DOWNSTREAM MOVEMENT OF SALMON IDS AT BONNEVILLE DAM Marine Biological Laboratory APR 1 7 1958 WOODS HOLE, MASS. SPECIAL SCIENTIFIC REPORT-FISHERIES No. 236 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 Department of the Interior, Fred A. Seaton, Secretary Fish and Wildlife Service, Amle J. Sucmela, Comissioner DOVOISTREiM MOVSffiNT OF SAUfONIDS AT BOHHEVILLE DAM lay Joseph E. G&uley, Raymond E. Anas and Lttvis C Schlotterbeck Fishery Research Biologists Bureau of Commercial Fisheries Special Scientific Report— Fisheries No. 236 Washington, D. C January 1958 ABSTRACT At Bonneville Deun most downstream-migrant salmonlds were ca\ight during hovirs of darkness during the years 19^6, 19^9, 1950, and 1953. In 1952, however, the majority were day migrants. Hourly fishing in 1952 and 1953 indicated that laaxlmum movement of chlnook salmon and steelhead trout tends to occur at dawn smd dusk; additional data are needed for blueback emd silver salmon. Although the data are far frcBB conclusive, the percentage of chlnook salmon that migrate at night appears to he more highly correlated with turbidity than with days elapsed from start of sampling. Other factors, which imdoubtedly affect day -night migration, were not tested. TABLE OF CONTEHTS Page Methods 1 Hourly movement 3 Chinook fingerllngs 3 Chinook yearlings ^ Bluebacks 3 Silvers 5 Steelheeuls 6 Discussion of hoiirly movement 6 Day and night movement 7 Canparison between 1952 and 1953 7 Factors affecting movement at Bonneville 7 Susmary and conclusions 10 Literature cited 10 FIGURES Nos. 1. Location of the fingerllng bypasses and bypass traps at Bonneville Dam 2 2. Diagrammatic drawing of an auxiliary -water screen pit showing positions of fingerling bypasses and fingerling traps 2 3. Hourly catches of chinook fingerlings in 1952 and 1953* Each hour represents the summation of the year's catch for that hour 3 k. Percent of chinook fingerlings caught each hour during four 72-hour periods in 1953 3 5. Hourly catches of chinook yearlings in 1952 and 1953* Each hour represents the summation of the year's catch for that hour 5 6. Percent of chinook yearlings caught each hour during three 72-hour periods in 1953 5 Figures - Cont'd Nos. Page 7. Hourly catches of bluebacks in 1952 and 1953* Each hour represents tha suimation of the year's catch for that hour 5 8. Hourly catches of silvers in 1952 and 1953* Each hour represents the sunaaation of the year's catch for that hour 6 9. Hourly catches of steelheads in 1952 and 1953* Each hour represents the suamation of the year's catch for that hour 6 10. Percent of steelheads caught each hour during tvo 72-hour periods in 1953 6 U. Percent of night-migrant chlnook fingerlings and yearlings plotted against numbers of fish (1952 and 1953). Lines shown axe the least-squares fits 8 12. Percent of night-migrant chinook fingerlings and yearlings plotted against days from start of sampling (1952 and 1953). Lines shown are the least-squares fits 8 13. Percent of night -migrant chinook fingerlings and yearlings plotted against Secchi-disk readings (1952 and 1953). Lines shown are the least-squares fits 10 TABLES 1. Hourly catches of downstream-migrant seLLmonids in 1952. Each hour represents the suomation of the yeea*'8 catch for that hour ^ 2. Hoxirly catches of downstream -migrant salmonids in 1953* Each hour represents the summation of the year's catch for that hour h 3. Numbers of downstream-migrant salmonids caught within sampling periods at Bonneville Dam froa 19^-1953 3 DOWNSTREAM MOVEMENT OF SAIMONIDS AT BONNEVILLE DAM Bonneville Dam is the first structure across the Columbia River that adult salmon and steelhead trout sunnount on their spawn- ing migration, and the last one that down- stream migrants pass on their way to the ocean. The spillways and turbines of the several dams completed, under construction, or planned for the Columbia and its tribu- t€a*ies