TRANSACTIONS
of the
AMERICAN
¾OLUME
FISHERIES SOCIETY
Trout
and
Salmon
NUMBER
Movements
in Two
Idaho
100
3
Streams
as Related to Temperature, Food, Stream Flow,
Cover, and Population Density•
T. C. BJORNN
Idaho CooperativeFishery Unit
University o/ Idaho
Moscow, Idaho
ABSTRACT
Many juvenile salmonand trout migrated from the Lemhi River drainage each fall-winterspringperiod. Seawardmigrationof anadromoustrout and sahnonnormallyoccurredin the
springbut pre-smoltanadromous
and non-anadromous
fishesalsoleft the streamusuallybeginning in the fall. ! compareddata on temperature,food abundance,streamflow, coverand
populationdensitywith movements
and conductedfield and laboratoryteststo determinereasons
for the two types of movements.
Smolts of the anadromousspeciesmigrated for an obvious reason but none of the factors
I examinedappearedto "stimulateor release"their seawardmigration. Movementfrequently
coincidedwith changesin water temperatureand streamflow, but I could not establisha consistent causal relationshipand concludedthat photoperiodand perhaps growth must initiate
the physiologicaland behavioral changesassociatedwith seaward migration.
Non-anadromousand pre-smolt anadromousspecies emigrated from the streams for different
reasonsthan the smolts. I postulatedthat fish found the stream environmentunsuitable during
the winter. Stream temperaturedeclined in the fall as fish began moving from the streamsbut
I could not induce more fish to stay in test troughs with 12 C water versus troughs with 0-10 C
water. Fish emigrated before abundanceof drift insectsdeclined in winter. Emigration occurred
in spite of the relatively stable flows in both streams. Population density modified the basic
migration pattern by regulating the number and percentageof fish that emigrated and to a
limited extent time of emigration.
Movements
of non-smolt
trout and salmoncorrelatedbestwith the amountof coverprovided
by large rubble substrate.Subyearlingtrout emigratedfrom Big SpringsCreek which contained
no rubble substratebut remainedin the Lemhi River which did. In both field and laboratory
testsmorefish remainedin troughsor streamsectionswith large rubble substratethan in troughs
or sectionswith gravel substrate. Trout and salmonin many Idaho streamsenter the substrate
when streamtemperaturesdeclinedto 4-6 C. A suitablesubstrateprovidingadequateinterstices
appearsnecessaryor the fish leave.
smolt and non-anadromous fishes move down-
INTRODUCTION
Both anadromous and non-anadromous sal-
streamduring the fall, winter and spring
monidsmigrate extensivelyduring the fall, (Chapmanand Bjornn, 1969) and somerewinter and spring seasonin many Idaho turn upstreamin the springand early summer
(Bjornn and Mallet, 1964). I compareddata
streams. In addition to the normal seaward
movementof smoltsin the spring, many prex Funds for these studiesprovided by Idaho Fish
and Game Departmentthrough Federal Aid to Fish
RestorationProject F-49-R and U.S. Bureau of Sport
Fisheries and Wildlife.
423
on movements of fish in the Lemhi River and
Big SpringsCreek (1962-1969) with various
environmental factors and conducted field and
laboratory tests to determinewhich factors
caused or influenced the movements.
424
TRANS. AMER. FISH. SOC., 1971, NO. 3
FmtJaE2.--Monthly range and meanheight of water
on gauge boards at Big Springs Creek and Lenahi
River weir sites.
mous rainbow trout), chinook salmon (Oncorhynchustshawytscha),brook trout (Sal-
Fmuaz 1.--Map of the Lemhi River drainage with
location of fish weirs.
velinus]ontinalis), Dolly Varden (Salvelinus
malma), mountainwhitefish (Prosopiumwilliamsoni), sculpin (Cottus sp.), and dace
(Rhinichthyssp.). Usually I could not distinguishbetweenanadromous
andnon-anadromous rainbow trout and I used the term rainbow-steelhead trout when I believe both forms
participatedin the movements
described.
In the studystreamsbehaviorof salmonids
changedfrom active feeding and territory
occupation(or hierarchies)in the summerto
"hiding or hibernation"in the winter. Few
fish left the studystreamsduring the summer
but with the onsetof fall, requirements
of the
fish apparentlychangedand an environment
which fish found suitable in the summer be-
camelesssuitableand they beganto leave.
THE
STUDY
STREAMS
The Lenahi River (90.3 km long) flows
through a broad mountain valley into the
Salmon River at Salmon near the east central
border of Idaho (Figure 1). Big Springs
Creek (8.0 km in length)parallelsand enters
the Lemhi River 77 km from its j unctionwith
the Salmon River.
The Lemhi River falls an
averageof 6.7 m/km.
I classifybothstreams
asrelativelyproductive on the basisof total dissolvedsolids (273
and298ppm) andbicarbonate
alkalinity(134
and 160 ppm) in the water.
I found the followingfish speciesin the
studystreams:non-anadromous
rainbowtrout
(Salmo galrdneri), steelheadtrout (anadro-
Stream
Flow
The volumeof flow in the studystreams
usually fluctuated within a narrow range
(Figure 2). The water level in Big Springs
Creekfluctuateda maximumof 0.85 m during
1965-68, and that in the Lemhi River 0.61 m,
but levels changedless than 0.30 m most
months.Big SpringsCreekdischarged
0.8-1.0
m3/sec(0.79-0.82m on gaugeboard) andthe
Lemhi River 3.4-5.0 m3/sec(0.30-0.37 m on
gaugeboard) duringwinter. I estimated
the
volumeat 17.0 m3/secin the Lemhi River at
the weir duringpeak dischargein June,1965.
