United
States
Environmental
Protection
Agency
EPA­
910­
D­
01­
005
May
2001
Issue
Paper
5
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
on
Salmonids
Prepared
as
Part
of
EPA
Region
10
Temperature
Water
Quality
Criteria
Guidance
Development
Project
Dale
A.
McCullough,
Colum
bia
River
Inter­
T
ribal
Fish
Commission
Shelley
Spalding,
U.
S.
Fish
and
Wildlife
Service
Debra
Sturdevant,
Oregon
Department
of
Environmental
Quality
Mark
Hicks,
Washington
Department
of
Ecology
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
Contents
ABSTRACT
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1
INTRODUCTION
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2
SUMMARY
OF
THERMAL
REQUIREMENTS
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3
What
are
the
thermal
requirements
for
incubation
and
early
fry
development?
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3
What
are
the
thermal
requirements
for
growth?
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3
What
are
the
thermal
requirements
for
smoltification?
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6
What
are
the
thermal
requirements
for
swimming
speed?
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8
What
are
the
thermal
requirements
for
migration
to
spawning?
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9
What
are
the
thermal
requirements
for
adult
holding
and
spawning?
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11
What
are
lethal
temperature
effects?
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12
What
conclusions
can
you
draw
for
anadromous
salmonids
and
coastal
cutthroat
and
rainbow
trout?
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13
What
conclusions
can
you
draw
for
bull
trout
and
Dolly
Varden?
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17
What
conclusions
can
you
draw
for
other
salmonids?
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18
SUPPORTING
DISCUSSION
AND
LITERATURE
 
GENERAL
ISSUES
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19
Laboratory
and
Field
Studies
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19
What
are
the
advantages
and
disadvantages
of
laboratory
and
field
data?
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19
If
our
most
precise
understanding
of
thermal
effects
is
from
laboratory
tests,
what
methods
can
be
used?
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21
Potential
for
Variation
Among
Stocks
or
Species
of
Salmonids
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23
Is
there
enough
significant
genetic
variation
among
stocks
or
among
species
to
warrant
geographically
specific
water
temperature
standards?
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23
Are
there
evolutionary
differences
among
salmonid
species
in
the
Pacific
Northwest?
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24
What
are
the
major
differences
in
thermal
tolerance
among
and
within
important
families?
24
What
is
the
variation
in
thermal
response
within
a
species?
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26
Is
there
significant
genetic
flexibility
within
a
stock
that
would
allow
for
adaptation
to
thermal
regimes?
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27
Besides
survival,
what
other
key
biotic
responses
influenced
by
temperature
vary
among
stocks?
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27
Growth.
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28
Swimming
speed.
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29
SUPPORTING
DISCUSSION
AND
LITERATURE
 
SUBLETHAL
EFFECTS
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30
Incubation
and
Early
Fry
Development
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30
Which
temperatures
provide
optimum
conditions
for
incubation
and
early
fry
development
in
the
following
species?
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30
Chinook
salmon.
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30
Coho
salmon.
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33
Chum
salmon.
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34
Pink
salmon.
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34
Sockeye
salmon.
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35
Steelhead.
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36
Nonanadromous
rainbow
trout.
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36
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
Cutthroat
trout.
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37
What
are
the
conclusions
for
incubation
requirements?
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38
Growth
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38
For
growth,
what
are
the
demands
for
energy
and
how
is
the
balance
determined
by
temperature?
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38
Why
is
it
important
to
be
concerned
with
growth
rate,
product
ion,
and
fish
density?
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39
What
is
the
optimum
range
or
optimum
temperature
for
growth
of
various
salmonids?
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40
Chinook.
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40
Sockeye.
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41
Steelhead.
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42
What
more
is
specifically
known
about
growth
rearing
requirements
of
rainbow
trout?
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42
What
is
the
relationship
between
growth
temperatures
and
other
physiological
responses?
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44
What
are
temperature
feeding
limits
for
salmonids?
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45
How
is
feeding
rate
affected
by
acclimation
temperature?
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46
What
are
temperature
growth
limits
for
salmonids?
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46
How
does
food
availability
affect
growth
of
salmonids
at
different
temperature
exposures?
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47
Is
there
evidence
for
food
limitation
in
natural
streams?
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48
Can
growth
rates
be
predicted
under
field
conditions
using
thermal
history
identified
under
laboratory
conditions?
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.
49
Has
acclimation
to
a
temperature
higher
than
the
mean
of
a
diel
cycle
been
demonstrated?
.
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.
51
Are
there
seasonal
differences
in
growth
rates
not
related
to
temperature?
.
.
.
.
.
.
.
.
.
.
51
What
research
seems
to
best
describe
the
influence
of
fluctuating
temperature
on
growth?
.
.
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.
52
What
is
the
range
of
laboratory
growth
rates
under
fluctuating
temperature
vs.
constant
temperature?
.
.
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54
Smoltification
.
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.
57
How
is
smoltification
measured?
.
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.
.
57
What
is
physiological
stress
and
at
what
temperatures
does
it
occur
in
salmonids?
.
.
.
.
57
What
are
the
seasons
for
passage
of
smolts
of
common
anadromous
species
and
how
would
this
information
be
used?
.
.
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.
.
58
What
are
heat
shock
proteins
and
what
do
they
indicate?
.
.
.
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.
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.
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.
58
What
temperature
range
is
recommended
for
reducing
physiological
stress?
.
.
.
.
.
.
.
.
.
59
Why
might
it
be
advisable
to
use
naturally
reared
vs.
hatchery­
reared
salmonids
to
measure
physiological
status?
.
.
.
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.
.
60
How
does
physiological
status
of
smolting
salmon
change
seasonally?
.
.
.
.
.
.
.
.
.
.
.
.
.
60
How
does
photoperiod
influence
growth
rate
and
subsequent
saltwater
readiness
of
smolts?
.
.
.
.
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.
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.
.
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.
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.
.
61
Are
smolts
affected
by
high
temperatures
during
migration?
.
.
.
.
.
.
.
.
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.
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.
.
.
62
Are
smolts
subject
to
cumulative
stresses
from
thermal
exposure?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
62
What
temperatures
are
required
to
inhibit
smoltification
in
steelhead
and
salmon?
.
.
.
.
.
62
What
temperatures
are
required
to
reverse
smoltification
in
steelhead?
.
.
.
.
.
.
.
.
.
.
.
.
.
64
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
Can
incubation
temperature
affect
smolt
emigration
timing?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
64
What
river
temperatures
are
associated
with
peaks
in
migration?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
64
How
do
freshwater
and
ocean
temperatures
affect
time
of
ocean
entry?
.
.
.
.
.
.
.
.
.
.
.
65
What
is
the
role
o
f
temperature
in
migratory
respo
nse
and
seawater
adaptation?
.
.
.
.
.
.
65
How
can
multiple
stresses
during
the
smolting
phase
be
reduced?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
66
Swimming
Speed
.
.
.
.
.
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.
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.
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.
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.
.
.
.
.
.
66
How
is
swimming
speed
measured?
.
.
.
.
.
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.
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.
.
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.
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.
.
.
.
.
.
.
.
.
.
.
.
66
At
what
swimming
speeds
do
metabolic
transitions
occur?
.
.
.
.
.
.
.
.
.
.
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.
.
.
.
.
.
.
.
.
.
67
Why
is
swimming
speed
vital
to
adults
during
migration?
.
.
.
.
.
.
.
.
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.
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.
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.
.
.
.
.
.
.
.
.
67
Why
is
swimming
speed
vital
to
smolts
during
migration?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
68
How
does
temperature
affect
juvenile
swimming
speed?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
69
How
do
temperature
and
oxygen
jointly
affect
juvenile
swimming
speed?
.
.
.
.
.
.
.
.
.
.
.
69
How
are
physiological
optimum,
growth
optimum,
preferred
temperature,
swimming
maximum,
and
metabolic
scope
derived?
.
.
.
.
.
.
.
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.
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.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
69
How
can
allocation
of
energy
to
metabolism
and
swimming
be
used
to
interpret
fitness
and
resistance
to
disease?
.
.
.
.
.
.
.
.
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.
.
.
.
.
.
.
.
70
How
do
temperature,
light
intensity,
and
photoperiod
influence
swimming
speed?
.
.
.
.
70
How
do
fish
size
and
acclimation
temperature
affect
swimming?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
71
Can
disease
affect
swimming
speed?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
71
What
is
known
about
swimming
speed
for
three
species
of
char?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
71
Can
swimming
act
as
an
indicator
of
sublethal
stress?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
71
How
are
adult
swimming
speeds
and
migration
rate
related?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
72
Adult
Migration
to
Reproduction
.
.
.
.
.
.
.
.
.
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.
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.
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.
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.
.
.
.
.
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.
.
.
.
.
.
.
.
.
.
.
.
.
.
73
What
temperatures
are
asso
ciated
with
migration?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
73
How
can
stress
during
migration
affect
later
reproductive
success
in
salmonids?
.
.
.
.
.
.
75
What
temperatures
are
recommended
for
holding?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
75
Can
temperature
affect
viability
of
gametes
developing
in
adults?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
76
How
is
survival
of
prespawning
adults
affected
by
water
temperature?
.
.
.
.
.
.
.
.
.
.
.
.
.
81
What
temperature
ranges
are
associated
with
the
adult
spawning
period?
.
.
.
.
.
.
.
.
.
.
.
81
What
temperatures
or
thermal
regimes
are
required
to
initiate
spawning?
.
.
.
.
.
.
.
.
.
.
.
82
Conclusions
for
spawning.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
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.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
83
SUPPORTING
DISCUSSION
AND
LITERATURE
 
LETHAL
EFFECTS
.
.
.
.
.
84
What
is
the
utility
of
UILT
data
and
how
has
it
been
applied?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
84
Are
there
potential
weaknesses
in
reliance
on
MWAT?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
85
How
can
UILT
data
be
evaluated
against
UUILT
data?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
86
How
can
prolonged
exposure
to
cyclic
temperatures
be
evaluated?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
87
SUPPORTING
DISCUSSION
AND
LITERATURE
 
SUBLETHAL
AND
LETHAL
EFFECTS
FOR
NATIVE
CHAR,
REDBAND
TROUT,
AND
CUTTHROAT
TROUT
SPECIES
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
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.
.
.
.
.
.
.
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.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
89
What
are
the
thermal
requirements
of
bull
trout
and
Dolly
Varden?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
89
Incubat
ion.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
89
Growth.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
91
Migration.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
91
Spawning.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
91
What
are
the
thermal
requirements
for
Lahontan
cutthroat
trout?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
92
Growth.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
92
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
Thermal
stress
 
heat
shock
proteins.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
92
Occurrence.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
93
Lethal
effects.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
93
What
are
the
thermal
requirements
for
westslope
cutthroat
trout?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
94
Incubat
ion
and
egg
survival.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
94
Growth.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
94
Spawning.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
94
Occurrence.
.
.
.
.
.
.
.
.
.
.
.
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94
What
are
the
thermal
requirements
for
redband
trout?
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94
Growth
and
feeding.
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94
Metabolic
activity
and
swimming
speed.
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95
Occurrence.
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95
Lethal
effects.
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95
LITERATURE
CITED
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96
1
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
Issue
Paper
5
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
Region
10
Temperature
Water
Quality
Criteria
Guidance
Development
Project
Dale
A.
McCullough,
Shelley
Spalding,
Debra
Sturdevant,
and
Mark
Hicks
ABSTRACT
The
chief
objective
of
this
paper
is
to
provide
a
literature
review
of
the
role
temperature
exerts
on
the
physiology
of
various
salmonids.
The
fish
are
affected
as
species
and
within
the
stages
of
their
life
history.
The
thermal
environment,
perhaps
more
than
any
other
aquatic
habitat
feature,
influences
the
distribution,
health
and
survival
of
our
native
salmonids.
Temperature
tolerances
for
salmonid
species
typically
refer
to
effects
of
temperature
on
an
individual.
Because
we
are
interested
in
sustainable
populations
of
salmonids,
this
paper
also
reviews
information
on
the
optimal
or
preferred
ranges
of
temperatures
that
will
be
needed
to
promote
long­
term
survival,
growth,
and
reproductive
success.

