbor (Table 1). These rivers display relatively low flows during late summer and early

fall, increased river flows and decreased water temperatures beginning in early October, and a

single flow peak in December or January. These temperature and water regimes are similar

regardless of whether the rivers drain into the lower Columbia River or into other coastal bays.

There are also similarities between the Columbia River estuary, Willapa Bay, and Grays

Harbor: All three are characterized by extensive intertidal mud and sand flats that are not found

in estuaries to the north or south (Fig. 5). Part of this similarity results from the shared geology

of the area: The Chehalis River Basin was the northernmost area that remained ice-free during

the most recent glaciation (McPhail and Lindsay 1986), and the Chehalis and Columbia Rivers

periodically had much higher flows during that time period, which greatly enlarged their

respective valleys (Alt and Hyndman 1984, Allen et al. 1986). The Columbia River estuary,
21
22

Willapa Bay, and Grays Harbor were all inundated by seawater following the last ice age.

Sediments carried by the Columbia River have slowly been filling the lower Columbia River and

been transported northward along the coast to form Long Beach, which in turn has formed

Willapa Bay, in addition to creating extensive sand beaches and dunes north and south of Grays

Harbor (Alt and Hyndman 1984, Allen et al. 1986, Landry et al. 1989).

Life-history characteristics of chum salmon appear to follow the water flow and

temperature regimes of these southwest Washington rivers. Fish enter freshwater spawning

streams from early October to mid-November, with a peak return in early November. Spawning

peaks in mid- to late November and is usually completed by early December (WDF et al. 1993;

also see “Life-History and Ecological Information,” p. 34).

Western Olympic Peninsula_Farther north, the western coast of the Olympic Peninsula

gradually becomes more rocky and steeply graded. Rivers along this coast may drain into Grays

Harbor (e.g., Humptulips and Chehalis Rivers) or directly into the ocean (e.g., Hoh and

Quillayute Rivers) (Table 1) (Fig. 5). While the Grays Harbor estuary is one of the largest on the

west coast of North America, most western Olympic Peninsula rivers have small estuaries, and

some abruptly enter the open sea.

There are two outstanding climatic characteristics of the Olympic Peninsula: In the

winter it is one of the wettest places on earth (160-380 cm precipitation/year, with snowfall over

150 cm/year at higher elevations), but in the summer it is dry (Mathews 1988). The increased

winter precipitation on the Olympic Peninsula is primarily caused by the high elevation of the

Olympic Mountains (1,000-2,000 m) and the prevalence of water-laden air moving eastward off

the Pacific Ocean (Franklin and Dyrness 1973, Mathews 1988). The summer drought results

from a combination of the jet stream moving north in the summer, taking its rainy frontal

systems with it, and a subtropical North Pacific high stabilizing off the Northwest coast. This

high-pressure area produces an onshore airflow that is warmer than the sea surface (12.8oC, or

55oF), creating vast ocean fog banks, but little rain.

Tropical areas typically have well-defined wet and dry seasons, whereas temperate

regions usually have precipitation year-round. The climate of the Olympic Peninsula is mid-way

between California’s Mediterranean climate (dry summers and warm temperatures) and

Southeast Alaska’s cold marine climate (heavy year-round rain, slightly reduced in summer, and

cool temperatures year-round). Similar wet-dry temperate regions include southern Chile,

western Scotland, northern Honshu, and coastal Norway. Precipitation in winter in these areas is

around 1.5 times greater than it is in summer. On the Olympic Peninsula, precipitation is

between 6 and 20 times greater in December than in June (Mathews 1988). Because of this

winter precipitation, an extremely heavy snowpack at high elevations persists longer into the

summer than in other mountains with equally mild or somewhat colder climates, such as the U.S.

Rocky Mountains (Mathews 1988).

As a consequence of these climatic conditions, rivers originating in the Olympic

Mountains derive much of their water from snowmelt and have relatively high flows even in
23

summer. Most have a second flow peak during July or August. Rivers and streams that do not

originate in the mountains have low or no summer flows. Because of the geological history of

the region, the coastal plain of the Olympic Peninsula is narrow, with the Olympic Mountains

thrusting upwards within a few kilometers of the ocean. Rivers in the region are typically swift,

steeply graded, rocky, and short; this is true whether they drain directly into the ocean, such as

the Copalis (34 km), Queets (83 km), or Ozette (21.4 km) Rivers, or whether they drain into

Grays Harbor, such as the Humptulips River (98 km long). The largest river on the north coast is

the Quillayute River, which, although only 113.5 km in length, drains four major basins with an

area of over 1,012 km2 (Storm et al. 1990).

Chum salmon from rivers draining the western Olympic Peninsula display an early- and

late-fall return pattern coincident with increasing fall/winter river flows. In general, river entry

occurs from September through December with spawning from October (late October in Grays

Harbor) to January. Spawning tends to peak in mid-November. Chum salmon on the north coast

are most abundant in Grays Harbor, perhaps because of the large estuary available for rearing

and good spawning habitat of low-gradient streams.

Eastern Olympic Peninsula and Hood Canal_This region, the focus of two of the three

petitions received by NMFS for chum salmon, lies on the eastern and northern Olympic

Peninsula and has a different physical and climatic character from the western Olympia

Peninsula (Figs. 1 and 6). It also has far more abundant and diverse runs of chum salmon than

the north coast. The major geographic features of the region are Hood Canal and the eastern

escarpment of the Olympic Mountains. Hood Canal is a 100-km-long, fjord-like, blind channel

that extends to the west of Puget Sound (Figs. 1-2). Beginning at the northern tip of the Kitsap

Peninsula between Tala Point and Foulweather Bluff (near Hansville, Washington), the Canal

runs southward along the eastern side of the Olympic Mountains, takes a sharp eastward turn at

the hook-like Great Bend, and ends only a few kilometers from southern Puget Sound (Fig 1).

The western shore is on the Olympic Peninsula, with river headwaters high in the Olympic

Mountains. The eastern shore is on the Kitsap Peninsula, with rivers much gentler and without

headwater snowpack.

As with other regions of the Peninsula, the climate of Hood Canal is strongly influenced

by the Olympic Mountains. Headwater areas of rivers draining western Hood Canal receive

annual precipitation averaging 200-250 cm per year, and precipitation in the southern Canal

averages between 150 and 200 cm annually. In the northern part of the Canal, the Olympic

Mountains block major North Pacific storm systems from reaching Hood Canal, and this rain

shadow reduces annual precipitation to about 75 cm annually in the Quilcene River Basin

(Yoshinaka and Ellifrit 1974).

The primary force that has structured the unique hydrological characteristics of Hood

Canal and the Strait of Juan de Fuca regions was the same general north-south uplift that formed

the Olympic and Cascade Mountains. This uplift was accompanied by a downthrust between the

two ranges that formed the Puget-Willamette Trough and allowed the intrusion of continental

glaciers during the Pleistocene Epoch. It is estimated that the Vashon Glacier, present in the
24

Puget Sound area as recently as 15,000 years ago, cut and deepened many of the downthrust

valleys as much as 900 feet below present-day sea level (Yoshinaka and Ellifrit 1974).

The result is a long channel that is relatively narrow and deep, with a sharp northeastward

turn at the Great Bend near Union and Tahuya (Fig. 1). The Canal averages 2.4 km in width and

is widest (6.4 km) at the mouth of Dabob Bay (between the towns of Brinnon and Seabeck) and

narrowest (0.8 km) at Sister Point near the Great Bend. The average depth of the Canal is more

than 152 m, and maximal depths may exceed 182 m near Dabob Bay. Water is shallower east of

Great Bend, with shoaling continuing to the end of the Canal at the mouth of the Union River

near Belfair (Yoshinaka and Ellifrit 1974).

The Quilcene, Dosewallips, Duckabush, Hamma Hamma, and Skokomish Rivers on the

western side of the Canal drain the eastern slope of the Olympic Mountains (Table 1) (Fig. 3).

These rivers tend to be steep, with cool water and high river flows even in summer. Big Beef

Creek and the Dewatto, Tahuya, and Union Rivers drain the eastern shore of the Canal (Fig. 3).

They are smaller, lowland-type streams on the Kitsap Peninsula. The Kitsap Peninsula, part of a

glacial drift plain that covers much of Puget Sound, consists of low rolling hills usually less than

154 m high. The streams have very low flow levels in late summer and early fall. The greater

Hood Canal watershed is approximately 2,331 km2

.

Hood Canal, along with similar long channels in southern Puget Sound, contains

populations of summer-run chum salmon, a seasonal run more common in northern British

Columbia and Alaska. The Canal also contains populations of fall chum salmon, classified by

fishery co-managers in Washington State (WDF et al. 1993) as fall and late-fall stocks (Figs. 7ad). Possible reasons for this diversity of chum salmon include the abundance of quality

spawning grounds and the protected estuarine habitat afforded chum salmon smolts by this long

inlet.

The topographic character of Hood Canal results in a unique hydrographic mosaic of

weak tidal exchanges, seasonal nutrient loading, and low surface salinities. Although there is a

constant but limited tidal exchange with Puget Sound, glacial sills at the Canal entrance greatly

reduce water exchange and deepwater circulation. Only in late summer does cold, nutrient-rich

upwelling water from the Pacific Ocean intrude into the Canal (Yoshinaka and Ellifrit 1974).

Water exchange in the Canal is slow, because of strong tidal flows and significant water mixing

only in the north, nearest the entrance to Puget Sound. The southern Canal and Dabob Bay

experience weaker and less turbulent tidal exchanges, especially in the eastern arm

(Friebertshauser et al. 1971).

Hood Canal also has an exceptionally large freshwater lens (> 3 m in depth), especially

from December to June when river flows are high and tidal mixing is weak. The lens results in

warmer spring/early summer temperatures (when juveniles are feeding) and colder fall

temperatures (when adults return) than in more uniformly saline water (Phillips and Fleenor

1970).
25
26
27
28
29

Coastal British Columbia—The wet climate of the Olympic Peninsula continues north along

the west coast of Vancouver Island and along the British Columbia mainland north of Vancouver

Island (Fig. 5). Limited hydrographic data (Farley 1979) indicate that river flow patterns in this

area are similar to those on the Olympic Peninsula, with relatively high flows throughout the

year. Summer air temperatures generally decrease with increasing latitude—the Olympic coast

is a few degrees warmer than the southwestern coast of Vancouver Island, which is a few degrees

warmer than the northwestern coast and the mainland north of Vancouver Island.

Puget Sound and Strait of Georgia—A smaller gradient of decreasing average precipitation

extends from west to east in northwestern Washington (Figs. 1 and 5). East of the Olympic

Peninsula, precipitation rapidly decreases because of the rain shadow caused by the Olympic and

Vancouver Island mountains to the north and the Willapa Hills to the south. The rain shadow

continues through lowland Puget Sound, up the lowlands bordering the Strait of Georgia and to

the south end of Queen Charlotte Strait. Most of the Washington streams that support chum

salmon are in Puget Sound. This area receives less than 120 cm rain per year, with some areas

receiving as little as 50 cm/year.

There is apparently a slight summer temperature cline within the northern rain shadow

region; average maximal air temperatures in Puget Sound and Hood Canal (20-24o

C) are slightly

higher than those in the Strait of Georgia (16-20o

C), which in turn are higher than those inside

Vancouver Island farther north (14-16oC). In contrast, winter air temperatures are more uniform,

averaging 0-5oC throughout the area. Stream temperatures in the area are generally cool, with a

maximum of 12-20oC in summer and a minimum of 0-4oC in winter (Hydrosphere Data

Products, Inc. 1993).

Coastal Upwelling

Upwelling along the coasts of British Columbia, Washington, and Oregon north of Cape

Blanco is primarily wind driven (Smith 1983, Landry et al. 1989) and patterns are fairly

consistent among regions (Bakun 1973, 1975; Thompson 1981) (Fig. 5). One exception to these

patterns has been observed off the southwestern corner of Vancouver Island, where consistent

and strong upwelling apparently occurs throughout the year (Denman et al. 1981). Upwelling

south of Cape Blanco is thought to be caused by current-driven as well as wind-driven events,

leading to relative temporal and spatial stability.

Oceanic and Climatic Variability

Historically, research into the survival, growth, and production of Pacific salmon has

focused on the freshwater stages of their life cycles, with oceanic or climatic factors considered

relatively unimportant (Hare and Francis 1995). Part of the reason for this is the vast scale and

complexity of designing studies to investigate changes which may be local or global and occur

over months or millennia. For example, in 1970, the North Pacific winter atmospheric
30

circulation pattern shifted from previous years (Hollowed and Wooster 1992), but this discrete

event lasted only a single season. By contrast, the “little ice age” and other long-term climate

changes described in Chatters (1995) and Chatters et al. (1995) lasted for hundreds of years

(1200 to 1770 A.D.).

Although numerous climatic and oceanic cycles have been identified on several time

scales ranging from a few years (Kerr 1990, Hayward 1997), to hundreds (Kreutz et al.1997), to

thousands (COHMAP members 1988), to tens of thousands (GRIP members 1993), it has been

difficult to correlate these changes with salmon abundances. Physical and biological factors that

influence salmonid survival are usually highly correlated with each other and exhibit such

complex relationships that it is hard to separate cause from effect (Hare and Francis 1995). For

example, a biological factor such as intraspecific competition is affected by other biological

factors such as prey availability and predation, and these may be affected by climatic factors such

as regional cooling and increased freshwater run-off.

Only in recent years with advances in data collection/storage technology and the

increased availability of decadal-scale datasets, have comparisons between physical changes in

the ocean or climate and biological production of salmon become possible. Long-term datasets

of climatic factors—such as the Aleutian Low Pressure Index (ALP), Pacific Interdecadal

Oscillation (PDO) Index or the Cold Tongue (CT) Index (Beamish and Bouillon 1993, Hare and

Francis 1995, Francis and Mantua In press)—coupled with biological indices such as records of

copepod abundance, and Alaska salmon catches have revealed correlated positive and negative

trends (e.g., Francis and Sibley 1991, Beamish and Bouillon 1995, Hare and Francis 1995, Helle

and Hoffman 1995, Francis and Mantua In press). These trends suggest that regional variability

in biological production is caused in part by large-scale climate change reflected in North Pacific

atmospheric-oceanic regime shifts (Hare and Francis 1995). These oscillating “warm” and

“cool” regimes occur on decadal scales. The Pacific Northwest was warm from the early 1920s

to late 1940s/early 1950s, cool from the early 1950s to mid-1970s, warm from the mid-1970s to

the mid-1990s (Francis and Hare 1994) and appears to be presently shifting to a cooler, more

productive regime in the late 1990s (Francis and Mantua 1997).

Food Production and Zooplankton

Beamish and Bouillon (1993) were the first to develop evidence showing that annual

catches of chum, pink, and sockeye salmon in the North Pacific exhibit long-term parallel trends

that corresponded to climatic indices, particularly the ALP. Their analysis indicated that

increases in Alaskan salmon survival in the late 1970s occurred at the same time that year classes

of other commercially important marine fishes also had exceptionally high marine survival

(Beamish 1993). They hypothesized that this association was mediated in the late 1970s by large

increases in food (zooplankton, particularly copepods) for larval fishes (Brodeur and Ware 1992,

McFarlane and Beamish 1992, Beamish 1993). An alternative explanation was proposed by

Meacham and Clark (1994), who argued that the dramatic increases in commercial catches of

Alaskan salmon stocks since the 1970s are the result of sound management by the state of

Alaska.
31

Climate and salmon production: Alaska versus Northwest

There is also increasing evidence that the climatic patterns and trends in catch data for the

Pacific Northwest are opposite those for the Alaskan coast (Francis and Sibley 1991, Hollowed

and Wooster 1992, Francis and Hare 1994). Francis and Mantua (In press) reported that the PDO

was positively correlated with increased catches of

1) chum salmon in west and central Alaska and on west Vancouver Island and Puget Sound,

2) pink salmon in central and southeast Alaska and Oregon,

3) coho and sockeye salmon catches throughout Alaska,

4) coho salmon in Puget Sound,

5) sockeye salmon in West Vancouver Island, and

6) chinook salmon in Puget Sound and central Alaska.

Catches negatively correlated with the PDO include:

1) coho salmon in coastal Washington (but not Puget Sound), Oregon, and California, and

2) chinook salmon in west Vancouver Island, coastal Washington and California.

The mechanisms driving these changes are areas of intense research (reviewed in Francis

and Hare 1994), but the periodic oceanic regime shifts are due, at least in part, to changes in the

directions of the North Pacific Current, which splits in the eastern Pacific Ocean basin forming

two currents (California and Alaska Currents) that are out of phase with each other (reviewed in

Francis and Hare 1994).

Density Dependence

A second area of intense research is the question of whether density dependence or

carrying capacity influences Pacific salmon abundance in the North Pacific Ocean. If changes in

climate result in long-term changes in the survival and/or production of salmon in the North

Pacific Ocean, evidence of density dependence or carrying capacity should be expected. Some

evidence supports this contention. Helle (1979, 1984) and Helle and Hoffman (1995) rated a

trend of decreasing size and older age at maturity for chum salmon from Alaska to Hood Canal,

Washington, from the 1970s to the 1990s. Similarly, Ishida et al. (1993) showed significant

decreases in mean body weight and increases in mean age of Japanese and Russian chum salmon

during periods of increasing abundance in the 1970s and 1980s. Rogers (1980) and Peterman

(1984) demonstrated density-dependent growth in North American populations of sockeye

salmon. In Bristol Bay, Alaska, a highly productive natural system, Rogers and Ruggerone

(1993) found changes in size and age structure in sockeye salmon populations during years of

high abundance.

As noted by Beamish and Bouillon (1993), the primary evidence for density dependence
32

in the 1980s was decreasing size. However, during that period, food in the northeastern Pacific

Ocean apparently was increasing. They also noted that a density-dependent reduction in growth

occurred only in coastal waters during the early and final periods of marine residence when fish

compete primarily among themselves. They found little evidence of competitive interaction

among groups of fish from distant regions.

Beamish and Bouillon (1993) also suggested that hatcheries, except in Japan, were not

important contributors to the increase in chum salmon catches in the North Pacific during the

1970s and 1980s. They suggested that increases in Alaskan catches of chum salmon were so

great in the 1970s that hatcheries could have contributed to them only slightly. However, they

suggested that hatchery production strategies should take into account the interdecadal changes

in the ocean conditions relative to salmon production.

Biological Features

Vegetation

Patterns of vegetation in Washington and southern British Columbia are strongly affected

by precipitation. Coastal regions in Washington and British Columbia (Fig. 5) were historically

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, extending a few kilometers inland only over coastal plains,

and to elevations above 150 m only in areas immediately adjacent to the ocean (Franklin and

Dyrness 1973). Sitka spruce forests are replaced by western hemlock-dominated forests along

the Strait of Juan de Fuca to the north and east. 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 occur at about the

Elwha River on the Olympic Peninsula and Sooke Inlet on Vancouver Island (Figs. 1 and 5).

Because of Puget Sound’s lower precipitation and glacial soils, drought-tolerant pines, such as

western white, lodgepole, and occasionally ponderosa, are more common here than elsewhere in

the western hemlock zone.

Zoogeography

Only a few zoogeographic groupings of fishes, invertebrates, and amphibians have been

identified along the east coast of the North Pacific Ocean within the range considered in this

status review. There is a distinct faunal boundary for marine fishes off the northern tip of

Vancouver Island (approximately 50oN lat.) (Allen and Smith 1988), but there is no apparent

pattern of variation in marine fishes associated with chum salmon in southern British Columbia

or in Washington and Oregon. There is only one distinct group of estuarine fishes in the Pacific

Northwest, the Fjord group from Puget Sound and Hood Canal (Monaco et al. 1992). Other

estuary groupings are less evident and seem to depend more on characteristics of individual

estuaries rather than on geographic location. Regional differences are characterized not by
33

unique variation within species (distinct subspecies or populations), but by presence or absence

of species. Within the range of chum salmon in the Pacific Northwest, only one major

freshwater ichthyogeographic region, the Columbia, has been described (McPhail and Lindsey

1986, Minkley et al. 1986).

The distributions of marine invertebrates show transitions between major faunal

communities similar to those of marine fishes (Hall 1964, Valentine 1966, Hayden and Dolan

1976, Brusca and Wallerstein 1979). 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.

The distributions of many amphibian species appear to begin and end at several common

geographical areas within the range of chum salmon in the Pacific Northwest. The Strait of

Georgia and Vancouver Island are the northern extents of many amphibian distributions, such as

tailed and red-legged frogs, as well as Pacific giant, western long-toed, western red-backed,

Oregon, and brown salamanders (Cook 1984). In addition, several amphibians (Olympic torrent

and Van Dyke’s salamanders) are restricted to the Olympic Peninsula, while other species

(Pacific giant and Dunn’s salamanders) occur in most areas in western Washington and Oregon,

except in the Olympic Peninsula (Leonard et al. 1993).

Ecoregions

The U.S. Environmental Protection Agency has developed a system of ecoregions based

on patterns of factors such as land use, climate, topography, potential natural vegetation, and

soils (Omernik and Gallant 1986, Omernik 1987). Under this system, the range of chum salmon

in Washington covers two ecoregions that border on saltwater: the “Coast Range” ecoregion,

which extends from the Strait of Juan de Fuca to Monterey Bay and from the ocean to

approximately the crest of the coastal mountains; and the “Puget Lowland” ecoregion, which

begins in Washington at approximately the Dungeness River near the eastern end of the Strait of

Juan de Fuca and extends through Puget Sound to the British Columbia border.

Significance of Environmental Information for ESU Determinations

Based on the preceding physiographic, geological, climatic, and biological information,

there appears to be evidence for an environmental distinction between the following three areas:

the Columbia River and the coast, Hood Canal and the rest of the Olympic Peninsula, and the

Olympic Peninsula and the rest of the Pacific Northwest. However, because the gradients in

temperature and precipitation within the range of Northwest chum salmon are not sharp, and

based on the physical and biological factors examined here, the precise location of an

environmental “border” separating these areas is unclear.
34

Life-History and Ecological Information

Geographic Distribution

Chum salmon have a broader spawning distribution than any other species of Pacific

salmon (Bakkala 1970, Salo 1991) (Fig. 4). In Asia, they commonly spawn as far south as the

Naktong River in the Republic of Korea (35°N, 129°E) and the Tone River (36°N, 141°E) on

Honshu Island, Japan (Walters 1955, Atkinson et al. 1967). In some years, small numbers of

chum salmon occur in streams as far south as Nagasaki and Fukuoka Prefectures of Kyushu

(about 33°N) (Sano 1966). Historically, the range of the fish extended as far as the

Komandorskiye Islands (Smirnov 1975) and the area of present-day northeastern China, although

these populations were also reportedly intermittent and sporadic (K. Chew and L. Donaldson8, as

cited in Salo 1991). The northern range of chum salmon in Asia extends along the edge of the

Arctic Ocean, almost halfway across the Russian Federation to the Lena River (Laptev Sea)

(73°N, 125°E) (Soldatov and Lindberg 1930). However, these populations are small and may

occur only intermittently. Juvenile outmigration of these northern stocks often occurs beneath

the ice of rivers draining the shores of the Arctic Ocean (Sano 1966, 1967).

Historically, the largest and most commercially important run of chum salmon in Asia

was located in the Amur River, which flows more than 2,800 km along the border of China and

the Russian Federation. The Amur River is also the only site in Asia that has large runs of both

early (summer) and late (autumn) returning chum salmon within the same river basin (see

“Spawning Migrations,” p. 35). Other commercially important runs originate in Japan, on

Sakhalin Island (the northernmost part of which is opposite the mouth of the Amur River), in the

southern Kuril Islands, on the Kamchatka Peninsula north to the Anadyr River, and in

continental streams emptying into the Sea of Okhotsk. Sano (1966) divided chum salmon in

Asia into five geographic groups: West Kamchatka, East Kamchatka, Okhotsk, Sakhalin-Kurils,

and the Amur River.

In North America, chum salmon have been observed as far south as the San Lorenzo

River in Monterey, California (about 37°N, 122°W) (Scofield 1916), with spawning populations

as far as 322 km upstream in the Sacramento River (37°50’N 122°W) (Hallock and Fry 1967)

(Figs. 4-5). In recent years, chum salmon have been observed intermittently in northern

California (Moyle et al. in press) and southern Oregon (Kostow 1995) (see “Assessment of

Extinction Risk,” p. 144, for information on the occurrence of chum salmon in Oregon and

California). In North America, the northern range of the species extends to the shores of the

Arctic Ocean (Wynne-Edwards 1952), east to the Mackenzie River (69°N, 135°W) (Dymond

1940), and west across the north Pacific Ocean to Attu Island in the Aleutian Archipelago

(Holmes 1982).

8 K. Chew, School of Fisheries, University of Washington, Seattle, Washington 98195. Pers. commun.,

April 1995.
35

The geographic range of commercially important runs of North American chum salmon

has shrunk in recent years. The northernmost runs that support large commercial fisheries return

to Kotzebue Sound (Noatak and Kobuk Rivers) and the Yukon River (Buklis and Barton 1984)

(Fig. 4). Before the 1960s, the southernmost commercially important run of chum salmon in

North America occurred in Tillamook Bay, Oregon (45° 50' N) (Henry 1953, 1954) (Fig. 5).

This was a highly lucrative annual fishery, with chum salmon landings exceeding that of any

other salmonid in the Bay. However, Oregon closed this fishery in 1962 because of declining

abundances of these fish (see “Assessment of Extinction Risk,” p. 144, for further information).

In the 1940s, an important fishery of chum salmon developed in the Columbia River, with

commercial landings varying from 1 to 8 million pounds annually.

Since 1959, with a sharp decline in chum salmon abundance, commercial landings were

gradually reduced, until presently there are neither recreational nor directed commercial fisheries

for chum salmon in the Columbia River (ODFW and WDFW 1995). In the 1990s, the

southernmost commercial run of chum salmon in North America was in Willapa Bay and Grays

Harbor (Fig. 5). The harvest of chum salmon from these coastal fisheries averaged 96,000 fish

from 1988 to 1992 (WDFW 1995).

Spawning Migrations

In both Asia and North America, chum salmon spawn most commonly in the lower

reaches of rivers, with redds usually dug in the mainstem or in side channels of rivers from just

above tidal influence to nearly 100 km from the sea. In some areas (particularly in Alaska and

northern Asia), they typically spawn where upwelled groundwater percolates through the redds

(Bakkala 1970, Salo 1991). Some chum salmon even spawn in intertidal zones of streams at low

tide, especially in Alaska, where tidal fluctuation is extensive and upwelling of groundwater in

intertidal areas may provide preferred spawning sites (Helle9). Bailey (1964) reported that chum

salmon eggs in Olsen Creek, Alaska, could survive exposure to tidewater for up to 55% of the

time during embryonic development.

Chum salmon are believed to spawn primarily in the lower reaches of rivers because they

usually show little persistence in surmounting river blockages and falls. However, in some

systems, such as the Skagit River, Washington, chum salmon routinely migrate over long

distances upstream (at least 170 km in the Skagit River) (Hendrick10). In two other rivers, the

species swims a much greater distance. In the Yukon River, Alaska and the Amur River, the

Russian Federation, chum salmon migrate more than 2,500 km inland. Although these distances

9

 J. Helle, NMFS Alaska Fisheries Science Center, Auke Bay Laboratory, 11305 Glacier Hwy., Juneau,

Alaska 99801. Pers. commun., April 1995.

10 D. Hendrick, Washington Department of Fish and Wildlife, 333 East Blackburn Rd., Mt. Vernon,

Washington 98273. Pers. commun., January 1996.
36

are impressive, both rivers have low gradients and are without extensive falls or other blockages

to migration. In the Columbia River Basin, there are reports that chum salmon may historically

have spawned in the Umatilla and Walla Walla Rivers, more than 500 km from the sea (Nehlsen

et al. 1991). However, these fish would have had to pass Celilo Falls, a web of rapids and

cascades, which presumably was passable by chum salmon only at high water flows.

Timing of Spawning Migrations

Spawning migration refers to the movement of adults from seawater into their natal rivers

to spawn. Chum salmon may enter natal river systems from June to March, depending on

characteristics of the population or geographic location. Groups of fish entering a river system at

particular times or seasons are called “runs” (footnotes 1 and 2), and run timing has long been

used by the fishing community to distinguish anadromous populations of salmon, steelhead, and

sea-run cutthroat trout. Run-timing designations (e.g., summer versus fall or early-fall versus

late-fall) are important in this status review, because two of the ESA petitions for chum salmon

(PRO-Salmon 1994, Trout Unlimited 1994) used run timing as evidence supporting population

distinction.

In ESA status reviews for anadromous Pacific salmonids, run timing, along with

information for other biological and ecological characteristics, is evaluated from the perspective

of two criteria for defining ESUs—reproductive isolation and contribution to ecological and

genetic diversity (Waples 1991). Previous status reviews have shown that simply relying on

traditional run-time designations is not sufficient for identifying ESUs; each case must be

evaluated individually. For example, NMFS received petitions in 1990 to list three races of

chinook salmon (spring-, summer-, and fall-run fish) in the Snake River as threatened or

endangered species. The different runs were defined by fixed dates at which adults pass Lower

Granite Dam on the lower Snake River. The BRT looked for other evidence to evaluate the

biological significance of the nominal run-timing differences, because actual run timing in any

given year is variable and may span the cutoff dates. Snake River fall-run chinook salmon

spawn later and at a much lower altitude than do the other two forms, and also show substantial

differences from spring- and summer-run fish in genetic and juvenile and adult life-history

patterns. NMFS concluded on the basis of these differences that Snake River fall-run chinook

salmon were in a separate ESU from spring- and summer-run chinook salmon (Waples et al.

1991). Conversely, spring- and summer-run chinook salmon in the Snake River spawn in similar

habitats and cannot be reliably separated on the basis of genetic or life-history variation.

Therefore, the two forms were considered to be a single ESU (or species under the ESA), i.e.,

Snake River spring-summer chinook salmon (Matthews and Waples 1991).

Asian run timing

Biologists in both Asia and North America have used run-timing differences to separate
37

the species into early- or summer-run stocks and late- or autumn-run stocks11 (Berg 1934, Sano

1966, Bakkala 1970, Salo 1991). Chum salmon return to natal spawning streams on both

continents progressively later in southern areas. Chum salmon in northern Asia return only

during summer months (June, July, and August); whereas farther south, both summer (JulyAugust) and early autumn-run chum (September-October) salmon occur along the Amur River

and streams on Sakhalin Island (Fig. 4). On Honshu Island in Japan in the far south, near the

southern limit of their range, only autumn-run (October-November) chum salmon occur (Fig. 4).

The Amur River, which flows along the Russian-Chinese border, is almost 2,900 km in

length and is the largest Asian river entering the North Pacific Ocean (Fig. 4). In addition to

being the only major river in Asia with both seasonal runs of chum salmon, it has historically

supported both the largest runs and runs that migrate farther inland than any other on the

continent. Summer-run chum salmon enter the Amur River as early as July and spawn within

100 km of the sea. A second run of fish enters the system later in the fall, and some of these fish

are known to migrate 1,000 to 2,500 km inland. The number of autumn-run chum salmon in the

Amur River Basin has become so depressed in recent years that the run may be near extinction

(Semenchenko and Augerot12).

In Asia, summer-run fish are considered distinct from autumn-run fish. Berg (1934), who

first formally described Asian chum salmon, separated Asian chum salmon into seasonal races,

and considered the “autumn” chum salmon an “infraspecies,” O. k. autumnalis. However, while

other Asian investigators have supported Berg’s classification (Lovetskaya 1948; Grigo 1953;

Birman 1951, 1956; Hirano 1958; Sano 1966), this taxonomy has not found wide support in

North America, perhaps because North American chum salmon with different run timings are not

as geographically separated as in Asia. Characteristics of autumn-run fish used by Berg (1934)

and Sano (1966) to separate the seasonal runs include the following: 1) later entrance into

spawning streams, 2) less developed gametes at time of entry into natal streams, 3) later

spawning period, 4) larger size (≥3.5 kg versus ≤2.5 kg for summer-run fish), and 5) greater

fecundity than summer-run chum salmon.

North American run timing

In North America, return timing of chum salmon also follows a general north-to-south

cline of earlier to later returns, similar to that seen in Asia. Only summer-run chum salmon

generally enter streams along the northern Bering Sea and Arctic coast; fall-run fish occur in

11 “Fall” is used synonymously with “autumn” to describe run times in this report. “Autumn” is most

commonly used in the literature to refer to chum salmon in Asia, and “fall” refers to chum salmon in

North America. Also see footnote 1.

12 A. Semenchencko, Pacific Institute of Fisheries and Oceanographic Research (TINRO), 4 Shevchenko

Alley, Vladivostok, 690600 Russia; and X. Augerot, Center for the Analysis of Environmental Change,

Oregon State University, Nash Hall, Corvallis, OR 97331. Pers. commun., July 1996.
38

rivers bordering the southern Bering Sea and Gulf of Alaska; and both summer and fall runs

commonly occur in southeast Alaska and northern British Columbia (Fig. 4). Fall-run fish occur

primarily south of Vancouver Island (Bakkala 1970). Latitudinal changes in run timing occur in

both Asia and North America. However, in Asia, geographic separation between fish with falland summer-run times appears to be distinct (Bakkala 1970), whereas in North America, many

streams have both fall- and summer-run chum salmon populations. Also, in contrast to Asian

summer-run chum salmon, many North American summer-run fish mature at older ages, are

larger, and have higher fecundities than do fall-run chum salmon in the same region. Overall, the

differences between summer and fall runs in North America are not nearly as distinct or well

developed as those reported in Asia. This led Salo (1991) to suggest that most summer runs in

North America should more accurately be called early fall runs, and that the only North

American populations with the same distinguishing characteristics as the Asian summer chum

salmon are in the Yukon River.

Alaska run timing—Chum salmon in northern Alaska tend to return earlier than do chum

salmon farther south. Although this is similar to the pattern seen in Asia, Alaskan chum salmon

in general show greater diversity in run timing than chum salmon across a similar range of

latitude in Asia, with many Alaskan basins having runs that return from July through November.

For example, tagging studies by Yanagawa13, Bigler (1983, 1985), and Bigler and Burwen (1984)

have shown a bimodal return timing of chum salmon in some rivers in the far north in Kotzebue

Sound (around 67°N). The spawning run into Kotzebue Sound is primarily composed of fish

that spawn in the Noatak and Kobuk Rivers, with the Noatak River supporting about threequarters of the Sound’s total return (Bigler 1983) (Fig. 4). Kobuk River chum salmon enter

Kotzebue Sound earlier than Noatak River chum salmon (Yanagawa footnote 12), and chum

salmon in Kobuk River spawn in the lower tributaries from late July to late August and in the

upper tributaries from late August well into October (Bigler and Burwen 1984). Spawning in the

Noatak River showed a single peak in the lower 160 km of the river from mid-August to midOctober.