Maximum flows exceededminimumflows by
lessthan 10:1 in all years and 2:1 in some
years. Maximum dischargesof many other
Idaho streamsfrequentlyexceedminimum
flows by ratios of 30-100:1.
Use of Lemhidrainagewaterfor irrigation
influenceddischargepatterns in the Lemhi
River and Big SpringsCreekmore than any
other factor. Peak dischargeof snow-melt
normallyoccurredin late May andearly June,
the sameperiodthat largescaleuseof water
for irrigationbegan. Farmerswithdrewwater
BJORNN--TROUT
AND SALMON MOVEMENTS
from both the studystreamsand their tributaries.
Flow in the tributaries
70 LEMHI
RIVER
exceeded the
needs for irrigation and entered the study
streamsin large quantitiesin yearswith deep
snowpack in the surroundingmountainsand
abnormallylarge amountsof precipitationin
the valleysduringMay and June (Figure 2-1965). Irrigationwaterspreadon the alluvial
fansin the valley,enteredthe studystreamas
groundwater2-6 monthslater, and increased
the flow in the studystreamsduringthe late
summerand fall. In Idaho drainageswithout
irrigation,flowsnormallydeclinedthroughout
the summer, fall and winter. The small
amountof precipitation(lessthan 25 cm per
year) which fell in the Lenahi valley also
contributed
flow.
425
to the small fluctuation
o•
SPRINGS
•o•
CREEK
•o•
o
FtGuar &--Monthly range of maximum and minimum stream temperatures at the Lemhi River and
Big Springs Creek weir sites.
in stream
Aquatic Vegetation
Hornedpondweed(Zannichelliapalustris)
andbuttercup(Ranunculus
aquatilus)formed
densemats of vegetationin the upperLemhi
Temperature of the study streams at the River and Big SpringsCreekduringthe sumweirs followeda relativelyconstantseasonal mer andfall months.The vegetationdied and
patternfrom year to year (Figure 3). Fluc- driftedfrom the streamsduringthe fall and
tuations in mean monthly temperaturesbe- winter and the streamslackedvegetationfrom
tweenyearsdid not exceedmorethan 1-2 C.
late winter to June when new plant growth
Maximum and mean temperaturesof Big began. The matsof vegetationfilled the shalSpringsCreek usuallyexceededthoseof the low stream channels,increasedwater depth,
Lemhi River at the weir, probably because decreased
velocity,and providedmid-stream
more cool ground water enteredthe Lemhi cover for fish and invertebratesduring the
River.
Water Temperature
summer
Daily fluctuationsin temperatureranged
from nothingin the winter when ice flowed
in the streamsto more than 25 F (14 C) in
months.
Fish Weirs
I used two fish weirs to monitor downstream
the summer.Maximumsummertemperatures
fish movements,
onein Big SpringsCreeknear
exceeded75 F (23.9 C) in Big SpringsCreek its mouth and one in the Lemhi River about
but only briefly each day. Daily minimum 48 km upstreamfrom its mouth (Figure 1).
temperaturesin summerrangedfrom 45-55 F I attemptedto monitor upstreammovements
(7-13 C) depending
on the nighttimeair tem- of juvenileswith 0.6 X 0.6 m box traps,each
peratures.
with a V openingfacing downstream
but few
fish enteredthesetraps. The two weirs reSubstrate
stricted or blockedupstreammovementsof
Gravel, sand and silt made up the bottom juvenile trout and salmonduring someflow
of Big SpringsCreek and the Lemhi River and operatingconditions.
upstreamfrom the mouth of Big Springs The weir at Big SpringsCreek consisted
initially of inclinedscreentraps. We later inCreek. Larger rock and rubble comprised
stalled
a large rotary drum screenwith a
more of the bottom materials in the Lemhi
bypasstrap to reducemaintenance
and pass
River downstream from the creek. Later in
the large amountsof vegetationdrifting in
my paperI discuss
theimportance
of substrate the stream. The entire flow of the stream
compositionsand structure in relation to passedthroughthe screensand fish moving
movement of fish.
downstreamentered the traps. We usually
426
TRANS. AMER. FISH. SOC., 1971, NO. 3
UPSTREAM
YEARLINGS
MOVEMENTS
Some juvenile trout and salmon moved
upstreamin the studystreams,but I did not
obtain a quantitativemeasureof the magnitude or distanceof such migrations. We
caught few upstreammigrantsin box traps
but I probablyusedinadequatetraps.
I
observed two situations
which
led me
RAINSOW--STEELH
{LR)
G•
to believe that juvenilesof certain species
migratedupstreamlimiteddistances
primarily
during the summermonths. I found large
numbers of juvenile chinook salmon in
screenedirrigation ditches. The salmonprobablyenteredtheditchesby migratingupstream
through the wasteways.At the weir in Big
SpringsCreek I recaptureda few marked
juvenile trout which I had marked and released downstream from the weir.
These fish
probablyreturnedupstreamaroundthe weir
when the creek flowed through the bypass
canal.
DOWNSTREAM
MOVEMENTS
Juvenile trout and salmon entered downFIGURE 4.--Number
of salmon and trout of 1964
year class which emigrated past Lemhi River (LR)
and Big Springs Creek (BSC) weir sites. Fish of
other year classesmigrated in similar seasonalpattern.
operatedthe weir five days each week unless
ice formation or equipmentbreakdownprevented operation. I estimatedthe total numbers of migrantsby multiplyingthe monthly
catchby the ratio of numberof daysin month
over numberof days of weir operation.
The downstream
migranttrap in the Lemhi
River consistedof a louverarray whichguided
fishintoa trap. Thelouversstrainedapproximately10% of the river flow. The percentage
of the downstream
migrantsthat we captured
in the louver trap dependedon species,size
and distribution of the fish across the stream.
streamtraps of the two weirs in all months
of the year, but we caughtmost fish in fall
and spring (Figure 4). Chinooksalmonand
steelheadtrout smolts of appropriate age
migratedto the sea only during the spring.