present a series of hazards to the young fish. Information on the time of day when seaward migrants move downstiream may be useful in the development of methods of guiding them safely peist these structures. If dame kill or injure significant numbers of migrants, adjustments might be made at critical hours to allow safe passage. For example, if the turbines are less hamful to downstream migrants than the spillway at Bonneville, closing spillway gates for short periods to coincide with peak down- stream movement or when releeises from hatcheries are moving past the dam would allow more fish to peiss through the tur- bines and thus minimize losses. This report contains data collected at Bonne- ville which may be useful as a guide for protecting downstream migrants in this way. Earlier investigators detenained that salmonids migrate seaward in much greater numbers at night than during the day (Bar- naby, l^kh; Hoar, 1951; Oregon State Game Commission, Fishery Division, 1952). Foerster (1929) noted that downstream- migrant sockeye salmon (Oncorhynchus nerka) migrated only at night at the start of the run, all during the day at the peak of the run, and only at dawn at the end of the season. Data collected at Bonneville in the present study indicated that, at least for some species, maximum movement occurs at dawn and dusk, and althou^ most downstream- migrant salmonids move past the dam at night, some migrate during the daytime. Members of U. S. Fish and Wildlife Service collected all the data used in this report. H. B. Holmes, K. G. Weber, and C. J. Burner reviewed the maniiscrlpt and made extremely helpful suggestions. METHODS The f ishways at Bonneville Dean have auxiliary-water systems that transport several hundred c.f .s. of forebay water to the fishways and fishway collecting systems through valve -controlled conduits. This water provides additional flow to attract upstream migrants into the fishways. Before the auxiliary water enters the conduits, it is screened to keep out debris and fish. Bypasses carrying 10 to 15 c.f.s. were designed for sach screen pit when the dam was constructed to provide a eafe down- stream route for fish that entered the auxiliary-water systems. Figure 1 shows the location of the auxiliary -water systems and fingerling bypasses. Inclined -plane fln- gerling traps, designed by the Service, were placed in all of the bypasses except the one at the head of the Bradford Island fishway. These traps capture all migrants that pass through the fingerling bypasses and counts of each species in the hourly catches of these traps provide the data on day and night movement past the dam of the seaward -migrant fish. An advantage of the inclined -plane trap is that it does not interfere with the flow through the bypass and no migrants elude the trap when it is raised to collect the live fish. Figure 2 is a diagrammatic drawing of an auxllisury-water screen pit showing the positions of the conduits, screens, bypfisses and inclined -plane fin- gerling traps. No catch data from Teinner Creek by- pass, which has not been sampled since 19^, are included in this report. The following species were studied: Chinook (Oncorhynchus tshawytscha), blue- back (O. nerka), and silver (O. kisutch) salmon, and steelhead trout (Salmo galrd- nerii) . In this report chinook finger- lings are defined as chinook salmon that migrate seaward during their first year of life, wherecus chinook yearlings migrate seaward during the spring of their second year. Adult steelhead trout returning to WASHINGTON n«urt 1. "Location of the flngerllng bypaBM» and byp*»» tx»p« At Boonerllle Das A= Auiiliory water screens B= Fingerling bypass C = Fingerling trops Stop logs Collecting pot Discharge to toil- water below dom •cnu pit •tamljB* pcMltlooa of flacarUat tiypMMa ud flaflirlliic trap*. the ocean are^ In a sense, dovnstreaB migrants. Only Juvenile downstream migrants are