STATUS OF COLUMBIA RIVER BLUEBACK SALMON RUNS, 1951 Marine Biological Laboratory J'JN13 1952 WOODS HOLE, MASS. SPECIAL SCIENTIFIC REPORT: FISHERIES No. 74 UNITED STATES DEPARTMENT OF THE INTERIOR FISH AND WILDLIFE SERVICE STATUS OF COLUMBIA RIVER BLUEBACK SALMON RUNS, 1951 Marine Biological Laboratory J'JNU 1952 WOODS HOLE, MASS. SPECIAL SCIENTIFIC REPORT: FISHERIES No. 74 UNITED STATES DEPARTMENT OF THE INTERIOR FISH AND WILDLIFE SERVICE Explanatory Note The series embodies results of investigations, usually of restricted sccpej intended to aid or direct management or utilization practices and as guides for administrative or legislative actioHo It is issued in limited quantities for the official use of Federal^, State or cooperating agencies and in processed form for economy and to avoid delay in publication. Washington_j D. April, 1952 CONTENTS Page A brief history of the Columbia River bluebackso ^ ...,,. „.o . 1 Present status of blueback runs. ,o.....o....o.o..., 3 Spawning surveys o- ,..■, ...o .o ,„......,.,,.,.. „ 7 Lake Wenatchee surveys ..........<........... -o . 7 Okanogan surveys ,,..<.<,...<...<...... ...» ...... l6 Survival in the rearing lake ..................... 23 Future runs and recoimnendations, ..... ......... 23 Summary and conclusions ......... ............... 28 Literature cited ............... ...... 29 ILLUSTRATIONS Figure Page 1. Known blueback salmon rearing areas of the Columbia River River System — past and present ....•.....,.,.,,. 2 2. Commercial catches of blueback salmon, Columbia River, 1889-1950. ........................... h 3. Present known migration routes of blueback salmon, Columbia River System . 5 It. Columbia River blueback salmon counts over Bonneville and Rock Island Dams and total run data 1938-51 8 5. Columbia River blueback salmon counts over Bonneville and Rock Island Dams and total r\m data 1938-^1 plotted by ii-year cycles. 9 6. Diagrammatic map of the principle blueback salmon spawning areas of the Lake liTenatchee System . 10 7. Occurrence curves from blueback spawning counts in the Okanogan River, 19ii7 . . lii 8. Diagrammatic map of the principle blueback salmon spawning areas of the Okanogan River System. .......... I8 9. Map of upper Okanogan region showing possible spawning area for blueback salmon ...........,...,,.,. 25 United States Department of the Interior, Oscar L. Chapmanj, Secretary Fish and Wildlife Servicej Albert M, Day, Director STATUS OF COLUICIA RIVER BLUEBACK SALJON RUNS, 1951 by Harold A« Gangmark and Leonard A. Fulton Fishery Biologists Special Scientific Report: Fisheries No, Ih The comraercial take of blueback salmon in I9J47 exceeded all -atcn- since 1925 and the escapement (coxmt of fish over Bonneville Daai minus the catch above Bonneville) was the largest since counting was started at Bonneville in 1938, This large escapement caused West Coa^t fishery- agencies to become concerned about the capacity of the limited remaining stream areas to accoiriinodat.e the larger number of spaxmerso A surrey was therefore maae to determine the density of populations and the probabie success of natural spawning of blueback salmon utilizing the remaining rearing grounds in the Wenatchee and Okanogan River systew:;. The earlier parts of this work were done at the direcoiOii . ' Joseph To Barnaby, formerly Chief ^ North Pacific Fishery Investigations,, Ral}.h P. Silliman was in charge of the first field surveys <> Grateful ackncwl<^'-'r-'e' ment is due Floyd G„ Bryant, A. A. Gentry, Zeil E» Parkhurst and K. G, Weber for their active participation and helpful suggestions in the prepa- ration of this report. A BRIEF HISTORY OF COLUMBIA RIVER BLUEBACKS The blueback salmon (0. nerka) , unlike ether salmon, generally deposits its eggs in streams tributary to lakes or on the shores of lakes theicselvo^o On emerging from the gravel, the 2'oung usually spend one or more years in the lake before making the seaward migration. Most lakes suitable for propagation of bluebacks have been lost through the development of power and irrigation projects o High dams without fish facilities, and irrigavioi; canals without proper screening for downstream migrants, have combined to deplete the rearing areas (Rich 19U2j po 106), The known blueback spawning areas (figure 1) of the Colum.bia Pivei" system., have never been as numerous as those for the Chinook salmon » They include the Payette and Redfish Lakes in Idaho, Wallowa Lake in Oregon,, the lakes of the Yakima River system in Washington, and the Arrow and Upper Okanogan Lakes in Canada,, all of which have been isolated by darasol/ The last of these systems to be eliminatedj the Arrow Lakes ^ was isolated by Grand Coulee Dam« To compensate for the loss of spawning area the Uo S, Bureau of Reclamation built three hatcheries and financed reloca- tion of bluebacks and other species of fish« All bluebacks were placed in t\-io remaining spawning and rearing areas , (1) the Lake Wenatchee regior,. in central