December 1999

DFO SciencePacific Region Stock Status Report D6-11 (1999)

Background

The Fraser River watershed is the largest Canadianproducer of chinook salmon. Most Fraser-originchinook spawn in the middle and upper regions of thewatershed, the most notable exception being theHarrison River population in the lower Fraser. Chinookreturn to the Fraser throughout the year, with most non-Harrison fish arriving in the lower Fraser between Apriland September. Harrison fish enter the lower Fraserduring September to November.

Fraser chinook spawn primarily from August toDecember, and most spawners are 3, 4, or 5 years old.Fry emerge the following spring and those that spendone or more years in freshwater are called “streamtype,” while those that rear in freshwater less thanone year (typically less than 6 months) are “oceantype.” Harrison fish are unusual in that they are allwhite-fleshed (most non-Harrison chinook are pink-fleshed) and migrate as recently emerged fry directlyto the lower Fraser River and its estuary.

Fraser chinook are comprised of a large number ofpopulations. For management purposes, they aredivided into 4 major geographical stock complexes, and3 timing groups. The geographical stock strata are:upper Fraser (those upstream of Prince George andincluding Nechako), middle Fraser (downstream ofPrince George but excluding the Thompson), theThompson, and the lower Fraser (numericallydominated by fall-returning Harrison-origin fish). Thetiming groups are categorized into 3 seasonal runs. Theearly or spring run migrates through the lower FraserRiver before July 15; the summer run migrates through

Fraser River Chinook Salmon

the lower Fraser between July 15 and Sept. 1.; and thefall chinook, mostly originating in the Harrison andChilliwack, enter the lower Fraser after Sept. 1. Thegeographical and timing complexes overlap. Forassessment purposes, geographic stock aggregates aregrouped according to their timing and life history.

Since the early 1980s, the principal hatcheriesenhancing Fraser chinook have been the Chehalis andChilliwack (lower Fraser), Eagle, Shuswap Falls,Clearwater, Deadman Creek, and Spius Creek (allThompson) and the Quesnel (mid-Fraser) and Stuart/Narcoslie (upper Fraser). In recent years, theClearwater, Eagle, Quesnel, and Stuart facilities haveclosed. Some enhancement also occurs at small facilitiesthroughout the watershed. Enhancement is thought tohave a relatively small effect on the total numbers ofchinook returning to the Fraser, although the effectson certain watersheds, such as the Nicola watershed,which is enhanced by the Spius Creek Hatchery, andthe Chilliwack River, which is enhanced by theChilliwack Hatchery, can be significant.

Map of Fraser River watershed.

Driftwood River

Takla Lake

Middle R.

Trembleur Lake

Stuart Lake

Stuart River

Nadina R.

Francois Lake Fraser LakeRiver

QUESNEL

WILLIAMS LAKE

LILLOOET

Bow

ron River

Mitchell River

Quesnel

Quesnel

River

LakeRiv

erF

rase

r

Chilcotin

RiverChilko R

iver

Taseko Lakes

Tase

ko R

ive

r

Bridge R.

Anderson Lake

Birkenhead R

.

Lillooet

River

Nahatlatch R.

Col

dwat

er R

.

Harrison Lake

Coq

uiha

lla R

.Stave R

.

Stave Lake

Pitt Lake

U. P

itt R.

VANCOUVER

Hell's Gate

NORTH BEND

Nicola River

Kamloops L.

KAMLOOPS

Scotc

h C

r.

L. Shuswap R.

M. Shuswap R.

Mabel Lake

Mara Lake

Eagle River

Adams Lake

Momich R. Ada

ms

Riv

er

N. Barriere LakeN

orth

Raf

t Riv

er

Strait of Georgia

CANADA U.S.A.

Shuswap Lake

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0

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40

50miles

80km

Johnstone Strait

Chilko Lake

Fraser

River

(upper)

Horsefly R.

South Thompson R

iver

VANCOUVER ISLANDHOPE

CHILLIWACKChilliwack R.MISSION

Chehalis R.

Seton Cr.