The Yukon River drainage (river mouth about 63°N) supports populations of chum

salmon that not only have one of the most distinctive bimodal summer/fall-run patterns of return

for chum salmon in North America, but also make the longest freshwater migration in the world

(Buklis and Barton 1984) (Fig. 4). Chum salmon in the Yukon River share many similarities

with those of the Amur River of Asia. Both of these large rivers have long (>2,500 km) stretches

accessible to anadromous fish, and both have low gradients with no barrier falls (Buklis and

Barton 1984, Brannian and Gnath 1988). Both Amur and Yukon River chum salmon consist of

summer-run and fall-run fish, but unlike chinook salmon or steelhead trout in the contiguous

United States, these run-time designations refer to time of spawning and not to time of river

entry. In both rivers, summer-run chum salmon were historically more numerous (and in the

Yukon still are more numerous), return in fuller spawning coloration, are less fecund, and are

13 C.M. Yanagawa. 1968. Kotzebue chum salmon tagging projects, 1966-1968. AYK Region Fishery

Bulletin #7, cited in Bigler and Burwen 1984.
39

smaller than fall-run chum salmon (Berg 1934, Sano 1966, Buklis and Barton 1984). However,

unlike the runs in the Amur River, the two runs in the Yukon River have an overlap in return

times (Berg 1934, Buklis and Barton 1984). Yukon River summer-run chum salmon enter the

river mouth from early May through mid-July, whereas some Yukon River fall-run chum salmon

(e.g., Fishing Branch Creek in the upper river) enter as early as the beginning of June (Buklis and

Barton 1984). Chum salmon returning to the Yukon River are considered predominantly fall-run

fish that return from mid-July through early September (Brady 1983).

Summer-run chum salmon in both the Yukon and Amur Rivers spawn primarily in

tributaries that empty into the lower part of the main stem, whereas fall-run fish spawn farther

upstream in spring-fed streams and sloughs (Buklis 1981, Buklis and Barton 1984, Salo 1991).

Some late-returning chum salmon in the Yukon River travel almost 3,200 km from the mouth of

the river to its headwaters, near Teslin Lake in British Columbia. This freshwater migration is

more than 700 km farther than the longest chum salmon migration on the Amur River.

Farther south, in rivers flowing into Bristol Bay (about 58°N), chum salmon return from

mid-June through July, with a peak the first week of July (Salo 1991) (Fig. 4). On the Alaska

Peninsula, return times are in July and August. In the Kuskokwim River, spawning is in late

August and September. In central Alaska (e.g., eastern shore of Prince William Sound), some

chum salmon first enter streams in mid-June, but the peak of spawning is primarily in late July

and August. Throughout this area, run timing varies greatly between river basins, but is

relatively consistent from year to year within basins (Helle14).

In Southeast Alaska, catch statistics from 1984 indicate that nearshore abundance peaked

in the first 2 weeks in August, and that the median timing of the escapements occurred from late

August to mid-September (Clark and Weller 1986). Spawning chum salmon are difficult to

count in the many rivers and streams of this region, because of the large numbers of pink salmon

also present in the streams (Helle footnote 14). However, it is clear that the run timings of these

chum salmon are diverse, ranging from mid-June through December. As an example, Helle

observed that chum salmon first entered some mainland streams in Behm Canal and Portland

Canal in southern Southeast Alaska in mid-June, with peak numbers occurring in mid-August.

Fish began to enter natal streams on islands in September, and the run did not peak until midOctober (Helle footnote 13). Spawning has also been observed in October near the mouth of the

Alsek River in the Yakutat area (Salo 1991). An exceptionally late run of large, fall-run chum

salmon return to the Chilkat River near Haines (Cline 1982), and the timing of this run appears to

be influenced by upwelling groundwater in sloughs exposed after the glacial waters of the

Klehini and Chilkat Rivers recede in the fall (Helle footnote 13). Large numbers of bald eagles

congregate in these sloughs in late fall and early winter to feed on the chum salmon carcasses

(Helle footnote 13).

British Columbia run timing_Tables 2 and 3 list rivers in British Columbia that support

escapements greater than 5,000 chum salmon annually and show run timings (start, peak, end)

14 J. Helle, NMFS Alaska Fisheries Science Center, Auke Bay Laboratory, 11305 Glacier Hwy., Juneau,

Alaska 99801. Pers. commun., November 1995.
40
41
42
43

for each population (Aro and Shepard 1967). Escapements were estimated from catches in inside

passages and inlets close to spawning areas. Spawning times were estimated from a variety of

stream surveys (e.g., foot, plane, photographs), although Aro and Shepard (1967) cautioned that

the dates of runs were approximate because information from different surveys was not always

comparable. Since chum salmon spawning areas are spread more evenly over a large number of

moderately sized streams in British Columbia, the species is more difficult to survey in spawning

areas than are sockeye and pink salmon. Nonetheless, surveys have shown that chum salmon

spawn in the lower reaches of more than 880 streams in British Columbia and that this

population is fairly well distributed among the streams. Aro and Shepard (1967) calculated that

the most productive 58 streams produced only 50% of the estimated total chum salmon

escapement, while 75% of the total pink salmon run in British Columbia occurred in the most

productive 58 streams, and 75% of the sockeye salmon escapement occurred in only 29 streams.

In general, there is a distinct north-to-south cline of early-to-late return and spawning

times in British Columbia, similar to the clines for these variables in Asia and Alaska. Chum

salmon pass through inshore fishing areas near the northern mainland of British Columbia in July

and August (summer runs), and catches peak in August along the coast of north-central British

Columbia, near Bella Bella and Bella Coola. Catches are made primarily in August and

September around the Queen Charlotte Islands. Return times of chum salmon into northern

rivers around Johnstone Strait and the Strait of Georgia are usually earlier (early October) than

they are in southern rivers, such as the Cowichan River (late December). Peak catches north of

Vancouver Island occur from mid-July to mid-September, and southern British Columbia peak

catches are in October (Beacham 1984).

Aro and Shepard (1967) also found a marked cline for spawning time. They found 64

rivers with “major stocks” of chum salmon north of Vancouver Island (Statistical Area 13), and

all but two of these runs appear to spawn in August or September. Farther south (Statistical Area

13 and higher), 47 major runs were listed, but only one spawned as early as August (Toba River,

Section 15), and only eight spawned in September. All other runs began spawning in October or

November. Most southern runs completed spawning by the end of December, but six apparently

continued to spawn into January. In the north, all but six runs completed spawning by the end of

October, and these six finished spawning by November.

Canadian biologists do not classify chum salmon runs into “summer” or “fall” categories.

However, spawning in southern British Columbia occurs principally from October to January

(Tables 2 and 3). Early spawning and summer runs of chum salmon are rare in southern British

Columbia, and no July spawners have been reported. Rivers on northern Vancouver Island and

those opposite on the mainland with late-summer or August spawning times include the

Ahnuhati, Keogh, Kingcome, Quatse, and Waterfall Rivers, and Ahta Valley Creek. Spawning

peaks in October in most of these rivers, but continues into November. Farther south, midway

down Vancouver Island and on the opposite mainland (Toba River), chum salmon spawning

begins in August and continues through December. Spawning peaks in mid-November, not in

October as it does to the north. On southern Vancouver Island, chum salmon spawn in the

Nanaimo River (average escapement 20,000-50,000 per year) from September to January, with a

peak in October. On the outer southern coast of Vancouver Island, chum salmon run from
44

September to November into the Toquart River (20,000-50,000 escapement) and peak in

October. Similarly, on the middle outer coast of Vancouver Island, fish in the Zeballo River

(5,000-10,000 escapement) spawn from September to November (Aro and Shepard 1967). No

data are available to indicate whether there is a break between the early and late portions of the

run, but the runs appear to be continuous (Beacham15).

Washington run timing—Most chum salmon in Washington are classified as fall-run fish and

generally return to their natal streams from October to November, although distinct summer and

winter runs of chum salmon are recognized. WDFW and WWTIT (SASSI: WDF et al 1993)

listed return times for 72 runs of chum salmon: 62 are classified as fall runs, 2 as winter runs

(both in southern Puget Sound), and 8 as summer runs (4 in southern Puget Sound and 4 in Hood

Canal/Strait of Juan de Fuca) (Table 4; and Fig. 7a-d).

Puget Sound run timing—Only fall (October to late November) runs have been observed

in the rivers of northern Puget Sound (Nooksack, Skagit, Stillaguamish, Skykomish, and

Snohomish Rivers) (Atkinson et al. 1967; Hiss et al. 1982a; WDF et al. 1993). However, there is

a greater variability in river entry and spawning time within these fall runs than runs in British

Columbia. Salo (1991) suggested this regional difference was due to the presence of a larger

number of moderate-to-large rivers in Washington than in British Columbia, and to the fact that

chum salmon spawn farther upstream in Washington rivers. For example, chum salmon were

tagged at the mouths of the Stillaguamish and Nooksack Rivers, and spawn timing was

calculated from tagged carcasses counted on spawning grounds (Hiss et al. 1982a, 1982b). In the

Stillaguamish River, the average time between tagging and spawning-area recovery was 31 days,

and some fish spent more than 6 weeks in freshwater before spawning. Also, different parts of

the river basins had different spawning times; in general, return times to spawning areas higher

in the river basin were progressively later than return times to spawning areas lower in the basin

(Tables 5-7) (Hiss et al. 1982a, 1982b).

All three seasonal runs (summer, fall, and winter) occur in Puget Sound (Table 4; Fig. 7ab) (WDF et al. 1993). Summer-run chum salmon spawn from September to mid-October, and

WDFW has identified three summer chum salmon runs: Case Inlet, Hammersley Inlet, and

Blackjack Creek. A fourth run into Chambers Creek, north of the Nisqually Delta, in summer

was listed as extinct (SASSI: WDF et al. 1993). Existing runs exhibit a wide range of spawning

times that extend from late August to mid-October (Hammersley Inlet), through mid-September

to early November (Case Inlet), to mid-October and mid-November (Blackjack Creek near Port

Orchard, Washington). With the exception of Blackjack Creek, these runs have been

supplemented with fry from local spawners, which were reared at Johns Creek Hatchery

(Hammersley Inlet) and at Coulter Creek Hatchery (Case Inlet).

Chambers Creek, a southern Puget Sound stream that empties into the Tacoma Narrows,

also once contained a run of summer fish (WDF et al. 1993). The existence of the run was

15 T. Beacham, Department of Fisheries and Oceans, Biological Sciences Branch, Pacific Biological

Station, Nanaimo, B.C., Canada V9R 5K6. Pers. commun., September 1995.
45
46
47
48
49
50
51

inferred from weir counts in the 1970s and 1980s at the Garrison Creek Hatchery, which is

located on a tributary of Chambers Creek. Hood Canal chum salmon with November return

timing were introduced into Chambers Creek in the 1970s. Until the SASSI review, chum

salmon returning to Chambers Creek before 10 December were assumed to be a mix of the “early

native stock” and introduced fish (Crawford 1997); fish returning after 10 December were

considered natural winter-run chum salmon. However, analysis of weir counts at the hatchery

revealed an earlier run beginning about the third week in September and peaking about the third

week in October. The early run was considered to be extinct by about 1983 when only three fish

were observed in the creek. November-returning fish of Hood Canal origin have not been

observed in Chambers Creek since 1986, but winter-run chum salmon still return to the creek

(see below).

The Chambers Creek winter-run fish enter the river from early December to late January

(Table 4) and are reported in SASSI to be geographically and temporally isolated from other

Puget Sound runs (WDF et al. 1993). As reported by Crawford (1997:5), “The issue of spawner

overlap with winter chum is moot, since summer and ‘fall’ chum are no longer present.”

Winter-run chum salmon (defined in the SASSI report [WDF et al. 1993] as fish with an

average peak of spawning after 10 January) also occur in the Nisqually River in southern Puget

Sound (Table 4) (WDF et al. 1993). This winter run and the winter run in Chambers Creek may

be the latest returning chum salmon in the world. Tagged chum salmon caught by purse seines

in the Nisqually River estuary between late November and mid-January from 1974 to 1980 were

recaptured from mid-December to late February/early March at weirs on two spawning ground

tributaries, Muck and Yelm Creeks (Cole et al. 1986). Small numbers of fall-timed chum salmon

are caught in a tribal fishery in the Nisqually River basin, but WDFW does not believe these fish

represent a self-sustainable fall run (Turner 1995). Stream surveys or other data for these fall

fish are not available. These fall fish may be strays or they may be from hatchery programs in the

Nisqually River Basin. These hatchery programs have primarily reared winter-run fish, but

summer-run fish from Johns Creek and fall-run fish from Kennedy Creek, Hood Canal, and

Bonneville Hatchery Complex on the Columbia River have also been propagated (see

Appendix).

Nine groups of natural fall-run chum salmon in southern Puget Sound were identified in

the SASSI report (WDF et al. 1993) (Table 4). One of these, the Eld Inlet fall-run chum salmon,

contained fish that return to Allison Springs, which was the focus of the petition submitted by the

“Save Allison Springs” Citizens Committee (1994). These southern Puget Sound chum salmon

spawn from mid-October to late January, with the long duration of spawning apparently caused

by differences among the populations. These fish are reported in the SASSI report (WDF et al.

1993) to be isolated by distance, and to some degree by run timing differences, from other

groups of chum salmon in Puget Sound.

Eld Inlet is located between Totten and Henderson Inlets, near the southern end of Puget

Sound (Fig. 2) and is fed by freshwater streams near its terminus. The primary tributaries

emptying into Eld Inlet where fish spawn are McLane, Swift, and Perry Creeks. Chum salmon

returning to Eld Inlet enter southern Puget Sound (WDF et al. 1993) from late October to mid-
52

December, with river entry and spawning from late November to early January. Although this is

a broad spawning time compared to other fall chum salmon in Puget Sound, WDFW points out

that it is “much later than the Puget Sound summer stocks” (WDF et al. 1993, Appendix 1—

Hood Canal and Strait of Juan de Fuca, p. 259), the only other chum salmon spawning in the

region. Spawn timing of other fall-run chum salmon in southern Puget Sound are shown in

Table 4.

Hood Canal summer chum salmon run timing—Co-managers in Washington have

classified chum salmon in Hood Canal as summer- and fall-returning stocks (Fig. 7). Run-timing

and other life-history characteristics for the SE populations have been extensively reviewed by

Tynan (1997). Information recorded from 1913 to 1914 (Fig. 8) at the Quilcene National Fish

Hatchery on the Big Quilcene River in northern Hood Canal (Fig. 3) indicated a separation of

almost a month between the end of the summer chum salmon run and the beginning of the fall

run (Cook-Tabor and Zajac). The SASSI report (WDF et al. 1993) states that, at present, the

“summer” spawning of the early run occurs from early-September to mid-October, while the

“fall” run spawns from early November to late December (Table 4, Fig. 7c). Graphs of spawning

survey data collected by WDFW (Fig. 9) and catch survey patterns developed by the Point No

Point Treaty tribes (Figs. 10 and 11; Lampsakis6

) also show nearly a month’s separation between

peak catches of summer-run chum salmon and natural, fall-run chum salmon in Hood Canal

(Fishery Management Area 12).

Summer-, but not fall-run, chum salmon also occur in two bays on the eastern end of the

Strait of Juan de Fuca (Fig. 1). These fish have run times similar to those of summer-run fish in

Hood Canal (Table 4, Fig. 7c). A run of early-returning chum salmon was recently observed in

the Dungeness River, but no life-history, abundance, or other data for the run are available

(Johnson7

).

Hood Canal fall chum salmon run timing—Co-managers in Hood Canal (WDF et al.

1993) identified 10 naturally spawning Hood Canal fall chum salmon stocks: Northeast Hood

Canal, Dewatto, Southeast Hood Canal, Lower Skokomish, Upper Skokomish Late, West Hood

Canal, Hamma Hamma Late, Duckabush Late, Dosewallips Late, and Quilcene Late. Fall-run

chum salmon in the SASSI report are defined as fish that enter the terminal area in Hood Canal

(terminal areas are Fishery Management Areas 12A, B, C, and D) (Fig. 3) between the first week

16 C. Cook-Tabor and D. Zajac, U.S. Department of Interior, Fish and Wildlife Service, Western

Washington Fishery Resource Office, 2625 Parkmont Lane, Bldg. A, Olympia, Washington 98502. Pers.

commun., March 1995.

17 N. Lampsakis, Fisheries Office, Point No Point Treaty Council, 7999 N.E. Salish lane, Kingston,

Washington 98346. Pers. commun., March 1995.

18 R. Johnson, 133 LipLip Land, Nordland, Washington 98358. Pers. commun., May 1995.
53
54
55
56
57
58
59

in October and the first week in January. These stocks are separated by the co-managers based

on two criteria: geographic separation of spawning grounds and differences in run timing (WDF

et al. 1993, Appendix 1—Hood Canal and Strait of Juan de Fuca, p. 43):

Spawning [of fall-run chum salmon] begins about the third week in October and may continue

through January. This long duration is a result of timing differences among the nine fall chum

stocks in the area which are classified for management purposes as “early fall” and “late fall”

stocks.

Fall chum spawning in this region is isolated from other Puget Sound chum stocks primarily

through geographic separation. Hood Canal summer chum are separated by a clear difference in

the spawning seasons from the fall stocks. Hood Canal fall chum were separated into 10 stocks

based primarily on geographic separation of the spawning grounds. However, in some cases runtiming differences were also large enough to consider separation of stocks.

However, this does not mean fall chum salmon in Hood Canal were classified in SASSI

by run timing “primarily for management purposes.” Crawford (1997:6) argues that

Differences in run timing of Hood Canal fall chum stocks was considered but in all cases there

was significant timing overlap, and none of the fall timed stocks would have been identified as a

distinct stock based solely on timing differences. The timing difference criterion was only used

in support of spawning distribution, and was always characterized in the individual stock reports

as “to some degree by differences in run timing.” The reference to SASSI characterizing stocks

based on “management differences in run timing” is not correct. Fishery management elements

were not a part of the SASSI stock identification or stock rating process. The confusion here

probably arises from the fact that WDFW staff feel that because there is so much overlap in

timing among the Hood Canal fall chum stocks, the distinction between fall timing and “late” fall

timing is only useful in a management sense; to fine tune management dates for fisheries.

Hatchery production of fall chum salmon in Hood Canal is large compared to other

locations in Washington or British Columbia. This hatchery production also had an effect on the

identification of some fall chum salmon stocks in SASSI (WDF et al. 1993, Appendix 1—Hood

Canal and Strait of Juan de Fuca, p. 42):

The West Hood Canal fall chum stock is comprised of chum spawning in small, independent

tributaries located on the west side of the canal. These fish were identified as a single stock for

two reasons: 1) The proximity of many of these streams allows for the possibility of

commingling of the spawners on the spawning grounds, and 2) large hatchery plants and/or major

egg box projects using Hood Canal (Hoodsport) Hatchery stock are ongoing in these streams and

have established runs with a similar genetic makeup. The Hood Canal Hatchery stock originated

from Finch Creek, one of the west-side independent tributaries. Accordingly, these fish were

identified as a mixture of native and non-native fish.

Less run-timing information is available on early fall-run chum salmon in Hood Canal

(Table 4, Fig. 7c) (WDF et al. 1993) than for most other chum salmon populations. The SASSI

report provided “terminal run,” “river entry,” and “spawning” timings when available for each

stock listed in the survey; however, for early fall-run fish in Hood Canal, this information was
60

reported in SASSI for only one of the five early-returning groups reported. For late fall-run fish,

all groups have timing reported for all three factors. The early-run group with the most complete

record of run timing is the West Hood Canal fall-run chum salmon. These fish are reported to

enter the terminal areas between mid-October and late November, begin up-river migrations

between early November and mid-December, and spawn between mid-November and midDecember. Only spawn timing is reported for all other early fall-run fish, which is thought to

occur from mid-October to about mid-December (WDF et al. 1993). Based upon this reported

time of spawning, there is often no clear distinction between “spawn time” in early- and late-run

fall chum salmon in Hood Canal. All late fall-run chum salmon begin to enter terminal areas in

mid-October and spawn from mid-December to late January (WDF et al. 1993). For example,

“Dosewallips Late Fall Chum” stock (WDF et al. 1993, Appendix 1—Hood Canal and Strait of

Juan de Fuca, p. 80) reach the entrance to Hood Canal (Terminal Area 12) from mid-October to

mid-December, but do not enter the river to spawn until mid-November to mid-January. An

early fall run of chum salmon (“Northeast Hood Canal Fall Chum”) (WDF et al. 1993), which

spawns in a broad swath approximately opposite the mouth of the Dosewallips River, is reported

to spawn between mid-November and mid-December (WDF et al. 1993). Clearly, the spawning

times of these early and late fall-run fish can overlap.

Washington and Oregon coast run timing—Chum salmon appear to return to tributaries

on the Washington and Oregon coasts in October and November and to spawn as late as

December, but data are limited (WDF et al. 1993, Kostow 1995). Long-term run times for

coastal Oregon chum salmon are available only for Tillamook Bay, which fish enter in October

and November. However, spawning may continue into late December, as it does on the

Washington coast (Henry 1954, Cooney and Jacobs 1994). Smaller runs of chum salmon are

reportedly found farther south in Netarts Bay, Nestucca River, Yaquina River, Siuslaw River,

and Coos Bay, although run times for these fish are not available.

Columbia River run timing—Chum salmon are limited to tributaries below Bonneville

Dam, with the majority of fish spawning on the Washington side of the Columbia River. Chum

salmon have been reported in October in the Washougal, Lewis, Kalama, and Cowlitz Rivers in

Washington and to the Sandy River in Oregon (Salo 1991). Only three Washington runs (Grays

River, Hamilton Creek, and Hardy Creek) were listed in the SASSI report, and all return in about

October (the peak is mid-November), a run time similar to that of chum salmon in rivers along

the Washington coast (Table 4) (WDF et al. 1993). Grays River chum salmon enter the

Columbia River from mid-October to mid-November, but apparently do not reach the Grays

River until late October to early December. These fish spawn from early November to late

December. Fish returning to Hamilton and Hardy Creeks begin to appear in the Columbia River

earlier than Grays River fish (late September to late October) and have a more protracted spawn

timing (mid-November to mid-January). The Oregon Department of Fish and Wildlife (ODFW)

cited 25 locations in that state where chum salmon spawn in the lower Columbia River, but run

times for these fish are unavailable (Kostow 1995).
61

Marine Travel Time to Spawning Grounds

Chum salmon in different runs may swim at different speeds during their return

migrations from oceanic feeding grounds (Salo 1991). However, an insufficient number of

studies have been conducted to determine run-specific travel times. For example, Lyamin (1949)

found that chum salmon tagged at different locations migrated between 300 km in 15 days (20

km/day) and 1,200 km in 15 days (80 km/day), whereas Shmidt (1947, cited in Lyamin 1949)

reported maximal speeds of 43-63 km/day. Fish tagged in British Columbia traveled at a rate of

14 km/day from Johnstone Strait to the mouth of Fraser River (Anderson and Beacham 1983).

An additional complication in calculating stock-specific timing of freshwater entry is

“milling” (Hunter 1959, Koski 1975): All species of anadromous salmonids may delay their

entry into freshwater or into terminal spawning areas as they approach the mouths of their natal

rivers at the end of the marine phase of their life cycle. For example, some tagged chum salmon

in Skagit Bay remained in the estuary for up to 21 days (Eames et al. 1981). Also, as noted

above, the average time between tagging at the mouth of the Stillaguamish River and recovery of

marked carcasses on the spawning grounds was 31 days (Hiss et al. 1982a, b). Some of these

tagged fish spent more than 6 weeks in freshwater before spawning (Hiss et al. 1982a, b).

Chum salmon are particularly vulnerable to fisheries and natural predation during this

period of milling. For example, Evenson and Calambokidis (1993) found that the number of

harbor seals at Dosewallips State Park in Hood Canal, Washington, was highest when adult

chum salmon were present. Fisheries aimed at other species or more plentiful hatchery stocks of

chum salmon (as described by Tynan (1992) and Cook-Tabor (1995) for Hood Canal) can also

incidentally harvest fish milling in Hood Canal. Adult chum salmon concentrate in such large

numbers in estuaries and off the mouths of small streams that their dorsal fins break the water’s

surface. The cause of milling is unclear, although maturation may play a role, but often fish will

move into a river only after a period of rain, when water flow increases. For whatever reason,

the period of milling becomes shorter as the spawning season progresses (Salo 1991).

Straying

In the past, observations of chum salmon behavior have suggested to some that the

species may have a greater tendency to stray than other species of Oncorhynchus (reviewed in

Lister et al. 1981). There are a number of reasons why this perception could have developed. 1)

O. keta spawn near the mouths of streams, and their young do not conduct the long, downstream,

freshwater migrations that are common in some salmonid species. It has been hypothesized that

juvenile salmonids who do conduct long, freshwater migrations may sequentially imprint on a

chain of migratory cues that assist them as adults in returning to their natal streams (Lister et al.

1981). 2) Observations of the reluctance of adult chum salmon to surmount small falls or rapids

have suggested to some that they may go upstream as far as they can toward natal areas, but once

they reach a barrier, they spawn. 3) Adult chum salmon also are more sexually mature when

they enter freshwater than most species of anadromous salmonids and may not be able to endure

delays in reaching their natal areas; if delayed, they may be forced to spawn at the first available
62

location. 4) It has been observed (McNeil 1969, Lister et al. 1981) that, when spawning densities

of chum salmon become high in some rivers (especially those with hatchery runs), straying to

nearby streams may increase.

Only a few experimental studies have directly addressed this issue (Lister et al. 1981;

Quinn 1984, 1993; Salo 1991; Altukhov and Salmenkova 1994; Tallman and Healy 1994), and

these studies have concluded that under normal circumstances, straying in chum salmon is no

greater than in any other species of Oncorhynchus. Lister et al. (1981) reviewed experimental

studies on straying in all species of Pacific salmon, but found only a few unpublished reports that

used chum salmon as the study species (Table 8). In a review of the life history of chum salmon,

Salo (1991) found that the only information relevant to straying in chum salmon was collected

incidentally from studies designed for other purposes. Genetic studies of straying for all species

of Pacific salmon are limited (reviewed in Quinn 1984, 1993, 1997), and only one experimental

study of chum salmon straying has been published (Smoker and Thrower 1995).

Mark-release and recapture studies—The first reported experimental mark-release study to

document straying in chum salmon was conducted in Japan by Sakano (1960, cited in Okazaki

1982a). In this study, over 2 million native, fin-clipped chum salmon fry were released into the

Tokoro River on northern Hokkaido Island and into the Chitose River on the southern part of the

island. Both the Tokoro and Chitose Rivers are large rivers that empty directly into the sea, and

“straying” in this study is defined as the portion of fish that were captured in a river system other

than their native Tokoro or Chitose Rivers. The straying rate was estimated to be only 2% for

fish released into the Tokoro River, with most of the fish recovered in their natal stream.

However, some strays were recovered as far as 350 km away in the Teshio River on western

Hokkaido Island. Fish released into the Chitose River strayed at a rate as high as 10%, with

marked fish recovered as far as 2,000 km away on Honshu Island. However, this rate of straying

among fish released into the Teshio River has perhaps been underestimated, due to an inadequate

geographic sampling range; most of the rivers monitored were on Hokkaido Island, while many

strays were incidentally recovered far to the south on Honshu Island (Okazaki 1982a).

Salo (1991) collated information on straying and homing in chum salmon from studies

designed to gather other kinds of information. For example, Salo and Noble (1952a, b; 1953)

marked juvenile (dorsal fin marks) and adult chum salmon (fin clips) at the mouth of Minter

Creek, Washington for 2 years and found no marked adults in nearby streams. In another study

cited by Salo (1991), Wolcott (1978) released fry from the Quilcene National Fish Hatchery into

Walcott Slough, near Brinnon on Hood Canal, and found no strays in nearby streams. The

authors concluded that adults returned “unerringly” to traps on the slough, even though a natural

run did not exist there. In his own studies, Salo (1991) observed that adult chum salmon returned

to a weir trap set at the outlet of a small stream from which the fish had emigrated as fry and not

to a nearby trap set on the mainstream. These results were taken by Salo (1991) as support for

strong homing behavior in chum salmon.
63
64

In their review of straying in Pacific salmon, Lister et al. (1981) identified one

unpublished mark-and-release study on chum salmon in Alaska and two studies from the Fraser

River in Canada. These studies were summarized in a common format and published as

appendices by Lister et al. (1981). In the Alaskan study, Freitag and Ward (reported in Lister et

al. 1981) (Table 8) designed a study to evaluate imprinting in off-site rearing facilities: They

reared chum salmon to the fry stage in two hatcheries, then released some into their natal stream

and others from a hatchery. Straying was defined as occurring when fish were captured at sites

other than where they had been released as juveniles. None of the fish released into their natal

stream were found in nearby streams. However, these results were inconclusive, because only 17

of 100,000 marked fish returned over the 2 years of the study. An 8.8% straying rate, based on

returns of 56 fish (0.12% of the total release), was reported for the fish released from the

hatchery.

The two studies identified by Lister et al. (1981) on straying in chum salmon in the lower

Fraser River did not involve transfers of fish from one area to another. Straying was also defined

in these studies as occurring when fish were captured in streams other than where they had been

released as juveniles. In the first study, fish from Inches-Barnes Creek, a tributary to the Fraser

River, were spawned and eggs reared in a hatchery on the creek (Foye, reported in Lister et al.

1981). Juveniles were fin-clipped as fed fry and released into the creek. The returning adults

strayed at a rate of 7.2% to streams within 2 km of the natal stream. In another study, adults

from Blaney Creek, a tributary to the North Alouette River on the lower Fraser River, were

spawned and their eggs incubated at a facility on-site (Harding, reported in Lister et al. 1981).

Juveniles were fin-clipped and released into Blaney Creek (252,900 were released in 1974 and

190,033 in 1975). A large difference in adult straying was found between the 2 years, with

45.7% straying in 1977 but only 9.3% in 1978 (Harding 1981, cited in Lister et al. 1981).

Harding hypothesized that the high straying rate in 1977 resulted from a large escapement that

saturated available spawning sites in Blaney Creek, forcing many fish to seek other areas to

spawn. Blaney Creek had a spawning density of 1.7 females/m2 in 1977, but only 0.2 females/m2

in 1978 (Banford and Bailey 1979). While spawner densities vary greatly among spawning

areas, the density in 1977 was more than twice the optimal density for chum salmon suggested

by McNeil (1969).

Lister et al. (1981) reviewed almost 400 studies on straying in Pacific salmon, including

the ones above on chum salmon, and found a small but measurable straying rate in almost every

study. They concluded that the average straying rate of adults released as smolts from the

hatchery where they had been reared was 2.6% across species. However, straying rates varied

widely under different conditions (such as site of release or life-history stage of fish at release).

Lister et al. (1981:39) concluded that “relatively large adult returns (of chum salmon) to sites

with hatchery facilities could result in increased straying to nearby streams. This pattern was

evident from chum salmon marking studies conducted to evaluate hatchery operations.”

In Washington, Eames et al. (1981, 1983) tagged adult chum salmon in 1976 and 1977 in

northern Puget Sound near Port Gardner, Bellingham Bay, and Skagit Bay. However, the

primary purpose of these studies was to estimate run-size, not straying. In this study, “strays”

were defined as “tagged fish which moved to other river systems or which were taken in the
65

various [out of basin or nonreported] fisheries” (Eames et al. 1981:147). However, the fish

tagged in this study were caught in the estuary, and it is unlikely that all the fish tagged were

native to the drainage. With these caveats, the researchers estimated straying rates between 6.9%

and 63.2% for the fish in their study.

Also in Washington, observations by WDFW biologists (Fuss and Hopley 1991), during

a study of five consecutive broods of coded-wire tagged chum salmon released from the Hood

Canal Hatchery, revealed very few stray fish in streams located in Hood Canal.

Other observations have shown that chum salmon periodically appeared in some southern

Oregon and California streams, with few if any known chum salmon spawning at locations

nearby (Moyle et al. in press). It therefore appears that chum salmon either stray thousands of

kilometers from the nearest spawning areas in some years, or they maintain spawning

populations in California and southern Oregon in areas that have been poorly surveyed.

Genetic studies on straying—Bams (1976) published a study on pink salmon that suggested

impaired homing in transplanted fish and in hybrids between populations. This hypothesis was

tested with chum salmon by Smoker and Thrower (1995). For two years they crossed fish from

two populations of chum salmon, tagged the offspring with coded microwire tags, and released

about 20,000 age-0 fry per year from control and treatment groups up to 65 km from their natal

streams (Table 8). Recoveries were monitored for 3 years per brood year. None of the 611

tagged fish that were recovered strayed from the native (non-hybridized) group, and only one

stray was recovered from the hybridized group. Although the number of fish released was small,

the results support the hypothesis that straying rates for native and transplanted hatchery chum

salmon are not necessarily great.

However, even small straying rates from large hatchery releases may result in a high

proportion of hatchery fish in small, natural populations. This can substantially affect natural

populations, particularly if the stray fish are of non-native origin. (Jacobs 1988, Thorpe 1994).

Many small populations of summer-run chum salmon in southeast Alaska have escapements of

less than 5,000 adults, and hatchery programs in some areas (see “Artificial Propagation,” p.

108) have released more than 100 million fry per year, producing returns approaching 1 million

fish per year. In recent years, otolith marking has been used on many of these hatchery releases,

with extensive monitoring of local wild populations for hatchery-marked fish. While no results

have yet been published, early returns indicate that only a small proportion of the total return of

hatchery fish is straying into local streams, although strays may represent up to 50% of the fish

in some of these streams (Thrower19).

19 Frank P. Thrower, NMFS Auke Bay Laboratory, 11305 Glacier Highway, Juneau, Alaska 99801-8626.

Pers. commun., November 1995.
66

Spawning behavior

In freshwater, a variety of population-specific reproductive behaviors have been

described for chum salmon in Asia (e.g., Sano and Nagasawa 1958) and North America (e.g.,

Johnson et al. 1971; Tautz and Groot 1975; Duker 1977, 1982; Helle 1981; and Schroder 1973,

1982) that may act to isolate populations. For example, Duker (1982) described a model for the

pre-spawning phase of courtship that involved mate recognition based on a variety of auditory,

tactile, and visual clues (e.g., species-specific body coloration, the black and white pigmentation

pattern inside the mouth) (Schroder 1981, Duker 1982). However, studies to determine whether

these behaviors or characteristics act to reproductively isolate particular populations or runs of

chum salmon from one another have not yet been made.

