364;

SALMON RUNS -

UPPER COLUMBIA RIVER, 1956-57

Marine Biological Laboratory

WOODS HOLE, MAtJS.

SPECIAL SCIENTIFK REPORT-FISHERIES Na 364

United States Department of the Interior, Fred A. Seaton, Secretary
Fish and Wildlife Service, Arnie J. Suomela, Conunissioner
Bureau of Commercial Fisheries, Donald L. McKernan, Director

SALMON RUNS - UPPER COLUMBIA RIVER. 1956-57

by

R. R. French and R. J. Wahle

United States Fish and Wildlife Service
Special Scientific Report--Fi8herie8 No. 364

Washington, D. C.
October I960

CONTENTS

Page

Introduction 1

Salmon runs past Rocky Reach Dam site 2

Time and size of runs passing Rocky Reach Dam site Z

Chinook salmon..... 3

Blueback sedmon 3

Steelhead trout 6

Silver salmon 7

Rate of travel--Rock Island to Zosel Dcun 7

Distribution of spawners in tributaries above Rocky Reach Dam

site 8

Chinook salmon 8

Blueback salmon 14

Siunmary and conclusions 14

Literature cited 15

FIGURES

1. Columbia River watershed between Rock Island and Grand

Coulee Dams iv

2. Chinook salmon p>assage at Rock Island Deim, 1954-57

(smoothed by 5) 4

3. Blueback salmon counts at Rock Island Daun, 1954-57 5

4. Steelhead trout counts at Rock Island Dam, 1954-57 (totals by

weeks) 6

5. Areas of spawning in the Entiat River 9

6. Areas of spawning in the Methow River system 10

7. Areas of spawning in the Okanogan and Similkameen Rivers 11

8. Distribution of tagged chinook salmon above Rocky Reach Deun

site by period of tagging at Rock Island Dam, 1954 and 1955. 12
9- Distribution of tagged chinook salmon above Rocky Reach Daxn

site by period of tagging at Rock Island Dajn during 1956 13

TABLES

1. Totals of streami survey counts and counts of spring and summer

chinook salmon passing Rock Island Dam - 1956 and 1957....

2. Spawning ground surveys above Rocky Reach Dan:i site 1956-57.

Peak counts (live and dead) of chinook and blueback salmon .

ui

Hotcher

Figure t.— Columbia River watershed between Rock Island and Grant Coulee Dams.

IV

SALMON RUNS - UPPER COLUMBIA RIVER, 1956-57

by

R. R. French and R. J. Wahle

ABSTRACT

Important runs of salmon pass Rocky Reach Dann site on the
Columbia River. The escapement of chinook salmon past Rocky
Reach in 1957 was estimated to be approximately 11,000 spring
chinook which spawn in the small remote tributaries and 6,000
summer chinook which spawn in the large tributaries of the Columbia
River.

Blueback salmon passing Rocky Reach Dam site in 1956 and 1957
accounted for approximately 72 and 60 percent of the escapement
passing Rock Island Dam, or about 67,000 fish in 1956 and 43,000
fish in 1957. They spawn in the Okanogan River in Canada. The rate
of travel of blueback salmon was 13.5 miles per day.

INTRODUCTION

Upon the comipletion of Grand Cou-
lee Daxn in 1938, anadromous fish runs
were blocked from about 1,140 lineal
miles of spawning and rearing areas
above the dam (Fish and Hanavan,
1948). At that time anadromous fish
were transplanted to the tributaries
between Rock Island and Grand Coulee
Dams. These tributaries and the Co-
lumbia River between Chief Joseph
and Rock Island Dams, totaling about
340 lineal miles of stream, now provide
the spawning and rearing areas for
anadromous runs passing Rock Island
Dzim (fig. 1).

Note.--R, R. French and R, J. Wahle, Fishery Re-
search Biologists, Bureau of Commercial Fisheries.
U. S. Fish and Wildlife Service, Seanle, Wasliington.