Thermal
stress
occurs
when
a
temperature
or
a
change
in
temperature
produces
a
significant
change
to
biological
functions
leading
to
decreased
likelihood
of
survival.
Thermal
stress
can
lead
to
lethal
effects
either
immediately,
in
a
period
of
days,
or
even
weeks
or
months
from
the
onset
of
the
elevated
temperature.
Thermal
stress
can
also
result
in
"
sublethal"
or
indirect
effects
resulting
in
death
or
reduced
fitness
that
impairs
processes
such
as
growth,
spawning,
smoltification,
or
swimming
speed.
Metabolic
processes
are
directly
related
to
temperature,
and
the
metabolic
rat
e
increases
as
a
function
of
temperature.
Fish
are
metabolically
efficient
and
most
likely
to
thrive
within
the
preferred
range
of
temperatures.

Different
species
of
salmonids
have
evolved
to
utilize
different
thermal
regimes,
although
there
is
much
overlap
in
their
utilization
of
these
regimes.
Anadromous
salmonids
and
coastal
cutthroat
and
rainbow
trout
tend
to
have
similar
temperature
requirements;
however,
where
multiple
species
and
life
stages
are
present,
temperature
criteria
need
to
protect
the
most
sensitive
species
and
life
history
stage.
For
this
guild,
maximum
growth
and
swimming
speed
occur
at
55.4­
68
°
F
(
13­
20
°
C)
under
satiation
feeding;
reduced
ATPase
levels
are
experienced
at
temperatures
as
low
as
51.8­
55.4
°
F
(
11­
13
°
C),
potentially
resulting
in
delayed
or
ineffective
smoltification;
adult
migration
may
be
blocked
at
69.8­
73.4
°
F
(
21­
23
°
C);
and
temperatures
of
42.8­
50
°
F
(
6­
10
°
C)
or
lower
during
incubation
result
in
maximum
survival
and
size
at
emergence.
Bull
trout
have
lower
temperature
requirements
than
other
salmonids
with
optimal
incubation
occurring
at
35.6­
42.8
°
F
(
2­
6
°
C),
spawning
being
initiated
as
temperatures
drop
below
48.2
°
F
(
9
°
C),
and
the
maximum
growth
rate
at
satiation
feeding
occurring
at
60.8
°
F
(
16
°
C).
For
other
salmonids
such
as
redband
trout,
westslope
cutthroat
trout,
and
mountain
whitefish,
little
information
is
available
on
the
effect
s
of
temperature
on
their
physiology.
2
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
INTRODUCTION
The
distribution,
health,
and
survival
of
our
native
fish
species
are
inextricably
linked
to
the
thermal
environment.
Temperature,
perhaps
more
than
any
other
environmental
parameter,
greatly
affects
the
status
of
fish
and
other
aquatic
life.
With
respect
to
thermal
effects,
lethal
temperatures
do
occur
in
the
field
and
can
be
locally
problematic
in
defining
usable
and
unusable
habitat.
Sublethal
effects
of
temperature
determine
the
overall
well­
being
and
patterns
of
abundance
of
our
native
fish
populat
ions.
Temperature
exerts
its
control
through
its
effect
on
the
physiology
of
the
individual
species
and
their
life
stages.
In
addition,
individuals
within
a
species
population
vary
in
their
responses
(
e.
g.,
lethal,
growth)
to
temperature,
generally
according
to
a
bell­
shaped
distribution.
As
species
individually
or
relative
to
one
another
experience
temperatures
outside
their
physiological
optimum
range,
the
mix
of
species
present
in
any
given
waterbody
may
drastically
change.
Aside
from
direct
mortality
caused
by
very
high
temperatures,
temperature
influences
the
abundance
and
well­
being
of
organisms
by
controlling
their
metabolic
processes.
Every
species,
including
disease
organisms,
has
optimal
metabolic
ranges.
Community
composition
is
shaped
by
the
level
of
numerous
components
of
the
habitat
system,
including
temperature,
food,
water,
light,
substrate,
and
so
on,
each
of
which
can
provide
optimal
or
suboptimal
conditions.
Temperature
is
one
of
the
single
most
influential
determinants
of
habitat
quality
and
can
also
act
synergistically
with
other
habitat
elements.

Temperature
through
its
effect
on
physiology
influences
the
ability
of
fish
to
grow,
reproduce,
compete
for
habitat,
and
escape
predators.
This
issue
paper
examines
the
role
of
temperature
in
the
physiology
of
the
salmonids
native
to
t
he
Pacific
Northwest,
and
the
importance
of
lethal
temperature
effects
compared
with
various
types
of
sublethal
effects
in
controlling
the
survival
and
health
of
native
fishes.

For
further
information
on
the
effects
of
temperature
on
salmonids,
we
suggest
you
refer
to
both
the
Behavior
and
Temperature
Interaction
issue
papers
in
this
series.
This
issue
paper
is
drawn
heavily
from
existing
extensive
reviews
of
thermal
effect
literature
(
Berman
1998,
EPA
and
NMFS
1971,
Hicks
1999,
2000,
McCullough
1999,
ODEQ
1994)
and
is
intended
to
extract
from
this
large
body
of
literature
the
key
documents
illustrating
various
concepts
and
effects.
For
additional
guidance
to
the
literature
on
thermal
effects,
we
recommend
starting
from
these
references.

The
intention
of
t
his
paper
is
to
review
physiological
effects
of
temperature
regimes
for
all
salmonids.
However,
the
authors
acknowledge
the
scarcity
of
relevant
bull
trout
information
and
have
avoided
including
observations
or
case
studies
that
are
difficult
to
extrapo
late,
as
is
the
case
with
much
of
the
bull
trout
temperature
literature.
In
cases
where
there
is
information
available
on
a
closely
related
charr
species,
that
information
may
be
included.

In
the
following
questions
and
answers,
we
first
summarize
thermal
requirements
for
salmonid
incubation
and
early
fry
development,
growth,
smoltification,
swimming
speed,
migration
to
spawning,
and
adult
holding
and
spawning,
and
discuss
lethal
effects.
Then
we
present
detailed
documentation
and
references.
3
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
SUMMARY
OF
THERMAL
REQUIREMENTS
What
are
the
therm
al
requirem
ents
for
incu
bation
an
d
early
fry
development?

During
incubation
and
early
fry
development,
salmonid
embryos
and
young
fish
have
different
habitat
requirements
from
those
of
spawning
adults,
even
though
the
adult­
selected
spawning
site
is
the
incubation
environment
for
the
progeny.
During
incubation,
water
temperature
affects
t
he
rate
of
embryo
and
alevin
development,
the
amount
of
dissolved
oxygen
in
the
water,
and,
to
a
significant
extent,
the
survival
of
early
fry
(
Bjornn
and
Reiser
1991).
Within
an
acceptable
range,
the
higher
the
temperature
is
the
faster
the
rate
of
development
will
be
and
the
shorter
the
incubation
period
and
time
to
emergence
(
Beacham
and
Murray
1990).

The
effects
of
water
temperature
in
regulating
developmental
rates
of
incubating
eggs
are
well
documented
(
Hicks
2000,
McCullough
1999).
Temperatures
from
39.2
to
53.6
°
F
(
4­
12
°
C)
tend
t
o
produce
relatively
high
survival
to
hatching
and
emergence,
with
approximately
42.8­
50
°
F
(
6­
10
°
C)
being
o
ptimum
for
most
salmonid
species.
However,
although
salmonids
should
avoid
temperatures
that
are
too
cold
or
too
warm
during
initial
stages
of
incubation,
the
entire
thermal
history
(
including
accumulation
of
degree
days)
during
incubation
is
of
great
importance
to
ensure
proper
emergence
timing.
That
is,
a
thermal
regime
that
cools
rapidly
from
53.6
°
F
(
12
°
C)
and
achieves
low
winter
temperatures
(
according
to
natural
cooling
processes
and
rates)
is
essential
for
acquiring
the
necessary
thermal
units
to
ensure
proper
emergence
timing
and
high
egg
survival.
Unless
water
releases
from
dams
alter
winter
thermal
regimes
in
egg
incubation
habitat,
it
is
assumed
that
controlling
summer
rearing
temperatures
(
maximum
and
diel
fluctuation)
will
also
provide
proper
winter
temperatures
during
incubation.
Management
"
control"
of
summer
temperatures
means
taking
those
actions
that
would
restore
the
thermal
regimes
consistent
with
the
system
potential
for
the
stream.

Char
can
be
characterized
as
a
stenothermal
species
because
they
require
a
narrow
range
of
cold
temperatures
to
rear
and
reproduce
and
may
thrive
in
wat
ers
too
cold
for
other
salmonid
species
(
Balon
1980).
The
literature
suggests
t
hat
the
optimum
water
temperature
range
for
bull
trout
and
Dolly
Varden
incubation
occurs
just
below
the
optimal
range
for
the
other
salmonids
native
to
the
Pacific
Northwest.

Native
stocks
of
salmon,
trout,
and
char
are
closely
tied
to
t
heir
natal
streams
and
have
evolved
with
natural
fluctuations
in
stream
temperatures
and
other
environmental
variables.
Some
streams
may
have
winter
temperatures
that
are
lower
than
the
minimum
recommended
as
optimal
for
most
salmonid
species
ot
her
than
char;
however,
eggs
are
usually
able
to
develop
normally
because
spawning
and
initial
embryo
development
occur
when
temperatures
are
in
the
suitable
range.
The
presence
of
groundwater
inflows
close
to
spawning
areas
also
helps
ameliorate
seasonal
temperature
extremes
that
might
be
harmful
to
developing
embryos.

What
are
the
thermal
requirements
for
growth?

Growth
is
one
of
the
most
sensitive
indicators
of
overall
fish
health
and
is
vulnerable
to
changes
in
basic
environmental
conditions
such
as
temperature.
Unless
a
fish
can
grow
it
cannot
complete
its
life
functions.
For
example,
a
fish
must
reach
a
sufficient
size
at
hatching
or
4
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
emergence
to
have
a
high
likelihood
of
survival.
Size
attained
at
the
time
of
hatching
or
emergence
partially
depends
on
egg
size,
which
in
turn
is
related
to
adult
size
and
nutritional
status
at
spawning.
If
growth
rates
are
too
low
during
the
summer
rearing
period,
body
fat
is
not
sufficient
to
sust
ain
a
fish
during
the
winter
rearing
period
(
Hokanson
1977).
If
the
size
during
overwintering
is
too
small
or
the
growth
rate
prior
to
emigrat
ion
is
too
low,
smolt
size
will
be
insufficient
to
ensure
successful
transition
to
the
marine
environment
(
Folmar
et
al.
1982).
Growth
rates
during
egg
incubation
are
affected
by
temperature
in
the
gravel.
In
streams
with
low
winter
temperatures
(
e.
g.,
<
42.8
°
F
[
6
°
C]),
feeding
and
total
fish
activity
tend
to
be
very
low,
and
consequently
growth
is
minimal.

Growth
rates
of
juvenile
fish
during
summer
are
used
as
a
convenient
means
of
monitoring
the
thermal
impacts
of
most
freshwater
environments.
Riparian
canopy
removal
or
channel
widening,
which
lead
to
increased
maximum
water
temperatures
during
summer,
are
also
associated
with
lower
minimum
winter
temperatures
as
well
as
increased
diel
fluctuations
in
both
seasons.
Optimum
growth
temperatures
for
a
variety
of
salmonids,
many
of
which
are
native
to
the
Pacific
Northwest,
are
listed
in
Table
1.
These
optimum
temperatures
for
feeding
at
full
ration
range
from
53.6
to
68
°
F
(
12­
20
°
C).
Because
food
availability
in
the
field
typically
provides
less
than
satiation
feeding,
optimum
growth
temperatures
in
the
field
can
be
substantially
reduced
(
Elliott
1981).

