Special scientific report

SPAWNING ESCAPEMENT

OF OKANOGAN RIVER BLUEBACK

SALMON (O.nerka), 1957

Marine Biological Laboratory

' 19:;9

WOODS HOLE, MASS.

SPECIAL SCIENTIFIC REPORT- FISHERIES No. 275

UNITED STATES DEPARTMENT OF THE INTERIOR
FISH AND WILDLIFE SERVICE

EXPLANATORY NOTE

The series embodies results of investigations, usually of restricted
scope, intended to aid or direct management or utilization practices and as
guides for administrative or legislative action. It is issued in limited quantities
for official use of Federal, State or cooperating agencies and in processed form
for economy and to avoid delay in publication .

United States Depeurtanent of the Interior, Fred A. Seaton, Secretary
Fleh and Wildlife Service, Amie J. Suomela, Commissioner

SPAWNING ESCAPEMENT OF OKANOGAN RIVER
BLUEBACK SAIMON (ONCORHYNCHUS NERKA) , 1957

by

Donovan R. Crsuidock
Fishery Research Biologist

Special Scientific Report--Fisheries No. 275

Washington, D. C
December 1958

The Library of Congress catalogue card for this publication
is as follows:

Craddock, Donovan R

Spawiiiiifr es-capemcnt of Okanogan River blueback salmon
(Oncorhynchus nerka) 1957. Washington, U. S. Dept. of
tlio Interior, Fish and Wildlife Service, 1958.

8 p. (iiagrs., tables. 27 cui. ( Special sclentiac report— fisheries,
no. 275)

Bibliography: p. 7.

1. Salmon. i. Title. (Series: U. S. Fish and Wildlife Serv-
ice. Special scientific report : fisheries, no. 275)

[SH11.A335 no. 275] Int 59-19

U. S. Dept. of the Interior. Library

for Library of Congress

The Fish and Wildlife Service series, Special Scientific
Report — Fisheries, is catalogued as follows:

U. S. Fish and Wildlife Service.

Special scientific report : fisheries, no. 1-
(Washington, 1949-

no. iUus., maps, diagrs. 27 era.

Supersedes In part the Service's Special scientific report.

1. Fisheries — Research.
SH11.A335 639.2072 59-60217

Library of Congress

ABSTRACT

The blueback salmou spawning area of the Okanogan River
has been surveyed extensively each yeeir since the start of a
Canadian flood-control project in 1951. The spawning populations
have been estimated and their distribution above Rock Island Dam
detezmined. The large niiober of fish unaccoxmted for may be
partially attributed to mortalities caused by the high water
temperatures existing in the Okanogem River prior to spawning.

The age, length, eind sex compositions of the 1957 Okanogan
River spawning escapement were determined from samples collected on
the spawning grounds. Althoiigh seme delay in passage occurred at
the thirteen newly completed drop structures, completeness of spawn-
ing was not abnonoally low.

The occurrence of large numbers of 33 's ^ *^ spawning
population seems to be peculiar to the Okanogan River.

The distribution of fish on the spawning grounds has not
changed appreciably since 1952.

TABLE OF CONTENTS

Page

Suirveys 1

Spawning escapement 1

Water temperatiire 1

Composition of escapement k

Spawning success k

OccvoTrence of 32'" 7

Distribution 7

Experimental channel 7

Svmnary and discussion 7

Literature cited 7

SPAWNING ESCAPEMENT OF OKANOGAN RIVER
BLUEBACK SAI/<ON (ONCORHYNCHUS NERKA) , 1957

The encroachment of civilization has
greatly restricted the spawning migrations
of the Columbia River blueback salmon.
The Osoyoos, Wenatchee, and Redfish Lake
systems are the only spawning and rearing
areas of importance remaining available to
this valuable species of Columbia River
S6uLmon>

The spawning area of the Okanogan,
which is the most important of the three
systems, has been channelized recently in
connection with a Canadian flood-control
project. This channelization necessitated
construction of 13 drop structures (small
dams with 3 feet of head) which the salmon
must ascend on their migration from Lake
Osoyoos to the spawning area. Annueil sur-
veys have been made to detenaine the im-
mediate effect of the flood-control work
on the salmon and to see that all steps
necessary for their protection are taken.
The long-range effect of this project on
the Okanogan blueback runs will not be
known for several years.

SURVEYS

Blueback spawning activities in the
Okanogan have been surveyed extensively
each year since the flood-control project
started in 1951. Five surveys were made
this season in much the same manner as in
previous years. The 1957 surveys were of
particular interest because for the first
time the fish have had to ascend the new
channel with its 13 drop structures. Since
a partial block existed at drop structure
No. 2 during the last half of September,
special attention was given to the spawn-
ing success of the migrants. This delay
plus the possibility of other delays could
cause the fish to arrive at the spawning
area too late and too weeik for successful
spawning.