Chelan County Public Utility Dis-
trict No. lis engaged in the construc-
tion of Rocky Reach Dam located ap-
proximately 21 miles aboveRock Island
Dam. This dam poses problems for
passing anadromous fish runs upstream
and downstream and for maintaining
adequate spawning areas if major
spawning areas are eliminated by flood
waters of the forebay. The Fish and
Wildlife Service agreed to provide basic
biological information on the present
salmon escapements of chinook salmon
(Oncorhynchus tshawytscha), blueback sadm-
on (Oncorhynchus nerka), silver salmon
(Oncorhynchus kisutch), and the steelhead
trout (Salmo gairdneri). S tudi e s on the
steelhead were limited to examination
of their abundance and times of arrival
at Rock Island Dam. This basic

biological information will also provide
a basis for comparisons of the runs in
future years. During 1956 and 1957 the
Service made studies on ( 1 ) the size and
time of migration of various species
past the dam site, (2) the rate of travel
of migrating fish pastRocky Reach Dam
site before the dam is built, and (3)
tributary spawning areas used by
various segments of the run.

To accomplish these objectives we
have used the fish-count data at Rock
Island Dam for determining the size
and time of escapements atRocky Reach
Dam site 21 miles upstrecim. Tagging
experinnents provided information on
the rate of travel of blueback Sedmonj
and strejmi surveys in which spawning
salmon were counted in the streams
were used for obtaining salmon spawn-
ing data.

Financial support for this study
was provided by Public Utility District
No. 1 of Chelan County, Washington.

SALMON RUNS PAST ROCKY REACH
DAM SITE

Over the years salmon become
specifically adapted to their environ-
ment and become established in certain
strecims and watersheds in varying
abundance. The purpose of the in-
vestigation was to determine the abun-
dance of these upriver runs and the
arrivcil times of these runs at the new
Rocky Reach Dam site.

Since it was not possible to count
fish there, the arrival times of the
runs at Rocky Reach Dam site was
estimated from a study of the arrival
times of fish at Rock Island Dam 21
miles downstream. The daily counts
of salmon and steelhead were graphed
to show the seasonal pattern of migra-
tion, and by applying known rates of
travel of different species, we were
able to estimate their arrival times
at Rocky Reach Dam site.

The size of escapements passing
Rocky Reach Dam site was estimated
by applying to the Rock Island Dam
count the ratio of spawners observed

in spawning streams above and below
Rocky Reach Dam site. Totals of peak
salmon counts for the Wenatchee River
system and river systems above Rocky
Reach were compiled, and a ratio ob-
tained of the number of spawners found
in the two areas. This ratio was then
applied to the escapement counted at
Rock Island Dam to obtain an estimate
number of fish passing Rocky Reach
Dam site. For example, if 1,000
spawners were counted in all streams
and 700 were observed in streams above
Rocky Reach, then 70 percent were
deemed to have passed Rocky Reach.
Thus, if 10,000 Chinook had been counted
at Rock Island Dam, 7,000 fish would
be estimated as having passed Rocky
Reach Dam site.

Stream surveys were made peri-
odically by foot or by boat and the num-
ber of fish of each species of salmon
was recorded. Peak counts, which were
the largest number counted in any one
survey, becamie the basis of compari-
sons. Survey counts do not represent
the total number of spawners present in
a stream in a season. Such information
cannot be obtained from stream sur-
veys. However, as these survey counts
were taken in the Scune manner and by
the same personnel, we feel they gave
a usable estimate of the comparative
abundance of spawners in the different
streams.

Time and size of runs passing Rocky
Reach Dam site

Blueback salmon were found to
migrate upriver at the rate of 13.5
miles per day (see later section); thus,
they would be expected to pass Rocky
Reach Dam site, 21 miles upstream
from Rock Island Dam, by the second
day after passing Rock Island Dam.
Chinook salmon in the Snake River
were reported to naigrate at rates of
13 and 15 miles per day.* Either of
these rates indicates that chinook runs
passing Rock IslandDam would pass the

Thompson, Robert N„ James B. Haas, Lawrence M.
Woodal, and Edwin K, Holmberg. 1958. Results of a tagging
program to enumerate the numbers and to determine the
seasonal occurrence of anadromous fish in the Snake River
and its tributaries. Fish Commission of Oregon, Contract
Report DA 35-026-eng-20609, Portland, 202 pp. Processed,

Rocky Reach site Ij or Z days later.
Therefore, the arrival times of the
blueback and chinook runs at Rock
Island Dam have been used as the ap-
proximate times the runs would be ex-
pected at Rocky Reach Deun site.