Washington, and (2) Lake Osoyoos which lies in Canada and north central Washingt-cr, (Jlsh and Hanavan 19i48„ po5)o ^/ The Redfish Lakes are new accessiblej but the runs had already bean depleted by Sonbeam Dam and have never been restocked. Surveys in the area during the 19U6 and 1.9li7 seasons revealed only six bluebacks „ LAKE KENATCHE "'f^. %: WASh^ CT ^. columJ 'Uke f'^^TETTE •-♦KES REDFiSH •Uakes Figure 1. Known blueback salmon rearing areas of the Columbia River System — past and present Paralleling the decrease of available spawning and rearing areas for the bluebacks has been the decline of the commercial catches of blueback salmon. This is illusorated in figure 2 and shows early catches of 1 mil- lion povjids to be common, mth occasiona"". takes exceeding h million poiinds (Craig and Hacker ipliO , po I98) „ 'AH.de fluctuations occurred in the com- mercial fishery but a distinct downward trend persisted until a low of only 8_„500 pounds was taken in 19hS'> PRESENT STATUS OF BLUEBACK RUNS Since the Grand Coulee Fish Salvage Project of 1939~ll3, the blueback runs have shown evidence of recoveryo This may be a result of special effort in connection with the salvage program (Fish and Hanavan 19^8, p«^), or may be merely a natural fluctuation such as those which occurred before the Grand Coulee Dam was built „ In their spawning migration blueback salmon must pass over Bonneville and Rock Island Dams (figure 3) where counting stations are maintained. The counts of salmon over the two. dams on the migration route to the spawning grounds help considerably in an. analysis of the runs,. Information obtained from the States of Oregon and Washington on daily deliveries of blueback salmon to canneries enables us to complete the picture of the trends of abundance of the species o An example of the runs analysis derived from the available information is seen in table 1. Inspection of the Rock Island Dam precentage of escape- ment (item 13) reveals considerable fluctuation from year to year. This is probably due to three factors? (1) low water conditions and resulting higher temperatures causing mortality2/j (2) natural mortality of fish infected with disease or otherwise in a weakened condition^ and (3) straying into other streams o The percentage of fish at Rock Island Dam does appear to be in- creasing, however, as shown in table 1, Item 11 in table 1 gives fishing intensity which is calculated by dividing the total commercial deliveries by the total estimated run. It can be seen that there is a wide variation in fishing intensity, which ranges from 13o^ to 89,3 percento The 19^8 and 19U9 rates of fishing in- tensity were low due to & closure of commercial fishing during the major part of the blueback nigra tion^ the purpose of the closure being to obtain a larger spawning escapement so as to increase future runs of fish. 2/ The extremely small percentage of bluebacks reaching Rock Island in 19hl was caused by extreme low water conditions aggravated by a water shortage as a result of the filling of Grand Coulee Reservoiro Low water caused lethal temperatures and provided poor passage over artificial and natural barriers in the river (Fish and Hanavan I9U8, p. ^1) » o I o eo u % CO •H 43 O O c o as m oc < CO UJ ,0 >• 3 iH fi a> o 3 1^ K) CM SONOOd dO SN0I11IN 6 > to > •H « •H o 13 C c E 1-1 (D (0 O CO XI <0 o (0 a o t-, c o ^ c >■ o c a Q) en 0) t^ Hi naui Dm OK OAICH, tsDimmn wto., mr oouwiu am Buirawt tarn - i9j»-x9}i SSL. L22L (X) OkUk iMlOT Bom*. ttak (!»■ lOi^) M.JTti (» tMtnlU* aoant TS.OkO (5) Tktal m, astnr oT tlak (It«i !•«) |l6T,lali (k) Catch sbov* Boaiw- { nu«, panda I 9t,398 i (6) Catch aba** of flih I (Ita'k/S) ! *,Wt m mmtxr of riah tt*mm «-6) 3A.S96 122. ^»l>Q liT.jSl J6,?T» 1?0,746 lliS.SOS 185,T77 196,193 m^ i.ll 2.7 I 33,3T»j 7»,6«l. liO.QlO 76,Ha (8) IMal catch, fowls |li2S,100 266,S00t JSI.SOO aw«ra0t (9) AU-rl* vai^t povoaSa (10) TMal cat£h, Ktmbmr ^ (Itaa 8A) 3.3 ue.siB (u) naeiii« ij>t«Mi«y. prrD«t(10OxItaa W3) 76.9 (12) lech lalaad eoiatt 17,123 (13) B«ti lolMt yarcaot { of caeapadCOidtaa 12/7)U>Ji 10S,71S 6S,7ia 171.1.S6 127,915 >.7 Ii7.3r6 18,365 ^SiiL 37,799 5S,b63 93,J6» 55,362 2.7 20, Soli 3I»,9S9 505,200! W2,Ue» 3.3; 3.3 3.3 80,756 66.9 19.591 Ii9.0 10»,636 59.0 153,091 89.3 3.3 56,303 62.5 19m 33,813 39,BU. 73,657 26,768 2.7 9,91it 29,930 Uili,300 3.3 U3,727 l>ltlt 7,637 15,071 22,708 21,321 2.7 7,897 7,17U S5,9a 3.6 15,53lt 19U5 1916 |l9i.7" 26,»9b 9t>9 16,282 35.3, 5.2 li6.6 59.li 6S.b 17,665 59.0 l>,932 68.7 1,096 9,S01 10,597 3,869 2.7 1.1.33 6.066 8,597 3J> 2.529 23.9 7,11.2 86.5 27,72li 7li,35l. 102,078 3S,19li 2.7 13.035 61,319 126,353 3.1 liO,759 39.9 li5.029 73.l> 167, UO 171,238 338,31.8 11.0,59b 2.7 52,072 119,166 701,383 3.2 219.182 61..B 79,833 67.0 M^ 8,915 131,537 U0,h52 58,327 2.7 21,603 109,93b 95,79b 3.3 29.028 20.7 8b.626 77.0 T i!te__iii2£-4iZ21- 2.2M 5l,bbb 53.666 13,599 2.7 5.037 b6,b07 23,9Sb 3.3 7,259 13.5 18,601 77,993 l09,9bS 52.138 2.7 19.310 58,683 