Gates Cr.

Tho

mps

on

R

iver

Bon

apa

r te

R iver Sey

mour

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Nec

hako

Tho

mps

onR

iver

Chilako R.

West Road R

iver

Harrison R

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Vedder R.

Cottonwood R.

PRINCE GEORGE

Cle

arwater R

.

Willow

R

ive r

Bowron Lake

Sockeye Salmon Distribution

FRASER RIVER WATERSHED

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Pacific Region Fraser River Chinook Salmon

The Fishery

Under the 1985 Pacific Salmon Treaty, Canadaand the U.S. committed to halting the decline ofchinook escapements. Catch ceilings wereestablished for major chinook fisheries fromAlaska to British Columbia and various time andarea closures were implemented. Since 1994,additional fishery management changes have beenmade to increase the size of spawning stocks ofupper Fraser River and other chinook stocks.These have included reduced catch ceilings forthe troll fisheries, and increased minimum sizelimits and reduced bag limits for the recreationalfishery. In 1997 and 1998, Canadian oceanfisheries were dramatically reduced to lessenimpacts on Thompson basin coho, further alteringmarine catch distributions and lowering oceancatches of Fraser chinook.

Estimates of the distribution of Fraser chinookare based on data gathered during coded-wire tag(CWT) studies. Because of recent changes in thefishery, catch distribution results were dividedinto pre- and post-1997 when there were sufficientdata to do so. Recoveries for all tags were groupedinto one of 7 recovery strata:

All CWT information is presented as “estimatedtags,” – the numbers of tags recovered in the time-area-fishery stratum– expanded to account for thecatch/sample ratio. In many instances, samplesizes are small, and our understanding of chinookdistribution is limited as a consequence. FirstNations fisheries in the Fraser have not been

adequately sampled for CWTs, and are thereforeexcluded from the recovery strata.

Spring-Run Chinook

Recoveries of upper Fraser spring-run chinookwere rare considering the numbers of CWTsapplied, and these tags were recovered in all strata(Fig. 1). Most tags were from the WCVI/Entryarea. Early returning chinook to the upper Fraserare rarely available to coastal fisheries during July,but are available to entrance and recreationalfisheries in May and June during their returnmigrations.

Fig. 1. Distribution of estimated CWT recoveries ofupper Fraser spring-run chinook before (n=875), andduring or after (n=65), 1997.

There currently are no CWT application programsfor mid-Fraser spring-run chinook. A total of 504CWTs were estimated to have been recoveredcoastwide from earlier tagging. Similar to upperFraser springs, most recoveries occurred in theWCVI/Entry area, and many of these were caughtin the Juan de Fuca recreational fishery duringJune.

A greater proportion of chinook originating in theNorth and South Thompson were recovered inthe north and central recovery areas than occurredfor mid and upper Fraser spring chinook (Fig. 2).Freshwater sport recoveries were almostexclusively in the lower Fraser River bar fishery,as there were no terminal sport fisheries targettingthese (marked) stocks.

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Recovery Stratum Fishery / Mark Recovery AreasIncluded

North, Central All northern and central net, trolland sport fisheries

WCVI, Entrances All WCVI, Johnstone St. and Juande Fuca St. fisheries

Inside All Georgia Strait troll, net andsport fisheries

Fraser River Commercial Fraser gillnet, seine, and testfisheries

Fresh Water Sport All Fraser River recreationalfishery recoveries

Alaska Alaskan troll, seine, and gillnetrecoveries

Washington / Oregon Washington, Oregon andCalifornia fisheries

3

Pacific Region Fraser River Chinook Salmon

Fig. 2. Distribution of estimated CWT recoveries ofNorth and South Thompson spring-run chinook(n=485).

Prior to the closure of many of the outsidecommercial fisheries, recoveries of lowerThompson springs occurred in all strata with theexception of Alaska, but were most common inthe WCVI/Entry area (Fig. 3). From 1997 on, thenumber of recoveries in all fisheries declined, withthe exception of the terminal and lower riverrecreational fisheries. While these sport fisheriesrecovered almost 70 % of all lower ThompsonCWTs during 1997-98, they represented only 87tagged fish, of which 65 were caught in theterminal recreational fisheries at the mouth of theNicola River.

