I
'
~~~. . . £ARCH REPORTS
HfPORTS
RESEARCH
the
of the
SH commiSSIOn Of ORfGOn
FISH COfflfflISSIOfl OF ORE6Ofl
VOLUME 44
VOLUME
NUMBER
NUMBER 22
JUNE 1973
1973
JUNE
Robert T. Gunsolus, Editor
This is the second Research Report of Volume 4 of a new publication replacing the Research Briefs and the Contribution series.
This new series follows Volume 13, Number 1 of the Research
Briefs and Contribution Number 29. Frequency of publication
of this series will depend on the number and size of acceptable
manuscripts submitted to the editor.
These reports are intended to inform fisheries scientists, the
fishing industry, sportsmen, and the general public of noteworthy research and management activities of the Fish Commission staff and other contributors working with Pacific Coast
fisheries resources. Research Reports are free and may be ob-
tained on request to the editor.
Address correspondence to:
Fish Commisson of Oregon
Division of Management &
Clackamas, Oregon 9701 5
RESEARCH RfPORTS
RfSfRRCH
of
the
of the
fiSH
commiSSIOn Of
OHfGOn
FISH COIlllflISSIOfl
OF OREGOfl
FISH
COMMISSION OF
OF OREGON
OREGON
FISH COMMISSION
307 State Office Building
Building
.
#
Portland, Oregon
97201
VOLUME 44
VOLUME
NUMBER
NUMBER 22
JUNE
1973
JUNE 1973
CONTENTS
CONTENTS
THE
THE LENGTH
LENGTH OF
OF RESIDENCE
RESIDENCE OF
OF JUVENILE
JUVENILE FALL
FALL CHINOOK
CHINOOK SALMON
SALMON
IN SIXES
SIXES RIVER,
RIVER, OREGON
OREGON
Page
ABSTRACT----------------------------------------------------------------------------------------------------------ABSTRACT
----------------------- ------------------------------------ ------------ ------------ ------------------------
3
INTRODUCTION------------------------------------------------------------------------------------------------INTRODUCTION
---------- ------------ -------- ----- -------- ------- -------------------------------- -- ------------DESCRIPTION
AREA___________
___ ____ ____ __ __ _______________________ _______________
DESCRIPTIONOF
OF THE
THE STUDY
STUDY AREA
-----------------------------------------------------------------
3
55
METHODS------------------------------------------------------------------------------------------------------------METHODS
--------------------------- ------ ------------------------------ ------------ ---------------------------------- 8
Sampling
Adult Population
Population ----------------------------------------------------------------____________ __ _____ __ _______________ _________________ __ _________ _ 8
Samplingof
of the
the Adult
Sampling
of
the
Juvenile
Population
________ ___ _________ __ __ ____ ______________ ___________ _ 8
Sampling of the Juvenile Population _______
------------------------------------------------------------Fresh-Water Studies
Studies ----------------------------------------------------------------------------------------------------------------- ------ ---------------------------------- 9
EstuarineStudies
----------------------------------------------------------------------------------Estuarine Studies ---------------------- ---- ------------------ ----- ----- ------------------ ---------- 9
0
BehaviorStudies
-------------------------------------------------------------------------------------------Behavior
Studies
-- --- ----------- ------------ -- ----- ----------------- ------- -------------------- ------------ 10
ScaleStudies
------------------------------------------------------------------------------------------------Scale
Studies
---- ----- --- --------- --- ---- ---- --- ---- --- --- ----- ------ ----------------------- ---- ------------- 10
RESULTS
----- --------- ---------------- ---------------------- -------- -- ------- ------------- --- ---------------- ----- ----- 110
0
RESULTS--------------------------------------------------------------------------------------------------------------Location
andTime
Timeof of
Deposition_______
____ ______ ___ _____ ________ ____________________________ 11 00
Location and
EggEgg
Deposition
------------------------------------------------------------TimingofofEmergence
Timing
Emergence --------------------------------------------------------------------------------------------------------------------------------- ------------------------------- ----- 12
Downstream Migration and
and Behavior
Behavior of
of Newly
NewlyEmerged
Emerged Fry
Fry_______________
___ _______ _ 14
Downstream
-------------------------EmergenceBehavior
----------------------------------------------------------------------------Emergence
Behavior
---- ------------------- ------------------------------------------------------ 14
Development
Residence
-------------------------------------------------------Stream
Residence
-------------------------------------------------------- 16
DevelopmentofofStream
Influence
------------------------------------------------------------------------InfluenceofofMoonlight
Moonlight
----------------- ----------------------- ------------------------------- -- 17
Long-Term
Tributary
Residence
_________ _____ ____ __ __ _--- ---- ------- ----- -------------------- --- ---- 11 88
Long-Term Tributary
Residence
--------------------------------------------------------------------the
Main
___ __ ___ ____ _____________________________ ___ ______ _____ __ ___ ____ __ 18
18
Residence ininthe
Residence
Main
RiverRiver_______
------------------------------------------------------------------------Residencein
Estuary
--------------------------------------------------------------------------------Estuary
.. --- -- -- ----------- ---- -- --------- ---------------- ------------------------------ 19
Residence inthethe
Change in
in Abundance----------------------------------------------------------------------------____ __ __ ___ ____ .------------- --------------------------- ---- ------ ------ ----· 20
Change
Growthin
Juveniles
----------------------------------------------------------------------------Growth in Juveniles ------------------------- -·-- ------·--- ·-- -------- -------- ----- --- --------- · 21
Terminal
Population
Terminal Population --------------------------------------------------------------------------------------------------- -----············--------------------------- -- ------ -- 23
YearlingMigrants
Yearling Migrants ----------------------------------------------------------------------------------------·······················------------- --- ·············- ---- ------------------- --- --------- - 24
ScaleStudies
Scale Studies --------------------------------------------------------------------------------------------------- --------- ----- --------------------- ---- -- --- ---·-····--·-··--·--·-------------------- ----· ·-·· 24
Types
Life Histories
Histories --------------------------------------------------------------------------________ ____________ ___ ___ ______ ___ __ __ ___ _____ __ _____________ ____ ____ _____ 24
24
Types of
of Life
Scale
Characteristics of
of Life History
Scale Characteristics
His toryTypes
Types ----------------------------------------------- ----------------------- ------------- 26
26
Life History
HistoryofofSuccessful
SuccessfulSpawners
Spawners ------------------------------------------------------ --------- ----- ------------- -------- ----------- ··· 31
DISCUSSION--------------------------------------------------------------------------------------------------------DISCUSSION -- --- -------------- ------ -------------------- -- -- --- -- -- -- ----- --- -- ------------------------- ------------ 32
32
Initial Downstream
Downstream Dispersal
Dispersal of Fry
Fry ___
_______ ______ ______ ______ ____ _____ _______ ______ __ __ ___ ____
------------------------------------------------------------Influence
Temperature on
Residence inin the
Main River
River_-----------------------_________ __ __________ __
Influence of Temperature
on Residence
the Main
Population Density
the Estuary
Estuary -------------------_______ __________ ___
Population
Density Versus
VersusGrowth
Growthof
of Juveniles
Juveniles in
in the
Importance
Importance of Fresh-Water
Fresh-Water and
and Estuarine
Estuarine Rearing
Rearing ----------------------------------------- ---- -- ------------------- ------- -LITERATURECITED
LITERATURE CITED ------------------------------------------------------------------------------------------------ ---- --- ----- -------------------------- ---·-······ ·····------- ----------------------·-····
32
32
35
35
36
38
40
40
ACKNOWLEDGMENTS--------------------------------------------------------------------------------------ACKNOWLEDGMENTS --- ------- ------------------------- --- ---------- -- -- --------- ---------- -- ----- ---- ---- 43
[ 2]
(2]
THE
LENGTH OF
RESIDENCE OF
THE LENGTH
OF RESIDENCE
OF JUVENILE
JUVENILEFALL
FALLCHINOOK
CHINOOK SALMON
IN SIXES
SIXES RIVER,
RIVER, OREGON
OREGON°
Paul E.
E. Reimers7
Paul
ReimersC
ABSTRACT
This
history information
information about
about juvenile
juvenile fall
fall chinook
chinook salmon,
salmon, Oncorhjjnchus
Oncorhynchus
This study
study was
was designed
designedtoto provide
provide life
life history
tshawytscha (Walbauml,
(Wolbouml, irs
in Sixes
Sixes River,
Oregon, by
11 documenting
documenting the
length of
of residence
residence
River, aa small
small coastal
coastalnver
river of
of Oregon,
by 1)
the length
the juveniles
juveniles throughout
exploring several
several factor
s possibly
length ofofresidence,
residence, and
and
of the
throughout the
the river,
river, 21
2) exploring
factors
possibly influencing
influencing their
their length
31 assessing
assessing the
importance of fresh-water
fresh-water and
and estuarine
estuarine rearing
areas for
for producing
producing returning
returning spawners
spawners.
3)
the relative
relative importance
rearing areas
The juveniles
juveniles were
emergence inin the
spawning streams
r entry
into the
the ocean.
ocean. Most
Most
The
were followed
followed from
from their
their emergence
the spawning
streamstoto thei
their
entry into
information
length of
of residence
residence of the
the juveniles
juveniles was
was obtained
obtained by
by seining
seining and
and trapping
trapping at
at various
various times
times and
and
information on
on the length
locations in
the river.
river.
locations
in the
Spawning
Creek. Most
fish spawned
spawned from
from November
November
Spawningoccurred
occurredmostly
mostlyininthe
thetributary
tributary streams,
streams,Primarily
primarily in
in Dry CreeL
Most fish
January. Fry
emerged from
May. Newly
Newly emerged
emerged fry
moved downstream
downstream from
to January.
Fry emerged
fromthe
the grovel
gravel from
from March
March to
to May
fry moved
from the
spawning
numbers at
experimental studies of juvenile behavior, this
movement
Based on
on experimental
this movement
spawningareas
areasinin Iorge
large numbers
at night. Based
apparently resulted
fry during
during darkness.
darkness. Downstream
apparently
resultedfrom
fromemergence
emergenceatatnight
nightand
andlock
lackofofvisual
visualorientation
orientationofof the
the fry
movement
day light or moonlight
!. This
This initial movement
movementwas
wasreduced
reducedduring
duringincreased
increasedlight
lightlevels
levels ((daylight
moonlighti.
movement of fry is
thought to assure
assure rapid
e rriver
iver without
extens ive energy
thought
rapid dispersal
dispersalofof juveniles
juvenilesthroughout
throughoutththe
without extensive
energy costs
costsofof dispersal
dispersalby
by aa
mechanism.
social mechanism.
Many juveniles
juveniles remained
remained in
fresh water
water until
untilearly
earlysummer
su mmer. Most
entered the
the estuary,
estuary, possibly
possibly because
because
Many
in fresh
Most then entered
high temperature
temperature in
the main
main river.
river. A
small number
numberofoffish
fishcontinued
continuedtotoreside
reside ininthe
thecool
cool spawning
spawning tributaries.
tributarie s,
of high
in the
A small
Detailed studies
1969 showed
showed that
juveniles began
ring the estuary
estuary 1n
Iorge increases in the
Detailed
studies in
in 1969
that juveniles
beganente
entering
in spring, but large
population did not
not occur
occur until
until June.
June. During
Duringthe
the
periodofof
increasingobundance,
abundance,many
manyjuveniles
juvenileswere
werealso
alsocaptured
captured inin
population
period
increasing
the ocean
ocean surf.
surf. The
The population
population level
level in
the estuary
estuary peaked
peaked at
about 145,000
145,000 fish
and August
August and
and
in the
at about
fish during
during July
July and
then
to aa low
then declined
declined to
low level
level in
in autumn.
autumn. The
The rate
rote of
ofgrowth
growthofofthe
thejuveniles
juvenileswas
wasreduced
reduced for
for 33 months
months during
during the
the
period
period of
of high
high populotion
population abundance.
abundance. Population
Population density
density isis hypothesized
hypothesizedasasaa maj
major
or cau'e
causeof
of the
the depressed
depressed rate
rateof
of
growth of
of the
the juveniles.
juveniles. After the
the population
population declined
declined in late
late summer,
su mmer, growth
growth of
ofjuveniles
juveniles again
againimproved.
improved. Following
the autumn
autumn freshets,
freshets, mOst
most fall chinook
chinook salmon
salmon remaining
remainin g in
in the
theestuary
estuary and
andthose
th o'e ininthe
thecool
coolspawning
spawningstreams
streams
ing the
entered the
few fish
fish from
from the
the tributary
tributary populations
populo! ions remained
remained in
m ientered
the ocean.
ocean. AA few
in fresh
fresh water
water through
through the
the winter
winter and
and migrated
the ocean
ocean as
as yearlings
yearlings the
the following
following spring.
spring.
grated to the
Based
length of
res idence of
Basedon
onvariation
variationinin the
the length
of residence
of juveniles
juveniles inin fresh
fresh water
water and
and the
the estuary,
estuary,five
five types
typesofof life
life
histories
Scale patterns
patternsfrom
from these
these types
typeswere
were distinguished
distinguishedand
andreturning
returning spawners
spawnersfrom
from the
the 1965
1965
histories were
were defined. Scale
brood
the various
various types.
types. The
The type-3
type-3 fish,
fish, those
those remaining
remaining in
fresh water
water until
until early
early summer
summer and
and then
then
in fresh
brood sorted
sorted into the
remaining
period of
of improved
improved growth
growth in
in the
the estuary,
estuary, repre
se nted about
the returning
returning spawners.
spawners. Based
Based
represented
about90%
90% of the
remaining for
for a period
on
the return
return of
of these
these type-3
type-3 fish,
fish, fresh-water
fresh-water and
and estuarine
estuarine rearing
rearing were
were concluded
concluded to
be about
about equally
equally imporimporon the
to be
tant to
to fall
fallchinook
chinooksalmon
salmonininSixes
Sixes River.
River.
Introduction
The
chinook salmon,
salmon, OncorhynchThe fall chinook
us tshawytscha
tshawytscha (Walbaum),
an imimus
(Walbaum), isis an
portant component
component of Oregon's
Oregon's comcomportant
mercial
and sport
sport fisheries.
fisheries . Significant
Significant
mercial and
recently made
made in
uncontributions were recently
in un-
derstanding historical changes in the
abundance of
chinook salmon
salmon in the
the
abundance
of fall chinook
Columbia
hatchery
Columbia River
River and
and the
the.fate
fate of hatchery
fish in
in the
the ocean
ocean (Van
(Van Hyning,
Hyning, 1973;
1973;
fish
Wahle, and
and
Cleaver, 1969;
1 969; Worlund,
Worlund, Wahle,
Zimmer, 1969).
despite general
general inin1 969), But despite
terest in
in maintaining
maintaining or
or increasing
increasing the
the
terest
abundance
relatively little
abundanceofofthis
this fish,
fish, relatively
is
known of
its juvenile
juvenile life
life history.
history.
is known
of its
study was
was designed
designed to
to provide
provide
This
This study
chinook
additional
additional information about fall chinook
salmon by
documenting the
length of
salmon
by 1)
1) documenting
the length
residence of
juveniles in
in aa small
small coastal
coastal
residence
of juveniles
river, 2)
2) exploring
exploring several
several factors
factors posposriver,
sibly
influencing their
their length
length of resiresisibly influencing
<D This
with
the
, NOAA,
Morine
This study
study was
wasconducted
conductedinincooperation
cooperation
with
theDepartment
Departmentofof Commerce
Commerce,
NOAA, Notional
National Marine
Fisheries
Service,
Service, under
under Public
Public Law
Low 89-304,
B9-304, Projects
Projects AFc-26,
AFC-26, AFC-39,
AFC- 39, and
and AFC-54
AFC-54.
fulfillment of
for the
From
Oregon State
partial fulfillment
of the
the requirements
requirements for
the degree
degree of
of
From aa thesis
thesis submitted
submitted to
to Oregon
State University
University in
in partial
Doctor
Philosophy, June
June 1971.
1971.
Doctor of Philosophy,
<!)
® Aquatic
Aquatic Biologist,
Biologist, Management
Management and
andResearch
Research Division,
Division , Fish
Fi sh Commission
Commission of Oregon,
Oregon, Port
Port Orford,
Orford, Oregon
Oregon 97465.
97465.
[(3]
31
dence,
assessing the
was absorbed.
absorbed. Later data
data suggested
suggested
dence, and
and 3)
3) assessing
the relative
relative imim- yolk was
fresh-water and
and estuarine
estuarine further survival advantage in rearing
portance
portance of
of fresh-water
for producing
producing hatchery
hatchery fall
chinook salmon
salmon to aa large
large
rearing
rearing areas
areasofof the
the river
river for
fall chinook
returning spawners.
1957; Junge
Junge and
and
returning
spawners.
size
(Cope and Slater,
Slater, 1957;
size (Cope
Phinney, 1963).
Chinook salmon
salmon are
are divided
divided into sevChinook
sev- Phinney,
1963) .
Reports.
popuera!
seasonal races,
eral seasonal
races,based
basedon
onthe
the time
time of
Reports.ofof research
research on
on natural
natural popufresh-water
adults on
chinook salmon
s.almon are
are scarce.
scarce.
fresh-water entry
entry of
of the
the adults
on their lations
lations of chinook
and These
These studies
spawning migration. Spring,
Spring, summer,
summer, and
studies faced
facedtwo
two main
main difficulties
difficulties
fall races
the Columbia
Columbia that must
must be
be considered
considered when
when attemptraces are
are present
present in
in the
River (U
.S. Army
Corps of
of Engineers,
Engineers, ing
(U.S.
Army Corps
ing to decipher
decipher the
the history
history of
of our
our knowlknowlIn the
the Sacramento
Sacramento River
River aa winter
edge about
length of
of residence
residence of
of
1969)
1969).. in
winter edge
about the
the length
is also
also present
present (Slater,
In the juveniles: 1)
1) most
most studies
studies were
were done
done
race
race is
(Slater, 1963).
1963). In
chinook salmon
salmon mimi- on
large rivers
rivers where
where sampling
sampling was
large
large rivers,
rivers, adult
adult chinook
on large
was difdifthe ficult, and
and 2)
2) more
more than
than one
one race
race was
was
grate
grate during
during nearly
nearly every
every month
month of
of the
short coastal
coastal streams,
streams, such
such as
as usually
usually involved.
involved. Distinguishing
Distinguishing among
among
year. In
year.
In short
the
study, only
the fall race
race races
races was
simthe one
one in
in this study,
only the
was impossible
impossible because
because of
of the simis
this race
race enter fresh
fresh ilar appearance
appearance of
the juveniles.
juveniles.
is present.
present. Adults
Adults of this
of the
water
from August
August to
to December
December and
and
Confusion occurs in the literature
water from
spawn
September to March,
March, dede- where
history
spawn from
from September
where interpretations
interpretationsof
of the
the life history
location of the
the stream
stream of chinook
chinook salmon
salmon were
pending
pending on
on the
the location
were made
made from
from adult
(Mason,
scales
scaleswithout
without examining
examining the
the length
length of
(Mason, 1965).
the juvenile
juvenile life history
history residence
juveniles. For
For example,
example,
Variability
Variability in
in the
residence of
of the juveniles.
of chinook
chinook salmon
salmon appears
appears to be common. analysis
scales from
Taku
analysisof
of adult
adult scales
from the Taku
The juvenile
The
juvenile life
life histories
histories of
the two
two River
suggested that
the fish
moved
of the
fish moved
River suggested
that the
are downstream
(Alaska Department
Department
primary races,
races, the
primary
the spring
spring and
and fall, are
downstream as
as fry
fry (Alaska
generally
be distinct.
distinct. The
The of Fisheries,
Fisheries, 1953),
1953), but
but Meehan
Meehan and
and
generallythought
thought toto be
various
populations have
have been
been managed
managed Siniff
Sin iff (1962)
( 1962)trapped
trappedthe
thesame
same populapopulavarious populations
that most
most juveniles
juveniles rereaccordingly.
sal- tion
tion and
and found
found that
accordingly. Juvenile
Juvenile spring chinook salexpected to
to remain
remain in fresh mained
mained in
fresh water for aa year
year or longlongmon
are expected
mon are
in fresh
water for aa year
year before
before migrating
migrating to the
the er.
Mattson (1963)
( 1963) showed
showed from
from adult
adult
er. Mattson
scales that
that most
ocean
second spring. JuvenJuven- scales
most spring
spring chinook
chinook salmon
s.almon
ocean during
during their second
ile
ile fall
fall chinook
chinook salmon
salmon are
are expected
expected to in the
the Willamette
Willamette River
River returned
returned from
from
fresh water for aa short
short period
period juveniles
juveniles residing
residing aa year
fresh water,
water,
remain in
remain
in fresh
year in
in fresh
showed that
that the
of time,
time, usually
usually around
around 3 months
months after but sampling
sampling showed
the majority
majority
ab$orption. The
these poppop- of the
the juveniles
juveniles went
went downstream
downstream as
as fry
yolk absorption.
The origin of these
have been
been inin- in the first spring (Mattson, 1962).
ular concepts
concepts seems
seems to
ular
to have
fluenced by success
orfailure
failure of
of hatchery Based
on adult
adult scale
success or
Based on
scale reading
reading by
by Rich
Rich
1968) and
and interpreinterpre- (1925), most juvenile fall chinook
operations
operations (Wallis,
(Wallis, 1968)
salmon in the
tation
the Columbia
tat ion of adult
adult scales
scales (Rich,
(Rich, 1925).
1925) .
Columbia River
River were
were
Becauseof
of the
the advantage
Because
advantage of increased
increased thought
thought to
to move
move quickly
quickly to
tothe
theocean.
ocean.
growth in
in the
theocean
ocean as
as opposed
opposed to fresh
fresh However, extensive fresh
-water resifresh-water
of juveniles
in tributaries
water, as
water,
as early
early as
as 1900
re- dence
dence of
juveniles in
tributaries of the
the
1 900 there
there were
were rerelease hatchery
River was
was later
later discoverdiscovercommendations
commendations to
to release
hatchery fish lower Columbia River
and Loeffel,
The ed
ed (Reimers
(Reimers and
Loeffel, 1967).
1967).
as
as soon
soon as
aspossible
possible(Rutter,
(Rutter, 1903)
1903).. The
was primarly
primarly aa field
field study
practice of planting recently
hatched
This research
research was
practice
recently hatched
juvenileswere
were traced
traced from
from the
as Rich where
where juveniles
the
alevins was
was widespread,
widespread, but
alevins
but as
( 1920) pointed
pointed out, itit may
may have
have led
led to
to time they
they emerged
emerged from
from the
thespawning
spawning
(1920)
Following that early
early pracprac- gravel
gravel until they
they entered
entered the
the ocean.
ocean. The
The
low survival.
survival. Following
low
tice, hatcheries
hatcheries held
the length of residence
residence and
and downstream
downstream
tice,
held juveniles
juveniles until
until the
[ 4]
(4]
movement of
of the luveniles
movement
juveniles were
were associatassociatecological data
data and
and examined
examined in
ed
ed with
with ecological
behavioral
experiments. After
explorabehavioral experiments.