169,163 3.3 51,262 b6.6 Jlp952 35.955 Ii5,b76 I69.b2e *',77b 50.Qb7 bO.O 85.2 205, '83 :.?P,25l 33,200 3/ 6?,?T0 2.7 12,296| >-.ni 157,132 57,563 lS9.22ej 23i,121 3.3 b8,2Sl 101, 782 6b.8 70.581 23.5 SS.O 3S.03S 60.; y ■aaai m •iT»t'« aoidlnc, iacladlag 3,031 C»Ulo flth la 19b7 aad 19.822 appar plTar ftih la 19bbJ.7. ■■•^i «a arraotU sa^illi«, iaelaMac 29.3b3 flrii In 19bb-b7. The dam counts and total runs analysis is illustrated in figure i;, in which :°t can be seen that since the low of IS'U^j the runs have shown sigTis of recovery. Since bluebacks ai-e predominantly i; years old at time of re- turn, the counts in figure !? are plctv-ed by U-year cycles. Of particular interest is the marked increase of bluebacks passing Rock Island Dam. The count there probably represents the best measure of the spawning escapement, because no commercial fishery takes place beyond it, and because there is no eAH-dence that the fish unaccounted for between Bonneville Dam and Rock Island Dam spawn successfullyo SPAMING SURVEYS The 19li7 blueback run was an exceptionally large oneo The commercial catch totaled 7013383 pounds or 219jl82 fish (bashed on average weights taken in Astoria, Oregon, by F, G, Bryant, 19li7^' ) , and the total run was 3385 3U8 fish for the year^, the largest since I926, The original purpose of the surveys reported on herein was to determine how the record 19ii7 run and future runs of perhaps larger magnitude would fare on the remaining spawning grounds » In short, would the spavming gravels be overpopulated to the point where it would have a deleterious effect on the survival of the eggs? The surveys were made during the spawning seasons of 19^7 .t 19ii8j 19^9^ and 19^1., The spawning nopulations were enumerated during the surveys by means of boat and motor, rubber raft, or by footj, depending on the condition of the various streams, l'\fhen too shallow or too swift, the stream was sur- veyed on foot. When conditions permitted, a rubber boat was used^ or when the stream was deep enough the motor and boat were used. There were three pos- sible types of counts f (1) Live fish, (2) redds or spawning nests, and (3) dead fish. Only the first of these was used, since it was impossible to distinguish individual redds where they were in close proximity, and since dead fish tended to settle in deep pools and disappear from sight. Individ- ual fish were counted whenever possible, but on crowded spawning gravels they were occasionally estimated by tens» THE LAKE WENATCHEE SURVEYS The first surveys were begun in the Lake Wenatchee region, where spaivn- ing occurs earlier than in the Okanogan area. Figure 6 is a diagrammatic map of the Vfenatchee system showing where the major portion of spawning takes place. The main spawning areas are in the lower 2 miles of the North Fork of the White River and the main stem of the Wliite River from the North Fork down- stream to within 2 miles of Lake Wenatchee, Blueback spawn in the Little ^ "Average Weights of Columbia River Salmon", T^TtT Floyd G, Bryant, unpublished report. m Q Cd o T3 C « 1— 1 m o M m ^ G> o OD r-l i-l * f-l > «> (D C c o m u (0 > * O 0) to c 3 o tt V ■^ <1 c o e 1 > lueback sal ta 1938-51. M XI 01 <• t- at 0) c > 3 rabia Ri total r i 3 r-l tJ O C o Cd • £ ss 5b •H 0> HSIi M) SQNVSnOHl m z 3 OC g o o m 8 O O o o (0 s; -a c a) i-i to M J«: o o cr: TS c CO CI iH . i-( [0 •H 0) > <-l a> u C t>5 c o o m ^^ CO P, 0) e >> > 1 c o vr < CP >> 111 ^•" >- 3 -O o o ■o Jf CIO m J^ a CJ r'> CO O^ JU i-< a' 3 en i-i -p ^ CO •n h ? § •H ^ K !-< CO ffl ^ -P ,o o +J I-I -o o R o 0! •H Nownvs xoveama do saNvsnoHi (0 < lli % Q. (/> t/> UJ o s -P O -P OS C cd :g o n a> u ca c •H C g a n c i (d 03 J -p o ■p •H ft* 10 Wenatchee River throughout its lower 7 miles except for a short stretch near the lake, A l/2-miie reach at the outlet of Lake Wenatchee, and the lower 2 miles cf Nason Creek are used also. Smaller spawning populations scatter down the Wenatchee River to the town of Plain, Tvro areas on the shore of Lake Wenatchee where -ander^rfater seepage enters the lake are used alsOo Tow of these spawning-stream sections are downstream from the lakeo It was once thought that ail bluebacks proceed through a lake in their migration and spawn in i;he lalie's tributaries | however^, bluebacks are seen spawning below Lake Wenatchee each year. Scale samples takea from these spai^mers re- vealed a freshwater life history no different from those taken from above the lake, suggesting that they were hatched above the lake, or migrated up- stream to it shortly after hatching. On further inquiry, it was found that this anomalous behavior is quite common in Karluk and Bristol Bay, Alaska, and also in sockeye (blueback) streams in Canadao The chances of sun/ival of the resu]i.ting young fish are questionable. If they could swim back up into the lakej their chances of sujrvival would be equal to the chances for survival of fry hatched in streams above the lake. But if they proceed to sea