Mains and Smith (1956) and Raymond
2 observedonly onemajor downstream
migration
of juvenile salmon and trout in the Snake
River and that in the springmonths. Factors
other than instinctual seaward migration
causedthe migration of non-smok steelhead
and salmon and non-anadromous rainbow and
brooktrout duringthe fall, winter and spring.
Chinooksalmonmigratedprimarily as: (1)
fry (lessthan 50 mm fork length) soonafter
emergence,(2) subyearlings(70-120 mm) in
the fall-winter after their first summer, (3)
smolts (80-130 mm) in the spring of their
secondyear, and (4) precociousmales after
the spawningseasonat the end of their second
summer (Figure 4). Migrants decreasedin
abundance
from fry stageto precocious
males
in all year classesthat we enumerated.
Rainbow-steelhead
trout did not migrateas
We releasedmarked fish upstreamfrom the
weir to determinethe percentageof migrants
which passedthe weir site and entered the
louvertrap and therebywe couldestimatethe
total numberof migrants. More detaileddescriptionsof bothweir facilitiesand methods
of operationappear in Bjornn (1966, 1968)
a Personal communication: Howard Raymond, Naand Holubetz (1967).
tional Marine FisheriesService,Seattle,Washington.
BJORNN--TROUT
AND SALMON MOVEMENTS
427
newly-emerged
fry in mid-summerbut primarily as: (1) subyearlings(60-120 mm
total length) in the fall, winter,or springafter
their first summer, (2) yearlings (140-210
ram) in the fall after their secondsummer,
and (3) smolts(160-240 ram) in the spring
of their third year (Figure 4). A few steelheadtrout remainedan additionalyear before
migrating to the sea. In Big SpringsCreek
subyearlings
outnumbered
theotheragegroups
of migrants while at the Lemhi weir site
smoltsmigrating in the spring outnumbered
all otheragegroups(Figure4). In the Lemhi
River few subyearlings
migrateddownstream
pastthe weir site eventhoughrelativelylarge
numbers (up to 25,000) entered the river
from Big SpringsCreekeachfall.
From the fall of 1962 through1969 both
anadromous(steelhead)and non-anadromous
rainbow trout migrated from Big Springs
Creek so that I could not determine
if the
migrationpatterndescribedaboveappliedto
SUBYEARLINGS--BIG
SPRINGS
CREEK
TOTAL
SPRING
h
200
I00
both forms. However, rainbow trout of the
1962
nl-JnnF1
1965
1964
1965
1966
1967
1966
1960 and 1961 year classesenteredthe weir
trap during1962assubyearlings
andyearlings Fret:as 5.--Number of steelhead trout fry released
and thus providedevidencethat non-anadro- into Big SpringsCreek and number of rainbow-steelof each year class emigrating past Big Springs
mous rainbow trout migrated in a manner head
Creek and Lemhi weir site during fall (Augustsimilar to that of steelheadtrout (Figure 5). December),spring (April-July), and total (AugustI believe fewer rainbow than steelhead trout
migratedespeciallyduring yearswhen I releasedlarge numbersof steelheadtrout fry
into the creek.
July) emigration season.
Movement Versus Water Temperature
The largestrainbow-steelhead
subyearlings Juvenile salmon and trout commenced miappearedto migrate first from Big Springs gration from both study streamsin the fall
Creek. I analyzed the 1962-1964 data and as streamtemperaturesdeclined(Figure 6).
found statisticallysignificant (.05 level) dif- Yearling rainbow-steelheadmigratedin largwhilethe largferencesin lengthsof fish migratingthe first estnumbersduringSeptember
half of October versus late November or
est numberof subyearlingsalmonand trout
December as follows: 1962, 90.2 versus84.3 migratedin Octoberand November.
mm total length; 1963, 100.3 versus92.0 ram;
The number of fish migrating normally
1964, 91.0 versus83.5 min.
declined in winter as stream temperatures
Brook trout migrated from Big Springs reachedtheir annual lows. In the spring, as
Creek primarily as: (1) subyearlings(80- temperaturesincreased,larger numbers of
and chinooksal170 mm total length) in the fall, winter, or yearling rainbow-steelhead
spring after their first summer,and (2) as monmigrated,but fewersubyearlingrainbowyearlings (110-270 ram) in the fall, winter, steelheadand brook trout migrated (Figures
smoltscompriseda
or springafter their secondsummer(Figure 4 and 6). Seaward-bound
4). Brooktroutfry emergedduringFebruary- large part of the May peak in numbersof
March but did not migrateas fry. Although yearling(ageII) rainbow-steelhead
troutand
small numbers of brook trout migrated each all of theMarch-Junepeakof chinooksalmon.
year, they migrated in a manner similar to Large decreasesin stream temperatureapthat of other trout.
pearedto causeincreased
numbersof fish to
428
TRANS. AMER. FISH. SOC., 1971, NO. 3
LEMHI
.5 BIGSPRINGS
CREEK
RIVER
[ •1Roinbow-steelheod
4
Roinbow--steelheod
I.yearlingos
_
yeorlings
2
-L,
z
Roinbow-steelheod
•Chino
solm
subyeorlings
subyeorlings
40
o
2O
z
I
o
0
--
-
15
I0
5-
•b•' 6'•'•
'•'
•'
oAUG
............
0
D
F
A
d
MONTHS
Fz½oaE6.--Mean monthly temperaturesof Lemhi River and Big SpringsCreek and mean number of fish
emigrating from each stream each month for 1964-1968 and 1962-1968 periods respectively.
