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

'