The rates of travel of individual
steelhead were found to vary widely in
the Columbia River between Bonneville
and McNary Dams. Schoning, Johnson,
and Merrell, in an unpublished report,
found that these rates varied from 1.9
to 14.6 miles per day.' Thus steelhead
could be expected to pass Rocky Reach
from Z to IZ days after passing Rock
Island Dam.

Chinook salmon. --The season of
passage and the number of chinook
salmon passing Rock Island Dam are
given in figure Z. Chinook runs in the
Columbia River are composed of
spring, summer, and fall segments ac-
cording to the time they enter the river.
Each season, the chinook salmon escap-
ing the fishery appear during the same
time period at Rock Island Dam; spring
chinook pass in May and June, summer
chinook pass in July and August, and
fall chinook make their appearance
after August. The spring and summer
chinook runs are fairly well defined by
their period of passage at Rock Island
Dam. The fall run, however, is not
clearly marked and appears as a minor
part of the escapement late in the
season. Fish and Hanavan (1948) re-
ported on the bimodality of the chinook
runs at Rock Island Dam and reported
that the spring run apparently termi-
nates during early July. They did not
report on the existence of a fcill run,
but evidence of a fall run atRock Island
Deim is presented in a later section of
this report. Considerable overlap of the
three segments occurs. All three
groups should be expected at Rocky
Reach Dam site during the same time
period as at Rock Island Dam.

Spawning ground counts above and
below Rocky Reach Dajn site and counts

^Schoning,. Robert W., Donald R.Johnson, and Theodore
R. Merrell. 1950. The expected appearance of certain runs
of Columbia River salmon at McNary Dam. Fish Commis-
sion of Oregon. February, unpublished report., IS pp.
Portland.

of spring and summer chinook at Rock
Island Dam are given in table 1. We
found that 77 percent of the spring
chinook counted in 1956 and 65 percent
in 1957 were in areas above Rocky
Reach. In 1957 this meant that about 65
percent of the spring run counted over
Rock Island, or approximately 11,000
fish, were estimated as having passed
Rocky Reach Dam site. Twenty-one
percent in 1956 and 19 percent in 1957
of the summer chinook were counted
in areas above Rocky Reach Dam site.
Thus, in 1957 the population of summer
chinook passing Rocky Reach was es-
timated at 6,000 fish. Counts of spring
and summer chinook runs passing Rock
Island DaJTi in 1956 were not reliable
because of the overlap of the runs that
season. The reason for this overlap is
discussed in a following section.

Fall chinook salmon spawn in the
Columbia River in the limited area be-
tween Rock Island Dami and Rocky Reach
Dam site, and on extensive spawning
riffles above Rocky Reach. Determina-
tion of their abundance in this stretch
of the main Colunibia River was as-
signed to another fishery agency.

Blueback s almon.--Bluebac k
salmon, first appearing at Rock Island
Dam in early July, show a peak of
abundance around July 15 to Z5. (see
figure 3.) To determine the size of the
blueback escapement passing Rocky
Reach Dam site we have used the sea-
sonal counts of blueback at Tumwater
Dam (fig. 1) as the number of blueback
entering the Wenatchee River system.
The remaining part of the run, or Rock
Island Dam counts minus the Tumwater
Dam counts, has been used as the es-
timated number passing Rocky Reach
Dam site. This procedure was in pref-
erence to usirig stream surveys for
obtaining ratios of blueback salmon in
the two areas. In recent years the
Okanogan run has been the larger of
the two runs. Counts of the Wenatchee
River run at Tumwater Dam for 1954-
57 have ranged from 28 to40 percentof
the total escapement counted at Rock
Island Dam. The remaining 60 to 72
percent of the blueback runs for these
years has been attributed to the
Okanogan run. The estimate of the blue-
back run passing Rocky Reach Dam site

lO C\l lO to
00 — OD —

cj_ r--_ q. r>-_
n Hi in O

fO CM M "O

* lO <o f^
m ir> lO m
o> a> o> ff>

■s

o
o

01

c
o

E

HSU dO bl3SNnN

Table 1. — Stream survey and Eock Island Dam counts of spring and summer

Chinook, 1956-57

Chinook salmon counts •'•

-Area

1956 2

1957

Spring

Sinraner

Spring

Summer

Counts above Rocky Reach Dam site

Counts below Rocky Reach Dam site
( Wenatchee River system)

Total survey counts

Percentage above Rocky Reach

Counts at Rock Island Dam

1,093

334

1,427

77

575

2,147

2,722

21

3,097

1,672

4,769

65

16,631

1,787

7,407

9,194

19

29,914

''" The week ending June 25 was the division date separating spring and summer Chi-
nook; the week ending August 27 was the division date for summer and fall chinook.
2 In 1956 overlap of runs precluded separation of sprine and siimmer chinook.