The section designations used in
pluvious years were followed closely. These
sections and the location of the drop
structures ajre depicted in figure 1 (page
2). Conditions for observing the spawners
were very good except on October 22, when
wind and snow made observations difficult.

The area from the Southern Okanogan Lands
Project Dam to drop structure No. 13 was
surveyed by rubber boat, and the area from
drop structure No. 13 to Lake Osoyoos was
checked from the dike paralleling the river.
A few spawning fish were observed near drop
structures No. 6 and No. 13, but the spawn-
ing below No. 13 was of little importance.

SPAWNING ESCAPEMENT

Table 1 presents the actual counts
made on the various surveys and table 2
shows the spawning population estimate
derived by the "Factor 5" method. This
method (Gangmark and Fulton 1952) has been
used on the Okanogan for several yeeirs.
Although we are convinced that it gives a
consistently low estimate, we feel that it
serves as a reliable index of the magnitude
of the spawning population.

The 1957 count of blueback through
the fishways at Rock Island dam was 71,261.
Of these, 28,231 were counted at Tumwater
Dam on the Wenatchee River, 8ll were taken
by "up river" hatcheries and miscellaneous
samples, and an estimated 3>017 were taken
by the Okanogan Indian fishery. The
"Factor 5" estimate of 25,350 for the
Okanogan spawning population leaves 13,919
fish or 19.5 percent of the Rock Island
blueback count unaccounted for. Table 3
is a record of the distribution of blue-
back above Rock Island obtained by using
"Factor 5" estimates for the Okanogan.
The increasing number of fish accounted
for in recent years is probably due to
improved siirvey techniques euid accurate
counts obtained at Tumwater Dam.

WATER TEMPERAIURE

Although it has not been proved,
many of the fish unaccounted for may have
succumbed to the effects of the high
temperatures encountered in the Okanogan
during the migration period (fig. 2). For
more than 2-1/2 months during July, August,
and September, the river temperature was
well above the 65 "F. level. These high
temperatures are common since the four

S. O.L.R Dom
A

\Voseou)( Lake
SO.L.P Dom

CANADA
U.S.A.

OROVILLE L-/zoselDam
Area Mop \^

- Section designotions
= Verticol drop structure

Figure I. DIAGRAM;
CHANNELlZATIOr
SPAWNING GROUNDS OF THE OKANOGAN'R.

Tabl« 1.— Spawning ground surveys, Okanogan River, 1957

Section

Sept.
25

Oct.

1

Oct.
8

Oct.
15

Oct.
22

Total
live

Total
dead

Live

Dead

Uve

Dead

Live

Dead

Live

Dead

Live

Dead

838

A

129

155

285

221

1

48

1

B

272

491

1773

2

1212

50

463

112

4?n

164

C

173

923

1879

3

131*3

1*7

320

198

4638

248

D

115

530

570

1286

1*4

31*3

283

2844

327

E-H

252

759

k

2803

12

1551

384

436

858

5863

1258

H-K

hk

299

1179

17

1076

l^h

248

397

2784

568

K-13

50

10

30

90

Total

985

3207

k

8499

3^*

6719

680

1858

1848

21,268

2,566

Table 2. — "Factor 5" estimates of Okanogan spawning population, 1957

Section

E-H

H-K

K-M

Survey
date y

10/1
10/8
10/15
10/22

10/1
10/8
10/15
10/22

10/1
10/8
10/15
10/22

10/1
10/8
10/15
10/22

10/1
10/8
10/15
10/22

10/1
10/8
10/15
10/22

10/1
10/8

10/15
10/22

Count

155

285

221

48

491
1773

1212

463

923
1879
1343

320

530
570

1286
31*3

759
2803
1551

436

299
1179
1076

248

50

10

30

0

Average

Am.

177

985

1116

682

1387

701

22

885

4925

5580

3410

6935

3505

110

Estiaate :

25,350

1/ The Survey of 9/25 wa* ellninated since spawning was not actually
in progress.

large leikes In the Okanogem chain pemit
great surface heating.

Figure 2 also Illustrates the varia-
tion In temperature, 62' to Wf., during
the period of spawning- The peak of spawn-
ing occurred at a temperature of approxi-
mately 53'F.

ratios in the two age classes as well as
the age -class composition of the entire
sample. The 32 's made up 30 percent of
the sample and had a sex ratio of 1 male
to 0.514- females while the k^'s made up
70 percent of the sample and had a sex
ratio of 1 male to I.62 females.