After explorat~ry
the first
firstfew
fewyears,
years, Sixes
Sixes
tory work during the
R1ver
was chosen
chosen as
primary stream
stream
River was
as the primary
for study
study because:
because: 1)
1 ) it had
had aa relatively
relatively
large natural population of fall
fall chinook, 2l
2) the
river was
was small
small and
and acacnook,
the river
study, and
and 3)
3) considerable
cessible to
cessible
to study,
length
variation
variation appeared
appearedtotoexist
exist in
in the
the length
of
residence of
the juveniles,
juveniles, with sevsevof residence
of the
eral rearing areas
being utilized.
utilized. Because
Because
eral
areas being
the
scope of
study involved
involved work
work
the scope
of this study
from the
the spawning
spawning areas
areas to the
the estuary,
estuary,
all aspects
aspects could
could not
not be
be studied
studied simultansimultaneously.
research were
eously. Various
Various parts
parts of the research
were
conducted
1970. Major
conductedfrom
from 1964
1964 to 1970.
emphasis
years of
emphasis was
was placed
placedon
on the
the later years
study,
1969 to
to 1970,
1970, where
where
study, primarily
primarily 1969
more complete
were available
available for aa
more
complete data
data were
particular brood.
brood. CD
Description
Study Area
Description of
of the
the Study
Area
Sixes
coast of
Sixes River
River isis located
located on
on the
the coast
Oregon
(Figure
Oregon 88 km
km north
north of
of Port
Port Orford
Orford (Figure
1).
Total drainage
drainage of
the river
river is
is about
about
1). Total
of the
340
Flow in
in the
the river
river isis influenced
influenced
340 km~
km.. Flow
by
rainfall; mean
mean daily
daily discharge
discharge varies
varies
by rainfall;
about o.sm:l
'sec in
in summer
summer to
to over
over
from about
from
0.5m sec
2.0J
(U .S.S.Geological
Geological
sec in
in winter (U.
203 mH sec
Survey,
Survey, 1968a)
1968a)..
Most
the tributaries
tributaries have
have been
been loglogMost of the
high turbidities in
in these
these
ged,
ged, resulting
resulting in
in high
streams
in the
the main
main river
river during
during
streams and
and in
concentrations of
Mean daily
daily concentrations
freshets. Mean
suspended
lower main
main
suspendedsediment
sedimentinin the
the lower
water-year 1968
1968 were
were ininexcess
excess
river
river in water-year
100 mgliter
mg / literon
on37
37days
days(U.
(US.
. S.GeoGeoof
of 100
highest mean
mean
logical
Survey, 11968bl.
logical Survey,
968b). The highest
CD
Brood years
yeors ore
calendar year
which
® Brood
ore def1ned
definedby
by the
the calendar
yeor in which
spawners
grovel.
spawnersbegm
begindepos1t1ng
depositingtheir
their eggs
eggs in
in the grovel.
For
example, f1sh
1n the
the 1968
1968 brood
brood were
were deposited
deposited
For example,
fish in
as eggs
of 1968
1968 and
and emerged
emerged
as
eggs mto
into the
the gravel
grovel in autumn of
from the
the grovel
gravel as
as fry
fry in
inspring
spring 1969.
1969.
from
LOCATION KEY
LOCATiON
0
E-:l
/
LEE1
Cf
C)
0
N
0
';lf/
PORT
ORFORD
90
I
2
Figure
Figure 1.
1.
4 5Km
Location
Location and drainage
drainage area
areaofofSixes
SixesRiver.
River.
[5]
(5]
4
daily
concentration of
of suspended
suspended sedisedidaily concentration
ment was
was 1,000
1,000 mgj
mg/liter.
ment
liter. In
In contrast
contrast to
these high
high turbidities
turbidities in
in the
these
the main
main river,
river,
Dry
Creek and
Dry Creek
and the
the South
South Fork
Fork remained
remained
relatively
flows .
relatively clear
clear during
during high flows.
Dry
Dry Creek
Creek is
is probably
probably the
the most
most important tributary
tant
tributary for
for fall
fallchinook
chinooksalmon.
salmon .
During
During the
the summer
summer the
the stream
stream bed
bed in
in the
lower
km either
either Contains
contains a series
series of
lower 33 km
isolated pools
poolsor
orisisdry.
dry. The
The surface
surface water
water
isolated
in this section submerges
submerges and
and flows
through the
the gravel
gravel bed.
bed. The
Thestream
streamabove
above
this
point continues
continues to
flow over
over the
the
this point
to flow
gravel surface.
gravel
Most
Most of the
the tributaries,
tributaries, particularly
particularly
Dry
Creek, contain
contain large
large quantities
quantities of
Dry Creek,
good
spawning gravel.
gravel. This gravel
gravel
good quality
quality spawning
consists of erosion-resistant
consists
erosion - r~sistant sandstone,
sandstone,
siltstone,
siltstone, and
and mudstone
mudstone dating
dating from
from the
Jurassic
the Cretaceous
Cretaceous periods
periods and
and
Jurassic to
to the
volcanic
volcanic igneous
igneous rock
rock of various compositions
the Jurassic
Jurassic Period
Period (Boggs,
tions from the
1969)
The main
main river differs from
from the
the
1969).. The
tributaries
generally being
lower
tributaries by
by generally
being of
of lower
gradient and containing
containing more
more deep
deep pools.
pools.
Riff!es
in the
the main
main river
river have
have aa higher
higher
Riffles in
concentration
of fine
fine gravel
gravel and
and sand
sand than
concentration of
those
those in
in the
the tributaries.
Most
tributaries are
cooler than
Most tributaries
are cooler
than the
main
river during
during the
the summer
summer months
months
main river
(Figure
The wide,
wide, exposed
exposed main
main river
(Figure 2)
2).. The
probably receives
receives more·
solar radiation
radiation
probably
more solar
narrow, shaded
shaded tributaries. DurDurthan the narrow,
ing summer
summer the main
main stem
stem of
of Sixes
Sixes River
River
has
considerable variation
maximum
has considerable
variation in maximum
along its
itscourse
course as
as measured
measured
temperature along
•. KRONENBERG
KRONENBERG BRIDGE
BRIDGE (13
(13 Km)
Km)
HIGHWAY
HIGHWAY101
101 (6
(6 Km)
CRYSTAL CREEK
- - - - - CRYSTAL
CREEK
-0-0-0- DRY
DRY CREEK
~
CREEK
EDSON CREEK
EDSON
CREEK
•
30
25
U
CJ
LU
LLI
0::
;:::)
20
~
I
0::
LLI
~
:IE
15
'.
_\
I
F5
LLI
1-
10
p5
MAY
JUNE
JULY
AUG.
SEPt
SEPT
OCt
OCT
Figure
Figure 2.
2. Comparison
Comparison of
maximum water
temperatures recorded
three tributribuof maximum
water temperatures
recordedweekly
weekly in
in three
taries
taries and two
two locations
locations in
in Sixes
Sixes River,
River, May-October
May-October 1969.
1969.
[(6]
6]
on one
one of the
the warmest
warmest days
days (Figure
(Figure 3)
on
3)..
The lower
lower part
the river
river is
is influenced
influenced
The
part of the
by marine
marine conditions
conditions of fog
fog and
and strong
strong
by
winds. However,
However, inland
inland about
about
northwest winds,
10
the climate
climate is
that of
10 km
km the
is similar
similar to
to that
interior valleys
valleys where
where high
high temperatures
temperatures
o::cur.
The main
main river
river was
was warmest in the
occur. The
North
Fork (31
km inland).
inland) . From
From the
the
(31 km
North Fork
North Fork
Fork to the
the South
South Fork,
Fork, maximum
maximum
temperatures ranged
ranged from
C. The
from 23 to 24 C.
South
had aa major
South Fork
Fork had
major cooling influence
on
on the maximum temperature in the main
that influence
influence extended
extended only
only aa
river, but that
river,
kilometers downstream.
downstream. In the lower
lower
few kilometers
10
prevailing winds
winds and
and fog
fog apap10 to
to 12 km prevailing
parently prevented the stream from
and may
may have
have had
had aa
warming extensively and
cooling influence.
influence.
The lower
lower 44 km
km of
of the river form an inor estuarine
estuarine area.
area . The
The river
river emp
emptertidal or
ties into
into the
the open
open ocean
ocean north
north of
ofCape
Cape
ties
Blanco through
mouth restricted
restricted by
by
Blanco
through aa mouth
low sand
sand dunes.
dunes. Most
the estuarine
estuarine
low
Most of the
work
in this
this study
study was
was confined
confined to the
the
work in
lower kilometer, representing a unit
somewhat
the remainder
remainder of
somewhat distinct
distinct from the
the estuary
(Figure 4)
Above the
the lower
lower
the
estuary (Figure
4).. Above
bay, the estuary is
is divided into
intodeep
deep pools
pools
bay,
separated
tide.
separatedby
byshallow
shallowriffles
riffles at
at low tide.
Prevailing northwest
and longlongPrevailing
northwest winds and
shore
sand at the
the
shore currents
currents form
form aa sill
sill of sand
mouth of the
the river
river ininsummer,
summer, creating
creating
mouth
aa shallow
shallow embayment.
embayment. Maximum
Maximum depth
depth
is about
Tidal fluctuafluctuais
about 55 m
m at
at high
high tide.
tide. Tidal
tions are usually
usually less
less than
than 11.5
m because
because
.5 m
of
the sand
sand sill
and narrow
narrow mouth.
mouth . As
As
of the
sill and
summer
progresses and
si II develops
develops
summer progresses
and the
the sill
at the
the mouth,
mouth, the
the low
low tide
tide level
level in
in the
the
at
estuary
gradually increases.
increases. The shoreshoreestuary gradually
is composed
composed of
flatbeaches
beaches
line is
of relatively flat
o MAIN
MAIN RIVER
RIVER
o
25
25
•
TRIBUTARIES
0
LU
I4 20
.
li
0
LU
•
0:
o
LU
0
_J
J
I-
4
~
(/)
U)
>I
00
5
00
~
0
00
0
~
(/)
I-
0
<!::Z:~
a:
•
zZ
• .•
.
ci >-W
0
a:UJO
~a:
wofr
w
LU
5
15
II-.
II
li
(I)
<!:
w
uj
0()
.
a:
0
0
li
cx
•.
a:
•
•
0.
0:
z
~
u..
(.!)
m iEffi
irl(/)
(1)
.-
1-1(/)I-
•
a:
cr
ct
4 .
<.!la:
::JO
D0
(f)
Cl)
50
e(J)
w
~
4
Id
:z:
I
15
20
25
10
KILOMETERS
ABOVE THE
THE MOUTH
MOUTH
KILOMETERS ABOVE
30
35
Figure
maximum temperature
temperature along Sixes
Sixes River
tributaries on
on August
August
Profile of maximum
River and
and in tributaries
Figure 3. Profile
3, 1970
1970 from
from 1642
1642 to
to 1800
1800hours.
hours.
[(71
7]
V.
?
1)
a/VC
çH\
C\
The
at the
the mouth
mouth creates
creates aa twoThe si
sillII at
layered
layered system
system in
in the estuary on ebb tide.
Cold salt
water is
is retained
retained on
botCold
salt water
on the bottom,
while warm
warm fresh
fresh water
water moves
moves
tom, while
downstream above
water and
and
downstream
abovethe
the salt
salt water
over
through the
the narrow
narrowchannel
channel
over the
the sill through
into
into the
the ocean.
ocean. The
The interface
interface between
between
these
layers at
tide is
sharply
these two
two layers
at low
low tide
is sharply
with as
as much
much as
as 10
10 C
C difference
difference
defined with
temperature and
and 25°
; oo difference
difference in
in temperature
25°/oo
salinity.
Waterinineach
each density
density layer
layer apapsalinity. Water
parently
remains discrete
discrete despite
despite strong
strong
parently remains
northwest winds. On
On flood
flood tide the mouth
is inundated
inundated by
by cold,
cold, full-strength
full-strength sea
sea
is
water,
extensive vertical
water, resulting in extensive
vertical mixmovement of the water
water
ing at the mouth, movement
mass
and presumably
presumably rejuvenrejuvenmass upstream, and
ation
nutrients in
in the
the estuary.
estuary. Water
ation of nutrients
flow is out of
of the
the bay
bay about
about 75%
75 % of the
the
time
and into
bay about
about 25
% of the
the
time and
into the bay
25%
time.
time.
/
/
ac
0
in
f
0
100 200
SCALE IN METERS
METERS
Methods
Sampling
Sampling of the Adult
Adult Population
Population
DEPTH CONTOURS
CONTOURS • I m
DEPTH
rn
LANDINGL
Figure
Figure 4. The
of Sixes
Sixes River
River esesThe lower
lower part of
tuary
tuary at
at mean
mean tide
tideshowing
showingnumbered
numbered
sampling
sampling stations
stations and
and depth
depth contours
contours
(areas less
less than
than 11 m
m deep
deep are
are stippled).
stippled).
(areas
Information on
on timing,
timing, distribution,
Information
and characteristics
characteristics of spawning
spawning fish was
and
obtained
and dead
dead fish
obtained by
by examining live and
on
on the spawning grounds.
grounds. Attempts
Attempts were
were
made
sample spawning
made to
to sample
spawning fish
fish in proportion to their abundance,
abundance, but fre
fre-quency
sampling depended
depended on stream
stream
quency of sampling
conditions and
and the
the time
conditions
time required
required for
each survey. Duri~g
each
the last 33 years
years
During the
all
spawning areas
areas were
were sampled
sampled every
all spawning
77 to
to JO
10 days
days with
wit!-! both
both live
liveand
and dead
dead
fish counted.
counted. Total
counts on aa survey
survey
Total counts
represented all live fish
fish observed
observed and
and
those
dead fish
fish not
those dead
not previously
previously counted.
counted.
For each
each dead
dead fish
fish found on the
For
the spawnspawning
grounds, locality,
date, length,
length, and
and
ing grounds,
locality, date,
sex
were recorded
recorded and
and aa scale
scale sample
sample
sex were
taken.
of sand
sand and
and gravel,
gravel, so
so small
small increases
increases in
in
depth
rapidly increase
increase the
size of the
the esesdepth rapidly
the size
tuary. In
some years
years short-term
short-term sand
sand
In some
occurs at
mouth,
blocking irregularly occurs
at the mouth,
if the
the sill
sill builds
builds rapidly.
rapidly. The
level
The water level
in the bay
in
bay then rises
rises from tidal
tidal invasion
invasion
and river
river inflow.
inflow. When
When the
the water
water level
level
and
reaches
the sand
sand bar,
bar, erosion
erosion
reachesthe
the top
top of the
rapidly
opens aa new channel
rapidly opens
channel and lowers
lowers
the water level.
the
level.
During
discharge in
During high
high river discharge
in winter,
the intertidal
the
intertidal area
area is fresh
fresh water
water and
and
Sampling of the Juvenile
Sampling
Juvenile Population
Population
short. However,
However, occasional
occasional low-river disdischarge
charge during
during winter
winter allows temporary inA variety
variety of
ofgear
gear was
was used
used to
to sample
sample
vasion
vasion of
of salt
salt water
water along
along the
the bottom.
bottom. juveniles,
but seines
seines were
primary
juveniles, but
were the primary
In the spring,
spring, as
as river flows drop,
drop, estuarestuar- equipment. Operations
Operations extended
extended from
me conditions are
ine
are re-established.
re-established.
small tributaries downstream through
[18]
8]
ocean surf.
ocean
Population
Population estimates
estimates of juveniles
juveniles in
969
lower estuary
estuary were
were made
made in
in 11969
the lower
Fresh-Water Studies
Studies
cold branding
branding (Everest
(Everest and
and EdmundEdmundby cold
1967) and
and releasing
releasing fish
fish captured
captured
son, 1967)
son,
the main
main river,
river, estuary,
estuary, and
into the
the
the
and into
the spawning
spawning tributaries
tributaries and
and the
the
In the
river, small-mesh
small-mesh seines
seines were
were used.
used.
main river,
downstream were
were traptrapJuveniles moving downstream
ped at several
several sites
sites as
as time
time permitted
permitted
ped
during
the study.
study. During
the spring
spring of
During the
during the
1970, aa small
downstream trap
trap was
was
small downstream
1970,
operated
Edson Creek.
Creek. This
This equipequipoperated in Edson
consisted of
of screened
screened panels
panels leadleadment consisted
ing
trap".
ing from
from each
each bank
banktoto the
the "V
"V trap".
This
method provided
provided good
good data
data for
This method
short periods
periods during
stable flows,
flows, but
but
short
during stable
was unreliable
unreliable for long-term
trapping
long-term trapping
was
because of
freshets.
because
of washouts
washouts during freshets.
Craddock fyke
trap was
~as periodically
periodically
A Craddock
fyke trap
operated in
during spring
spring
operated
in the
the lower river during
and
summer. In
1969 three
three fyke
fyke traps
traps
In 1969
and summer.
were
set. During
high flows
flows trapping
trapping
During high
were set.
was incomplete,
flows the
the
was
incomplete,but
butatat low
low flows
traps
stream.
traps extended
extended across
across the
the entire stream.
This
trapping indicated
indicated the
timing of
of
This trapping
the timing
downstream migration
migration and
and characterischaracterisdownstream
tics
migrating juveniles,
juveniles, but
was intics of migrating
but was
adequate
magnitude of
adequatetoto estimate
estimate the
the magnitude
downstream
movement.
downstream movement.
Captured
usually ananCaptured juveniles
juveniles were
were usually
esthetized
MS 222
222 and
and measured
measured in
esthetized in
in MS
the field
field to
to the
the nearest
nearest 0.1
0 . 1 cm
em fork
fork
the
length. Samples
Samples of
juveniles were
were prepreof juveniles
scale analysis.
served
served for
for scale
analysis. Fish
Fish were
were fixed
solution of
of formaldehyde
formaldehyde for
in
7 .6% solution
in aa 7.6%
for
14
24 hours,
hours,
14 days,
days, placed
placedinin water
water for
for 24
and
36.5 % isopropyl
isopropyl alaland then
then stored
stored in
in 36.5%
cohol.
Estuarine Studies
The
used
The primary sampling equipment used
the estuary
estuary was
was aa 38-rn
38-m bag
bag seine
seine
in
in the
with stretched
stretched mesh
mesh size
sizeofof 2.0
2.0 em
cm in
the
wings and
and 11 .3
in the
the bag.
bag. DurDurthe wings
.3 em
cm in
each year,
year, the inshore
inshore
ing
ing early
early spring of each
estuarine
estuarine population
population and
and juveniles
juveniles in
in the
the
mouth
the river
river and
and in
in the
theocean
ocean
mouth of
of the
surf were
were caught
caught with
with either 9-m
9-rn or 25-m
25-rn
Occasionally an
an Oneida
beach
seines. Occasionally
Oneida
beach seines.
Lake
the estuary.
estuary.
Lake trap
trap was
was set
set in
in the
over aa 2- or
or 3-day
3-day period
period and
and then
then rere over
sampling for
the marked
marked to
to unmarked
unmarked
sampling
for the
about 55 days
days later.
later. Fish
Fish were
weremarkmarkratio about
ed at each
each station
station in
in proportion
proportion to
to the
the
ed
number seined.
seined. An
An attempt
attempt was
was made
made
number
mark 10%
10 % of
of the
the population,
population, but
but the
the
to mark
supply of liquid
liquid nitrogen
nitrogen coolant
coolant limited
limited
supply
work to
to33days.
days.
work
Fish were
marked at aa central
central station
station
Fish
were marked
under aa shelter
shelter to reduce
reduce formation
formation of
of
under
the brands
brands caused
caused by
and
ice
on the
ice on
by wind and
moisture. All
All captured
captured fish
fish were
werehauled
hauled
moisture.
the marking
marking station
station and
and sorted
sorted into
into
to the
holding pens.
pens. Newly
Newly marked
marked fish
fish and
and
recaptured marked
transported
recaptured
marked fish
fish were transported
and released
released at
their capture
capturesite.
site.RanRanand
at their
dom mixing
mixing was
was assumed,
assumed, based
based on
dom
on the
distribution of
of recoveries
recoveries of fish
fish uniqueuniquely
marked at individual
individual stations
stations in
in 1967
1967
ly marked
(Fish
Commission of
Oregon, 1968).
1968) .
(Fish Commission
of Oregon,
The
The recovery
recovery effort was
was completed
completed in
in
2 days.
On the
the 1St
1st day,
day, stations
stations 1,
1, 3,
days. On
and 6 were
were sampled
sampled (Figure
(Figure 4)
4,
4, and
4).. All
fish were
fish
were held
held until
until seining
seining was
was comcomThe marked
pleted at
at aa station.
pleted
station . The
marked and
and
unmarked fish
fish were
unmarked
were then
then sorted,
sorted, meameaThe next
sured, and
and released.
released . The
next station
station
sured,
"upstream" (against the
visited was
was "upstream"
tidal
tidal current
current from
from the
the last
last station)
station) to
prevent handled
handledfish
fish from
from drifting
drifting into
prevent
the
the next
next sample.
sample. On
On the
the 2nd
2nd day
day of
the recovery,
seining was
was done
done at
at stathe
recovery, seining
stations 7,
7, 9,
9, 10,
tions
10, and
and 12
12 at the
the same
same tidal
tidal
stage as
as the
the previous
Fish were asstage
previous day.
day. Fish
assumed to
to be
be in the
sumed
the same
same relative
relative posiposithe 22 days.
days.
tion
on the
tion on
the estuary
Growth
juveniles in the
estuary
Growth of juveniles
was monitored
monitored weekly.
weekly. A sample
of fish
fish
was
sample of
from various
stations was
was measured
measured to
from
various stations
the nearest
cm fork
fork length
the
nearest 00.1
. 1 em
length in
in MS
MS
222.
fish that
222. All branded
branded fish
that were
were recovrecovered were
were measured
to provide
provide an
an indeered
measured to
independent check
checkon
onthe
the rate
rate of
of growth
growth of
of
pendent
individuals inin the
individuals
the population,
population, eliminateliminat-
[(91
9]
ing
the effect of
of recruitment
recruitment from
from upuping the
stream.
Samples of
fish were
were preserved
preserved
stream. Samples
of fish
for scale
scale analysis.
analysis.