20,000

19,000 ■

1 8,000

17,000

16,000-

15,000 -

14,000

13,000

^ 12,000
to

^ 11,000-
o 10,000

tr
111
m

9000
8000
7000
6000
5000
4000
3000
2000
1000

I ; V

1954 91.234

1955 155.055

1956 92,443

1957 71,261

15 20
JULY

15 20
AUGUST

Figure 3.--Blueback salmon counts at Rock Island Dam. 1954-57.

5

in 1956 was 67,000 fish, or 72 percent
of the Rock Island Deun counts. In
1957 the estimate was 43,000 blueback
or 60 percent of the Rock Island Dam
counts.

Steelhead trout. --Two groups of
steelhead runs pass Rock Island Dam,
the spring run, which pass in mature
condition and are destined to spawn that
same season, and the fall run, which
pass Rock Island from July through

700

October and forms the larger group
of the two, figure 4. As counting at
Rock Island Dam is not continuous dur-
ing winter months but consists of
periodic counts at the three ladders,
the migration during this period is not
fully known. These periodic counts at
the various ladders at Rock Island have
revealed some movement of steelhead
throughout the winter months. Pre-
sumably, spawning of steelhead occurs
throughout the accessible river systems

600

500

X

400-

ir
ui
o

2

300

200-

100

1954
1955

N = 4578
N = 3200
N = 1531

1956

1957 N =3927

( Counts are for periods of confinuous
counting at the 3 ladders.)

-•^..^p,,,, •••- — ^-~
7 14 21 28 4 II 18 25 2 9 16 23 30 6 13 20 27 3 10 17 24 I 8 15 22
MAY JUNE JULY AUGUST SEPTEMBER OCTOBER

Figure 4.--Steelhead trout counts at Rock Island Dam, 1954-57. (totals bf weeks).

6

above Rock Island Dcun, although no
spawning ground counts were obtained.
Sizes of steelhead rxins passing Rocky
Reach were not estimated.

Silver salmon. --Silver salmon are
few in this area at the present time.
Total yearly counts of silver Scilmon
at Rock Island Daun for 1954-58 have
ranged from 40 to 94 fish. These fish
p>ass Rock Island Dam during Septem-
ber, October, and November. Formerly
silver salmon were abundant. Records
show that approximately 6 to 7 million
silver salmon eggs were taken annually
from the Wenatchee River alone during
the years 1899 to 1902. From 1910 to
1920 the nvimbers of silver salmon eggs
taken annually at the Methow River
hatcheries ranged from a few thousand
to nearly 3 million (Washington State
Department of Fisheries, 1899-1920).
These silver salmon runs, though of
little value now, could p>ossibly be im-
proved.

Rate of travel — Rock Island to Zosel
Dam

The rate of travel for blueback
Scilmon between Rock Island Dam and
Zosel Dam (figure 1) was determined
prior to the building of Rocky Reach
Dam in order to ascertaun if delays
in migration result from the new dam
now under construction. The question
of delay and its effect upon migrating
salnrion has long been a matter of con-
jecture among fishery biologists. The
actual effect of a short-term delay or
the accumulated effect of several short-
term delays to migrating salmon is
not known. The most notable example of
the effect of a delay in migration has
been the blockade at Hell's Gate on
the Fraser River. Here, fish that were
delayed longer than 14 days did not
reach the spawning ground. During these
experiments fish captured, tagged, and
liberated were often recaptured below
the gate and the interval between cap-
tures was termed delay (Talbot, 1950).
In reference to the Columbia River and
many dams now built or contemplated
along salmon migration routes, one of
the problems is whether dams cause
delays over and above the effects of

pre-existing conditions; and if delays
are caused, what might be the cumula-
tive effect of many dams.