shortly after attaining the free-swimming stage, there is a fair indi- cation, not to be taken as conclusive, that they would experience a mortality far in excess of those which migrated in their second and third years (Gilbert 1912, p. 6l) . The procedure for making the spawning surveys was to enumerate the fish in each section of stream oeriodically until the peak of the run had been observed in each instanceo Some stream conditions influenced the accuracy of the counts. For exan^le, the North Fork of the '.ilhite River and the main stem below become very turbid after a rain storm and poor visibility is the result. Also flooding conditions in the Osoyoos region in 19U6 made counts in the major portion of the stream impossible. The maximum counts made in various streams appear in table 2. In an attempt to account for the total number of fish utilizing each section of stream, certain estimates can be made provided the necessary assiimptions are made alsoo The maxirn'orn counts in each spawning section will give an absolute minimum estimate because we know that many successive groups of fish utilized the spawning gravel in the course of the spawning season. This does not, however, account for the total nuiiiber of fish utilizing the various spavming grounds but merely represents the "standing crop" of spavmers, which during the entire spawning period are being added to by late arrivals and diminished by dying spawned-out salmon. The counts (table 2) for the four survey years, when the hatchery- spawned bluebacks and maxim^jm stream coimts are added, total 12,176 in 19U7, 16,209 in 19h8, 2669 in 19li9, and 7,089 in 1951 for the Wenatchee area, com- pared mth Rock Island counts of 79,833, 81i,626, 18,601, and 101,782. 11 TABLE 2 STREAM CENSUS OF BLUESACK SPAWNERS IBINQ MAXJMUU COUNTS, WENATCHEE RIVER Stream Section Date UaxoCount Total Wiite River little Wenatchee River Nason Creek Wenatchee River little Wenatchee YJhite River Little Wenatchee River Nason Creek Wenatchee River Little Wenatchee White River Little Wenatchee River Nason Creek Wenatchee River Little Wenatchee White River Little Wenatchee River Nason Creek Wenatchee River Little Wenatchee auid White River 19U7 North Fork 2 mi « above confluence Confluence to lake Lake to hatchery rack Cole»s Corner to the Wenatchee Ro outlet of lake to ^ mile below Hatchery take 19U8 North Fork 2 mieabove confluence Confluence to lake Lower seven miles Cole*s corner to the Wenatchee R< Outlet of lake to J mi .below Hatchery take 19U9 North Fork 2 ml, above confluence Confluence to lake Lake to hatchery rack Cole's corner to the Wenatchee R, Outlet of lake to ^ miobelow Hatchery take 19|1 North Fork 2 mieabove confluence Confluence to lake Lake to hatchery rack Cole's Corner to Wenatchee Ro Outlet of lake to \ miobelow Hatchery take 9/2U 9/17-19 9/18 9/22 9/22 9/17 9/21 9/11; 9/17 9/15 9/27 9/21 9/20 9/lli 9/21 9/20 9/18 9/19 9/26 9/20 58 5,529 1,122 U82 1,082 3,liOO 3,871 2,701 U78 1,59U 27 U,5io 2U2 16 230 8,273 3.905 12,176 12,0UU h,l65 16^6? 1,U38 1,231 X5^ 5,025 2,06U ■ 7,of«> 12 In an atterapt t^ account for a greater share of the Rock Island counted bluebackSj an estimate based on averages v/as applied. The esti- mation (using avera{;e counts) of numbers of spawners in the Wenatchee system is based on the i^ssumption that the total numbers of spawners utilizing a given stream section is equal to the average number of live fish in the stream during the spawning period multiplied by the ratio "time period live fish are in the stream" over, "average length of life of the fish after reaching the section." Algebraically^ R = M D / T R equals the total nuinber of spawners ^ M is the average number, D is the duration of period that live fish are present in the sectionj and T is the length of life of an individual fish after reaching the sectionT To evaluate this equation, the symbols M, D, and T must be ^li'ven numerical value. Tlie best estimate of M is the average of successive counts in each section o D is not known i\dth precision^ but can be estimated by the occur- rence curves of the number of fish found in a section upon successive visits o The 19l;7 occurrence curves from counts obtained in the Okanogan River and fitted by inspection, indicated that the length of the period during which fish were present was about 35 days (figure 7) . In the absence of sufficiently complete data for the Lake Wenatchee drainage, this figure was used for that area also. For T, the stream life of the average blueback, no definite information is available for the Columbia River, but a period of 7 days has been estimated on the basis of tagging experiments at Karl-uk Lake, Alaska, and is here used as the best available substitute,. -5 The value of D/T or 35/7 then becomes 5. IVhenonly one count was made, it was used as the average. This procedure produces counts of 3U..710, 36,185, 2,925, and 17,l95, for 19U7, 19U8, 1919, and 1951, which when added to those fish trapped and