considered in this report. Although the percentages of night migrants in 1952 and I953 differed, the hourly catches reached their maxima at the same hours. HOURLY MOVafflHT The hourly catches of all species are listed in table 1 for 1952 and In table 2 for 1953. The catches in table 1 represent four periods (April 9-11, April 22-25, April 28 - May 1, and May 5-7) totalling 2I4O hours of sampling; the catches in table 2 represent four periods (March IO-I3, April 20-23, April 28 - May 1, and May '^-7) totalling 288 hours of sampling. These periods were selected because migrants were most abundant on those dates. Hourly sampling was limited to two traps (one in the powerhouse channel and the other in the spillway channel) because only one observer was available for each 8-hour shift. Chinook Fingerlings Chinook fingerlings in both 1952 and 1953 were caught in greatest numbers during early morning and early evening hours (figure 3). In both years the pesik morning hour was 6 to 7 a.m. and the peak evening hour, 7 to 8 p.m. The catch drops off rather sharply on both sides of these hours. \2 1 1 -I— I- T- I I 1 I I I 1 1 1 1 ) T — 1 — 1 — - - II 1952 : 3342 FISH 10 - — - 1953 4107 FISH w - 9 I w8 _ \ - ^7 Ll. °6 - h\ 1 A 1 \ ' / \ 1 ^5 2 ^N -^ 1 \ \ V A \) 1 0 _j 1 1 1 J 1 1 1 1 .1 1 1 1 1 1 1 1 1 1 L. J 1 1 — 12 2 4 6 8 10 12 2 4 6 8 10 12 AM HOUR PM Figure 3" — Hourly catches of cfainook fin- gerlings in 1952 and 1953- Each hour represents the summation of the year's catch for that hour. Four 72-hour periods were plotted for 1953 (figu« k). From March 10 to March 13 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 1 1 I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 : li \ 1 '1 '•! ■ f 1 m - ^ n 1 \ 1 1 1 1 1 1 1 1 1 1 f 1 1 r 1 M K 1 1 1 \ 1 1 12 2 4 6 8 10 12 2 4 6 8 10 12 AM PM HOUR MARCH 10-13 I 273 FISH APRIL 20-23 275 FISH APRIL 28-MAYl 2380 FISH MAY 4- 7 179 FISH FlguTs k. -Parcent of Chinook f logarlin^s cau^t each hour during four 72-bour periods In 1933- sunrise was about 6:15 a.m. and sunset about 6:15 p.m. The catch peaked at 7 a.m. and 7 p.m., which coincides with the hours of dawn and dusk. The three periods from April 20 to May 7 bad smaTI morning peaiks, all earlier than 7 a-m. A wellnnarked peedc occurred in all three periods at 8 p.m. S\mrise during these periods was between k:iO and 5 a.m., and sunset between 7 bjoA 8 p.m. There were too few fish in seme of Table 1. — Hourly eatcbsB of dovnstrean-mlgrant salmoalds In 1952. Each bour represents tbs sumnatlon of tbs year's catch for that hour. Hour ending Chinook Chinook BltMbacks savers Steelheads Total at flnserllnKS yearlings 12 96 25 11* 6 25 166 JU4 1 93 31 11 6 27 168 2 123 36 9 11 18 197 3 102 29 11 3 27 172 i» 135 to 11 12 23 221 5 106 38 13 10 31* 201 6 221 65 9 5 92 392 7 300 56 19 7 1^ i»a8 8 201 k2 8 7 li6 30li 9 200 35 5 8 k9 2y/ 10 188 39 13 8 5k 302 11 130 35 8 5 33 211 12 115 29 11 2 39 196 Hi 1 119 36 9 7 5^ 225 2 76 36 10 8 k5 175 3 96 33 Ik k 38 185 k 109 ia 8 3 k9 210 5 9^ 38 8 5 26 171 6 100 33 11 2 30 176 7 121 29 9 2 19 180 8 256 '•9 8 9 3^ 356 9 171 56 12 2 31 272 10 107 32 13 7 21 180 11 83 35 7 5 32 162 Total 3,3^2 918 251 Ikk 892 5.5l^7 Table 2 Hourly catches of downstream-migrant salaooids in 1953> Each hour represents the suaaation of the year's catch for that bour. Hour enfling Chinook Chinook at fingerlings yearlings Bluebacks Slivers Steelheads Total 12 151 26 k 5 37 223 AM 1 136 30 5 1 20 192 2 183 27 6 5 35 256 3 200 29 3 2 32 266 k 170 38 k 10 30 252 5 190 50 2 6 26 276 6 173 51 1 3 39 267 7 317 18 . 