BJORNN--TROUT
AND SALMON MOVEMENTS
429
GAGE BOARD READING
•_•
,,d
3•f•lV•3dl•131
•31V/•
SIN•f•8IH
•
o
•
I•IV3•ISN/•OO
•
•
dO •3gHNN
•
o
430
TRANS. AMER. FISH. SOC., 1971, NO. 3
WATER
INLET
II
SCREENS
I
/
migrateas illustratedon May 10 and September 18, 1965in Big SpringsCreek(Figure7).
Similar increases in movement coincided with
suddendeclinesin temperaturein otheryears
and with otherspecies(Bjornn, 1966).
Although migrations coincidedwith seasonaltemperaturechanges,I couldnot establish any causalrelationshipfrom the data on
temperatureand weir counts. In 1967•58 I
conductedtestsduringthe fall-winter periods
to more clearlydefinethe role of temperature
in the fall migrations.In 1967,I usedtroughs
24 ft (7.5 m) long,2 ft (0.6 m) deepand4 ft
(1.3 m) wide with large rock and gravel substrates to determine
the effect of water tem-
perature and substraterock size on downstream movements.
In 1968 we divided the
troughslengthwiseto providefor replication
in the testsand also added an upstreamtrap
usedin someof the tests (Figure 8). I used
springwater (11-12C) in half the troughs
and Hayden Creek water (O-10C) in the
otherhalf. We placedgravel (1.5 cm diameter) in half the troughsand piles of larger
ROCK PILE
24'
rock (15-45 cm) in the others.
For these tests we used age 0 rainbowsteelhead trout and chinook salmon taken from
WAT E R
FLOW
trapsin the studystreams.After acclimating
the fish 24 hours we removed the barriers to
the traps, beganthe tests,and removedand
countedfish from the traps daily. Most fish
leavingthe troughsdid so in 2-3 days and
during the nighttime. We fed the fish dry
meal once daily.
Chapmanand Bjornn (1969) reportedthe
resultsof the 1967 tests (Table 1) and tentatively concludedthat primarily low temperature
caused
the
downstream
movement
of
rainbow-steelheadtrout and quality of the
winter cover (substrate) modified the movement. We were less sure of the influence of
temperature.
After completingthe 1968 tests (Table.1)
I must revise our conclusionconcerningthe
causal role of temperaturein downstream
movement.In many of the 1968 tests.,fish
Fzcuaz 8.--Diagram of troughsusedin temperaturesubstrate tests during 1967 and 1968.
placedin the warmer spring water left the
troughsat least as readily as fish placedin
the colderwatertroughs.
When I usedbothupstreamand downstream
trapsin the 1968 tests(tests1, 2, 3, 4 and 5,
Table 1), mostfish left the troughsregardless
BJORNN--TROUT
AND SALMON MOVEMENTS
431
TABLE1.--Percentageo] subyearling
rainbow-steelhead
trout and chinooksalmonleavingtest troughswith:
(1) rainbow-steelhead
onlypresent,(2) chinooksalmononlypresent,(3) bothspeciespresent,(4) spring
water versuscolder creek water, and (5) large rock versusgravel substrate
Number Temperature
Year and
test number
of fish/
Date of test
trough
Creek C
Rainbow-steelhead
1967
1
2
100
100
October 16-31
November 1-30
Hayden Creek water
of Hayden
Rock
1-9
04
41
33
October
October
47,40
100,95
4-9
2-8
33,48
52,21
68,52
83,96
25
15
25
25
i
6
3-10
1-7
0-8
0-7
0-5
Means
Rainbow-steelhead
November 8-15
November 22-29
2
13
0
6
7.5
3.0
95,79 100,100
8•,100
51.9
77.7
86.8
57,56
92,79
69.4
8•,96
100,96
i00,100
96.8
87.3
53,5
7,0
0,4
0,16
65,56
100,87
100,71
10.6
Means
8
10
Gravel
5.3
4-10
Means
October 2,5-November
November 15-22
November
29-December
December
13-20
74.0
25
25
Means
6
9
ii
13
Rock
55.5
25
25
4
11-18
18-25
81
67
37.0
Means
September 20-27
September 27-October
Spring water ( 12 C)
trout only
Means
1968
Gravel
96,92
0,12
29,27
24,8
12,8
96,42
73,60
56,72
83.4
15.0
53.9
47.0
12,20
34.5
trout with chinook salmon present
15-15
10-10
0-8
0-8
0,14
0,0
Means
3.5
Means
80,47
40,0
67,64
10,10
41.8
37.8
77,40
22,33
43.8
40.4
22.7
Chinook sahnon only
1967
3
4
December
December
6-13
14-20
100
28
0-5
0-4
45
68
Means
56.5
Means
1968
3a
October 4-11
25
3-9
Means
November 1-8
December 6-13
25
10
1-8
0-9
Chinook salmon with rainbow-steelhead
8
10
November 8-15
November 22-29
15-15
10-10
0-8
0-8
Means
61.0
39.0
100,100
60,100
100 -
100.0
80.0
100.0
90.0
86.7
48,40
100,90
6.0
69.5
21,8
10,10
48,36
90,10
12.3
37.8
46.0
29.2
trout present
20,38
0,0
Means
17.0
76,84
Means
1968
86.5
65
57
80.0
4,0
0,20
Means
27
7
71.5
Means
7
12
91
82
14.5
25.5
73,73
0,0
13,27
80,0
36.5
30.0
100,47
40,60
61.8
45.9
Both upstreamand downstreamtraps used in these tests. Only downstreamtraps operatedin remainder of tests.
of water source (temperature) and usually a
majority enteredthe upstreamtraps. Operating under the hypothesisthat colder temperaturescausefish to move downstreamI
expected fish in creek water to enter the
downstreamtrap if they left the troughsand
fish in springwater to remain in the troughs
or enter upstream traps.