Table
1.
Selected
growth
optima
for
salmonids
determined
from
feeding
on
full
rations
Species
Optimum
growth
temperature
(
°
C)
Reference
Chinook
(
Oncorhynchus
tshawytscha)
15
Banks
et
al.
(
1971)
(
as
cited
by
Garling
and
Masterson
1985)
17
Clarke
and
Shelbourn
(
1985)
19
Brett
et
al.
1982
20
Marine
(
1997)
Sockeye
(
Oncorhynchus
nerka)
15
Brett
et
al.
1969
Coho
(
Oncorhynchus
kisutch)
15
Everson
(
1973,
as
cited
by
Sullivan
et
al.
2000)
Rainbow
trout
(
Oncorhynchus
mykiss)
17.2­
18.6
Hokanson
et
al.
(
1977)

16.5
Wurtsbaugh
and
Davis
(
1977)
15
Grabowski
(
1973)
15
Railsback
and
Rose
(
1999)
(
redband
trout)
20
Sonski
(
1983b)
Brook
trout
(
Salvelinus
fontinalis)
12.4­
15.4
McCormick
et
al.
1972
Lake
trout
(
Salvelinus
namaycush
12.5
Edsall
and
Cleland
(
2000)

Brown
trout
(
Salmo
trutta)
13.9
Elliott
and
Hurley
(
1999)
13.1
Elliott
et
al.
(
1995)
Atlantic
salmon
(
Salmo
salar)
18
Siemien
and
Carline
(
1991)
Arctic
char
(
Salvelinus
alpinus)
14
Jobling
(
1983)
15.1
Larsson
and
Berglund
(
1997)
European
grayling
(
Thymallus
thymallus)
17.3
Mallet
et
al.
(
1999)
5
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
Bull
trout
(
Salvelinus
confluentus)
12­
16
McMahon
et
al.
(
1999)

Optimum
growth
temperature
is
that
temperature
which
pro
vides
the
most
favorable
conditions
for
growth.
Other
biological
performances
such
as
feeding
rate
and
conversion
efficiency
may
have
other
optimum
temperatures.
For
example,
feeding
rate
and
conversion
efficiency
both
are
influenced
by
temperature,
but
each
can
have
a
slightly
different
optimum
temperature.
Because
growth
rate
is
more
directly
linked
to
energy
assimilated
(
the
result
of
the
combination
of
feeding
rate
and
conversion
efficiency),
it
seems
most
appropriate
to
emphasize
growth
rate
as
a
key
biological
performance
indicator
of
the
thermal
environment
quality
rather
than
the
other
two
performances.

Growth
rate
is
a
function
of
temperature
but
also
of
food
availability
(
Elliott
1981,
Elliott
1994).
Food
availability
in
the
field
is
normally
thought
to
be
substantially
less
than
that
needed
to
provide
satiation
feeding.
Consequently,
if
stream
productivity
restricts
salmonid
feeding
to
levels
less
than
satiation,
then
lower
temperatures
are
required
to
ensure
optimum
growth
rates.
Although
laboratory­
derived
temperature
growth
optima
are
probably
adequately
defined
for
various
feeding
levels,
an
absolute
growth
rate
in
the
labo
ratory
may
not
be
matched
in
the
field
given
the
differences
in
food
quality.
In
hatchery
culture
situations,
satiation
feeding
on
hatchery
diets
can
produce
excessive
accumulation
of
lipid
(
i.
e.,
hatchery
fish
are
often
obese
compared
with
wild
fish).
This
is
not
to
say
that
optimum
growth
temperatures
are
not
a
useful
biological
index
to
temperatures
providing
healthful
co
nditions
for
salmonids
residing
in
the
center
of
their
distribution
in
the
field.
Instead
it
indicates
that
art
ificially
increasing
temperature
in
the
field
above
optimum
produces
a
relative
reduction
in
growth
rate.
Also,
in
order
to
provide
the
greatest
population
production
capacity
(
contributing
to
biomass,
abundance,
and
fecundity
 
all
indicators
of
fitness
and
population
long­
term
viability),
it
is
important
to
provide
the
full
range
of
natural
potential
temperature
longitudinally.
This
means
very
cold
headwaters,
cold
midreaches,
and
cold/
cool
lower
reaches.
This
will
produce,
in
general,
lower
than
optimum
growth
in
headwaters,
optimum
growth
in
midreaches,
and
lower
than
optimum
growth
downstream.
Eliminating
cold­
water
habitats
upstream
shrinks
suitable
habitat,
converts
more
habitat
to
suboptimal
growth
zones,
and
reduces
potential
production.

Optimum
temperature
can
have
another
connotation.
When
we
consider
the
effects
of
temperature
at
any
given
life
stage,
multiple
performances
must
often
be
achieved.
For
example,
if
the
highest
growth
rate
were
produced
only
under
temperatures
so
high
that
a
large
portion
of
the
population
would
die
from
disease,
the
optimum
temperature
for
satisfying
overriding
needs
(
e.
g.,
sustainability)
of
the
population
might
be
closer
to
the
optimum
for
protection
against
disease.
If
the
disease
resistance
temperature
optimum
is
so
low
that
growth
and
reproduction
are
low,
the
optimum
would
have
to
lie
in
a
more
intermediate
positio
n.
However,
as
previously
described,
most
key
biological
performances
are
well
correlated
and
have
similar
optima.
Preferred
temperatures,
optimum
growth
temperatures,
and
high
disease
resistance
from
common
warm­
water
diseases
(
e.
g.,
furunculosis,
columnaris)
tend
to
be
similar
(
Jobling
1981).
Consequently,
we
are
able
to
survey
the
literature
about
optimum
growth
temperatures,
compare
these
temperatures
with
optima
for
other
performances
such
as
disease
resistance
or
swimming
ability,
and
find
a
temperature
range
that
would
satisfy
growth
objectives
but
also
meet
other
key
needs
influencing
survival.
6
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
The
physiological
optimum
is
the
temperature
under
which
a
number
of
physiological
functions,
including
growth,
swimming,
spawning,
and
heart
performance,
are
optimized.
Physiological
optimum
temperature
can
be
estimated
as
the
average
of
growth
optimum
and
final
preferendum
(
Armour
1990,
McCormick
and
Wegner
1981).
Physiological
optimum
has
been
used
as
the
basis
for
estimates
of
suitable
temperatures
for
fish
survival
(
NAS
1972).
Because
growth
optima
heavily
influence
the
physiological
optimum,
optimum
growth
is
intimately
linked
with
temperatures
producing
high
survival.
Optimum
growth
during
the
warm,
maximum
growth
season
(
generally
summer)
is
then
linked
with
high
survival.
Optimum
growth
depends
on
food
availability.
As
food
availability
declines,
t
he
temperature
producing
optimum
growth
also
is
lowered.
The
growth
optimum
is
also
found
near
the
temperature
for
maximum
metabolic
scope
(
Brett
1952).
The
greater
the
scope,
the
greater
the
ability
of
fish
to
divert
energy
to
either
somatic
growth
or
gamete
production.
Obviously,
maximizing
growth
is
not
desirable
at
all
times.
For
example,
rapid
egg
development
throughout
incubation
would
result
in
improper
emergence
timing,
and
rapid,
early
juvenile
growth
would
result
in
early
smolt
emigration
(
Holtby
et
al.
1989).
On
the
other
hand,
inadequate
size
attained
by
smolts
leads
to
poor
ocean
survival
(
Metcalfe
and
Tho
rpe
1992).
These
contrasting
demands
imply
that
it
is
important
to
achieve
high
growth
rates
during
the
growth
season
and
to
minimize
the
loss
of
energy
during
the
remainder
of
the
year.
At
a
stream
system
scale,
this
maximization
of
growth
rates
would
occur
only
in
the
center
of
the
geographic
distribution
of
the
species
according
to
the
natural
potential
of
the
system
to
produce
the
corresponding
thermal
regime.
Exceeding
the
temperature
producing
optimum
growth
(
e.
g.,
in
the
center
of
distribution)
results
in
diminished
growth
rate,
increased
disease
incidence,
and
increased
sublethal
stress
(
see
Elliott
1981).

Recommendation
of
temperatures
for
protection
of
fish
species
must
emphasize
high
survival
by
life
stage
(
e.
g.,
egg,
juvenile,
smolt,
adult).
High
ability
to
perform
all
key
life
functions
(
e.
g.,
feeding,
growth,
swimming,
migration,
reproduction,
mate
selection)
is
also
an
important
link
to
fitness
and
population
viability.

The
general
form
of
the
relationship
between
growth
and
temperature
is
a
hump­
shaped
(
symmetrical
or
skewed)
curve
in
which
an
intermediate
temperature
produces
optimum
growth,
and
temperatures
both
higher
and
lower
result
in
declines
in
growth
rate
t
o
zero.
Upper
incipient
lethal
temperatures
(
UILT)
can
obviously
result
in
zero
growth
when
mortality
occurs.
However,
growth
rates
at
temperatures
above
the
optimum
can
plummet
rapidly
to
zero
with
increasing
temperature
and
reach
zero
at
temperatures
less
than
the
UILT
(
Brett
et
al.
1982).
Growth
responses
can
also
be
fairly
broad
in
the
vicinity
of
the
optimum
so
that
an
optimum
zone
might
be
described.
Again,
temperatures
above
the
optimum
zone
can
result
in
sharply
declining
growth
rates,
so
caution
is
warranted
in
setting
criteria
at
the
upper
end
of
the
optimum
zone.

What
are
the
thermal
requirements
for
smoltification?

Smoltification
occurs
in
juvenile
fish
as
they
prepare
to
move
from
a
freshwater
habitat
to
a
marine
habitat.
The
parr
to
smolt
transformation
involves
changes
in
activity,
coloration,
shape,
and
physiological
tolerance
to
seawater.
The
ultimate
biological
goal
of
smoltification
is
to
increase
survival
of
smolts
upon
entering
the
marine
environment.

Effects
o
f
temperature
on
the
smolting
process
have
been
studied
in
terms
of
changes
in
7
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
growth,
condition
facto
r,
body
silvering,
body
moisture
and
lipid
content,
salinity
tolerance,
and
gill
Na­
K­
ATPase
activities
(
Johnston
and
Saunders
1981).
High
temperatures
during
the
smolt
phase
can
result
in
outright
lethality,
premature
smolting,
blockage
of
seaward
migration,
desmoltification,
shifts
in
emigration
timing
resulting
in
decreased
survival
in
the
marine
environment,
or
other
stresses
detrimental
to
fitness.

Salmon
and
steelhead
during
the
smolt
phase
have
various
degrees
of
sensitivity
to
elevated
water
temperatures
(
e.
g.,
Adams
et
al.
1973,
Zaugg
and
McLain
1976,
Hoar
1988).
Temperatures
that
have
been
reported
in
the
literature
as
impairing
smoltification
range
from
approximately
53.6­
59
°
F
(
12­
15
°
C)
or
more
(
Table
2).
St
eelhead
appear
to
be
most
sensitive
during
this
stage,
as
opposed
to
their
greater
resistance
to
high
temperatures
during
other
juvenile
stages.
Although
some
bull
trout
do
enter
the
nearshore
marine
environment,
little
is
known
about
their
smoltification
process
and
sensitivities.
Smolt
migration
during
periods
of
high
water
temperatures
can
cause
inhibition
or
reversal
of
the
smoltification
process
or
a
termination
of
migration
(
i.
e.,
return
to
freshwater
residency
for
an
additional
year).
Qualitatively,
this
effect
can
be
linked
to
changes
in
visual
or
physiological
indicators,
such
as
gill
Na+­
K+
ATPase
activity.
These
qualitative
indices,
in
turn,
are
linked
to
a
lowered
survival
of
smolts
when
subjected
to
seawater
challenges.
Lowered
survival
is
associated
with
inability
to
osmoregulate
due
to
altered
physiological
status.
Because
sensitivity
of
smolts
to
elevated
mainstem
temperatures
varies
by
species
and
because
species
and
stocks
vary
in
migration
timing,
the
significance
of
effects
of
mainstem
temperatures
on
smolt
ification
and
survival
require
considerat
ion
of
thermal
regime
during
the
migration
period
by
species.