6 13 351* 8 131 18 1 - 15 165 9 127 19 2 3 26 177 10 109 21 6 7 13 156 u 121 22 3 3 22 171 12 92 28 2 Ik 136 HI 1 113 33 3 1 20 170 2 99 29 6 1 16 151 3 85 19 1 3 20 128 k 82 19 2 1 13 117 5 15't 12 3 2 10 181 6 91 13 1 3 19 127 7 331* 10 - k 19 367 8 1.89 1*9 9 6 52 605 9 257 31 6 6 37 33r 10 157 33 10 k 29 233 11 ll»6 21 8 7 35 217 Total l»,107 6U6 88 89 59^* 5,524 the periods to plot 1952. Chinook Yearlings The catch of Chinook yearlings peaked in the morning and evening in both years (fig. 5). The morning peak was at 6 a.m. in both years, which is 1 hour eaxlier than that for fingerlings. The evening pesik in 1952 was at 9 p.m., and in 1953 a* 8 P-ni- 10 0 I I I I I I I I I I I I I I I I I I I I 1952: 918 FISH 1953 : 646 FISH I I I I I I I I I 1_J I I 1 I — I — I — I — I — I — I — I — L 12 2 4 6 8 10 12 2 4 6 8 10 12 ^■^ HOUR •'^ Fi^ura i Hourly catches of Chinook ysarllsgs In 1953 and 1953- Each hour repreeants the sumatloQ of the y«ar*B catch for that hour. Three 72-hour periods in 1953 were plotted, and morning and evening peaks are evident. The morning peaks did not coin- cide, but occurred at k, 5> and 6 a.m. The evening peaks coincided at 8 p.m. The period from May k to May 7 had a slightly higher 2 p.m. peak than the one at 8 p.m. (fig. 6). Bluebacks A morning peeik of bluebacks at 7 a.m. occurred in 1952, with the catch gradually diminishing during the succeeding hours. The 1953 data were opposite with noticeable evening and night peaJis (fig. 7). Addi- tional data are needed to detenaine If this graph accurately defines hours of downstream movement. Silvers In 1952, silvers peaked at 2 and k a.m. ; the third highest mode occured at 8 p.m. (fig. 8). After the k a.m. peak the catch fluctuated widely with morning 1 — 1 — I — 1 — 1 — I — 1 — 1 — 1 — I — I — 1 — 1 — I — I — I — I — I — I — I — I — I — r 2 2 4 6 8 10 12 2 4 6 8 10 12 AM HOUR PM APRIL 20-23 114 FISH APRIL 28-MAYI 165 FISH MAY 4-7 364 FISH Figure 6. — Percent of chinook yearlings caught each hour during three 72-hour periods in 1953. 12 I I 10 9 8 7 6 T ' I I I — I — I — I — t I I — I — I — n — n — I — I — I — I — I — r « 1952 : 25! FISH - — 1953 : 88 FISH \ ;\- 12 2 4 6 8 10 12 2 4 6 8 10 12 AM PM HOUR Figure J. — Hourly catches of bluebacks in 1952 and 1953- Each hour repre- sents the summation of the year's catch for that hour. T — I — I — I — I — I — I — I — I — I — 1 — I — 1 — I — I — I — I — I — I — I — I — I — r 1952 : 144 FISH — - 1953 : 89 FISH 12 2 4 6 8 10 12 2 4 6 8 10 12 AM HOUR PM Figure 8. --Hourly catches of allver* in 1952 and 1953- Each hour representB th« suamatloa of the y«ar'0 catch for that hour. II 10 — 1 — r —1 — 1 — 1 — \ — 1 — 1 — 1 — 1 — ! — r—r -T — 1 — r — 1 — \ — r- -1 — 1 — 1 — 1— - 1 1952 :892 FISH - 9 - 11 -— 1953 : 594 FISH 1' x8 CO - ;\ U.7 - 1 * li. ' ^ ) \ Ob ' N /"' 1 \ * \ r >--, < ' \ ' '^ V / ^ I \/ \ . LU 1 \ / V \ J - o4 '\l 1 \ I - a: . V / 1 ' \ A \ ' r\ A- UJ^ /v/ ' A \y\'' / \ A a.- A /^ \. ^' \ / y V - 2 1 n M 12 2 4 6 8 10 12 2 4 6 8 10 12 AM ^^ouR PM Figure 9> — Hourly catches of steelheads in 1952 and 1953- Bach hour re- presents the sunmation of the yeeir's catch for that hour. peaks at 7> 9, and 10 a.m. Because compara- tively few fish vere taken, these hours may be of no slgnlflccmce. Steelheads Well-marked peaks of steelheads occurred at 6 a.m. in 1952 and 1953* hut only 1953 had a noticeable evening peak (fig. 9). Two 72-hour fishing periods in 1953 having similar hours of sunrise and sunset were plotted. Both periods have peaks at 8 p.m. , but the morning periods lack any discernible modes (fig. 10). Discussion of Hourly Movement Hourly fishing of the flngerllng traps in 1^2 and 1953 indicates that at dawn and dusk there is an increatse In the migration rate of most downstream^ilgrant salmonids at Bonneville Dam. Chinook fln- gerlings and yearlings showed dawn and dusk peaks in both years. Steelheads had a morning peak in both years, but an eve- ning peak only in 1953- Silvers and blue- backs exhibited a tendency to migrate at all hours. The data on hourly migration are not conclusive because too few years have been sampled; they are nevertheless indicative of migration behavior. ID 1 1 1 1 1 1 1 1 -I— 1 — 1 — 1 — t— 1 — 1 — 1 — 1 — 1 — r — 1 — 1 — 1 — r- 1 - f\ 9 - l\ - 1 \ x8 :f7 1 > A ^' i Ll. T 1 ^ 1 \ h \ \ *■ 1.6 \ \ w m t \ \f\ o -' ' xV / "\ A \ V ' k5 2 uj4 -* ' /A / \>' / \ / '\ A '' / \ / 'I / \A A /^ : yv: o -\ / \ / \ \ \ / \ * / \ / - a. v \/ A \ J !