Knowing Rocky Reach Dam was to
be constructed we decided to determine
the rate of travel of salmon through this
stretch of river before construction.
Then in the future it miay be possible
to determine if Rocky Reach Dam de-
lays passage of migrating fish.

In 1957, to determine the rate of
travel through this stretch of river,
blueback salmon were tagged with var-
ious colored tags, were released in
the forebay at Rock Island Dsuna, and
were observed at Zosel Dam approxi-
mately 145 miles upstream on the
Okanogan River. The use of combina-
tions of colored tags enabled us to
identify tagging dates as tagged fish
passed an observation point. Zosel Dam,
the observation point, is a small wooden
structure designed to forni a pool for
logging operations at a nearby mill.
Observers recorded the daily passage
of tagged and untagged fish through the
fishways at this dam; however, fish
were also able to pass the dam through
cracks in the wooden weirs. As few
recoveries were made from the 1957
experiments, the data from tagging
experiments of 1954 and 1955 were used
to obtain rates of travel between Rock
Island and Zosel Dams. These experi-
ments in 1954 and 1955 were similar
to the 1957 experiments and were for
the purpose of studying the efficiency
of the Rock Island Dcim fishways.

In addition to tagging experiments,
peak counts at Rock Island and Zosel
Dams were used to determine the rate
of travel by computing the difference
in time between the peaks in abundance
at the two places.

The data obtained from the blue-
back tagging experiments at Rock
Island Dam in 1954-55 are presented
below. "Days out" represents the time
interval between tagging at Rock Island
and recovery at Zosel Dam. The day
of tagging is treated as zero day. The
data from the two seasons were com-
bined because the means and variances

of the days -out period of the two re-
covery groups were not statistically
different.

Number of tag recoveries

30

Average number of days out 10.7

Range of days out 7 to 16

Since the distance between Rock Island
Dam and Zosel Dam is about 145 males,
the average rate of travel is 13.5 miles
per day.

The results of a comparison of the
time of peak counts of blueback salmon
at Rock Island and Zosel Dams were
found to agree with results of the tagging
studies. In 1953 the mode at Rock
Island Dam occurred during the period
Jxily 15-22, with a maximum count on
July 18. At Zosel Dam the mode oc-
curred during the period July 23-30,
with the maximum noted on July 28.
Thus, the difference in time between
maximum counts (10 days) compares
closely with the 10.7 days travel time
established by tagging studies. Other
seasons could not be compared as no
definite peaks in abundance were noted
at Zosel Dam.

DISTRIBUTION OF SPAWNERS IN

TRIBUTARIES ABOVE ROCKY

REACH DAM SITE

Salmon are known to be attracted
to certain spawning areas in a river
system, if the flow, temperature,
gravel, and other requirements are
fulfilled. Normally, there is very little
straying from these spawning areas
from year to year. The purpose of the
investigation was to discover the spawn-
ing areas now used by salmon in the
tributaries above Rocky Reach Dam
site.

Stream surveys were made to
determine the distribution and com-
parative abvmdance of spawners in the
tributary streeims. While the survey
counts do not represent the total num-
bers of spawners present, the counts
are of value in deternaining the dis-
tribution and coinparative abundance of

spawners from year to year and indif-
ferent streams, providing the surveys
are made in the Seime manner. Aerial
surveys, of the number of salmon
nests were used as an add in locating
the area of spawning in the Okanogan
River from Oroville to Brewster.

Tagging experiments atRock Island
Dam gave additional information about
spawning areas of the different seg-
ments of the runs which pass Rocky
Reach Dam site. Although these ex-
periments were designed for evaluating
the fishways, they also yield data which
are applicable to this study. Chinook
and blueback salmon were tagged
throughout most of their period of mi-
gration at Rock Island Dam during the
1954, 1955, and 1966 experiments.
Many tagged salmon were recovered
on the spawning grounds, and from
their distribution we learned which
spawning areas were used by various
segments of the run.

Chinook salmon

Peak counts of salmon and the time
period encompassing the peak of spawn-
ing are listed in table 2. These counts
serve to exemplify the relative im-
portance of each tributary stream-
Note the increased covmts in each
stream in 1957 over those of 1956.
Total counts of chinook salmon are
about 3 times the counts obtained in
1956.