Behavior Studies ·
The
behavior of
newly emerging
emerging fry
The behavior
of newly
fry
and
their subsequent
subsequent fate
fate ininsocial
social popupopu and their
were primarily
primarily investigated in
lations
lations were
small
observation troughs
troughs simulating
simulating aa
small observation
stream
environment. These
The~e observation
observation
stream environment.
troughs
possessed simulated
troughs possessed
simulated redds
redds where
eyed eggs
eggs could
be planted
planted to
to allow
allow
eyed
could be
natural
natural emergence
emergenceofof juveniles
juveniles from
from the
the
addition, experiments
experiments were
were
gravel. In
In addition,
run
in emergence
emergence boxes
boxes that
that consisted
consisted
run in
primarily
the simulated
simulated redd
redd from
primarily of the
from the
observation troughs (Reimers, 1970)
1970)..
Some
started by
Some experiments
experiments were
were started
juveniles in the
the troughs.
troughs.
simply
simply planting
planting juveniles
These
trapped from
These fish
fish were
were seined
seined or
or trapped
from
nearby natural
rearing area
area or
transaa nearby
natural rearing
or transplanted
another experimental
experimental syssysplanted from another
tem. In
tem.
experiments natural emerIn other experiments
gence of
the gravel
gravel reprerepregence
of juveniles
juveniles from the
sented the
the beginning
sented
beginning of an
an experiment.
experiment.
Scale Studies
Scales were
were removed
removed from
from the
Scales
the second
second
or third
or
th ird scale
scale row
row above
above the
the lateral
lateral line
line
in the
of the
in
the area
area below
below the
the insertion
insertion of
the
dorsal fin
fin.. Usually
Usually three
three scales
scales from
from
spawners
and three
three or more
spawners and
more scales
scales from
juveniles were
juveniles
were taken.
taken. Plastic impressions were
were made
made of
of these
these scales.
scales.
sions
The scales
were magnified
magnified98X
98X with
The
scales were
Tn-simplex microprojector onto aa
aa Tri-simplex
table top.
top. AA mask
table
mask was
was placed
placed over
over the
scale
image and
and centered
centered on
on the
scale image
the nunucleus.
cleus. The
The anterior-posterior
anterior-posterior line
line on
on the
mask was
the long
long axis
axis
mask
was oriented
oriented with
with the
of the
the scale.
scale. Counts
Countsand
andmeasurements
measurements
circuli were
were made
made along
along aa line
line 20°
20 °
of circuli
to the
the dorsal
dorsal side
side of the
the anterior-posteranterior-posterior axis
ior
axis of the
the scale.
scale. The
The selected
selected 20°
20°
lines on
lines
on the
the scales
scales of
of spawners
spawners and
and jujuveniles
veniles appeared
appeared to correspond
correspond closely.
closely.
best scale
scale was selected from
from each
each
The best
fish. Those
Those that
that were
wereobviously
obviouslyregenregenerated
erated or
or those
those with
with irregularities
irregularities along
along
the
axis were
were not
not used.
used. Regenera
Regenera-the 20° axis
the first
f irst few
fewscale
scale circuli
circuli was
was
tion
tion of the
checked by
the distribution
distribution of
of
checked
by plotting
plotting the
platelet distances.
distances. Platelet distance
distance was
was
platelet
defined as
as extending
center of
defined
extending from
from the center
the nucleus
nucleus to
the outside
outside edge
edge of the
the
the
to the
first visible
visible circulus.
circulus. Scales
Scaleswith
with platedistances larger
larger than
mm were
were
let distances
than 8.2 mm
excluded
(Figure 5)
excluded (Figure
5)..
narrow strip of
of paper
paper with aa ruled
ruled
A narrow
was placed
placed directly
the 20°
20 °
line was
line
directly over
over the
axis. The
outside edge
the platelet
platelet
axis.
The outside
edge of
of the
and
outside edge
edge of
of each
each succeeding
succeeding
and the outside
circulus encountered along the line
were marked.
marked . All
circuli on
on the
the juvenjuvenAll circuli
ile
scales were
maximum
ile scales
were marked,
marked, but aa maximum
of 50
50 were
were marked
marked on
on the
the scales
scales from
from
spawners.
spawners. Measurements
Measurements of
of bands
bands of
of five
circuli were
were made
made to
to the
the nearest
nearest 0.1
0.1
circuli
mm with
w ith aa vernier
vernier caliper.
caliper. The
The point
point
mm
separation between
between fresh-water,
fresh-water, esesof separation
tuarine, and
and oceanic
oceanic growth on the
scales of
spawners was
estimatscales
of spawners
was visually
visually estimated and
and marked
marked on
paper. Counts
Counts of
ed
on the paper.
and measurements
measurements of
of scale
scale diadiacirculi and
meter were
were made
made on
on these
theseselected
selectedareas
areas
meter
were compared
compared to similar data
and were
for
juveniles of known
known life
life history.
history.
for juveniles
Results
Results
Time of
of Egg
Egg Deposition
Deposition
Location and Time
Initially, information
information was
was gathered
gathered on
on
spawning populations
populations of fall chinook
spawning
salmon in Sixes River to determine
and when
when eggs
eggs were deposited
deposited in
in
where and
the gravel.
gravel. Spawning
Spawning occurred
occurred primarily in Dry,
Dry, Edson,
Edson, and
and Crystal
Crystal creeks,
creeks,
and in
upper Sixes
Sixes River
River (Figure 6)..
6) ..
in upper
About 60 to
to 70%
70 % of
ofthe
theruns
runsspawned
spawned
About
in
Dry Creek
Creek (Table
(Table 1).
1) .
in Dry
Table 1.
1. Percentage
Live and
and
Table
Percentageof
of the
the Total Live
Salmon Observed
Observed in
in Sixes
Sixes
Dead Chinook Salmon
River
Were Found
Found in Dry
Dry Creek.
Creek.
River that
that Were
Year
Year
1967-68
1968-69
1969-70
1969-70
[ 10]
(10]
Spawners
=----=;-.,-S~
p~
a_::
wn:_:e:.:,:
rs:--.=::;:
Sixes River
Dry Creek
Sixes
1,902
2,504
1,271
1,271
1,351
1,351
1,823
1,823
779
Percentage
Percentage of
of
Spowners
Spawners in
Creek
Dry Creek
71.0
72.8
61.3
60
•
55
ii
D
50
REGENERATE nr3l
REGENERATE
n =31
= 284
284
NONREGENERATE n =
ILl
0
w
~
z 45
ILl
0::
a::
0::
:::>
0
8
40
35
u.. 30
0
tzz
25
ILl
LU
:::> 20
0
~
Lii
r
0::
u..
15
IS
10
5
3456 Hill
3
4
5
6
.
-
6
4
2
77 8
12
14
16
0
8
9 10
PLATELET DISTANCE
IN MM
MM AT 98X
DISTANCE IN
8
-J
200
distancesinin aa sample
of scales
from fall chinook
Figure
platelet distances
sample of
scales from
chinook
of platelet
Figure 5. Distribution of
salmon
sorted into
into regenerate
regenerate and
and nonregenerate.
nonregenerate.
salmon visually
visually sorted
.4
Distributionof
of the
the spawning
spawning population
population of
nf fall
Figure 6. Distribution
fall chinook
chinooksalmon
salmon ininSixes
Sixes River,
River,
Figure
Oregon,
1964
to
1970.
Oregon, 1964
1970.
[[11]
11 ]
Most
NovemMost spawning
spawning occurred
occurred from
from November
January, as
as indicated
indicated by
by counts
counts
ber to January,
in
lower Dry
Dry Creek
Creek (Figure
(Figure 7)
Other
in lower
7).. Other
streams
pattern . The
The
streams showed
showedaa similar
similar pattern.
earliest
. any fish
fish were
wereobserved
observed on
on
earliest that
thatany
the
spawning grounds
years of
the spawning
groundsinin the
the 77 years
the
was November
November 13.
13. Fresh
the study was
Fresh carcassesand
andan
an occasional
occasionallive
live fish
fish were
casses
were
observed as
observed
as late
as February
February 21.
21 . Data
Data
late as
from
the spawning
spawning populations
populations showed
showed
from the
that
juveniles would
would emerge
emerge from
the
that juveniles
from the
gravel
river system
system and
and
gravel throughout
throughout the
the river
that emergence
emergence could
expected over
over
could be expected
aa period
period of about
about 60 to
to 90
90 days.
days.
Time
Emergence
Time of Emergence
The earliest
The
earliest that
that newly
newly emerged
emerged jujuveniles were
captured in
the spawning
spawning
veniles
were captured
in the
streams was
was March
streams
March 11
1 1 in Edson
Edson Creek.
Creek.
fish were
Five fish
were caught
caught in eight
seine
eight seine
hauls.
By early April many newly
emerged
in Edson
Edson Creek
Creek
emerged fish
fish were
were found in
and
river.
and other
other parts
parts of
of the river.
In 1970
the downstream
downstream trap
trap was
was
1970 the
periodically
operated in Edson
Creek
periodically operated
Edson Creek
from
March 27 to
to June
June 4.
4 . On
On the
the first
from March
night
trapping, 286
286 fry
fry ranging
ranging in
in
night of
of trapping,
length
3. 9 to
to 4.3
4 .3 cm
em were
were caught.
caught.
length from
from 3.9
Fish
this newly
newly emerged
emerged size,
size, some
some
Fish at
at this
with yolk rema1n1ng,
remaining, were caught
through
last trapping
trapping in
in June,
June, sugsugthrough the
the last
gesting
emergence was
was protracted
protracted
gesting that emergence
(Figure
The trapping
trapping data
data were
were asas(Figure 8)
8).. The
sumed
closely represent
represent the
pattern
sumed to
to closely
the pattern
of emergence
emergence because
because captured
captured juveniles
were
small and
and often
often possessed
possessed yolk.
yolk.
were small
Judged from
the periodic
periodic trap
trap catches
catches
Judged
from the
through
spring, peak
peak emergence
emergence in
in
through the spring,
Edson Creek
to late
Edson
Creekcame
camefrom
from mid
mid to
Apri I (Figure
(Figure 9).
9) .This
Thiswas
wasapproximateapproximateApril
days after the time
of peak
peak
120 days
ly 120
time of
spawning
that stream.
stream. Seining
data
spawning in
in that
Seining data
collected in Edson Creek
concurrent
Creek concurrent
with trapping
trapping provided
provided similar
similar results.
results.
with
25C
250
200
o
0 1967-68
1967-68
• 1968-69
1969-70
00 1969-70
0
•
::1:
(0
C/l
ii 150
i&:
....
00
U-
•
ffi
ID
:::E 100
100
;:)
z
50
0
0
/
O• OD I_________
JANUARY
0
NOVEMBER
0
DECEMBER
JANUARY
•
FEBRUARY
FEBRUARY
Figure 7.
7. Total
Total number
number of
chinook salmon
lower Dry
Dry
of fall
fall chinook
salmonobserved
observedonon each
each survey
surveyinin lower
Creek, 1967-68 to 1969-70.
1969-70. Totals
Totals include
dead fish,
fish, both
both adults
adults and
and
include live
live and
and dead
jacks
jacks (line fitted
fitted by
by inspection).
inspedion) .
[12)
(12]
8.0
7.5
7.0
221
f
N
N
MEAN
z(.) 6.5
C,
~
MEAN
so
SD
RANGE
II
II
6.0
50
t 5.5
~
5.5
79
5.0
U
..J
-J
1.1.1
Si
a: 4.5
:11:
f2 4.0
3.5
3.0
MAY
APRIL
MARCH
Creek,
Edson Creek,
downstream in Edson
Lengthof
of juvenile
juvenilefall
fall chinook
chinook salmon
salmon moving
moving downstream
Figure 8. Length
Figure
1970.
14
'4
•
•
13
12
II
•
10
l0
:E:
(09
9
(/)
ii:
IL
8
(/)
7
0
0
ILl
~
6
:::>
5
z
:E:
•
•
4
I'
•
3
•
2
..
I
0
MARCH
MAY
APRIL
JUNE
in
downstream in
moving downstream
chinook salmon
salmon moving
Catch per
per trap-night
trap-night of
of juvenile
juvenile fall chinook
Figure 9.
Figure
9, Catch
by
inspection
l
.
EcisonCreek,
Creek,1970
1970(line
(line fitted
fitted
inspection).
Edson
[ 13 ]
[13]
Downstream
DownstreamMigration
Migration and
and Behavior
Behavior of
of
Newly
Emerged Fry
Newly Emerged
A large
large number
number of
of juveniles
juveniles appeared
appeared
to move
move downstream
downstream as
as recently
recently emergemerged fry and
and most
most moved
moved at night.
night. The
The
ed
Edson Creek
was checked
checked at dawn
dawn
Edson
Creek trap
trap was
and
and dusk
dusk on
on 15
15 days
days during
during 1970.
1970. Less
Less
than
% of the
the fish
fish moved
moved during
during the
the
than 55%
hours of
daylight and
and more
more than
than 95%
95 %
hours
of daylight
of the fish moved during da
rkness
darkness
(Table 2).
Factors controlling this
downstream
downstream movement
movement were
were further
further explored
experimental work.
work.
plored in experimental
Table
downstream
Table 2. Temporal
Temporal pattern
pattern of downstream
migration
juvenile fall
fall chinook
chinook salmon
salmon
migration of juvenile
Edson Creek,
Creek, 1970.
1970,
in Edson
Day
Day
Date
March 29
March
30
31
April
April
May
May
%
N
N
1
2
8
9
14
15
16
23
5
6
7
8
Total
Average
1
3 2.0
1 0.4
11 0.9
2 1.5
1.5
1 0.9
3 4.4
4 2.7
8 0.6
21 1.8
0 .9
6 0.9
3 1.5
1.5
1.0
5 1.0
3 0.8
1.0
5 1.0
8
1.5
74
1.2
1
1
N
ight
Night
N
%
N%
150 98.0
264 99.6
99.6
109 99.1
137 98.5
109 99.1
65 95.6
146 97
.3
97.3
1,279
1,279 99.4
1,131
1, 131 98.2
692 99.1
200 98.5
510
510 99.0
360 99.2
494 99.0
521
98.5
6,167
6, 167
98.8
Total
tures
pattern (10-12
( 10-12
tures followed
followed the
the diel
diel pattern
C)
Records were
the diel
diel patpatC).. Records
were kept
kept of the
tern
of emergence
emergence and
the number
number of
of
tern of
and the
fish
emerging daily
their
fish emerging
daily inin relation
relation to
to their
size.
Some
began emerging
the
Some fish
fish began
emerging from
from the
gravel shortly after hatching (Figure
110).
0) . Others
Others continued
continued to
to emerge
emerge prior
prior
to
yolk absorption,
absorption, but
but peak
peak emeremerto total yolk
gence
t il afte
r the
gencedid
didnot
not occur
occurun
until
after
the fry
reached
Beginni ng on
on
reached maximum
maximum weight.
weight. Beginning
Ma rch 15,
% of
the fry
March
15, 1970,
1970, when
when77%
of the
had
gravel, the
trap
had emerged
emergedfrom
from the
the gravel,
the trap
was
14
was checked
checkedatat dawn
dawn and
and dusk
dusk for
for 14
consecutive
days. About
About 20%
20% of
of the
consecutive days.
juveniles emerged
day and
and
juveniles
emerged during
during the
the day
the
(Table 3)
3) .
the rest
rest at
at night (Table
Diel
paHern of emergence
emergence of
juDiel pattern
of juvenile fall chinook
chinook salmon
salmon planted
planted as
as
venile
Table 3.
Table
N
153
153
265
110
110
139
139
110
110
68
150
150
1,287
1,152
1,152
698
203
515
363
499
529
6,241
eyed
eyed eggs
eggs in
in an emergence
emergence box,
box, 1970.
Day
N
ight
Night
3
18
18
19
19
20
21
22
23
24
25
26
27
28
1
1
33
5
5
7
4
8
8
9
9
19
19
7
8
8
8
1
Total
Percentage
97
19.7
19.7
Date
Date
March
15
16
16
17
17
Emergence Behavior
Behavior
Emergence
Several experiments
experiments were
Several
were conducted
conducted
to examine
time of emergence
of juveto
examine time
emergence of
juveniles
in their beniles and
and to study
study changes
changes in
behavior
havior in the
the stream
stream environment.
environment. The
The
eggs from
from one.
female from Edson
eggs
one female
Edson Creek
were
were fertilized using
using one
one male
male and
and held
held
in aa Heath
at the
in
Heath incubator
incubator at
the Elk
Elk River
River
Salmon
Hatchery inin autumn
Salmon Hatchery
autumn of 1969.
1969.
When the
the eggs
eggs reached
reached the
the eyed
eyed stage,
stage,
they were randomly
they
randomly divided
divided into
intoexperiexperimental lots.
mental
lots.
In the first experiment,
experiment, 600 eggs
eggs
were
were planted
planted into
into an
anemergence
emergence box.
box.
The emergence
box was
to the
emergence box
was exposed
exposed to
the
normal light-dark
light-dark cycle
cycle and
and temperatempera-
1
31
52
80
80
21
21
23
44
4
13
22
21
26
33
40
61
61
99
87
29
29
24
395
80.3
492
100.0
I
8
1
.
Total
15
17
17
18
18
25
second experiment,
experiment, two
two groups
groups
In aa second
of advanced
advanced alevins
alevins were
were planted
planted into
into
separate
experiseparate emergence
emergence boxes.
boxes. This experiment was
was identical
identical in
in design
design to
to the
the first,
except that
that one
one emergence
emergence box
box was
was
completely
covered with black
black polyethypolyethycompletely covered
lene sheeting to maintain continual
lene
darkness.
emergence box was
was
darkness. The
The other emergence
exposedto
to the
the normal
exposed
normal light-dark
light-dark cycle.
cycle.
was checked
checked on 12
12 days
days
The experiment was
at dawn
dawn and
and dusk
dusk from
from April
April 11
11 to
to 23,
23,
1970. Tn
In the
box about
about 9%
9 % or
or
1970.
the control
control box
fish emerged
emerged during
duringthe
theday
dayand
and91
91%
%
30 fish
[ 14]
(14]
0 .65 r-- - -0.65
iii=
~
c(
- - --
- - --
-
---,
10
~
;!l: 0.60
0 .60
•S
!;;
t!>
CD
•
•
~
••
•
...
0 .55
w 0.55
~
a:
~
0 .50 1 - - - - -0.50
- --
- -- - -----i
tOO
100
90
880
0
:c
70
70
If
60
!!;
50
::
19
i
40
40
:::>
z
30
30
20
tO
I0
5
0
IS
20
25
most
emerged in the
the evening
evening period
period
most emerged
(Figure 11)
1 1).. In continual darkness,
emergence
fish was
was distributed
distributed
emergenceofof 299
299 fish
throughout 24
slightly
throughout
24 hours
hours but
but with aa slightly
higher
peak in
the afternoon
afternoon (Figure
In the
higher peak
11
) . The
The null
nullhypothesis
hypothesis of
of equal
equal numnum11).
bers emerging
the four
four periods
periods
bers
emerging during
during the
was rejected
(X 1 = 18.6;
18.6; P<.01).
P<. Oll .Barns
Bams
was
rejected (X
(1969J
showed that
that fry
fry increase
increase their
their
(1969) showed
and move
move to
to the
the gravel
gravel surface
surface
activity and
during maximum
maximum temperatures
temperatures in the
during
afternoon. Under
Under the
the normal
normal light-dark
light-dark
afternoon,
cycle, actual
actual emergence
emergence of these
these fish
cycle,
from
the gravel
gravel was
from the
wasinhibited
inhibited until
until light
levels decreased
decreased at dusk.
dusk.
levels
Based
obBased on
on stream
stream and
and experimental
experimental observations, both
both downstream
downstream migration
migration
servations,
and emergence
emergence from
the gravel
gravel occur
and
from the
primarily during darkness.
darkness. With
the posposWith the
sibility
that fry
fryemergence
emergence and
and downdownsibility that
stream movement
movement could
be closely
closely rerestream
could be
30
MARCH
1 00~--------------.
NORMAL
LIGHT
CYCL E
:: rORMAL
LIGHT
CYCLE
eo
Temporal pattern
pattern of
Figure 10.
10. Temporal
of emergence
emergence
Figure
and
change in weight of
of newly
newly emerged
emerged
and change
fall chinook
chinook salmon
salmon planted
planted as
as eyed eggs
in an emergence
emergence box,
1970.
box, 1970.
60
50
0
40
~
Ui
CD
or
317 fish emerged
emerged at
the exexor 317
at night.
night. In
In the
perimental
perimental box
box about
about 59
59%
% or
or 214 fish
fish
emerged during
during the
the normal
emerged
normal hours of dayday1 51 fish
fish emerged
light and
and 41
41%
emerged dur% or 151
ing
normal period
period of
of darkness.
darkness.
ing the normal
In this
this second
second experiment,
experiment, the
the trap
trap
In
catches were
the end
end
catches
were also
also checked
checked at
at the
four major
major periods
periods of the
the day:
day : evenevenof four
ing (dusk
(dusk to
midnight) , night
night (midnight
(midnight
ing
to midnight),
to dawn),
dawn ) , morning
morning (dawn
(dawn to
to midday),
midday ) ,
to
and
The
and afternoon
afternoon (midday
(middaytoto dusk)
dusk).. The
control
system was
was checked
checked on
days
control system
on 77 days
and
experimental system
system was checkand the experimental
In the
ed on 66 days.
days. In
the control
control system
system aa
ed
total of 300
300 fish
fish emerged.
emerged. The
The distribution of
of emergence
emergence showed
showed that under
under
the
the normal
normal light-dark cycle,
cycle, not only did
did
more
emerge during
during darkness,
darkness, but
but
more fish emerge
~
20
20
I-
~
WI1 00~-L-~-L-~-~==~~-~-4
~
1&1
Ui
0
a.
CONT INUAL DARKNESS
OARKNESS
CONTINUAL
eo
50
60
so
40
20
20
EVENING
NIGHT
MORNING
MORNING AFTERNOON
AFTERNOON
OF EMERGENCE
EMERGENCE
PERIOD OF
Figure
11 . Diel pattern
pattern of
of emergence
emergence in
in
Figure 11.
four periods
periods of
juvenile fall
four
of the
the day
day for juvenile
chinook
chinook salmon
salmon in emergence
emergence boxes
boxes exposed to
light-dark cycle
cycle and
and
posed
to the normal light-dark
continual darkness,
darkness, 1970.
1970.
continual
[(15]
15 ]
lated, and
and that fry
fated,
fry moving
moving downstream
downstream
on any
on
any given
given night
might also
also have
have
night might
emergedon
on that
that same
emerged
same night, additional
additional
observations were
were made.
made.
observations
In experiments in the observation
troughs,
troughs, actual
actual emergence
emergenceofofaa few
few fry
was
dusk.
was observed
observedduring
during the
the day
day or
or at dusk.
In
most cases
cases the
made aa rapid
rapid dart
In most
the fry made
from the
from
the gravel
gravel and
and erratically
erratically swam
swam
downstream
upstream or side
downstream or
or into
into the upstream
walls.