1968 comparemostreadily with the 1967 tests
becauseI usedonly downstream
trapsin both
years. In 1968, as in 1967, fewer salmonand
trout enteredthe downstreamtraps of troughs
with spring water (34.5%) than with creek
water (47.0%), but I found a smaller and
statisticallyinsignificant difference in 1968
(Table 1).
I ran tests with both trout and salmon in
Tests 6, 9, 11 and 13 (rainbow-steelhead
trout) and 7 and 12 (chinook salmon) in the troughsconcurrentlyin 1968 to seeif one
432
TRANS. AMER. FISH. SOC., 1971,NO. 3
RAINBOW SUBYEARLINGS
BIG SPRINGS
RAINBOW
CREEK
40
LEMHI
YEARLINGS
CHINOOK SUBYEARLINGS
RIVER
LEMHI
RIVER
/
ß.3
2.0
0
•--
.6 •
•_40
m
o
--
.0 :•
212
Z
__
o
1966-67
4o.
•
•
•
_
-.5
z
Z y..o
F
-
1967-68
ZO
dUL
•
S
N
d
M
M
•UL S
N
d
MONTHS
M
M
.0
IUL
S
N
d
M
M
FIcuar 9.--Mean monthlystreamheight (flow) of Lemhi River and Big SpringsCreek and percentageof
total fish which migrated past weir sites each month.
speciesmight affect the movementsof the
MovementVersusStream]low
other. Nearly identical percentagesof both
In general,migration of trout and salmon
species
left thetroughsbut largernumbersleft coincided with more or less consistent seasonal
the troughswith springwater (Table 1).
fluctuationsin streamflow(Figure 9). Few
From the inconsistent and variable results
of the 1968 tests,I must concludethat I used fish migratedduringthe summerwhenstreamunsuitabletest apparatusor procedures,or flow reached a minimum. As withdrawals of
that temperaturedid not affect movements water for irrigation declined,flow in the
under the conditions tested.
streamsincreased
in late September
and Octo-
BJORNN--TROUT AND SALMON MOVEMENTS
ber and the fall migrationbeganduringthose
months.Streamflowremainedrelativelycon-
433
STEELHEAD
EMIGRATING
stantduringwinterwhilethenumberof fish
migrating declinedfrom the fall peak. In
spring,
the
migration
of
yearling
trout
apresulting
fromirrigation
withdrawals
priorto
pearedto coincidewith a reducedflow in May
snow-melt
run-off.Subyearling
troutandsalmonmigrated
in thespringalsobutwithless
well defined peaks of movement. Few fish
moved
downstream
in JuneandJulywhen
peakflowsoccurred.
Although some of the major migrations
coincided
with
seasonal
changes
instreamflow,
I do not believe fluctuationsin stream flow
caused
themigrations.
Usually
thefallmigration of trout and salmonbeganin late August
or September
beforestreamflowincreasedand
continued
duringstableflows(Figures7 and
INSECTS
DRIFT
SAMP
ß IN
i
I
INSECTS
I
IN
I
I
STOMACHS
•
i
I
I
OF STEELHEAD
9).
Movement
Versus Food Abundance
JUL
A
S
O
N
D
d
F
M
A
M
d
We collectedsamplesof drifting insectsand
stomachsfrom 10 juvenile steelheadtrout
Fmuas 10.--Estimated
number of rainbow-steelmonthlyduring1966 and 1967at Big Springs head trout which left Big Springs Creek, mean number of insectscollectedin drift nets per 15 minutes,
Creek to determineif the fish migratedbe- and
meannumber of aquatic insectsin trout stomachs
cause of reduced food abundance.
Hartman
collectedduring 1966-1967.
(1963) and Waters (1962) found drift food
lessabundantin winter in the streamsthey
studied.We collecteddrift insectsamplesin
five nets,each30 cm wide and spacedacross
a uniform riffle, at two-hourintervalsduring
a 24-hourperiod. The monthlymeannumber
of driftinginsects(Figure10) wasdetermined
from 60 sampleseachcollectedfor 15 minutes.
Fewer insectsenteredour nets during the
winter months, but the decline in abundance
of insectsoccurredafter trout beganmigrating
from the stream (Figure 10). Many trout
began migratingin Septemberand October
but the number of insectsenteringour nets
did not decline until December.
Trout stomachs contained more insects dur-
of vegetationduring summerand fall, (2)
undercutbanks,and (3) pools.I foundlarge
rubble substrateand the coverit provides
primarily in the Lemhi River downstream
from Big SpringsCreek.
Vegetationbeganto die and drift from the
streamsin September,about the time fish
beganmigrating. Sinceother streamswhere
similardownstream
migrationoccursdid not
containthe matsof vegetation(Chapmanand
Bjornn, 1969, Figure 8), I believethe lossof
vegetationwasa secondary(if any) causeof
the migration.
Chapmanand Bjornn (1969) theorizedthat
ing the winter months (Figure 10), but re- salmon and trout in Idaho. streams need winter
duced digestionrates during winter may coverin whichto hide. Large numbersof fish
left the upperLemhi and Big SpringsCreek
account for the increased number of insects
andthusI believemanyfish foundthehabitat
(Reimers, 1957).
unsuitable.Since few trout which left Big
Springs Creek as subyearlingscontinued
Movement Versus Cover
migratingpastthe LemhiWeir sitetheymust
Coverin Big SpringsCreekand the upper have found suitable habitat. The lower Lemhi
Lemhi River consistsprimarily of: (1) mats River differed from upper portionsof the
434
TRANS. AMER. FISH. SOC., 1971, NO. 3
rock also occupieda variety of stationsin
summer,but we found them primarily under
cut banks in the winter. Without vegetation
125
or rocks in the stream channel fish avoided the
I00
shallowdepthand fastervelocityof the open
riffle
sections in the stream.