Spawning Ground and Redd Characteristics

There is extensive literature on selection of spawning sites and redd characteristics for

chum salmon (reviewed in Bakkala 1970, Smirnov 1975, Salo 1991), which indicates that under

specific circumstances chum salmon spawn in a wide variety of locations. In general, chum

salmon are reported to spawn in shallower, slower-running streams and side channels more

frequently than do other salmonid species, perhaps to avoid competition with pink salmon

(Bakkala 1971, Smirnov 1975, Salo 1991). In Asia, there are also extensive differences reported

between seasonal run types, with summer chum salmon reported to spawn in deeper waters and

higher velocities than fall chum salmon (Sano and Nagasawa 1958, Soin 1954, Smirnov 1975,

Salo 1991), even though Smirnov (1975:50) reported that the “autumn chum is larger than the

summer one and its redds are also larger.”

Smirnov (1975) suggests that the differences in physical parameters between the two run

times of chum salmon in the Russian Federation may be caused by interactions with pink

salmon. Fall chum salmon migrate farther inland than pink salmon, but summer chum and pink

salmon spawn in similar areas. Both species spawn within about 100 km of seawater, although

in most years, the spawning grounds of the two are widely separated: Summer chum salmon

spawn in the lower and middle reaches of rivers, whereas pink salmon usually migrate into the

upper reaches. But even in years when both pink and summer chum salmon are abundant, and

their spawning grounds are close together in the middle reaches, the two species maintain

separation by choosing different locations for their redds. Smirnov reported that in these

circumstances, summer chum, unlike pink salmon, spawn in deep, lower-velocity pools, away

from riffles and closer to river banks.

The velocity of water in spawning areas has been a widely studied area of research. In

the Amur River Basin, water velocities of 10-80 cm/sec were measured over summer chum

salmon spawning sites, and velocities of 10-30 cm/sec in riffles over fall chum salmon spawning

grounds. However, fall chum salmon also spawned in pools in this region where the velocity

was reported to be quite insignificant (Soin 1954, Smirnov 1975). On Hokkaido Island, Sano

and Nagasawa (1958) also found that fall chum salmon selected spawning areas with lower water

velocities (10-20 cm/sec) than did summer chum salmon in the Amur River area. These
67

differences in the physical characteristics of spawning areas may act to isolate populations or

runs in the same river (Salo 1991).

In Washington, Johnson et al. (1971) measured water velocities near 1,000 chum salmon

redds and found that velocities where fish spawned varied from 0.0 to 167.6 cm/sec and that over

80% of the fish spawned in velocities between 21.3 and 83.8 cm/sec. This range is similar to that

found in other species of salmon. For example, velocities of streams where chinook salmon

spawn are reported to range from 10 to 150 cm/sec. Johnson et al. (1971) also attempted to

correlate abundance indices of chum salmon in Washington with environmental variables such as

stream discharge, velocity, and surface water temperatures, but found no relationship between

run size and these variables. He concluded that he was unable to measure or to isolate the critical

areas in which environmental factors influence run size.

Subgravel flow (upwelled groundwater) may also be important in the choice of redd sites

by chum salmon. Salo (1991:240) reported that “chum salmon prefer to spawn immediately

above turbulent areas or where there was upwelling.” Sano (1966:46), in a summary of available

information on Far Eastern chum salmon, reported that throughout the Russian Federation and on

Hokkaido Island in Japan, autumn chum salmon “utilize mostly spring areas of upper tributaries,

[as] damage by freezing and other severe winter conditions is relatively minor in most years.”

However, Sano also notes (p. 46), based on studies by Smirnov in the 1940s, that “summer chum

salmon spawn earlier in the season, and they do not particularly choose spring areas.”

Smirnov (1975) noted that “the summer spawning chum from Kamchatka gravitates

towards the places of emergence of ground water” (p. 50) and that in the redds “of the summer

Amur and Sakhalin chum the eggs are mainly flushed by the so-called subterranean water,

replenished by the infiltrating streams water” (p. 49). Smirnov further noted that the summer

chum salmon in the Amur River area began to spawn from August to September during the

warmest time of the year when water temperatures fluctuated from 9.8 to 13.6°C. He reported

that incubation remained above 3°C through October and then dropped to zero.

Smirnov (1975:50) also noted that in many areas of the Russian Federation and on the

Islands of Hokkaido and Honshu in Japan, fall chum salmon reproduced in localities supplied

with groundwater even when temperatures did not go below freezing: “In limnocrenes, or

spring-fed spawning creeks on the basin of the Amur, the summer temperatures do not exceed

11-12°C; in the winter they fluctuate within the limit 2.5-5°C (on Hokkaido spawning grounds,

sometimes higher).”

Biologists at WDFW reported that chum salmon in Washington do not preferentially

choose areas of upwelling groundwater for redd construction; rather they suggest that chum

salmon in Washington “most commonly” use “areas at the head of riffles” (Crawford 1997:4).

As reported in Turner (1995) and repeated in Crawford (1997:4):

We [WDFW] are unaware of any evidence that Washington chum salmon specifically select

spawning sites with upwelling ground water. . .Washington chum salmon would not seem to need

this particular adaptation. Upwelling ground water would be an advantage for summer chum . . .
68

but most of the streams involved do not seem to match the definition of ‘streams with cool,

upwelling ground water.’ The summer chum streams of the Strait of Juan de Fuca and the Kitsap

Peninsula are characterized by low summer/fall flows and likely experience elevated stream

temperatures during the summer chum spawning period. In fact, a lack of ground water

influence may pose a particular problem for summer chum during periods of summer drought as

has occurred in western Washington in recent years. A more likely reason that summer chum

spawn where they do is the low flow condition of spawning streams at the time of return,

confining these fish to the lower reaches of the streams.

Fecundity and egg size

Fecundity and egg size of chum salmon have been extensively reported in the literature

(reviewed by Bakkala 1970 and Salo 1991); however, in most cases, comparative regional or

run-type information by age, size, or relative survival rates are lacking. Salo (1991:244)

considered fecundity data unreliable for comparison among regions and among runs, because it

was “not certain how representative the samples [were] for the reported geographical regions and

rivers of origin.”

Nevertheless, some latitudinal and run-type trends were evident for absolute fecundities

(number of eggs/female) and relative fecundities (number of eggs/cm of length) (Salo 1991).

One pronounced trend was that the ranges of absolute fecundity for both individual and annual

means were higher and larger among Asian chum salmon runs than among North American runs.

For example, individual fecundities from numerous studies, summarized by Salo (1991), varied

from about 900 to 8,000 eggs per female in Asian chum salmon, but only from 2,000 to 4,000

eggs per female in North American chum salmon. The annual mean of these fecundities ranged

from about 1,800 to 4,000 eggs per female in Asian chum salmon and from 2,000 to 3,600 eggs

per female in North American chum salmon. Differences also existed among northern and

southern populations in the two regions. Rivers in northern Asia had generally higher relative

fecundities than rivers in southern Asia. However, in North America the opposite was true:

Fall-run fish from southern rivers tended to have higher relative fecundities than fall-run fish

from northern rivers. The different regional trends are difficult to interpret because the various

studies were not always comparable. However, Salo (1991) suggested that differences may be

related to decreasing survival rates from south to north in Asia, and from north to south in North

America.

Fecundity differences between run times—Differences in both relative and absolute

fecundities have been extensively documented in fish with different run times (summer- and fallrun chum salmon) in the Amur River (Lovetskaya 1948; Birman 1951, 1956; Svetovidova 1961;

Sano 1966; Kulikova 1972), and to a lesser extent in the Yukon River (Andersen 1983, Trasky

1974) and in Hood Canal (Koski 1975). Summer-run chum salmon generally spawn within 100

km of the mouths of both the Amur and Yukon Rivers, whereas some stocks of fall-run fish

historically migrated hundreds of kilometers upriver to spawn. Interestingly, summer-run fish in

the Amur River have higher fecundities on average than do fall-run fish spawning in the lower

river, although in the Yukon River the opposite trend appears. However, the difference between

runs in the Yukon River is not large, and few data are available to compare fecundities between

the two run times (45.5 eggs/cm, N=23 for summer-run fish; and 41.2 eggs/cm, N=24 for fall-run
69

fish).

Fecundity and egg size for summer- and fall-run chum salmon in Hood Canal were

measured in Big Beef Creek by Koski (1975) in 1967-69. He found that summer- or early-run

females were smaller for a given age than in late-run fish (males were of similar size), but earlyrun fish had slightly larger fecundities per body length and per weight. Early-run fish had on

average 50 eggs per cm of body length compared to 46 eggs/cm in fall-run fish. Early-run fish

also averaged about 526 g less than later-returning fish, but had about 100 more eggs. Koski also

found that early-run fish had larger eggs than late-returning fish of the same body size.

Incubation and time of emergence

The rates of chum salmon embryonic and juvenile development tend to decline at high

latitudes in both Asia and North America, but vary among populations within an area, apparently

because of adaptation to local environmental conditions (e.g., summer-, fall-, and winter-run

chum salmon in southern Puget Sound or Hood Canal) (Bakkala 1970, Salo 1991). One of the

earliest detectable differences between chum salmon in different areas is the time of hatching of

eggs and the emergence of alevins from gravel. Differences between areas are caused by

physical factors such as stream flow, water temperature, dissolved oxygen, and gravel

composition, and by such biotic factors as genetics, spawning time, and spawning density, all of

which can affect survival (reviewed in Bakkala 1970, Salo 1991).

The rate of embryonic development in chum salmon is influenced most by water

temperature (reviewed in Bakkala 1970, Koski 1975, Salo 1991). The amount of heat, measured

in thermal units (TUs), required by fertilized chum salmon eggs to develop and hatch is about

400-600 TUs, and the heat required to complete yolk absorption is about 700-1,000 TUs. Lower

water temperatures can prolong the time required from fertilization to hatching by 1.5-4.5

months. For example, fertilized eggs hatch in about 100-150 days (400-600 TUs) at 4°C, but

hatch in only 26-40 days at 15°C.

The time to hatching also varies among populations and among individuals within a

population (Salo 1991). Koski (1975) found differences in the time to hatching between earlyand late-returning chum salmon at Big Beef Creek, a tributary to Hood Canal. For 2 years

(1968-1969 and 1969-1970), early-returning (peak September) and late-returning (peak late

November or December) fish spawned and their offspring were reared in spawning channels in

the creek. Fry emerged from February to June, but the timing of fry emergence differed between

early- and late-returning fish by an average of 35 days each year. Early-run fish took longer to

hatch, and this difference between the two runs was consistent from year to year. However, the

longer hatching time of early-returning spawners led to fry with lower average weight and less

lipid content than fry of late-returning spawners. Lower weight and fewer food reserves in early20 Thermal or temperature units (TUs) are the average number of degrees above 0°C during a 24-hour

period.
70

return fry may decrease their chances of survival during early life history. The difference in

incubation times for eggs from these early- and late-returning fish suggested a genetic difference

between the two runs, and Koski (1975) concluded that natural selection apparently acted on

hatching times: Fry tended to emerge when they had their best chances of surviving in streams

and estuaries.

Changes in hatching times due to adaptation to cold water have also been found for chum

salmon in the Susitna River, Alaska (Wangaard and Burger 1983) and in the Amur River in Asia

(Disler 1954, cited in Bakkala 1970). In these populations, low incubation temperatures resulted

in faster embryonic development than for embryos in other populations at the same temperature.

In Canada, however, Beacham and Murray (1986) failed to find differences in hatching times

among eggs from adults with early, middle, and late spawning times that had been incubated at

constant temperatures of 4, 8, and 12°C. Nevertheless, the time of emergence in that study

depended on the timing of spawning: Earlier-spawning fish laid larger eggs that took longer to

develop than did smaller eggs from later-spawning fish.

Other factors, such as dissolved oxygen, gravel size, salinity, nutritional condition, and

even the behavior of alevins in the gravel, can also influence the time to hatching, emergence

from the gravel, or both (reviewed in Bakkala 1970, Schroder et al. 1974, Schroder 1977, Salo

1991). For example, Fast and Stober (1984) found that developing chum salmon embryos in

small coastal streams required less oxygen than had been reported for either coho salmon (O.

kisutch) or steelhead (O. mykiss), but it is unknown to what extent chum salmon in different

areas vary in their oxygen requirements. The relative importance of various factors influencing

early development in different populations has not been evaluated.

However, despite a large amount of variability in incubation environments, even over

short distances, chum salmon display a variety of developmental responses that result in similar

emergence and outmigration times among fry within an area. Variability in some of these

responses appears to reflect differences among individual fish, but it also reflects differences

among populations in adult run and spawning times, egg size, and temperature-development

requirements.

Downstream movement

Observations of chum salmon fry are often more difficult to make than are observations

of juveniles of other salmonids because chum salmon outmigrants 1) are smaller than

outmigrants of other salmonids, 2) migrate at night, 3) usually have shorter distances to migrate

to reach saltwater than do other species, and 4) do not school as tightly as some other salmonids

(e.g., pink and sockeye fry) (Salo and Bayliff 1958, Beall 1972, Koski 1975, Seiler et al. 1981,

and reviewed in Salo 1991). Moreover, some chum salmon fry outmigrate in conditions less

conducive to scientific observation. For example, observation of outmigrating chum salmon fry

in northern Russian rivers draining into the Arctic Ocean is obscured by ice on the rivers at that

time of year (Sano 1966, 1967).
71

Nonetheless, several key facets of fry outmigration are known (Table 9). Downstream

migration may take only a few hours or days in rivers where spawning sites are close to the

mouth of the river, or it may take several months, as in the Yukon and Amur Rivers, where

spawning sites are located hundreds of kilometers upriver. The timing of outmigration is usually

associated with increasing day length, warming of estuarine waters, and high densities of

plankton (Walters et al. 1978). Juvenile chum salmon at southern localities, such as those in

Washington and southern British Columbia, migrate downstream earlier (late January through

May) than do fry in northern British Columbia and southeastern Alaska (April to June) (Table 9).

In the Yukon and Noatak Rivers in northern Alaska, chum salmon fry migrate

downstream beginning in late May, with the breakup of river ice. Outmigration continues until

fall, with peak movement in June and July (Martin et al. 1986) (Table 9). However, several

exceptions to this general pattern can be found. For example, Koerner (1993) reported that in

Fish Creek, a tributary of the Salmon River near Hyder, Alaska, chum salmon fry outmigrated

over an extended period from late February through May. Chum salmon in this creek also

spawned over an extended period from mid-June through October, which may have contributed

to the long period of emergence from the gravel and outmigration (Helle, footnote 14).

Several cues influence the timing of downstream migration, resulting in considerable

variability in migration timing. These cues include time of adult spawning, stream temperatures

during egg incubation and after hatching, fry size and nutritional condition, population density,

food availability, stream discharge volume and turbidity, physiological changes in the fry, tidal

cycles, and day length (Simenstad et al. 1982, Salo 1991). In the Russian Federation, Soldatov

(1912, cited in Smirnov 1975) found that chum salmon outmigrations did not always

immediately follow emergence; juveniles in many rivers remained up to 3-4 months in the river

and grew to a considerable size before outmigration (Kostarev 1970, as cited in Salo 1991). In

Washington, chum may reside in freshwater for as long as a month (Salo and Noble 1953,

Bostick 1955, Beall 1972). Juvenile residence times in freshwater longer than a month have also

been reported in the mainstems of the Skagit (Dames and Moore 1976) and Nooksack (Tyler

1964) Rivers.

Estuarine Life History

Chum salmon juveniles, like other anadromous salmonids, use estuaries to feed before

beginning long-distance oceanic migrations. However, chum and ocean-type chinook salmon

usually have longer residence times in estuaries than do other anadromous salmonids (Dorcey et

al. 1978, Healey 1982).21 The period of estuarine residence appears to be the most critical phase

21 Healey (1982) found that chinook salmon (of all salmonid species) depend most on estuarine habitat,

since all chinook life-history types feed and grow for some time in estuaries (unlike stream-type fry,

ocean-type chinook fry move quickly to salt water after emerging and depend on estuaries for nursery

habitats). Lake-type sockeye and pink salmon depend on estuaries the least of anadromous salmonids.
72
73

in the life history of chum salmon and appears to play a major role in determining the size of the

subsequent adult run back to freshwater (Mazer and Shepard 1962, Bakkala 1970, Mathews and

Senn 1975, Fraser et al. 1978, Peterman 1978, Sakuramoto and Yamada 1980, Martin et al. 1986,

Healey 1982, Bax 1983a, Salo 1991). Bax (1983b) determined that the extent of juvenile

mortality within 4 days after a hatchery release into the Hood Canal estuary was 31-46%. The

most important determinant of estuarine survival may be the timing of entry into saltwater

because of the strong seasonality of plankton in estuaries (Gunsolus 1978, Helle 1979, Gallagher

1979, Simenstad and Salo 1982).

For these reasons, the estuarine life-history phase has been the most intensely studied

period of chum salmon early life history. In all countries with large chum salmon hatchery

programs, research has focused on determining the optimal size and time for release of juvenile

chum salmon to enhance adult returns. How changes in estuaries affect the use of estuaries by

chum salmon, and how such changes influence the time of seawater entry, run and spawn timing,

and growth and maturation, may be important in delimiting ESUs.

Smoltification

This term denotes the life-history stage in which juvenile salmonids lose their parr marks,

turn silvery, and migrate from freshwater into seawater. In summary, smoltification is perhaps

the most intensively studied aspect of salmonid life history. Groot et al. (1995) contains an

extensive review of both historical and recent studies on this process. Coho, stream-type

chinook, lake-type sockeye salmon, and steelhead have a distinct “smolt” stage that can be

identified visually among fry, parr, and fingerlings (Hoar 1958). Chum and pink salmon,

however, do not have clearly defined smolt stages, but are nonetheless capable of adapting to

seawater soon after emerging from gravel. Chum salmon also usually retain parr marks when

they first enter seawater. In Japan, chum salmon fry weighing less than 2 g maintained normal

levels of plasma sodium (Na+) when they moved from freshwater into seawater (Iwata 1982).

This ability, however, declines slightly with continued residence in freshwater. The capability of

chum salmon fry for early osmoregulation in seawater may be important for adult homing back

to natal streams. For example, hatchery coho salmon were 10 times less likely to stray within a

river system if they were released into the river as fingerlings rather than as smolts (McHenry

1981, cited in Lister et al. 1981).

Timing of entry into estuary

Chum salmon fry from various spawning populations and adult runs in a river system

tend to enter seawater at a similar time, one that maximizes their chance of survival. The most

critical factor for survival of fry within an estuary appears to be fish size (Healey 1982). Similar

entry timing into an estuary by fish from different rivers may be an adaptation to temporally

variable food resources because plankton abundance in estuaries is highly seasonal (Gunsolus

1978, Helle 1979, Gallagher 1979, Simenstad and Salo 1982). Walters et al. (1978) developed a

model of optimal timing for downstream migration and entry into estuaries to maximize early
74

marine survival. The parameters for this model included 1) zooplankton production, 2) diet and

growth of young salmon, 3) size-dependent survival, and 4) timing of fry outmigration into

saltwater. For juvenile chum salmon in the Fraser River estuary, this model demonstrated a close

correlation between timing of seawater entry and early chum salmon survival.

Duration of estuarine residence

Chum salmon juveniles of early-returning adults tend to enter estuaries before juveniles

of late-returning fish (Koski 1975). Unlike some other species—sockeye salmon, for example,

which move immediately into deep water after entering an estuary—chum salmon tend to remain

in shallow eelgrass beds or other productive areas within the estuary from January to July (Healy

1982). Residence times are known for only a few estuaries, even though residence timing has

been studied since the 1940s (reviewed in Congleton 1979, Healey 1982, Simenstad et al. 1982,

Bax 1983a). Observed residence times range from 4 to 32 days, with a period of about 24 days

being the most common (Table 10).

Migratory patterns within estuaries

Migration patterns of juvenile chum salmon have been studied intensively in areas such

as Hood Canal by following marked juveniles from hatchery populations of fall-run chum

salmon and by monitoring outmigration (Bax 1982, 1983a,b; Bax et al. 1979, Bax et al. 1980;

Bax and Whitmus 1981; Schreiner 1977; Whitmus and Olsen 1979; Whitmus 1985; Salo et al.

1980). Some fry remain near the mouth of their natal river when they enter an estuary, but most

disperse within a few hours into tidal creeks and sloughs up to several kilometers from the mouth

of their natal river. In the Nanaimo and Fraser River estuaries, juveniles spend up to 3 weeks

feeding in the inner estuary, with little local movement (Healey 1979, Levy et al. 1979). Chum

salmon juveniles in the Nanaimo, Yaquina, Cowichan, and Courtenay estuaries are most

abundant in nearshore areas during April and May, but are most abundant in the outer estuary

during May and June (Myers 1980, Healey 1982).

Chum salmon fry show daily tidal migrations in the Fraser and Nanaimo Rivers, which

have large deltas and marshlands (Healey 1982). However, fry in Hood Canal have not been

observed to display daily tidal migrations (Bax 1983a), most likely because rivers entering Hood

Canal do not have extensive delta or tidal marsh systems (with the exceptions of the Quilcene

and Skokomish Rivers).

Although in general, movements of chum salmon fry in Hood Canal appear to follow a

pattern that depends on the time of release from hatcheries, release time is not the only causative

factor influencing migratory patterns (Bax 1982, 1983a). Chum salmon fry released into Hood

Canal in early February and March have spread out over a large area, but fish released in April

and early May tended to remain inshore initially, moving offshore in summer. These movements

were apparently associated with prey availability. Fish initially fed inshore on epibenthic

organisms, then offshore on plankton later in the season. Foraging success (growth), as well as
75
76

age, appeared to be the major factors in offshore movements of chum salmon juveniles in the

Strait of Georgia in early June and July (Healey 1980).

A seasonal change in the swimming speed of juvenile chum salmon was also observed in

Hood Canal (Bax 1982). In February and March, chum salmon fry (<40 mm fork length) usually

moved 8-14 km/day, but in May and June they moved 3-7 km/day. Fish released from the Hood

Canal Hatchery at Hoodsport in June took 3 weeks to arrive at the mouth of Hood Canal (Bangor

Annex), but arrived after only 1 week when released in April. However, this pattern may not be

consistent from year to year: Bax (1982) found that in 2 of the 3 years of a study (1977-1979),

average migration speed was lower in February than in March. Larger fish tended to move faster

than small fish, but the overall rate of movement decreased as the season progressed (Bax

1983a).

Larger fish also tended to move out of an area first when both large and small chum

salmon fry were simultaneously released from hatcheries on the Skokomish River in southern

Hood Canal (Bax and Whitmus 1981, Whitmus 1985). In southern British Columbia, larger fish

also tended to migrate offshore first, but by mid-July all chum salmon juveniles had left the

estuaries, regardless of size (Healey 1980). A similar timing of outmigration was observed in the

Yaquina River estuary in Oregon, except that most chum juveniles had moved out of the estuary

by mid-May (Myers 1980).

Reasons for the differences in movement patterns among areas are unclear. One reason

may be that genetically based physiological differences between runs produce different behavior

patterns (Whitmus 1985). Migration may be facilitated by both active swimming and passive

movement in currents, and seasonal changes in river discharge and surface flow in Hood Canal

may contribute to different migration patterns among populations (Bax 1982). The rate of

movement, especially early in the season, appears to be correlated with surface outflow in Hood

Canal (Bax 1982, 1983a). Movement of chum salmon juveniles apparently is also influenced by

the abundance of pink and chum salmon juveniles of the same size class in Hood Canal (Salo

1991).

Hood Canal fall-run chum salmon_Establishing riverine or estuarine residence times of

hatchery fall-run chum salmon is particularly important because of possible overlap with

summer-run chum salmon juveniles in Hood Canal. Chum salmon juveniles released from the

Hood Canal and Quilcene Hatcheries in Hood Canal showed little delay in their migration out of

Hood Canal, traveling in distinct groups past the Bangor Annex sampling site in the northern part

of Hood Canal (Whitmus 1985). However, some portion of large and small hatchery chum

salmon fry released at the same time from hatcheries in the southern part of Hood Canal resided

in the large Skokomish River delta region for up to 4 weeks (Whitmus 1985). Although the

hatchery fish released into southern Hood Canal were derived from the Hood Canal and Quilcene

hatcheries, they not only had longer residence times near their release site but failed to pass the

Bangor Annex as a distinct group (Whitmus 1985).
77

Hood Canal summer-run chum salmon—No experimental mark-and-release studies have been

conducted on natural or fall chum in Hood Canal, including summer-run chum salmon.

However, the outmigration of chum was monitored before the release of hatchery fish into Hood

Canal, and small peaks of outmigrants have been observed in February and March at sites on

both the east and west sides of Hood Canal (Bax et al. 1979, Bax et al. 1980, Bax 1982, 1983a).

Juveniles from early-spawning adults at Big Beef Creek were observed passing Bangor in Hood

Canal (Fig. 1) one week after peak outmigration from Big Beef Creek, but juveniles from laterun fish, which had emerged in April, took two weeks to cover the same distance (Bax 1982).

These differences were interpreted to result from differences in surface outflow in Hood Canal

rather than from any intrinsic behavior in the chum salmon juveniles (Bax 1982).

While these results indicate that summer-run chum salmon quickly migrate up the Canal

and into the main body of Puget Sound, preliminary data from ongoing snorkel and beach-seine

surveys by the U.S. Fish and Wildlife Service (USFWS) have revealed the presence of natural

chum salmon juveniles in Quilcene Bay, Hood Canal, from mid-January to mid-April (TaborCook et al.). These observations would suggest that either these fish emerge from streams over

an extended period or that juveniles remain in Quilcene Bay for several weeks. Washington

fisheries co-managers are currently conducting studies to clarify residence times and the timing

of juvenile migration for summer-run juveniles in Hood Canal (Tynan23).

Based on the time when summer-run chum salmon spawn, emergence of fry would be

expected at least a month prior to fall-run chum salmon emergence, but Koski (1975) found that

summer-run chum salmon in Big Beef Creek delayed embryonic development by an average of

12 days compared to the length of time it took fall-run chum salmon to emerge from the gravel.

However, in so doing, the fry apparently sacrificed their robustness (mass) and lipid reserves.

Therefore, if size at ocean entry is similar for all chum salmon (Peterman 1978), summer-run

chum salmon would be expected to spend more time in a nearshore estuarine environment, either

Hood Canal or the main body of Puget Sound, until they reached this optimal size (Salo 1991).

Japan—In Japan, prey availability may also influence the estuarine migration patterns of

juvenile chum salmon. The warm summer Oyashio Current off northern Japan moves inshore in

May and June, forcing cold-water oceanic plankton populations to move far offshore: Many fish

are then forced to move offshore also. Kaeriyama (1986, 1989) divided juvenile chum salmon

from this region into three groups: 1) “river” type, which remain in the river until they are large

enough to migrate offshore as the warm current approaches; 2) “foraging” type, which move into

offshore feeding areas in February and March before the warm currents arrive; and 3) “escape

22 C. Tabor-Cook, T. Kane, and D. Zajac, USFWS Western Washington Fisheries Resource Office, 2625

Parkmont Lane, Bld. A, Olympia, Washington 98502. Pers. commun., November 1995 and January

1996.

23 T. Tynan, Washington Department of Fish and Wildlife, P.O. Box 43151, Olympia, Washington 98504.

Pers. commun., June 1996.
78

foragers,” which migrate to low-salinity inshore and estuarine waters, where they feed until the

Oyashio Current retreats in June and July.

Growth and feeding in estuaries

Growth greatly influences the survival and migration timing of juvenile chum salmon.

Chum salmon grow rapidly in estuaries, and even though growth rates vary substantially between

areas, there are some consistent patterns. Salo et al. (1980) and Bax and Whitmus (1981)

measured growth of chum salmon fry in Hood Canal and found a daily gain of 5.7-8.6% body

mass, but found gains as high as 10.1% body mass in the first 4 days of estuarine residence.

Chum salmon in the Skagit River salt marsh grew 6% of their body mass per day (Congleton

1979, Congleton et al. 1982). Marked chum captured in the Nanaimo River estuary on

Vancouver Island also grew at about 5.7% of their body mass per day (Healey 1979), whereas

unmarked chum salmon in the Nitinat Lake (British Columbia) estuary grew only about 2.7%

body mass per day. However, Healey (1982) suggested this latter growth rate may have been

underestimated because larger fish migrated seaward from the lake. He suggested that the true

growth rate was closer to 3.5% body mass per day, but was still significantly less than the growth

rates in the Nanaimo estuary.

In some areas, such as the Fraser River estuary, chum salmon fry captured high in the

estuarine marshes were smaller than those captured in other estuaries (Levy and Northcote 1981),

but the fry were larger farther seaward in the Fraser River (Goodman 1975). Fry also increased

in size more slowly in the Squamish (British Columbia) and Yaquina (Oregon) River estuaries

than in the Nanaimo estuary (Levy and Levings 1978, Myers 1980). However, in all of the

above studies, chum salmon juveniles captured in estuaries were heavier than those captured in

rivers, and the difference increased with time. Also, while some fry remained for considerable

time in the inner estuary, all fry moved seaward by mid-May, with heavier fish migrating first.

Juvenile salmon, particularly chum and chinook, depend heavily on benthic organisms for

food in estuaries, but in outer areas they depend more on planktonic organisms. Detritus-based

food webs and juvenile chum salmon production in estuaries are closely linked (Sibert et al.

1978). In the 1970s and 1980s, chum salmon feeding and food-chain relationships were

examined in the above studies along with migrational timings of juveniles in fresh and estuarine

waters.

Simenstad et al. (1982) summarized the diets of juvenile salmonids in 16 estuaries and

concluded that small (#50-60 mm FL) juveniles of chum salmon fed primarily on such

epibenthic crustaceans as harpacticoid copepods, gammarid amphipods, and isopods, whereas

larger juveniles (>50-60 mm FL) in neritic habitats fed on drift insects and on such plankton as

calanoid copepods, larvaceans, and hyperiid amphipods. This diet is broader than that of

similarly sized pink salmon juveniles, which feed only on neritic zooplankton similar to those

consumed by large chum salmon juveniles, even in shallow sublittoral habitats (Healey 1982,

Simenstad et al. 1982). However, the early diet of juvenile chum salmon at some localities also

consists exclusively of neritic zooplankton.
79

Juvenile chum salmon in the Nanaimo River, British Columbia (Healey 1980) and in

Auke Bay, Alaska (Landingham 1982) fed only on harpacticoid copepods; but at other localities,

such as at some localities in the Skagit River (Congleton 1979) and in some estuaries of

Vancouver Island (Mason 1974), fry fed only on dipterans, primarily chironomids. Comparisons

between juvenile chum and chinook salmon in marsh habitats in the Fraser River estuary

indicated that the diet of chum salmon varied less from place to place than did the diets of

chinook salmon (Levy and Northcote 1981). Feeding preferences among juvenile salmon appear

to correlate with the degree to which a species depends on estuarine habitats (Healey 1982).

Chum salmon fry may exploit a greater variety of prey, because they can withstand greater

changes in salinity than other salmonids. For example, chum salmon fry in the Skagit River fed

on freshwater, estuarine, and marine organisms during a single tidal cycle (Congleton 1979).

Migration of chum salmon juveniles out of estuaries appears to be closely correlated with

prey availability. Chum salmon juveniles move offshore as they reach a size that allows them to

feed on the larger neritic plankton, and this movement normally occurs as inshore prey resources

decline (Salo 1991). This transition has taken place at 45-60 mm FL in Puget Sound and Hood

Canal, Washington (reviewed in Simenstad and Salo 1982, Salo 1991), but at 60 mm FL in

Prince William Sound, Alaska (Cooney et al. 1978).

Habitat utilization

Do different groups of chum salmon, or chum salmon compared to other salmon species,

use estuarine habitats differently? In the few studies published on this subject, juvenile chum

and pink salmon apparently occupy shallow sublittoral habitats before moving into neritic

habitats. They appear to remain in the shallow areas until they reach 45-60 mm FL, after which

they move into neritic habitats. Chum salmon apparently prefer exposed cobble or gravel

beaches in nearshore areas (Miller et al. 1977, 1980), especially within embayments. Chum

salmon also school in shallow habitats during daylight, but disperse into smaller groups at night

(Salo et al. 1980). Juveniles from most runs of chum salmon migrate in schools through northern

Puget Sound and into the Strait of Juan de Fuca (Fresh 1979). In contrast, juvenile coho salmon

move directly into neritic waters after entering an estuary and school much less than do pink and

chum salmon.

Interspecific interactions

Chum salmon interact with other salmonids in several ways (reviewed in Gallagher 1979,

Salo 1991). Most notable is the observation that returns from odd-year broods of chum salmon

in the Pacific Northwest and from even-year broods in Alaska tend to be lower when pink

salmon juveniles coexist with chum salmon juveniles in estuaries (Rounsefell and Kelez 1938,

Smirnov 1947, Lovetskaya 1948, Noble 1955). Ivankov and Andreyev (1971) modeled chum

salmon populations in southeastern Russia and found that when pink salmon juveniles were

abundant, predicted feeding and growth rates of juvenile chum salmon were lower. Ames (1983)
80

also hypothesized that competition for food and predation between pink and chum salmon

juveniles in estuary and nearshore marine habitats may cause distinct odd- and even-year cycles

in natural chum salmon populations in Puget Sound. The diets of pink and chum salmon in

Hood Canal overlapped up to 84% (Simenstad et al. 1980). Chum salmon diet also shifted in

years when pink salmon were abundant (Gallagher 1979), but this may have been due in part to a

more diverse diet in chum salmon juveniles than in pink salmon juveniles. Invertebrates not

eaten by pink salmon juveniles may be more available to chum salmon in years when pink

salmon are also abundant.

Culture techniques may also influence interactions between chum salmon juveniles and

other salmonids. Estuarine predation on natural and hatchery pink and chum salmon by larger,

piscivorous salmon—such as coho and chinook salmon smolts—may have caused declines in

some Puget Sound pink and chum salmon populations (Johnson 1973, Simenstad et al. 1982).

Freshwater and estuarine survival

Estimates of mortality of chum salmon in freshwater after emergence from the gravel

have been made by several authors, including Neave (1953) and Hunter (1959) in British

Columbia, Semko (1954) in the Russian Federation, and Beall (1972) and Fresh and Schroder

(1987) in Big Beef Creek, Washington. Although estimates of mortality in a study can vary

greatly (e.g., mortality varied from 5 to 60% in the study by Fresh and Schroder (1987)), the

average for all of the above studies was about 45%. Mortalities in natural habitats can be

influenced by such short-term physical factors as extreme cold, water diversions, and flooding.