Table
2.
Temperatures
that
have
been
linked
to
impairment
of
smoltification,
ability
of
smolts
to
migrate,
or
survival
during
smolt
migration
Species
Temperature
(
°
C)
threshold
for
impairment
Reference
Chinook
12
Wedemeyer
et
al.
(
1980)

17­
20
Marine
(
1997)

12
Wedemeyer
et
al.
(
1980)

Coho
15
Zaugg
and
McLain
(
1976)

12
Wedemeyer
et
al.
(
1980)

15
Adams
et
al.
(
1975)

Steelhead
>
13
Hoar
(
1988)

>
12.7
Adams
et
al.
(
1975)

(
summer
steelhead)
>
13.6
Zaugg
et
al.
(
1972,
as
cited
by
Zaugg
and
Wagner
1973)

12
Zaugg
(
1981)

Sockeye
12­
14
Brett
et
al.
(
1958)
8
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
To
provide
a
thermal
regime
protective
of
smoltification,
temperature
should
follow
a
natural
seasonal
pattern
(
Wedemeyer
et
al.
1980).
Varying
temperatures
are
common
in
the
natural
environment,
and
fluctuating
temperatures
are
more
stimulating
to
steelhead
smoltification
than
constant
temperatures
(
Wagner
1974
as
cited
by
Hoar
1988,
Zaugg
and
Wagner
1973).
An
extreme
example
of
the
interference
of
elevated
and
constant
temperatures
on
smoltification
can
be
found
in
the
mainstem
Columbia
River
reservoirs,
where
environmental
conditions
are
of
considerable
concern.
The
large
thermal
inertia
due
to
the
volume
of
stored
water
in
the
reservoirs
alters
the
seasonal,
as
well
as
diel,
thermal
regimes
(
Bennett
et
al.
1997,
Karr
et
al.
1992,
1998).

What
are
the
thermal
requirements
for
swimming
speed?

Beamish
(
1978)
classified
swimming
performance
of
fish
into
three
categories:
sustained,
prolonged,
and
burst
swimming.
Sustained
swimming
performance
is
that
swimming
speed
that
can
be
maintained
for
long
periods
(>
200
min)
without
fatigue.
Prolonged
swimming
speed
defines
a
performance
of
shorter
duration
(
20
s
to
200
min).
Burst
swimming
speed
is
the
speed
a
fish
can
swim
for
a
few
seconds.
Swimming
speed
for
fish
of
a
certain
species
and
size
can
have
maximum
swimming
speeds
defined
by
the
number
of
body
lengths
traveled
per
second
(
Bjornn
and
Reiser
1991)
or
in
absolute
terms
of
distance/
time.

According
to
Bell
(
1986),
sustained
speed
is
used
for
passage
through
difficult
areas,
prolonged
or
cruising
speed
during
migration,
and
dart
or
burst
speed
for
escape,
feeding,
and
rapid
movement
through
swift
water.
During
adult
migration,
if
water
temperature
is
high
or
oxygen
concentrations
are
low,
swimming
speed
can
be
impaired
and
the
fish
may
refuse
to
migrate,
migrate
back
downstream,
or
seek
shelter
in
tributaries
or
other
available
cold­
water
refuges
(
Fish
1948,
Schreck
et
al.
1994).
Under
these
conditions
the
migration
may
be
delayed
or
restricted.
Smolts,
on
the
other
hand,
benefit
from
availability
of
rapid
current
flow
because
their
downstream
progress
depends
on
water
velocity
rather
than
their
swimming
speed.
However,
swimming
speeds
of
smolts
must
not
be
impaired
because
swimming
is
vital
to
maintaining
position
in
the
current
to
control
rate
of
descent
and
avoid
obstacles.

Small
fish
generally
have
lower
swimming
speeds
(
ft/
s)
than
large
fish
at
any
given
temperature.
Large
predators
can
easily
overtake
small
fish,
so
that
ability
to
avoid
predators
with
burst
swimming
is
essential.
Burst
swimming
used
during
avoidance
behavior
requires
recovery
time,
and
excessive
stress
can
lead
to
death.
Burst
swimming
can
be
impaired
under
high
temperature
or
low
oxygen
conditions.
Predaceous
species
more
adapted
to
warm
water
such
as
northern
pikeminnow
(
native),
walleye
(
exotic),
and
smallmouth
bass
(
exotic),
for
example,
find
their
optimum
swimming
speeds
at
temperatures
greater
than
those
of
salmon
and
steelhead.

Water
temperature
and
oxygen
are
significant
cont
rols
on
swimming
speed.
Swimming
performance
also
depends
on
prior
acclimation
temperature
in
relation
to
exposure
temperature.
Disease
has
been
shown
to
adversely
affect
the
swimming
performance
of
mature
sockeye
salmon
caught
in
Port
Alberni
Inlet
and
transferred
to
Simon
Fraser
University
for
swimming
tests
at
66.2­
69.8
°
F
(
19­
21
°
C)
(
as
cited
in
Macdonald
et
al.
in
press).
Critical
swimming
performance
9
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
was
reduced
to
65%
of
normal
by
diseases.
Stress
can
also
adversely
affect
swimming
performance.
High
plasma
lactate
levels
are
known
to
negatively
affect
swimming
performance
(
Farrell
et
al.
1998
as
cited
in
Macdonald
et
al.
in
press).
Telemetry
studies
at
Hell's
Gate
suggest
that
fish
that
failed
to
negotiate
Hell's
Gate
exhibited
one
or
more
periods
>
10
min
in
which
they
swam
at
speeds
greater
than
their
estimated
critical
swimming
speed.
Stress
is
believed
to
induce
such
frantic
behavior
and
cause
the
fish
to
be
washed
downstream.

Field
studies
with
Fraser
River
sockeye
(
as
cited
in
Macdonald
et
al.
in
press)
reportedly
support
the
work
of
Brett
(
1971,
1995)
(
optimum
swimming
performance
at
59­
64.4
°
F
[
15­
18
°
C])
and
found
the
temperature
optimum
to
be
62.6
°
F
(
17
°
C)
for
swimming
endurance,
with
almost
a
20%
reduction
in
swimming
speed
at
69.8
°
F
(
21
°
C).

In
1997,
researchers
reportedly
found
that
because
of
high
water
velocity
some
sockeye
salmon
depleted
their
lipid
stores
more
quickly
than
in
previous
years.
Consequently,
muscle
protein
and
glycogen
reserves
were
utilized
earlier
in
the
migration
than
was
expected
under
normal
conditions;
many
fish
failed
to
reach
the
spawning
grounds
(
Donaldson
et
al.
2000,
Higgs
et
al.
2000;
as
cited
in
Macdonald
et
al.
in
press).
Given
that
water
temperature
in
1998
exceeded
the
average
by
3.6­
7.2
°
F
(
2­
4
°
C),
the
authors
expected
that
metabolic
stores
would
have
been
reduced
at
least
25%
faster
during
river
migrat
ion.

What
are
the
thermal
requirements
for
migration
to
spawning?

Salmonids
often
migrate
great
distances
(
intrabasin
or
upstream/
downstream
anadromous
migrations)
in
river
systems
during
the
warm
season.
The
success
of
these
migrations
can
depend
substantially
on
water
temperatures.
Most
stocks
of
anadromous
salmonids
have
evolved
with
the
temperature
regime
of
the
streams
they
use
for
spawning
and
migration,
and
alteration
of
the
normal
temperature
pattern
can
result
in
reduced
fitness.
Migration
blockages
occur
consistently
among
species
in
the
temperature
range
66.2­
73.4
°
F
(
19­
23
°
C)
(
Table
3).

Elevated
temperatures
in
mainstem
rivers
that
provide
migration
corridors
(
especially
those
dominated
by
reservoirs)
are
harmful
for
survival
and
reproduction
of
bull
trout,
chinook,
steelhead,
and
sockeye
(
especially,
because
of
their
adult
migration
timing).
These
effects
occur
via
several
mechanisms:
(
1)
direct
lethality
to
adults
and
smolts
under
high
temperature
conditions,
(
2)
delay
in
migration
and
spawning,
(
3)
depletion
of
energy
stores
through
heightened
respiration,
(
4)
deformation
of
eggs
and
decreased
viability
of
gametes,
and
(
5)
increased
incidence
of
debilitating
diseases.
See
the
Behavior
issue
paper
for
a
discussion
of
the
effects
of
temperature
on
the
migratory
behavior
of
salmonids.

Macdonald
et
al.
(
in
press)
studied
the
high
mortality
rates
in
sockeye
and
chinook
salmon
that
occurred
in
the
Fraser
River
Watershed
of
British
Columbia,
Canada.
They
found
temperature
to
be
the
likely
cause
of
bot
h
en
route
and
prespawning
losses.
On
the
basis
of
their
review
of
the
historical
database,
the
authors
suspected
that
losses
in
spawning
runs
occur
when
mean
daily
river
temperatures
exceed
62.6­
64.4
°
F
(
17­
18
°
C)
for
prolonged
periods.
Migration
blockages,
susceptibility
to
disease,
impaired
maturation
process,
increases
to
stress
parameters,
reduced
efficiency
of
energy
use,
and
reduced
swimming
performance
were
all
cited
as
potentially
serious
hazards
as
daily
mean
temperatures
exceed
62.6
°
F
(
17
°
C).
In
examining
fertilization
10
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
success,
the
authors
found
significant
impairment
(
only
10%
success)
in
stocks
that
Table
3.
Studi
es
that
identify
thermal
blockages
to
adult
salmon
migration
Species
River
Temperature
cited
as
blocking
migration
Reference
chinook,
sockeye,
steelhead
Columbia
71­
75
°
F
(
21.7­
23.9
°
C)
Fish
and
Hanavan
(
1948)

spring
chinook
Clearwater,
Idaho
69.8
°
F
(
21
°
C)
Stabler
(
1981)

spring
chinook
Tucan
non
69.9
°
F
(
21.1
°
C)
Bumgarner
et
al.
(
1997)

spring
chinook
Willamette
69.8­
71.6
°
F
(
21­
22
°
C)
(
at
oxygen
>
3.5
mg/
L)
Alabaster
(
1988)

summer
chinook
Snake
69.8
°
F
(
21
°
C)
Stuehrenberg
et
al.
(
1978)
(
as
cited
by
Dauble
and
Mueller
1993).

fall
ch
inook
Sacramento
66.2­
69.8
°
F
(
19­
21
°
C)
(
oxygen
~
5
mg/
L)
Hallock
et
al.
(
1970)

steelhead
Snake
69.8
°
F
(
21
°
C)
Stricklan
d
(
1967,
as
cited
by
Stabler
1981)

sockeye
Okanogan
69.8
°
F
(
21
°
C)
Major
and
Mighell
(
1967)

sockeye
Snake
71.9
°
F
(
22.2
°
C)
Quinn
et
al.
(
1997)

sockeye
Okanogan
73
°
F
(
22.8
°
C)
Hatch
et
al.
(
1993)

sockeye
Fraser
64.4­
71.6
°
F
(
18­
22
°
C)
Macdonanld
et
al.
in
press
migrated
through
t
he
Fraser
during
1998
(
a
record
warm
year)
compared
with
success
during
cooler
years.
Dr
.
Craig
Clarke
(
as
cited
in
Macdonald
et
al.
in
press)
found
that
a
2­
wk
exposure
to
66.2
°
F
(
19
°
C)
compared
with
59
°
F
(
15
°
C)
in
the
labo
ratory
was
sufficient
to
significantly
depress
the
hormones
controlling
sexual
maturation
in
sockeye
salmon.
This
was
viewed
as
consistent
with
the
finding
of
Manning
and
Kime
(
1985,
as
cited
in
Macdonald
et
al.
in
press)
that
steroid
biosynthesis
was
suppressed
in
rainbow
trout
testes
at
62.6
°
F
(
17
°
C).