Then the
the fish
fish usually
usually settled
settled on
on
walls. Then
the
for aa few
fewseconds
seconds to
to several
several
the bottom for
minutes
before swimming
swimming up
up in the
minutes before
water column.
column . Filling
the swim
swim bladbladFilling of the
der was
der
was usually
usually attempted
attempted fairly
fairly soon
soon
was not
not always
always successful
successful on
the
but was
on the
attempt. The
Thefish
fishgenerally
generally swam
swam
first attempt.
in jerking
movements with
jerking movements
with their tails
lowered.
Some fish
swam to the
the surface
surface
lowered. Some
fish swam
and
times, while
while
and gulped
gulped air
air four
four or
or five times,
others gulped
others
gulped only
only once.
once. Several
Several fish
were observed
observed to
and remain
remain
were
to calm
calm down and
stationary in the
water column.
column. One
One
the water
fish, identified
identified by
by aa unique
unique parr-mark
parr"mark
pattern, remained
remained at the
the same
same site where
where
it emerged
emerged until the
experiment was
was
the experiment
ended.
ended. Most fish
fish immediately
immediately disappeardisappeardownstream and
were lost
lost among
among
ed
ed downstream
and were
resident
Several fish
fish moved
resident fish,
fish . Several
moved immeimmediately out of the
the systems
systems into the
the traps.
traps.
These observations
observations led
led to experiments
These
experiments
examining
the post-emergence
post-emergence developdevelopexamining the
ment of
of juveniles
juveniles as
as they
they became
became resiresiment
dent in
dent
in stream
stream populations.
populations.
Development of
of Stream
Stream Residence
Residence
Three experiments
Three
experiments were
were conducted
conducted
from
from April 21
21 to
to29,
29,1970,
1970,where
where small
small
groups of
that had
had emerged
emerged on
on aa
groups
of fry that
given night
night were
were placed
placed inin aa trough
trough to
given
observe whether
whether they
they tended
observe
tended to remain
remain
there or
there
or move
move downstream.
downstream. Over
Over the
the
succeedingdays
daysfish
fish that
that moved
succeeding
moved downdown stream were
were placed
stream
placed back
back upstream
upstream on
the
the next
next day.
day. These
These experiments
experiments showshowed that few fish
ed
fish remained
remained in
in the
the troughs
troughs
on
the 1st
1st day
day out
out of
of the
thegravel.
gravel. Each
on the
succeeding
day more
more fish
fish tended
tended to stay
stay
succeeding day
(Figure 12).
12) .
(Figure
100
lOG
EXP.
NO. I
EXP NO.
N
23
N• 23
8Sc0
660
0
r-
40
40
20
!z
z
100
too
:I
...
a:
80
$0
...
60
ffi
40
<i
~
uU
_0_
EXP.
EXP. NO.
NO. 22
N
2!5
N• 25
.--
r-
r-
a:
~
[l
20
n
10
0
100
EXP. NO. 3
EXPNO.
80
N •25
2!5
N
r-
60
40
20
.--
r-
n
I
44
2
3
DAYS
FOLLOWING EMERGENCE
EMERGENCE
DAYS FOLLOWING
Number
newly emerged
emerged iujuNumber of newly
venile
chinook salmon
salmon remaining
remaining in
venue fall
fall chinook
observation troughs with increasing
daily age
age after
afteremergence,
emergence, 1970.
1970.
Figure 12.
12.
Figure
Whenever newly
newly emerged
emerged fry were
were
Whenever
taken
from the
the emergence
emergence boxes
boxes and
and
taken from
placed in
the observation
observation troughs,
troughs, they
they
placed
in the
grouped near
the bottom
bottom in aa fright
grouped
near the
huddle.
These newly
newly emerged
emerged fry usualusualhuddle. These
rema ined together
the first
together during
during the
ly remained
few days
days and
and were
were docile.
docile. There
There was
was aa
photo-negative response.
response. In the
the
marked photo-negative
presence ofofbright
represence
bright sunlight,
sunlight, the
the fry
fry rethe shadows
shadows of
the pools
pools or
or
mained in
mained
in the
of the
hid among
among the
the gravel.
gravel. However,
However, in
the
in the
absence of
sun, the
the entire
entire group
group
absence
of bright
bright sun,
usually stationed near the upper
upper end
end
was usually
was
the riffle
riffleorormoved
moved together
together throughthroughof the
the trough.
trough.
out the
Usually by
day, the
tendUsually
by the
the 3rd
3rd day,
the fish tended
spread out,
fed on
on drift,
drift,respondrespond ed to spread
out, fed
light, and
andshowed
showed some
some
ed less
less to strong light,
ed
agonistic
At emergence,
emergence, most
most
agonistic behavior.
behavior. At
fail
fall chinook
chinook salmon
salmon lacked
lacked color
color in
in their
[ 16]
[161
fins,
by the
the 3rd
3rd or
or 4th
4th day
day they
they
fins, but
but by
started developing color patterns of
stream
fish (Stein,
Reimers, and
Hall,
stream fish
(Stein, Reimers,
and Hall,
1972).
Influence
Influence of Moonlight
Several observations
suggested that
observations suggested
moonlight
a depressing
depressing effect
on
moonlight had
had a
effect on
the downstream migration of newly
emerged
This was
was
emergedfry
fry during
during the
the night.
night. This
ddiscovered
iscovered during experiments where
newly
planted in obobnewly emerged
emerged fry
fry were
were planted
servation
durservation troughs
troughsatattwo
two times:
times: 11)) during daylight on the morning after
emergence,
emergence, and
and 2) during
during darkness
darkness at
night shortly
shortly following
following their
theiremergence.
emergence.
In
In most
most cases
cases fish
fish planted
planted during
during the
the
day
stayed in
in the
troughs until
until darkdarkday stayed
the troughs
moved downstream.
downstream. Fish
ness, then moved
planted at
night usually
usually went
went downdownplanted
at night
stream
stream immediately.
immediately. However,
one
However, on
on one
night
moon, the
night during
during full
full moon,
the entire
entire lot of
fish
planted after dark
dark remained
remained in
the
fish planted
in the
trough. The
trough.
next night
night one
one of
of the
The next
troughs
black polyepolyetroughs was
was covered
covered with
with black
thylene
thylene sheeting
sheeting. and
and the
the other
otherexposed
exposed
STAGES
STAGES OF
MOON
•
0
o
()
DARK
DAWN
80
.
()
DARK
FULL
!0NUGHT
MIDNIGHT
DUSK
to
normal night light.
light. In
In the
the moonmoonto the normal
system, 38 remained
remained in the
the trough
trough
light system,
and
downstream, while
in the
the
and two
two went downstream,
while in
darkened trough,
trough, five
five remained
darkened
remained and
and 35
35
went downstream.
downstream.
trap inin Edson
Edson Creek
Creek was
was checked
checked
The
The trap
at
midnight on
on aa few
nights at different
at midnight
few nights
stages
moon to
to substantiate
substantiate the
the
stagesof
of the
the moon
experimental findings
findings (Figure
3). On
On
(Figure 113).
experimental
those
moon, the
the moon
moon
those days
daysprior
prior to
to full moon,
was already
the sky
sky when
when nightfall
nightfall
was
already inin the
came. During
these nights
most fish
fish
During these
nights most
moved
midnight, and
and presumably
presumably
moved after
after midnight,
After full
the moon
moon went
went down.
down . After
after the
moon,
moon, the
the moon
moon did
did not
not come
come up
up until
later in the
evening. On
On these
these nights
nights
the evening.
most
fish moved
moved before
before midnight,
midnight, and
and
most fish
few
the moon
moon was
was up.
up. During the
the
few after the
dark
the moon,
moon, fish
fish were
were captured
captured
dark of the
in
trap throughout
throughout the
the night.
night. VariaVariain the trap
tion in
in the
the distribution
distribution of
of catch
catch may
may reretion
differences in distance
distance that newly
newly
flect differences
emerged fish
traveled downstream
downstream from
emerged
fish traveled
emergence sites.
Based
the preceding
preceding analysis,
analysis, it
Based on
on the
was concluded
concluded that large
large numbers
numbers of
of jujuwas
POST-MIDNIGHT
1131 692
CATCH
60
40
~ 40
0..
ii
20
~
0
1-
!C
20
~
z 20
ILl
PRE-MIDNIGHT
CATCH
()
ffi
40
0..
60
80
E
1125
IC
IS
15
20
APRIL
Figure
25
30
10
5
MAY
13. Period
downstream movement
newly emerged
emerged juvenile
juvenile fall
Period of
of downstream
movementatat night
night of
of newly
chinook salmon
Edson Creek
moonlight, 1970.
1970.
chinook
salmon inin Edson
Creek compared
comparedtoto conditions
conditions of
of moonlight,
[(17]
17 1
venile
chinook salmon
salmon in
in Sixes
Sixes River
River
venile fall chinook
left
the spawning
spawning streams
streams shortly
left the
shortly after
emergence
areas in
emergenceand
and entered
entered other
other areas
the
river for
for rearing.
rearing. AAmuch
much smaller
smaller
the river
number
resided in
in the
the spawning
spawning
number of
of fish resided
streams.
Table
Number of
marked juvenile
juvenile fall
Table 4.
4. Number
of marked
fall
chinook
chinook salmon
salmon recovered
recovered from
from one
one pool
in Edson
Edson Creek
Creek at
atsuccessive
successive sampling,
sampling,
1964.
Total
Number
Number
of
of Fish
Caught
o.,te
Date
Long-Term
Residence
Long-Term Tributary
Tributary Residence
Once
was
Once residence
residenceinin the
the tributaries was
established,
developed agonistic
agonistic
established, the
the fish developed
social
social behavior
behavior (Reimers,
(Reimers, 1968)
1968) and
and the
bright colors of stream fish (Stein,
Reimers,
Some fish rereReimers,and
andHall,
Hall, 1972).
1972). Some
mained and grew in the spawning
streams
summer and
and auaustreams through
through the
the summer
tumn
Unfortunately, no
no estimate
estimate of
tumn.. Unfortunately,
of the
number
residing in
number of
of fish
fish residing
in the tributaries
is
number was
was probprobis available,
available, but
but the number
ably
small considering
considering the
areas inhabitably small
the areas
ed. Only an
ed.
an estimated
estimated 15
1 5toto 20
20 km
km of
tributary streams
streams were
were being
being used.
used. Primary areas
mary
areas for this
this extended
extended stream
stream
rearing
Edson, Dry,
Dry, and
and Crystal
Crystal
rearing were
were Edson,
creeks.
Most of
of these
fish left the
Most
these fish
the tributary
tributary
streams during
during autumn. Some
Some juveniles
streams
were fin
fin marked
with vinyl
were
marked or
or tagged
tagged with
vinyl
thread and pennant tags in Edson
Creekduring
duringautumn
autumn1964.
1964.AA total
total of
Creek
29 fish was
was marked
marked in
in an
an upstream
upstream pool
pool
on
on September
September 16.
16. Progressively
Progressively fewer
marked fish
fish were
marked
were recaptured
recaptured each
each time
time
the pooi
(Table 4)
4).. These
the
pool was
was seined
seined (Table
These
marked fish could
could not
not be
be identified
downstream
the same
downstream because
because the
same mark had
had
been
been used
used in other
other pools.
pools. From
From October
October
23
23 to
to November
November 4, 107
107 fish
fish were
were uniuniquely tagged
quely
tagged along
along the
the stream.
stream. From
From
October 27
27 to
19
October
to November
November 1
12,2, only 19
tagged
fish were
of which
tagged fish
were recovered,
recovered, of
which
nine had
had remained
remained in
in the
the same
same pool.
pool. The
The
remainderofof the
the tagged
fish that were
remainder
tagged fish
were
recaptured were caught downstream
from
from their
their tagging
tagging location.
location. Seining
Seining in
in
the creeks
wasdifficult
difficult during
creeks was
during the
the winter.
ter. Five
Five juveniles were caught
caught on
on JanuJanuary
ary 17,
17, 1965,
1965, but
but none
none could
could be
be caught
caught
on February
February 20,
20, 11965.
965.
September
16
September 16
October
October 22
October
22
October 22
November
November 44
29
24
16
16
5
5
Number
of
Fish
Fish
Marked
Number
Number of
Marked
Fish
Recovered
29
-
-
-
20
12
2
83.0
75
.0
75.0
40.0
Percentoge
centage
Marked
Residence
River
Residenceinin the
the Main River
In
1969 juveniles
juveniles were
were followed
In 1969
followed from
the
spawning tributaries
tributaries as
as they
they moved
moved
the spawning
downstream
and
downstream through
through the
the main
main river and
estuary
ocean . Data
Data on
on
estuary and
and entered
entered the ocean.
catch
seine haul
Dry Creek
Creek and
and
catch per
per seine
haul for Dry
Edson Creek
and
Edsori
Creek were
were combined
combined in
in 1969 and
showed
that for
for
showedaa pattern
pattern similar
similartoto that
Edson
(Figure 14).
14) . The
The
EdsonCreek
Creekinin 1970
1970 (Figure
populations in
the tributaries
tributariesincreased
increased
populations
in the
in
April, peaked
peaked in
in May,
May, and
and declined
declined
in April,
June.
in June.
Peak
Peak abundance
abundance came
came about 11 month
later
river than
than in
in the
later in
in the main
main river
the tributaries.
taries. At the
the time
timewhen
whenpeak
peaknumnumbers
of fish
fish were
found in
in the
bers of
were found
the tributartributaries,
ies, many
many fish were
were moving
moving downstream
downstream
into
the main
main river.
river. The
The population
population in
into the
main river
river began
began increasing
increasing in May,
May,
the main
reached aa peak
reached
peak in
in June,
June, and
and declined
declined in
in
July
(Figure 14).
14) . AAreduction
reductionininpopupopuJuly (Figure
lation by
by early
early to
tomidsummer
midsummer generally
generally
lation
occurred
study.
occurred during
during each
each year
year of
of this study.
Relatively
information isisavailable
available
Relatively little information
to explain
explain this
this reduction,
reduction, but
high tembut high
peratures are
play an
an imporimporperatures
are thought
thought to play
tant role.
role. In
In contrast
contrast to
cool tributo the cool
taries where
where a small
small resident
resident population
population
taries
remained, the
main river
river became
became conconremained,
the main
siderably
siderably warmer
warmer and
and possibly
possibly uninhabituninhabitable along
along much
much of its
its course
course (Figures
(Figures
able
and 3).
2 and
In 1969
1969 periodic
periodic trapping
trapping in
in the
the lowlower main
main river
river occurred
occurred from
to
er
from April
April 99 to
13. Initial catches
catches in April
April and
and
August 13.
indicated that
thatsome
some recently
recentlyemergemergMay indicated
ed
fish moved
moved into
into tidewater
tidewater (Figure
ed fish
[ 18 J
(18]
56
<[
• TRIBUTARIES
(EDSON AND
AND DRY
DRY CREEKS)
CREEKS)
TRIBUTARIES (EDSON
0
o MAIN
(6 KM)
MAIN RIVER
RIVER (6KM)
48
LOWERESTUARY,(STA
ESTUARY• (STA . 1-12)
1-12)
48 00LOWER
b
1-
44
52
52
....11
4
I.-
/,""'- ....,,
I
'S
I/I
lL
1I
00 40
w
(!)
~ 36
z :26
w 32
...
0
0:
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D..
I
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w
I
28
(f)
<[
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16
Ill
I
,'
•
,'
'
I
/
w 12
:>
w
a::
•
I
I
I
I
<[
~
....1
I
I
20
z
I
I
w 24
0
:i0
8
4
0
0
\
S
I/
\ .. ·····. "'•,.
I
••••\
I
•• '
•.
I o:
\
,.,--·
,'
'
,' .:
...
.
,'•• t)
/o•
•
•
0
APRIL
MAY
JULY
JUNE
0
AUG.
AUG.
0
0
SEPT.
SEPT
chinook salmon
Figure 14.
14. Estimated
Estimated abundance
juvenile fall chinook
salmon in tribtstaries
Figure
abundance of juvenile
tributaries (catch
per
seine haul
I, main
main river
river (catch
(catch pperr seine
seine haul
I , and
and estuary
estuary (population
(population esesper seine
haul),
haul),
timates
Sixes River,
River, 1969.
1969.
timates)I of Sixes
1 5) . The
The number
number of
of trapped
trapped fish
fish reachreach15).
ed
a peak
peak in
in late
late June
June and
and rapidly
rapidly dedeed a
clined
(Table 5).
clined in
in July
July (Table
Table 5.
5. Catch
Catch per
trap-night of juvenile
juvenile
per trap-night
Table
fall
fall chinook
chinook salmon
salmon in
in lower
lowerSixes
Sixes River,
River,
1969®.
1969CD.
Catch
Per
catch Per
Trap
Trap Night
Dote
Date
April
May
June
9
10
24
29
30
7
8
22
23
29
11
11
12
12
65
49
91
13
9
48
67
29
26
35
252
183
Catch Per
Per
Trap Night
Night
Trap
Dote
Date
June
18
19
20
26
27
10
July
11
18
24
31
31
August 13
August13
ii
110
276
321
414
616
41
21
24
14
14
5
2
of 7.0
7.0 to
to 8.0
8.0 cm,
em, based
based on
on the
the size
size of
of
trapping
migrant and
and resident
resident fish
fish at the trapping
location (Figure
(Figure 15).
1 5). Fish
Fish caught
caught in the
the
location
assumed to
trap were assumed
to be
be migrants,
migrants, while
fish caught
caught farther
farther upstream
upstream with
the
fish
with the
seine
seine were
were assumed
assumedtoto be
be residents.
residents. MiMigrants were
were slightly
slightly smaller
smaller than
than the
the
grants
residents.
juveniles reresidents. The
The number
number of juveniles
residing
siding in the
the main
main river
river before
before being
being rerecruited to the estuary
was probably
probably
estuary was
large, considering
considering the large
large rearing
rearing pools
pools
large,
in
main river and
and that juveniles
juveniles were
in the main
initially distributed
distributed along
along 30-35
initially
30-35 km
km of
river.
river.
Residence
Estuary
Residence in
in the Estuary
rearing for
time in
in the
the main
main
After rearing
for aa time
CD On
On April
April 9,
9, 10,
10, 29
29and
and30,
30,only
onlyone
one trap
trapfished
fished near
near
®
the
the south
south shore.
shore.On
OnApril
April 24
24 and
and May
May 7-29,
7-29, three
three traps
traps
were
trapping was
was incomplete.
incomplete. From
were operated,
operated, but
but trapping
June
were fished
fished extending
June 11-August
11 -August 13,
13, three
three traps were
across the entire
entire stream.
stream.
across
During
their residence
residence in the
the main
main
During their
river,
fish grew
grew to
toan
anaverage
average size
size
river, the fish
river or tributaries,
tributaries, most
most juveniles
juveniles from
from
river
any
brood moved
moved downstream
the esesany brood
downstream to
to the
tuary (Figure
14) . Peak
Peak abundance
abundance in
(Figure 14).
the
tributaries came
came about
the middle
middle
the tributaries
about the
of May,
May, while
while peak
peak abundance
abundance in
in the
the
main river
river came
came about
about the
the middle
middle of
main
June.
'9]
£I9 1
12.0
N
0
I
ElSEINED
SEINED
11.0
*MEAN
so·
RANGE
TRAPPED
6
10.0
l5C)
50
413
9.0
118
11$
zz
I
345
321
321
35
~ 8 .0
6zz
1&.1
Ui
.J
-j
1155
7. 0
~ ·~i
4
918522
~
15ILU-
NH
106
66224
6.0
6.0H
I
5.0
5.°L
4 .0
114
114
APR IL
APRIL
40
14
B
e
ij
I
M
LU
I
I'I
I
MAY
MAV
JUNE
JULV
JULY
AUG.
SEPT.
Length of juvenile fall chinook
Figure 15.
lowerSixes
Sixes River,
River, 1969.
1969.
15. Length
chinook salmon
salmon captured
captured in lower
Fish caught
seine were
resident. Trapped
Trapped fish
fish were
were capcapFish
caughtwith
with aa seine
were assumed
assumedtoto be
be resident.
tured
moving downstream
downstream and
assumed to
migrants.
tured moving
and were assumed
to be migrants.
In
first juveniles
juveniles entered
entered the
In 1969 the first
estuary
in early
estuary in
early spring,
spring, but there
there apappearedtoto be
be few
few fish
fish in the
the lower
lower bay
bay
peared
before mid-April. After the estuary
late March
arid early
flooded
early April,
flooded in
in late
March and
many juveniles
juveniles were
were seined
seinedon
on April
April 77
many
and
the head
of tidewater, boat
near the
head of
boat
and 14 near
landing, and
and stations
stations 10
landing,
10 and
and 6.
6. Most
fish appeared
to be
in shallow
shallow water
water
fish
appeared to
be in
near shore
shore and
and were
were associated
associatedwith
with logs
near
logs
and debris.
debris.
Relatively few fish were
were captured
captured near
near
Relatively
the
river mouth
mouth (stations
(stations 1 and
from
the river
and 3)
3) from
March
The first
March to
to May
May (Table
(Table6).
6). The
first juveniles captured
on April
April
veniles
captured were
were three
three on
21
29. Juveniles had
had
21 and
and four
four on
on April 29.
been captured
capturedat
at upper
upper stations
stations in
in the
been
estuary
month earlier.
earlier. On
On May
May
estuary about 11 month
1
3
and
14,
the
Oneida
Lake
trap
was
13 and 14,
Oneida Lake trap was
fished
station 3.
3. This
trapping and
and
This trapping
fished at
at station
seven
stations 1 and
seven seine
seine hauls
hauls at stations
and 33
caught
1 3 fish
fish compared
to 383
caught only
only 13
compared to
383
fish caught
fish
caught with 27
27 seine
seine hauls
hauls at stastations 44 to 12.
1 2. Later
the summer
summer the
the
tions
Later in the
trap
from 200
200 to 11,000
net caught
caught from
trap net
,000 fish
1
per
at stations
stations 11 and
and 3.
3. Based
Based on
per night at
these observations,
was concluded
these
observations, itit was
concluded that
few
fish moved
moved directly
the mouth
mouth
few fish
directly to the
the river
river or
or into
intothe
theocean.
ocean. By
By early
early
of the
June, juveniles
juveniles were
captured at all
all stastaJune,
were captured
tions in the
the estuary
estuary and
and were
were also
also obobtions
estuary and
and not
not
served throughout
served
throughout the
the estuary
just near
near the
the shore.
shore.
Table
6. Total
Total number
number of
of juvenile fall
Table 6.
chinook salmon
salmon seined
seined from
from Sixes
Sixes River
River
chinook
estuary from
1969.
estuary
from March
March to
to May 1969.