Mortality is also affected by long-term factors such as the cumulative effects of habitat

degradation, climatic changes, and urbanization, and by biotic factors such as disease,

interspecific competition, bird and other predation, and the introduction of exotic predators and

competitors. Fish in most experimental studies are usually monitored in relatively stable

environments over a short period of time. Most of the above natural sources of mortality are

absent, and the only natural cause of mortality reported is usually predation. Nonetheless,

estimates of mortality under such experimental conditions can still be helpful for identifying

vulnerable life-history stages. Predation by juvenile coho salmon was the primary cause of

mortality to chum salmon in all the freshwater studies reviewed here. In Big Beef Creek on

Hood Canal, size selection of chum salmon juveniles by coho salmon was identified by Beall

(1972), but in a later study (Fresh and Schroder 1987) size selection by coho salmon and rainbow

trout was not observed.

Mortality of chum salmon juveniles, especially those from natural populations, is difficult

to estimate in estuaries. In studies on fluorescently marked juvenile chum salmon released from

the Enetai Hatchery in Hood Canal, Bax (1983a, b) estimated average daily mortalities between

31 and 46% over a 2- and 4-day period. In a study on releases of equal numbers of fish of two

different sizes, Whitmus (1985) estimated that small fish suffered higher mortalities than did

large fish. About 58% of the small fish died over 2 days, and of the fish remaining after 10 days

only 26% were small fish. This mortality was apparently due to predation by cutthroat trout and

marine birds. However, predator selectivity on fish size may have been due to the distribution of
81

the differently sized fish rather than to selective behavior: Large fish avoided predation in the

study area by emigrating out of the area sooner than small fish.

Juvenile offshore movement and residualism

It is unclear how long chum salmon juveniles remain in estuarine areas, but chum salmon

in the Washington and southern British Columbia generally entered the ocean earlier than did

more northern and western populations (Hartt 1980, Hartt and Dell 1986). In studies of juvenile

chum salmon (300-400 mm FL) captured and tagged in June in central Puget Sound, Jensen

(1956) found that juveniles moved northward to the Strait of Georgia and the west coast of

Vancouver Island shortly after release. They appeared to migrate northward along the coast in a

narrow band about 32 km in width. Hartt (1980) and Hartt and Dell (1986) summarized

available data on the distribution, migration, and growth of chum salmon in their first year at sea

and found that chum, pink and sockeye salmon juveniles tended to group together and remained

nearer shore (within 36 km) than juvenile coho and chinook salmon and steelhead. Later in the

season, pink salmon were extensively caught offshore by Canadian longline gear in November

and December, but no juvenile sockeye or chum salmon were caught in these offshore waters.

As groups of chum salmon reached Alaska, they moved offshore in a generally southwestern

direction, although movement was variable and appeared to be strongly influenced by currents

(Hartt 1980, Hartt and Dell 1986). A difficulty in these studies is that few numbers of tagged

fish were recovered. In the tag recoveries summaries by Hartt and Dell, over 110,000 juvenile

salmon and steelhead were caught and 35,259 tagged, of which 4,412 were chum salmon,

although only 6 chum salmon, or 0.1%, were recovered.

A second factor that obscures patterns of oceanic distribution and migration is the extent

of delayed ocean migrations and residualism by chum salmon. In the tagging studies by Jensen

(1956) juvenile chum salmon remained in nearshore waters beyond the usual time of ocean

migration, although the extent of this residualism was unclear (Jensen 1956, Hartt 1980, Fresh et

al. 1980, Hartt and Dell 1986). Not all of the chum salmon juveniles tagged in Hood Canal and

Puget Sound moved northward toward British Columbia; some remained in Puget Sound

throughout the summer, perhaps not leaving until the next spring (Jensen 1956). In November,

Hartt and Dell (1986) found juvenile chum salmon in central Puget Sound and in Hecate Strait

that averaged 230 mm in length, an indication of good growth. It has been hypothesized that

these fish may not make an extended northwest migration along the British Columbia/Alaska

coast, but may instead proceed directly offshore into the north Pacific Ocean (Hartt and Dell

1986).

Marine Life History

Marine migration patterns

Oceanic distributions of salmonids have been used to differentiate salmonid populations

for ESA considerations (Waples et al. 1991, Weitkamp et al. 1995). The International North
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Pacific Fisheries Commission (INPFC) has collected a large amount of information since 1952

on the distributions and origins of high-seas chum salmon. Studies by the INPFC have focused

on tagging experiments and scale pattern analysis (see Davis et al. 1990), and more recently on

mixed-stock identification (MSI) (see Winans et al. 1994). There have also been several regional

studies on the identification of high-seas chum salmon. These studies have used a variety of

techniques including gonad development, scale characteristics, age, morphology, allozyme

patterns, mtDNA variation, and DNA fingerprinting (e.g., Altukhov et al. 1980, Okazaki 1986,

Nikolaeva 1987, Ishida et al. 1989, Park et al. 1993, Taylor et al. 1994). However, until recently,

these studies focused on estimating the continent of origin for chum salmon, and little

information has been developed on the distributions of specific regional populations.

Tagging and scale studies by the INPFC showed that although chum salmon from both

Asia and North America are distributed throughout the North Pacific Ocean and Bering Sea,

Asian chum salmon apparently migrate farther across the Pacific Ocean than do North American

fish. Neave et al. (1976) reported that North American chum salmon were rarely found west of

the mid-Pacific Ocean (beyond long. 175°E), whereas Asian chum salmon were routinely

encountered far east of this line. Asian chum salmon have extended their distribution in recent

years into the central and eastern North Pacific Ocean, perhaps because of the large increase in

releases of hatchery fish in Japan (Kaeriyama 1989, Salo 1991), and because of the change from

high-sea to inshore fisheries by Japan’s fishing industry (Kaeriyama 1989, Ogura and Ito 1994).

Bigler and Helle (1994) and Helle and Hoffman (1995) suggested that the overlap of continental

groups may be detrimental to North American chum salmon because maturing chum salmon in

the North Pacific Ocean may be at or above carrying capacity.

Limited information exists on stock- or population-specific migrational patterns, and

distributions of chum salmon during their oceanic phase are limited. Maturing chum salmon in

the North Pacific begin to move coastward in May and June and enter coastal waters from June

to November (Neave et al. 1976, Fredin et al. 1977, Hartt 1980). No region-specific information

on chum salmon migrations to Washington and Oregon has been reported. Whether the large

populations of chum salmon that once inhabited the Columbia River (Rich 1942) and Tillamook

basins (Henry 1953, 1954) had oceanic distributions similar to Puget Sound chum salmon is

unknown. As landings in coastal Oregon historically excluded landings on the Oregon side of

the Columbia River (Henry 1953), one speculation is that these fish had a more southern

distribution, like the present distribution of Columbia River coho salmon (Sandercock 1991), and

may have returned northward along the Oregon coast as do some Columbia River coho salmon.

Age and growth

Age and growth in adult chum salmon have been extensively studied (reviewed in

Bakkala 1970 and Salo 1991). Although clear trends are difficult to detect because most studies

have relied on commercial catches of mixed stocks (Helle 1984), regional differences in growth

rate, age at maturity, and size at maturity are evident.

Growth rate—Asian chum salmon grow faster in the marine environment (higher instantaneous
83

growth rate) than do North American chum salmon. North American fish, however, are usually

larger at each stage of marine life. Salo (1991) suggested that the faster growth rate in Asian

chum salmon may be a genetic (bioenergetic) adaptation to poor habitat conditions in the western

Pacific Ocean. LaLanne (1971) and Ricker (1964) suggested that the growing season may be

longer for North American fish because scale analysis showed that growth began earlier and

ended later in the Gulf of Alaska than it did in Asian waters.

In general, average size for chum salmon of all ages increases from north to south, and

age at maturity decreases from north to south (reviewed in Salo 1991). This is attributed to the

longer growing season and earlier maturation of southern populations. However, Helle (1984)

demonstrated that in individual populations from the Noatak River in northern Alaska to

Whiskey Creek in central Oregon, 4-year males during the same year were largest in southern

southeast Alaskan mainland (Fish Creek at the head of Portland Canal) and decreased in size

both to the north and to the south. The average mass of chum salmon in Alaska was less than in

British Columbia, but the average sizes of chum salmon in northern British Columbia did not

differ significantly from average sizes in southern British Columbia (Ricker 1980). The greater

number of 3-year-old fish in southern catches and greater variability in fish age in northern

British Columbia may explain these results (Ricker 1980). Four-year-old chum salmon were

longer in northern Puget Sound (average 78.3 cm FL in 1964, and 75.7 cm FL in 1970) than in

the southern Puget Sound (from Discovery Bay to Tacoma) (average 74.3 cm FL in 1963-1966

and 72.4 cm FL in 1970) (Pratt 1974).

Age at maturity—Age at maturity also appears to follow a latitudinal trend in which a greater

number of older fish occur in the northern portion of the species’ range. Age at maturity has

been investigated in many studies, and in both Asia and North America, it appears that most

chum salmon (95%) mature between 3 and 5 years of age, with 60-90% of the fish maturing at 4

years of age. However, there is a higher proportion of 5-year-old fish in the north, and a higher

proportion of 3-year-old fish in the south (southern British Columbia, Washington, Oregon)

(Gilbert 1922, Marr 1943, Pritchard 1943, Kobayashi 1961, Oakley 1966, Sano 1966). Helle

(1979) has shown that the average age at maturity in Alaska is negatively correlated with growth

during the second year of marine life, but not with growth in the first year, and that age at

maturity is negatively correlated with year-class strength. A few populations of chum salmon

also show an alternation of dominance between 3- to 4-year-old fish, usually in the presence of

dominant year classes of pink salmon (Gallagher 1979).

Differences in age at maturity might be expected between summer and fall chum salmon

in such rivers as the Yukon and Amur, where distinct differences in the life history of the runs

occur. However, Buklis and Barton (1984) found little difference in the age at return for Yukon

River summer-run and fall-run chum salmon in commercial catches between 1973 and 1983.

Four-year-old fish made up 72.7% of the fall-run fish and 70.5% of the summer-run fish; age-5

fish were next most abundant, followed by age-3 and age-6 fish. An important consideration in

all studies of age composition is the large year-to-year variation common to all large data sets on

chum salmon.

Several authors have shown that the fluctuations observed in age composition are
84

explained by differences in abundances between brood years (Helle 1979, Buklis and Barton

1984). For example, in Olsen Creek, Prince William Sound, Alaska, 62% of the male chum

salmon from the 1956 brood came back as 3-year olds in 1959 (Helle 1979). The 1971 brood

produced the next largest percentage (32%) of 3-year-old males during the 20-year study. The

percentage of production of 3-year-old males ranged from 0 to 62%. Production of 4-year-old

males from the 1956-1972 brood years ranged from 33 to 94%. Production of 5-year-old males

from 1956-72 brood years ranged from 1 to 64% (Helle 1979). On the Amur River in the

Russian Federation, Lovetskaya (1948) reported data collected in the late 1920s and early 1930s

on age at maturity for summer-run and fall-run fish, and found that 4-year-old fish made up

73.0% of the summer-run and 68.6% of the fall-run chum salmon. However, age structure varied

widely between years. Only 26.6% of the summer-run fish in 1929 were 4-year-old fish, but

98.1% in 1930 were 4-year-old fish. No data are available for fall-run fish in 1930, although

73.7% in 1929 were 4-year-old fish.

Adult chum salmon have been decreasing in size since the early 1980s (Fig. 12). Helle

and Hoffman (1995) found that the average mass of 4-year-old fall chum salmon returning to the

Quilcene National Fish Hatchery on the Quilcene River in Hood Canal, Washington and to Fish

Creek at the head of Portland Canal in Southeast Alaska declined about 46% between the early

1970s and early 1990s (Helle footnote 14). The average age at maturity for fish at both localities

has also increased as size has decreased. Helle and Hoffman (In press) added four more years

(1993-96) of data on size changes in chum salmon to their previously published data set from

Fish Creek (1972-92) in southern southeast Alaska and Quilcene National Fish Hatchery (1973-

92) on the Quilcene River in Hood Canal in Washington (Helle and Hoffman 1995) (Fig. 12).

These new data on size changes in chum salmon show an abrupt significant increase in mean

length in 1995 and 1996 at Fish Creek and a significant increase in mean length for chum salmon

at Quilcene National Fish Hatchery in 1994, 1995 and 1996. Because population abundance of

chum salmon in both Asia and North America increased during these years, the authors suggest

that the climate regime of the North Pacific Ocean may be undergoing another change (Helle and

Hoffman In press).

Earlier, Bigler et al. (1996) examined mean length and mass of chum salmon captured in

commercial fisheries throughout North America from 1970 to the early 1990s, and most of the

catches showed declines in size. In addition, Japanese and Russian chum salmon have declined

in average size and have increased in average age at maturity during the past 15 years (Ishida et

al. 1993). The similarity of changes in size and age of chum salmon in North America, as well

as in Asia, suggests that these changes are the result of one or more factors in the ocean

experience of chum salmon.

A major change in ocean climate in the North Pacific Ocean occurred during 1976-77

(McLain 1984, Miller et al. 1994). Sea surface temperatures cooled in the central North Pacific

Ocean and warmed along the coast of North America. These conditions continued through the

mid-1990s. Although these oceanic changes enhanced survival and increased abundance,

particularly in Alaska and Asia, the relationship of these changes to the decline in size is

uncertain. The declining size and older age at maturity may be the result of density-dependent
85
86

factors (see Kaeriyama 1989, Ishida et al. 1993, Helle and Hoffman 1995, Bigler et al. 1996).

Density-dependent growth of salmonids in the ocean is complex and poorly understood (see

Peterman 1978, Rogers 1980, Peterman and Wong 1984).

Significance of Life-History Information for ESU Determinations

Life-history characteristics are complex attributes of biological organisms, derived from

the interaction of genetic and environmental influences. They may reveal population-specific

differences among local populations, useful in the identification of ESUs, although life-history

differences are often obscured by regional trends, environmental perturbations, and selective

sampling. In the BRT’s review of chum salmon life-history traits, only run timing appeared to

be important in defining ESUs, especially for populations of summer-run and winter-run chum

salmon, which show unusual run timings.

Chum salmon show several distinct run-timing patterns: 1) In both Asia and North

America, there is a bimodal distribution in return timing, with an early or summer peak and a late

or fall peak; 2) these seasonal peaks of returning fish appear to follow a north-to-south cline,

from earlier to later spawning times; 3) populations with early run times are common in Alaska

and in northern British Columbia, but are rare farther south; and 4) south of southeast Alaska

there is a distinct break between natural summer-run and fall-run chum salmon.

Genetics of Chum Salmon

In this section we consider the genetic evidence for reproductive isolation between

populations or groups of populations. Allele-frequency differentiation among populations and

differences in levels of gene diversity constitute the bulk of this evidence. Populations of chum

salmon have been examined for genetic variability throughout most of their geographical range

around the North Pacific Rim. Most of these studies were made with protein electrophoresis, but

recent studies have also used the analysis of mitochondrial DNA (mtDNA) and VNTR (variable

number of tandom repeats) microsatellite DNA.

One approach to detecting reproductive isolation is to compare frequencies of protein

variants (allozymes) among samples with a contingency-table analysis and the chi-square

statistic or the G-statistic (log likelihood ratio statistic). The finding of significant frequency

differences between groups can be taken as evidence of reproductive isolation. Another

approach to identifying reproductively isolated groups is to analyze genetic distances between

samples with such clustering methods as the unweighted pair groups method with averages

(UPGMA) (Sneath and Sokal 1973) or multidimensional scaling (MDS) (Kruskal 1964). The

UPGMA method is appropriate for analyzing populations of species such as salmon that largely

have hierarchical genetic population structure, with large geographical groups divided into

subgroups. However, when genetic variability varies continuously, as in a cline, or when

geographically intermediate populations are also genetically intermediate between groups, MDS

more accurately depicts relationships among samples than does agglomerative clustering such as
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the UPGMA (Lessa 1990). MDS is a nonmetric ordination of samples in two or three

dimensions that represents dissimilarity among samples. Principle component analysis (PCA) of

allelic frequencies can also be used to examine genetic relationships among populations. The

results of PCA analysis are usually similar to the results of MDS analysis for a set of data.

Several genetic distance measures (e.g., Cavalli-Sforza and Edwards 1967; Rogers 1972;

Nei 1972, 1978) have been used to study the population genetic structure of chum salmon, as

well as other salmonids. It is unclear, however, which measure is best. An attractive feature of

Rogers’ and Cavalli-Sforza and Edwards’ distances is that they are metrics and satisfy the

triangle inequality: Given three populations (A, B, C), the sum of the distances between A and B

and between B and C is greater than or equal to the distance between A and C. Nei’s (1972,

1978) distances sometimes distort genetic distance so that the triangle inequality is not met. On

the other hand, Cavalli-Sforza and Edwards’ and Rogers’ genetic distances do not use a

correction for sample size; thus distances are biased upward, especially for small sample sizes

(Nei 1978). In contrast, Nei’s (1978) distance is unbiased.

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. Sample sizes much less than 50 individuals may inflate estimates of genetic

distance between populations, because of the increased error in estimating allele frequencies. An

unbiased statistic is therefore more desirable. However, when genetic distances between

populations are also small, as they often are between populations of salmon, 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 Nei’s (1972, 1978) and Rogers’ (1972a) distance measures

can be influenced by different levels of heterozygosity between populations, whereas

Cavalli-Sforza and Edwards’ (1967) measure cannot. Discussions of these and other features of

genetic distances appear in Nei (1978), Hillis et al. (1996), and Rogers (1991). Most of this

discussion has focused on the merits of the various measures for phylogenetic reconstruction

among species and higher taxa. No one has quantitatively evaluated the performances of these

distances in assessing genetic differentiation among populations of species like salmon, which

typically show small genetic distances between conspecific populations.

Since it is unclear which distance measure is “best” in any given application, we analyzed

each set of data with Nei’s unbiased (1978), Rogers’ (1972a), and Cavalli-Sforza and Edwards’

(1967) genetic distances to identify results that may not be robust to the distance measure used.

In most cases, the different genetic distance measures yielded results that were highly correlated.

For simplicity we report only results based on Cavalli-Sforza and Edwards’ distance measure.

This measure ranges from 0.0 (identity) to 1.0 (complete dissimilarity).

A gene diversity analysis (Nei 1973, Chakvaborty 1980) was used to apportion allelefrequency variability into its geographic or behavioral components for a regional data set. Most

genetic variability in salmonids occurs as genotypic difference among individuals within a

population. A smaller proportion is generally due to genetic differentiation between spawning
88

populations in rivers and streams that have been defined by geography or run timing. These

statistics facilitate comparisons among regions and may detect regional differences in gene flow

or the effects of hatchery strays on genetic population structure.

Several life-history characteristics in chum salmon may influence the population genetic

structure. Fish return to natal streams at 3-5 years of age and spawn as early as June in northern

areas and as late as March in southern areas. Overlapping generations of fish at spawning

localities tend to increase the effective size of a population in a river, decreasing the effects of

random-drift genetic variability within and between populations. Since chum salmon generally

do not migrate far into a river to spawn, less genetic differentiation might be expected relative to

other species of salmon which have more geographically isolated populations scattered

throughout a river system.

Regional Differentiation

A major east-west genetic subdivision of Pacific Rim chum salmon populations has been

detected in several studies. In an ocean-wide study, Okazaki (1983) found a major genetic

discontinuity between Asian and North American chum salmon; however, because his study

included only a few samples, he was not able to resolve the geographic boundaries of these

groups. Seeb et al. (1995) combined data for 200 populations around the Pacific Rim from

studies of Kondzela et al. (1994), Phelps et al. (1994), Seeb et al. (1995), Wilmot et al. (1994),

and Winans et al. (1994). In this data set, genetically homogeneous populations were pooled into

regional groups, and some alleles occurring at low frequencies were pooled with alleles with

similar electrophoretic mobilities. Analyses of Cavalli-Sforza and Edwards’ (1967) genetic

chord distances between samples resolved a large geographic subdivision among Pacific Rim

chum salmon populations, with the break occurring to the east (Wilmot et al. 1994, Seeb et al.

1995) of the break suggested by Okazaki (1983). The results of Seeb et al. (1995) indicated that

northwestern Alaskan populations were genetically more similar to Asian populations than they

were to populations on the Alaska Peninsula and those in central and southeastern Alaska.

The analysis of mini-satellite nuclear DNA genes, however, showed a different

geographical pattern of genetic subdivision. Taylor et al. (1994) examined variability for two

putative VNTR loci in 1,211 fish from 39 localities extending from Honshu Island, Japan to

southern British Columbia, including localities in the Russian Federation, the Yukon River, and

southeastern Alaska. A UPGMA cluster analysis of a generalized genetic distance based on band

frequencies pooled into 44 size classes showed three hierarchical groups in which the greatest

subdivision was between Japanese samples and the remaining samples, and the next lower

subdivision was between Russia/Yukon River samples and southeastern Alaska/British

Columbia samples. The differences in population structure suggested by allozymes and by

nuclear mini-satellite DNA may be due to the analysis of only two linked mini-satellite loci.

The analyses of nucleotide sequence variability in mitochondrial DNA by Park et al.

(1993) showed a pattern of regional differentiation similar to that indicated by the analysis of

mini-satellite DNA by Taylor et al. (1994). Park et al. (1993) found a lack of sequence
89

variability in the control region (D-loop) of mtDNA in 798 fish collected from 42 localities

extending across the Pacific Rim from Japan to Washington. However, they found restriction

fragment variability in polymerase chain reaction (PCR) amplified mtDNA fragments of the

NADH dehydrogenase gene that showed strong frequency differences across the Pacific Rim.

The largest frequency differences were between Japan and all other regions including the

Russian Federation, Alaska/Yukon, and British Columbia/Washington. The mean frequency of

this variant in Japan was 0.80, whereas its frequency in the other regions was 0.13 or less.

Asian Populations

On the Asian side of the North Pacific, Japanese and Russian populations constitute

genetically discrete geographic units. Winans et al. (1994) compared 17 Japanese populations on

Honshu and Hokkaido Islands with 12 Russian populations extending from the Okhotsk Sea in

the south to the Anadyr River in the north. Cluster analysis of Nei’s unbiased genetic distances

(Nei 1978) between samples and a principal component analysis (Winans et al. 1994) showed

that the Japanese and Russian chum were genetically distinct from one another, with an average

genetic distance of 0.006 for a sample of 62 isozyme loci. This genetic distance is near the low

end of the range typically found for conspecific populations (Thorpe 1982).

Ninety percent of chum salmon produced in Japan are raised in about 300 hatcheries

(Kaeriyama 1989) located on most of the rivers that historically had runs of chum salmon. In a

study of 43 populations on Hokkaido and Honshu Islands, Okazaki (1982a,b) reported genetic

subdivision between populations on the two islands and, to a lesser degree, between areas on

each island. We reexamined the published allelic frequencies with genetic distances and cluster

analyses and found no evidence of regional or local genetic groupings among Japanese

populations of chum salmon. Our gene-diversity analysis of these data indicated a small amount

of genetic differentiation among populations. Of the total genetic variability, 96% was contained

on average within populations, 3.1% was due to differences among populations within four

regions, 0.4% was due to differences between islands, and 0.5% was due to the average

difference between east and west coast populations on each island.

Winans et al. (1994) examined an overlapping set of 17 populations on Hokkaido and the

northern part of Honshu Island for geographic variability at 26 polymorphic loci. Their UPGMA

clustering of Nei’s genetic distance between populations for these data indicated that the greatest

amount of geographic differentiation was between east and west coast populations and not

between Hokkaido and Honshu Islands, as suggested by Okazaki (1982a,b).

Kijima and Fujio (1982) examined genetic relationships among populations of chum

salmon in Japan based on allele-frequency variability at six loci. They searched for correlations

between genetic distances and geographical distances between samples with four different

analyses of population groups delimited by different potential pathways of migration around

Hokkaido and Honshu. In the genetic-distance/geographical-distance comparisons, the

magnitude of genetic distances between pairs of populations increased for a separation of up to

600 km between the pairs of samples. Pairs of samples separated by more than 600 km showed
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no correlation between genetic distance and geographic distance. This was interpreted to

indicate that gene exchange between populations was largely limited to distances less than 600

km and that populations separated by more than 600 km were genetically independent of one

another.

In contrast to Japanese chum salmon populations, Russian populations appear to be

subdivided into two genetically distinct groups with a few genetic outliers. In a genetic study of

chum salmon collected at river mouths, Viktorovskii et al. (1986) found two large groups, one

located on the eastern Kamchatka Peninsula and the other on the western side of the Peninsula

and around the Sea of Okhotsk. The southernmost populations on Sakhalin Island and around

the Bay of Amur were genetic outliers. The results of Winans et al. (1994) generally confirmed

the existence of two large Russian populations. In that study, samples of chum salmon were

collected from 17 localities in the Russian Federation, extending from the Ola River on the

Okhotsk Sea in the south around the Kamchatka Peninsula to the Anadyr River in the north, and

were examined for variability at 35 loci. A UPGMA analysis of Nei’s unbiased genetic distance

produced four clusters that were geographically poorly resolved. Nonetheless, populations

around the Okhotsk Sea (mainland and western Kamchatka Peninsula) tended to be genetically

distinct from those of the eastern Kamchatka Peninsula.

North American Populations

Northwestern Alaska/Yukon—Chum salmon of northwestern Alaska and the Yukon River

exhibit diverse life-history patterns and run times. Some chum salmon, for example, migrate

2,000 miles up the Yukon River to spawn, whereas others spawn in the lower sections of the

Yukon River basin. In a study of Alaskan and Canadian chum salmon spawning in the Yukon

River and its tributaries, Beacham et al. (1988) examined 7 polymorphic loci in 10 populations,

including those spawning several hundred miles from the mouth of the Yukon River. They

found that fall-run fish of the upper Yukon River were genetically distinct from summer-run fish

in the lower Yukon River in northwestern Alaska. Other genetic studies (Seeb et al. 1995,

Wilmot et al. 1994) also confirmed major genetic differences between upper Yukon fall-run

chum salmon and summer-run chum salmon in the lower river. The large genetic differences

between these two groups of populations appear to reflect large differences in run times and large

geographic distances between spawning areas.

Wilmot et al. (1994) examined 24 polymorphic loci (plus 30 invariant loci) in 30 river

populations around Bristol Bay, in the Yukon River, and on the Alaska Peninsula. Three

samples from the Russian Federation were also included in this study. In a UPGMA and

neighbor-joining cluster analysis of chord genetic distances, they found three major clusters of

samples: 1) Russia-Alaska Peninsula samples, 2) Bristol Bay samples, and 3) upper and lower

Yukon River samples. A hierarchical gene-diversity analysis of allele-frequency variability

indicated that 95.4% of gene diversity was contained, on average, within populations, 1.4% was

due to allele-frequency differences among populations within regions, 0.5% to differences

between fall- and summer-spawning populations in the Yukon River, and 2.7% to differences

among areas within years.
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Southeastern Alaska/British Columbia—Kondzela et al. (1994) examined 42 variable loci

(plus 4 monomorphic loci) in 61 samples of chum salmon from populations in southeastern

Alaska and northern British Columbia. A neighbor-joining cluster analysis of chord distances

(based on 40 loci) showed four more or less distinct clusters of populations: 1) central

southeastern Alaska, 2) southern southeastern Alaska and north and central British Columbia, 3)

Prince of Wales Islands, and 4) Queen Charlotte Islands. A gene-diversity analysis of these data

indicated that 97% of the genetic diversity occurred as differences between individuals within

populations, 1.3% as allele-frequency differences among populations within regions, and 1.4% as

frequency differences among regions.

British Columbia—Beacham et al. (1987) studied allozyme variability for 9 polymorphic loci in

83 chum salmon populations in central and southern British Columbia. A UPGMA tree of Nei’s

unbiased genetic distance indicated five more or less distinct clusters of samples: 1) Queen

Charlotte Island samples, 2) north and central coast British Columbia samples, 3) east coast of

Vancouver Island and south coast of British Columbia samples, 4) west coast of Vancouver

Island samples, and 5) Fraser River samples. This study did not include samples outside British

Columbia, thus the relationships of these groups to chum salmon populations to the north in

Alaska or to the south in Washington are unclear. An analysis of geographic variability with the

fixation index (F

ST

) indicated that on average 97.7% of the total gene diversity was contained

within populations, and 2.3% was due to allele-frequency variability differences among

populations.

Washington/British Columbia—Phelps et al. (1994) examined genetic variability at 39

polymorphic loci in 153 samples from 105 locations in southern British Columbia, Washington,

and Oregon (Table 11). Five of 30 spawning localities examined for interannual variability

showed significant (P < 0.05) allele-frequency differences between or among years. Genetic

marking or hatchery transplantations could explain the temporal variability in three of these

populations, and temporal variability at two localities with small population sizes was probably

due to random genetic drift. Allelic frequencies were pooled over years for those populations

sampled in more than 1 year, except for the Samish Hatchery which had a recent history of

transfers that apparently have produced significant allele-frequency shifts among years.

A UPGMA tree of chord genetic distances consisted of clusters with samples from the

same geographical region or run-time. The most important result of this analysis was that

summer-run chum salmon in Hood Canal and the Strait of Juan de Fuca were distinct from

fall-run chum salmon in the same areas and from other fall- and summer-run populations. This

genetic distinction also appeared in the multidimensional scaling analysis of the chord distances.

Unlike Hood Canal and Strait of Juan de Fuca summer-run chum salmon, the summer-run chum

salmon of southern Puget Sound clustered with fall-run chum salmon of the same geographical

region.

Another important result was that among fall-run chum salmon, geographically close

populations were generally more similar genetically to one another than to widely separated
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populations. One exception was fall-run chum salmon in the Strait of Juan de Fuca and coastal

Washington and Oregon, which were more similar to Georgia Strait and west-coast Vancouver

Island populations than to populations in Puget Sound. Samples from two southern Puget Sound

winter-run populations were included in the study, and these two samples were genetic outliers

that were most closely related to samples of fall-run Hood Canal and northern Puget Sound

populations (Fig. 12).

Phelps24 (and Phelps 1995) added allele-frequency data for an additional 16 chum salmon

populations to the data of Phelps et al. (1994) and resolved three reasonably distinct clusters of

samples: 1) summer-run chum salmon of Hood Canal and Strait of Juan de Fuca, 2) Puget Sound

fall-run and southern Puget Sound winter- and summer-run chum salmon, and 3) Strait of Juan

de Fuca, coastal Washington, and Oregon fall-run chum salmon. Samples from British

Columbia were not included in this second analysis, but the previous results of Phelps et al.

(1994) indicated that group 3 was most closely related to Fraser River and Georgia Strait chum

salmon populations in British Columbia.

A gene-diversity analysis of the 105 populations sampled by Phelps et al. (1994) was

typical of that for other regions around the North Pacific and indicated that 97.17% of the total

diversity was contained within populations and that 2.83% was due to differences between

population differences and run-timing differences. Within run timings, 0.80% was due to

differences among populations, and 0.27% was due to regional differences. The calculation of

diversity within and between run timings was not straightforward, because southern Puget Sound

summer-run fish are genetically closer to Puget Sound fall-run fish than to summer-run fish in

Hood Canal and the Strait of Juan de Fuca. Summer-run fish in southern Puget Sound were

therefore excluded from the calculation of diversity among populations within a run timing,

which was 0.91%. The addition of southern Puget Sound fish represented 0.05% of the diversity,

and the diversity due to differences among run timings was 0.80%.

To develop a better perspective of regional genetic variability, we combined the

allele-frequency data of Phelps et al. (1994) with those of Phelps (footnote 26). The combined

data set included allelic frequencies for 34 loci in samples from 116 localities. Multidimensional

scaling in three dimensions of Cavalli-Sforza and Edwards (1967) chord distances (Fig. 13)

showed four groups of chum salmon: 1) summer-run populations in the Strait of Juan de Fuca

(nos. 108-110) and Hood Canal (111-116); 2) fall-, summer-, and winter- run chum salmon in

British Columbia (1-26) and Puget Sound (27-74) and fall-run fish in Hood Canal and the Strait

of Juan de Fuca (75-95); 3) all samples of chum salmon from outer coastal populations of

Washington and Oregon (96-104, 107); and 4) all samples of chum salmon from the Columbia

River (105-106).

To depict the genetic relationships among Washington and British Columbia populations,

we used multidimensional scaling in two dimensions of chord distances based on 34 loci (Fig.

24 S. Phelps, Washington Department of Fish and Wildlife, P.O. Box 43151, Olympia, Washington

98504. Pers. commun., July 1995.
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13). These populations consist largely of fall-run chum salmon, but also of genetically similar

winter- and summer-run chum salmon in Puget Sound. Several geographically meaningful

clusters appeared in the graph. Samples of fall-run chum salmon from southern Puget Sound

(nos. 47-74) and from Hood Canal, or fish of Hood Canal origin (75-89), formed a large cluster.

Three samples from Puget Sound summer-run chum salmon (69-72) and from two winter-run

populations (73-74) were included in the large Puget Sound cluster of samples. Two overlapping

clusters of samples from northern Puget Sound (27-46) and the Fraser River (17-26) were placed

next to the large southern Puget Sound-Hood Canal cluster. Clusters of samples from southern

British Columbia (12-16), eastern and southern Vancouver Island (4-11), and the Strait of Juan

de Fuca (92-95) populations overlapped with each other.

No clear genetic boundaries appeared between adjoining clusters, but more widely

separated populations generally showed larger genetic distance than did nearby populations.

West Vancouver Island populations (nos. 1-3) were placed in a distinct cluster separate from

other British Columbia populations. Samples from Washington and Oregon outer coastal

populations (96-104, 107) and Columbia River populations (105-106) formed two distinct

clusters, in which the nearest genetic neighbors of the Columbia River populations were among

the outer coast populations.

We further analyzed allelic frequencies of the fall-run chum salmon samples reported by

Phelps et al. (1994) with spatial autocorrelation to test for isolation by distance among

populations. The autocorrelation coefficient, Moran’s I (Cliff and Ord 1981), was calculated

between samples in 13 50-km distance classes for 19 independent alleles and presented as a

correlogram (Fig. 14, Table 12). Significant deviations of Moran’s I from zero were detected by

standard normal testing procedures following the methods described by Sokal and Oden (1978)

and Jumars et al. (1977). This statistic detects positive and negative correlations between sample

allelic frequencies within a distance class relative to the average allelic frequencies over all

samples.