Migration
has
been
observed
to
occur
under
a
wide
range
of
conditions
for
each
salmon
species
(
see
Bjornn
and
Reiser
1991).
This
reflects
a
combination
of
characteristics
about
the
fish:
the
seasonality
of
their
migration
period,
temperatures
that
were
available
to
them
during
their
normal
migration
period,
shifts
in
migration
timing
that
may
have
occurred
over
time
(
e.
g.,
effects
o
f
deliberate
attempts
by
hatchery
managers
to
creat
e
a
run
t
hat
does
not
overlap
with
a
wild
run,
t
he
response
by
the
stock
itself
to
shifts
in
river
temperature
regimes
during
the
incubation,
smolt
migration,
and/
or
adult
migration
periods),
and
in
some
species
that
migrate
during
warm
seasons
their
tolerance
to
elevated
temperatures.
Bioenergetic
stresses
(
ability
to
maintain
long­
term
energy
reserves),
instantaneous
power
demands
(
ability
to
exhibit
burst
swimming,
jump
falls,
escape
predators,
recover
from
stress
[
exertion,
disease]),
and
ability
to
11
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
resist
disease
may
all
be
of
concern
in
the
higher
temperature
range
for
migration.
Just
as
distribution
of
juveniles
relates
to
temperature
in
a
stream
system
(
i.
e.,
from
optimum
to
suboptimum
to
the
distributional
limits),
migration
temperatures
can
be
assumed
to
have
an
optimum
that
is
less
than
the
migration
limit
and
migrat
ion
can
be
impaired
as
the
limit
is
approached.

Fall
and
spring
chinook
are
examples
of
different
life
history
types
of
a
single
species
having
differing
migration
and
spawning
timings.
Given
the
similarity
in
ultimate
upper
incipient
lethal
temperatures
of
these
two
races
(
NAS
1972)
and
t
he
minor
differences
in
ultimate
upper
incipient
lethal
temperature
(
UUILT)
among
stocks
of
numerous
species,
it
is
reasonable
to
assume
that
fall
and
spring
chinook
have
similar
UUILT
values
for
juvenile
and
adult
stages,
respectively.
Because
adult
spring
chinook
migrate
earlier
in
the
year
than
fall
chinook
they
encounter
cooler
water
temperatures
in
mainstem
rivers.
However,
spring
chinook
also
must
hold
in
tributaries
until
the
autumn
spawning
season,
so
avoidance
of
high
holding
temperatures
is
their
thermal
challenge.
For
fall
chinook,
the
thermal
challenge
is
avoidance
of
higher
thermal
stress
both
during
adult
migration
and
during
a
more
brief
holding
period.
Temperature
ranges
for
spring,
summer,
and
fall
chinook
migration
have
been
summarized
(
see
Bjornn
and
Reiser
1991),
and
show
that
spring
chinook
tend
to
migrate
under
a
range
of
temperatures
having
a
lower
maximum.
Given
the
similarity
in
lethal
temperatures
within
this
species,
the
temperatures
linked
to
successful
migration
for
fall
chinook
might
also
adequately
represent
the
capability
of
spring
chinook,
which
are
not
normally
tested
because
temperatures
do
not
tend
t
o
be
as
high
during
their
migration
period.
However,
threshold
temperatures
linked
to
a
complete
inability
to
migrate
are
very
similar
between
spring
and
fall
chinook,
as
well
as
among
many
anadromous
species
that
have
been
examined.

What
are
the
thermal
requirements
for
adult
holding
and
spawning?

Full
protection
of
salmonids
during
reproduction
involves
managing
instream
temperature
during
several
phases
of
the
reproductive
cycle
(
prespawning,
spawning,
and
postspawning).
Successful
reproduction
can
involve
success
(
survival
of
adults
and
their
gametes)
during
migration,
holding
prior
to
spawning,
mate
selection,
redd
digging,
egg
deposition,
and
nest
guarding.
For
fall­
spawning
fish
(
e.
g.,
bull
trout,
chinook,
co
ho,
chum),
temperatures
typically
reach
t
heir
annual
highs
during
migration
and/
o
r
holding.
Stocks
that
take
advantage
of
the
predictability
of
the
most
generally
favorable
seasons
time
their
migration
and
spawning
to
complete
life­
cycle
phases.
Long­
term
alterations
in
temperature
regimes
can
disrupt
this
timing.
Disruptions
in
timing
include
a
reduction
in
time
available
to
complete
a
subsequent
life­
cycle
process
or
a
change
in
timing
of
this
process.

Temperature
can
inhibit
upstream
migration
of
adult
fish.
This
can
result
in
seeking
coldwater
refuges
such
as
deep
pools
in
the
mainstem,
cold
tributary
mouths,
or
downstream
mainstem
areas.
Inhibitory
temperatures
thus
can
cause
migration
delays
that
alter
timing
of
key
processes
such
as
spawning
or
can
lead
to
stress,
disease,
bioenergetic
depletion,
or
death.
If
migration
occurs
at
high
temperatures
just
prior
to
spawning
(
such
as
in
fall
chinook
or
coho),
gametes
held
internally
in
adults
can
be
severely
affected,
resulting
in
a
loss
of
viability
that
appears
as
poor
fertilization
or
embryo
survival.
High
temperatures
during
the
holding
or
prespawning
stages
can
also
occur
in
many
locations,
even
if
adults
have
managed
to
escape
high
12
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
mainstem
migration
temperatures.
Then,
if
water
temperatures
have
not
begun
to
decline
below
critical
thresholds
before
spawning
begins,
fertilization
and
early
incubation
survival
will
be
affected.
Early
incubat
ion
is
very
sensitive
to
elevated
temperatures.
In
addition,
salmonid
diseases
can
affect
the
egg
stage
as
readily
as
other
life
stages.

The
above
section
on
migration
detailed
the
inhibition
of
adult
migration
that
occurs
with
elevated
temperatures
in
migratory
corridors.
Spring
chinook,
summer
chinook,
and
fall
chinook
all
migrate
during
different
seasons,
but
high
water
temperatures
can
be
assumed
to
have
similar
effects
on
migration
for
all
races.
In
addition,
other
species
respond
to
the
same
thresholds.
Furthermore,
it
is
of
great
concern
that
UILT
values
for
chinook
and
coho
are
appro
ximately
the
same
as
the
temperatures
that
inhibit
migration.
This
implies
that
salmon
will
cease
migrating
at
temperatures
just
below
those
required
to
kill
a
portion
of
the
population.

What
are
lethal
temperature
effects?

National
Academy
of
Sciences
(
NAS)
(
1972)
recommendations
for
water
temperature
exposure
for
protection
of
aquatic
life
specify
maximum
acceptable
temperatures
for
prolonged
exposures
($
1
wk),
winter
maximum
temperatures,
short­
term
exposure
to
extreme
temperature,
and
suitable
reproduction
and
development
temperatures.
Lethal
effects
are
thermal
effects
that
cause
direct
mortality
within
an
exposure
period
of
less
than
1
wk.
Prolonged
exposure
temperatures
and
temperatures
that
interfere
with
normal
reproduction
and
development
can
result
in
mortality
or
reduction
in
population
fitness
or
production,
but
the
effects
may
be
delayed
or
indirect,
or
result
from
impairment
of
function
or
reduction
in
suitable
habitat
or
food
quantity
and
quality
available.

Survival
rates
based
on
amount
o
f
time
exposed
and
temperature
of
exposure
are
extremely
well
described
in
the
scientific
literature.
These
time­
temperature
relationships
have
been
described
using
equations
of
the
form
log
(
time)
=
a
+
b
(
temp.),
where
time
is
expressed
in
minutes,
temperature
is
in
degrees
Celsius,
and
a
and
b
are
coefficients
for
intercept
and
slope
of
the
regression,
respectively,
described
for
individual
acclimation
temperatures
(
NAS
1972).
The
regression
describes
the
combinations
of
time
and
temperature
that
result
in
mortality
(
typically
recorded
as
the
point
of
estimated
50%
mortality)
at
various
acclimation
temperatures.
The
upper
incipient
lethal
temperature
(
UILT)
is
an
exposure
temperature,
given
a
previous
acclimation
to
a
constant
acclimation
temperature,
that
50%
of
the
fish
can
tolerate
for
7
d
(
Elliott
1981).
Alternatively,
UILT
at
a
particular
acclimation
temperature
has
been
determined
as
an
exposure
temperature
producing
50%
survival
within
1,000
min
(
Brett
1952,
Elliott
1981)
or
24
h
(
Wedemeyer
and
McLeay
1981,
Armour
1990).
Within
this
variation
in
exposure
times,
we
expect
a
slightly
lower
UILT
at
a
7­
d
than
a
24­
h
exposure.
The
UILT
becomes
greater
with
increasing
acclimation
temperature
until
a
point
is
reached
at
which
further
increase
in
acclimation
temperature
results
in
no
increase
in
temperature
tolerated
with
the
same
survival
level.
This
is
the
ultimate
upper
incipient
lethal
temperature.

In
addition
to
acclimating
fish
to
a
constant
temperature
prior
to
exposure
to
test
temperatures,
fish
may
be
acclimated
to
a
fluctuating
temperature
regime.
It
is
possible
to
determine
for
a
cyclic
acclimation
temperature
a
corresponding
constant
temperature,
that
is,
an
equivalent
constant
temperature.
This
is
accomplished
by
experimentally
determining
the
const
ant
13
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
acclimation
temperature
within
the
range
of
the
cyclic
regime
that
produces
the
same
response
to
an
exposure
temperature
as
the
cyclic
regime.

Because
UILT
varies
with
increasing
acclimation
temperature
until
the
UUILT
is
reached,
the
UUILT
is
a
good
stable
index
for
comparing
thermal
response
among
species.
For
salmonids,
a
survey
of
the
literature
indicat
es
that
acclimation
temperatures
above
approximately
68
°
F
(
20
°
C)
produce
similar
UILT
values,
although
very
small
increases
in
UILT
can
occur
at
up
to
a
75.2
°
F
(
24
°
C)
acclimation
temperature.
Consequently,
it
can
be
safely
assumed
that
any
UILT
study
in
which
acclimation
temperature
was
$
68
°
F
(
20
°
C)
will
produce
a
UILT
nearly
identical
to
the
UUILT.
UILT
values
compiled
from
the
literature
(
taken
from
McCullough
1999)
for
various
acclimation
temperatures
are
presented
in
Table
4.
Given
the
considerations
above,
these
values
can
be
interpreted
as
estimates
of
UUILT.

What
conclusions
can
you
draw
for
anadromous
salmonids
and
coastal
cutthroat
and
rainbow
trout?

1.
Five
species
of
Pacific
salmon
 
chum,
Oncorhynchus
keta;
coho,
O.
kisutch;
sockeye,
O.
nerka;
chinook,
O.
tshawytscha;
and
pink,
O.
gorbuscha
 
and
steelhead,
O.
mykiss,
and
coastal
cutthroat
trout,
O.
clarki,
are
stenothermic
and
have
similar
physiological
requirements
for
cold
water.
Given
their
similarity
in
physiological
requirements,
a
common
temperature
criterion
could
be
established
to
protect
these
seven
species
as
a
single
group.
In
those
waterbodies
where
multiple
species
and
life
stages
are
present
,
temperature
crit
eria
would
need
to
be
oriented
to
the
most
sensitive
species
and
life
history
stage.