Stationss
sampling
Numberof
Station·
Sampling
Number of
Hauls
Period
and
to 122
_P
_e_ri_od_ __ Seine
s_e_in_e_H_
a_
u l_s _ _IT_a_
nd
_ 33 _ __ 4
4_to_T_
13
March
13
0
22
March
35
April
38
7
357
7
May
28
86
596
- - -- - - - - - - - -- - - -Change
Abundance
Change In
In Abundance
The abundance
abundanceof
of juveniles
juveniles in
in the
the lower Sixes
Sixes River
River estuary
estuary was
was estimated
estimated
times between
between May
May 12
12 and
and SeptemSeptemsix times
ber
1969 (Figure
(Figure 16).
16) . Athough
Athough juber 23,
23, 1969
veniles
estuary durveniles were
were present
present in
in the estuary
[ 20 J
(20)
ing April and
and May,
May, the
the population
population was
was
ing
small.
May and
and early
early
small. However,
However, by
by late
late May
June,
the population
population had
had greatly
greatly inJune, the
about 145,000
145,000
creased. AA population
creased.
population of about
fish
was reached
reached in
late July and
and early
early
fish was
in late
August. Subsequently, the
the population
population
August.
..
THOUSANDS OF
OF FISH
FISH
THOUSANDS
200r--- - - -- - - -- - - -- -- -- -- -- -- - - -- - ,
200
95% CONFIDENCE
CONFIDENCE LIMITS
LIMITS
95%
POINT
ESTIMATE
POINT ESTIMATE
\
150
50
low of about
about 25,000
25,000 fish
fish
declined
declined to
to aa low
in late
late September.
September.
Many
may have
have been
been moving
moving to
to
Many fish may
the ocean
ocean during
period of
of high
the
during the
the period
density in the
estuary. In
population
the estuary.
population density
1966
1966 during
during June,
June, as
as many
many as
as 300
300 ju- 100
00
captured in
veniles
veniles per
per seine
seine haul
haul were
were captured
the outflow
outflow channel
channel and
and ocean
ocean surf
the
within 100
100 m
m to
to the
the north
north and
and south
south of
later in
in summer
summer
Sixes
River. However,
However, later
Sixes River.
only a
a few fish
fish were
were captured
captured in
in these
these
only
50
localities.
localities. Juveniles captured in the
ocean surf
channel were the
the
ocean
surf and
and outflow
outflow channel
same
juveniles in
the esessamesize
size as
as the
the juveniles
in the
Oregon ,
tuary (Fish Commission of Oregon,
1968)
1968)..
Another measure
measure of the
the change
change in
Another
SEPTBIBER
AUGUST
JULY
JUNE
MAY
population size
size in the
population
the estuary
estuary was
was data
data
on
per seine
seine haul
the 38-rn
38-m
on catch
catch per
haul with
with the
seine.
Catch per seine
seine haul
haul of juveniles
juveniles Figure
seine. Catch
16. Estimated
of juvenile
Figure 16.
Estimated number
number of
juvenile fall
for the
the lower
lower estuary
estuary during
during 1969
1969 was
was
salmon in lower
lower Sixes
Sixes River
River eseschinook salmon
chinook
tuary,
1969.
tuary, 1969.
variable but
showed aa pattern
variable
but showed
pattern similar
similar to
the
population estimates
estimates (Figure 17).
17 ).
the population
Comparison
Comparisonofof data
data on
on catch
catch per
per seine
seine near
near the
river mouth
mouth where
where they could
could
the river
haul
the upper
upper and
and lower
lower parts
parts of be
haul for
for the
easily.
be captured easily.
the estuary
estuary suggests
suggests that
peak abunabunthe
that peak
Two
population estimates
estimates and
Two population
and their
dance
weeks earlier
earlier associated
dance came
cameabout
about55 to
to 66 weeks
associated catch
catch per
per seine
seine haul obtained
obtained
at
the head
head of tidewater
tidewater than
than near
near the
the in
at the
Sixes River
1967 (Fish
(Fish
in Sixes
River estuary
estuary during
during 1967
river
mouth.
river mouth.
Commission of Oregon, 1968) were
There
was a
a close
close relationship
relationship bebe- plotted
There was
fit the
plotted in
in Figure
Figure 18.
18. The
The data
data fit
the
tween catch
catch per
per seine
seine haul
haul and
and the
the line
tween
well, suggesting
that in
line reasonably
reasonably well,
suggesting that
in
population
estimates of
of juveniles
juveniles in
in the
population estimates
the any
data on
on catch
catch per
per seine
seine
any year
year where
where data
lower
8) . The
The first five
five haul
lower bay
bay (Figure
(Figure118).
haul are
are available,
available, population
population estimates
estimates
population estimates
estimates and
and their correpopulation
corre - may
may be obtained.
obta ined .
sponding catch
catch per
per seine
seine haul
haul fell
fell on
on aa
sponding
of Juveniles
Juveniles
The last
straight line. The
last point
point deviated
deviated Growth of
In
1969
the lengths
lengths of
of 8,421
8,421 fish
1969
the
This probably
from
the line. This
probably resulted
resulted
from the
measured
in
lower
estuary.
The
were
measured
in
the
lower
estuary.
The
from variability
variability in
in the
the catch
catch per
perseine
seine
from
average
weekly
sample
size
was
290
average
weekly
sample
size
was
haul rather
rather than
than an
an error
error in the
the populapopulahaul
The first fish
fish measured
measured on
on March
March
estimate. By
By autumn
autumn these
these large,
large, fish. The
tion estimate.
were all recently
recently emerged.
emerged. The
The averaver8 were
tended to
to congregate
congregate 118
mobile
juveniles tended
mobile juveniles
[ 21 1]
[21
320 ~---------------------------------------------------,
S
• LOWER
ESTUARY (STA.
(STA. 1-12)
1-12)
•
LOWER ESTUARY
300
300
o0 UPPER
ESTUARY (ORCHARD
(ORCHARD HOLE)
HOLE)
UPPER ESTUARY
•
280
280-
•
260
240
220
200
~
0 200
U.
l!::
180
u 180
"-1
w
......
:r
I 160
60
~ 140
••
(.)
120
100
•
·.·.
o:
80
60
··'!) ••
40
20
•
....
•
•
••••••••••
0
......0
•
APRIL
Jut£
JUNE
MAY
JULY
JULY
AUG.
SEPT.
OCT.
OCT.
Figure 17.
Figure
17. Catch
Catch per
juvenile fall
fallchinook
chinooksalmon
salmon collected
collected with
with aa 38-rn
38-m
per seine
seine haul
haul of uvenile
beach seine
seine in Sixes
Sixes River
River estuary,
beach
estuary, 1969.
x 200
X200
(/)
0)
~
1967
00 967
1969
•'1969
0
0
U-
~
0
(/)
C,)
a )50
z 150
ct
4
(/)
Ci)
;:::)
0
0
....=I-X
-S.
~100
ILl
w
~
z
0
NI
C',
~
..1
50
00
;:::)
•
a.
0
a.
I
50
I
100
100
150
200
I
250
300
350
CATCH/EFFORT
GATGH/ EFFORT
Figure
8. Relationship
Figure 118.
38-m seine
seine and
and
Relationshipbetween
betweenaverage
averagecatch
catchper
per seine
seine haul
haul with
with the
the 38-rn
the estimated
populationof
of juvenile
juvenile fall
fall chinook
the
estimated population
chinook salmon
salmon in
in lower
lower Sixes
Sixes River
River esestuary,
1969.
tuary, 1967 and 1969.
[[22]
22]
age
age increase
increaseinin length
length during
during April was
was
small,
increase of the
the upupsmall, although
although the increase
per
range suggests
was
per range
suggeststhat
that some
some growth
growth was
occurring (Figure 19)
late April
April
19).. By
By late
and
rate of growth
growth
and throughout
throughout May,
May, the
the rate
in
the lower
lower estuary
estuary was
was rapid.
rapid. Average
Average
in the
length increased
increased from
4.8 cm
em on
on
fork
fork length
from 4.8
April
29 to
to 7.9
7.9 cm
em on
on June
June 2.
2. Dur.ing
April 29
During
June,
and August,
August, there
there was
was only
only
June, July,
July, and
aa slight increase
increase in
in the
the average
average length.
length.
From
mid-November, the
the
From late
late August
August to
to mid-November,
average
increased from
8. 5 to
average length
length increased
from 8.5
12.5
em.
12.5 cm.
During
the period
period of
of reduced
reduced growth
growth
During the
in
the lower
lower estuary,
estuary, the
the upper
upper range
range
in the
and entire
entire distribution of fish
and
fish size
size closeclosely
followed the
the pattern
pattern of the
the mean.
mean. As
ly followed
growth increased
increased in late
summer and
and
late summer
autumn,
the upper
upper range
range increased
increased at
autumn, the
at
the same
same accelerated
accelerated rate
rate as
as the
the mean,
mean,
and
the entire
entire size
size distribution
distribution shifted
shifted
and the
upward.
Growth
marked fish generally
generally folGrowth of marked
lowed
same pattern
as the unmarkunmarklowed the
the same
pattern as
ed fish
fish but with
ed
with slightly
slightlymore
more variation.
variation.
direct comparison
comparison of
of the
theaverage
average size
size
A direct
of
the marked
marked and
and unmarked
unmarked fish
fish sugsugof the
gests
rates (Figure
(Figure
gests they
they grew
grew at
at similar
similar rates
The first group
group of
of marked
marked fish
fish
20). The
mid-May to
to early
grew rapidly from
from mid-May
June, although
as the
the ununJune,
although not
not as
as fast
fast as
marked fish.
fish. Marked
Marked fish in
in the
thesecond
second
marked
and third groups
groups grew
from early
early
and
grew little from
June to
to mid-August.
mid-August. However,
However, these
these
June
marked
marked groups
groups did
did show
show signs
signs of
of slightly
improved growth
being at
at large
large
iy improved
growth after being
month.. Marked
Marked fish
fish in the
about 1 month
fourth
group grew
grew slowly
late July
July
fourth group
slowly from
from late
end of
Then their growth
growth
to the end
of August.
August. Then
showed
same increase
increase as
as the
the ununshowed the
the same
September and
and
marked fish. Through
Through September
October
growth followed
followed closely
closely
October their
their growth
the accelerated
accelerated rate
the unmarked
unmarked
the
rate of the
fish
Marked fish
the fifth
fifth and
and sixth
sixth
fish.. Marked
fish in
in the
groups
the same
same rate
rate
groups grew
grew rapidly
rapidly at
at the
as
unmarked fish.
fish.
as the unmarked
1
Terminal Population
Terminal
By
remainBy autumn
autumn relatively
relatively few
few fish remained
These fish
fish
ed in
in the
the estuary
estuary (Figure
(Figure 18)
18).. These
16.0
16.0
15.0
15.0
t··~
MEAN
14.0
SD
so
RANGE
13.0
13.0
~ 12.0
12.0
;!!:; 11.0
11.0
x
%
t;
'i:5
10.0
1o.o
zz
9.0
~ 9.0
~
a: 8.0
!r
7.0
6.0
5.0
4.0
4.0
3.0
3.0
... ~ '
APRIL
MAY
JUNE
JUNE
JULY
AUG.
AUG.
SEPT.
SEPT
OCT.
OCT
NOV.
NOV.
Figure
Figure 19.
19. Length
Length of
juvenile fall chinook
chinook salmon
salmon seined
seined in
in lower
lower Sixes
Sixes River
River estuary
estuary
of juvenile
(stations 1-12),
1-12), 1969. Sample
Sample size
size averaged
averaged 290 and ranged
ranged from
from 32 to 731.
731.
[ 23]
(23]
(5.0
15~r------------------------------------------------------------,
8,421)
UNMARKED (N
-------- UNMARKED
(N= 8,421)
14.0
(4.0
MARKED
(N = 2,077)
MARKED (N2,077)
13.0
(3.0
12.0
(2.0
~11.0
3!:: 10.0
3:
t;
z
I-
9.0
9.0
2
-J
~
88.0
.0
¥
a:
U-
/
~------
uJ
~
~--~-_.,,/
,
, ,..
/
7.0
7.0
66.0
.0
5.0
FJ
4 .0
4.0
----------""
JULY
JUNE
AUGUST
JUNE
SEPTEMBER OCTOBER
OCTOBER
SEPTEMBER
Figure
Average length of
of marked
marked and
and unmarked
unmarked juvenile fall chinook
chinook salmon
salmon seined
seined in
Figure 20.
20. Average
in
Sixes River
River estuary,
estuary, 1969.
1969. Lines
Lines for
each group
group were
were fitted by
byinspection
inspection
lower Sixes
for each
fish at
at each
each date.
date.
through
through the
the average
average length
length of
of fish
APRIL
MAY
were large
large (Figure
(Figure 19)
19) and
and appeared
appeared to
to
were
excellent condition.
be in excellent
condition. After the
autumn rains,
autumn
rains, the estuary
estuary changed
changed from
aa saline
saline to
to aa fresh-water
fresh-water environment.
environment.
At this
this time
time most
most of
of the
thefish
fishapparentapparently emigrated
emigrated to
to the
the ocean.
ocean.
Yearling Migrants
During the
During
the winter and
and spring
spring of
of each
each
year,
only a
year, only
a. few
few yearlings
yearlings were
were collectcollected
ed in the
the main
main river
river and
and in
in the
theestuary.
estuary.
The
The total number
number captured
captured in
in each
each year
year
ranged
ranged from 11 to 63. No
Noprecise
precise record
record
of the
the number
number of
of seine
seine hauls
hauls was
was kept,
but the effort
effort was
was extensive.
extensive. The
The total
total
number captured suggests
that yearlings
number
suggests that
yearlings
were scarce.
These fish
fish probably
scarce. These
probably origioriginated from
from the
the long-term
long-term residents
residents in
in
nated
the spawning
spawning streams.
streams. In the
the winter
winter oof
1965,
1965, a
a few yearlings
yearlings were
were found in
in EdEdson Creek.
In several
several years,
years, yearlings
yearlings
son
Creek. In
were
found just below
were also
also found
below Dry
Dry Creek
Creek
the main
main river.
river. The
Thesize
size of
ofyearlings
yearlings
in the
seemed
continuation of growth
growth
seemedtoto be
be aa continuation
of juveniles
juveniles from
from the
the tribuary
tribuarystreams
streams
(Figure 21)
21 ) rather
rather than
than of
of extended
extended
(Figure
residents
the estuary.
estuary. Yearlings
residents from
from the
reached
reacheda asize
sizeinin June
June similar
similar to
to that
of juveniles
in the
of
juveniles that
that were
were present
present in
the
estuary
preceding autumn
beestuary the
the preceding
autumn just
just bethe ocean.
ocean.
fore
migration to
to the
fore migration
Studies
Scale Studies
Now that
that aa general
general picture
picture of
the
Now
of the
length
length of residence
residence of the
the juveniles
juveniles has
has
been
need remains
remains to
been developed,
developed,the
the need
determine the
determine
the contribution
contribution of various
various
juvenile life histories to returning
spawners.
spawners.
Types of Life
Life Histories
Histories
Types
For the
the purpose
purpose of
of discussion,
discussion, five
five
For
major
histories were
were arbiarbi major types
types of
of life histories
[ 24
24]J
1!5.0
15.0
14.0
14.0
13.0
3.0
• 1963 BROOO
0 1964 9ROOO
.6.
196~ BROOD
•
1967 BROOD
X 1968 BROOD
12.0
2.0
0
1969 BROOO
l
RANGE
MEAN
~11.0
011.0
zz
/
6z
I
/
/
/'
/
-10.0
l0.0
~
'
I
/
/
__
9.0
"'- 8.0
8.0
Ui
. /I
I
/
.J
lC
~
0 7.0
IL
LI.
6.0
6.0
5.0
5.0
UNOERYEARLINGS
4.0
4.0
APR
APR.
MAY
JUN..
JUN
JUL.
JUL.
AUG.
AUG
SEPT.
SEPT
OCT.
OCT
NOV.
NOV
YEARLINGS
DEC.
DEC
JAN.
JAN
FEB.
FEB
MAR.
MAR.
APR.
APR
MAY
JUN.
JP
Figure 21. Length
Length of
of juvenile
Figure
fuvenile fall chinook
salmon seined
seined as
as underyearlings
underyearlings in
in Edson
Edson
chinook salmon
Creek and
from
by
Creek
and as
as yearlings
yearlingsinin Sixes
SixesRiver
Riverestuary
estuary
from1964
1964toto1970
1970(line
(line fitted
fitted by
inspection).
inspection). Sample
Sample size
size averaged
averaged 45
45 and ranged
ranged from
from 11 to
338. The
The dotted
dotted line
line
to 338.
represents the
average size
size of
of underyearlings
underyearlings in
in Sixes
Sixes River
River estuary
estuary in
represents
the change
change in
in average
1969.
defined from
from the
the study
study of
of juvenjuventrarily defined
iles (Table
(Table 7). Only
Only sketchy
sketchy informainformation is
on the
is available
available on
the relative
relative number
number
tion
of juveniles
juveniles from
from any
any brood
brood that
that residresided in different
areas of
the river
river or
or
different areas
of the
migrated
the ocean
ocean at
at various
various times
times
migrated to
to the
to be
to
be classified
classified into
one of
the five
five
into one
of the
types of
of life
life histories.
histories. Few
fish were
were
types
Few fish
captured
the estuary
estuary in
in early
early spring
spring
captured in
in the
and even
even fewer
fewer atat the
and
the mouth
mouth of the
the
river. The
The extent
extent that
that these
these juveniles
juveniles
entered
fish
entered the
the ocean
ocean to
to become
becometype-1
type-i fish
is unknown,
unknown, but the
the number
number was
was probprobis
ably small.
small. Most
juveniles probably
probably bebeMost juveniles
came
fish, based
based on
on the
the curve
curve
came type-2
type-2 fish,
of population
population abundance
abundance derived
the
derived for the
estuary (Figure
During the
the time of
estuary
(Figure 16).
16). During
large
abundance and
and reduced
reduced
large population abundance
the estuary
estuary
growth,
many juveniles
growth, many
juveniles left the
and were
and
were captured
captured in the
the ocean
ocean surf.
surf.
Presumably,
also present
present bebePresumably, they
they were
were also
the surf
surf zone
zone in
in the
theopen
openocean.
ocean.
yond the
yond
Compared
Comparedtoto the
the number
number of
of type-2
type-2 fish,
fewer
juveniles remained
remained in the
the estuary
estuary
fewer juveniles
until late
late summer
summer and
and autumn
autumn to
to experexperience
and be
be classified
classified
ience improved
improved growth and
as
type-3 fish.
as type-3
fish . The
The differences
differences between
between
type-2
type-3 fish
fish were
were less
less disdistype-2 and
and type-3
tinct than
than among
among other
other types.
types. But
But the
the
classification was
was preserved
preserved because
because the
period of reduced
reduced growth
growth in the esperiod
eslong enough
enough that many
many type-2
type-2
was long
tuary was
fish
probably would
would have
have entered
entered the
the
fish probably
ocean without
forming typical
typical estuarine
estuarine
ocean
without forming
circuli
circul i on
on their
theirscales.
scales. After growth
growth of
of
juveniles in
the estuary
estuary improved,
improved, fish
fish
juveniles
in the
continued to
enter the
the ocean.
ocean . These
continued
to enter
juveniles were
were classified
classified as
juveniles
as type-3
type-3 fish,
since
probably would
wouldhave
havepossespossessince they probably
sed typical estuarine circuli on their
scales. The
The number
number of fish
fish remaining
remaining
[(25]
25]
in the
the tributaries
tributaries until
until autumn
autumn to
to be
be
in
come
juveniles was
was probably
probably income type-4
type-4 juveniles
termediate between the number of
the combined
combined total
types
type-3
and the
type-3 and
total of types
and 5.
5. Yearling
5) were
were
1I and
Yearling fish (type
(type 5)
captured each
each spring,
spring, but
but the
captured
the number
number
was
always small.
small. The
The suggested
suggested relarelawas always
order of
ofdecreasing
decreasing abundance
abundance for
for
tive order
the different
different types
types of
juvenile life hishisthe
of juvenile
4, 5,
5, and
and 1.
1.
tories is
tories
is 2,
2, 3, 4,
Table
Table 7. Description
Description of
of the
the major
major types
types of
life histories of juvenile fall chinook
salmon
Sixes River,
River, Oregon.
Oregon.
salmon in Sixes
Type
Description
Emergent fry
move directy
directy downstream
downstream and
into
Emergent
fry move
and into
the ocean
the
ocean within
within a
o few
few weeks.
weeks.
2
Juveniles rear
Juveniles
rearininthe
the main
main river
river or
or remain
remain inin tri
tri-butaries
early summer,
summer, then
the
butaries until early
then emigrate
emigrate into the
estuary
a short
short period
period of rearing
rearing and
and enter
enter the
estuory for
for a
ocean
improved growth
late summer.
summer.
ocean before
before the
the improved
growth in late
33
Juveniles rear
main river
river or
or tributaries
tributaries until
until
Juveniles
rearinin the
the main
early 5ummer,
;ummer, then
estuary for
for
early
then emigrate
emigrate into
into the estuary
extended
the period
period of
ofimproved
improved
extended rearing
rearing during
during the
growth in late
late summer
summer and
enter the
the ocean
ocean in
in
and enter
autumn.
'I
4
Juveniles remain
streams (or
lor rarely
rarely
Juveniles
remain inin the
the tributary streams
the main
main river)
river) until
autumn rains,
rains, then
then emiemiuntil autumn
in the
grate
to the
the ocean.
ocean.
grate to
55
Juveniles
remain in
in the tributary
Juveniles remain
tributary streams
streams (Or
lor rarely
rarely
in
the main
main river)
river) through
through the
the summer,
summer, rear
rear in
in the
Sixes River
the following
following spring,
spring, and
and enter
enter
Sixes
River until
until the
ocean as
as yearlings.
yearlings.
the oceon
Scale
Types
Scale Characteristics
Characteristics of
of Life History Types
attempt was
was made
made to
An attempt
to differentiate
scale
from the
the various
various
scale patterns
patternsof
of fish
fish from
by comparing
comparing
types of life histories by
and spawners.
spawners. FundaFundascales
scales of
of juveniles and
mental to the
the scale
scale analysis
analysis was
was the
the
mental
ability to distinguish among circuli
formed in fresh water, estuary, and
ocean. Differences in conditions.
conditions, for
growth
fish in
these three
three environenvironin these
growth of
of fish
ments were
assumed to
on
ments
were assumed
to be
be reflected on
scales. Slow
Slow growth
growth was
was expected
expected
their scales.
narrow circuli
by narrow
to be represented by
spacing and
spacing
and rapid
rapid growth
growth by
by wide
wide circuli
rcul i
circuli
spacing.
