Special scientific report

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.

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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.

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SECCHI DISK READING (FEET)
CHINOOK FINGERLINGS

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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*

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