2.
Measures
of
maximum
growth
and
swimming
speed
are
useful
in
defining
the
optimal
temperature
range.
However,
these
tests
are
typically
conducted
under
controlled
laboratory
conditions
and
may
not
accurately
reflect
the
influence
of
temperature
under
the
more
complex
ecological
context
of
natural
stream
systems.
Laboratory
results
may
need
to
be
adjusted
downward
to
account
for
the
influences
of
reduced
food
availability,
competition,
predation,
and
other
environmental
variables.
Also,
laboratory
results
may
not
reveal
sublethal
effects
associated
with
an
increased
risk
of
warm­
water
disease
and
physiological
stresses
of
smoltification
under
elevated
water
temperatures.

a.
Maximum
growth
and
swimming
speed
generally
occur
within
the
range
of
55.4­
68
°
F
(
13­
20
°
C)
for
native
salmon
and
trout
under
laboratory
conditions
in
which
fish
are
fed
to
satiation.
Maximum
swimming
speeds
appear
to
be
at
temperatures
greater
than
those
providing
maximum
growth
rates.
The
ecological
need
for
temperatures
allowing
maximum
growth
is
greater
than
for
maximum
swimming
speed.
That
is,
of
the
two
biological
performances
controlled
by
temperature,
growth
rates
have
a
greater
need
to
be
optimized
on
a
basinwide
scale
(
see
issue
papers
on
Fish
Distribution
and
Spatio­
Temporal
Effects
as
well
as
the
final
synthesis
paper
for
a
complete
description
of
this
concept).
In
addition,
optimum
growth
temperatures
provide
nearly
optimum
swimming
speeds.

b.
Streams
with
naturally
low
productivity
or
in
which
food
availability
is
lower
than
under
natural
conditions
(
e.
g.,
caused
by
stream
channel
sedimentation
and
high
14
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
substrate
embeddedness)
can
be
expected
to
produce
optimal
growth
at
temperatures
that
are
lower
by
at
least
3.6­
7.2
°
F
(
2­
4
°
C)
and,
under
certain
conditions,
as
much
as
Table
4.
Upper
incipient
lethal
temperature
of
various
juvenile
salmonids
Species
Common
Name
Origin
(
river/
lake)
Author(
s)
Accl.
Temp.
(/
C)
UILT
(
°
C)

Oncorhynchus
tshawytscha
chinook
salmon
Dungeness
Hatchery,
WA
Brett
(
1952)
20
24
25.1
25.1
Sacramen
to
River
Orsi
(
1971,
as
cited
by
CDWR
1988)
21.1
24.9
Oncorhynchus
kisutch
coho
salmon
Nil
e
Cr
.
Hatch
ery,
British
Columbia
Brett
(
1952)
20
23
25.0
25.0
Oncorhynchus
nerka
sockeye
salmon
Issaquah
Hatch
ery,
WA
McConnell
and
Blahm
(
1970)
(
as
cited
by
Coutant
1972)
Brett
(
1952)
20
20
23
23.5
24.8
24.3
Oncorhynchus
keta
chum
salmon
Nil
e
Cr
.
Hatch
ery,
British
Columbia
Brett
(
1952)
20
23
23.7
23.8
Oncorhynchus
gorbuscha
pink
Dungeness
Hatchery,
WA
Brett
(
1952)
20
24
23.9
23.9
Oncorhynchus
mykiss
rainbow
trout
Lake
Superior
Hokanson
et
al.
(
1977)
16
25.6
France
Charlon
et
al.
(
1970)
24
26.4
Lakes
Erie,
Onta
rio,
Huron,
Superior
Bidgood
and
Berst
(
1969)
15
25­
26
Cherry
et
al.
(
1977)
24
25
Stauffer
et
al.
(
1984)
24?
26
Ontario
Threader
and
Houston
(
1983)
20
25.9
Alabaster
(
1964)
(
as
cited
by
Threader
and
Houston
1983)
20
26.7
Summerland
Hatchery,
British
Columbia
Black
(
1953)
11
24
Firehole
River,
MT
Ennis
Hatchery
Winthrop
Hatchery
Kaya
(
1978)
24.5
24.5
24.5
26.2
26.2
26.2
15
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
Table
4.
Upper
incipient
lethal
temperature
of
various
juvenile
salmonids
(
continued)

Species
Common
Name
Origin
(
river/
lake)
Author(
s)
Accl.
Temp.
(/
C)
UILT
(
°
C)

redband
trout
Parsnip
Reservoir,
Oregon
Sonski
(
1983a)
20
23
27.4
26.8
Parsnip
Reservoir,
Oregon
Sonski
(
1984)
20
23
26.2
26.2
Firehole
River,
Wyoming
20
23
27.2
26.3
Wytheville
rainbow
20
23
26.8
27.0
Salmo
salar
Atlantic
salmon
England
Bishai
(
1960)
20
23.5
Salmo
trutta
brown
trout
England
Bishai
(
1960)
20
23.5
Frost
and
Brown
(
1967)
23
25.3
Cherry
et
al.
(
1977)
?
23
England
Alabaster
and
Downing
(
1966)
(
as
cited
by
Grande
and
Ander
son
1991)
20
26.3
Salvelinus
fontinalis
brook
trout
Ontario
Fry,
Hart,
and
Walker
(
1946)
20
24
25.3
25.5
Cherry
et
al.
(
1977)
?
24
Salvelinus
namaycush
lake
trout
Ontario
Fry
and
Gibson
(
1953)
20
24.0­
24.5
Thymallus
arcticus
Arctic
grayling
Montana
Lohr
et
al.
(
1996)
20
25
Alaska
LaPerriere
and
Carlson
(
1973)
(
as
cited
by
Lohr
et
al.
1996)
?
24.5
14.4
°
F
(
8
°
C)
from
temperatures
producing
optimal
growth
under
satiation
feeding.
In
the
natural
environment,
food
is
often
limited
to
less
than
satiation
levels.

c.
Disease
occurrence
and
severity
are
primarily
determined
by
the
specific
strain
of
the
pathogen,
the
temperature
of
the
wat
er,
and
the
relative
health
of
the
exposed
fish.
The
following
general
pat
terns
can
be
ident
ified
from
laboratory
and
field
research:
constant
16
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
temperatures
below
53.6­
55.4
°
F
(
12­
13
°
C)
often
reduce
or
eliminate
both
infection
and
mortality;
temperatures
above
59­
60.8
°
F
(
15­
16
°
C)
are
often
associated
with
high
rates
of
infection
and
notable
mortality;
temperatures
above
64.4­
68
°
F
(
18­
20
°
C)
are
often
associated
with
serious
rates
of
infection
and
catastrophic
outbreaks
of
many
fish
diseases.

d.
At
t
he
time
of
smoltification,
anadromous
salmonids
experience
reduced
ATPase
levels
at
constant
or
acclimation
temperatures
greater
than
51.8­
55.4
°
F
(
11­
13
°
C).
Reduced
ATPase
levels
may
result
in
delayed
or
ineffective
transition
to
t
he
marine
environment
and
may
result
in
smolts
attempting
to
ret
urn
to
freshwaters
to
wait
unt
il
the
next
spring.
Temperatures
above
64.4
°
F
(
18
°
C)
may
inhibit
feeding
in
smolts,
and
temperatures
of
57.2­
59
°
F
(
14­
15
°
C)
may
cause
cessation
of
the
seaward
migration.

3.
Stream
temperatures
vary
through
the
spawning
and
egg
incubation
period,
particularly
for
species
that
spawn
in
late
summer
and
fall.
There
are
several
factors
to
consider
in
setting
a
criterion
for
these
life
history
stages:
temperatures
that
affect
survival
of
gametes
in
adults
prior
to
spawning,
temperatures
that
affect
the
initiation
of
spawning
behavior,
temperatures
that
maximize
the
survival
of
eggs
upon
deposition
in
gravels
and
early
embryo
stages,
and
temperatures
that
allow
for
the
correct
timing
and
size
of
fry
at
hatch
and
emergence.
In
summary,
it
appears
that
a
range
of
temperatures
from
42
to
55
°
F
(
5.6­
12.8
°
C)
allows
for
successful
spawning
and
incubation
for
different
species
of
salmon.

a.
For
fall­
spawning
fish,
spawning
may
be
initiated
in
the
field
at
temperatures
of
57.2­
60.8
°
F
(
14­
16
°
C).
Experiments
done
at
constant
incubation
temperatures,
however,
show
that
survival
of
eggs
under
these
conditions
is
low.
Consequently,
spawning
temperatures
>
57.2
°
F
(
14
°
C)
are
considered
to
provide
marginal
to
poor
egg
survival
for
these
early­
spawning
fish.

b.
For
fall­
spawning
fish,
spawning
that
is
initiated
as
daily
maximum
temperatures
fall
below
53.6­
57.2
°
F
(
12­
14
°
C)
results
in
greater
incubation
success,
with
55
°
F
(
12.8
°
C)
being
adequate
for
most
salmon
species.

c.
In
laboratory
studies,
constant
temperatures
of
42.8­
50
°
F
(
6­
10
°
C)
or
lower
during
incubation
consistently
result
in
maximum
survival
and
size
at
emergence
for
Pacific
salmon,
steelhead,
and
coastal
cutthroat
trout.

d.
Constant
incubation
temperatures
as
low
as
39.2
°
F
(
4
°
C)
and
as
high
as
53.6
°
F
(
12
°
C)
can
result
in
good
to
very
good
survival
to
hatching
and
emergence,
with
approximately
46.4
°
F
(
8
°
C)
being
optimal
for
most
salmon
species.

4.
Laboratory
and
field
studies
show
that
when
adult
fish
are
exposed
to
constant
or
average
temperatures
above
55.4­
60
°
F
(
13­
15.6
°
C)
during
the
final
part
of
the
upstream
migration
or
during
holding
prior
to
spawning,
there
is
a
detrimental
effect
on
the
size,
number,
and/
or
fertility
of
eggs
held
in
vivo.

5.
Many
studies
have
been
done
on
the
acute
lethality
of
warm
water
temperatures
on
17
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
salmonids.
Laboratory
tests
of
acute
lethality
measure
the
temperature
at
which
50%
of
the
fish
die
after
1
to
7
d
of
exposure
to
a
constant
temperature
(
upper
incipient
lethal
temperature,
or
UILT).

a.
The
range
in
UILT
values
found
in
multiple
tests
of
various
species
of
juvenile
salmonids
is
73.4­
75.2
°
F
(
23­
24
°
C)
when
acclimation
temperatures
are
between
50
and
59
°
F
(
10
and
15
°
C).
Although
UUILT
(
ultimate
upper
incipient
lethal
temperature)
values
reported
in
the
literat
ure
and
in
this
paper
are
up
to
78.8
°
F
(
26
°
C),
fish
in
the
field
will
not
necessarily
be
acclimated
to
warm
temperatures
as
they
are
in
laboratory
tests
of
UUILT.
Therefore,
UILT
values
in
the
field
may
be
1.8­
3.6
°
F
(
1­
2
°
C)
lower
t
han
the
UUILT
values
derived
in
the
laboratory.

b.
The
range
in
UILT
values
for
adult
salmonids
is
69.8­
71.6
°
F
(
21­
22
°
C)
when
acclimation
temperatures
are
approximately
66.2
°
F
(
19
°
C).
Adults
appear
to
have
lethal
tolerances
3.6­
5.4
°
F
(
2­
3
°
C)
lower
than
the
juvenile
fish
typically
used
in
lethality
testing.

c.
When
fish
are
acclimated
below
53.6
°
F
(
12
°
C),
substantial
lethality
(
LT50)
can
be
expected
to
occur
almost
instantly
(
1­
60
s)
at
temperatures
above
86­
93.2
°
F
(
30­
34
°
C).

d.
Migratory
fish,
particularly
anadromous
fish,
may
not
be
fully
acclimated
to
warm
mainstem
temperatures.

e.
In
a
fluctuating
environment,
multiple­
day
exposure
to
lethal
temperatures
may
create
cumulative
effects.

6.
For
all
salmonids,
figures
can
be
compiled
from
the
literature
to
depict
temperature
requirements
by
species
and
life
stage.
Such
a
diagram
was
developed
by
McCullough
(
1999)
for
spring
chinook.
The
value
of
such
diagrams
is
to
highlight
the
ranges
for
normal
function
and
high
survival
(
e.
g.,
egg
incubation,
adult
migration),
optimum
growth
ranges
(
e.
g.,
juvenile
stage),
and
thresholds
for
effects
that
become
increasingly
significant
both
above
and
below
incipient
lethal
levels
(
e.
g.,
disease,
migration
blockages,
cold
effects
on
egg
incubation).
For
any
life
stage,
there
are
multiple
potential
effects
on
survival,
fitness,
and
growth.
Recommendations
for
temperature
criteria
for
a
waterbody
must
account
for
the
most
sensitive
species,
most
sensitive
life
stages
of
a
species
for
any
season,
and
the
multiple
effects
on
each
life
stage.

What
conclusions
can
you
draw
for
bull
trout
and
Dolly
Varden?

1.
Bull
trout
(
S.
confluentus)
are
not
actually
trout,
but
are
char.
Bull
trout
and
Dolly
Varden
(
S.
malma)
are
the
only
native
char
found
in
Idaho,
Washington,
and
Oregon.
Members
of
the
genus
char
live
in
the
coldest,
cleanest,
and
often
most
secluded
waters.