The results for five alleles—sIDHP-2*86, sIDHP-2*36, sMDHA-1*100, sMDHB-1*100,

and mMEP-2*100—were typical of those for 14 other alleles and are shown in Figure 15. High

positive autocorrelation appeared between allelic frequencies in samples separated by less than

about 250 km. Populations separated by distances greater than 250 km do not, on average,

influence one another significantly through migration. The neighborhood size for chum salmon

populations in the Pacific Northwest is considerably less than the estimated 600 km reported for

Japanese chum salmon by Kijima and Fujio (1982), who estimated this parameter by regressing

genetic distances between populations on geographic distances. Larger neighborhood size for

Japanese populations could be due to the greater number of egg and fry transfers between

hatcheries. Among Pacific Northwest samples, significant negative autocorrelation appeared for

pairs of samples separated between 250 and 600+ km, except for significant positive

autocorrelation for 5 of the 19 alleles between pairs of samples from populations separated by

about 300-450 km. These unexpected positive autocorrelations between widely separated

populations may be due to genetic similarity from recolonization by the same ancestral

populations after deglaciation (McPhail and Lindsey 1986). Alternatively, they may result from
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long-distance straying induced by alternate migration around Vancouver Island (Beacham et al.

1987) or translocations of chum salmon eggs and fry (Phelps et al. 1994).

Within-Population Genetic Diversity

The amount of genetic variability in a population reflects the effects of past population

events, such as random genetic drift, the introduction of variability through immigration or

mutation, and natural selection. If the effects of mutation and natural selection on electrophoretic

variability are assumed to be minimal, reduction in genetic variability within a population may

be taken as an indication of past reductions in population size. Larger populations are less

subject to the loss of genetic variability through random genetic drift. For example, Kijima and

Fujio (1984) found a significant correlation (R = 0.40, P < 0.05) between average, direct-count

heterozygosity and population size in 37 river populations of chum salmon in Japan.

In a study of Asian chum salmon populations by Winans et al. (1994), gene diversities

(expected heterozygosities) in over 62 loci (including monomorphic loci) ranged from 0.066 to

0.087 among samples, averaging 0.079. However, no regional trends were apparent in the

geographical distributions of these values. Overall, this level of genetic variability represents a

large amount of genetic diversity relative to that found in other vertebrates (Ward et al. 1992).

For northwestern Alaska and Russian populations, Wilmot et al. (1994) estimated expected

heterozygosities from 54 loci and found values ranging from 0.056 to 0.072. Heterozygosities

averaged by Wilmot et al. (1994) over populations within regions were 0.064 among lower

Yukon River summer-run populations, 0.062 among upper Yukon River fall-run populations,

0.065 among Bristol Bay populations, 0.064 among Alaska Peninsula populations, and 0.063

among Russian populations. In 83 chum salmon populations in British Columbia, Beacham et

al. (1987) used 9 loci to estimate expected heterozygosities in 5 areas and found that populations

in the Fraser River and on the south coast of British Columbia tended to have smaller values.

However, population abundances, and presumably effective population sizes, are smaller in

northern areas, especially on Queen Charlotte Island, than in southern areas of British Columbia

(Beacham 1984). Since Beacham et al. (1987) used only 9 polymorphic loci, their

heterozygosity values cannot be compared directly to other studies that used 50 or more loci in

their estimates of heterozygosity.

Phelps et al. (1994) estimated population heterozygosity from direct counts of

heterozygotes in a set of data that included 38 polymorphic loci and that overlapped with the sets

of loci used by Beacham et al. (1987) and Winans et al. (1994). Since monomorphic loci were

not included in the estimates of Phelps et al. (1994), heterozygosities between the studies are not

directly comparable. Average heterozygosities varied among populations from 0.082 to 0.116

and did not deviate more than 0.005 from heterozygosities expected with random mating. The

highest heterozygosities occurred in Hood Canal fall-run chum salmon (0.108 on average) and

southern Puget Sound fall- and summer-run populations (0.102 on average). The lowest values

were found in the Strait of Juan de Fuca (0.090), Georgia Strait (0.090), and the west coast of

Vancouver Island (0.089) fall-run populations. Heterozygosities in hatchery populations were

nearly the same as heterozygosities in nearby wild populations. These results suggest that chum
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salmon hatchery populations in Washington have not experienced recent or historical bottlenecks

in population size.

Summary of Genetic Information

Allelic frequencies for a large number of protein-coding loci indicate that chum salmon

populations along the rim of the North Pacific are divided into several regional groups. Russian

and northwestern Alaska chum salmon appear to be more closely related to each other than either

is to Japanese chum salmon. Frequencies of a mitochondrial DNA variant and mini-satellite

DNA variants also show a major difference between Japanese chum salmon populations and all

other populations. In northwest Alaska, allozyme frequencies indicate that fall-run chum salmon

in the upper Yukon River are distinct from summer-run chum salmon in the lower Yukon River.

In the eastern North Pacific, populations of chum salmon from central Alaska to Washington

appear to be genetically isolated by distance, so that geographically proximate populations are

more closely related to one another than populations separated by large distances.

Two major genetic groups are present in central and southern British Columbia,

Washington, and Oregon. One consists of summer-run chum salmon in Hood Canal and the

Strait of Juan de Fuca, and a second large group consists of fall-, winter-, and summer-run chum

salmon in other areas. The second large group is weakly divided into two groups: 1) coastal

populations along the outer coast of Washington and Oregon, including those in the Columbia

River, and 2) the remaining populations in British Columbia and Washington (including the

Strait of Juan de Fuca populations). Levels of genetic variability within and between populations

in several geographic areas are similar, and populations in Washington show levels of genetic

subdivision which are typical of those seen between summer- and fall-run populations in other

areas and which are typical for populations within run types.

Discussion and Conclusion of ESU Determinations

Based on a review of the biology and ecology of chum salmon, the BRT identified four

ESUs for the species in the Pacific Northwest (Fig. 16). Genetic data (from protein

electrophoresis and DNA markers) were the primary evidence considered for reproductive

isolation criterion. This evidence was supplemented by inferences about barriers to migration

created by natural geographic features. Data considered important in evaluations of ecological/

genetic diversity included distributions, migrational and spawning timing, life history,

ichthyogeography, hydrology, and other environmental features of the habitat. In the following

summaries, we describe those factors that were valuable in making individual ESU

determinations.

Each of the ESUs include multiple spawning populations of chum salmon, and most

ESUs also extend over a considerable geographic area. This result is consistent with NMFS

species definition policy (Waples 1991:20), which states that in general, “ESUs should

correspond to more comprehensive units unless there is clear evidence that evolutionarily
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important differences exist between smaller population segments.” However, considerable

diversity in genetic or life-history traits or habitat features may exist within a single complex

ESU, and the descriptions below briefly summarize some of the notable types of diversity within

each ESU. This diversity is considered in the next section in evaluating risk to the ESU as a

whole.

Puget Sound/Strait of Georgia ESU

The Puget Sound/Strait of Georgia ESU (Figure 16) includes most U.S. populations of

chum salmon and the vast majority of adult spawners that return to U.S. waters outside Alaska.

This ESU includes all chum salmon populations from Puget Sound and the Strait of Juan de Fuca

as far west as the Elwha River, with the exception of summer-run populations in Hood Canal and

along the eastern Strait of Juan de Fuca. The BRT concluded that this ESU also includes

Canadian populations from streams draining into the Strait of Georgia. A northern boundary for

this ESU was tentatively identified as Johnstone Strait, but this determination was hampered by a

paucity of information from populations in central and northern British Columbia. Chum salmon

from the west coast of Vancouver Island are not considered part of this ESU, in part because

available genetic information suggests these fish are distinct from Puget Sound or Strait of

Georgia fish.

Genetic, ecological, and life-history information were the primary factors used to identify

this ESU. Environmental characteristics that may be important to chum salmon (e.g., water

temperature, and amount and timing of precipitation) generally show a strong north-south trend,

but no important differences were identified between Washington and British Columbia

populations. An east-west gradient separating Olympic Peninsula populations from those to the

east was considered to be more important for evaluating chum salmon populations.

Chum salmon populations within this ESU exhibit considerable diversity in life-history

features. For example, although the majority of populations in this ESU are considered to be

fall-run stocks (spawning from October to January), four summer-run (spawning from September

to November) and two winter-run (spawning from January to March) stocks are recognized by

state and tribal biologists in southern Puget Sound. Summer chum salmon in southern Puget

Sound are genetically much more similar to Puget Sound fall chum salmon than they are to other

summer-run populations in Hood Canal and the Strait of Juan de Fuca. These data suggest

relatively weak isolation between summer- and fall-run chum salmon in southern Puget Sound

and/or a relatively recent divergence of the two forms. Reproductive isolation of the Nisqually

River and Chambers Creek winter-run populations, which are the only populations in the ESU

whose spawning continues past January, may be somewhat stronger.

The Nisqually and Puyallup Rivers are also unique in southern Puget Sound because their

headwaters are fed by glaciers on Mount Rainier, giving the rivers different characteristics than

other regional river systems. The Nisqually population is also one of the more genetically

distinctive chum salmon populations in Puget Sound. However, the genetic differences are not

large in an absolute sense, and the majority of the BRT felt that the distinctiveness of the winter-
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run populations was not sufficient to designate these populations a separate ESU. Rather, the

team concluded that these populations, along with the summer-run populations in southern Puget

Sound, reflect patterns of diversity within a relatively large and complex ESU.

Hood Canal Summer-Run ESU

This ESU includes summer-run chum salmon populations in Hood Canal in Puget Sound

and in Discovery and Sequim Bays on the Strait of Juan de Fuca. It may also include summerrun fish in the Dungeness River, but the existence of that run is uncertain. Distinctive lifehistory and genetic traits were the most important factors in identifying this ESU.

Hood Canal summer-run chum salmon are defined in SASSI (WDF et al. 1993) as fish

that spawn from mid-September to mid-October. Fall-run chum salmon are defined as fish that

spawn from November through December or January. Run-timing data from as early as 1913

indicated temporal separation between summer and fall chum salmon in Hood Canal. Even

though for many years there have been hatchery releases of fall chum salmon in Hood Canal of

about 35 million fish annually, and many25 of these fish return to hatcheries in Hood Canal and

were historically spawned before the end of October, recent spawning surveys show that

temporal separation still exists between summer and fall chum salmon. Genetic data indicate

strong and long-standing reproductive isolation between chum salmon in this ESU and other

chum salmon populations in the United States and British Columbia. Hood Canal is also

geographically separated from other areas of Puget Sound, the Strait of Georgia, and the Pacific

Coast.

In general, summer-run chum salmon are most abundant in the northern part of the

species’ range, where they spawn in the main stems of rivers. Farther south, water temperatures

are so high and stream flows are often so low during late summer and early fall that conditions

become unfavorable for salmonids. River flows typically do not increase and water temperatures

do not decrease until the arrival of fall rains in late October/November. Presumably for these

reasons, few summer chum populations are recognized south of northern British Columbia.

Ecologically, summer-run chum salmon populations from Washington must return to freshwater

and spawn during peak periods of high water temperature, suggesting an adaptation to

specialized environmental conditions that allow this life-history strategy to persist in an

otherwise inhospitable environment. The BRT concluded, therefore, that these populations

contribute substantially to the ecological/genetic diversity of the species as a whole.

25 As described in Table 14, WDFW data from the 1960s to 1980 (NRC 1995) identify a total of about 1.5

million fall chum salmon spawned at Hood Canal hatcheries before November. From 1980 to 1987,

about 600,000 fish were spawned prior to November. In 1988 from 30 October to 5 November, about 2

million Finch Creek stock fall chum salmon were spwned. In recent years no fall chum salmon have

been spawned prior to October 30th at state, tribal or federal hatcheries in Hood Canal.
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Some chum salmon populations in the Puget Sound/Strait of Georgia ESU, which has

four recognized summer-run populations and two recognized winter-run populations, also exhibit

unusual run timing. However, allozyme data indicate that these populations are genetically

closely linked to nearby fall-run populations. Therefore, variation in run timing has presumably

evolved more than once in the southern part of the species’ range. Genetic data indicate that

summer-run populations from Hood Canal and the Strait of Juan de Fuca are part of a much more

ancient lineage than summer-run chum salmon in southern Puget Sound.

Pacific Coast ESU

This ESU includes all natural chum salmon populations from the Pacific coasts of

Washington and Oregon, as well as populations in the Strait of Juan de Fuca west of the Elwha

River. This ESU is loosely defined at present, and is defined primarily on the basis of lifehistory and genetic information. Allozyme data show that coastal populations form a coherent

group that show consistent differences between other fall-run populations in Washington and

British Columbia. Geographically, populations in this ESU are also isolated from most

populations in the Puget Sound/Strait of Georgia and Columbia River ESUs.

Ecologically, the western Olympic Peninsula and coastal areas inhabited by chum salmon

from this ESU experience a more severe drought in late summer and are far wetter during the

winter than areas in the Puget Sound/Strait of Georgia region. All chum salmon populations in

this ESU are considered to include fall-run fish. Some Oregon populations are the only known

locations to which 2-year-old adult chum salmon return with any appreciable frequency.

Chum salmon from this ESU cover a large and diverse geographic area—from the Strait

of Juan de Fuca (lat. 48°20 ́N) to at least southern Oregon—and the historic ESU may have

extended to the recorded extreme limit of the species’ distribution near Monterey, California (lat.

36°50 ́N). Many BRT members concluded that multiple ESUs of chum salmon may exist in this

area, but a more detailed evaluation was hampered by a scarcity of biological information of all

types. It is possible that many (perhaps most) reports of chum salmon in California and southern

Oregon do not represent permanent spawning populations, but rather episodic colonization from

northern populations. Even if this is the case, however, the southern limit to permanent natural

populations is unclear.

The boundary between this ESU and the Puget Sound/Strait of Georgia ESU is uncertain,

particularly with respect to fall chum salmon in the Dungeness and Elwha Rivers. Genetic data

for these two populations are ambiguous (Elwha—because of hatchery stocking) or nonexistent

(Dungeness), and run timing is also largely uninformative regarding the affinities of these two

populations. Although coastal populations generally return and spawn slightly earlier than those

in Puget Sound, there is little difference in run timing between Puget Sound and Strait of Juan de

Fuca populations. The Washington Department of Fish and Wildlife (Phelps et al. 1995)

considers the Dungeness and Elwha River populations to be affiliated with Strait of Juan de Fuca

populations to the west, primarily because of their geographic separation from inner Puget Sound

fall-run populations. However, the transition to the wetter, coastal climate occurs west of the
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Elwha and Dungeness Rivers on the Olympic Peninsula. After considerable discussion, the BRT

concluded, based on available information, that fall chum salmon from the Dungeness and Elwha

Rivers should be considered part of the Puget Sound/Strait of Georgia ESU.

Columbia River ESU

The BRT concluded that, historically, there was at least one ESU of chum salmon in the

Columbia River. Ecologically, Columbia River tributaries differ in several respects from most

coastal drainages. Genetic data are available only for two small Columbia River populations,

which differ substantially from each other as well as from all other samples examined to date.

Historically, chum salmon were abundant in the lower reaches of the Columbia River and

may have spawned as far upstream as the Walla Walla River (over 500 km inland). Today only

remnant chum salmon populations exist, all in the lower Columbia River. They are few in

number, low in abundance, and of uncertain stocking history.

The question of the extent of the Columbia River ESU along the Washington and Oregon

coasts prompted considerable debate within the BRT. The BRT concluded, based upon the

genetic and ecological data available, that chum salmon in the Columbia River were different

enough from other populations in nearby coastal river systems (e.g., Willapa Bay, Grays Harbor,

Nehalem River, and Tillamook River) that the Columbia River ESU should extend only to the

mouth of the river.

Relationship to State Conservation Management Units

Busack and Shaklee (1995) identified Major Ancestral Lineages (MALs) and Genetic

Diversity Units (GDUs are subdivisions of MALs) for several salmon species in Washington.

This effort, which sought to identify the existing amount and patterns of genetic diversity within

the state, supports the goals of the Wild Salmonid Policy under development by state and tribal

fishery managers and is intended to facilitate its implementation. The terminology (GDUs and

MALs) differs somewhat from that of previous documents prepared by WDW and WDFW (e.g.,

Leider et al. 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 stated that they expected that individual ESUs would often include multiple GDUs but

would be unlikely to include multiple MALs.

The geographic boundaries of the proposed ESUs for chum salmon are largely consistent

with the GDUs and MALs identified by Phelps et al. (1995). With respect to populations in

Washington, three of the ESUs for chum salmon proposed here (Puget Sound/Strait of Georgia,

Hood Canal Summer-Run, and Coastal) are similar to MALs identified by WDFW. Each of the

three MALs identified by WDFW included multiple GDUs. As noted above, one difference

between the NMFS and WDFW frameworks is that Phelps et al. (1995) consider all fall chum

salmon from the Strait of Juan de Fuca to be in the Coastal MAL, whereas the BRT includes the
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Dungeness and Elwha River fall-run populations in the Puget Sound/Strait of Georgia ESU.

Another difference is that the BRT recognize a Columbia River ESU, whereas Columbia River

populations were considered by Phelps et al. (1995) to be part of two GDUs within a larger MAL

that included coastal and Strait of Juan de Fuca populations.

Relationship to ESU Boundaries for Other Anadromous Pacific Salmonids

As part of an effort to complete comprehensive status reviews for all anadromous Pacific

salmonids, NMFS has made ESU determinations for coho and pink salmon and steelhead from

the same geographic areas covered by this status review for chum salmon. Although there are

similarities in the geographic coverage of ESUs for these species, each species has distinctive

attributes that merit special consideration.

The Puget Sound/Strait of Georgia ESU for chum salmon proposed here is similar in

geographic coverage to ESUs for coho and odd-year pink salmon. As was the case for chum

salmon, genetic and life-history data for both these species showed substantial genetic

similarities between U.S. and Canadian populations. Although no recent genetic data are

available for comparing U.S. and British Columbia steelhead populations, life-history data

showed an abrupt change in smolt age at approximately the U.S.-Canada border, and this was a

significant factor in the determination that the Puget Sound ESU for steelhead does not include

populations from British Columbia. The western boundary for the Puget Sound/Strait of Georgia

chum salmon ESU is similar to the boundaries proposed for coho, pink, and steelhead salmon

ESUs.

The Hood Canal Summer-Run and Pacific Coast ESUs for chum salmon have no clear

analogues in the other species for which comprehensive status reviews have been completed.

However, the even-year pink salmon ESU (which contains a single U.S. population) shares with

the Hood Canal Summer-Run ESU the features of restricted geographic range and a small

number of component populations. The geographic coverage of the Pacific Coast ESU for chum

salmon includes areas that are inhabited by steelhead and coho salmon from multiple ESUs. It is

possible that additional information will indicate that multiple ESUs of chum salmon also occur

in this area. The geographic extent of the Columbia River ESU for chum salmon is similar, but

not exactly congruent with ESUs for coho salmon and steelhead in the same area.
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ARTIFICIAL PROPAGATION

NMFS Artificial Propagation Policy

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, defined as the progeny of naturally

spawning fish (Waples 1991). This approach directs attention to fish that spend their entire life

cycle in natural habitat and is consistent with the mandate of the ESA to conserve threatened and

endangered species in their native ecosystems. Implicit in this approach is the recognition that

fish hatcheries are not substitutes 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 and migration and spawn timing (e.g., Crawford 1979).

Second, artificial propagation poses a number of risks to natural populations that may affect their

risk of extinction or endangerment (see “Assessment of Extinction Risk,” p. 144). 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 latter determination would be made following a

proposed listing and is not considered further in this document. The remainder of this section is

intended to provide a summary of the nature and scope of artificial propagation activities for

chum salmon.

Overview of Worldwide Artificial Propagation of Chum Salmon

More artificially propagated chum salmon are released annually into the Pacific Ocean

than are any other salmonid species. The majority of these fish, from both Asia and North

America, are released directly from hatcheries as 1- or 2-month-old fed fry, although unfed fry

are occasionally released (as well as eyed eggs planted) (Mahnken et al. 1983, Salo 1991, NRC

1995). Traditionally, most chum salmon hatcheries released juveniles directly into freshwater

streams located near seawater. More recently, releases of chum salmon juveniles from seawater

acclimation facilities have become common, especially in Japan, northern Puget Sound (Lummi

ponds), Hood Canal (the Hoodsport Hatchery in Hood Canal has acclimated chum salmon in

seawater since the early 1950s), and on the Oregon coast.
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Asia

Chum salmon are the primary focus of salmonid artificial production in Asia, and the vast

majority of this production is from Japan (Fig. 17). Of 2.8 billion artificially propagated chum

salmon released annually from Asia and North America, approximately 2 billion are from

Japanese hatcheries (Mahnken et al. In press). Adult returns to Japanese coastal fisheries from

these releases were more than 78 million fish in 1995 (Mahnken et al. In press). Japan has

pioneered the production of hatchery chum salmon, and worldwide most programs follow

guidelines developed in Japan. More than 300 chum salmon hatcheries are located on the islands

of Honshu and Hokkaido, and at least 262 rivers are managed almost entirely for artificial

propagation (Salo 1991).

Japanese hatchery programs started in 1888 with the construction of the Chitose River

Central Hatchery in Hokkaido (Kaeriyama 1989). By 1900, 45 chum salmon hatcheries had

been built in Japan; but until the 1960s, hatchery technology and fish culture practices (primarily

unfed fry were released) were not well developed. In the 1960s, the Japanese began to feed fry

in the hatcheries and to use cold well water to delay the time of release. This led to an increase

in the size of juveniles at release in May, when coastal temperatures generally exceeded 10°C

and oceanic conditions were most favorable to fry survival (Kobayashi 1980, Kaeriyama 1989).

As the percentage of fed fry increased, return rates to both Honshu and Hokkaido hatcheries

increased substantially, reaching 2.3% in Hokkaido after 1966 (Mahnken et al. 1983, Nasaka

1988, Isaksson 1988). By 1974, the Japanese catch of chum salmon had reached 10 million fish,

the highest catch since the 1880s before artificial enhancement began (Mahnken et al. 1983).

Since 1979, more than 1.5 billion juvenile chum salmon have been released annually, leading to

recent annual harvests of over 40 million adults (Nasaka 1988, Isaksson 1988, Kaeriyama 1989).

In 1995, more than 78 million chum salmon returned to Japanese rivers (Urawa26).

This success of Japanese hatchery programs has been attributed in part to efficient

hatchery practices (e.g., seawater acclimation and to the timing of fry releases to coincide with

coastal conditions favorable to survival [Kaeriyama 1989]), predator swamping (Peterman and

Gatto 1978), decreased effort for chum salmon in offshore gill-net fisheries (Mathews 1990), and

changing ocean conditions that favor survival (Pearcy 1992).

In Korea and China, small remnant populations of chum salmon are believed to exist, but

no definitive information was found on their distribution and abundance. Folsom et al. (1992)

reported that little artificial propagation of chum salmon has occurred in Korea, although the

Japanese established a few hatcheries during their occupation of the Korean Peninsula in the

early 1940s. Presently, in Korea, three hatcheries produce chum salmon: Yang Yang Inland

Research Institute (NFRDA), Sam Ceog Inland Development Business in Gang Oweon Do, and

the Inland Laboratory in Gyeong Bug. In 1996, the total number of hatchery-reared fry released

26 S. Urawa, Genetics Section, Research Division, Hokkaido Salmon Hatchery, 2 -2 Nakonoshima,

Toyohira-ku, Sapporo 062, Japan. Pers. commun., June 1996.
110
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from Korean hatcheries was about 15,850,000 fish, and the NFRDA facility produced about

75% of these fish. Most Korean chum salmon are released when they reach 7.0 cm in length

(Baik27).

In the Russian Federation, about 1 billion chum fry are released from hatcheries each

year, most of these on Sakhalin Island and the Kuril Islands (Zolotukhin and Augerot28). The

first chum salmon hatchery in the Russian Far East was constructed in 1927-1928 at Teplovka

Lake, a tributary of the Amur River. This hatchery produced an average of 23.2 million eggs and

20.4 million fry annually from 1938 to 1952. By the 1980s at least 17 hatcheries operated on

Sakhalin Island, 3 on Iturup Island in the Kurile Archipelago, 4 on the Amur River, and 1 on the

Kamchatka River (Atkinson 1983). Construction of new hatcheries has continued in the 1990s,

primarily by joint Russian and Japanese cooperatives (Zolotukhin and Augerot footnote 29).

Rukhlov (1982, cited in Atkinson 1983) reported that 391 million chum salmon and 468 million

pink salmon were released from Russian hatcheries in 1978. During the 1970s, hatcheries on

Sakhalin Island released approximately 150-200 million chum salmon fry annually (Kanid’yev et

al. 1970). However, production has often been less than anticipated. In Primorye Territory, two

chum salmon hatcheries built in 1986 have each produced only 10,000-30,000 chum fry per year,

whereas plans called for production of 80 million (Zolotukhin and Augerot, footnote 29).

Unlike Japanese programs, Russian hatchery programs were never designed to manage

rivers exclusively for hatchery fish. Russian hatcheries have generally used local chum salmon

for broodstock, and no attempt has been made to block natural production. However, natural

production and habitat protection were not first priorities: Chum salmon eggs were transferred

among hatcheries, and surplus hatchery fish were allowed to spawn with natural fish (Atkinson

1964, 1983; Zolotukin and Augerot, footnote 29). In the late 1970s, on the advice of Russian

geneticists, hatchery managers reduced the number of egg transfers to reduce the effects of

interactions between natural and hatchery fish (Helle 1979).

Alaska

Until recently, chum salmon were not highly regarded by Alaskan fish culturists and were

seldom propagated (Roppel 1982). However, in response to low salmon abundance in the early

1970s, chum salmon were identified in the Southeast Regional Plan as the preferred species for

large-scale hatchery production (Bachen and Linley 1995), and legislation permitting the

operation of private, nonprofit hatcheries was enacted in 1974 (McNair 1996). In the 1990s, over

450 million juvenile chum salmon have been released annually (Fig. 17), with a total of about 34

billion released since 1974 (McNair 1996). In 1995, there were 5 Alaska Department of Fish and

27 Kook-Ki Baik, Yang Yang Inland Research Institute, Gang Oweon Do National Fisheries Research and

Development Agency, Yang Yang, RSK. Pers. commun., June 1996.

28 S. Zolotukhin, Pacific Institute of Fisheries and Oceanographic Research (TINRO), Vladivostok,

Russia, and Xan Augerot, Center for the Analysis of Environmental Change, Nash Hall, Oregon State

University, Corvallis, OR. Pers. commun., August 1996.
112

Game (ADF&G) facilities and 31 private, nonprofit hatcheries propagating chum salmon in

Alaska, with most of the effort concentrated in Prince William Sound and southeast Alaska

(McNair 1996).

Hatchery releases in Alaska are very large compared to other North American chum

salmon artificial propagation programs: In 1995, Hidden Falls Fish Hatchery on Baranof Island

in southeast Alaska released more than 70 million juvenile chum salmon, Neets Bay Hatchery

Complex in Prince William Sound released 66 million, and the Ester Lake Hatchery Complex

released 96 million. By contrast, since 1974, total releases of chum salmon from several

hatcheries in Hood Canal have averaged about 37.3 million fish per year. In 1995, hatcheries

contributed more than 40% (16 million fish) of all chum salmon harvested in Alaska (McNair

1996).

An example of a large artificial propagation program in Alaska is the Hidden Falls Fish

Hatchery, which has been especially successful in producing fish for harvest. Between 1978 and

1995, more than 13 million chum salmon returned to the facility, with 3.5 million adults

returning in 1995. Hidden Falls Hatchery is the largest chum salmon producer in North America

(McNair 1996), and the largest single producer of chum salmon outside Japan (Bachen 1994).

The Hidden Falls Hatchery alone contributed about 22% of the chum salmon harvest in southeast

Alaska in 1993 (Bachen and Linley 1995). To minimize any effect the hatchery program may

have on local natural populations, the facility is located about 21 km from the nearest stream

with a native run of chum salmon. Terminal harvests restricted to the vicinity of the hatchery

apparently have minimized the interception and overharvest of natural chum salmon populations

in other streams in the district. However, even small but persistent rates of straying from large

hatchery programs can have a significant influence on nearby natural populations (see

“Straying,” p. 61 and “Genetics of Chum Salmon,” p. 86).

British Columbia

More than 3.3 billion chum salmon have been released from hatcheries in British

Columbia since 1960, with most of this production occurring since 1980 (Fig. 17). Currently, 90

facilities in British Columbia rear chum salmon to various early life stages before release, and 29

of these are spawning channels (Table 13) (NRC 1995). In the 1950s, the Canadian Department

of Fisheries and Oceans began to use spawning channels to enhance the natural production of

chum salmon, with an early facility located on Jones Creek on the Fraser River (Hourston and

MacKinnon 1956). These channels allowed natural spawning and did not require the handling of

fish. Recently, efforts by the provincial government to promote private participation in

enhancement efforts have resulted in a large increase in the numbers of chum salmon hatcheries

and spawning channels.
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Washington and Oregon

In the U.S. Pacific Northwest, approximately 85 million juvenile chum salmon have been

released annually between 1983 and 1993 (Figs. 17 and 18), and most of this production has

come from hatcheries in Washington (Figs. 19 and 20, Tables 14 and 15, and Appendix) (NRC

1995). Hatcheries in Oregon (Fig. 19 and Table 14) have released only small numbers of chum

salmon, chiefly into rivers on the north coast of Oregon and into the lower Columbia River Basin

(Table 15) (NRC 1995), but these releases were stopped by 1990 (Kostow 1995).

In most areas, the number of hatchery chum salmon produced in Washington is small

compared to the number naturally produced, and very small compared to the number of hatchery

fish produced annually in other areas such as Japan (2 billion) or Alaska (over 450 millon) (Fig

17) (Salo 1991, McNair 1996). Chum salmon are not the primary focus of salmon artificial

propagation in either Washington (except Hood Canal) or Oregon, as they are in Asia. For

example, in recent years, hatcheries in Washington have released almost as many juvenile coho

salmon annually (75 million) (Weitkamp et al. 1995) as chum salmon, and the vast majority of

these coho salmon are smolts, requiring a year of hatchery rearing, instead of the 0-2 months

required by chum salmon. Also, while about 25 hatcheries rear chum salmon in Washington,

there are more than 50 hatcheries in the state rearing coho salmon and more than 100 hatcheries

rearing chinook salmon.

Many chum salmon hatchery programs in Washington have been highly successful, with

the ratio of juvenile releases to adult returns similar to those of Japan. Many of these hatcheries

have produced substantial numbers of fish relative to natural production, especially in areas

where hatcheries have been used to supplement or create fall chum salmon fisheries. These areas

include Hood Canal, Bellingham Bay, and Tulalip Bay in northern Puget Sound, the Nisqually

River, and southern Puget Sound (WDF et al. 1993).

Egg-box programs and remote-site incubation facilities (RSI) were used extensively from

the late 1970s to early 1990s in the Pacific Northwest (Figs. 21 and 22). These programs

incubate salmon eggs in streamside facilities, producing emergent unmarked, unfed fry (defined

as all fish released at less than 0.4 g in the NRC [1995] database) and are particularly attractive

for chum salmon because of the species’ early immigration into seawater (Fuss and Seidel 1987).

The potential contribution of releases of unfed fry from egg-box, RSI, and hatchery facilities may

have been substantial. Estimates from the NRC database (1995) indicate that approximately

12% of all chum salmon released in Washington from 1970 to 1990 were unfed fry. Further, the

number of releases from egg boxes and RSIs has been concentrated in some locations (e.g., Hood

Canal, Fig. 22) (WDF et al. 1993, Fuss and Fuller 1994).

Although the effect of unfed fry releases may be substantial, it is extremely difficult to

estimate how many unfed fry enter rivers of their own volition from the wide variety of eggbox,

RSI, and other programs producing fry throughout the Northwest. Consequently, unfed fry have

been excluded from the tabulation of artificially propagated chum salmon in Table 16 and the

evaluation of these programs within this Section. Possible ecological effects of unfed fry releases
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are discussed in the Risk Section (p. 144), and these releases are included in the chum salmon

production data included in the Appendix (p. 256). This appendix, provided by biologists from

WDFW29, contains numbers of all chum salmon released, both fed and unfed fry, from egg-box

programs, remote-site incubators, and hatcheries in Washington, organized by the stock

designations in WDF et al. (1993). Egg-box and RSI enhancements are currently being

reevaluated by fisheries co-managers in Washington and have been curtailed in many areas

(WDFW 1995). There are presently no chum salmon egg-box or RSI programs in Oregon

(Kostow 1995).

In Washington, hatchery protocols, transfers of fish between hatcheries, adult returns of

chum salmon to hatcheries, and other performance data on hatchery stocks have been published

in a variety of sources (e.g., Fuss and Ashbrook 1995; Ashbrook and Fuss 1996; see Crawford

1997 for listing). However, in both Washington and Oregon some historical releases and

transfers have not been reported in the published literature. The SASSI report (WDF et al. 1993)

is a comprehensive inventory of naturally produced salmon populations in Washington. In

SASSI many salmon populations are identified where artificially-produced fish were believed to

have hybridized with or otherwise influenced native populations. However, the SASSI report

focused on naturally produced fish; in general, hatchery fish were identified only if they were a

component of a naturally producing run (WDF et al. 1993, Crawford 1997).

Recent Changes in Hatchery Management in Washington

In 1991, salmon co-managers in Washington instituted statewide policies to reduce the

number of out-of-basin, hatchery-to-hatchery transfers of salmonids, including chum salmon

(WDF 1991; Fuss and Ashbrook 1995; Ashbrook and Fuss 1996). These policies included

genetic guidelines specifying which transfers between areas were acceptable. The policies apply

only to transfers between hatcheries and do not explicitly prohibit introductions of non-native

salmonids into natural populations (WDF et al. 1993). At present, co-managers in Washington

are developing extensive guidelines and rules regarding all aspects of salmonid culture and

management (WDFW 1997) including transfers of hatchery chum salmon into natural

populations (WDFW 1995, 1997).

29 T. Tynan and H. Fuss, Washington Department of Fish and Wildlife, P.O. Box 43151, Olympia,

Washington 98504. Pers. commun., April 1996.
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Artificial Propagation by ESU in the Pacific Northwest

Puget Sound/Strait of Georgia ESU

The majority of chum salmon artificially propagated in the Pacific Northwest are from

hatcheries in the Puget Sound-Strait of Georgia ESU, primarily in Hood Canal and southern

Puget Sound (Figs. 18 and 20, Tables 13 and 14, Appendix) (WDF et al. 1993). An average of

65 million chum salmon fry per year have been released from U.S. hatcheries in this ESU from

1960 to 1991 (Fig 21). This compares to an average of 1.4 million fry released per year from

1958-1994 in the Pacific coast ESU, and 485,000 fry released per year from 1930 to 1991 in the

Columbia River ESU.