Movementl/ersusPopulationDensity
• 5o
28
The number of subyearlingand yearling
rainbow-steelhead
trout which migratedfrom
the studystreamsfluctuatedwith the number
of steelhead
trout fry releasedinto Big Springs
TEST
CONTROL
•+•--[
I
AUG
JAN
1967
1968
JUN
1968
JUL
1968
MAR
1969
AUG
•969
Fmuaz 11.--Number of rainbow-steelheadyearlings
collected from control and test (rock piles added)
sectionsof Big Springs Creek. Rock piles added after
samplingin August 1967.
study streamsprimarily in that it contained
some rubble substrate.
To test the hypothesisthat substratemade
no differenceto migratingfish we conducted:
(1) the trough tests mentionedpreviously
(Table 1), and (2) we placedpiles of large
rock in two 100 ft (30.5 m) long sectionsof
Big Springs Creek during August of 1967.
Two controlsections100 ft (30.5 m) in length
adjacentto the testsectioncontainedno rock.
In both test situations
we wanted to see if
largernumbersof trout and salmonremained
in the troughsor streamsectionswith large
rubble substrate.
Fewer trout and salmon left the troughs
with rock substratethan with gravel substrate
with exceptions
in only a few tests(Table 1).
With all testsaveraged,32% of the rainbowsteelheadtrout left the troughs with rock
comparedwith 68% from the troughswith
Creek(Figure5). The numberof fry released
regulatedthe number of rainbow-steelhead
juvenileswhichrearedand migratedfrom Big
SpringsCreek. Subyearlingsof the 1967-68
year classes
whichmigratedfrom Big Springs
Creekrepresented
a higher proportionof the
fry releasedthan in previousyears perhaps
becausesteelheadhad more completelyreplacedrainbow trout in the stream (Bjornn,
unpublished
data).
The number of fish rearing in Big Springs
Creek (as measuredby the number of migrants) regulatedsomewhatthe time when
fish left the stream(Figure 12). When large
numbersof subyearlingsand yearlings migrated from the stream a higher percentage
left duringthe early Augustto Decemberpart
of the migration season.
In the Lemhi River, a relatively constant
percentage
of rainbow-steelhead
yearlingsand
chinooksalmonsubyearlings
migratedin the
fall regardlessof the total numbermigrating
(Figure 12).
The fraction of the populationof subyearling rainbow-steelhead
rearingin Big Springs
Creekthat migratesmay alsovary with populationdensity.A relativelyconstantnumber
of subyearlingsmigrated from Big Springs
Creek during the spring (April-July) each
year (Figure5). I believeall but a relatively
constant number of subyearlingsleave Big
SpringsCreekeachyearby spring. Goodnight
andBjornn3 (unpublished
data) estimated
the
populationof rainbow-steelhead
subyearlings
in Big SpringsCreekin the springof 1969 at
gravel. Thirty percentof the chinooksalmon
left the troughswith rock comparedwith 6.3%
from troughswith gravelsubstrate.
We founda larger numberof age I+ rainbow-steelheadtrout in the sectionsof Big
SpringsCreekwherewe addedpiles of rock
than in the sectionswithoutrock (Figure 11). 3,000 to 7,000 fish. Their estimate seems
Fish in the sectionswith addedrock occupied reasonablewhen comparedwith the number
a variety of stationsin the stream during
summerbut in winter nearly all fish lived in
or near rock piles. Fish in sectionswithout
a W. Goodnight and T. C. Bjornn, University of
Idaho, Moscow,Idaho.
BJORNN--TROUT
IOO
RAINBOW
AND SALMON MOVEMENTS
SUBYEARLING-BSC
RAINBOW
435
YEARLING--
LR
o
,.•5o
o
o
r=.63
•
0
o
o
o
r=.01
I
I
I0
20
o
I
30
I0 '
15
o
50
o
r=.70
•AINBOW
0
0
YEARLINGI
I
BSC
I
2
r= -.40
CHINOOK
I
3
0
SUBYEARLING--LR
I
I
150
300
I
450
NUMBER OF EMIGRANTS (THOUSANDS)
FmuR•;12.--Correlation(r) betweennumberof emigrantswhichpassedthe Lemhi River (LR) or Big Springs
Creek (BSC) weir sites (1962-1968 year classes) and percentageswhich emigrated in fall.
of yearlingswhichreared and migratedfrom stimulated or released movements in each
the stream. Approximately20-40% of the case ?
subyearlingsmust surviveto yield the 800Watertemperatures,
streamflow,
and photo2,400yearlingswhichmigratedfromthecreek. periodcouldstimulateor releasethe seaward
Assumingabout5,000 subyearlings
remain migration of chinook salmon and steelhead
in Big Springs Creek each year to rear a trout smolts. Peak movements of steelhead
secondsummer, then the total number of sub- trout smolts occurred in May when Lemhi
yearlingsproducedin the streamrangedfrom streamflowdecreased(Figure 9), but I do
11,000 to 30,000 fish. The percentageof the not believethe changingstreamflowscaused
estimatedtotal number producedwhich mi- the downstream
movements.Steelhead
began
gratedassubyearlings
rangedfrom 55 to 83%. migratingfrom the LemhiRiver in late March
and April when streamflowincreasedor reDISCUSSION
mained constant in most years. Steelhead
smoltsmigratedfrom Big SpringsCreekalso
Two types of downstreammovementocin April and May and streamflowremained
curred amongjuvenile trout and salmonin
relativelyconstantthroughoutthe migration
the studystreams: (1) seawardmigrationin period (Figure 9). Chinook salmonsmolts
the spring monthsby age I chinooksalmon migratedfrom the Lemhi River throughout
and age II or III steelheadtrout, and (2) the springmonths(with a peakoccurringin
downstreammovements
primarily in the fall, March some years) and during relatively
winter and spring by pre-smolt and non- stablestreamflows(Figure 9).
