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/ 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 . . 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