Early returning spring chinook from theBirkenhead River (upper Harrison system) had avery different marine catch distribution than anyother Fraser River spring chinook population (Fig.4). Most Birkenhead chinook, one of the earliestreturning populations to the Fraser, wererecovered in Alaskan fisheries. Recoveries insidethe Strait of Georgia occurred during early springrecreational fisheries.

Fig. 4. Distribution of estimated CWT recoveries ofBirkenhead spring-run chinook (n=398).

Summer-Run Chinook

Recoveries of upper Fraser summer-run chinook(mostly Stuart) occurred most frequently in theentry fisheries and off the west coast of VancouverIsland, with the southwest Vancouver Island trollfishery and Juan de Fuca net fisheries being theprimary contributors (Fig. 5). Few recoveries werereported in recreational fisheries and recoveriesin the Fraser River commercial fishery occurredmostly during sockeye openings.

Recovery information for mid-Fraser summerchinook is presented in aggregate for mid-Fraserpopulations pre-1997, and for Quesnel River fishin 1997 and 1998 (Fig. 6). Mid-Fraser summerswere, prior to 1997, recovered often in entrancenet fisheries, although more recently, mostrecoveries occurred in northern and Alaskanfisheries, and in directed sockeye fisheries in theFraser. Alaskan recoveries occurred primarily introll fisheries. Very few recoveries were reported

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Fig. 3. Distribution of estimated CWT recoveries oflower Thompson spring-run chinook before (n=3692),and during or after (n=133), 1997.

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Pacific Region Fraser River Chinook Salmon

in the Strait of Georgia fisheries or in freshwatersport fisheries.

Fig. 5. Distribution of estimated CWT recoveries ofupper Fraser summer-run chinook before (n=506), andduring or after (n=49), 1997.

No North Thompson basin summer chinookCWTs have been recovered since 1996. Up toand including 1996, there were an estimated 3,400recoveries of tagged North Thompson chinook,from the Raft, Clearwater and the NorthThompson River itself. Recoveries were mostcommon in the WCVI/Entry and in north-centralarea fisheries.

Fig. 6. Distribution of estimated CWT recoveries of mid-Fraser summer-run chinook before (n=2150), andduring or after (n=195), 1997.

Fig. 7. Distribution of estimated CWT recoveries ofSouth Thompson summer run chinook before (n=9914),and during or after (n=472), 1997.

South Thompson summer chinook appeared tohave a more northerly marine catch distributionthan other Fraser summer-run populations (Fig.7). A large proportion of South Thompson-originsummer chinook were recovered in the northernwaters of B.C. and in the Alaskan fisheries. Mostfreshwater sport recoveries occurred in theterminal sport fisheries on the lower and mid-Shuswap River.

Fall-Run Lower Fraser Chinook

To understand the distribution of Harrisonchinook in the marine fisheries, we utilizedinformation from chinook tagged and releasedfrom the Chehalis River Hatchery. It is notpracticable to tag adequate numbers of naturallyproduced juvenile chinook leaving the HarrisonRiver due to their small size. Since 1981, Harrisonchinook have been enhanced at this hatchery,which is located on a tributary of the lowerHarrison River.

Harrison-origin (Chehalis) chinook salmon werepredominantly coastal in their marine distribution.Most recoveries occurred in southern fisheries inthe WCVI/Entry area, the Strait of Georgia, andWashington waters (Fig. 8).

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Pacific Region Fraser River Chinook Salmon

Fig. 8. Distribution of estimated CWT recoveries forHarrison (Chehalis) fall-run chinook before (n=24166),and during or after (n=544), 1997.

Resource Status

Many of our inferences about the status of Fraserdrainage chinook are based on spawnerescapement data. Most data are from visualsurveys, which are generally biased to low countsalthough they are considered reasonably precise.Counting fences and mark-recapture projectsoccur for some systems, although are rarely lastlong enough to examine time series ofescapements.