%\l, ^ - 2 V \ — /' - 1 - - n 1 1 1 1_1._] — 1 — 1 — 1 — 1 — 1 — L 1 1 1 j_ 12 2 4 6 8 10 12 2 4 6 8 10 12 AM PM HOUR — APRIL 28- MAY I 323 FISH — MAY 4- MAY 7 258 FISH Figure 10. --Percent of steelheads caught each hour during two 72-hour periods in 1953- DAY AND NIGBT MOVIMENT Comparison between 19^2 and 1953 Sampling from I9U6 to I95O indicated that although most downstream-migrant salmonids passed Bonneville Dam during hours of darkness, some move seaward during daylight hours. The hourly data collected in 1952 and 1953 were separated into day (5:01 a.m. to 7 p.m.) and night (7:01 p.m. to 5 a.m.) periods. These hours were chosen because they coincided best with the hours preceding daybreak and following nightfall; in this way no daylight was in- cluded in the night period. The trap catches in 1952 had more daytime than night migrants even though the hourly data showed modes at dawn and dusk in both 1952 and 1953. The numbers of Chinook yearlings, bluebacks, and sil- vers were not significantly different (P "^ .05) between the day and night periods in 1952; more chinook f ingerlings and steelheads were caught during the daylight than the night period (P<..01). Although the time of year and duration of fishing periods in 1953 were similar to those of 1952, all species were caught in signifi- cantly greater numbers (P<: .01 for all species) during the night periods in 1953- The chi-square test was used to detemine the significance of the differences be- tween day and night periods. Table 3 susmarizes the data for each year. Sampling in 19'*'7, 19^, and I95I was not possible because other experlaents were being conducted during those years. The dally sampling periods were changed because of the exploratory nature of the sampling program. Factors Affecting Movement at Bonneville factors that might affect movement aire (1) operation of the dam, (2) races of fish, (3) size of migrants, {k) number of migrants, (5) weather conditions, and (6) physical variables of the river (flow, temperature, and turbidity). Operation of the dam introduces vari- ables which are very difficult to evaluate. Sane of these, such as changes in the spill- way gate settings and powerhouse operations, are changed over short intervals of time and might affect catches. At night the demand for power drops and the flow of water decreases eis one or more generators are closed down. At such times, spillway gates may be opened to keep the water level below the top of the spillway gates. Thus, flow conditions in both channels are altered and migration patterns KRy be Euffected. Varia- tions between traps and also any daily differences in catches of the same trap may be caused by operational changes of the dam, but the volume of auxiliary-water, which draws the fish into the bypass areas, is seldom changed over short periods of time, and hence should not affect movement of the fish within dally periods. Another possible variable is the dif- ferent behavior of races. Rich (1920) states there is evidence that Juvenile Columbia River chinooks from pajrticuleur tributaries tend to migrate at the same time and school together during the seaward migration. At present there is no practical way to distinguish races at Bonneville; hence, this variable was not tested. Salmon are released by several hatcheries above Bonneville. The distribution of hatchery fish in the river may be different from that of the wild migrants at the time they pass the dam. Many releases migrate past Bonneville within a short period of time; thus, the proportion of migrants caught by each trap would be affected by such schools of fish. Several factoirs influence movement of each species at Bonneville, resulting not only