anadromous fish. Smolts of the anadromous
The smolt migrationo.f both salmonand
speciesobviouslysoughtthe ocean in their trout in the study streams coincided with
downstream
movements
but what did the pre- increasingstreamtemperaturesin the spring
smolts or non-anadromous fish seek? What
(Figure 6), but the increasingtemperatures
436
seemed
TRANS. AMER. FISH. SOC., 1971, NO.
coincidental
since
steelhead
trout
rearedin a spring-fedpondon a tributaryof
the Lemhi River migratedfrom the relatively
constanttemperaturepondat the normaltime
in April or May.40sterdahl (1969') observed
that timing of seawardmigrationof Atlantic
salmon (Salmo salar) frequently, but not
always,coincidedwith an increasein stream
temperatureandhe concluded
temperaturedid
not causethe migration. Bjornn, Craddock,
and Corley (1968) found sockeyesalmon
(Oncorhynchus
nerka) left RedfishLake regardlessof temperatureat the lake outlet.
I could not establisha causalrelationship
betweenstreamtemperatureand the seaward
migrationof salmonand trout smoltswith
the data I collected. Eales (1965), however,
seasonand declined as it ended. Wagner,
Conte, and Fessler (1969) suggestedthat
marineosmoregulation
developed
independent
of the parr-smolt transformation
5 in coho
salmon and developmentof the euryhaline
state did not resuk in an immediatechange
in migrationdisposition.
The role of photoperiodand temperature
as stimulators, or releasers, in the seaward
migrationof salmonand trout smoltsis unclear and should be better defined.
Growth
alsoplaysa role sincesomefishdo not migrate
until they reach a thresholdsize and pass
throughone or two photoperiod-temperature
cyclesbeforemigratingto the sea (steelhead
trout for example).
Sincepre-smoltsand non-anadromous
fish
migratedprimarilyduringthe periodSeptember-May eachyear, I theorizedthat the fish
found someaspectof the environmentunsuitableduringthat period. ChapmanandBjornn
(1969) proposedthat fish in most Idaho
streamsrequired winter cover and that low
watertemperatures
triggeredthe winterhiding
behaviorobservedby them (Hartman, 1965;
found that increasedthyroid activity in steelheadtroutsmoltsdepended
on bothincreasing
temperatureand photoperiod.Johnstonand
Eales(1968) foundthat deposition
of guanine
and hypoxanthine(silvering)in the skin and
scalesof Atlantic salmon also dependedon
temperaturebut was not affectedappreciably by len•hening photoperiod. Canadian
workers (FisheriesResearchBoard of Canada, Everest, 1969).
1966) reportedthat cohosalmon(Oncorhyn- In my experiments
with substrate
and temchus kisutch) held in 8.5 C water underwent perature, I inducedmore fish to remain in
changes
in bothguaninedeposition
and coef- test troughsor test sectionsof Big Springs
ficient of condition with change in photo- Creek by providingmy conceptof a more
period. For fish held in 2.5C water the suitable substrate in terms of winter cover
coefficientof conditionchangedlittle, if any, (Table2 andFigure11). I believetheamount
under any photoperiodregime tested and of suitablewinter cover in a streamplays.a
guaninelevel increasedslightlyby the end major role in regulatingthe numberof fish
that overwinter in streams with winter temof the experiment.
Water temperaturesin the Lemhi River peraturesbelow 4-5 C. Hunt (1969) found
increasedduring the spring and thus would reduced loss of brook trout in a Wisconsin
not inhibit the parr-smolt transformation in streamdue to mortality and migration after
the manner listed above. At Redfish Lake, habitat improvement.He believedthe imhowever,we (Bjornn et al., 1968) observed provementin "space-refuge"
factors (protecsockeyesalmonsmoltsleavingan ice-covered tive cover, depth, pool area) accountedfor
lake in which water temperatureshad not the larger overwinterpopulations.
exceeded 4 C for 34 months.
The role, if any, of temperaturein the fallBaggerman(1960) concludedthat daily winter migrationsremainedunclear,perhaps
length of photoperiodcontrolledtiming of becauseof inadequatetesttroughs.A slightly
maturation of the mechanism for marine
largernumber(notstatistically
significant)of
salmon
and
trout
left
the
troughs
with gravel
osmoregulation
and probably migration-dissubstrate
and
cold
water
compared
to gravel
positionof juvenilesalmon.Shefoundthyroid
activity increasedprior to the migration
Unpublisheddata, Idaho Fish and Game Department, Salmon,Idaho.
5 1 considerthe parr-smolttransformationto include
both the changes in appearance (silveriness and
coefficient of condition) and behavior (migration
disposition).
BJORNN--TROUT
AND SALMON MOVEMENTS
TABnE2.--Percentageo] ]ish leavingtroughsduring
tests conductedin 1967 and 1968 (Table 1), all
tests combined
Substrate
Steelhead
Rock
Gravel
26.7
41.3
76.2
62.9
29.6
30.3
66.4
62.8
trout
Creek water (0-10 C)
Spring water (11-12 C)
Chinook salmon
Creek water
Spring water
substrateand warmer water (Table 2).
in the operationsof facilitiesand collectionof
data. Dr. D. W. Chapmangave helpful suggestionsand assistance
as the testsprogressed
and criticallyreviewedthe manuscript.James
C. Simpsonand JamesF. Keating,Idaho Fish
and GameDepartment,providedthe financial
and administrativesupportrequiredfor long
range studiesof this type.