Included in the upper Fraser complex areapproximately 16 stream populations that spawnin the Fraser River and its tributaries upstream ofPrince George, including fish from the McGregor,Nechako, Stuart, and Torpy River systems. Inmost recent years, mark-recapture estimates havebeen produced for the Stuart River, area-under-the-curve estimates for the Nechako, and fencecounts for the Salmon River (Prince George). Inthe mid-Fraser complex are 12 populationsdownstream of Prince George, including fish fromthe Chilko, Chilcotin, and Quesnel River systems.In both complexes, estimates are generatedprimarily from aerial overflight data and bydividing the peak count by 0.65.

Within the Thompson are fish spawning intributaries to the lower Thompson Riverdownstream of Kamloops (Deadman River andNicola River systems), 6 tributaries to the North

Thompson plus the North Thompson itself, and7 tributaries to the South Thompson, includingthe lower and middle Shuswap, and the SouthThompson. Most escapement estimates areproduced by expanding peak visual surveyestimates, but counting fences or fishways areutilized in the Eagle, Salmon, Bonaparte, andDeadman Rivers. The Nicola River is the site ofa cooperative enumeration project with the localFirst Nations.

The Harrison River population (lower Fraser) hasbeen consistently enumerated by a mark-recaptureproject since 1984. Chinook escapements to theHarrison were also estimated from 1951 to 1986by visual surveys. Unfortunately these estimateswere largely subjective and visual estimates inthe latter years were influenced by the ongoingmark-recapture programme. It has therefore notbeen possible to adequately reconstruct theHarrison time series prior to 1984.

The Fraser escapement time series is numericallydominated by the Harrison (Fig. 9). Returns tothe Harrison have been highly variable andwithout any overall trend. Non-Harrison stockaggregates increased in numbers commencing inthe mid-1980s. Since 1995, escapements of theThompson aggregate appear to have increasedmore than did upper and mid-Fraser populations,likely due to coho conservation measures anddeclines in late sockeye fisheries.

An examination of the non-Harrison dataseparated into the major timing groups is moreinformative. While all early returning aggregatesappeared to increase numerically in the mid-1980s, the increase was largest in the upper Fraser(Fig. 10). Early timed runs to the Thompson have

Fig. 9. Estim a ted numbers of chinook salmon returning to

major areas of the Fraser River w a tershed

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250,000

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6

Pacific Region Fraser River Chinook Salmon

been trending downwards in the most recentyears, while early runs to the upper and mid-Fraser, while highly variable, have been withouta pattern.

Summer aggregates also increased numericallyin the mid 1980s (Fig. 11). Summer runs to theThompson have apparently been doing well thelast several years while escapements for othersummer stock aggregates have been relativelyunchanged.

Outlook

Forecasts of the next year’s escapement for wildspawning Harrison chinook are made annuallyand a forecast methodology for Harrison-originchinook spawning in the Chilliwack River isunder development. As part of the mark-recaptureescapement estimation programme at theHarrison, estimates of spawner escapements arepartitioned by age class. “Sibling regression” usesthe numbers of younger spawners in one year topredict the numbers of older spawners insubsequent years. This method requires that

fishery exploitation rates remain constant overtime. The method has worked well in most years,but significantly underestimated the returns in1998, when exploitation rates were much lowerthan average. The forecast for 1999 is for about85,000 spawners in the Harrison (jacks excluded)which is about 80 % of the average escapementduring the last 15 years. As well, the numbers offemales returning in 1999 may be low.

The longer term prognosis for fall-returning whitechinook is uncertain. Escapements of enhancedHarrison origin fish to the Chilliwack River havegenerally increased since the population wasestablished, and in 1995 and 1997 they wereestimated to exceed the numbers of naturallyspawning chinook in the Harrison. Within theHarrison River, all chinook spawn in a 16.5-kmstretch of river downstream from Harrison Lake.The fry emigrate downstream shortly afteremergence and use side channels and sloughs ofthe lower Fraser River and its estuary as theirpredominant rearing locations. The HarrisonRiver is used for log transport and storage andthe lower Fraser River and estuary is affected innumerous ways by the city of Vancouver. Thewild population is clearly vulnerable todegradation of these important habitats.