Hatchery propagation of chum salmon began in this ESU as early in 190530 at the

Washington State Skokomish Hatchery (Table 17) (WFC 1907), in 1911 at the USFW

Duckabush River (Station) Hatchery, and 1912 at the USFW Quilcene National Fish Hatchery

(Cook-Tabor 1994). Both fall and summer chum salmon were reared at the Duckabush River

and Quilcene facilities, but the seasonal run reared at the Skokomish Hatchery is not indicated in

the WFC reports. By 1913, 4.5 million unfed chum salmon fry were released annually from 7

Puget Sound hatcheries, and by 1919, fry releases had increased to about 13 million from 12

Puget Sound hatcheries (WFC 1916, 1921). However, chum salmon have never been the

primary focus of salmonid artificial propagation in this ESU, and it was not until the mid-1970s

that relatively large hatchery programs for chum salmon were first established in southern Puget

Sound and Hood Canal.

Prior to the mid-1970s, Hood Canal was a salmon preserve, where most commercial

salmon fishing was not allowed (although some tribal subsistence fisheries did occur in a few

rivers) and harvest of Hood Canal fish occurred in outer Puget Sound or in the ocean (Fuss and

Fuller 1994). Releases of chum salmon into Hood Canal from 1951 to 1973 averaged about 5.2

million fish per year, but with the development of large-scale hatchery programs in the Canal,

average releases of chum salmon increased to 37.2 million fish per year between 1974 and 1993

(NRC 1995).

Fall-run chum salmon

The majority of chum salmon fry artificially propagated in the Puget Sound/Georgia Strait

ESU return as adults to natal areas after mid-October and are designated as fall (formerly

30 Although release data are only available beginning in 1905, production of chum salmon may have

started earlier at the Skokomish Hatchery as reported by the Fish Commissioner in his 14th & 15th

Annual Report (WFC 1905:39): “This hatchery [Skokomish] was built in 1899 and has been operated

continuously ever since....It does not produce the best variety of fish, a large per cent of its hatchery

being Dog [chum] salmon, some Silversides but no Spring or Steelheads...”
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“normal”) chum salmon by Washington fishery co-managers (WDF et al. 1993).

Most hatchery fall chum salmon are released into their native streams in Puget Sound or

Hood Canal (Table 15, Appendix) (NRC 1995). Some hatcheries, particularly those in Hood

Canal, produced excess numbers of eggs and unfed fry (Fig. 18) (Fuss and Fuller 1994).

Historically, this excess production was often distributed to other regions (e.g., Minter Creek and

Keta Creek in southern Puget Sound, Tulalip and Bellingham Maritime Heritage Center in

northern Puget Sound, and Elwah River in the Strait of Juan de Fuca). In addition, the Samish

Hatchery appears to have mixed local fish with hatchery fish originating from Hood Canal

(Phelps et al. 1994). These transfers of hatchery fish are described in Table 15 and the Appendix

and were so common in the 1970s and early 1980s that at least 50% of hatchery chum salmon

released into the Nooksack, Skagit, Puyallup, Deschutes, and Elwha-Dungeness River basins,

and into several small southern Puget Sound river basins, were not native to the basin of release

(NRC 1995). The most widely distributed stocks were from WDFW Hood Canal, McKernan,

and George Adams Hatcheries in Hood Canal (Phelps et al. 1994, 1995). Fish from these

hatcheries were even introduced into lower Columbia River tributaries and the Siuslaw River in

Oregon (NRC 1995, Table 15).

It is difficult to determine the proportion of non-native hatchery chum salmon released

into watersheds, and in this report these numbers may be underestimated (Table 15) for three

reasons. First, in the databases used in this status review (primarily NRC 1995), many

outplanted fish were designated as “origin unknown.” To standardize the data in our tables and

figures, we assumed these were native fish, even though in many cases their status may have

been reported as “unknown” because they were not native. Second, when juvenile salmon that

had been transplanted to an out-of-basin hatchery returned to that hatchery as adults, they were

usually designated as stock from that hatchery, and the name of the river or hatchery of origin

was dropped. This occurred because it was impossible to distinguish native and non-native fish

when they returned as adults. For example, Hood Canal fish introduced into Tulalip and Mission

Creeks and released from Tulalip Bay net-pens in Port Susan in northern Puget Sound were

designated at the time of their release as juveniles by their stream of origin in Hood Canal as

“Big Quilcene River,” “Finch Creek,” or “Walcott” fall-run chum salmon. However, when these

fish returned as adults to the Tulalip Bay area, they could not be distinguished from other Puget

Sound fish and thus were designated as “Tulalip Creek” chum salmon, even though they were

derived from out-of-basin populations (NRC 1995). Similarly, Hood Canal fall chum salmon

were established at the Minter Creek Hatchery in southern Puget Sound and were subsequently

introduced into other watersheds as Minter Creek fish (Phelps et al. 1994). A third reason the

proportion of non-native hatchery fish released into watersheds may be underestimated is that all

egg transfers or releases of unfed fry from egg-boxes, RSI, or hatcheries were excluded in the

summary of west coast chum salmon releases (Table 15), as previously noted.

Summer-run chum salmon in southern Puget Sound

Artificial propagation of summer-run chum salmon in southern Puget Sound was only

recently initiated and is very small compared to the hatchery production of fall chum salmon.
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Two summer-run chum salmon hatchery programs were initiated in the late 1970s on John’s and

Coulter Creeks (Table 14), where about 1.8 and 1.1 million native summer-run chum salmon per

creek, respectively, were released annually (Table 15) (NRC 1995). Based upon adult returns, it

is believed that both hatchery programs contributed considerably to summer-run chum salmon

abundance in these streams (WDF et al. 1993). These programs were terminated on John’s Creek

in 1991 and Coulter Creek in 1992, and Washington co-managers expect run sizes in these

streams to decline because of the lack of augmentation (WDF et al. 1993). However,

escapements to these streams in 1996 of 39,600 fish, compared to an average escapement from

1984-1995 of 25,900 fish, suggest otherwise (Crawford 1997).

Winter-run chum salmon

There has been no artificial propagation of Nisqually River winter-run chum salmon,

although substantial numbers of hatchery fall-run chum salmon have been planted into the

Nisqually River (Table 15, Appendix) to support and enhance commercial fisheries in the area.

Based upon timing of adult returns and genetic analysis, these outplants have apparently not

affected native winter-run chum salmon in the river (WDF et al. 1993).

Winter-run chum salmon were propagated between 1982 and 1993 in Chambers Creek at

the WDFW Garrison Springs Hatchery (Table 14; see no. 22 in Fig. 20) and have been released

into Chambers Creek at the site of the hatchery, as well as into Clarks Creek and other tributaries

of the Puyallup River (WDF et al. 1993) (Appendix).

Hood Canal summer-run chum salmon ESU

Very few summer-run chum salmon have been artificially propagated in Hood Canal, and

the only releases in recent years have been from newly established restoration programs. These

recent releases totaled about 241,000 chum salmon fry into Hood Canal in 1993 and 1994 and

about 85,000 fry into Discovery Bay on the Strait of Juan de Fuca in 1992. Summer-run chum

salmon have been reared in Hood Canal at the Quilcene National Fish Hatchery (QNFH) (Fig.

18) from 1912 to 1937, and at a satellite hatchery, Duckabush River Station, from 1911 to 1942

(Cook-Tabor 1994). Releases of chum salmon were also reported from 1905 to 1921 from the

Washington State Skokomish Hatchery (Table 17), but whether these were summer- or fall-run

fish is undocumented. Fish from the Skokomish Hatchery were primarily released directly from

the hatchery. Chum salmon eggs reared at the other facilities were collected from various rivers

in Hood Canal and released primarily into the Little and Big Quilcene Rivers (Fig. 3), although

some releases occurred at other locations, such as Walcott Slough31 (Fig. 3). The program was

ended in 1938 when the Lower Quilcene River was “modified” and fish could no longer return to

the hatchery (Cook-Tabor 1994). Small numbers of summer chum salmon (mid-September

31 Walcott Slough is located just north of the Dosewallips River mouth and was the historical release and

recapture site for fall chum salmon produced at the QNFH (Cook-Tabor 1994).
141

spawning fish) were also released from the WDF Hood Canal Hatchery in 1962-1964, and

apparently these were the only chum salmon reared at that hatchery during those years. These

fish were apparently native to Finch Creek, the stream that runs past the hatchery (Rasch and

Foster 1978).

Hatchery production of summer-run chum salmon in Hood Canal did not occur again

until 1992, when the USFWS, WDFW, and Point No Point Treaty Council (PNPTC) began a

program to rear the salmon run at the QNFH in response to declines in the population (CookTabor 1994). Since then, about one-half of the annual return of summer-run chum salmon to the

Quilcene River has been spawned artificially (Cook-Tabor 1994). In 1993 and 1994, a total of

241,000 summer chum salmon juveniles were released into the Big Quilcene River. In 1995,

203 pairs of summer chum salmon were spawned in the hatchery (Cook-Tabor 1995) and

spawning surveys in the Big Quilcene River during this period listed 4,958 live and dead chum

salmon (about 1,770 fish per mile) (WDFW 1996).

There has been little artificial propagation of summer chum salmon from the Strait of

Juan de Fuca east of the Elwha River. Since 1992 a restoration egg box program has produced

about 85,000 fry annually in Salmon Creek, a tributary to Discovery Bay (Appendix). There are

no records of summer-run chum salmon fry plants into other streams that enter the Strait of Juan

de Fuca, including Jimmycomelately and Snow Creeks, or the Dungeness River (NRC 1995).

Pacific Coast ESU

Artificial propagation of chum salmon in this ESU has averaged about 1.4 million fry

released per year from 1958-1994 (Fig. 18). Fry have been released primarily to support

commercial and tribal fisheries and, in recent years, most releases have been from a single

hatchery near Makah, Washington (Table 15 and Appendix). In Oregon and along the Strait of

Juan de Fuca west of the Elwha River, hatchery outplanting has been relatively infrequent

compared to the Washington Coast and Hood Canal (Table 15, and Appendix) (NRC 1995, WDF

et al. 1993). Chum salmon hatcheries on the Washington coast were first established after the

turn of the century, and included a state-run facility on the Chehalis River which incubated 1.2

million eggs in 1913 and increased its output to 39 million eggs by 1919 (WFC 1916, 1921).

The USFWS National Fish Hatchery in Neston, Washington (near Makah, Washington) was

established in 1968 and released a total of about 33 million chum salmon fry from 1970 to 1993.

This hatchery primarily rears a local chum salmon stock from Cook Creek. In Oregon, the first

artificially cultured chum salmon were released in 1937 from a state-operated hatchery on the

Trask River (NRC 1995). Today, only 4 of the 23 chum salmon hatcheries that once operated on

the Washington and Oregon coasts remain, and all are in Washington (Fig. 19; note this figure

includes the Columbia River ESU hatcheries) (NRC 1995) .

Along the Strait of Juan de Fuca, fish were released into only two rivers for a total of

three years. About 188,000 fry were released in 1970 into the Lyre River, and about 170,000 fry

were released in 1978 and 1979 into the Sail River. In contrast, just a few kilometers west on the

outer coast, over 20 million chum salmon fry were released into the Sooes River from 1975 to
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1993 (Table 15). Equal or larger numbers of fry have been released into rivers along the

Washington outer coast (Table 15), but these numbers are relatively small compared to the

average of 37.5 million chum salmon released each year into Hood Canal (NRC 1995).

In recent years, chum salmon were artificially propagated on the Washington Coast only

in the Sooes and Quinault Rivers on the north coast and in Willapa Bay tributaries on the south

coast. Broodstock used in all of these programs are from adults captured in the same river where

the juveniles are released. Smaller hatchery programs for chum salmon are also currently

operating in the Hoh, Queets, Humptulips, and Chehalis Rivers (NRC 1995).

In Oregon, the magnitude of artificial propagation has been substantially less than in

Washington (Table 15). Historically, six state hatcheries produced chum salmon in Oregon’s

portion of the coastal ESU, but this production has been halted in recent years (Kostow 1995,

NRC 1995). Private hatcheries also released chum salmon in Oregon from 1973 to 1994, and

many of these fish were of non-native origin, including fish from Hood Canal (Table 15). Some

straying was observed from at least one of these private facilities (Kostow 1995). However,

returns of non-native chum salmon have generally been poor, and only one private facility still

released chum salmon in 1994.

Historically, out-of-basin transplants within the coastal ESU were common (Table 15,

Appendix). For example, almost half of about 20 million chum salmon released into the Sooes

River from 1975 to 1993 originated from out-of-basin sources, including Hood Canal and

Quinault River hatcheries (NRC 1995). In the Quinault River, almost 17% of about 5 million

chum salmon fry released annually between 1971 and 1979 originated in Hood Canal (NRC

1995). The effects of these out-of-basin plants are not well studied, and the chum salmon in

these rivers have not been genetically characterized. However, WDF et al. (1993) reported that

non-native chum salmon have largely replaced native chum salmon in the Sooes River. Nonnative chum salmon also appear to have extensively hybridized with native fish in the Quinault

River, and chum salmon in the Queets River are also not considered to be a distinct population

because of hybridization or replacement of native fish with Quinault River fish.

Chum salmon populations along the southern Washington Coast (e.g., Humptulips,

Chehalis, Nemah, and Naselle River systems) show less evidence of introgression from hatchery

fish introduced into these rivers (WDF et al. 1993). This relative lack of hybridization between

non-native fish and native fish in southern Washington coastal populations may be due to the

greater use of local broodstock in hatchery programs from this area (Table 15, Appendix).

Columbia River ESU

Little artificial propagation of chum salmon has occurred in the Columbia River

compared to other areas in the Pacific Northwest (Fig. 18, Tables 15 and 16, Appendix), and this

has usually been conducted in areas that no longer contain native chum salmon stocks. From

1930 to 1991 an average of only 485,000 chum salmon fry were released annually. Historically,

chum salmon were reported to be present in almost every river in the lower Columbia River
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Basin, but most of these runs disappeared by the 1950s (Rich 1942, Marr 1943, Fulton 1970).

Presently, on the Washington side of the lower Columbia River, only three streams are

recognized as containing native chum salmon: Hamilton and Hardy Creeks near Bonneville

Dam at RKm 235, and Grays River (RKm 34) (WDF et al. 1993).

Historical plants of non-native hatchery chum salmon into the Columbia River Basin

(comprised of fish from the coast, Hood Canal, and a small portion of Japanese origin) are

believed by WDFW not to have hybridized with local populations for several reasons. Hatchery

fish were planted to supplement fisheries only in areas without native chum salmon and in areas

where spawning was poor or nonexistent (WDF et al. 1993). Recent genetic analysis of fish

from Hardy and Hamilton Creeks and from the Grays River also indicate that these fish are

genetically distinct from other chum salmon populations in Washington (WDF et al. 1993,

Phelps et al. 1994). At present, only a single cooperatively owned hatchery on the Chinook

River (a tributary to the Columbia) produces hatchery chum salmon for the Columbia River and

propagates chum salmon imported from Willapa Bay. Approximately 360,500 chum salmon fry

were released annually by this hatchery between 1982 and 1991 (WDF et al. 1993).

About 22 populations of chum salmon have been reported on the Oregon side of the

Columbia River (Kostow 1995). Big Creek and the Klaskanine River (the latter a tributary to the

Youngs River near Olney, OR) are the only river systems that have received significant numbers

of hatchery chum salmon, and in both cases, local fish were used for supplementation (Table 15)

(NRC 1995).
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ASSESSMENT OF EXTINCTION RISK

Background

The ESA (1973, Sect. 3) defines the term “endangered species” as “any species which is

in danger of extinction throughout all or a significant portion of its range.” The term “threatened

species” is defined as “any species which is likely to become an endangered species within the

foreseeable future throughout all or a significant portion of its range.” NMFS considers a variety

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

1) absolute numbers of fish and their spatial and temporal 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, 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 based on the best scientific information available regarding its status, after taking into

consideration conservation measures that are proposed or are in place. In this review, we did not

evaluate likely or possible effects of conservation measures. Therefore, we do not make

recommendations as to whether identified ESUs should be listed as threatened or endangered

species, because that determination requires evaluation of factors not considered by us. We have

drawn scientific conclusions about the risk of extinction faced by identified ESUs under the

assumption that present conditions will continue (recognizing, of course, that natural

demographic and environmental variability is an inherent feature of “present conditions”).

Conservation measures will be taken into account by the NMFS Northwest and Southwest

Regional Offices in making listing recommendations.

Aspects of several of these risk considerations are common to all four chum salmon

ESUs. These are discussed in general below; more specific discussion of factors (e.g., harvest)

for each of the ESUs under consideration here can be found in the following sections.

Absolute Numbers

The 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 expected time until
145

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 comprise most of the data available

for Pacific salmon and steelhead. In assessing the future status of a population, the number of

reproductive adults is the most important measure of abundance, and we focus here on measures

of the number of adults escaping to spawn in natural habitat. However, total run size (spawning

escapement + harvest) is also of interest because it indicates 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 chum salmon artificially spawned for a hatchery, restoration, or egg box

(RIS) program are included under “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 composed of two

components (Fig. 23): “hatchery produced,” 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.

Historical Abundance, Habitat, and Carrying Capacity

For chum salmon, quantitative estimates of historical abundance are generally lacking.

At best, historical abundance can be inferred from fishery landings data. Fishery landings

suggest that chum salmon abundance may be near historical levels in the Puget Sound area, but

that natural populations south of the Columbia River (and possibly to the north) are at very low

levels relative to historic abundance.

Although knowing the relationship of present abundance to present carrying capacity is

important for evaluating the health of populations, the fact that a population is near its current

capacity does not necessarily signify full health. A population near capacity implies limits of the

effectiveness of short-term management to increase chum salmon abundance. This also implies

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
146
147

of hatchery fish may further increase population density in a limited habitat.

The relationship between current and historical abundance and habitat capacity 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 scaling long-term trends in populations. Comparison of

present and past habitat capacity can also indicate long-term population trends and problems of

population fragmentation.

Historical Changes in Estuaries

Chum salmon generally spend only a short time relative to other salmonids in streams

and rivers before migrating downstream to estuarine and nearshore marine habitats. Because of

this, the survival of early-life-history stages of chum salmon depends more on the health and

ecological integrity of estuaries and nearshore environments than for most other Pacific salmon.

Habitat loss in the estuarine or nearshore marine environment is difficult to quantify

because there are few historical studies that include baseline information, and these studies

encompass a variety of classification methods and several time intervals to measure change

(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 nearly

320 km of dikes enclosing 4.1 km2

 of marsh. In Skagit and Stilliguamish River areas, Nesbit

found that tidelands covered 520 km2 and extended 20 km inland from the present shoreline.

Across the Puget Sound region in the 1880s, Nesbit found that the areas covered by tidal marshes

greatly exceeded those covered by tidal flats, and that the extents of non-tidal freshwater marshes

were three to four times larger than tidal marshes. In contrast, by the 1980s, Boule et al. (1983)

estimated that 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, Bortelson et al. (1980), Simenstad et al. (1982), Hutchinson (1989), and

Levings and Thom (1994) have attempted to quantify changes in some Northwest estuaries.

Bortelson et al. estimated historical changes in natural habitats in eleven major estuaries. They

found, on average, a decrease in the estimated (km2) size of subaerial wetland of 64% (SD 35%)

with losses in the Puyallup of 100%, in the Duwamish of 99%, and in the Samish of 96%. Only

in the Nooksack had wetland area increased, and that was only by 0.2%. Simenstad et al. (1982)

used similar methods to calculate losses of wetlands in Grays Harbor and found a decrease of

30.3%. They also reported that the U.S. Army Corps of Engineers, as part of maintenance

dredging operations, removed 2.3 million m3 of sediments annually from estuaries in Washington

State, nearly half of this in Grays Harbor. Hutchinson (1989) estimated the change in area of

intertidal marshes around the Strait of Georgia and Puget Sound from the time of European

settlement to the present. He 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)
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wetland area in Washington and Oregon have been lost and that much of the remaining habitat is

degraded.

Levings and Thom (1994) also estimated changes in extent of habitat coverage in Puget

Sound for the following habitat types: marshes/riparian, sandflats, mudflats, rock-gravel

habitats, unvegetated subtidal, kelp beds, intertidal algae, and eelgrass. They were able to

quantify change only in the marshes/riparian and kelp bed habitats. For all other areas, they

could estimate change only as a loss or an increase. However, for the marshes and riparian areas

in the eleven major river deltas in Puget Sound, they estimated a loss of at least 76% (from 732

km2 prior to the mid-1800s to 176.1 km2 in the early 1990s), based upon the reports of Nesbit

(1885), Boule et al. (1983), and others.

Levings and Thom (1994) were also able to quantify a change in extent of kelp beds.

They found that the locations of kelp beds have been relatively well documented as navigational

aids, for marking the location of shallow rocky-bottom areas, and as sources of kelp for potash.

Based upon several comprehensive surveys (one dating back to the Wilkes expedition in 1841

[Thom and Hallum 1990]), they estimated that the length of shore with kelp beds in Puget Sound

has increased from 1912 to the present by as much as 53% (from 205.5 km2 to 313.8 km2

). The

significance of kelp beds to chum salmon is undocumented, but presumably they would supply a

refuge from waves, currents, and perhaps predators.

Most regulatory reviews and environmental analysis 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 3620 km of Puget

Sound shoreline (Canning 1997). Perhaps better estimates 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) because 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) inventoried armoring in Thurston County,

Washington and compared this to 1977 studies. They found a more than 100% increase in the

length of armoring from 1977 to 1993. Kathey (1994) inventoried armoring along Bainbridge

Island in Puget Sound and found that between 42 and 67% of the entire shoreline was armored.

In the Columbia River estuary, Sherwood et al. (1990) used a combination of circulation

modeling, analysis of river flow records, and computerized cartographic analysis to evaluate

historical change in the circulation and morphology of the Columbia River estuary from 1867 to

the late 1980s. These authors found a wide variety of significant changes, including large

changes in morphology caused by navigational improvements (such as jetties, dredged channels,

and pile dikes) and by diking and filling wetland areas. Lesser changes in morphology were

attributed to natural shoaling and erosion.

Sherwood et al. (1990) used bathymetric data from 1867 onward to estimate a decrease in

the tidal prism of roughly 15%, and a net accumulation of about 68 x 106 m3

 of sediment in the
149

estuary. They also report that large volumes of sediment have eroded from the entrance region

of the Columbia River and have been deposited both on the continental shelf and in the estuary,

contributing to the formation of new land. Ignoring the erosion at entrance to the river,

Sherwood et al. (1990) estimated deposition soil in the estuary of roughly five times the rate at

which sea level has fallen locally since turn of century. They also report that the river’s seasonal

flow cycle has been significantly altered by regulation and diversion of water for irrigation, with

the greatest change occurring after 1960. They suggest these changes in morphology and river

flow have reduced mixing, increased stratification, altered the response to fortnightly (neapspring) changes in tidal forcing, decreased the salinity intrusion length, and the transport of salt

into the estuary.

The effects of these changes (e.g. decrease in freshwater inflow, tidal prism, and mixing;

increase in flushing time and fine sediment deposition, and net accumulation of sediment) have

been extensive and include concurrent reduction in wetland habitats that have resulted in an

estimated 82% reduction in emergent plant production and a 15% reduction in benthic

marcoalgae production, a combined production loss of 51,675 metric tons of organic carbon per

year (Sherwood et al. 1990). They hyopthesize that there has been a shift from a food web

based on macrodetritus derived from emergent vegetation, to one involving microdetritus derived

from phytoplankton, consequently causing a shift from shallow-water benthic consumers to

water-column pelagic and deep-water epibenthic consumers.

Other changes in the community structure of the Columbia River estuarine ecosystem

reported by Sherwood et al. (1990) include increases in some exotic species filling new or

undeveloped niches. One example is the American shad (Alosa sapidissima), an Atlantic species

that migrated northward after plantings in California. The species entered the Columbia River

between 1876-1877 and were planted into the river in 1885-1886. Currently, shad constitutes

one of the most abundant species in the Columbia River and, as pelagic planktivores, exploits

both freshwater copepods and cladocerans as well as other prey concentrated in the estuarine

mixing zone. The increase in shad production coincides with a shift toward a microdetritusbased food web.

Historical Changes in Freshwater Habitat

Chum salmon may depend less on freshwater habitats than other Pacific salmonids, but

their spawning areas still extend up to 80 Rkm upstream in many rivers, and their requirements

for successful spawning and rearing—such as cold, clean water and relatively sediment-free

spawning gravel—are similar to other Pacific salmon (See “Life History,” p. 34).

Alterations and loss of freshwater habitat for salmonids have been extensively

documented in many regions, especially in urban areas or habitat associated with construction of

large dams. In the last 25 years, a major issue in “stream restoration” has been the role that large

woody debris (LWD) plays in creating and maintaining Pacific salmon spawning and rearing

habitat. Descriptions of pre-development conditions of rivers in Washington and Oregon that

had abundant salmonid populations suggest that even big rivers had large amounts of instream
150

LWD, which not only completely blocked most rivers to navigation but also contributed

significantly to trapping sediments and nutrients, impounding water, and creating many side

channels and sloughs (Sedell and Froggatt 1984, Sedell and Luchessa 1982). Many streams

consisted of a network of sloughs, islands, and beaver ponds with no main channel. For

example, portions of the Willamette River reportedly flowed in five separate channels, and many

coastal Oregon rivers were so filled with log jams and snags that they could not be ascended by

early explorers. Most rivers in coastal Washington and Puget Sound were similarly blocked by

large woody debris, snags, and instream vegetation. Sedell and Luchessa (1982) compiled a

partial list of major rivers that were impassable for navigation in the mid-1800s because of large

(100-1500 m-long) log jams; this list included 11 rivers in Oregon and 16 in Washington.

However, until recently, up to 90% of the funds for fish-habitat enhancement went for removal

of woody debris in streams (Sedell and Luchessa 1982).

Besides clearing rivers for navigation, extensive “stream improvements” were

accomplished to facilitate log drives. Simenstad et al. (1982) reported that historically some of

the more adverse impacts on the estuarine and freshwater habitats used by chum salmon resulted

from “stream improvements” in the 1800s and early 1900s, when logs were transported down

streams and stored in main stems of rivers, lakes and estuaries. These activities included

blocking off sloughs and swamps to keep logs in the mainstream and clearing boulders, trees,

logs, and snags from the main channel. Smaller streams required the building of splash dams to

provide sufficient water to carry logs. Scouring, widening, and unloading of main-channel

gravel during the log drive may have caused as much damage as the initial stream cleaning. In

tributaries to Grays Harbor and Willapa Bay, over 120 logging dams were identified by Wendler

and Deschamps (1955). Stream cleaning continued through the mid-1970s in many areas, not

only for flood control and navigation, but as a fisheries enhancement tool as well. Debris in

streams was viewed as something that would either impede or block fish passage and as a source

of channel destruction by scour during storm-induced log jam failures.

The past destruction, modification, and curtailment of freshwater habitat for steelhead

was reviewed in the “Factors for Decline” document (NMFS 1996) published as a supplement to

the notice of determination for West Coast Steelhead under the ESA. Although chum salmon, in

general, spawn lower in river systems than do steelhead and primarily rear in estuarine areas, this

document still serves as a catalog of past habitat modification within the range of chum salmon.

Among habitat losses documented by NMFS (1996), those with the most impact on chum

salmon include water withdrawal, conveyance, storage, and flood control (resulting in

insufficient flows, stranding, juvenile entrainment, and instream temperature increases); logging

and agriculture (loss of LWD, sedimentation, loss of riparian vegetation, habitat simplification);

mining (especially gravel removal, dredging, pollution); and urbanization (stream channelization,

increased runoff, pollution, habitat simplification). Hydropower development was considered a

major factor in habitat loss for steelhead (NMFS 1996), but is probably less significant for chum

salmon (due to chum salmon’s use of lower river areas for spawning) although many spill dams

and other small hydropower facilities were constructed in lower river areas. Lichatowich (1989)

also identified habitat loss as a significant contributor to the decline of Pacific salmon in

Oregon’s coastal streams.
151

A number of authors have attempted to quantify overall anadromous fish habitat losses in

areas within the range of chum salmon. Gregory and Bisson (1997) stated that habitat

degradation has been associated with greater than 90% of documented extinctions or declines of

Pacific salmon populations. It has been reported that up to 75% and 96% of the original coastal

temperate rainforest in Washington and Oregon, respectively, has been logged (Kellogg 1992),

and that only 10-17% of old-growth forests in Douglas-fir regions of Washington and Oregon

remain (Norse 1990, Speis and Franklin 1988). California has reportedly lost 89% of the state’s

riparian woodland to various land-use practices (Kreissman 1991). Within California, Fisk et al.

(1966) stated that over 1,600 km of streams had been damaged or destroyed as fish habitat by

1966. Approximately 80-90% of the original riparian habitat in most western states has been

eliminated (NMFS 1996). For example, Edwards et al. (1992) reported that 55% of the 43,000

stream kilometers in Oregon were moderately or severely affected by non-point source pollution.

Specific quantitative assessment of habitat degradation or attempts to evaluate the

response of fish populations to specific changes in habitat are rare (Reeves et al. 1989). For coho

salmon, Beechie et al. (1994) estimated a 24% and 34% loss since European settlement in the

capacity for smolt production in summer and winter rearing habitats, respectively, in the Skagit

River. Beechie et al. (1994) identified the three major causes of these habitat losses, in order of

importance, as hydromodification, blocking culverts, and forest practices. Similarly, McHenry

(1996) estimated that since European settlement, Chimacum Creek, Washington (northwest

Puget Sound) had lost 12%, 94% and 97% of its spawning, summer-rearing, 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.

Habitat factors identified in SASSI that may affect chum salmon

Although not all of the chum salmon stocks identified in SASSI had habitat factors listed

for them, numerous habitat- or land-use practices were identified as having a detrimental impact

on chum salmon (WDF et al. 1993). The northern portion of the Puget Sound/Strait of Georgia

ESU was reported to incur its greatest impact from agricultural (diking) and logging practices

(sedimentation). Habitat impacts in the southern portion of this ESU (excluding Hood Canal)

were listed as loss of freshwater and estuarine wetlands due to diking and armoring (e.g.,

construction of bulkheads, piers, and docks), urbanization, degradation of water quality, and loss

of spawning habitats. Habitat factors in Hood Canal were primarily identified for the Hood

Canal Summer Chum Salmon ESU and included gravel aggradation (due to logging in some

areas), channel shifting, and diking. No chum salmon habitat factors were identified in the

Washington portion of the Coastal ESU, but the greatest impacts to other species were reported

to be from forest and agricultural practices. In the Lower Columbia River ESU, habitat

“limiters” associated with chum salmon included gravel quality and stability, availability of

high-quality nearshore, main stem freshwater and marine habitat, road building, timber harvest,

diking, and industrialization (WDF et al. 1993).
152

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. These data sources and methods are discussed in more

detail below, under the “Approach” section (p. 156). Regular sampling has not been conducted

for many chum salmon populations outside the Puget Sound region, and data series are quite

short for many of those populations that have been sampled. When time 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 important role of artificial propagation for Pacific salmon and steelhead requires

careful consideration in ESA evaluations. Artificial propagation has implications for evaluating

both production trends and the genetic/ecological integrity of populations. Waples (1991) 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. Thus, an important question in the threshold determination is whether natural

production is 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 chum salmon in the contiguous United

States has been relatively minor compared with natural production, with the exception of a few

areas of localized, intensive artificial propagation. 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 judgment. Events

affecting populations may include natural changes in the environment or human-induced

changes, either beneficial or detrimental. Possible future effects of recent or proposed

conservation measures have not been taken into account in this analysis, but we have considered

documented changes in the natural environment. A key question regarding the role of recent

events is: Given our uncertainty of the future, how do we evaluate the risk that a population may

not persist?
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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 Changes

Climatic conditions are known to have changed recently in the Pacific Northwest (see

“Oceanic and Climatic Variability,” p. 29). 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. Chum salmon

tend to migrate farther offshore than chinook and coho salmon, and are thought to have been less

affected by changes in the nearshore environment. However, the chum salmon populations

considered in this review are from the southern end of the range of the species, and their

migration patterns are poorly understood. Much of the Pacific coast has also been experiencing

drought conditions in recent years, which may depress freshwater production even of species

such as chum salmon that spend only a brief time in freshwater. At this time, we do not know

whether these climate conditions represent 1) a long-term shift in conditions that will continue to

affect salmonids into the future or 2) short-term environmental fluctuations that can be expected

to reverse in the near future.

Genetic Integrity

In addition to being a factor in evaluating natural replacement rates, artificial propagation

can have a substantial influence on genetic/ecological integrity of natural salmon and steelhead

populations. This can occur in several ways. First, stock transfers that result in interbreeding of

hatchery and natural fish can lead to the loss of fitness in local populations and the loss of

diversity among populations. The latter is 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 salmon or steelhead hatchery dramatically changes the

mortality profile of a population, some level of genetic change relative to the wild population is

inevitable even in hatcheries that use local broodstock (Waples 1991). 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
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spawners still can have ecological and indirect genetic effects on natural populations. On the

spawning grounds, hatchery fish may interfere with natural production by competing with natural

fish for territory and/or mates. If 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.

For populations with low abundance (either natural or hatchery), small-population effects

(inbreeding, genetic drift) can also 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). 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. However, we are not aware of empirical evidence

for inbreeding or outbreeding depression or loss of genetic variability in any natural or hatchery

populations of Pacific salmon or steelhead.

Although past hatchery practices may have substantially influenced some isolated chum

salmon populations, the relatively small magnitude of most current hatchery programs and the

predominant use of local broodstock argue that hatchery practices are unlikely to threaten the

genetic integrity of most chum salmon populations considered in this review. Large programs

take place in Hood Canal and southern Puget Sound, and genetic concerns in these areas are

proportionally greater. Small population effects (such as genetic drift, mutation, and

introgression) are likely to influence summer-run chum in Hood Canal and populations spawning

from the Columbia River south.