spa;med by the hatchery, give totals of 38j,6l5 or U8,U percent of the I9I1? Rock Island count, U0^350 or li7,7 percent of the I9I18 count, l4,l56 or 22.3 percent of the 19k9 count, and 19,559 or 19.2 per- cent of the 1951 count. This is probably a better estimate of the spawners which utilized the Wenatchee area (table 3) than that based on maximum counts alone. Thus estimates of numbers of spawners utilizing the Wenatchee region have been made. Their calculation is bhe first step in calculating the ratio of the number of spawners to the number of square yards of suitable spav/ning area available in this system. Further useful information was obtained from stream survey notes compiled by stream surveys of the Service, These surveys give the to tal "n timber of square yards of available spawning gravel in the Wenatchee River system. Finally, information on the square yard requirement for each pair of spawning bluebacks was obtained from earlier work on this subject (Burner, 1951, p, 110) , V U/ 80O square yards given in above publicatonj used 80U which was obtained by" Burner after a more complete analysis of his data. 13 20 30 SEPT. 10 20 OCT. DATE Figure 7. Occurrence curves from blueback spawning, counts in the Okanogan River, 1947. 14 TABI£ 3 DATA FROM SURVgTS OF BLUEBACKS SPAWNDIO VH IMDIYIDUAL STREAM SECTIONS, 19l»7 - 19$! STREAM SECTION DAIX SURVET COUNT AVEKAQE (1)5 19U7 White Rirer North Fork, 2 ailea above confluence 9M 1 58 56 290 White Riyer Confluence to lake 9A7-19 1 5,529 9/21.-25 2 2,868 1,198 20,990 Little Wenatchee Rirer Hatchery racks to lake 10/10 1 1,122 1,122 5,610 Nason Creek Lower 2 nlles 9/22 1 1.82 1.82 2,iao Wenatchee River Outlet of Lake Wenatchee to i aile below 9/22 1 1,082 1,082 5,iao ToUl 31., 710 19li8_ White River North Fork 2 alles above confluence 9/17 1 3,1.00 9/21 2 807 2,101. 10,520 White River Confluence to lake 9A5 1 1,U.5 Uttle Wenatchee River Hatchery racks to lake 9/21 lOA 9/li. 9/214 2 3 1 2 3,871 862 756 2U. 2,059 1.85 10,295 2,1.25,, Little Wenatchee River Above racks 9/22 1 1,91.5 1,91.5 5,835^ Mason Creek Lower 2 ailes 9A7 9/2U 1 2 U78 378 U26 2,U.O Wenatchee River Outlet of Lake Wenatchee to \ aile below 9/15 ?/2l4 1 2 1,591. 391. 991. l.,970 Total 36.165 19U9 White River White River North Fork 2 ailes above Confluence to lake confluence 9/8 9/11. 9/20 9/27 9/8 9/U. 9/21 9/27 1 2 0 0 19? 265 7 6 659 160 111. 213 570 1,065 Little Wenatchee River Hatchery racks to lake 9/7 9/U. 9/20 9/27 158 122 21(6 30 11.0 700 Naeon Creek Lower 2 ailes 9/8 9/11. 9/21 9/27 0 70 la 5U la 205 Wenatchee River Outlet of lake to ^ aile below 9/8 9/11 9/21 9/27 0 0 196 113 77 365 ToUl 2,925 1951 White River North Fork 2 niles above confluence 9/20 27 27 135 White River Confluence to lake 9A8 9/26 1510 U.57 298U 11., 920 Uttle Wenatchee River Hatchery racks to lake, above racks 9A9 9/19 230 12 230 12 1,150 60 Nason Creek Lower 2 alles 9/26 16 16 80 Wenatchee River Outlet of lake to i aile below 9/20 230 230 1,150 Total 17,1.95 1/ This atreaa area was cut off for two weeks by hatchery racks so the factor of . three was used. 15 Table Ij is a summary of the information showing the estimate by stream sur^reyors of the total number of square yards of suitable spavining gravels available for each section in the V/enatchee systemj the number of bluebacks which can be accommodated ^ and the n'jmber of spaxmers in each section in 19li7, ipiiSs 19h9o and 1951. It can be seen that a total of 129^,000 bluebacks could spawn in the area without crowding if they distributed themselves in proportion to area available.. However, it will be observed in table k that some stream sections support nearly maximum populations while others remain only partially usedo Altogether there is about seventy percent more suitable spawning area available than was used during the largest spaiiming concentra- tion in 19ii8„ THE OKMOGAN SURVEYS The Okanogan River system constitutes the second of the two major spawning and rearing areas for blueback salmon. In this system is Lake OsyocSj which extends north to south wj.th approximately h miles in Canada and h miles in the United States^ and the Okanogan River vrbdch flows through Lake Osoyoos. Tne major spaiming takes place in a 20-mile stretch of the river above the lake (figure 8). The upper limit of spawning is the Oliver diversion dam^ about 6 feet in height. There are no fish-passage facilities there. Approximately the same procedure was used for counting the spawners in the Okanogan as vjas used in the Wenatchee area. Table 5 is a summary of Okanogan counts, Uni"ort-inately_, flooding conditions in 19U8 made it impos= sible to make counts in most of the river area in that year. The best that could be done was to compare the areas tallied with those of 19ii7 and make an estimate of the remainder. Using the average counts and appljrlng the factor 5 as before provides estimates of lS,125 bluebacks in the Okanogan in 19li7, 35,875 in 19U8s 310 in 19ii9 and 12^2U0 