Therefore, estuarine ci
spacing.
intermediate in
in spacspacshould have
have been
been intermediate
should
ing
fresh water
ing between
between those
those formed
formed in
in fresh
and the
the ocean.
ocean .
and
the scale
scale analysis
analysis was
was conconMost
Most of the
fined
1965-brood fish,
fish, since
since that was
was
fined to 1965-brood
the
only brood
brood with
with complete
complete returns
returns
the only
Since most
most of
of the
of spawners.
spawners. Since
the data
data
on
length of residence
residence and
and growth
growth are
are
on length
the 1968
1968 brood,
brood, differences
differences between
between
for the
the years
years need
need to
to be
be resolved.
resolved. Differthe
ences in the
the length
length of
ofresidence
residence and
and
juveniles in
in fresh
fresh water
water among
among
growth of juveniles
years studied
studied appeared
appeared to
be
all the
the years
to be
minimal, except
except for
for extended
extended residence
residence
minimal,
and larger
larger size
size of
of juveniles
juveniles in
in 1964.
and
• was
Length
residence in
the estuthy
estua'ty
was
Length of
of residence
in the
among all the years studied,
similar
similar among
although
a I thoughpopulation
population abundance
abundance probably
varied
Possibly as
as aa result
result of
differvaried.. Possibly
of different population
population levels,
levels, there
there appeared
appeared to
be considerable
considerable differences
differences in
in growth
growth
be
of juveniles
juveniles in
in the
theestuary
estuary among
among the
the
years.
were small
small
years. Differences
Differences in
in growth were
between 1966
and 11969
probably
966 and
969 and
and probably
preclude aa direct
direct comparison
comparison bebedo not preclude
do
tween
scale patterns
patterns of 1965-brood
1965-brood
tween the scale
fish and our detailed knowledge of
growth and
and length of residence
residence of 19681968brood juveniles.
juveniles. A period
period of
of reduced
reduced
brood
growth was
was also
also observed
observed in
(Fish
in 1966 (Fish
Oregon, 1970).
I 970). in
In 1966
1966
Commission
Commission of
of Oregon,
and 1969
and
1969 the
the size
size of
of juveniles
juveniles during
during
the period
period of reduced
reduced growth
growth was
was alalthe
most identical
In 1969
1969
most
identical (8.0
(8.0 to
to 8.5
8.5 em).
cm). In
the period of reduced
reduced growth
growth lasted
about
months, but
but during
during 1966
1966 it
about 33 months,
lasted only about 2 months. The
length
this period
period appeared
appeared to
diclength of
of this
to dictate the
tate
the final
final size
the juveniles
juveniles in
in
size of
of the
autumn, as
growth in
in the
the
autumn,
as the
the rates
rates of
of growth
years were
were similar
similar once
once growth
growth imim2 years
I 966 they
they reached
reached a length
length
proved.
proved. In 1966
of
about 12.5
12.5 cm
em near
near the
the middle
middle of
of
of about
October,
1969 they
they were
were about
about
October, while
while in 1969
l1 cm
em shorter.
shorter.
Juveniles from
I 965 brood
brood were
were
Juveniles
from the
the 1965
collected
scale analysis
folcollected for
for scale
analysisatat the
the foltimes and
and areas
areas in
in Sixes
Sixes River:
River:
lowing
lowing times
I1)) trapped
trapped moving
moving downstream
downstream in
the
in the
[ 26 J
[26]
lower
from May
May 20
20 to
to June
June 13;
lower river
river from
1 3;
seined in
in the
the estuary
estuary from
from May
May 26
26
2)
2) seined
to
June 26
26 (these
(these fish
fishwere
wereassumed
assumed
to June
to
be recently
recently recruited
recruited to the
the estuary,
estuary,
to be
since
population was
was rapidly
rapidly increasincreassince the population
ing);
ing) ; 3) seined from tributaries on
September
seined from the
the estuary
estuary
September 6;
6; 4)
4) seined
on
October 6; and
and 5)
5) seined
seined as
as yearlings
yearlings
on October
during
May and June
June (because
(because of aa lack
lack
during May
the 1965
1965 brood,
brood, fish
fish
yearlings from
of yearlings
from the
1967 brood
brood were
were used).
used). Availfrom
from the 1967
able samples
samples from
each area
able
from each
area were
were stratified
by date
date and
and size
size of fish.
fish.
fied by
Comparative
made of averaverComparative plots were made
ofscales
scales
age
spacing for aa series
series of
age circuli spacing
to
examine differences
differences among
among freshfreshto examine
oceanic circuli
water, estuarine, and oceanic
In part
part one
one of
of Figure
Figure 22
22
(Figure 22)
(Figure
22).. In
are the measurements for juveniles
collected at four key locations and
times. All of
times.
of these
these measurements
measurements of
were small
small and
and
average
spacing were
average circuli
circuli spacing
known to
to have
have been
been produced
produced in fresh
fresh
known
water.
In
In part
part two
two ofofFigure
Figure22
22are
arescales
scales
the estuary
estuary in
in
from
juveniles seined
from juveniles
seined inin the
autumn.
autumn . These
These fish possessed circuli
that appeared
appeared to
be of
of two
two distinct
distinct
to be
spacings. The boundary
boundary between
between these
these
spacings.
zones
circuli was
was abrupt.
abrupt. Because
zones of
of circuli
these
estuary in
in
these fish
fish were
were captured
captured in the estuary
their background
background could have
have inautumn, their
both freshfreshvolved varying
volved
varying amounts
amounts of
of both
and estuarine
mawater and
estuarine growth.
growth. The
The two mazones on
the scales
scales were
jor zones
on the
were arbitrarily
water and
and estuarine
estuarine when
when
called fresh
fresh water
called
plotted. The zone classified as
as fresh
fresh water
water
had measurements of average circuli
circuli spacspacthat were
were midway
midwayamong
among measuremeasureing
ing that
ments
on the
the four
ments on
four groups
groups of
of juveniles
juveniles
known
known to be
be from fresh
fresh water.
water. The
The other
other
zone
zone had
had measurements
measurements of
of average
average circuli
circuli
were larger
larger and
and therefore
therefore
spacing
spacing that
that were
must
have been
been formed
the estuary.
estuary.
must have
formed in the
The scales
scales from
juveniles captured
captured in
The
from juveniles
the
estuary in autumn
autumn had
had an
an additional
additional
the estuary
feature that needs description. If
growth
juveniles in
in the
the estuary
estuary was
was
growth of juveniles
0
MM AT
AT 98X
96X
WIDTH IN
WIDTH
IN MM
N
-
"'
...
SPRING
SPRING
AUTUMN
---- ±
--+-
ARLINGS
jt'EARLINGS
.!>
"'
tji TRAPPED
TRAPPED IN
IN RIVER
RIVER
S
gj
r
IN ESTUARY
ESTUARY
SEINED IN
m
U,
:ll SEINED
SEINED IN
IN TRIBUTARIES
TRIBUTARIES
SEINED IN ESTUARY
ESTUARY
SEINED
r
WA~i:~
-+--~
Aq'
i----
ESTUARINE -
ESTUARINE - - - - -
z
F
~
'i
U,
Cp
WATER ----~
F~if~R
FRESF4
ESTUARINE _
ESTUARINE
_
l>
"'"'
in
,._,.__._ ~
CD
li:
OCEANIC
------ll:
''DC
~IrrR
WATER ---,.__.-~
ESTUARIrE
ESTUARINE
OCEANIC __.,____
OCEANIC
~ltsE~
-----g:
ESTUARINE _ _ _ _ _ _
ESTUARINE
OCEANIC
FRESH
FRESH
WATER
g:
DC
in
U,
_
~
>
DC
in
J>
"'"'
a,
0
DC
-~---~
"'
OCEANIC
zo
,,
----g:
U,
ESTUARINE
ESTUARINE
in
N
-----~
in
Figure
Comparison of
of average
Figure 22. Comparison
average circuli
circuli
spacing on scales
scales of
spawnspacing
of juvenile and spawning
ing fall
fall chinook
chinook salmon
salmon ininSixes
Sixes River.
River.
ju1. Fresh-water
Fresh-water circuli
circuli on
on scales
scales of
of juveniles collected
collected from
from four
four known
veniles
known areas
areas
and times.
times. 2.
Circuli visually
visually separated
separated
2. Circuli
fresh-water and
and estuarine
estuarine zones
zones on
on
into fresh-water
scales
collected from
from the
scales of juveniles
juveniles collected
the
estuary in autumn.
autumn. 3. Circuli visually
separated into fresh-water, estuarine,
and oceanic zones in the first 50
circuli on scales
scales of spawners.
spawners.
[(27]
27]
reduced
period during
during summer,
summer,
reduced for
for aa period
some
this should
should be
be prespressome reflection
reflection of
of this
on their
theirscales.
scales .Close
Close examination
examination
ent on
the scales
scales revealed
revealed that about
about 70%
70 %
of the
possessed
outside edge
edge
possessedcirculi
circuli near
near the
the outside
of the
the area
area previously
previously defined
defined as
as "fresh
water" that
that were
were either:
either : 1)
1 ) thinner
thinner and
and
with narrower
narrower spacing
spacing than
than those
those obobserved nearer
served
nearer the
the nucleus,
nucleus, or
or 2) interrupted
broken and
and appeared
appeared to
to cross
cross
rupted or broken
other
The number
number of these
these cirother circuli.
circuli. The
culi
of reduced
reduced estuarine
estuarine growth
growth rangrangculi of
ed from
mode at
Further
ed
from 22 to 77 with aa mode
at 44.. Further
discussion
classified as
as fresh
fresh
discussionofof circuli
circuli classified
water
should be
be understood
understood to
also ininwater should
to also
clude circuli
formed during
during th
th~ period
clude
circuli formed
reduced growth.
growth.
of reduced
In
part three
three of
of Figure
Figure 22
22 are
are scales
scales
In part
from
from four
four age
age groups
groups of
of spawners
spawners colcollected
throughout Sixes
Sixes River.
lected throughout
River. The
The first
first
50
on these
these fish
fish appeared
appeared to be
be
50 circuli on
three distinct
distinctspacings.
spacings. The
The boundarboundarof three
ies
ies between
adjacent zones
zones of
of circuli
between adjacent
circuli
were
were abrupt.
abrupt. Because
Because these
could
these fish
fish could
possesscirculi
circuli formed
possess
formed in fresh
fresh water,
water,
estuary,
estuary, and
and ocean,
ocean, these
these zones
zones were
were
classified in this
this manner
manner and
and
initially classified
of average
plotted. Measurements
Measurements of
average circuli spacing
spacing for those
those circuli classified
classified as
as
fresh
fresh water match
match well
well with
withmeasuremeasurements of
of fresh-water
ments
fresh-water circuli in
in parts
parts one
one
and
two of
of Figure
Figure 22.
22. Also, measuremeasureand two
ments
average circuli
spacing of
the
ments of average
circuli spacing
of the
zone classified as estuarine on the
spawning fish match well with the
measurementsobtained
obtainedfor
for estuarine
estuarine cir"
cirmeasurements
culi
cui i in part
part two
two of
of Figure
Figure 22.
22. The
measurementsofofthe
thethird
third zone
zone on
on the
measurements
scales were considerably wider than
those
those classified
classified as
as fresh
fresh water
water and
and eseswere probably
probably
tuarine and therefore were
formed
formed in the
the ocean.
ocean. Based
Based on this
this exexamination, it was
was concluded
concluded that
that cirreturning spawners
spawners could
could be
culi on returning
divided into
into those
those formed
the three
three
divided
formed in
in the
major environments
environments by
byusing
usingaverage
average circirculi spacing,
spacing, and
and that
that these
these zones
zones were
were
distinct.
Separation
the various
various
Separationofof adults
adults into the
types of life histories
was based
based on
on
histories was
recognizing fresh-water,
fresh-water, estuarine,
estuarine, and
and
recognizing
oceanic
on the
the scales
scales and
and subsuboceanic circuli
circuli on
jective determination
determination of 11)) the relajective
tive number
number of
circuli formed
formed inin each
each
tive
of circuli
area,
position of
area, and
and 2) the
the position
of the
the first
o:eanic
annulus.
oceanic annulus.
The primary
primary difficulty in
in this
thissystem
system
The
was
recognition of
the first
firstoceanic
oceanic
was the
the recognition
of the
annulus.
For fish
that enter
enter the
the ocean
ocean
annulus. For
fish that
general conditions
in autumn, general
conditions for growth
are
improved over
fresh water
water
are improved
over those
those in
in fresh
or
the estuary
estuary but
but apparently
apparently are
are not
or the
those of prime
prime oceanic
oceanic growth that
might
be experienced
experienced during
spring
might be
during the spring
and
annulus did not
not always
always
and summer.
summer. An annulus
show
could ususshow strong
strong development
development but
but could
ually be
be recognized
recognized by the
the rapid
rapid change
change
wider circuli
circuli spacing
spacing of prime
prime spring
spring
to wider
growth
followed. Annuli
Annuli formed
formed in
in
growth that
that followed.
later
years tended
tended to be
be more
more obvious.
obvious.
later years
Criteria for
recognizing the
the various
various
for recognizing
types of life
life histories
histories on
on spawners
spawners were
were
types
developed
AI though no
no exexdeveloped (Figure
(Figure23)
23).. Although
amples
fish were
were found,
found, they
they
amplesofof typetype-I1 fish
should
show few,
few, if any,
any, fresh-water
fresh-water
should show
circuli
followed by
by wide
wide circuli
circuli formed
formed
circuli followed
the ocean.
ocean. Type-2 fish
fish showed
showed considconsidin the
erable
and then
then an
an
erable fresh-water
fresh-water circuli
circuli and
abrupt change
change to
wide circuli
circuli of
the
abrupt
to wide
of the
ocean. The
annulus was
was located
located far
ocean.
The first annulus
the nucleus
nucleus because
because of
extendfrom the
of the extended good
good growth
these fish
fish experexpered
growth that these
ienced
ocean. Type-3 fish
fish showed
showed
ienced in
in the ocean.
considerable
considerablefresh-water
fresh-water circuli
circuli followed
by
a band
band of intermediate
intermediate estuarine
estuarine cirby a
cufi
culi before
before changing
changing to
to oceanic
oceanic circuli.
circuli .
annulus was
was near
The first oceanic annulus
the estuarine circuli because these
fish entered the ocean in autumn,
leaving little time
time for
foroceanic
oceanic growth
growth
before
Type-4 fish
fish showed
showed an
an
before winter. Type-4
oceanic pattern
the type-3
type-3
oceanic
pattern similar
similar to
to the
fish but
but lacked
lacked any
any estuarine
estuarine growth.
growth.
fish
They
were distinguished
distinguished from
type-2
They were
from type-2
fish by differences in the relative
amount of fresh-water and oceanic
[ 281
[28]
growth
and the
the average
average circuli
circuli spacing
spacing in the estuary
estuary in autumn had
had fresh-water
growth and
ranging from
12 to
to 19
19 and
and averaverthe fresh-water
fresh-water zone.
zone. Type-S
fish circuli
in the
circuli ranging
from 12
Type-5 fish
about 15.
15. These
These circuli includshowed
showed many
many fresh-water
fresh-water circuli
circuli follow- -aging
aging about
those formed
formed in the
the estuary
estuary during
during
ed those
ed
by many
many oceanic
oceanic circuli
circuli of prime
prime ed
ed by
growth . The
oceanic annulus
annulus was
was the
period of reduced
reduced growth. This probprobthe period
growth.
The first oceanic
additional four
ably accounted
accountedfor
for the
the additional
located farther
from the nucleus
on ably
farther from
nucleus on
circuli
on the
theaverage
average on
on these
these scales
scales
these
4.
circuli on
these scales
scalesthan
than on
on types
types 2,
2, 3, and 4.
uveniles trapped
than on
on juveniles
trapped entering
entering the
the
Counts
fresh-water circuli
on the
the than
Counts of
of fresh-water
circuli on
various juveniles
juveniles supported
or seined in the estuary in
various
supported criteria
criteria for estuary
estuary or
separation ofof the
var.ious types
life spring.
spring.
separation
the various
types of
of life
The number
number of
fresh-water circuli on
on
The
of fresh-water
histor
ies (Figure
number of
histories
(Figure 24)
24).. The
The number
juveniles from
the tributaries
tributaries
scalesof
of juveniles
from the
fresh-water circuli
circuli on
onyearlings
yearlingsaveraged
averaged scales
was smaller
number of freshfreshsmaller than
than the
the number
about 32
and ranged
ranged from
38. was
about
32 and
from 23
23 to 38.
water circuli on
on juveniles
juveniles in
in the
the estuary
estuary
possessed many
fresh-water water
They possessed
many more
more fresh-water
autumn. Since
juveniles in
the
Since the
the juveniles
in the
than any
any other
othergroup.
group.Juveniles
Juveniles in autumn.
circuli than
SEINED IN
x = 31.6
SEINED
IN ESTUARY
ESTUARYAS
AS YEARLINGS
YEARLINGS 1
n4I
n=41
20
10
I0
0
20
~z
0
SEINED IN
IN ESTUARY
IN AUTUMN
! = 15.4
SEINED
ESTUARY IN
AUTUMN x
fl: 74
n=
20
~
10
o 10
IX
0.0
ILl
Ui
0..
SEINED
ESTUARY IN
EARLY SUMMER
SUMMER lt = 11.6
SEINED IN
IN ESTUARY
IN EARLY
fl:
h=153
153
20
10
0
~-LJ_~~-L~~~_L~--------------------------------~
TRAPPED IN LOWER RIVER IN SPRING 1: 10.6
nI35
20
10
o
0
11.6
rfftU___
10
l0
ILl
.
SEINED IN TRIBUTARIES IN AUTUMN 1
rrftLflk-1
~-L_L~~-L~~~_L~~~~~~~~~~~~~~~~~~
5
10
0
15
15
20
25
NUMBER
CIRCULI
NUMBER OF CIRCULI
30
35
40
Figure
juvenile fall chinook
chinook
Number of
of circuli
circuli classified
classifiedas
as fresh-water
fresh-wateron
on scales
scalesof
of juvenile
Figure 24. Number
salmon
I yearlings were
were from
from
salmon collected
collectedatatvarious
variouslocations
locationsand
andtimes,
times,1965
1965brood
brood (yearlings
the
1967 brood).
brood l .
the 1967
[ 30]
28.-~--------------------------------------------------------,
28
N
26
0
JUVENILES
fl JUVENILES
hr.:
II
MEAN
24
SD
SPAWNERS
RANGE
22
X
a>
01
•
18
8
16
:::!! 16
:::!!
~
60
20
74
74
74
14
:z:
12
i5
0 12
~
74
I
10
10
8
6
44
2
0
L-----~--~----~-----L----~----~----~----~----~----L-~
1st
2nd
3rd
4th
7th
4th
5th
6th
SUCCESSIVE BANDS
BANOS OF
OF FIVE
FIVE CIRCULI
CIRCULI
SUCCESSIVE
8th
9th
lOth
10th
Figure
Width of
of bands
bands of
offive
fivecirculi
circulion
onscales
scales ofoffall
fallchinook
chinooksalmon
salmoncollected
collected from
from
Figure 25.
25. Width
74
juveniles in
the estuary
estuary in
autumn and
and 160
160spawners
spawners collected
collected throughout
throughout
74 juveniles
in the
in autumn
Sixes
River, 1965
1965 brood.
Sixes River,
tributaries were
tributaries
were sampled
sampled early
early in auau tumn,
tumn, they
they probably
probably added
added more
more circirculi and
similar to
to type-3
culi
and became
became similar
type-3 fish
fish
or may
even have
have had
had numbers
numbers of
of circiror
may even
thatapproached
approached those
those of
ofyearlings,
yearlings,
culi that
depending on
on how late they
depending
they remained.
remained.
Life History
History ofofSuccessful
Successful Spawners
Spawners
of 160
fish originA sample
sample of
160 spawning
spawning fish
originating from
from the
the 1965
1965 brood
brood was
was selectselectating
ed
ed by
by stratifying
stratifying by
by age
age and
and sampling
sampling
date.
As an
date. As
an initial
initial approach
approach to
to deterdetermining where
mining
where the
thesuccessful
successful spawners
spawners
rearedinin their
their 1st
of life,
reared
1st year
year of
life, counts
counts
and
and meaurements
meaurements were
were made
madeof
of the
the first
first
50 circuli
circuli on
fish (Figure
50
on these
these fish
(Figure 25).
The width
width of
The
of the
the scale
scale image
image (98X)
(98Xl
for the
the first
firstfive
fivecirculi
circuliaveraged
averaged 10.6
10.6
mm,
mm, probably
probably reflecting
reflecting conditions
conditions of
of
good
growth in spring shortly after
good growth
after emeremer-
The average
gence from
from the gravel. The
average
gence
width
width of
of the
the second
second and
and third
third bands
bands of
circuli
was reduced
reduced to
and 9,5
9 .5 mm.
mm.
circuli was
to 9.9 and
These measurements
measurements probaby
probaby representrepresentThese
ed typical fresh-water growth. The
fourth band
band of circuli
circuli showed
showed a rapid
rapid increase inin width
12.5 mm
mm while that
that
crease
width to
to 12.5
the fifth
fifthand
andsixth
sixthbands
bands leveled
leveled off
of the
at 14.0
These bands
bands probably
probably rere1 4.0 mm
mm.. These
presented improved
the estuestupresented
improvedgrowth
growth in
in the
ary. The
The seventh
seventh band
band showed
showed an
an addiaddiary.
tional increase in
in width
width to
to 17.2
17 .2 mm.
mm .
This
wide spacing
spacing was
was generally
generally mainmain This wide
tained through
through the
the tenth
tenth group,
group, sugsugtained
gesting
in the
theocean.
ocean .
gesting growth
growth in
general pattern
pattern of
ofmeasurements
measurements
The general
the scales
scales of spawners
spawners was
of the
was similar
similar to
the defined
defined life
history of type-3
type-3 fish.
fish.
the
life history
impression was
was strengthened
strengthened when
when
This impression
measurements of the scales of
the measurements
[(31
31 ]
spawners
compared to
to successive
successive
spawners were
were compared
bands of five circuli
made on
on scales
scales
bands
circuli made
from
1965-brood juveniles
juveniles captured
captured in
from 1965-brood
autumn
autumn in
in the estuary
estuary (Figure
(Figure 25)
25).. The
The
pattern
the scales
scales of
the juveniles
juveniles
pattern on
on the
of the
was similar
was
similar to
measurements on
the
to measurements
on the
o;;ame
scales, although
althougl-o
same areas
areasofof the
the adult scales,
in
each band
band the
the measurements
measurements from
from
in each
juveniles
smaller.
juveniles were
were slightly smaller.