Assessment of genetic influence of hatchery transfers

For almost 100 years, hatcheries in the U.S. Pacific Northwest have produced chum

salmon for the purpose of increasing harvest and rebuilding depleted runs. However, as reported

by Phelps et al. (1994:64):

Unfortunately a typological concept [the concept that one individual of a species has the same

genetic potential as another] of species existed until recently and considerable movement of eggs

and fry from one geographical region to another has occurred. Most of the stock transfers [in

Washington] have occurred from chum salmon hatcheries in Hood Canal to streams and

hatcheries in south and north Puget Sound, and the Strait of Juan de Fuca. Although these

transfers ceased in the early 1980’s, hatchery strains (with the Hood Canal chum salmon gene

pools) are still being used at some hatcheries and wild populations may have been mixed with

hatchery strains at the hatchery and through straying. Recently, the hatching of chum salmon in

small stream-side incubators has become popular with volunteer groups. When eggs are

provided from hatchery sources, these projects have the potential to disrupt historic patterns of

genetic diversity.

It is difficult to assess directly the influence of these population transfers on natural
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populations, because information is lacking in most cases. However, the results of two recent

genetic analyses provide evidence that introduced hatchery fish have hybridized with hatchery

and natural fish. Phelps et al. (1994, 1995), using significance testing of allelic frequencies and

cluster analyses, found that chum salmon in five hatcheries outside Hood Canal (Minter Creek

and Keta Creek in southern Puget Sound, Tulalip and Bellingham Maritime in northern Puget

Sound, and the Elwha River on the Strait of Juan de Fuca), which had received eggs or fish for

several years from Hood Canal hatcheries, had allozyme frequencies similar to those in Hood

Canal hatchery populations. In addition, Phelps et al. (1994:76) concluded from analyses of

allozyme frequencies of fish from Fennel Creek and Sherwood, Rocky, and Coulter Creeks in

southern Puget Sound that “several wild chum salmon populations outside Hood Canal . . . may

have had substantial genetic influence from Hood Canal origin hatchery chum salmon.” Several

management actions were taken because “the presence of these hatchery strains limit the

application of mixed-stock analysis and potentially jeopardize wild gene pools through

interbreeding” (Phelps et al. 1995:75). Among these actions were the replacement of Minter and

Keta Creek populations with more genetically-similar southern Puget Sound hatchery fish, the

application of a genetic mark to Tulalip Hatchery chum salmon to evaluate the extent of

hybridization with natural populations, and the cessation of transfers of fish from the Elwha

Hatchery to other locations (Phelps et al. 1995).

Autocorrelation analysis (see “Genetics,” p. 86) can also be used to assess the genetic

effects of egg transfers by determining whether groups of populations are genetically more

similar to each other than would be expected from random dispersion around the average

frequency of an allele. As discussed in the “Genetics of Chum Salmon” (p. 86), natural

populations separated by more than about 250 km did not typically show significant positive

autocorrelation (Fig. 14), most likely because of isolation by distance. Positive autocorrelation

between specific groups separated by more than 250 km may be evidence of an interaction

between the groups mediated by artificial gene flow.

We, therefore, calculated Moran’s coefficient (I) between 8 geographic or hatchery

groups of samples reported in Phelps et al. (1994) and Phelps (footnote 28) for 19 allozyme

alleles. These groups included 1) British Columbia (N=18 samples), 2) northern Puget Sound

(N=16), 3) southern Puget Sound (N=14), 4) Hood Canal natural populations (N=4), 5) outer

coast of Washington (N=8), 6) populations that have received outplanting of Hood Canal fish

(N=7), 7) Hood Canal hatcheries (N=5), and 8) hatcheries that have received Hood Canal eggs

(N=4). A jackknife variance was used to calculate a 95% confidence interval to test for departure

from the expected value, I =-1/(N-1), where N is the total number of samples used in the analysis.

For this analysis of 79 samples, the expected correlation between groups was I=-0.0128.

Average autocorrelations for pairwise comparisons between groups of natural populations

(groups 1-5) were negative, with one exception. The 9 negative correlations reflect genetic

differentiation between geographically distinct groups 1-5 (except groups 4 and 5). The single

exception to the pattern of negative correlation between distinct groups of natural populations

was a significant positive autocorrelation between Hood Canal and outer coastal natural
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populations. A positive, though not significant, average correlation was also found between

outer-coast natural populations and Hood Canal hatcheries. These two positive correlations may

indicate that egg transplants from Hood Canal to rivers on the coast have influenced allele

frequencies in outer-coast populations.

Comparisons involving Hood Canal hatcheries, or hatcheries stocked with Hood Canal

eggs, generally showed negative correlations with natural populations, except for positive but

nonsignficant, correlations for comparisons with natural populations in southern Puget Sound.

Positive correlations between these groups would not be expected because they are separated by

at least 250 km. This pattern may reflect post-glacial colonization of these two areas by a

common ancestral source population. Another possibility is that the similarity between

populations in the two areas may reflect an earlier pathway between Sinclair Inlet in southern

Puget Sound and Hood Canal during the Fraser glacial period (Burns 1985, Blair 1991). A

connection may have also existed between southern Puget Sound and the Pacific Ocean when a

glacial lake drained from what is now Budd Inlet, through the Chehalis Valley to the ocean

(Burns 1985). This connection has resulted in other zoogeographic similarities between southern

Puget Sound and the Chehalis River Basin (McPhail and Lindsey 1986). Alternatively, the

genetic similarity between these groups may indicate a general influence of Hood Canal egg

transfers into southern Puget Sound natural populations.

Evidence for the influence of hatchery transfers and outplantings on other populations can

be found in comparisons involving Hood Canal hatcheries. Positive, significant correlations in

allele frequencies were detected in the three possible comparisons between groups 6-8: Hood

Canal hatcheries, populations receiving eggs from Hood Canal hatcheries, and hatcheries outside

Hood Canal with a history of egg transfers from Hood Canal hatcheries. These positive

correlations are consistent with the hypothesis that egg transfers between hatcheries and

outplantings have genetically influenced the receiving populations.

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 a general decline in body size of spawners, there is no clear evidence for

effects of such risk factors for chum salmon in Washington and Oregon. Other factors may be

important for individual populations, as noted in the ESU summaries below.

Approach

Previous Assessments

Previous reviews of the status of chum salmon populations have been conducted

(Nehlsen et al. 1991, WDF et al. 1993, Nickelson et al. 1992, Kostow 1995). These reviews used
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a variety of methods and criteria for evaluating the status of salmon stocks. Nehlsen et al. (1991)

considered the status of populations coastwide and evaluated their risk of extinction. They

reported only the status of populations they considered to be at risk of extinction, categorizing

populations as possibly extinct, at high risk of extinction, at moderate risk of extinction, or of

special concern.

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 historical levels, were continuing to decline, or had spawning

escapements of less than 200. Populations were classified as “at moderate risk of extinction” if

they had declined from historic levels but presently appear to be stable at a level above 200

spawners. Nehlsen et al. (1991) felt that populations in this category had reached the threshold

for classification as threatened under the ESA. Populations were classified as “of special

concern” if a relatively minor disturbance could threaten them, insufficient data were available

for them, they were influenced by large releases of hatchery fish, or they possessed some unique

character. Nehlsen et al. (1991) also included a partial list of populations that they believed to be

extinct. The other reviews are limited to individual states and are thus more limited in area, but

are intended as inventories of populations and are more complete in terms of coverage within the

areas they cover.

Washington

WDF et al. (1993) classified stocks by origin (native, non-native, mixed, or unknown),

production (wild, composite, or unknown), and status (healthy, depressed, critical, or unknown).

However, the stock status designations in SASSI (WDF et al. 1993) are not considered a “risk

assessment” by these authors because SASSI is a survey that did not address threats to the future

of the populations listed (Ames footnote 15). Stock status was classified as healthy if recent

production was consistent with current habitat conditions. However, WDF et al. (1993)

combined hatchery production with natural production if a hatchery was located on a stream that

supported natural spawning, and, because the report considered only recent production status, it

did not consider possible negative impacts of hatchery production on natural populations. WDF

et al. (1993) recognized 72 chum salmon stocks in Washington. Of these, 48 were rated healthy,

3 were rated depressed, 2 were critical, 18 were of unknown status, and 1 (Chambers Creek

summer-run chum salmon) was considered extinct (Table 18). Only one stock is classified as

extinct because the authors considered only recent and not historical extinctions. Half of the

stocks of unknown status were from the Strait of Juan de Fuca and the west side of the Olympic

Peninsula. The classification of stock status by WDF et al. (1993) differed substantially from

that of Nehlsen et al. (1991) mostly because of differences in the intent of the two classifications.

Nehlsen et al. (1991) considered the Duwamish/Green River fall chum salmon to be at

high risk of extinction because of habitat loss and degradation. WDF et al. (1993) divided chum

salmon in this watershed into a possible remnant native stock (Duwamish/Green River) whose

status was unknown and into a hatchery run (Crisp or Keta Creek) introduced from releases of

Quilcene and Hood Canal hatchery stocks. The Crisp Creek status was listed as healthy,
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although all population-assessment data available are from hatchery rack counts and hatchery

planting records. As reported in the South Puget Sound SASSI Appendix (WDF et al. 1993,

Appendix 1—South Puget Sound, p. 191):

Currently, most of the fish are seen between Burns and Crisp Creeks. Natural spawning does

occur in this reach, but many of these fish may be hatchery fish headed for the Keta Creek

facility. In fact, there is some doubt that any native fish exist . . . Efforts are underway to

determine if any of the native fish remain.

Nehlsen et al. (1991) considered the Elwha and Ozette Rivers’ fall chum salmon runs to

be possibly extinct, whereas WDF et al. (1993) listed the status of these runs as unknown.

Nehlsen et al. (1991) listed Nisqually and Walla Walla Rivers’ fall chum salmon as extinct and

the Washougal River fall chum salmon as possibly extinct; these stocks were not mentioned by

WDF et al. (1993), because SASSI addressed only recent extinctions (Ames footnote 15).

Nehlsen et al. (1991) considered Hood Canal and Chambers Creek summer chum salmon to be at

moderate risk, whereas WDF et al. (1993) considered Chambers Creek summer chum salmon as

extinct and Hood Canal summer chum salmon as critical. Finally, Nehlsen et al. (1991)

considered lower Columbia River chum salmon to be at moderate risk; WDF et al. (1993)

divided these fish into three separate stocks, two of which were classified as depressed and one

as healthy.

Oregon

Within Oregon, Nehlsen et al. (1991) (Table 19) listed 11 chum salmon populations, in

addition to the Lower Columbia River chum salmon population, which also extended into

Washington (Table 18). They considered the Umatilla River population to be extinct, and

populations in Tillamook Bay, Netarts Bay, and Nestucca Bay at moderate risk of extinction.

They also identified seven stocks from Siletz Bay south which they considered to be at high risk

of extinction.

Chilcote et al. (1992) listed an inventory of chum salmon runs in Oregon and evaluated

them under the Oregon Wild Fish Policy (Chilcote et al. 1992) (Table 19). This policy has two

compliance criteria: a hatchery criterion that requires naturally spawning populations to 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 that requires at least 300 average

spawners. Kostow (1995) is a revision of Chilcote et al. (1992), with newer information on stock

presence or absence. Chilcote et al. (1992) considered the percentages of hatchery strays and

their genetic constitution in all chum salmon runs in Oregon in compliance with the hatchery

criteria. Of 50 populations of chum salmon identified in Oregon, they considered 4 to be in

compliance with the numerical criterion and 4 out of compliance. The remaining 42 populations

were of unknown status.
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Nickelson et al. (1992) evaluated the status of coastal populations of chum salmon in

Oregon. They classified populations as healthy if available spawning habitat was fully seeded

and abundance trends were stable or increasing over the last 20 years. They classified

populations as “of special concern” if they were believed to be composed of fewer than 300

spawners, or had a naturally spawning population that consisted of more than 50% strays from a

genetically-similar hatchery stock or 10% strays from a dissimilar hatchery stock. Populations

were classified as depressed if available spawning habitat was not fully seeded, abundance trends

were declining over the last 20 years, or abundance trends in recent years were below the 20-year

average. Nickelson et al. (1992) classified the status of 26 stocks; of these, 10 were considered

healthy, 12 “of special concern,” and 4 of unknown status due to insufficient data.

The 1994 biennial report on wild fish status in Oregon (Kostow 1995) considered chum

salmon populations in the Columbia River to be very depressed to extinct. Kostow (1995) also

described the Nehalem River as having a population of several hundred adults, and the

Necanicum River population as very small, unstable, and vulnerable. Chum salmon populations

in Tillamook Bay, Netarts Bay, and the Nestucca River were described as the most substantial

populations in Oregon, with Tillamook Bay having estimated escapements of 10,500 adults in

1992 and 7,500 adults in 1993. Chum salmon populations south of the Nestucca River were

described as very depressed or extinct, with remnant populations in the Salmon, Alsea, Yaquina,

Siletz, and Coos Bay River systems, and scattered adults occasionally seen in other basins

(Kostow 1995).

California

Nehlsen et al. (1991) listed chum salmon runs in the Sacramento River and Klamath

River as extinct.

Data Evaluations

Quantitative evaluations of data included comparisons of current and historical

abundance of chum salmon, and calculation of recent trends in escapement. Historical

abundance information for these ESUs is largely anecdotal. Time-series data were available for

many populations, but 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 naturally

spawning populations, including (where available) recent total spawning run size and

escapement, percent annual change in total escapement, and recent naturally-produced spawning

run size and escapement.

Although this evaluation used the best data available, they have several limitations, and

not all summary statistics were available for all populations. For example, spawner abundance

varies by state and region, and in some areas, (particularly where chum salmon are not presently

abundant) abundance was generally not measured directly. Instead, abundance was often

estimated from catch (which itself may not always have been measured accurately) or from
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limited survey data. In many cases, limited data were also 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 complete in terms of long-term adult

abundance records for chum salmon in the regions included in this review. Principal data

sources were run reconstruction and fishery statistics from commercial, tribal, and recreational

fisheries, and escapement estimates from stream surveys of spawning escapement. However,

although the above provide the “best” estimates of chum salmon production, actual run-size may

vary from these estimates. Specific problems are discussed below for each data type.

Data Types

Washington

Information on the abundance of natural chum salmon populations in Puget Sound

includes fishery landings data and spawning escapement surveys. While chum salmon fisheries

occur in several Puget Sound rivers, most chum salmon are harvested in saltwater, as fish return

to different spawning areas. The relative run size in terminal areas and genetic mixed-stock

analysis (MSA) indicate that various stocks are included in these mixed-stock fisheries (Graves

1989).

In the northern portion of Puget Sound, chum salmon escapement is estimated for river

basins by scaling base-year mark-recapture estimates (Eames et al. 1981) by the ratio of total

spawners in index areas to the index values in the base years. Estimates for individual stocks at a

finer level are usually not available. In general, index counts are available, but the base-year data

necessary to scale them at the stock level are lacking for some areas (Hendrick32). Data for

southern Puget Sound are primarily from spawning ground surveys (where all, or nearly all, of

the spawning habitat is surveyed) and from hatchery rack counts. Prior to 1976, spawning

ground surveys were used primarily to define peak counts of live fish, and since then most

estimates have been based on area under-the-curve (AUC) calculations derived from weekly

spawning ground surveys. WDFW used the AUC method, after it was introduced in 1976, to

estimate peak abundances for some locations in southern Puget Sound and Hood Canal with data

reaching back to 1968 (Uehara33).

Hood Canal summer- and fall-run chum salmon estimates of escapement from 1968 to

the present are based on the AUC methodology. Survey frequency was low prior to the mid32 D. Hendrick, Washington Department of Fish and Wildlife, 333 East Blackburn Rd., Mt. Vernon,

Washington 98273. Pers. commun., November 1995.

33 J. Uehara, Washington Department of Fish and Wildlife, P.O. Box 43151, Olympia, Washington

98504. Pers. commun., November 1995.
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1970s, and peak live spawner abundance and the full extent of spawning were often not reflected

in the curves. This means that early calculations underestimate abundances.

Chum salmon escapement has not been monitored by tribal biologists on the west side of

the Olympic Peninsula, and the only stock status data available were from landings. Chum

salmon are generally not targeted in western Olympic Peninsula or tribal fisheries, and since the

fisheries tend to occur near river mouths, it is not known to what extent the fish in the landings in

a river originate from that river. In Grays Harbor, index counts of peak spawners were expanded

to estimate total escapement, and in Willapa Bay, WDFW estimated escapement using AUC

methodology from spawning ground surveys of adults (Brix34).

According to Washington fisheries co-managers (WDF et al. 1993), Columbia River

chum salmon populations on the Washington side of the river were limited to Grays River,

Hardy Creek, and Hamilton Creek. However, biologists from WDFW have also observed chum

salmon in the Lewis, Cowlitz, and Kalama Rivers (Ames footnote 15). Fish spawn in limited

areas of these streams, and spawning grounds have been surveyed annually since 1976. These

surveys cover most of the spawning habitat in the streams surveyed, and counts at Bonneville

Dam monitor chum salmon ascending the Columbia River beyond these streams. WDF et al.

(1993) estimated that recent spawning escapement of chum salmon in the Columbia River was in

the range of “a few thousand up to ten thousand.”

Oregon

In Oregon, chum salmon spawning escapement has been monitored by ODFW using peak

counts of live and dead fish in standard surveys in the Tillamook District since 1948 at Moss

Creek, Clear Creek (Kilchis River), and the Little North Fork of the Wilson River. An additional

survey site (Nestucca River) was added in 1950. The intention of ODFW was to monitor trends

in escapement, and they have not attempted to quantify total escapement (Cooney and Jacobs

1994).

From 1957 through 1972, an impassible culvert was present near the mouth of Moss

Creek, and from 1960 through 1982 one was present on Clear Creek. Also in 1960, logging and

road slides clouded the water and hampered viewing in the Wilson River. In an attempt to

improve the census of spawning fish, ODFW surveyed 11 more areas, and in 1976 reclassified 4

of these supplemental surveys as standard surveys. The degree to which the surveys tracked

spawner abundance is questionable, because the amount of habitat has not been well monitored

and there have been unrecorded changes in quality and quantity of the survey areas.

Nevertheless, Nickelson et al. (1992) used the relationship between the survey data and

commercial landings to estimate total escapement to Tillamook Bay. In 1992, ODFW added 21

34 R. Brix, Washington Department of Fish and Wildlife, 48 Devonshire Rd., Montesano, Washington

98563. Pers. commun., March 1997.
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supplemental surveys in addition to its 8 standard surveys (Cooney and Jacobs 1994).

Supplemental surveys were located from the North Coast District as far south as the Yaquina

River. These supplemental surveys have been monitored since then (Klumph and Braun 1995).

In addition, a trap constructed by Oregon State University on Whiskey Creek in Netarts Bay has

been in operation since 1969 (Nickelson et al. 1992).

California

In California, chum salmon spawning escapement has not been monitored.

Run Size

In Washington, run size in Puget Sound was calculated by run reconstruction.

Interceptions by Canadian fisheries were considered relatively minor and were not incorporated

in the run reconstructions. Landings within Puget Sound were attributed to production units on

the basis of geographic locations of the fisheries and spawning grounds, and tagging studies.

Run reconstruction was also used to calculate run size in Grays Harbor and Willapa Bay. In

other areas, run-size estimates were not available. Run size can be estimated by summing

terminal catch and spawning escapement, because ocean interceptions are assumed to be

negligible. However, in coastal rivers on the Olympic Peninsula, the Columbia River Basin

(exclusive of the Washington side), and coastal Oregon streams, spawning escapement has not

been estimated.

Fishery landings

Fishery landings were estimated more accurately than spawning escapement. However,

landings contain less information on the abundance of individual stocks. While they are

informative in monitoring the overall abundance of chum salmon in broad geographic regions

within Puget Sound, the bulk of commercial fishing occurs on mixed stocks, and the current data

have not as yet been resolved into component stocks. For coastal rivers on the west side of the

Olympic Peninsula, these are the only data available and more accurately reflect landings from

individual rivers.

Computed statistics

To represent current run size or escapement 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 shorter than 5 years). We used only estimates that reflected the total abundance for an

entire river basin or tributary, avoiding index counts or dam counts that represent only a small

portion of available habitat. Where adequate data were available, trends in total escapement (or

run size if escapement data were not available) were calculated for all data sets with more than 5

years of data, based on total escapement or an escapement index (such as fish per mile from a

stream survey).
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As an indication of overall trends in chum salmon populations in individual streams, we

calculated average (over the available data series) percentage annual change in adult spawner

indices within each river basin. Trends were calculated as the slope (a) of the regression of

ln(abundance) against years corresponding to the biological model N(t) = beat. Slopes

significantly different from 0 (P<0.05) were noted. The regressions provided direct estimates of

mean instantaneous rates of population change (a); these values were subsequently converted to

percentage annual change, calculated as 100(ea - 1). No attempt was made to account for the

influence of hatchery-produced fish on these estimates, so the estimated trends included any

supplementation effect of hatchery fish. Trend analysis can also be influenced by climate regime

shifts and other factors.

Analysis of Biological Information by ESU

Puget Sound/Strait of Georgia ESU

The Puget Sound/Strait of Georgia ESU of chum salmon encompasses much diversity in

life history, and includes summer, fall, and winter runs of chum salmon. WDF et al. (1993)

identified 38 stocks with sufficient data to calculate trends in escapement within the area

encompassed by this ESU: 10 had negative trends and 23 had positive trends (Table 20). All of

the statistically significant trends (P< 0.05) were positive and the slopes of many negative trends

were close to zero. One stock, the Chambers Creek population of summer chum salmon, met the

WDF et al. (1993) definition of extinct, a stock currently being tracked that is believed to have

been extirpated in its original range. The sum of the recent 5-year geometric means of these

escapement trends, which are not exhaustive, indicate a recent average escapement of more than

300,000 natural spawners for the Puget Sound/Strait of Georgia ESU as a whole.

Commercial harvest of chum salmon has been increasing since the early 1970s

throughout the state (Fig. 24) and the majority of this harvest has been from the Puget Sound/

Strait of Georgia ESU. The recent average chum salmon harvest from Puget Sound (1988-1992)

was 1.185 million fish (WDFW 1995). This suggests a total abundance of about 1.5 million

adult chum salmon. This increasing harvest, coupled with generally increasing trends in

spawning escapement, provides compelling evidence that chum salmon are abundant and have

been increasing in abundance in recent years within this ESU.

While most populations in this ESU appear to be healthy and increasing in abundance,

there appears to be a potential for loss of genetic diversity within this ESU, especially in

populations that display the most distinctive life histories. For example, four summer-run stocks

from southern Puget Sound were identified by WDF et al. (1993). Of these four, one was

classified as extinct, two were of mixed production, and all were relatively small. Of the three
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extant stocks, Blackjack Creek has a 5-year geometric mean spawning escapement of 524, Case

Inlet has 4,570, and Hammersley Inlet has 7,728, with about 40,000 total summer chum salmon

spawners in southern Puget Sound estimated in 1994. The latter two stocks had hatchery

supplementation programs that were believed to be major contributors to the runs until they were

discontinued in 1992 (WDF et al. 1993). The last brood year produced by these hatchery

programs (1991 brood year) returned as adults at age-4 in 1995 and age-5 in 1996. While all

three summer-run populations are apparently stable or increasing, they represent a small fraction

of the ESU. The winter-run life history is represented by only two stocks. The Chambers Creek

stock is increasing in abundance, and the Nisqually River stock is a relatively large run with a 5-

year geometric mean escapement of more than 16,000 spawners. Both stocks are classified as

wild production.

Hood Canal Summer-Run ESU

Analysis of biological information for the Hood Canal summer-run chum salmon ESU is

more extensive than that for other ESUs. This extended analysis reflects the deliberations of the

BRT in considering the dynamic changes in summer-run chum salmon abundance that have

occurred in this ESU over the past several years.

Although summer chum salmon in this ESU have experienced a continuing decline over

the past 30 years, escapement in 1995-96 increased dramatically in some streams (Fig. 25).

Spawning escapement of summer chum salmon in Hood Canal (excluding the Union River)

numbered over 40,000 fish in 1968, but was reduced to only 173 fish in 1989 (WDF et al. 1993).

In 1991, only 7 of 12 streams that historically contained spawning runs of summer chum salmon

still had escapements (Cook-Tabor 1994, WDFW 1996). Then in 1995, escapement increased to

more than 21,000 fish in northern Hood Canal, the largest return in more than 20 years (WDFW

1996). These increases in escapement were observed primarily in rivers on the west side of

Hood Canal (Fig. 26), with the largest increase in the Big Quilcene River where the USFWS has

been conducting an enhancement program starting with the 1992 brood year (Tables 21 and 22).

Streams on the east side of Hood Canal continued either to have no returning adults (Big Beef

Creek, Anderson Creek, and the Dewatto River) or no increases in escapement (Tahuya and

Union Rivers) (Fig. 26).

Summer runs of chum salmon in the Strait of Juan de Fuca (Snow and Salmon Creeks in

Discovery Bay and Jimmycomelately Creek in Sequim Bay) are also part of this ESU. While

these populations have not demonstrated the marked declining trend that has characterized the

summer-run populations in Hood Canal in recent years, they are at very low population levels

(Fig. 27). Further, though escapement of summer-run chum salmon to Salmon Creek increased

in 1996, the other two populations in the Strait of Juan de Fuca did not show similar increases

(Fig. 27), and the overall trend in the Strait populations was one of continued decline. WDF et

al. (1993) considered the Discovery Bay population to be critical and the Sequim Bay population

to be depressed (Table 18).
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Several factors may have contributed to the dramatic increase in abundance seen in some

Hood Canal streams in 1995 and 1996. These include hatchery supplementation, reduction in

harvest rate, increase in marine survival, and improvements in freshwater habitat. Information

relevant to these factors is discussed below.

Hatchery supplementation

USFWS began hatchery production of summer chum salmon in Quilcene Bay with the

1992 brood year (Table 21). In brood year 1992, 27.95% of the fry released from Quilcene

Hatchery had their adipose fins removed, and most of these were tagged with micro- (half-size)

coded wire tags (CWTs); in subsequent years, all releases have been unmarked. Marked fish

returned as age-3 spawners in 1995 and as age-4 spawners in 1996. Examination of ratios of

marked and unmarked fish provides some indication of the role of hatchery production in the

population increases seen in some areas in 1995 and 1996.

Table 22 shows the number of adults surveyed in several areas in 1995 and 1996 and the

number of those fish that were fin-clipped. These data were provided by WDFW and USFWS.

Based on the proportion of marked and unmarked fish in the fishery in Quilcene Bay, returns to

the hatchery, and returns to Big Quilcene River (considering only age-3 fish in 1995-96 and only

age-4 fish in 1996), USFWS estimated that the survival of marked fish was only 21.4% that of

unmarked fish in 1995 and 39.9% of unmarked fish in 1996. USFWS assumed in making these

estimates that all fish sampled in Quilcene Bay and the Big Quilcene River originated from

hatcheries. A major weakness with the USFWS method is that there was apparently no

independent way to confirm this assumption. This method overestimates tagging mortality if

unmarked fish of non-hatchery origin are included in the samples. While this error almost

certainly occurred, we do not have a quantitative estimate of its magnitude. Bailey (1995)

estimated the survival rate of adipose-clipped and micro-coded wire-tagged chum salmon fry

from the Nitinat Hatchery released into Barclay Sound on the west coast of Vancouver Island

was approximately 50% that of unmarked chum salmon. Given these assumptions, the estimated

hatchery contributions to escapement to the Big Quilcene River were 32% of the 3-year-olds in

1995 and 63% of the 4-year-olds in 1996.

Table 22 presents 95% confidence limits on the largest number of marked fish that could

have been present in each stream given the estimated spawning escapement, the number of

carcasses examined, and the number of marks detected in 1996. The tabulated maximal number

of marks represents the maximal number of marked fish that could have been present in the

spawning escapement with less than 0.05 probability of observing no marked fish in the carcass

surveys. These limits were calculated from a hypergeometric distribution, with the assumption

that the carcasses in the surveys were drawn randomly from a population the size of the

estimated escapement without replacement.

Table 22 also shows an estimate of the maximal number of hatchery fish that could have

been present in those streams in 1996. These estimates were obtained by expanding the maximal

number of marked fish by the effective mark rate. The latter value was obtained by adjusting the
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actual mark rate (28%) for relative marking survival (0.34 in 1996); the resulting estimate

of effective marking rate is 0.11. The total estimate was obtained by pooling all samples,

and placed an upper bound on the total number of possible strays assuming that all streams

were equally likely to receive strays. The numbers of potential strays from the USFWS

enhancement program was clearly too small to account for the observed increases in

escapement to the Dosewallips, Hamma Hamma, and Duckabush Rivers.

Collectively, these results suggest the following conclusions about the effects of hatchery

supplementation on adult returns in 1995 and 1996.

1. There is no way to evaluate accurately the contribution of hatchery fish to escapements

outside Quilcene Bay without making assumptions about effective tagging rate, and there

are no reliable estimates of that parameter. However, outside Quilcene Bay, it is difficult

to attribute many of the 1996 returns to hatchery strays unless either a) biologists missed

marked fish in areas outside the Bay at a much higher rate than they did in the Big

Quilcene River, or b) virtually all marked fish died. There is no reason to believe that a)

is true, and b) is contradicted by the presence of substantial numbers of marked hatchery

fish in Quilcene Bay. Therefore, the most parsimonious conclusion is that most, perhaps

all, 1996 adult returns of Hood Canal summer chum salmon to areas outside Quilcene

Bay resulted from natural production.

2. If fish stray from the hatchery program in the Big Quilcene River into the Little Quilcene

River, the aging rate must be very low (at least in 1996, since sampling was too low to

draw conclusions in 1995) because no marked fish were found in natural spawning areas.

3. Available data are not particularly informative about the origins of fish sampled in

Quilcene Bay. The USFWS method is based heavily on data for these fish, but it would

lead to an unbiased estimate only if all of the fish were of hatchery origin. The method

therefore cannot be used to evaluate the origins of these same fish.

4. There are similar difficulties in interpreting the data for the Big Quilcene River. It is

possible that most or all of the adults that returned in 1996 were of hatchery origin, but

this greatly depends on the level of marking mortality, and the level of bias or uncertainty

associated with this estimate is unknown. The relatively low proportion of marked fish in

1995 suggests that a significant fraction of adults returning to the Big Quilcene River in

that year was the result of natural production.

Harvest reduction

WDFW divides Hood Canal into five regions for fishery management and assessment

(Fig. 3). Spawning populations of summer chum salmon are restricted to four of these regions:

Area 12A, Dabob Bay and Quilcene Bays, includes marine waters to which Big Quilcene and

Little Quilcene Rivers are tributaries; Area 12B, Central Hood Canal, includes the marine waters

adjacent to other east and westside rivers such as Anderson Creek and the Dosewallips, Hamma
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Hamma, and Duckabush Rivers; Area 12C, South Hood Canal, includes the population in

marine waters adjacent to Lilliwaup Creek; and Area 12D, Southeast Hood Canal, includes the

marine waters adjacent to Union River. Population responses in these four areas have been quite

different, with increases in returning spawners apparent only in Areas 12A and 12B (Fig. 26) and

Area 12D (Union) being stable.

Historically, summer chum salmon have not been a primary fishery target in Hood Canal,

since harvests have focused on chinook, coho, and fall chum salmon. Summer chum salmon

have a run timing that overlaps those of chinook and coho salmon, and they have been

incidentally harvested in fisheries directed at those species (Tynan 1992). Prior to 1974, Hood

Canal was designated a commercial salmon fishing preserve, with the only net fisheries in Hood

Canal occurring on the Skokomish Reservation (WDF et al. 1973). In 1974, commercial

fisheries were opened in Hood Canal and incidental harvest rates on summer chum salmon began

to increase rapidly. By the late 1970s, incidental harvest rates had increased to 50-80% in most

of Hood Canal and exceeded 90% in Area 12A during the 1980s (Fig 25B). In 1991, coho

salmon fishing in the main part of Hood Canal was closed to protect depressed natural coho

salmon runs. Commercial fisheries, targeting hatchery-produced coho salmon, continued in

Quilcene Bay. Beginning in 1992, fishing practices in this fishery, including changes in gear,

seasons, and fishing locations, were modified to protect summer chum salmon (WDFW 1996).

Since then, the tribal and nontribal harvests of coho salmon during the summer chum migration

have been by beach seine with the requirement that summer chum salmon be released or

surrendered to the USFWS for broodstock in the interagency enhancement program at Quilcene

National Fish Hatchery.

Exploitation rates on summer-run chum salmon in Hood Canal have been greatly reduced

since 1991 as a result of closures of the coho salmon fishery and efforts to reduce the harvest of

summer chum salmon (WDFW 1996). Between 1991 and 1996, harvests removed an average of

2.5% of the summer-run chum salmon returning to Hood Canal, compared with an average of

71% in the period from 1980 to 1989.

These harvest rates, and the reconstructed run sizes on which they are based, are

imprecise and are probably overestimated in recent years, when summer-run chum salmon

abundance has been depressed. Much of the imprecision and bias stems from the practice of

using a fixed cutoff date to attribute chum salmon in fishery landings to the summer or fall run

(Lampsakis footnote 19). Because a fixed cutoff date is used to assign chum salmon to the

summer or fall run, and the runs overlap, some fish will always be misclassified. With year-toyear change in run timing, the fraction of fish misclassified can vary considerably. Even if the

fraction of each misclassified run remains constant, as abundance changes, the number of fish

misclassified changes. Because the summer run has declined relative to the fall run, the number

of fall-run chum salmon misclassified as summer run in recent years has probably been greater

than the number of summer-run chum salmon misclassified as fall run. Consequently, the cutoff

date used to distinguish summer run from fall run is presently being reevaluated by state and

tribal biologists. This may have led to an overestimation of harvest rates calculated with WDFW

adult accounting periods. Tribal biologists advocate using an earlier cutoff date to delineate the

summer run from the fall run to compensate for the change in relative abundance of the two runs
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in Hood Canal. In spite of these caveats, the reconstructed run sizes and harvest rates based on

them are the best data available to evaluate the effects of harvest and changes in population

productivity.

While changes in harvest rates coincide to some degree with changes in run size, there are

some important differences. In general, run sizes declined in the 1970s and 1980s as harvest

rates increased to relatively high levels, rebounding in 1995 and 1996 after harvest was largely

curtailed (Fig. 28). Reductions in harvests alone are insufficient to account for the population

rebounds in Dabob Bay and Central Hood Canal, and no populations in south Hood Canal and

Southeast Hood Canal have rebounded.