in variations in the proportions migrating within periods of time, but also variations in the catches of each trap. This variability in trap catches, although expected, makes interpretation of the data difficult. It is assumed here that the combined catches of the trapc gives the best estimate of the relative numbers of migrants passing the dam. Seme of the The size of migrants may be closely associated with races and time of year; insufficient data are available for a study of this variable. The effect of weather conditions on migration at Bonneville would be difficult to separate and analyze, becaxise the weather is so closely «i8SOCiated with other vari- ables such as condition of the river and corresponding operation of the dam. ca •s OOOJ 1 1 * * 1 1 Q CO H ^ l/N 6 ir\ 1 x> ITNH H CJ -* ON -d- O h3 H OJ H H •A § 5 ^ 3) o •<-) -1 1 CO oo 00 O f^^ OJVO ON 3- H Jf t>- PlPO 5 •H 11 ^S ^ CO ITNPO •8 > "« •H t a O -H A 1 CVJ o\ hI O OJ 1 CO ON 2 •:< If &4 AS s^ &^ CVJ t^ o o 1-^ •H o on H ON OJ H OJ OJ 1 %H-^ k ^■^ coco ON■ •0 3 ^ '^1 \0VD H H H H H H %c +> n o s 1 EH • • • • • • • • o downi 1lle ; a a • • a a • • sS a a • • a a • • o •H VO vo VOVO ^ b t— if\ t— ITN x> *H > h t 1 1 1 1 1 1 1 4) +> og s a a • • a a 1 CO • • a a • • a a sS Number at Bon >> • ■ • • H H • • H H • • 1^ ^ o o O O g§ O O o o ^;, 1 vO vb VO VD DJ do UN r- ir\ t— • 55 CO +> 4> :5 ON o n H o\ ON ITN CVJ CO g: H H ON l/N iO ^ "O H OS ON 4) •^ •>. H H MtH • •p 8 • ??^ t— •H 09 p< ^ ^ ^ >> o :» •o 55 ^ a^ S 1 ^H "O o •H U 1 • 8? • 1 • o H • 1 O H 52 o3 ^ ^ U tf % s s X < s 8 The aumber of fish migrating might iiffect the proportion moving at night, but no correlation coefficient wets computed for this variable because the components are interrelated (Snedecor, p. l62). The fia- gerllng trap catches may not depict the exact number of migrants that pass Bonne- ville Dam, but it is assumed here that the data approximate the abundance of migrants during the periods studied. In all years except 191+6 the periods were of relatively short duration. Figure 11 shows the leswt- squares regression lines for Chinook flngerlings and yearlings ccmparing aumber of fish and proportion of night migrants in 1952 and 1953- On the hypothesis that day-night movement may be associated with time of year, dates were selected when samples of Chinook salmon were sufficiently large to test in 1952 and 1953 (March 1 for finger- lings and April 1 for yearlings). Sampling extended about 95 days for flngerlings and about 35 days for yearlings. Least-squares regression lines were plotted (fig. 12) and correlation coefficients were computed. The correlation coefficients for flnger- lings (0.104; P>0.50) and yearlings (0.352; P>0.1)O) were not significant. This vari- able might be correlated with size of fish because the size of the migrants changes gib the season progresses but seems not to be true. 2 4 6 8 10 12 14 16 16 20 22 24 26 28 30 NUMBERS OF FISH (HUNDREDS)- CHINOOK FINGERLINGS 1 1 1 1 1 1 1 1 I I r J I L. 30 90 150 210 270 330 390 450 NUMBERS OF FISH - CHINOOK YEARLINGS riguifi 11. --Percent of nl^t-nl^ivnt cUnook flogerllnge aod yearllnge plotted acaljut niaben of flab (19^2 and 1993)- Lines ihovn ai« the leaet-iqu&ze fits. 10 20 30 40 50 60 70 80 DAYS FROM MARCH I CHINOOK FINGERLINGS 0 10 20 30 40 50 DAYS FROM APRIL I CHINOOK YEARLINGS flours. 