The
scales of
spawners from
the
The scales
of the spawners
from the
1965
1 965brood
broodwere
werethen
then subjectively
subjectively sortsorted
the five
five types
types of life
life histories
histories
ed into
into the
criteriapreviously
previously established.
established. The
The
with criteria
type-3
group was
was the
the most
most abundant
abundant
type-3 group
(Table 8).
(Table
The scales of type-4 and type-S
those
spawners
spawnersdid
didnot
not match
match well
well with those
juveniles caught
caught in
in the
the estuary
estuary in
in
of
of juveniles
autumn.
These spawners
spawners had
had numbers
numbers
autumn. These
fresh-water circuli
circuli that
that ranged
ranged from
from
of fresh-water
37 and
and averaged
averaged 28,
23 to
to 37
23
28, in
in addition
addition to
lacking
circuli that
were recognizable
recognizable
lacking circuli
that were
as
estuarine. The type-2
type-2 spawners
spawners also
also
as estuarine.
and
lacked
lacked recognizable
recognizable estuarine
estuarine circuli and
had
had numbers
numbersofof fresh-water
fresh-water circuli
circuli that
ranged
20 and
and averaged
averaged 19.
19.
ranged from
from 1188 to 20
Since
spawners were
were probprobSince these
these type-2 spawners
average, based
ably
larger than average,
ably larger
based on
on their
numbers
they may
may have
have sursurnumbersof
of circuli,
circuli, they
vived
entering the
the ocean
ocean in
in
vived better
better after entering
summer
majority of potential
potential
summer than
than the
the majority
Table 8. Relative
Table
different type-2
Relative abundance
abundanceof
of different
captured in
in the
the ocean
ocean surf.
surf.
type-2 fish captured
lifehistories
histories among
among spawning
spawning
types of life
types
age groups
groups of spawners
spawners with
the
All
age
with
the
fall
chinook salmon
salmon inin Sixes
Sixes River,
River, based
fall chinook
type-3
life
history
included
a
fish
type-3
life
history
included
a
few
fish
on
scale characteristics
characteristics of
1965
on the scale
of the
the 1965
with more
more fresh-water
fresh-water circuli than
than were
were
brood.
found
on the
the juveniles.
juveniles. This
Thissuggests
suggests
found on
Age
R.eturn
Age at Return
that
largest juveniles
juveniles have
have highest
highest sursurthat largest
Type of
2
3
44
5
Life
Life
A
similar
possibility
exists
for
vival.
vival.
similar
possibility
exists
for
the
-N-%
History
Histgry
N
N
N
N
% ~
%
%
number
of
estuarine
circuli.
The
mean
number
of
estuarine
The
mean
1
0.0
0
00
0.0
0.0
0
0.0
0
number of
about 16
16 fresh-water
fresh-water circuli
circuli
number
of about
2
2.5
1
1
2.5
1
2.5
2.5
1
33
38 95.0
36 90.0
36 90.0
35 87.5
that
on
returning
spawners
indicated
returning
spawners
indicated
4
0.0
3
00
3
7.5
0.0
0
3
7.5
they
were
about
9.0
em
long
at
the
bethey
were
about
9.0
cm
long
the
be55
1
0
0
0.0
2.5
0.0
4 10.0
ginning
of
the
improved
growth
the
ginning
of
the
improved
growth
in
the
Totoi
40
Total
40 100.0
100.0
40 100.0
40 100.0
40 100.0
100.0
40
100.0
40
100.0
estuary
(Figure 28)
The mean
mean number
number
estuary (Figure
28).. The
estuarine circuli
circuli on
on the
thespawners
spawners sugsugThe
The distribution of
of the
thevarious
various types
types of estuarine
gested that
that an
an additional
additional 4.0 em
cm of length
histories with
with the
the age
age groups
groups gested
of life histories
estuary (Figure
(Figure 29),
was added
addedinin the
the estuary
combined
was:Type
Type1-0.0%,
1-0.0%,Type
Type22- was
combined was:
the average
average final size
size about
about
making the
2.5%,
Type3-90.6%,
3-90.6%, Type
4-3.8% making
2 .5%, Type
Type 4-3.8%
corresponded well
3.0 em.
cm. This
This corresponded
well with
and Type
Type5-3.1
5-3.1%.
and
%. There
Theredid
didnot
notappear
appear 113.0
average size
size of juveniles in the
the average
to be
effect of juvenile
juvenile life
life history
history the
to
be any
any effect
(Figure 19).
19) .
estuary inin autumn
autumn (Figure
on
the age
age at
at return
return ofofspawners.
spawners. The
The estuary
on the
distribution of life history types
types was
was
Discussion
Discussion
about
the ages
about equal
equal among
among all the
ages of
Initial
Downstream
Dispersal of
of Fry
Fry
Initial
Downstream
Dispersal
spawners.
Most
the mature
mature fall
fall chinook
chinook salsalThe distributions
Most of the
The
distributions of fresh-water
fresh-water and
and
estuarine circuli
circuli on
on the
estuarine
the type-3
type-3 spawnspawn- mon returning to Sixes River spent
about 33 months
months of
juvenile life in
in
of their
their juvenile
ers were
were compared
compared to
the distributions
distributions about
ers
to the
water. There
There is
is an
an advantage
advantage to
to
of fresh-water
fresh water.
fresh-water and
and estuarine
estuarine circuli on
on fresh
fresh-water residents
residentswhen
when they
they fully
juveniles caught
caught in
juveniles
in Sixes
Sixes River
River estuary
estuary fresh-water
theavailable
available rearing
rearingarea
area (Chap(Chaputilize the
(Figure 26
26 and
and 27).
in
autumn (Figure
27). The
The utilize
in autumn
Spawning fish set
set the
the stage
stage
distributions
match sufficiently
sufficiently well
well to man,
man, 1966). Spawning
distributions match
utilization by
bydepositing
depositing their
their
for this
this utilization
argue
argue that these
these spawners
spawners and
and juvenjuven- for
widely separated
separated areas
areas over
over aa
eggs
eggs in
in widely
iles
were from
from the
thesame
same population.
population.
iles were
1
1
1
1
1
1[ 32]
32 1
....
25
23 r-------------------------------~
y: -18972
4- 19923X
.189724199238
49(5
30
'
R
900
0900
A• 0
N • 38
36
N
N
153
N "' 153
2C
20
IC
10
-·
3C
50
N•
20
30
20
' !)
10
.....
-·
0
- .
~
32
30
~
22
20
~
IC
10
~
a:
S
Q
6
)!:;
0
a:
I2 10
l!l
0
~0
z2
AGE2
AGE 2
N
N • 38
38
32
30
20
IC
10
0
.JUVENILES
JUVENILES
N • 74
N
•o
81
21
20
40
IC
10
50
60
70
80
90
100
FORK
IN CM
FORE LENGTH IN
8184968
CINGUU
Figure
Number of circuli
circuli classified
classified as
as
Figure 26.
26. Number
fresh-water
1965-brood juvenile
juvenile fall
fresh-water on
on 1965-brood
chinook salmon
salmon captured
captured in
in Sixes
Sixes River
River
chinook
estuary
1966 and
reestuary inin autumn
autumnof
of 1966
and on returning
the type-3
type-3 life
turning spawners
spawnerswith
with the
history.
Relationship between
between number
number
Relationship
circuli classified
fresh-water and
of circuli
classified as
as fresh-water
fork
length of juvenile
juvenile fall chinook
chinook salsalfork length
mon
recruited to
to Sixes
Sixes River
River esmon recently recruited
tuary
spring, 1966.
1966.
tuary in spring,
Figure 28.
20
30
protracted period.
period. The
The population
population also
also
protracted
60
1!0
...... .
I0
10
2
30
20
I0
10
....
-·
00
"'
4
~\'j
~
AGE,
30
20
!0
10
..-·.
0
30
•o
20
.aNENILES
.58688.2.8
N
74
""' 74
30
""
•o
20
40
10
0
5
0
IN
30
MMNER Of 68018.1
..
28
Figure
Fig~re 27.
27. Number
Number of
of circuli
circuli classified
classified as
as
estuarine on
1965-brood juvenile
juvenile fall
estuarine
on 1965-brood
hinook salmon
captured in
in Sixes
Sixes River
River
chinook
salmon captured
estuary
in autumn
estuary in
autumn of 1966
1966 and
and on
onrereturning
with the
turning spawners
spawners with
the type-3
type-3 life
life
history.
history.
has evolved
has
evolved aa mechanism
mechanismthat
that allows
allows for
downstream dispersal
dispersal of juveniles
juveniles
_rapid
rapid downstream
as they
they emerge
emerge from
the gravel.
gravel . The
The
as
from the
mechanism serves
reduce predation
predation
mechanism
serves to
to reduce
and minimize
m inimize the
the energy
energy expenditure
expenditure
and
necessary for
abunnecessary
for adjusting
adjusting population abundance in
relation to
to food
food and
and space.
space. This
dance
in relation
dispersal involves
visual orienoriendispersal
involves lack
lack of
of visual
tation of the fry, resulting
resulting in
their drifttation
in their
ing downstream
downstream during
during the night
night of
of
ing
emergence. Fry
the
emergence.
Fryprobably
probablydrift
drift with
with the
currents during darkness until they
reach quiet
until light levels
levels
reach
quiet water
water or
or until
(moonlight or daylight)
daylight) again
again allow
allow visvis(moonlight
ual orientation.
orientation . Additional
Additional downstream
downstream
ual
movement of
newly emerged
emerged fry may
may
movement
of newly
cont inue for several days until they
continue
develop the
the behavior
behavior of resident
resident fish.
fish .
develop
Downstream migration
of newly
emerged chinook
chinook salmon
salmon has
has been
been docdocemerged
umented elsewhere
elsewhere (Chambers,
(Chambers, 1965;
umented
[ 33]
C
33]
8
7
::::!E
u
0
~
:I:
I
y = -1.5406 + 0.4362X
Y
R
R = 0.635
N
N = 74
6
5
.-
~ 4
a:
(!)
w
zz 3
0:
<(
.-::>
I(/)
(I)
2
w
Ui
5
6
7
8
9
10
10
II
II
12
12
13
13
14
14
115
5
16
16
17
17
18
lB
19
19
20
NUMBER
CIRCULI
NUMBEROF
OF ESTUARINE
ESTWIRINE CIRCULI
Figure 29.
Relationship between
between estuarine
number of circuli
circuli classiclassiFigure
29. Relationship
estuarine growth
growth in
in length and number
fied as
as esuarine
esuarine for juvenile
juvenile fall
fallchinook
chinooksalmon
salmoncaptured
capturedininSixes
SixesRiver
River estuary
estuary in
in auautumn 1966.
tumn
1966. The
estuarine growth
length was
was the
the difference
difference bebeThe estimate
estimate of
of estuarine
growth in
in length
tween
measured size
when captured
captured and the
the predicted
predicted size
size at
tween the
the final measured
size of
of the
the fish when
the
beginning of the
the period
period of
of improved
improved estuarine
estuarine growth,
growth, based
based on
on the
the number
number
the beginning
of fresh-water
fresh-water circuli
circuli (Figure
(Figure 27).
Thomas, Banks,
Banks, and
and Greenland,
Thomas,
Greenland, 1969;
1969;
Lister
and Genae,
1970).
Lister and
Genoe,1970;
1970; Miller,
Miller, 1970).
Lister
1970) found
Lister and
and Genae
Genoe((1970)
found few
few fry
residing in
Big Qualicum
Qualicum River
River durdurresiding
in the Big
ing early
early spring,
spring, athough
athough large
large numbers
numbers
had already
had
already moved
moved downstream.
downstream. They
They
suggested the
the following sequence
suggested
sequence of bebehavior after
havior
after emergence:
emergence : initial hiding
(possibly in the gravel), association
with bank
with
bank cover,
cover, appearance
appearance along
along open
open
shorelines,and
and finally,
finally, movement
shorelines,
movement into
into
higher velocity locations along the
stream margins or farther offshore.
These observations agreed with the
studies in the
studies
the experimental
experimental troughs
troughs and
and
with general
with
general observations
observations in
in Sixes
Sixes River.
River.
Thomas,
Banks,
and
Greenland
( 1969) demonstrated
demonstrated aa marked
marked reducreduc(1969)
tion in
in swimming
swimming ability
ability of
ofalevins
alevins near
near
tion
the time of
of yolk
yolk absorption.
absorption. This
This result
result
the
was
to the
the conclusions
conclusions reachreachwas important
important to
ed
this study
study about
about downstream
downstream mied in this
gration,
this reduction
reduction in
in swimming
swimming
gration, as
as this
ability
may be
be a
a key
key factor
factor facilitating
facilitating
ability may
immediate
their
immediatedispersal
dispersalofoffry
fry after
after their
emergence at
combination of
of
emergence
at night.
night. The combination
the bebereduced
wimming ability
reduced"sswimming
ability and
and the
havior of newly
newly emerged
emerged fry appear
appear to
havior
be
stream living.
be adaptive
adaptive in
in stream
1970) argued that
downthat downMiller ((1970)
stream
migration- results largely
from
largely from
stream migration
in cold
cold temperatemperapoor swimming
poor
swimming ability
ability in
tures.
factor was
was undoubtedly
undoubtedly an
an
tures. This
This factor
important
cause of
fish leaving
leaving his
his exeximportant cause
of fish
systems, but
may not
not have
have
perimental systems,
perimental
but it may
been the
been
the primary
primary reason
reason for downstream
downstream
migration of
newly emerged
emerged fry
the
migration
of newly
fry in the
Lemhi River,
River. Although
used fry
fry
Lemhi
Although Miller used
[ 34]
C
34]
had been
been captured
captured in
in the downdownthat had
stream trap
the river,
river, his
his definition
definition
stream
trap in
in the
of a
a fry
fry was
was a
a fish
fish less
less than
than 5.0 cm
em in
in
lack of fish at
length. Because
Because of aa lack
times,
few.
times, he
he also
also accumulated
accumulatedfry
fry for
for aa few
days before
before running
running experiments
experiments and
and
days
extensive avian
be vulnerable
vulnerable to extensive
avian and
and
be
fry would
piscine predation.
predation. Surviving
Surviving fry
would
piscine
crowded and
and would face
face aa
be extremely crowded
be
shortage of food. For juveniles to
emerge and
these high
high dendenemerge
and remain
remain in
in these
in the
the spawning
spawning streams
streams and
and later
later
sities in
sities
disperse primarily by
by means
means of
of social
social
to disperse
acclimated
hours in
in his
acclimatedthem
themfor
for 24
24 hours
interaction would
would appear
appeartoto be
be ineffithese fish
could no
no interaction
systems.
systems.Many
Manyof
of these
fish could
In
Carline
experiment,
one
cient.
emerged fry
longer be
be considered
considered newly
longer
newly emerged
1968)
showed
that
socially
dominant
(
(1968)
showed
that
socially
dominant
and
were
probably
past
the
initial
period
and were probably past the
period
coho salmon,
kisutch (Walbaum)
excoho
salmon, 0.
0. Icisutch
(Walbaum) exof downstream
downstream migration.
migration.
pended more
activity than
than
more energy
energy for
for activity
Miller (1970)
( 1970) found
found that
thatdensity
density was
was pended
obtained more
more
subordinates. They
They also
also obtained
important in the
the number
number of
of fry
fryremainremain- subordinates.
important
because of
social position
position and
and
food because
of their social
experimentalsyssys- food
ing in
in or
orleaving
leavinghis
hisexperimental
ing
grew
than
subordinates.
Without
grew
better
than
subordinates.
tems,
he suggested
suggested that social
social bebetems, but he
mechanism for
rapid dispersal,
dispersal, dendenfor rapid
not play
play aa role
rolebecause
because movemove- aa mechanism
havior
havior did not
sities
of
fry
at
emergence
sites
be
sities
fry
at
emergence
sites
would
be
ment
occurred primarily at
at night.
night. Based
Based
ment occurred
greater
those
tested
by
Carline.
far
far
greater
than
those
tested
by
Carline.
is
present
studies
in
Sixes
River,
it
on
on present studies in Sixes River,
suggested
may only be
be Energy costs in achieving dispersal
suggestedthat
that high
high density
density may
the
would probably
probably be
proportional to
be proportional
to the
with downstream
downstream migration
migration would
coincidental with
coincidental
social interactions.
interactions. Food
Food rerenumber of
of social
of newly
newly emerged
emerged fry, and
and isis probably
probably number
wards
fish
attempting
to
become
sowards
to
fish
attempting
to
become
sonot a primary
primary causal
causal factor.
factor. Considering
Considering
dominants under
under this
this suggested
suggested inincial dominants
that most
most emergence
emergence and
and downstream
downstream cial
tense
competition
might
not
offset
the
tense
competition
might
not
offset
the
the
movement
probably occurred
occurred on
on
movement probably
energy cost
cost in
in acquiring
acquiring limited
limited food.
food.
same
op- energy
samenight,
night, there
there would
would be
be little
little openergy cost
cost and
and
Because of
of the
the potential energy
portunity for interaction among fry. Because
probable high
rate of
of predation,
predation, rapid
rapid
high rate
on subsequent
subsequent days
days as
as fry probable
However,
However, on
does not involve
involve sosodispersal that does
develop
fish and
resident fish
and during the
the initial dispersal
develop into resident
seem to have
have survivbehavior would seem
remainder of their residence
residence in fresh cial behavior
remainder
al value
fry .
value to fry.
water,
social behavior
behavior appears
appears important al
water, social
in
governing their
the
in governing
their distribution
distribution.. With
With the
consideredspring
springchichi( 1970)considered
Miller (1970)
protracted emergence
period, fry emergemergence period,
emerg- nook
nook salmon
salmon fry moving
moving downstream
downstream in
in
ing late must
must face
face fish
fishalready
already occupyoccupy- the
ing
Lemhi River
River aa loss
loss to
total producproducthe Lemhi
to total
Inte-raction occurs
occurs and
and is
is tion.
ing
territories. lnteiaction
ing territories.
Apparently the
theareas
areas downstream
downstream
tion . Apparently
effective
effective in
in dislodging
dislodging smaller,
smaller, less
less dede- were
were not
not suitable
suitable for
for rearing.
rearing. In Sixes
Sixes
Contrary River
veloped
(Reimers, 1968). Contrary
veloped fish
fish (Reimers,
concluded that
that downstream
downstream
River it was
was concluded
to
Miller's conclusion
conclusion about
about the
the rela- movement
to Miller's
movementof
of fall chinook
chinook salmon
salmon had
had
between nocturnal
nocturnal movement
movement survival
tionship
tionship between
survival value,
value, since
since fish
fish rearing
rearing in
in the
the
and social
social behavior,
behavior, nocturnal
movement main
and
nocturnal movement
main river and
and estuary
estuary grew
grew better
than
better than
does
in the
the displacement
displacement of those
does play
play aa role
role in
those in
the tributaries
tributaries and
and predominatpredominatin the
In experiments
experiments in ed
socially
socially inferior
inferior fish
fish.. In
ed as
as returning
returning spawners.
spawners.
Sixes
were
Sixes River
River subordinate
subordinatefish
fish that
that were
nipped or threatened
threatened all day
day did
did not
not
nipped
ofTemperature
Temperature on
onResidence
Residence
Influence of
move downstream
dusk.
move
downstream until dusk.
the Main
Main River
River
in the
Without the
the uggested
!iuggestedmechanism
mechanism for
Without
fry many
manymore
morejuvenjuvenrapid
dispersal of fry
rapid dispersal
There
evidence that
that temtemThere was
was little evidence
present at
at emergence
emergence sites
sites
iles
be present
iles would be
perature was
important factor
factor inwas an
an imoortant
than are
They would perature
than
are currently observed.
observed. They
[ 35]
(35
1
fluencing the length of residence of
main river.
river. However,
However, if
juveniles in
juveniles
in the main
cooler
cooler conditions
conditions had
had prevailed,
prevailed, more
more
fish
probably would have
have reared
reared longer
longer
fish probably
in
in the
the main
main river
river and
and reached
reached aa larger
larger
ination of annual
ination
annual variation
variation ininresidence
residence
temperature would
would be
in relation to temperature
be
valuable.
With more
more fresh-water
fresh-water rearing
rearing area
area
fall chinook
chinook salmon
salmon
available, the
available,
the run
run of fall
in
Sixes River
River was
was probably
probably once
once larger
larger
in Sixes
The present
present total run
run averaverthan today.
today. The
than
( McGie,
ages
ages about
about 2,500
2,500 spawning
spawning fish
fish (McGie,
1970)
Unfortunately, there
evi1970).. Unfortunately,
there isis little
little eviruns in
dence
dencetoto indicate
indicate the
the size
size of
of runs
earlier years.
years.
temperatures by
by
size. Avoidance
Avoidance of high
high temperatures
size.
salmonids
increased production
production assocassocsalmonids or increased
increased flow
flow and
and reduced
reduced
iated with increased
iated
temperature have been documented
(Gibson,
!Gibson,
1966; Havey and Davis,
1970)
Even though
though maximum
maximum tempertemper1970).. Even
atures in Sixes
Sixes River
River were
were not
not always
always
atures
Population Density
Density Versus
Versus Growth
Growth of
lethal level
level for fall
fall chinook
chinook
above the
above
the lethal
Juveniles in the Estuary
salmon, growth efficiency has been
Most of the
the mature
mature fall
fallchinook
chinooksalsalMost
decline for other
other salmonids
salmonids at
shown
shown to
to decline
returning to Sixes River spent
mon returning
temperatures considerably below the mon
about 3 months
months in
estuary after they
in the estuary
lethal level (Brett, Shelbourn, and about
fresh water.
water. The
The number
number of juvenjuvenShoop,
Before Sixes
Sixes River
River was
was left fresh
Shoop, 1969)
1969).. Before
iles in the
the lower
lower estuary
estuary in
in 1969
1969 began
began
mouth iles
logged,
logged, timber
timber extended
extended to
to the mouth
and then
then
increase during
May and
to increase
during late
late May
of the
by the
the river,
river, as
as evidenced
evidenced by
the prepre- to
June. When
When the
the
The earlier
earlier rapidly increased in June.
sence of
stumps. The
sence
of old-growth stumps.
population
reached
20,000
fish
in
early
population
reached
20,000
fish
early
the watershed
watershed probprobextensive
extensive cover
cover in
in the
rate of growth
growth of
ofjuveniles
juveniles
June, the
the rate
ably
maintained cool
cool temperatures in June,
ably maintained
population peaked in
decreased. The
The population
summer
summer as
as well
well as
as stable
stable flows
flows during
during decreased.
and early
early August
August and
and then
then
late
July and
late July
winter.
juvensubsided.The
Therate
rateof
of growth
growth of juvenIt appears
appears that
the amount
amount of freshfresh- subsided.
that the
population fell
increased when
iles increased
when the
the population
water
rearing area
area used
water rearing
used by
by juvenile
juvenile fall iles
at
the
to
about
100,000
fish
at
the end
end of
of
to
about
100,000
fish
chinook
salmon in Sixes
Sixes River
River was
was once
once
chinook salmon
August.