CC»1P0SITI0N OF ESCAPEMENT

A sample of 695 fish was measured on
the Okanogan spawning grounds. The length
frequency curve, figure 3> clearly indicates
the occurrence of the two age classes com-
prising the spawning population. Exami-
nation of the otoliths from 79 of these
fish disclosed that the dividing line
between the 32 's and 42's lies between
18 inches and iS-l/l*- inches for females
and between I8-I/2 inches and 18-3/^ Inches
for males (table h). This table also
demonstrates the divergence of the sex

SPAWNING SUCCESS

Table 5 is a record of a much larger
sample examined for sex and for spawning
success. A total of 2,046 fish were sexed,
and the females were examined for complete-
ness of spawning. The overall sex ratio
of medes to females in this sample was 1:
1.3^, and 92 percent of the females were
canpletely spawned. In 1955 and 1956 the
percentages of completely spawned fish
were 9'* and 95 respectively, which indi-
cates that the delays encountered by the
1957 spawners did not materially affect
their spawning success.

Table 3* -'Distribution of blueback salmon above Rock Island dam

Year

Okanogan

factor

5

Wenatchee
counts 1/

Entiat &

Methow

Hatchery

Indian
catch

Total
accounted
for

R.I.
count

^ of R. I.

count
accounted for

I9U7

18,125

38,230

135

5,000

61,1+90

79,831+

77.02

19kQ

35,885

38,205

90

5,000

79,180

81+,627

93.56

19^*9

310

3,880

-

500

l+,690

18,682

25.10

1950

-

-

-

2,500

-

50,059

-

1951

12,21+0

17, '^95

200

5,000

3'*,935

102,721+

31+. 01

1952

25,000

19,200

1,000

3,000

1+8,200

113,703

1+2.39

1953

3lt,260

15,000

3,203

^+,533

56,996

152,013

37 A9

1951*

13,206

25,000

100

3,9^^

1+2,252

91,181+

1^.33

1955

'♦7,930

50,000

1,105

4,626

103,661

155,782

66.51+

1956

39,256

25,518

203

3,598

68,575

92,209

71+. 37

1957

25,350

28,231

811

3,017

57,1*09

71,261

80.56

1/ Factor 5 estimates through '52 and counts at Tumwater Dam thereafter.

-

FIGURE 2

AVERAGE DAILY TEMPERATURE
OKANOGAN RIVER— 1957

80

_

75

"

>\'

,1

ZOSEL DAM

f^^

'

1 , / .,'.

70

X

leo

X

<

If

"•MA' / /

""^

CO

UJ50
liJ

q:

-

^^

IU45

^ \/ ^ ^^

SPAWNING VVr^

40

-

^K^

35

1

1 1 1

1 1 1 1 1 1

1 I 1 1 1 1 1 1 1 1 1 1 I 1 1 1 1 1 1 II

5 10 IS 20 25 0 5 10 15 20 c'O 0 5 10 15 2C' 25 0 5 10 15 20 25

JULY AUGUST SEPTEMBER OCTOBER

5 10 15 20 25 0 5

NOVEMBER

75

CO

u.

li.
o

LlI

m

25

FIGURE 3 LENGTH FREQUENCY OF BLUEBACK
SALMON, OKANOGAN RIVER, 1957

635 COMPOSITE

324 MALE

37 I FEMALE

1475 1550 1625 170 1775 1850 1925 200 2075 2150 22 25 230

FORK LENGTH-MIDPOINT OF 1/2" INTERVALS

Table k. — Age-group breakdown as deteimined from otolith study,

Okanogaui blueback, 1957'

Age
group

Males
No . Length

Females
No. Length Total

Sex ratio
M : F

Percent
females

i

of total
sample

32
U2

139 <18-3A"
185 18-3/4" >

70 < 18-1/4" 209
301 18-1/4 "2. 486

1.00:0.54
1.00:1.62

35
62

30

70

Total

324

371 695

1.00:1.14

53

100

Table 5.— Sex ratio euid spawning success of Okanogan blueback,

1957.

Survey-

Total
dead

Dead
exam.

Sex

Sex ratio
M : F

F

Spawning
of fem
SPO USP

success
ales 1/

date

M F

PSP ^SPO

Sept. 25

0

Oct. 1

4

2

1 1

1.00:1.00

50

1

Oct. 8

34

26

11 15

1.00:1.36

58

10

4

1 67

Oct. 15

680

360

198 162

1.00:0.82

45

140

8

14 86

Oct. 22

1848

1658

663 995

1.00:1.50

60

929

29

37 93

Total

2566

2046

873 1173

1.00:1.34

57

1079

41

53 92

1/ SPO - spawned out - over 751^ Spent.
USP - unspawned - less than 25'3i Spent.
PSP - partially spawned - 25 to 75?i Spent.