The distribution of fish within the
streams is illustrated in figures 5, 6,
and 7. The stream lengths have been
drawn to sccile; the widths, however,
have been exaggerated in order to show
areas of spawning. The symbols rep-
resent the comparative abundance of
individual species within each stream.
As observed, spring chinooks spawn
in the smaller tributaries and more
remote areas of the tributaries, and
summer chinooks in the larger main
tributaries.

The distribution of spawning Chi-
nook salmon according to the time of
season they passed Rock Island Dam is
graphically illustrated by the recovery
of tagged fish on the spawning grounds.
The history of chinook salmon escape-

Table 2. — Spawning ground surveys above Bocky Reach Dam site 1956-57.
Peak counts (live and dead) of chinook and blueback salmon

Species and
name of stream

Salmon counts

1956

1957

Period of peak
of spawning

CHINOOK SALMON

Entiat River

Twisp River

Chewack River

Nfethow River

Above Winthrop

Winthrop to Twisp

Twisp to Pateros

Simllkameen River

Okanogan River

Oroville to Brewster ■""

BLUEBACK SAIM)N

Okanogan River

Above Lake Osoyoos

149
191
404

249
141
375
101

99

16,067

273

702

1,065

909

148

1,398

189

Aug. 20-30
Aug. 10-20
Aug. 15-25

Aug.
Sept
Oct.
Oct.

20-30

. 5-15

5-15

10-20

8,533

Oct. 15-25

Oct. 1-10

During aerial surveys of this section following the peak of spawning, 37 salmon
redds were counted in 1956 and 53 redds in 1957.
^Survey too early for spawning peak.

3 mites
(widths eiagQeroled )
o Spnnq Chinook
• Summer Chinook

Figure 5. — Areas of spavming in the Entiat River,

ment at Rock Island Dam shows the
separation of spring and summer Chi-
nook runs to occur sometime between
June 25 and July 9. Accordingly, tag
recoveries were plotted by these
periods in which spring and summer
Chinook are known to have passed the
dajxi, figure 8. The period between June
25 and July 9 was chosen as a period
of overlap of the two runs. It is ob-
served that for the combined tagging
data of 1954 and 1955 no tagged spring
Chinook were recovered on the summer
Chinook spawning areas; only one tagged
sumimer chinook was noted in spring
Chinook spawning areas. Fish tagged
during the period of overlapwere found
in both areas.

The 1956 tagging experiments at
Rock Island Dcm:i indicate that spring
chinook may not always pass Rock
Island Dami and Rocky Reach Dcm^i site
in the periods indicated. The distribu-
tion of tagged fish by season of passage
at Rock Island for 1956 is showninfig-
ure 9. Many fish tagged after Jvily 9, 1956

Rottli

3niiles

(widths exaggerated )

o Spftng Chinook
• Summer Chinook
X Blueback Salmon

Figure 6.— Areas of spawning in the Metiiow River system.
10

\Loke Voseoui

P

I Oliver Oiverson

Tuc ul nuit Lohe

BRITISH COLUM Bl A
WASHINGTON

3 miles
( l»l(ll^s eioggeroted )

Summer Chinook redds
Bluebock Salmon

J^

^ r

\\ ( Inkoneep Cfeeh

Figure 7.- -Areas of spawning in the Okanogan and Similkameea Rivers.

11

Figure 8.--I}istrlbutioa of tagged chioook salmon above Rocky Readi Dam site by period of tagging at Rock Island Dam,

1954 and 1955.

12

Legend

D Tagged prior to June 25
O Togged June 25- July 9
A Tagged ofter July 9

BRITISH COLUMBIA
WASHINGTON

Leovenworfh
Hotchery

Figure 9.— DistributioD of tagged chinook salmon above Rocky Readi Dam site by iieriod of tagging at Rock Island Dam

during 1956.

13

appeared in spring chinook spawning
areas. These were spring chinook and
not summer chinook as evidenced
by their characteristic small size,
greenish-gray appearance, and early
spawning. Summer chinook average
larger, take on a reddish color in spawn-
ing streams, and spawn later in the
season. Apparently a delay along the
migration route was responsible for
the unusually late passage of mainy
spring chinook at Rock Island Daan,
Davidson' noted that the upstream
salmon migrationin the ColxunbiaRiver
is retarded by floods, and at stages of
extreme high water may be inhibited.
In 1956 a minor flood occurred in the
Coliunbia River and the unusually late
passage of many spring chinook could
be attributed to this occurrence. It
should be noted that none of the fish
tsigged prior to July 9 was recovered in
summer chinook spawning areas that
season.