August.
total yield
yield
substantially
substantially larger,
larger,and
and the
the total
of effective migrants
migrants was
was higher
higher than
than toIt is hypothesized
hypothesized that
high popupoputhat high
estuary was
was probably
probably lation
day.
However, the estuary
day. However,
major cause
the
density was
lation density
was aa major
cause of
of the
affected by
bywatershed
watershed alterations
alterations depressed
little affected
little
of juveniles
juveniles
depressedrate
rateofof growth
growth of
and
have reared
reared any
in during midsummer.
and may
may not have
any m<;>re
more fish
fish in
was essentially
midsummer. There was
past years
does now.
great- no
past
years than
than itit does
now. With
With greatthe relationrelation months. If the
no growth
growth for
for 33 months.
er rearing
area inin the
er
rearing area
the main
main river,
river, the
the ship
between biomass
biomass of
juveniles and
and
ship between
of juveniles
autumn and
and yearling
yearling migrants
migrants availability
food was
was the
the major
major
number of autumn
availability of
of their food
cool concon- factor
was
was probably
probably much
much larger. The cool
resulting in
in depressed
depressed growth
factor resulting
growth of
1964 yielded
yielded more
more auau - fish,
of the
the fish
fishshould
should have
have bebeditions
during 1964
ditions during
fish, growth of
tumn
and yearling
yearling migrants
migrants than
than any
any gun
the same
same population
population size at
tumn and
gun at the
the study.
stopped. That growth
growth started
started
other
year of the
study. Other
Other years
years which it stopped.
other year
size or biomass
biomass five
five
yielded
fish in
in these
these groups,
groups, owing
owing at aa population size
yielded few
few fish
than when
when it stopped
small number
number of fish remaining
remaining in
in times higher than
to the small
appear to
disprove the primary
primary
would appear
to disprove
fresh
During 1964,
1964, when
fresh water.
water. During
when aa fair would
hypothesis. However,
hypothesized
However, it is
is hypothesized
population remained in lower Sixes hypothesis.
that the
the capacity
capacity of
of the
the estuary
estuary
further that
resident fish were
were larger
larger than
than further
River,
River, the
the resident
salmon increased
increased
to rear
rear fall chinook
chinook salmon
in
1969, suggesting
suggesting that
that summer
summer resiresi- to
in 1969,
the summer.
summer.
dence
necessarily be
dence would
would not necessarily
be termina- during the
An increase
in the
the rearing
rearing capacity
capacity of
increase in
ted
particular size.
size. AA closer
closer examexamted at aa particular
[[36]
36]
the
estuary was
prothe estuary
was probably
probably indirectly produced
the estuestuduced by
by greater
greaterutilization
utilization of
of the
ary
juveniles with
time. Prior
Prior to
ary by
by the
the juveniles
with time.
the
large increase
increase in
June,
the large
in population
population in June,
most
juveniles were
were confined
confined to the
most juveniles
shoreline
shoreline and
and were
were nearly
nearly absent
absent at
at the
lower stations.
When the
the number
lower
stations. When
number of
of
peaked in
July, juveniles
juveniles were
were livfish
fish peaked
in July,
ing
all stations
stations and
and were
were distributed
distributed
ing at all
in deep
throughout
the estuary,
estuary, even
even in
deep
throughout the
water.
The
reason that
The reason
that juveniles
juveniles did
did not
not initially use the entire estuary is unbut isissuspected
suspected to
to be
be behavioral
behavioral
known, but
rather
than physiological.
physiological. The
early beberather than
The early
these fish
fish appeared
appeared to involve
involve
havior of these
havior
hiding
and agonistic
agonistic behavior
behavior and
and rehiding and
quired orientation
orientationwith
with the
the bottom
quired
bottom in
in
shal!ow
stumps or
shaUow water.
water. Areas
Areas around
around stumps
logs often
tide that
that
logs
often had
had pools
poolsatat low
low tide
contained
contained isolated
isolated groups
groupsofof small
small fish
that presumably
presumably were
were temporarily
temporarily traptrapped. They
leave at
ped.
They had
had opportunities
opportunities to
to leave
high
high tide
tide but
but did
did not.
not. As
As density
density and
and
the size
the
size of the
the fish
fish increased,
increased, the
the inindividuals apparently
apparently changed
changed to
to a
dividuals
a pelapelagic, aggregative
modeofof life.
life. A similar
gic,
aggregative mode
similar
changeinin distribution
distribution with size
change
size was
was obobserved for
for pink
pink salmon,
salmon, 0.
0 .gorbuscha
gorbuscha
served
(Walbaum), in Fitz
(Walbaum),
Fitz Hugh
Hugh Sound,
Sound, BritBritParker,
ish
Columbia ((LeBrasseur
LeBrasseur and
and Parker,
ish Columbia
1964).
Adaption
of fish
to salt
Adaption of
fish to
salt water
water was
was
distribution of
probably
probablynot
not limiting
limiting the
the distribution
juveniles in
in the estuary.
the estuestuary. Since
Since the
estujuveniles
ary was
ary
was primarily aa two-layered
two-layered system,
system,
juveniles
could have
juveniles could
have easily
easily moved
moved into
into
the pelagic
and· remained
in fresh
the
pelagic zone
zone and
remained in
fresh
water. Wagner, Conte, and Fessler
(1969)
showed in
( 1969 I showed
in laboratory studies
that juvenile
juvenile fall
fall chinook
chinook salmon
salmon would
would
have
difficulty adapting
adapting to
to higher
higher
have little
little difficulty
salinities at small
salinities
small sizes
sizes where
where they
they have
have
opportunities for
for acclimation
opportunities
acclimation such
such as
as in
aa tidal estuary.
estuary.
In
In addition
addition to
to greater
greater utilization
utilization of
of
the
by juveniles
with time, evithe estuary
estuary by
juveniles with
evidence
the nunudence indirectly
indirectly indicated
indicated that
that the
tritional level and
food production
production of
and food
the
estuary increased
increased during
the sumsumthe estuary
during the
mer.
Shallow areas
the estuary
estuary were
were
mer. Shallow
areasof
of the
heavily
colonized by
by Corophium
Corophium spinispiniheavily colonized
Stimpson), aa tube-dwelling
corne
come I(Stimpson),
tube-dwelling amphipod important
the diet of the
the juvenile
juvenile
pod
important in
in the
salmon . As
salmon.
As aa result
resultof
of the
the sill
sill building at
the mouth,
mouth, the
the shallow
shallow area
area of the
the esesthe
the flat
tuary rapidly increased
increased over
over the
shore!
in e. This
shoreline.
This enlarged
enlarged the
the habitat
habitat for
Corophium colonization and
and presumably
presumably
provided more
the juveniles.
juveniles.
provided
more food
food for
for the
The
si II probably
probably had
had an
an even
even greater
greater
The sill
effect
than increasing
increasing the
wetted proproeffect than
the wetted
ductive
area of
the estuary.
estuary. Although
Although
ductive area
of the
there was
was no
measure of
there
no direct measure
of nutrient
level,
may have
have created
created an
level, the
the sill may
an effective nutrient trap
trap in
in aa manner
manner similar
similar
fective
that reported
reported for fjords
fjords with
with aa shalshalto that
(Ketchum, 1967).
1967) . At
At high
high
low
low outer
outer sill
sill (Ketchum,
water of
of high
high density
density
tide, nutrient-rich water
tide,
entered
estuary over
mixed
entered the
the estuary
over the
the sill, mixed
at
the mouth
mouth with
with.estuarine
estuarine water,
water, and
and
at the
the entire
entire water
water mass moved upstream.
the
the sill
sill acted
acted to hold
hold
During ebb
During
ebb tide
tide the
the dense
dense sea water in the estuary,
thereby trapping the nutrients, while
fresh water
water moved
moved downstream
downstream in aa
the fresh
shallow surface
surface layer.
layer.
shallow
Strong
during the
the
Strong northwest
northwest winds
winds during
summer
summer produce
produce extensive
extensive upwelling
upwelling of
nutrient-rich water
water along
along the
the southsouththis nutrient-rich
ern
coast of
Oregon (Pattullo
(Pattullo and
and DenDenern coast
of Oregon
This was
was particularly
particularly noticenoticener,
ner, 1965). This
able
mouth of
able along
along the
the beach
beachatat the
the mouth
Sixes
tide"
Sixes River
River where
where periodic
periodic "red
"red tide"
blooms were
blooms
were common.
common.This
This "red
"red tide"
water
was carried
carried into
the estuary
estuary at
at
water was
into the
high
tide .
high tide.
Production of algae
algae in
in the
the estuary
estuary was
was
Production
high, based
on visual
visual observations
of the
the
high,
based on
observations of
development
development of Enteromorpha and Spongiomorpha.
primary
giomorpha. As
As these
these and
and other
other primary
producers died,
producers
died, sedimentation
sedimentation of
of detritus
detritus and
occurred. Organic
Organic detritus
and debris
debris
the ocean.
ocean. SedimentaSedimentaalso
also entered
entered from the
tion of
of fine
finesand
sand and
and organic
organic material
material
tion
continued throughout
throughout the
the summer.
summer. OrOrcontinued
[ 37]
(37]
ganic detritus and
and associated
associated micro-ormicro-organic
ganisms form
source of food
ganisms
form the
the primary source
forCorophium
1968) .
for
Corophiurn (Green, 1968).
Another
possible explanation
Another possible
explanation for
for the
reduced growth
in mid-summer
mid-summer was
was sussusreduced
growth in
pected, since
juveniles entering
entering the
the esespected,
since juveniles
tuary were
were considerably
considerably smaller than
tuary
those already
lower stastathose
already present
presentat
at the
the lower
tions. The
The outcome
outcome would
would have
have been
been
tions.
in
abundance of
primary food
food organorganin abundance
of primary
seemed unlikely without obvious changes
changes in some
some environmental
environmental
vious
parameters
temperaparameters such
such as
as salinity
salinity or temperature,
but should
should be
be examined
examined in
in the
ture, but
future. Competition for the
the food
food resource with other
other fishes
fishes probably
probablyoccuroccursource
red,
its importance
importance was
was unknown.
unknown.
red, but its
Abundant
surf smelt,
smelt,
Abundant species
specieslike
like the
the surf
Hy pomesus pretiosus (Girard),
(Girard), and
andshinshinHypomesus
er perch,
er
perch, Cym
atogaster aggregata (Ci
(GibCymatogaster
bbons), appeared
appeared to be
be about
about equally
equallynunumerous
the summer.
summer.
merous throughout the
isms
mean size
size would
would demonstrate
demonstrate only
only
that mean
an
"apparent" reduced
reduced rate
growth.
an "apparent"
rate of growth.
This
since marked
marked fish,
This was
was unlikely since
fish, exempted
empted from
from recruitment,
recruitment, grew
grew at
at the
same rate
the unmarked
unmarked popupopusame
rate as
as fish
fish in the
Importance
Fresh-Water and Estuarine
Estuarine
Importance of Fresh-Water
lation.
close examination
examination of
the fate
fate
lation. A close
of the
Rearing
juveniles entering
entering the
the upper
upper estuary
estuary
of juveniles
from
the main
main river
river resolved
resolved the
the size
size
from the
Based on
the analysis
analysis of scales,
scales, fish
fish
Based
on the
Catch per
per seine
seine haul
juven- with the
disparity. Catch
haul of juventhe type-3
type-3 life history
history were
were the
the
iles
their most abundant group of returning
iles suggested
suggesteda adefinite
definite delay
delay in
in their
movement from
upper to
the lower
lower spawners.
movement
from the
the upper
to the
remained in fresh
fresh
spawners. These
These fish
fish remained
estuary.
the upper
upper estuary
estuary water
estuary. Numbers
Numbers in
in the
water for about
about 33 months
months and
and then
then enenpeaked 55 to
weeks before
those in
peaked
to 6 weeks
before those
in the tered
tered the
the estuary
estuary for
an additional
additional 33
for an
lower
estuary. When
When newly
newly recruited
recruited months
lower estuary.
residence. Because
Because these
months of residence.
these fish
fish reached
reached the
upper estuary,
estuary, their spent
the upper
spent part
part of
of their juvenile
juvenile life
life inin each
each
growth
must have
have improved,
improved, and
and prepre- area,
growth must
area, fresh-water
fresh-water and
and estuarine
estuarine rearing
rearing
sumably
lag allowed
allowed them
them to
to were
sumably this
this time
time lag
were judged
judged to be
be about
about equally
equally imporimporincrease in size. Fish
increase
Fish seined
seined near
near the
the tant to
to their
theirsuccess.
success. Chinook
Chinook salmon
salmon in
head
tended to be
be closer
closer to the
head of
of tidewater tended
Columbia and
and Klamath
Klamath rivers
rivers were
were
the Columbia
the size
of fish
the
size of
fish captured
captured in
in the
the lower
lower also
also found
spend aa significant portion
portion
found to spend
estuary than
estuary
than to
downstream migrants
migrants of their juvenile
to downstream
juvenile life in
in the
the estuary
estuary after
trapped
trapped just above
above tidewater.
leaving fresh
(Rich, 1920;
1920; SnySnyleaving
fresh water
water (Rich,
der, 1931).
1931).
The
growth of
of juvenile
The reduced
reduced growth
juvenile fall der,
chinook salmon
salmon in Sixes
Sixes River
River estuary
estuary
chinook
With
knowledge of the
the importance
importance of
With knowledge
could
have been
the fresh-water
fresh-water and
and estuarine
estuarine rearrearcould have
been produced
produced by
by other
other fac- both the
tors.
Three possibilities
possibilities were
were 11)) physio- ing areas,
tors. Three
areas, the
the question
question is
is raised
raised whether
logical
changes associated
abundance of
salmon in
logical changes
associatedwith
with smolting, the
the abundance
of fall
fall chinook salmon
2) changes
changes in
in abundance
abundance or availability
availability Sixes
Sixes River
environRiver can
can be
be enhanced.
enhanced. If
If environfood organisms,
organisms, or
3) changes in mental
of food
or 3)
conditions inin this
mental conditions
this river
river control
control
competition from other
other species
species of fish.
fish . the
competition
the number
number of long-term
long-term fresh-water
fresh-water
Judgments
potential physiological
physiological residents, then
Judgments about
about potential
any efforts
efforts to reduce
reduce
then any
problems were
possible without
withoutadad- temperature or increase flow
flow would
would
problems
were not possible
probably favor
studies. Studies
Studies are
are particularly
particularly probably
larger resident
resident populapopuladitional studies.
favor aa larger
needed of
of the smolting
needed
smolting process
process in these
these tion.
tion . Despite
Despite the small
small number
number of juvenjuvenfish and their salt-water adaptation iles
iles remaining
remaining for an
an extended
extended period
period in
in
under conditions
conditions that simulate
simulate regular
regular the
under
main river
river or
or tributaries
tributaries totobecome
become
the main
changesinin water
water velocity
changes
velocity and
and tempertemper- type-4 and
and type-S
type-S fish, they
they may
may have
have aa
ature, such as those experienced at high
high rate
rate of
of survival.
survival. Certainly
Certainly in the
the
mouth of
of the
mouth
the river.
changes future
river. Abrupt changes
Sixes River
River should
should be
be managed
managed
future Sixes
[(38]
38]
to improve
improve summer
summer conditions
conditions for
for rearrearthese two
two types
types by
by allowing
allowing vegavegaing
ing of these
tation to
to develop
develop along
along the
the streams
streams and
and
by
leaving buffer
logging
by leaving
buffer strips
strips in future logging
operations.
hatchery operation
operation simulating
simulating the
the
A hatchery
life history
history of
type-4 or
or type-5
type-S fish,
fish, but
of type-4
growing them
them to
to aa larger size than
growing
naturally
na~urally occurs,
occurs, would
would probably
probably also
help to
to increase
increase the run.
run. Such
Such aa rearing
rearing
help
program
would provide
provide for
for minimal
minimal ininprogram would
teraction between
between hatchery
hatchery and
wild
teraction
and wild
fish and
and would
would substantially
substantially increase
increase the
abundance ofof effective
the
abundance
effective migrants
migrants to
to the
ocean in
or as
as yearlings.
yearlings.
ocean
in autumn or
chinook salsalEnhancing
Enhancingthe
the run
run of
of fall chinook
mon by
of the
mon
by manipulations
manipulations of
the juvenile
juvenile
population
estuary may
population inin the
the estuary
may be
be diffidifficult but
but deserves
deserves further
further investigation.
investigation.
Of
particular concern
concern is the fate of
Of particular
juveniles that
remain in the
the estuary
estuary for
juveniles
that remain
only
the typetypeonly aa short
short time.
time. Adults
Adults with the
were scarce
scarce in relation
relation to
to
22 life
life history
history were
the many
many juveniles
juveniles that
potentially fell
fell
the
that potentially
into this
this group.
group. Evidence
Evidence presented
presented here
here
suggests that
Sixes River
not
suggests
that Sixes
River estuary
estuary is
is not
an unlimited environment,
environment, and
and that proproan
duction of fall
fall chinook
chinook salmon
salmon may
may be
be
duction
restricted by
limitations of
food and
and
restricted
by limitations
of food
space. If
large share
share of
individuals
space.
If a large
of the individuals
to fisheries
fisheries in
in the
the ocean,
ocean, or
contributing to
return to
to spawn,
spawn, are
are oblioblisurviving
surviving to
to return
gated
spend an
extended portion
gated to
to spend
an extended
portion of
life short
shortofofthe
theocean,
ocean,developing
developing
their life
hatchery releases
releases of
aa program
program for hatchery
of juvethe estuary
estuary in
in early
early summer
summer
niles into the
niles
would not
not be
be beneficial.
beneficial. Increasing
Increasing the
the
would
density
juvenile salmon
salmon in
the estuestudensity of
of juvenile
in the
ary may
may be
be detrimental
detrimental to growth
growth and
and
ary
survival of
b.o th hatchery
hatchery and
and wild fish.
fish.
survival
of both
Also, if size
size of
of juveniles
juveniles limits
limits survival
survival
Also,
the ocean,
ocean,
salmon in the
chinook salmon
of fall chinook
planting
the same
same size
size
planting hatchery
hatchery fish
fish at the
extended
as wild juveniles
juveniles may
may produce
produce extended
as
residence
the estuary
estuary and
and the
the resultresultresidence inin the
high dendening problems
problems associated
associated with
ing
with high
sity. However, if hatchery juveniles
planted
the estuary
estuary in
in early
early summer
summer
planted in the
were
fish, they
they
were much
much larger
larger than
than wild
wild fish,
might
quickly and
might acclimate
acclimate quickly
and enter
enter the
the
ocean
. This
ocean.
This would
would minimize
minimize competition
wild fish
fish and
and possibly
possibly allow
allow high
high
with wild
survival of hatchery
hatchery fish.
fish.
survival
Another
with the
Another manipulation
manipulation with
the wild
wild
in the
theestuary
estuaryseems
seems possible,
possible,
population in
facsince food
since
food appears
appearstoto be
be aa limiting factor
for growth
growth of
of juveniles
juveniles during
during peak
peak
tor for
population abundance.
Artificial feeding
population
abundance. Artificial
feeding
to maintain
maintain or
or improve
improve growth
juto
growth of
of juveniles might increase
veniles
increase the
the rearing
rearing capaccapacity
the estuary
estuary and
and the
the rate
rate of sursurity of the
vival of
those fish
fish emigrating
the
emigrating to
to the
of those
ocean during early
early summer.
summer.
ocean
Further research
research is needed
needed to
to measure
measure
the
importance of the
the estuary
estuary as
as aa stagstagthe importance
ing
area for
wild fall
fallchinook
chinooksalmon
salmon
ing area
for wild
before ocean
particularly need
need
before
ocean entry.
entry. We particularly
to
to measure
measure rearing
rearing capacity
capacity of
of the
the esestuary
terms of
survival to
tuary in
in terms
of survival
to maturity
maturity of
these fish. Because
Becauseofof our
our ability
ability to
to
measure population statistics of the
spawners returning
river and
and to
to
spawners
returningtoto the
the river
measure
abundance of
the
measure growth
growth and
and abundance
of the
juveniles
the estuary,
estuary, Sixes
Sixes River
River apapjuveniles in the
pears to
be ideal
ideal for
for continued
continuedresearch
research
pears
to be
on the population dynamics of fall
chinook salmon.
salmon.
[139]
39]
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[1423
42]
Acknowledgments
R. E.
E. Loeffel
Loeffel originally
originally stimulated
stimulated
Mr. R.
my
interest in
in chinook
chinooksalmon
salmon and
and gave
gave
my interest
me many
many valuable
valuable ideas.
ideas. I collectively
me
thank all
all Fish
Commission staff memmemFish Commission
thank
I
bers who
chibers
who have
have worked
workedon
on the
the fall
fall chinook
began in
nook ecology
ecology project
project since
since itit began
1964.
Messrs. P.
P. H. Reed,
Reed, A.
McGie,
1964. Messrs.
A. M. McGie,
JJ.. J.
J . Bender,
Bender, R.
R. G.
G. Montagne,
Montagne,
R. JJ.. Roll, R.
Jensen, R.
R. A.
A. Stein,
R.
Stein,
I-I. Jensen,
R. E.
E. Bender, H.
N..
T. E.
Cummings, and
late R.
R. N
E. Cummings,
and the
the late
Breuser
important contributions.
contributions.
Breuser made
made important
Orris Smith,
Smith, Port
Port Orford
Orford commercommerMr. Orris
cial
fisherman provided
provided historical
historical backbackcial fisherman
ground on
on local
local salmon
salmon runs.
runs. Sandra
ground
Smith and
and Joanne
Joanne Nelson
Nelson assisted
assisted with
Smith
with
the data
data analysis.
analysis. Linda
Linda Karlik
Karlik prepared
prepared
the
the figures.
figures . My
Mywife,
wife,Sandra,
Sandra, provided
provided
the
assistance in scale
scale reading
reading and
and
technical assistance
data analysis.
analysis.
am indebted
indebted to
to my
my major
major professor,
professor,
I am
Dr. J.
Hall, for
for his
his guidance
guidance and
and enDr.
J . D.
D. Hall,
couragement
during my
couragement during
my graduate
graduate study
study
and
of the thesis.
and preparation
preparation of
thesis. Dr.
Dr. C.
C. E.
E.
Warren, Mr.
Mr. A.
A. M.
Warren,
M. McGie,
McGie, Mr.
Mr. R.
R. E.
Loeffel, Dr.
Dr. W.
and Dr.
Loeffel,
W . G.
G. Pearcy,
Pearcy, and
Dr. A.
A.
W.
W . Pritchard
Pritchard reviewed
reviewed the
the thesis.
thesis.
[[43]
43]