OCCURRENCE OF Sg'^

SUMMARY AND DISCUSSION

The 1957 return of blueback was of
special interest since the U^g'^ ^^^^ ^®
progeny of the 1953 escapement which was
one of the largest in recent years. The
most unusual feature of the 1953 r^"i was
that over 86 percent of the Okanogan
spawners were 3-y6*r-old fish whose sex
ratio of males to females was 1:0. 75- 1^
hulk of these 3-year-old fish escape the
fishery and continue to the Okanogan where
in normal years they comprise about 22
percent of the spawning population. These
pm^n fish seem to be peculiar to the
Okanogan £uid su« seldom encountered in the
other two systems. Table 6 demonstrates
the occurrence of 3-year-old Columbia
River blueback for the last 7 years.

The ccHDparatively low return to the
Okanogan this year may be peo-tly attri-
buted to the high proportion of 3-year-old
fish in the 1953 run. Lower fecundity and
possibly lower fertility linked with re-
duced survivfiLL of eggs, fry, and finger-
lings because of their small size may be
factors contributing to the low return.

DISTRIHJTION

The 1957 Rock Island count of blue-
back salmon was the smallest recorded since
1950. This decline was more evident in
the Okanogan than in the Wenatcfaee system.
It has been speculated that lower fecundity
and poor survival of the spawn of the 32'"*
that made up 86 percent of the Okanogan
run in 1953 was a factor in this year's
low return.

The 1957 spawning escapement to the
Okanogan was composed of 30 percent 32 's
and 70 percent 42's. The sex ratios of
the two age cleisses were widely divergent.
The 32 's had 35 percent females and the
U2's had 62 percent females.

Spawning success was good and ap-
parently was not affected by the delays
caused by the drop structures. However,
the drop at many of the structures was
considerably greater than anticipated,
and some modification may be necessary to
increase the ease of fish peissage at these
structures.

In gener€il the escapement was ade-
quate and spawning appeared to be success-
ful.

The distribution on the spawning
grounds has not changed appreciably in the
last 5 years. The one exception is section
M-N, which for all practical purposes sup-
ported no spawning this year (fig. h).
During the past 5 years section M-N sup-
ported an average of only 7 percent of the
spawners.

LITERATURE CITED

GANGMARK, HAROLD A. , AND LEONARD A. FULTON
1952. Status of Columbia River blue-

back runs, 1951. U. S. Fish and
Wildlife Service, Special Scien-
tific Report— Fisheries No. Jk,
29 pp.

EXPERIMENTAL CHANNEL

Channel improvement work in sections
B to D was responsible for reducing the
flow in the experimental channel to a mere
fraction of normal. Consequently, only 88
fish were observed spawning in this channel
compared to 2,600 for last year. This same
channel work seriously reduced the flow in
the west channel causing an additional loss
of spawning area.

Table 6. — Occurrence of 3-year-old Coliunbia River blueback salmon

Rock Isl. dam counts

Year

Total
run

Large
fish

Small
fish

Rock Isl. small fish
^-Qf fof

Total

totfkL Rock Is.
run count

Vfenatchee ^ of SgO
River Okanogan
system River 1/ Okanogan

1951 201*, 369 89,733

1952 320,362 104,206

1953 260,079 99,565
195** 178,581 76, 7 W

1955 244,879 145,461

1956 202,240 74,563

1957 156,000-^ 63,733

12,093 101,826 5.9

9,480 113,686 3.0

52,182 151,747 20.1

14,486 91,234 8.1

7,601 155,062 3.9

17,880 92,443 8.8

7,528 71,261 4.8

11.9

17,495

12,230

-

8.3

19,200

u

25,000

-

34.1

15,000

y

72,000

86.6

15.9

25,000

49,000

20.9

6.2

51,820

48,000

12.7

19.3

25,518

40,000

24.9

10.6

28,231

25,000

30.0

1/ Estimates.

100

O 80
o

O

60

O 40
UJ

a.

20 —

0*"

FIGURE 4 DISTRIBUTION OF BLUEBACK SALMON ON THE
OKANOGAN RIVER SPAWNING GROUNDS, 1952-1957

^AAA

\

1952

T^T^

^i

\\\v

k\\\

^•>

1953

1954

1955

1956

1957

SECTION
^A-E

mni M-N

INT . -DUP . SEC . . WASH . . DC. -j e i* 3 •

MBL WHOl '-*;fl>|,|:,,i?n||MI|ill||l

5 WHSE 01273