in 1951, The 19ii9 light run in this section is easily explained in view of the predominance of a h-year cycle in bluebacks. In the Grand Coulee fish-transportation program no 19U1 adult blueback or brood of that year were planted in Lake Osoyoos and only hi fish (possibly made up of 3-year and 5-year fish) were seen there in 19ii5o The 19li9 run resulted from this 19u5 stock. Referring to spax-ming- gravel requirements^ table 6 gives the number of square yards avai.lable compared id.th the number of spawners during each of the h years. Note that this spawning area could accornmodateraany more fish than our raaxim,uro estimate of 19l;8o That was also the general conclusion derived from direct observation of the spawning beds. 16 TABLE h C«lcul«ted gsti»«t«8 of ATail«bl« Squara Tarda of Sultabla Spawning Oravl for Blu»b«ck Salaon in Varloua Streaa Sections of the Lake Wenatchee 1 Area Conpared t o Population Bstdjiates of lliose Areas in 19L7 - 1^1 Streaa Section Sq. Tds. of Suitable Spawning Oravel No. of fish which could be •ceomodated (using 8.b sq. yds. per pair) Bstiaai WL7 bed Spawn: IJUB Ina Populations -mr i?5r White RlTer Lower 2 alles of Worth Fork 50,000 12,000 290 10,520 570 135 White Hirer Confluence of North and South Fork to lake 151»,000 37,000 20,990 10,295 1,065 ll.,920 Little Wenatchee River Hatchery Racks to lake about ? nlles 36,000 9,000 5,610 2,U25 700 1,150 Little Wenatchee River Hatchery Racks to Falls Area 236,000 56,000 y 5,835 2/ 60 Naaon Creek Lower i miles of streaa 30.000 7,000 2,iao 2,11.0 205 80 Wenatchee Riwer Outlet of lake to i aile below 32,000 8,000 5,U0 l.,970 385 1,150 Total 538,000 129,000 31., 710 36,185 2,925 17,1.95 No flah were released beyond hatchery racks during season. 17 VASEAUX LAKE ) ROAO TO PEMTICTOM roao to UJ. 10110111 Figure 8, Diagrammatic map of the principle blueback salmon spawning areas of the Okanogan River System, 18 TAillX 5 DATA FROM 9imVKY3 OF HUIKIUCK SPAWNING IN STTKAM SBCTIONS OK THE OKAVOOAH RIVK;-, 19L7 - I9I49 and .1951 STRKAM MCTION DATE SimVKY COUNT AVKRAOE DiT«rslon d«M to first brldg* ■I n i« tf n « II It N N First to Mcond brldg* S*oond to fourth brldg* • an nan nam Fourth to fifth brldg* Fifth bridg* to lake Total 191.8 Diversion to first brldg* * i» « « An STera^ based on ratio with 19U7 counts 9/30 10/12 1,08U l,l51i 1 7,175" Total 19L9 riTersion da* to first bridge m n n n ** First bridge to fifth bridge 9/29 1 32 10/5 2 83 10/20 3 0 9/28 1 50 10/5 2 22 10/20 3 0 38 2L (X)5 10/? 10/9 10/16 1 2 2 850 1,023 378 750 3,750 10/? 10/8 10/15 1 2 3 3L1 1,231* 1,017 87U 1,370 1.0/1 10/8 10/15 10/2lj 1 2 3 h 313 1,375 2,219 555 1,123 5,615 10/1 10/8 10/15 10/2L 1 2 3 h 251. 1,171 1,17L 121. 831 1,155 10/16 1 17 1.7 235 18.125 35.f75 190 120 Total 310 1951 Diversion daa to first bridge ft If n First to second bridge f* « N Second to fourth bridge m n n n Fourtn bridge to lake 9/26 10/L 10/10 10/17 1 2 3 L L89 l.,172 1,795 865 1,'=30 9,150 9/25 10/3 10/9 10/16 1 2 I 17 376 1.065 U50 1.77 2,365 9/25 10/3 10/9 10/16 1 2 3 U 7 11? 35U 61 13L 670 lO/U 10/10 1 2 11 3 7 35 Total 12,21.0 1/ Extremely high water in 191.8 limited surveys to only a portion of were compared with counts of 191.7 and a similar ratio applied to obt&in the arf». The areas thit could be counted an estimate for 191.8 • 19 TABLE 6 CALCULATED ESTIMATES OF AVAILABLE SQUARE YARDS OF SLTTABLE 5PAVJNING GRAVEL FOR BLUEBaCKS in THE OKANOGAN RIVER COMPARED TO POPULATION ESTIMATES DURING 19U?-5l Year Number of Fish Square yards of Square yards gravel utilized of potential using dlk sq, yds, gravel avail- per pair able, 19U7 18,125 76,000 601,000 19U8^ 35,875 151,000 6oi,000 19U9 310 1,300 601,000 1951 12,2i|0 51,000 601,000 Although the seeding of spawning gravels continues to improve as exem- plified by the escapements past Rock Island Dam, the survival of the young fish plays an important part in determining the ultimate return and this can vary within wide limits. Exceptionally cold weather and reduced flows can damage the eggs of alevins by freezing and dehydration. Ice jams may scour out the gravel before the young fry are in the free-swimming stage. During the winter of 19li7-U8 information was obtained concerning the early life history of the bluebacks in the Wenatchee and Okanogan systems. Redds were selected and marked with an iron pipe driven into the stream bed. Periodic inspections were made during the winter while the spawn was in the gravel. A very small, spoon-like blade was used on an ordinary shovel handle and a fine-mesh hand-net held directly downstream from where the shovel was thrust into the gravel. The information derived from this study is shown in tables 7 and 8, As a result of the spawning-bed inspections we thought that the young of the 19li7 brood fared well with one exception. On March 3, 19^8, dead eggs were found in the Okanogan River. On fiorther investigation it was found that the river flow had been shut off at the control gate upstream just below Lake Okanogan for about a week while the dam and fishways were being rebuilt at Zosel Dam, Oroville, Washington, This probably was a contributing factor which resulted in smaller spawning counts in the Okanogan in 195l, despite larger Rock Island counts. No nest inspections were carried on during the winter of 19i|8, but it is a matter of record that the blueback areas were subject to exceptionally cold weather during that winter. 