Another tagging experiment con-
ducted during 1956 confirmed our be-
lief that fall chinook spawn in the main
Columbia River. Sixty- two chinook
from the September migration at Rock
Island Dam were tagged and released
over a 3-day period. No tagged fish
were recovered fronn this lot during
the streaun surveys made on all tribu-
tary streauns. For similar experiments
in August, however, in which the num-
ber tagged ranged from 24 to 70 chinook,
some tags were recovered. Total re-
coveries from these summer experi-
ments averaged 10 percent. If the fall
escapement of chinook salmon spawned
in the tributaries, surely some tags
would have been recovered; six fish
would have been recovered if the 10
percent average were obtained. It
seems certain that these fish sp>awn
only in the main Columbia River, but
because of the difficulty of finding
tagged fish in so large a river, no re-
covery was attempted there.

Blueback salmon

Majority of the blueback scdmon
passing Rocky Reach Dam site are

' Davidson, F. A. 1957. The effect of floods on the up-
stream migratioii of the salmon in the Columbia River.
Riblic Utility District No. 2 of Grant County (Ephrata,
Washington). 20 pp. Processed.

bound for the spawning areas in the
Okanogan River in Canada as evi-
denced by the strezim surveys (see
fig. 7). Very few blueback salmon
enter the Entiat, Methow, and Similka-
meen Rivers. Blueback seilmon tagged
during all parts of the migration period
at Rock Island Dam were recovered on
the Okanogan River spawning grounds.
Spawning commences in the Okanogan
River during the lastweek in September
and continues throughout the month of
October.

SUMMARY AND CONCLUSIONS

Investigations of fish runs passing
Rocky Reach Dam site have revealed
that important runs of chinook and blue-
back salmon pass the site bound for
S|>awiiing areas in all mciin tributaries
between Rocky Reach and Chief Joseph
Dam. The runs passing Rock Island
Dam would be expected at Rocky Reach
Dam site within Ij or Z days since the
dams are only Zl miles apart.

For 1957 the spring and stimmer
chinook escapement pass Rocky Reach
Dam site was approximately 11,000
and 6,000 fish respectively. The es-
capement of blueback salmon passing
Rocky Reach Dam site was approxi-
mately 67,000 fish in 1956 and 43,000
fish in 1957.

Steelhead trout and silver salmon
are assumed to pass Rocky Reach;
however, their numbers were not deter-
mined. Although numerous in the area
up to the year 1920, very few silver
salmon have been counted at Rock
Island Dam since counting commenced
in 1933.

The rate of travel of blueback
salmon between Rock Island Dam and
Zosel Dam established from tagging
experiments was found to be 10.7 days
for the 145 miles distance or 13.5
miles per day. The difference in time
between peaks of abundance at Rock
Island and Zosel Dam also indicated
that about 10 days were required
for fish to travel between the two
points.

14

In general, spring chinook spawn
in the smaller, more remote tribu-
taries, and summer chinook spawn in
the lower main tributaries. Fall chinook
spawn in the main Columbia River.
Blueback salmon spawn in that part of
the Okanogan located in Canada, from
Liake Vaseaux to Lake Osoyoos.
Scatterings of blueback were also found
in the £ntiat, Methow, andSimilkameen
Rivers.

LITERATURE CITED

FISH, FREDERIC F., AND MITCHELL
G. HANAVAN.
1948. A report upon the Grand Cou-
lee fish-maintenance project

1939-1947. U. S. Fish and Wild-
life Service, Special Scientific
Report No. 55, November,
63 pp., Washington, D. C.

TALBOT, G. B.

1950. A biological study of the ef-
fectiveness of the Hell's Gate
fishways. International. Pacific
Salmon Fisheries Commission,
Bulletin III, Part 1, pp. 3-80.
New Westminster, B. C, Can-
ada.

WASHINGTON STATE DEPARTMENT
OF FISHERIES.
1899- 19Z0. Annual Report of State
Fish Conunissioner. Olympia,
Washington. Various paging.

15

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