12--PBrc*Dt of nl^t-mleraDt cMnook fljigorllJigB and yearllngB plotted agalnat daya frca start of saflpllug (19^2 and 1953). Llnea tbcnru are the laaat-squ&re fits. River flow and water temperature, which may influence the total number of fish migrating over long periods of time, probably do not change the pattern within 24-hour periods. River flow does alter conditions at the dam to the extent that it governs operation of the spillway gates and, to a lesser degree, operation of the powerhouse; in this way it might be a secondary cause of variations in movement of seaward migrants. The river condition most apt to influence day-night movement of salmonids is turbidity, because light penetration of the water is affected. The chinook fln- gerlings in 1952 and 1953 were abundant enou^t to fonn eight groups for statistical analysis, and the yearlings seven groups, thus permitting the fitting of regression lines by the method of least squares and computing coefficients of correlation be- tween several factors, as shown in figure 13. The other species were not tested because some of the periods had few fish. Secchi-disk readings and percent night migrants were lowest in 1952. The corre- lation coefficients for fingerlings (O.65I; P>0.20) and yearlings (0.663; P>0.30) were not significant at the five percent level. It is realized that the lack of data precludes the acceptance of any of these values £18 facts, but comparison of the P- values siiggests that within the limits encountered in this report the percentage of night -migrant chinook salmon is more highly correlated with turbidity than with days elapsed from start of sampling. SUMMARY AND CONCLUSIONS 1. Inclined-plane fingerling traps, located in the fingerling bypasses of Bonneville Dam, were used to collect all of the data in this report. 90 1 1 1 1 1 1 U) ^ 80 - < a: 70 - 13 ^- — " S 60 • ^_„,— -"■"''^ ■ H ^ i 50 • ^___---''''''^ - 0 • ^_,„,— ' 2 40 ^,^-^''''^ • ■ 1- g30 • • 0 F. 20 . UJ 0. Y = 0.33+0II7X 10 n 1 1 1 1 1 1 05 10 1.5 20 25 SECCHI DISK READING (FEET) CHINOOK FINGERLINGS 3.0 1 1 I 1 < 1 H z < 80 ■ a. 5 70 • ^^ s • ^ — ^60 ^.^^^^ X ^^---'''''''^ u 50 • ^^^^"^ z ^^--■^^ 40 ^^„.--^ • K z • ti 30 - ■ 0 £ 20 - ■ a. 10 n Y=0 32 + 0 130 X L.I.I 0.5 1.0 1.5 2 0 2,5 SECCHI DISK READING (FEET) CHINOOK YEARLINGS 3.0 Pl«uj« 13. --Perc4at of nl^t-al^rant cMnook flD^rlla^ ODd yvarlln^ plotted afialjut Gacehl-dlmk rsadlnga (1952 and 1933). LljM* ■Jtoim are th* leaat-aqu&n flt«. Hourly sampling in 1952 and 1953 indi- cates that chinook salmon and steelhead trout increase their rate of downstream migration during the hours at dawn and dusk. Additional data are needed for blueback and silver SEilmon. Although the correlation coefficients were not significant, the data suggest that the relative numbers of chinook salmon which migrate at night are more closely associated with varying tur- bidity of the river than with time of year (or advance of the migration period). Data collected at Bonneville Dam indi- cate that, although in most years downstream-migrant salmonids tend to migrate predominantly at night, some years may have more day migrants. 5. A knowledge of the proportion of down- stream migrants sampled by the finger- lings bypasses would increase the value of the data In this report. LITERATUBE CITED Bamaby, J. T. 1950. Fluctuations in abundance of red salmon, Oncorhynchus nerka (Wal- baum), of the Karluk River, Alaska. U. S. Dept. Interior, Fish. Bull. Fish and Wildlife Service., vol. 50, pp. 237-295. 10 Literature Cited - Cont'd Foerster, R. E. 1929- An investigation of the life history and propagation of the sockeye salmon (Oncorhynchus nerka) at Cultus Lake, British Columbia. No. 3 - Ihe downstream migration of the young in I926 and 1927- Biol. Bd. of Canada, Contr. to Canadian Biol, and Fish., New Series, vol. 5, no. 3* pp. 57-82. Hoar, W. 1951. The behavior of chxmi, pink and coho salmon in relation to their seaward migration. Jour. Fish. Res. Bd. Canada, vol. 8, no. ^4^, pp. 241-263. Oregon State Game Ccmmission, Fishery Division 1952. Annual Report. 308 pp. Rich, W. H. 1922. Early history Euid seaward migra- tion of Chinook salmon in the Columbia and Sacramento Rivers. Bull. U. S. Bur. Fish., vol. 37, 1919-1920, pp. 1-74. Snedecor, G. M. 19^6. Statistical methods applied to experiments in agriculture and biology. The Iowa State College Press, Ames, lova, 4th ed., 485 pp. u INT-DUP. SEC. WASH.. D.C.3061* 1 MBL WHOI Library - Serials 5 WHSE 0 17