Quantitative forecasts are not made for spring andsummer timed stock aggregates. To provideforecasts, better annual sampling for agestructures, more quantitative estimates ofspawning escapements, and improved in-rivercatch information separated by population and ageare required. For spring populations (Fig. 10),recent spawning escapements have been generallyhigher than during the 1970s but the recent trendin the aggregate escapement index has beendownwards. Researchers are concerned about thestatus of this group, especially the earliestcomponents of the run, including the Spius Creek,Coldwater River, Birkenhead River, and theUpper Chilcotin River populations. Escapementsof the summer stock aggregate (Fig. 11) havegenerally been up the last 3 years although therehas been significant variability amongst streams.Escapements of mid and upper Fraser summer

Fig. 10. Estimated numbers of spring-run chinook returning to major areas

of the Fraser River watershed

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71 73 75 77 79 81 83 85 87 89 91 93 95 97

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F i g . 1 1 . E s tim a te d n u m b e rs o f su m m e r-ru n c h i n o o k

r e tu r n i n g to m a j o r a r e a s o f th e F r a se r R i v e r

w a te rsh e d

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Pacific Region Fraser River Chinook Salmon

stock aggregates have often been down in recentyears, while returns of late timed South Thompsonpopulations are strong.

It is clear that upriver chinook populations havebenefited from reductions in ocean harvests.Canadian marine fishery exploitations weresignificantly reduced in 1985 in accordance withthe rebuilding programme under the PacificSalmon Treaty and all non-Harrison stockaggregates appeared to increase (Figs. 9-11).Recent fishery reductions, designed in part toconserve upriver populations of Fraser coho andsockeye, have also benefited many Fraser chinookpopulations, especially summer runs of chinookin the Thompson. In-river harvests of early-runchinook may have delayed their rebuilding.

The long-term prognosis of upriver stocks ofFraser chinook is uncertain. It is not clear whetherthe freshwater carrying capacity for thesepopulations has been achieved. Freshwater habitatdegradation is a concern in some watersheds.Meanwhile, interim escapement goals, establishedfor all major Fraser chinook stock aggregatesabout 15 years ago, are currently being reviewed.Many upriver populations are well above thesegoals, which may have been too conservative,while the Harrison River population has neverreached its target. Researchers plan to use habitat-based approaches for upriver populations whilea stock-recruit approach will be used for theHarrison to establish new target escapements.

For More Information:

Contact:Jim IrvineStock Assessment DivisionPacific Biological StationNanaimo, BC V9R 5K6Tel: (250) 756-7065Fax: (250) 756-7138E-Mail: irvinej@pac.dfo-mpo.gc.ca

Or

Contact:Richard Bailey

Stock Assessment DivisionFisheries and Oceans1278 Dalhousie DriveKamloops, BC V2B 6G3Tel: (250) 851-4814Fax: (250) 851-4951E-Mail: baileyri@pac.dfo-mpo.gc.ca

Or

Contact:Rick SempleStock Assessment DivisionFraser River Interior Office100 Annacis Parkway, Unit #3Delta, BC V3M 6A2Tel: (604)-666-3193Fax: (604)-666-7117E-Mail: sempler@pac.dfo-mpo.gc.ca

This report is available:

PSARC SecretariatPacific Biological StationNanaimo, BC V9R 5K6Phone: (250) 756-7208Fax: (250) 756-7209E-Mail: psarc@pac.dfo-mpo.gc.caInternet Address: (www.dfo-mpo.gc.ca/csas)

ISSN 1480-4913 (for English series)ISSN 1480-4921 (for French series)

La version française est disponible àl’adresse ci-dessus.

Correct citation for this publication

DFO, 1999. Fraser River Chinook Salmon. DFOScience Stock Status Report D6-11 (1999).