2/ Based on a ratio with 19li7 counts. 20 TABI£ 7 OBSERVATIONS OF A BLUEBACK SAI/ION NEST LOCATED IN THE IKNATCHEE RII^R APPROXIMATELT ONE-HALF MILE BELOff LAKE WENATCHEE DURING THE WINTER 19li7 - 19U8 Visit No* Date Weather Air Water Temp.Fo Tenp»F« Sample Condition River Condition 1 12/9 Clear 101,0° U3.0° 2 12/16 Snowing 31.0° U2.5° 3 12/23 Snowing 32.0° 3U.5** ii 1/5 Cloudy 3$«0° UO.O* 5 1/12 Clear 17.0** 38.5° 6 1/29 Cloudy 28.6° 37.0° 7 2A3 Part U3«5° 38,5° Cloudy 8 2/18 Cloudy 38,0° 37,0° 9 2/26 Snow 36,0° 38.5° 10 3/5 Cloudy hli.0° U3.0^ 11 3/15 Fair 50.0° U5»0° 12 3/29 Fair U8.0° U7.5^ 9 eyed eggs 11 eyed eggs Nest covered with one foot of water Sams 2 alevlns, 2 eyed Same eggs 5 in alevin stage Low, but nest covered 3 In alevin stage Same 5 In alevin stage Water level up slightly 7 in alevin stage Low but neat oovered U try egg-sao about Nest oovered with absorbed about one foot of water - no lee. 3 fry have no egg- Same sac, 2 with egg-^ac« 2 fry well advanced Same 2 with presence of egg-sac 3 fry well advanced Same 3 have evidence of Free swimming fry yolk sac seen in shallow eddies 7 fry all In well Same advanced stage were all that was found In the entire nest. 21 TABI£ 8 OBSERVATIONS OF A BLUEBACK SALIIGN NEST LOCATED IN THE OKANOGAN RIVER APHIOXIIIATELY ONE QUARTER MII£ ABOVE FIRST BRIDGE BELOW OLIVER DIVERSION DAM IKAR OLIVER, B.C. DURING WINTER 19U7 - 19U8 Visit Air Water No* Date Weather Teap«F. TenpoF« Sample Condition River Condition 1 12/18 Fair 3 h 5 li5.0° 37.5' 12/30 Clear 30.0® 36.0 lA3 Clear 27.0O 3U.0° 3/28 Clear 29.0° 3U.5° 2/20 Snowing 35.0*= 7 3/16 Fair 8 3/31 Fair 9 h/lh Fair 31;.0'= 6 3/3 Clear 39.0° 39. 0*^ U6,0° li3.0° 56.0° U8.00 ^^.O*^ U7.0® 8 eyed eggs 2 in alerin stage 2 eyed eggs 6 in alevin stage U in alevin stage 5 fry egg-sac stage 5 fry eg^^ac stage 10 try egg sac stage 9 fry egg-sao half absorbed Only 2 fry left in nest. Fry in well advanced stage Up approximately one foot since spawning Same T^ another 8" Up aunother U" Same level as spawning time River level below that of spawning tiae ^p to spawning level Saae Water badly silted Same 22 Seeding of the spatming gravel in 19^9 appeared to be successful. Since this was a small run it gave th5 i9li9 adult soawners a selection of the beot spaxvning gravel with a minimum possibility of crowding. The 19^9 run did not fare well during the upstream Migration however. Only uO percent of the bluebacks were counLed past Rock Island Darii (table 1) 5 and only a small por- tion of the remaining population reached the spawning grounds above. Seeding of the spawning grounds in 1951 probably will not be as success- ful as Rock Island counts indicate because of injuries lAiich may have resulted from partial blockage and delay at McNary Dan,. It is estimated that 8 per- cent of the females had internal injuries which affected the ripening of part or all of the eggs. Discussion on this subject will follow. Spawning conditions J otherwise^, were favorable for blueback that survived without injury during the upstream migration of 195l. SURVIVAL IN THE REARING LAKE Bluebacks normally remain during their first year in Lake Wenatchee or Lake Osoyoos and migrate seaward in their second year. Other species compete Td.th them for food and predatory fish reduce their number during the time they remain in the lakes. Experimental predatory-fish sampling by means of gill-nets was done in Lake Wenatchee during 19li9-$l to deter- mine what species inhabited the lake and to what extent they were preying on the Kokanee (landlocked bluebacks) and the young sea-run bluebacks which cannot be distinguished from each other. Four species., squawfish (Ptycho- cheilus Oregon ensis) J, suckers (Catostomus species') , Dolly Varden (Salvelinus malma) , and whitefish (Prosopium species)^ were taken by gill-net, T^ro species which were found to contain identifiable 0^ nerka (bluebacks or * kokanee) in their stomach contents, vp.re squawfish and Dolly Varden trout. A total of 113 squawfish examined contained 12 0. nerka plus a number of sculpiHj lampreys,, and unidentified partially digested fish. Thirty-nine Dolly Var- den charrs contained a total of 26 0. "nerka in their stomachs, Ro E. Foerster and W. E, Ricker (I9U2) stated that the principal food of squawfish in the Cultus Lake, British Columbia area is young sockeye salmon. Their predator-control program conducted by means of gill-netting is re- ported to have benefited the fishing industry by thousands of dollars. FUTURE 0? THE RUNS AND RECOMMENDATIONS The Columbia River blueback salmon runs face difficulties. The Canadian government is planning a flood-control project which will destroy more than 75 percent of the spawning area available to bluebacks m the Okanogan region^ The stream which now vdnds through the Okanogan valley will be straightened by channelizing and will have a series of low dams at intervals along its course. This wj.ll be for the purpose of drawing off water more rapidly from Lake Okanogan which lies to the north. Thousands of square yards of suitable spawning rubble will thus be bypassed by the new channel. 