LITERATURE
In
437
CITED
BAGGERMA1%
B. 1960. Salinity preference, thyroid
activity and seawardmigration of four speciesof
Pacific salmon (Oncorhynchus). J. Fish Res.
thetroughswithrocksubstrate
equalnumbers
Bd. Canada 17(3): 295-322.
of salmonremainedin thetwowatertempera- B$ORI•I•, T. C. 1966. Steelhead trout production
studies,Lemhi Big Springs Creekß Annual Comturesand fewertrout remainedin the trough
pletion Report, Project F-49-R-4, Idaho Fish and
with warmerspringwater.
Game Dept., Processedreport, 183 pp.
Temperatureappearedto causelittle if any
1968. Steelhead trout production studies,
Le'mhi
BigSprings
Creek.Annual
Completion
changein the behaviorof fish movingdownReport, Project F-49-R-5, Idaho Fish and Game
stream, but Chapmanand Bjornn (1969)
Dept., Processedreport, 21 pp.
presented
someconvincingevidencethat lower
, A•D J. MAnnET. 1964. Movementsof planted
water temperaturestriggered winter hiding
and wild trout in an Idaho river systemßTransß
Amer. FishßSoc. 93(1): 70-76.
behaviorof fish. A fish inducedto hide by
, D. R. CRADDOCK,
A•D D. R. CORnE¾.1968ß
lowwatertemperatures
maymovedownstream
Migration and survival of Redfish Lake, Idaho
if unable. to locate suitable cover and thus
sockeyesalmon (Oncorhynchusnerka). Trans.
Amer. Fish. Soc. 97(4): 360-373.
temperaturesmay trigger downstreammoveCHAPMAN,D. W., AND T. C. Bjoal•l•. 1969. Disment indirectly.
tribution of salmonids in streams with special
! found no evidence that food or stream
flow induced the movements observed in the
reference to food and feedingß H. R. MacMillan
Lecturesin Fisheries,Symposiumon salmonand
trout in streams. University of British Columbia.
Pp. 153-176.
studystreams.Smallfreshetsduringthe usual
migrationperiod occasionally
coincidedwith EAZES,J. G. 1965. Factors influencing seasonal
changesin thyroid activity in juvenile steelhead
temporaryincreases
in thenumberof migrants
trout, Salmo gairdnerl. Canadian J. Zool. 43:
but suchoccurrences
only modifiedthe basic
719-729.
migrationpattern.
EVEREST,
F.H. 1969. Habitat selectionand spacial
interaction of juvenile chinook salmon and steelPopulationdensityalso appearedto only
head trout in two Idaho streams. Doctoral dismodify the basic migration patternsrather
sertation, University of Idahoß 77 pp. (Un-
than cause the movement. The number of
salmon and rainbow-steelhead
trout that
FISHERIESRESEARCHBOARDOF CANADA. 1966.
migratedand the time of migrationcorrelated
with populationdensityin someinstances,
but
somefish moveddownstreamat all popula-
view 1964. Annual Report, 103 pp.
HARTMAX,G.F. 1963. Observationson behavior of
juvenile brown trout in a streamaquarium during
winter and springß J. Fish. Res. Bd. Canada 20:
tion densities encountered.
Because some fish
migrated regardlessof populationdensity,
inheritedtraitsor photoperiod
couldalsoplay
a role in the movement.
Lack of movement
published.)
Re-
769-787ß
ß 1965. The role of behavior in the ecology
and interaction of underyearling coho salmon
(Oncorhynchus kisutch) and steelhead trout
(Salmo gairdneri). J. Fish. Res. Bd. Canada
22: 1035-1081.
of brook trout fry leadsme to recognizethe HOnt•BETZ,
T. B. 1967. Evaluation of louver guidpossibilitythat no fish wouldmigrateif popance facility used to sample salmon and trout
emigrantsßAnnual Progress Report, Project Fulationsdid not exceedthe winter capacity
49-R-4, Idaho Fish and Game Deptß 45 pp.
of the streams,perhapsin terms of winter HUI•T,
ROi3ERTL. 1969. Effects of habitat alteration
cover.
ACKNOWLEDGMENTS
I am gratefulfor the cooperationof Melvin
Reingold,DeanMyersand DelbertLedington
on production,standingcrops,and yield of brook
trout in LawrenceCreek, WisconsinßH. R. MacMillan Lectures in Fisheries, Symposiumon
salmon and trout in streamsß University of
British Columbiaß Pp. 281-312.
438
TRANS. AMER. FISH. SOC., 1971,NO. 3
JOHNSTON,
C. E., aNI• J. G. Eanzs. 1968. Influence
of temperature and photoperiodon guanine and
hypoxanthine levels in skin and scalesof Atlantic
salmon (Salmo salar) during parr-smolt transformation. J. Fish. Res. Bd. Canada 25(9):
1901-1909.
MAINS, J. E., AND J. M. SMITH. 1956. Determination of the normal streamdistribution,size,time
and currentpreferencesof downstreammigrating
salmon and steelhead trout in the Columbia and
Snake Rivers. Washington Department Fish.
Prog. Rept., Corps of Eng. Fish. Eng. Res.
Program. Pp. 14-25.
OSTERDAHL,
Laas. 1969. The smolt run of a small
Swedish
river.
H.
R.
MacMillan
Lectures
in
Fisheries, Symposium on salmon and trout in
streams. University of British Columbia, Pp.
205-215.
REI•ERS, N.
1957. Some aspects of the relation
between stream foods and trout survival.
fornia Fish and Game 43: 43-69.
Cali-
WacNza, H. H., F. P. CONTE,AND J. L. FESSLEI1.
1969. Developmentof osmoticand ionic regulation in two races of chinook salmon Oncorhynchus tshawytscha. Comp. Blochem. Physiol. 29:
325-341.
WATERS,
T.F. 1962. Diurnal periodicity in the drift
of stream invertebrates. Ecology 43: 316-320.