2.
All
char
are
fall
spawners
and
cold
water
temperatures
seem
to
be
the
proximate
cue
that
initiates
spawning
behavior
and
defines
distribution.
Char
are
cold­
water
fish
that
are
18
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
especially
sensitive
to
thermal
change
and
find
optimal
rearing
conditions
in
a
wide
variety
of
stream
sizes
that
can
provide
the
coldest
water
possible
in
the
Pacific
Northwest.
Char
are
Holarctic
in
dist
ribution
and
include
the
most
northerly
distribution
of
any
fish
found
in
freshwater.
Char
may
be
anadromous,
resident,
or
freshwater
migratory.

3.
Litt
le
information
is
available
for
the
physiological
requirements
of
bull
trout
and
Dolly
Varden.
Available
research
for
bull
trout
includes
information
for
incubat
ion,
fry
and
alevin
growth
and
survival,
growth
rates
for
juvenile
fish
under
variable
feeding
regimes,
and
juvenile
lethality.
This
is
substantially
less
than
the
broad
range
of
metrics
available
for
many
other
salmonids;
however,
it
does
include
some
important
physiological
characteristics
for
setting
temperature
criteria.
Evidence
from
laboratory
studies
and
distribution
data
indicates
that
bull
trout
have
optimum
temperature
requirements
substantially
lower
than
the
other
salmonids
examined
in
this
paper,
and
that
water
temperatures
protective
of
bull
trout
will
require
establishment
of
separate
temperature
criteria.

a.
Optimal
incubation
for
bull
trout
eggs
occurs
at
constant
temperatures
in
the
range
of
35.6­
42.8
°
F
(
2­
6
°
C),
with
highest
incubation
success
at
39.2
°
F
(
4
°
C).
Temperatures
in
the
range
of
42.8­
46.4
°
F
(
6­
8
°
C)
can
produce
variable
but
often
substantially
reduced
egg
survival
and
size
at
emergence.

b.
Under
laboratory
conditions,
maximum
growth
temperature
declines
as
ration
declines.
Growth
rates
in
the
studies
conducted
at
satiation
and
66%
satiation
were
highest
at
constant
temperatures
of
60.8
°
F
(
16
°
C),
although
the
growth
rate
was
less
in
the
lower
(
66%)
ration
test
than
at
100%
satiation.
At
the
33%
satiation
ration
the
growth
rate
was
maximized
at
46.4­
53.6
°
F
(
8­
12
°
C).
This
conclusion
is
based
on
a
single
set
of
experiments
on
bull
trout.
Much
more
extensive
studies
of
brown
trout
growth
rates
under
a
series
of
rations
show
similar
declines
in
growth
rate
with
decreased
ration.
From
these
studies
we
would
expect
growth
optima
to
decline
with
each
increment
of
decline
in
ration.

c.
The
UILT
for
juvenile
bull
trout
is
71.6­
73.4
°
F
(
22­
23
°
C)
for
a
7­
d
exposure.

What
conclusions
can
you
draw
for
other
salmonids?

1.
Interior
native
salmonid
species
found
in
Oregon,
Washington,
and
Idaho
include
Westslope
(
O.
clarki
lewisi),
Yellowstone
(
O.
clarki
bouvieri),
Bonneville
(
O.
clarki
utah),
and
Lahontan
cutthroat
trout
(
O.
clarki
henshawi);
redband
trout
(
O.
mykiss
gairdneri);
and
mountain
whitefish
(
Propsipium
williamsoni).

2.
Little
information
is
available
on
the
effects
of
temperature
on
the
physiology
of
these
salmonids.
Although
a
few
laboratory
study
results
are
available,
we
have
referenced
field
distribution
data.

3.
Mountain
whitefish
were
not
reviewed
because
of
limited
information.
It
is
assumed
that
temperature
criteria
established
to
protect
other
salmonid
species
protect
whitefish
where
they
occur.
19
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
SUPPORTING
DISCUSSION
AND
LITERATURE
 
GENERAL
ISSUES
Laboratory
and
Field
Studies
What
are
the
advantages
and
disadvantages
of
laboratory
and
field
data?

Our
understanding
of
thermal
effects
on
salmonids
is
based
on
a
combination
of
laboratory
and
field
evidence.
In
the
adult
life
stage,
much
of
t
he
information
available
comes
from
field
studies;
on
the
other
hand,
for
the
juvenile
life
stages,
most
information
on
thermal
effects
comes
from
laboratory
studies.

Some
argue
that
laboratory
studies
have
limited
use
in
setting
standards
because
of
unrealistic
conditions.
In
truth,
each
type
of
study
is
capable
of
providing
useful
information.
In
determining
the
usefulness
and
applicability
of
laboratory
study
results,
it
is
important
t
o
assess
the
possible
confounding
variables
such
as
whether
wild
fish
or
hatchery
progeny
were
used,
feeding
rations,
competition,
o
r
other
ecological
issues
that
may
or
may
not
be
described
in
the
methods
for
the
laboratory
study.

Reisenbichler
and
Rubin
(
1999)
provide
strong
evidence
that
salmonids'
fitness
for
natural
spawning
and
rearing
can
be
rapidly
and
substantially
reduced
through
artificial
propagation.
Genetic
differences
in
behavior
and
physiology
can
occur
in
the
offspring
of
hatchery
fish.
Hatchery
fish
are
often
raised
in
waters
with
constant
temperature
and
in
warmer
water
more
conducive
to
rapid
growth
at
satiation
feeding.

Laboratory
studies
of
thermal
effects
o
n
salmonids
are
most
often
conducted
under
constant
temperature
conditions,
although
what
is
considered
constant
can
fluctuate
as
much
as
1.8
°
F
(
1
°
C).
It
is
obvious
that
in
natural
stream
systems,
temperatures
fluctuate
hourly.
This
pattern
can
be
represented
as
a
sine
wave,
with
a
maximum
temperature
in
midafternoon
and
a
minimum
temperature
in
early
morning.
This
cycle
is
summarized
statist
ically
according
to
its
minimum,
mean,
or
maximum
temperature.
However,
from
day
to
day
these
values
can
change,
resulting
in
continually
changing
co
nditions
in
the
stream.
If
temperature
cycles
were
identical
(
i.
e.,
their
pattern
and
minimum
and
maximum
remained
steady)
for
several
consecutive
days,
it
would
be
easier
to
biologically
describe
acclimation
conditions.
Under
such
a
repetitive
cycle,
a
scientific
challenge
would
be
t
o
identify
the
"
effective
acclimation
temperature,"
t
hat
is,
the
temperature
in
a
fluctuating
thermal
environment
that
produces
acclimation
equivalent
to
a
constant­
temperature
acclimation.

Fluctuating
temperature
conditions
lead
to
major
issues
that
make
it
difficult
to
predict
thermal
effects.
From
laboratory
tests
using
constant
temperatures
it
is
known
that
survival
is
a
function
of
exposure
temperature
and
exposure
time,
but
the
magnitude
of
the
effect
also
depends
on
prior
acclimation
temperature.
If
water
temperatures
are
variable
during
both
the
acclimation
and
the
exposure
phases
of
a
test,
it
becomes
difficult
to
make
an
accurate
prediction
of
effects
based
on
constant­
temperature
laboratory
studies.
Likewise,
in
the
absence
of
any
laboratory
studies,
it
would
be
difficult
to
create
a
predictive
model
of
survival
under
a
thermal
regime
in
which
acclimation
and
exposure
history
are
both
varying.
20
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
Laboratory
tests
of
survival
under
thermal
stress
have
several
distinct
advantages.
Laboratory
studies
allow
both
acclimation
and
exposure
temperature
to
be
precisely
controlled.
Acclimation
and
exposure
temperatures
can
be
made
either
co
nstant
or
fluctuating,
and
if
fluctuating,
they
can
conform
to
precise,
repeatable
cyclic
patterns.
Under
laboratory
conditions,
we
know
precisely
what
temperatures
fish
are
actually
experiencing.
That
is,
fish
are
not
able
to
seek
thermal
refuges
during
survival
tests
as
they
could
in
the
field.
In
the
laboratory
the
condition
(
diseases,
prior
feeding
history,
gut
contents
prior
to
testing)
of
the
test
organisms
can
be
controlled.

Laboratory
results
can
sometimes
be
an
artifact
of
laboratory
methods,
conditions,
or
apparatus.
For
example,
"
tank
effects"
can
result
from
behavioral
interactions
between
test
organisms.
If
crowding
is
an
issue,
fish
can
be
stressed
from
agonistic
behavior.
If
current
speeds
are
not
similar
to
tho
se
the
fish
would
experience
in
a
field
setting,
many
unexpected
effects
could
occur.
For
example,
various
performances
of
a
population
can
change
with
current
speed
 
behavior,
energy
expenditure
during
swimming,
oxygen
uptake
rate
in
the
gills,
or
recovery
fro
m
stress
(
Milligan
et
al.
2000).
Attention
must
be
given
to
photoperiod
for
certain
performances
to
be
meaningfully
represented
(
Clarke
et
al.
1992).
Disturbance
t
o
test
organisms
during
testing
must
be
controlled
(
e.
g.,
minimizing
startling
the
fish
during
observation).
For
some
kinds
of
tests,
such
as
temperature
preference,
equipment
can
affect
results.
For
example,
it
can
make
a
difference
whet
her
fish
are
allowed
to
seek
their
temperature
preference
within
a
vertical
versus
a
horizontal
thermal
gradient.

Field
t
esting
of
fish
survival
under
high
temperatures
is
not
usually
done.
One
possible
field
method
is
to
catch
fish
from
a
stream
after
having
monitored
the
ambient
temperature
conditions
for
several
days.
This
acclimation
history
would
then
be
used
as
a
basis
for
interpreting
exposure
results.
Fish
could
be
tested
in
an
experiment
al
apparatus
at
st
reamside.
This
method
would
rely
on
art
ificial
equipment
(
t
anks)
t
o
test
their
response,
but
would
involve
uncertainty
in
effective
acclimation
temperature.
An
alternative
method
could
be
to
monitor
fish
densities
weekly
and
water
temperatures
hourly
in
a
stream
reach
netted
off
to
prevent
emigration
or
immigration.
This
would
be
a
"
realistic"
field
test,
but
would
involve
uncertainty
in
effective
acclimation
temperature
and
difficulty
in
integrating
exposure
temperatures.
Also,
reduction
in
fish
density
would
be
attributable
to
natural
mortality
factors
(
developmental
causes,
disease,
predation)
that
would
need
to
be
controlled,
as
well
as
temperature
effects.

If
such
methods
were
feasible,
the
improved
realism
would
be
helpful.
For
example,
it
would
be
useful
to
know
the
influence
of
food
availability
as
mediated
by
thermal
regime
and
other
environmental
conditions
(
light,
nutrients,
organic
inputs,
competition
for
food
and
space),
as
well
as
associated
natural
disease
occurrence,
in
regulating
mortality
under
thermal
stress
from
acclimation
phase
to
exposure
phase
in
the
field.
These
combined
effects
during
acclimation
would
likely
result
in
greater
mortality
under
field
conditions
than
in
laboratory
settings,
in
which
multiple
stresses
are
limited.
Although
these
multiple
effects
constitute
the
realism
that
ecologists
are
interested
in,
the
best
chance
of
adequately
understanding
these
effects
is
to
study
them
in
controlled
laboratory
tests
and
then
compare
predictions
from
laboratory
experience
with
field
data.

If
our
most
precise
understanding
of
thermal
effects
is
from
laboratory
tests,
what
21
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
methods
can
be
used?

Tests
of
survival
under
thermal
stress
have
conventionally
been
done
using
either
the
ILT
(
incipient
lethal
temperature)
or
the
CTM
(
critical
thermal
maximum)
methods.
It
has
generally
been
accepted
that
the
ILT
methodology
presents
the
best
means
of
assessing
acute
effects
because
it
does
not
allow
for
the
variable
levels
of
partial
acclimation
that
occur
in
CTM
tests
having
varying
rates
of
heating.
In
the
ILT
method
the
test
endpoint
is
death;
in
the
CTM
test,
the
endpoint
is
either
loss
of
equilibrium
or
death.