23 A plan was proposed by J. T. Bamaby of the Fish and Wildlife Service for extending the migration of blusback salmon to compensate for the less of spawning area resulting from the Canadian flood- -control program.^ The plarip however^ was not accepted by the Canadians „ It would have opened several lakes and streams which were formerly utilized by the bluebacks.. Vasea-.oXj Skaha^ and Okanogan Lakes., rJLne possible streams, and an unesti,- mated amo>aiit of lake-shore spawning area would have become available^ =-/ These areas are shown in figure 9. Tne plan proposed would have involved (1) the construction of fish ladder-s at Oliver Diversion Dam^ Okanogs_a Falls, and Lake Okai'iogan outlet, plus a series of small ladders over drop sections planned in the channel, and fish screens to protect fingerlings from becoming diverted into irri- gation ditches s and (2) relocation of the present rvns upstream into the new rearing areao From past experisnce it is regarded as very do.ubtf-al whetner the S£?_mon viould ma?fe a prespawTiing migration beyond Lake OsoyooSo The theory that bluebacks remain in the lake end proceed upstream just before spawriing Is sabstan.t-iated by earlier investigators who have stated that sockeye (blueuack) salition not only return to their own river basin at maturity but predominantly return to the particular part of the river basin in which they were reared as fingerlings (Gilbert 1917 ^ p. ^1). The run would be trapped and hauled by track to the new lakes. The most logi- cal trapping point is at Zosel Dam located at Oroville, Washington. One disadvan.tage to be tiiken into acccun,t when considering the exten- sion of spawrdng grounds was the lack of protection of blueback salmon in Canadian waters. More rigidly enforced laws are needed. In the past, snaggingj gaf'fing, and even gill-netting have been consistently in evidence in this area. These activities are undoubtedly responsible for the loss of a considerable nu'nber of spawners each jp.ar and would be ev'en more serious if the fish had a longer migra-^ion route through relatively constricted channels to the upper region. i^ A secondary proposal ey Barnaby will i'llow the blueback run to pass over drop sections to be constructed in the channel. Small fishways over these will make it possible for the s aLmon to pass upstream to the upper portion of their present spawning area not altered by the flood oonxrol project. The importance t^ future blueback runs of maintaining a Lake Osoyoos spavming and r earing area may be deomonstrated b^ ^comparing the plankton populations of Lake Osoyoos with Lake Wenatchee.2/ Young blueback salmon are principally plankton feeders. 5V This system of lakes at one time produced a substantial part of the entire blueback population of the Columbia River (Fish and Hanavan,19ii8, p. 23). 6j' "Interim report on Okanogan River, British Columbia". J. T. Barnaby^ mimeographed reporo }jy the U.S. Fish and Wildlf_fe Service. October 19$0,5 pp. 7/ Lake Wenatchee wt)uld probably have to support the entire natural spawn- ing run of blueback salmon if it became necessary to abandon Lake Osoyoos. 2U SWAN LAKE Figure 9. Map of upper Okanogan region showing possible spawning area for blueback salmon. 25 During the months of September and October 1939=UO, plankton samples were taken at regular intervals from the two lakes. A standard- tjipe plankton net >d.th a 3-3/Ii-inch orifice, a brass collection bucketj and body of No, 20 silk bolting cloth was used. In Lake Osoyoos, l6 vertical plankton hauls cf 86-foot average depth produced an average of O.Ii50 c.c. of plankton material. In Lake Wenatchee, lU vertical hauls of lU3-'foot average depth collected 0,191 c.c, of material. Siirface tows pro-vdded an average of 0.67 c.c, of plankton per 100 yards in Lake Osoyoos to C,l8 c,c. in Lake Wenatchee, A superiority of more than 2 to 1 in plankton for Lake Osoyoos deiiKin- strates the desirability of that lake as a rearing place for blueback salmon. This was also borne out by observations. Landlocked blueback (kokanee) in Lake Wenatchee are dwarfed^ averaging 5 inches in length,; whereas in Lake Osoyoos they range from 8 to lU inches. This could in part be a result of population pressure, but it could well be a direct result of difference in plankton production. The shallox'7 marginal area of Lake OsoyooSj, the warm climate,, and the surface drainage of large lal