Harvest in Canadian waters

Summer-run chum salmon are still harvested incidentally in British Columbia in pink and

sockeye salmon fisheries in the Strait of Juan de Fuca (Area 20) and Johnstone and Georgia

Straits (LeClair 1995, 1996; PSMFC data 1997, Tynan 1995, 1997). Summer-run chum salmon

are also taken in troll fisheries off the west coast of Vancouver Island (PSMFC data 1995). Net

and troll fisheries in these areas target Fraser River sockeye and coho salmon but incidentally

harvest chum salmon. Bycatch of chum salmon in Canadian Area 20 in the period from 1968 to

1995 has estimated 2,803 fish (Tynan 1995, 1997). These harvests have traditionally been

allocated between U.S. and British Columbia populations using the proportions determined from

genetic mixed-stock analysis (MSA) estimates in samples of fall chum salmon caught in later

fisheries that were directed at chum salmon (PSC Joint Chum Technical Committee 1996).

Recently, fishery managers have begun to suspect that Hood Canal and Strait of Juan de

Fuca summer-run chum salmon may be the majority of chum salmon migrating through Area 20

in August and early September when Area 20 fisheries for sockeye and pink salmon occur

(WDFW 1996). Genetic MSA was used to estimate the proportion of Hood Canal summer chum

salmon in the Area 20 catch (LeClair 1995, 1996). Estimates indicated that Hood Canal and

Strait of Juan de Fuca summer-run chum salmon accounted for 31% of the Area 20 catch in 1995

and 68% of the catch in 1996 (WDFW 1996). This corresponded to estimated harvest rates on

Hood Canal fish of ~3% in 1995 and ~1.5% in 1996, and on Strait of Juan de Fuca fish of ~17%

in 1995 and ~2% in 1996.

Marine survival

Changes in survival, whether in the marine or freshwater life-history phases, would be

reflected in changes in the number of spawners or potential spawners produced per parent (cohort

replacement rate). The predominant age at which individual broods of Hood Canal summer

chum salmon mature is variable, ranging from 92% age-3 to 83% age-4 for the 1968 to 1985

brood years (Tynan 1992). However, the mean age of maturation during this period was 3.6
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years, so we have used spawning escapement 4 years earlier as the measure of parental

abundance for a given year’s run. This erroneously attributes some production to adjacent year’s

escapement, but differences in year to year escapement are relatively small compared to the total

contrast in escapement levels.

Using the WDFW run reconstruction database (Big Eagle et al. 1995), updates from

WDFW (Haynes35), and the escapement numbers for 1996, it is possible to reconstruct the size of

terminal runs and the exploitation rate (Fig. 28) of Hood Canal summer chum salmon through

1996. Reconstructed terminal runs represent the best available data on stock productivity.

Although the scale of run reconstruction is coarse and there are potential errors and biases in

attributing catch to runs in management sub-areas (discussed in preceding sections on harvest),

changes in harvest rates have been so large that these biases are relatively small.

A plot of spawners-per-spawner 4 years earlier (Fig. 29) suggests that substantial

increases in the cohort replacement rates did not occur until the 1990s. However, if we consider

the number of recruits-per-spawner (Fig. 30), which accounts for the effects of incidental harvest,

it appears that there were increases in productivity in the early 1980s. These increases coincided

with a climatic regime shift in the north Pacific Ocean during the late 1970s that has generally

been viewed as beneficial to chum salmon (Francis and Mantua In press). However, apparent

productivity did not increase uniformly. The largest increases in productivity were apparent only

for the populations in Dabob Bay, with populations in the central portion of Hood Canal showing

little increase in productivity until after 1990. The timing and magnitude of apparent

productivity changes, and the inconsistencies between different areas within Hood Canal, suggest

the unlikelihood that changes in marine productivity contributed substantially either to the

decline in Hood Canal in the late 1970s or to the recent rebound in some of the populations.

Record numbers of chum salmon returned to many areas of Alaska and the Pacific

Northwest in 1995 and 1996. In this ESU, some streams have also had large returns of summer

chum salmon, while other streams have not. Possible explanations are that 1) any changes in

marine survival for this ESU are being overwhelmed either by differences in survival during

freshwater or by estuarine life-history phases, or 2) summer chum salmon in Hood Canal have

ocean migration patterns different than other chum salmon, or 3) other factors such as

susceptibility to diseases.

Freshwater Survival

Density dependence—The apparent increases in population productivity in Hood Canal have

coincided with depressed spawning escapements. One possible explanation for this is that

density-dependent mortality is occurring in freshwater habitats. If density-dependent effects in

35 J. Haynes, Washington Department of Fish and Wildlife, P.O. Box 43151, Olympia, Washington

98504. Pers. commun., November 1996.
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freshwater or estuaries are reducing survival rates, a decline in recruits-per-spawner with

increasing escapement would be expected. There is some suggestion of this depensation in

Dabob Bay and central Hood Canal rivers (Fig. 31), but little support for this hypothesis in

Lilliwaup Creek (Area 12C, South Hood Canal) or the Union River (Area 12D, Southeast Hood

Canal) (Fig. 32). However, if density-dependent effects occur in central Hood Canal tributaries,

they must do so at very low abundances, because most areas do not show any suggestion of

increased productivity except at extremely low escapement levels. Bias in reconstructed run

size, which tends to be greatest at low abundance, also confounds estimates of abundance. This

tends to give the appearance of density dependence. If density dependence were responsible for

the observed recent patterns of productivity in the streams, it would be difficult to explain the

large number of summer chum salmon in the late 1960s and 1970s, unless habitat capacity has

changed since then. At present, existing data cannot determine whether density dependence has

contributed to the recent rebound in abundance.

Possible ecological effects of artificial propagation—Hatcheries that produce salmon are

usually part of fisheries management programs designed to augment natural production and to

mitigate the impact of ecological damage by human alterations of the natural habitats. However,

hatchery productions can also have an unintentional ecological influence on natural populations

(Allendorf and Ryman 1987).

In Hood Canal, several salmonid species are released annually from hatcheries (Fig. 33).

Although ecological impacts of these releases have not been extensively studied (reviewed in

Tynan 1997), a number of authors have expressed varying opinions about the repercussions of

these releases on natural summer- and fall-run chum salmon in Hood Canal and other regions.

As an example, Washington’s fishery co-managers have suggested that the extensive use of

artificial propagation in Hood Canal may have adversely affected Hood Canal summer-run chum

salmon (WDF et al. 1993:37):

There are large coho, chinook and [fall] chum rearing and release programs at several Hood

Canal hatcheries which may cause increased competition and predation on summer chum.

In addition, the USFWS Western Washington Fishery Resource Office (Cook-Tabor 1994:11)

suggested:

Indirect or direct competition between hatchery produced fall chum and naturally produced

summer chum is likely. It is possible the higher densities of small-sized hatchery released

juveniles over-exploit the zooplankton population, thus limiting the foraging success of juvenile

summer chum salmon in Hood Canal.

These issues were also addressed by Gallagher (1979:95):

The similarities in pattern of variation in the total run and brood return of both the hatchery and

wild stocks of Puget Sound chum salmon suggest that (1) a major component of the mechanism

controlling the abundance of chum-salmon stocks takes place in the early marine environment,
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and (2) given the presence and absence of pink salmon in odd and even years, that component

may involve competition for limited food resources . . . By introducing large numbers of hatchery

[fish] . . . into this ecosystem, however, a food-limited competitive interaction may be induced.

Although such an interaction may account, in part, for the fluctuations in the hatchery chum data,

it may also stress an ecosystem that seems to have evolved an equilibrium of population

regulation and coexistence. Such a stress could prove devastating to the already seriously

depressed pink and chum wild stocks of Puget Sound [original emphasis].

More recently, in Tynan’s (1997:viii) extensive review of available information on chum

salmon in Hood Canal, he hypothesized that hatchery-produced salmon may affect naturallyproduced summer chum salmon in the Hood Canal and the Strait of Juan de Fuca regions in

several ways, including the shared use of many of the same ecological resources. He has

proposed an extensive research program to investigate this issue.

In contrast, Ames (1983) did not find evidence for any adverse effects between Hood

Canal hatchery and natural chum salmon based upon correlations of production in the 1970s and

1980s. In addition, calculations by Fuss and Fuller (1994:45) on hatchery chum salmon

production and the carrying capacity of Hood Canal indicated that “large numbers of hatchery

juveniles do not appear to be negatively impacting naturally produced fry in Hood Canal.”

Most hatchery fall chum salmon are released into Hood Canal at about the same time that

naturally-produced fall chum salmon fry emerge from the gravel (April and May) (WDFW 1995)

However, beginning in the 1970s, some fall-run chum salmon juveniles were released from

hatchery programs into Hood Canal earlier than they would have entered if naturally produced

(Table 23). These fish were released before the end of March, about a month before the

historical peak of natural fall-run fry downstream migration (Koski 1975; Young 1986a,b).

Historically, outmigration to seawater of fry from natural fall-run and summer-run chum salmon

in Big Beef Creek was separated by about 35 days, with nearly 50% of natural summer-run fry

emerging from the gravel and moving downstream by 21 March, and about 50% of natural

fall-run fry emerging by 25 April (Koski 1975). Between 1975 and 1991, an average of 8.1

million chum salmon per year were released from hatcheries in Hood Canal before the end

ofMarch (out of a total of ~37.2 million hatchery fall chum salmon released annually into Hood

Canal) (Table 23). A consequence of these earlier timed releases is that the separation in

outmigration timing between summer and fall chum has been lessened.

This advance in the time of release of hatchery fall-run chum salmon has not been

intentional and may be a consequence of a successful hatchery program and improved hatchery

incubation techniques. Koski (1975) reported that average water temperature during incubation

of natural-run fall chum salmon was about 6°C, with emergence occurring in about 146 days.

WDFW Hoodsport and George Adams Hatcheries incubated chum salmon eggs in constanttemperature (8°C) well water (Fuss and Seidel 1987, Fuss et al. 1993), allowing fall-run chum

salmon eggs to hatch in about 120 days. As early as the mid-1970s, peak abundance of juvenile

chum salmon in nearshore areas of Hood Canal often appeared to be associated with hatchery

releases, sometimes as early as mid-March (Tynan 1997). Therefore, some hatchery fall chum

salmon fry can now migrate downstream almost a month sooner than natural fall-run fry, because
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the warmer hatchery water speeds development and growth.

A second reason why fall chum salmon juveniles could be released in March into Hood

Canal is that the Hood Canal Hatchery complex has been highly successful in producing adult

returns of fall-run chum salmon. Advancement of peak spawn timing is a common development

in successful hatchery programs worldwide and has previously been observed in artificially

propagated coho salmon (Flagg et al. 1995) and steelhead (Tipping 1984). A successful hatchery

program usually increased the number of returning adult spawners throughout the time of the

spawning run. The return of greater numbers of fish early in the run allows hatchery personnel to

complete the hatchery’s egg take earlier in the season (Fig. 34). From 1968 to 1972, the time of

peak spawning of fall chum salmon at the hatchery occurred, on average, the first week of

December. However, 10 years later, the time of peak spawning was reported to occur in midNovember (Fig. 34). A possible consequence of this change in spawning time is that in past

years the separation of 35 days between peak spawn dates of fall- and summer-run chum salmon

reported by Koski (1975) in Big Beef Creek, or the 71-81 day difference reported by Young

(1986a,b) in other streams in Hood Canal, had been reduced to about 14 days (Fig. 34, Table 24).

In recent years no fall chum salmon have been released from hatcheries into Hood Canal in

March (Crawford 1997), and presumably a clear separation between outmigration timing of

summer and early fall chum salmon has been reestablished.

Biologists at WDFW (Crawford 1997) also point out that these differences in spawntiming have not caused an overall change in time or pattern of adult fall chum salmon returning

to Hood Canal or the hatchery. They analyzed the weekly total rack counts at the Hood Canal

Hatchery at Hoodsport from 1953 (first year of operation) through 1996 and averaged the data

over 5-year blocks. These data were then converted to 10, 50, and 90% run completions (Table

25). From Crawford (1997:2):

The 50% completion date has been remarkably stable over the last 36 years (1961-96), occurring

approximately during the period of November 18 through November 30. Discounting the

influence of the of the September/October timed fish during the first two time periods (1953-

1960 and 1961-1965), there is an apparent shift in the timing of the 50% completion date to just

over a week earlier for the fall run fish. Over the last 21 years (1976-1996), the 10%, 50%, and

90% completion timing have shown almost no variability.

As indicated, analysis of the rack count data did show some variation in peaks of chum salmon

returns to the hatchery during the 1950s and 1960s, with returns occurring in September and

October. Crawford (1997:2) suggested the cause of these early peaks might be:

The timing of this [1953-1960 early] peak is consistent with summer chum timing, and the most

likely explanation is that prior to the 1970s, Finch Creek supported a modest summer chum

salmon run. Other possible, but less likely, explanations for the occurrence of summer fish in

Finch Creek would be either straying from the summer chum populations in other Hood Canal

streams, or that these fish resulted from pink/chum hybridization experiments that were

conducted at Hoodsport Hatchery in those years.

There have also been large changes in the numbers of juveniles of summer- and fall-run
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adult chum salmon in Hood Canal prior to April over the last 25 years (Fig. 35). To compare the

ratio of summer and fall chum salmon fry in Hood Canal, we developed an estimate of the

number of summer chum salmon fry in the Canal based upon the number of adult returns. An

average of 1,935 summer-run chum salmon were estimated to have returned per year to Hood

Canal between 1979 (start of decline of summer chum salmon) and 1991 (from WDF et al.

1993). If these fish had a female-to-male ratio of 1.4 to 1 (Young 1986a,b), about 1,128 females

would have been available to spawn in the Hood Canal tributaries. Since the average fecundity

of summer-run females in Hood Canal was estimated to be about 3,500 eggs (Koski 1975), with

mean survival from egg deposition to migration of about 10% (Crawford 1997), we estimate that

about 400,000 natural summer-run chum salmon fry entered Hood Canal prior to April in those

years. Based upon these estimates, the number of hatchery-reared, fall-run juveniles released

into Hood Canal hatchery streams would have outnumbered natural summer-run chum salmon

juveniles by about 20 to 1. As most naturally-produced fall chum salmon in Hood Canal enter

seawater only after the beginning of April (WDF et al. 1993), these calculations suggest that in

recent years, many more fall chum salmon juveniles now enter Hood Canal prior to April than

they did when the majority of fall chum salmon production was natural.

Hatchery fall-run fry that enter Hood Canal prior to April also appear to be larger than

natural summer-run fry monitored by Koski (1975) in Big Beef Creek. Hatchery fall-run fry

released in March averaged between 0.56 and 1.0 g (Fuss et al. 1993), whereas Koski (1975)

estimated that natural summer-run fry averaged about 0.35 g and natural fall-run fish about 0.37

g at the time of freshwater outmigration. Larger chum salmon juveniles in Hood Canal are more

efficient at capturing prey than are smaller juveniles and hence can grow faster (Wissmar and

Simenstad 1988). However, zooplankton, the chief food of juvenile chum salmon, are not

abundant until late spring after the onset of phytoplankton blooms (Strickland 1983). This lack

of phytoplankton in early spring, together with observations from outmigration studies on chum

salmon in Hood Canal (Bax 1982, Bax 1983a; and see “Life-History and Ecological

Information,” p. 34), suggests that chum salmon fry outmigrate quickly. Even so, the less

abundant and physically smaller summer-run juveniles may experience competition for scarce

food from larger fall-run hatchery juveniles. Historically, this competition presumably would

have been avoided because the summer chum salmon would have emerged and entered Hood

Canal before fall chum salmon juveniles were present (Koski 1975).

WDFW (Crawford 1997:32) argued that this focus on the ratio of fall to summer chum

salmon entering Hood Canal misses a more critical issue regarding “potential limitations” on

summer chum salmon. This issue is “what level of all chum stocks migrating prior to March

might be limiting to summer chum?” They suggested that “it is important to recognize the fact

that differences in prey and estuarine migration areas exist between chum migrating as swim-up

fry, and therefore duration of interaction in the estuary, must also be considered.”

WDFW further argued (p. 34):

It seems likely that in some recent years the numbers of hatchery fall chum salmon fry released

prior to April into Hood Canal (as high as 28.6 million in 1993) exceeded the probable numbers

of wild summer chum salmon fry that resulted in any one year from the escapements that have
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occurred between 1968 and 1996. From the tabulated material below, the highest potential wild

summer chum fry outmigration of 8.97 million fish would have resulted from the 1968 parent

escapement of 43,720 spawners. Since this value is derived using an average freshwater survival

of 10%, one could speculate that the highest possible fry value resulting from 43,720 spawners

under ideal freshwater conditions could have been 30.7 million summer chum salmon fry; using

the highest individual survival (34.4%) reported in Bakkala (1970). However, such ideal

conditions are unlikely to have occurred in the last 29 years, and the 28.6 million hatchery fall

chum salmon fry released in 1993 almost surely exceeded the maximum numbers of wild

summer chum fry recruiting to Hood Canal in any year in the same time period.

Is this situation reducing the survival of summer chum salmon through competition for rearing

space or food resources? There is no research specifically on this problem, but the available data

suggest an answer. The early releases of 28.6 million hatchery fall chum fry in 1993 should have

had the greatest, and most observable, impact on summer chum (1992 brood) success of any year

in the data base. The 1992 wild summer chum escapement was only 2,076 spawners, which

would have resulted in a theoretical 420,000 fry recruitment to Hood Canal (see above). The

1992 brood summer chum have in fact been phenomenally successful, making up the majority of

the fish in the large returns in 1995 (age-3 fish) and 1996 (age-4 fish). Contrary to the attempt

. . . of [this Status Review] draft to implicate hatchery chum salmon releases in the decline of

summer chum stocks, a stronger case could probably be made that the early release of large

numbers of hatchery fry buffers wild summer fish against predation losses, and actually increases

survival. With the information at hand, however, it is inappropriate to speculate on the

possibility of either positive or negative impacts of the hatchery fall chum releases [original

emphasis].

Pacific Coast ESU

The Pacific Coast ESU of chum salmon includes a broad geographic range over the

coastal regions of three states, and data on chum salmon in the ESU have been collected from

several tribal, state, and federal agencies. Consequently, the types of data collected vary

considerably. On the Strait of Juan de Fuca, spawning escapement estimates are available only

for Deep Creek and the Pysht River. Tribal harvest data are the only data available for coastal

rivers on the Olympic Peninsula (Fig. 36). Tribal harvests of chum salmon on the coast of the

Olympic Peninsula generally declined prior to the mid-1960s and have been relatively stable at

lower levels since then. On the Quinault River, these estimates of tribal chum salmon harvest

have been converted to run size and escapement using information from the hatchery coho

salmon fishery on the Quinault River. Escapement estimates in Grays Harbor and Willapa Bay

are available for individual stocks (Fig. 37). The spawning escapements for these populations

show no strong recent trends in the more abundant populations but generally appear to be

increasing (Table 20). These trend data are far from exhaustive, but indicate about 35,000

spawners as a lower bound on the escapement of chum salmon on the Washington coast. The

harvest of chum salmon from coastal fisheries combined has averaged 96,000 fish per year from

1988 to 1992 (WDFW 1995). This suggests an abundance level that is an order of magnitude

smaller for the Washington coastal portion of this ESU than for the Puget Sound/Strait of

Georgia ESU, but which is still on the order of 150,000 adults.
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201

Few data are available on chum salmon south of the Columbia River. Tillamook Bay is

the southernmost location that supported substantial chum salmon harvests in recent times.

Intermittent historical landing data are available for Oregon rivers farther south. In response to

declines of the runs in Tillamook Bay, Oregon closed the commercial fishery for chum salmon in

1962. Though the connection between estimates of abundance from spawner surveys and actual

spawner abundance is somewhat tenuous, there has been no substantial increase in the number of

spawners in stream surveys since the halt of commercial fishing. Spawner surveys in the

Tillamook District show substantial year-to-year variability with little correspondence of the

variability among individual spawner surveys (Fig. 38). Estimates of total escapement to the

Tillamook Bay have been relatively stable since the end of the commercial fishery in 1962 (Fig.

39), with a geometric mean of 12,500 spawners for the period from 1987 to 1991. Whiskey

Creek in Netarts Bay also shows no clear trend in spawner counts, although this population is

supplemented with hatchery fish (Fig. 40).

Columbia River ESU

The Columbia River historically contained large runs of chum salmon that supported a

substantial commercial fishery in the first half of this century (Fig. 41). These landings

represented a harvest of more than 500,000 chum salmon in some years. There are presently

neither recreational nor directed commercial fisheries for chum salmon in the Columbia River,

although some chum salmon are taken incidentally in the gill-net fisheries for coho and chinook

salmon, and there has been minor recreational harvest in some tributaries (WDF et al. 1993).

Hymer (1993, 1994) and WDF et al. (1993) monitored returns of chum salmon to three streams

in the Columbia River (Fig. 42) and suggested that there may be a few thousand, perhaps up to

10,000, chum salmon spawning annually in the Columbia River basin. Kostow (1995) identified

23 spawning populations on the Oregon side of the Columbia River but provided no estimates of

the number of spawners in these populations.

An estimate of the minimal run size for chum salmon returning to both the Oregon and

Washington sides of the Columbia River has been calculated by summing harvest, spawner

surveys, Bonneville Dam counts, and returns to the Sea Resources Hatchery on the Chinook

River in Washington (ODFW and WDFW 1995). This suggests that the chum salmon run size in

the Columbia River has been relatively stable since the run collapsed in the mid-1950s (Figs. 43

and 44). The minimal run size in 1995 was 1,500 adult fish.

Summary and Conclusions of Risk Analysis

The ESA 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
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205
206
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208
209
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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 its current status, after taking into

consideration conservation measures that are proposed or are in place. In this review, we did not

evaluate likely or possible effects of conservation measures; 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”).

After evaluating patterns of abundance and other risk factors for chum salmon from these

four ESUs, the BRT reached the following conclusions.

Puget Sound/Strait of Georgia ESU

The BRT concluded that this ESU is neither presently at risk of extinction nor likely to

become endangered in the foreseeable future. Current abundance is at or near historic levels,

with a total run size averaging more than 1 million fish annually in the past 5 years. The

majority of populations within this ESU have stable or increasing population trends, and all

populations with statistically significant trends are increasing.

This ESU encompasses a great deal of diversity in chum salmon life-history patterns,

including summer, fall, and winter runs. The BRT expressed concern that the summer-run

populations in this ESU spawn in relatively small, localized areas and therefore are intrinsically

vulnerable to habitat degradation and demographic or environmental fluctuations. Concern was

also expressed about effects on natural populations of the high level of hatchery production of

fall chum salmon in the southern part of Puget Sound and Hood Canal and the high

representation of non-native stocks in the ancestry of hatchery stocks throughout this ESU. The

BRT was also concerned that although the Nisqually River winter-run population is fairly large

and apparently stable, the Chambers Creek population is much smaller and spawns in a restricted

area. Conservation of populations with all three recognized run-timing characteristics is

important to maintaining diversity within this ESU.

Hood Canal Summer-Run ESU

The BRT concluded that this ESU is in danger of extinction. In 1994, when petitions

were filed with NMFS to list summer chum salmon in Hood Canal, of 12 streams in Hood Canal

identified by the petitioners as recently supporting spawning populations of summer chum

salmon, 5 may already have become extinct, 6 of the remaining 7 showed strong downward

trends in abundance, and all were at low levels of abundance. The populations in Discovery Bay

and Sequim Bay were also at low levels of abundance with declining trends. Threats to the

continued existence of these populations include degradation of spawning habitat, low water

flows, and incidental harvest in salmon fisheries in the Strait of Juan de Fuca and coho salmon

fisheries in Hood Canal.
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In 1995 and 1996, new information was supplied by WDFW (1996) and by the USFWS

(1996) that demonstrated substantial increases of returning summer chum to some streams. A

hatchery program initiated in 1992 at the Quilcene National Fish Hatchery was at least partially

responsible for adult returns to the Quilcene River system, but it appears that 1996 spawners

returning to other streams in Hood Canal were primarily (and perhaps entirely) the result of

natural production. These streams (e.g., the Duckabush, Hamma Hamma, and Dosewallips) have

thus demonstrated considerable resilience in rebounding dramatically from very depressed levels

of abundance in recent years.

The rapid increase of summer-run populations in northern Hood Canal following the

reduction in incidental harvest in 1991 and 1992 is considerably more encouraging than the lack

of response of Columbia River and Tillamook Bay populations even though directed fisheries

were eliminated in those areas many years ago.

There remain, however, serious concerns about the overall health of this ESU. First, the

population increases were limited in geographic extent, occurring only in streams on the west

side of Hood Canal. Several streams on the eastern side of Hood Canal continue to have no

spawners at all, and even returns to the Union River were down in 1996. Union River, located at

the southeastern end of the Canal, was classified as a healthy stock by WDFW in the SASSI

report. In the Strait of Juan de Fuca portion of this ESU, only one of three creeks that have

recently contained summer chum salmon runs showed an increase in adult returns in 1996.

Second, the strong returns to the west-side streams were the result of a single strong year

class (1992), which returned as 3-year-old fish in 1995 and as 4-year-old fish in 1996. Also, the

declines in most of these populations have been severe and have spanned two decades.

Coastwide, many chum salmon populations had unusually large returns in 1995 and 1996, but

there is no indication from the historical record to suggest that such high productivity can be

sustained. In addition, in this ESU, summer chum salmon populations have shown a great deal

of variability in productivity and run size in recent years, and this extreme variability can itself

be a significant risk factor.

Third, greatly reduced incidental harvest rates in recent years probably contributed to the

increased abundance in west-side Hood Canal streams. However, these reductions have been

implemented because of greatly reduced abundances of the target species (coho salmon), rather

than as a conservation measure for summer chum salmon. If coho salmon in the area rebound,

and fishery management policies are not implemented to protect summer-run chum salmon, these

populations would again face high levels of incidental harvest. Finally, harvest of summer chum

salmon in Strait of Juan de Fuca fisheries is primarily incidental to targeted harvest of Fraser

River sockeye salmon. If the run of Fraser River sockeye in the Strait of Juan de Fuca is strong,

and abundance of summer chum salmon is low, the relative impact of incidental take in the

fishery will be stronger on this ESU than it has been in recent years.

In conclusion, although the BRT agreed that the 1995-96 data on summer chum salmon

from this ESU provided a more encouraging picture than was the case in 1996, most members
212

concluded that this ESU was still at significant risk of extinction. A major factor in this

conclusion was that, in spite of strong returns to some streams, summer chum salmon were either

extinct or at very low abundance in more than half of the streams in this ESU that historically

supported summer-run populations. A minority of the BRT concluded that the new data

indicated somewhat less risk of extinction, but that the ESU was still likely to become

endangered in the foreseeable future. Only one member believed that the large returns to some

Hood Canal streams indicated that this ESU as a whole was not at significant extinction risk.

Pacific Coast ESU

The BRT concluded that this ESU is not presently at risk of extinction or endangerment.

An important factor in this conclusion was the abundance of natural populations in Grays Harbor

and Willapa Bay, which presently have escapements of tens of thousands of adults per year.

Elsewhere on the Olympic Peninsula, available data suggest that populations are depressed from

historical levels but relatively stable. Populations in the Tillamook District, the major chumsalmon-producing area on the Oregon coast, are also at much lower abundance than they were

historically, with no apparent trends in abundance. The primary cause of the depressed status of

Oregon coastal populations appears to be habitat degradation.

Although there has been considerable hatchery enhancement in some areas and some

transfer of stocks within this ESU, overall hatchery production has been relatively minor

compared with natural production, and hatchery programs have primarily used fish from local

populations. On the Oregon coast, both public and private chum salmon hatcheries were phased

out by 1990, and all current chum salmon production in this area is natural.

The BRT identified some areas of concern for the status of this ESU. Neither the historic

nor the present southern limit of distribution and spawning of chum salmon is known with

certainty. Thus, it is unclear whether the geographic range has been reduced. Tillamook Bay

populations appear to be stable at low abundance. ODFW has recently increased monitoring

efforts for chum salmon on the remainder of the Oregon coast, but at present the time series is

too short to provide much insight into trends in abundance. Although populations from the

northern Washington coast and the Strait of Juan de Fuca do not appear to be at critically low

levels, their generally depressed status is also a concern and should be monitored. Finally, more

definitive information about the relationship between hatchery and natural fish in Willapa Bay

and Grays Harbor tributaries would allow a more comprehensive evaluation of the viability of

natural populations in these areas.

Columbia River ESU

The BRT concluded that the Columbia River ESU is presently at significant risk, but

team members were divided in their opinions of the severity of that risk. Historically, the

Columbia River contained chum salmon populations that supported annual harvests of hundreds

of thousands of fish. Current abundance is probably less than 1% of historic levels, and the ESU
213

has undoubtedly lost some (perhaps much) of its original genetic diversity. Presently, only three

chum salmon populations, all relatively small and all in Washington, are recognized and

monitored in the Columbia River (Grays River, Hardy and Hamilton Creeks). Each of these

populations may have been influenced by hatchery programs and/or introduced stocks, but

information on hatchery-wild interactions is unavailable.

Because of the well-known aversion of chum salmon to surmounting in-river obstacles to

migration, the effects of the mainstem Columbia River hydropower system have probably been

more severe for chum salmon than for other salmon species. Bonneville Dam presumably

continues to impede recovery of upriver populations. Substantial habitat loss in the Columbia

River estuary and associated areas presumably was an important factor in the decline and also

represents a significant continuing risk for this ESU.

Although current abundance is only a small fraction of historical levels, and much of the

original inter-populational diversity has presumably been lost, the total spawning run of chum

salmon to the Columbia River has been relatively stable since the mid 1950s, and total natural

escapement for the ESU is probably at least several thousand fish per year. Taking all of these

factors into consideration, about half of the BRT members concluded that this ESU is at

significant risk of extinction; the remainder concluded that the short-term extinction risk was not

as high, but that the ESU is at risk of becoming endangered.
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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 the egg nest (redd) until their

yolk sac is absorbed when they swim up and enter the water column.

allele

An allele is an alternative form of a gene that can occur at the same location (locus) on

homologous chromosomes. Many alleles may exist for a particular locus in a population, but a

single individual can carry no more than two alleles at a diploid locus.

allozymes

The alternative forms of an enzyme produced by different alleles andoften detected by

protein electrophoresis.

anadromy

The life-history pattern that features egg incubation and early juvenile development in

freshwater, migration to seawater for adult development, and a return to freshwater for spawning.

Obligatory anadromy: Type of anadromy where migration to seawater is required for survival.

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. Hatchery rearing practices for chum salmon differ

from those of most other salmonid species in that juvenile chum salmon are released directly

from hatcheries as 1- or 2-month-old fed fry, although unfed fry (defined as all fish released at

less than 0.4 g) are also occasionally released. This is possible because chum salmon juveniles

have characteristics of both the fry (young juveniles adapted to freshwater) and smolt (juveniles

that are physiologically prepared to undergo the migration into saltwater) salmonid life-history

stages and can almost immediately enter seawater after the alevin stage.

co-managers

Federal, state, county, local, and tribal agencies that cooperatively manage salmonids in

the Pacific Northwest.

dendrogram

A branching diagram, sometimes resembling a tree, that provides one way of viewing

genetic data to suggest similarities and differences between groups or samples. See multidimensional scaling.

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.
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electrophoresis

Electrophoresis is a physical process that refers to the movement of charged particles in

an electric field. The process has been developed as a analytical tool to detect genetic variation

revealed by charge differences on proteins or DNA. Data provided by electrophoresis can provide insight into levels of genetic variability within populations and the extent of genetic differentiation between them.

escapement

The fish in a run that “escape” all fisheries and return to the freshwater spawning area.

evolutionarily significant unit (ESU)

A “distinct population” of Pacific salmon defined as a “species” under the Endangered

Species Act.

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. The fry stage follows the alevin stage

and in most salmonid species is followed by the parr, fingerling, and smolt stages. However.

chum salmon juveniles share characteristics of both the fry and smolt stages and can enter seawater almost immediately after becoming fry. Hatcheries usually release chum salmon after 1- or 2-

months of feeding as fed fry, although unfed fry (defined as all fish released at less than 0.4 g)

are also occasionally released. Egg boxes allow volitional release juveniles as unfed fry.

genetic distance

A quantitative measure of genetic difference between a pair of samples.

hatchery stock (see stock)

A term that refers to 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.

introgression

Introduction by interbreeding or hybridization of genes from one population or species

into another.

locus (pl. loci)

The site on a chromosome where a gene is found. The term locus is often used more or

less synonymously with gene. See polymorphic loci.

molecular genetic phylogenics

The evolutionary history of an organism or taxonomic group determined by the study of

the molecular aspects of genetic mechanisms and the control of metabolic processes by genetic

material.
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multidimensional scaling

This is a graphing technique that can be used to represent genetic distances between

samples in two or three dimensions, which helps to visualize similarities and differences between

different groups or samples. See dendrogram.

natural fish

A fish that is produced by parents spawning in a stream or lake bed, as opposed to a

controlled environment such as a hatchery.

phenotype

The phenotype is the appearance, or other measurable characteristic, of an organism

resulting from the interaction of the genotype and the environment.

polymorphic locus

If different alleles can be detected at a gene locus, the locus is considered to be polymorphic. If all alleles are of the same type, the locus is considered to be monomorphic. Many population genetic analyses are based on the frequency of different alleles at polymorphic loci.

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 nests called redds, which are dug in the streambed

substrate by the female. Most 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).

Spawning surveys utilize counts of redds and fish carcasses 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.

remote site incubator (RSI)

An egg incubation system developed primarily for chum salmon. RSIs can hold 5,000 to

125,000 eggs.

SASSI

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 and if referenced as “WDF et al. 1993” in this status review.
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semelparous

The condition in an individual organism of reproducing only once in a lifetime.

smolt

verb - To go through the physiological process that prepares a juvenile anadromous fish

to survive the transition from freshwater to saltwater.

noun - A juvenile anadromous fish which has smolted.

Chum salmon differ from most other salmonids in that they have characteristics of both

fry and smolts immediately after swim up.

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.

terminal fisheries

Fisheries near freshwater (usually the mouth of rivers or bays or near a hatchery release

site) where the targeted species is returning to spawn. This definition includes the WDFW term

“extreme terminal fisheries” defined by Crawford (1997, p 24) as “. . . areas where hatchery fish

can be harvested with minimum impact on wild stocks (e.g., the Tulalip tribal hatchery).”

WDFW

Washington Department of Fish and Wildlife (WDFW) is a co-manager of salmonids

and salmonid fisheries in Washington State with WWTIT and other fisheries groups. The

agency was formed in the early 1990s by the combination of Washington Department of Fisheries (WDF) and Washington Department of Wildlife (WDW).

WWTIT

Western Washington Treaty Indian Tribes (WWTIT) is an organization of Native American tribes with treaty fishing rights recognized by the United States government. WWTIT is a

co-manager of salmonids and salmonid fisheries in western Washington in cooperation with

WDFW and other fisheries groups.
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