Conventional
use
of
the
ILT
method
is
to
acclimate
test
organisms
at
a
constant
temperature
and
then
immediately
transfer
them
to
a
constant
test
temperature.
This
and
other
methods
are
possible
as
shown
in
the
table
below:

No.
Acclimation
Exposure
Methodology
1
constant
constant
conventional
ILT
(
e.
g.,
Fry
1947,
Brett
1952)

2
constant
cyclic
Hokanson
et
al.
(
1997),
Golden
(
1976)

3
cyclic
constant
Threader
and
Houston
(
1983)

4
cyclic
cyclic
Golden
(
1976)

5
constant
constant,
with
multiple
exposures
6
constant
stepped
increase
CTM
variant
7
constant
continuous
increase
conventional
CTM
(
e.
g.,
Becker
and
Genoway
1979,
Elliott
and
Elliott
1955)

Test
condition
1
is
the
conventional
ILT
methodology
and
allows
the
most
accurate
knowledge
of
effective
temperatures.
Given
data
from
these
tests,
it
is
possible
to
determine
the
percentage
mortality
of
a
salmonid
test
population
at
temperatures
such
as
77,
78.8,
80.6,
82.4,
and
84.2
°
F
(
25,
26,
27,
28,
and
29
°
C),
for
example,
as
well
as
time
to
death.
With
a
mathematical
expression
of
these
results,
it
is
feasible
to
estimate
percentages
of
a
lethal
dose
that
could
be
acquired
during
exposure
to
a
cyclic
temperature
regime.

Test
condition
2
allows
accurate
knowledge
of
acclimation
history.
Subsequent
exposure
to
a
cyclic
regime
could
produce
mortality
in
a
test
population
that
could
be
attributed
to
a
mean
temperature,
maximum
temperature,
or
some
intermediate
temperature.
Mortality
under
a
cycle
could
also
be
predicted
from
knowledge
of
exposure
times
at
each
thermal
increment
under
a
cyclic
regime
and
application
of
mortality
rate
coefficients
for
each
temperature
increment
(
e.
g.,
Coutant
1972)
developed
in
constant­
temperature
experiments.
A
lethal
dose
may
be
estimated
by
this
summation
technique
for
a
single
cycle
(
McCullough
1999,
cumulative
mortification,
see
Fry
et
al.
1946
as
cited
by
Kilgour
and
McCauley
1986).
Alternatively,
mortality
from
a
constanttemperature
exposure
can
be
contrasted
with
that
from
a
cycle
having
the
same
mean
22
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
temperature.
Results
of
this
comparison
vary
with
the
magnitude
o
f
the
cycle
and
whether
the
mean
temperature
is
less
than
or
greater
than
the
optimal
temperature
(
Hokanson
et
al.
1977).

Condition
3
presents
the
best
opportunity
to
estimate
an
equivalent
acclimation
temperature
for
a
cyclic
temperature
regime
in
the
acclimation
phase.
Percentage
survival
is
determined
in
a
constant
temperature
exposure
environment,
given
acclimation
to
a
cyclic
regime.
This
is
then
related
to
that
constant
acclimation
temperature
that
would
have
provided
the
same
survival
(
or
growth
or
swimming
speed,
depending
on
experiment)
as
observed
in
a
cyclic
temperature
exposure.
Experiments
such
as
this
demonstrate
that
equivalent
acclimation
temperatures
in
a
cyclic
thermal
regime
are
equal
to
acclimation
t
o
temperatures
ranging
from
the
mean
to
the
maximum
of
the
cycle
(
Heath
1963,
Golden
1975,
Clarke
1978,
Jensen
1990),
with
much
evidence
indicating
that
a
temperature
intermediate
between
the
mean
and
the
maximum
is
a
good
representation
of
equivalent
acclimation
temperature.

Condition
4
provides
a
temperature
environment
during
acclimation
and
exposure
phases
that
can
mimic
reasonably
occurring
field
situations.
This
provides
the
most
"
natural"
laboratory
conditions,
but
imposes
the
need
to
compare
results
with
combinations
of
constant
acclimation
and/
or
exposure
temperatures.
Mortality
data
obtained
for
cyclic
temperature
exposures
from
this
method
are
best
interpreted
against
data
for
constant
temperature
exposure.
Otherwise,
cumulative
percentage
of
a
lethal
dose
could
be
established
as
in
condition
2
exposure
based
on
constant
temperature
laboratory
data
and
the
derived
survival
coefficient
for
each
test
temperature.

Condition
5
pro
vides
a
constant
acclimation
and
a
constant
exposure
temperature.
This
framework
would
be
effective
in
testing
cumulative
mortality
from
multiple
exposures.
Cumulative
exposures
were
tested
by
DeHart
(
1975),
Golden
(
1975,
1976),
and
Golden
and
Schreck
(
1978)
using
cyclic
temperatures.
They
found
that
mortality
could
be
produced
if
100%
of
a
lethal
dose
were
accumulated
in
periods
of
approximately
2
d.
A
more
effective
test
of
cumulative
mortality
could
be
gained
by
multiple
exposures
to
constant
temperatures.
It
would
be
helpful
to
know
whether
lethal
doses
can
be
accumulated
over
3,
4,
5,
or
more
consecutive
days.

Constant
temperature
acclimatio
n
followed
by
stepped
or
co
ntinuous
increases
in
temperature
provides
survival
results
similar
to
those
of
CTM
tests.
Depending
on
the
rate
of
increase,
a
certain
degree
of
partial
acclimation
can
occur,
leading
to
a
test
endpoint.
If
the
heating
rate
approximates
that
found
in
field
conditions
under
a
thermal
cycle
involving
high
maximum
temperatures,
the
CTM
experiment
based
on
thermal
regime
number
7
(
or
its
co
usin,
number
6)
can
be
helpful
in
inferring
harmful
temperature
fluctuations.
There
are
some
difficulties
in
making
effective
use
of
CTM
data.
As
in
all
laboratory
or
field
experiments,
properly
inferring
effective
acclimation
temperature
is
an
issue.
In
the
CTM
test,
the
heating
rate
determines
the
degree
of
partial
acclimation
that
is
feasible.
Variability
in
response
of
individuals
needs
to
be
considered
in
using
CTM
data
because
mortality
occurs
at
temperatures
below
the
median
level.
Also,
CTM
data
are
based
on
uniform
heating
rates.
In
the
field,
if
high
temperatures
are
sustained
for
variable
time
periods,
exposure
time
and
subsequent
mortality
to
the
most
lethal
conditions
can
vary
substantially.

Potential
for
Variation
Among
Stocks
or
Species
of
Salmonids
23
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
Is
there
enough
significant
gen
etic
variation
among
stocks
or
among
species
to
warrant
geographically
specific
water
temperature
standards?

At
the
time
of
the
1994
Oregon
Triennial
Water
Quality
Review,
which
involved
water
temperature
criteria,
Oregon's
water
temperature
standards
applied
a
standard
of
68
°
F
(
20
°
C)
to
salmon­
bearing
streams
of
northeastern
Oregon
and
57.9
°
F
(
14.4
°
C)
to
Oregon
Coast
Range
streams.
The
technical
committee
concluded
that
there
was
no
evidence
fo
r
significant
genet
ic
variation
in
sensitivity
to
high
water
temperatures
such
that
different
standards
(
especially
ones
differing
by
10.1
°
F
[
5.6
°
C])
could
be
justified
for
different
regions
of
the
State.

Climatic
conditions
vary
substantially
among
regions
of
the
State
and
the
entire
Pacific
Northwest.
Maximum
and
minimum
annual
air
temperatures,
rainfall
and
streamflow
patterns
and
magnitudes,
cloud
cover,
humidity,
and
other
climatic
features
all
influence
downstream
water
temperatures
and
trends.
Climate
also
indirectly
influences
density
and
type
of
riparian
vegetation
that
itself
has
a
role
in
controlling
water
temperature.
Regional
environmental
variations
can
establish
a
template
to
which
a
species
might
make
evolutionary
adaptations.
For
example,
a
species
found
in
a
region
with
streams
having
a
range
of
maximum
summer
water
temperatures
from
46.4
to
78.8
°
F
(
8­
26
°
C)
(
headwaters
to
mouth)
might
become
adapted
over
time
to
warmer
water
temperatures
than
the
same
species
located
in
a
region
having
temperatures
ranging
only
from
46.4
to
68
°
F
(
8­
20
°
C).
These
hypothetical
examples
may
represent
historical
extreme
conditions
in
large
stream
systems
in
coastal
versus
eastern
Oregon
streams.
Such
conditions
could
potentially
have
led
to
evolutionary
adaptations,
resulting
in
development
of
subspecies
differences
in
thermal
tolerance.

Acclimation
is
different
from
adaptation.
Adaptation
is
the
evolutionary
process
leading
to
genetic
changes
that
produce
modifications
in
morphology,
physiology,
and
so
on.
Acclimation
is
a
short­
term
change
in
physiological
readiness
to
confront
daily
shifts
in
environmental
conditions.
The
extent
of
the
ability
to
tolerate
environmental
conditions
(
e.
g.,
water
temperature
extremes)
is
limited
by
evolutionary
adaptat
ions,
and
within
these
const
raints
is
further
modified
by
acclimation.

The
literature
on
genetic
variation
in
thermal
effects
indicates
occasionally
significant
but
very
small
differences
among
stocks
and
increasing
differences
among
subspecies,
species,
and
families
of
fishes.
Many
differences
that
had
been
attributed
in
the
literature
to
stock
differences
are
now
considered
to
be
statistical
problems
in
analysis,
fish
behavioral
responses
under
test
conditions,
or
allowing
insufficient
time
for
fish
to
shift
fro
m
field
conditions
to
test
conditions
(
Mathur
and
Silver
1980,
Konecki
et
al.
1993).
It
is
also
possible
that
tests
intended
to
differentiate
stock
performance
(
e.
g.,
survival,
growth)
could
inadvertently
use
test
individuals
emphasizing
one
or
a
small
number
of
family
groups.
For
example,
when
tested
at
suboptimal
temperatures,
family
groups
of
rainbow
trout
showed
much
greater
variation
in
growth
rates
than
at
optimal
temperatures
(
Wangila
and
Dick
1979).

Are
there
evolutiona
ry
differences
among
salmonid
spec
ies
in
the
Pa
cific
Northwest?
24
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
Within
the
species
O.
tshawytscha
(
chinook
salmon)
there
is
great
variation
in
run
timing,
life
histories,
and
habitat
select
ion.
This
species
has
stream­
type
and
ocean­
type
forms,
featuring
significant
differences
in
length
of
freshwater
residency.
Even
so,
no
subspecies
have
been
designated
for
chinook
or
any
other
salmon
species.
Genetic
variation
does
exist,
however,
within
the
chinook
and
other
salmonids
in
the
Pacific
Northwest,
as
shown
in
classification
tree
diagrams
drawn
by
agencies
such
as
the
National
Marine
Fisheries
Service
(
NMFS).
These
genetic
relationships
are
based
on
enzyme
frequencies.
An
accumulation
of
genetic
differences
between
populations
can
eventually
become
great
enough
that
subspecies
are
recognized.
However,
this
has
apparently
not
happened
within
the
salmon,
despite
the
fact
that
species
such
as
chinook
range
from
Alaska
to
mid­
California
and
from
temperate
coastal
mountain
streams
to
continental
interior
streams.

There
are
many
possible
explanations
why
salmon
have
not
made
a
significant
adaptation
to
high
temperatures
in
streams
of
the
Pacific
Northwest.
Temperature
t
olerance
is
probably
controlled
by
multiple
genes,
and
consequently
would
be
a
core
characteristic
of
the
species
not
easily
modified
through
evolutionary
change
without
a
radical
shift
in
associated
physiological
systems.
Also,
the
majority
of
the
life
cycle
of
salmon
and
steelhead
is
spent
in
the
o
cean
rearing
phase,
where
t
he
smolt,
subadults,
and
adults
seek
waters
with
temperatures
less
than
59
°
F
(
15
°
C)
(
Welch
et
al.
1995).
It
would
be
unlikely
for
optimal
growth
conditions
and
associated
physiological
processes
to
be
radically
different
in
freshwater
systems
than
in
ocean
environments,
especially
when
food
abundance
in
freshwater
is
so
much
more
limited.

What
are
the
major
differences
in
thermal
tolerance
among
and
within
important
families?

One
way
to
look
at
evolutionary
differences
among
salmonids
is
to
compare
the
Salmonidae
with
ot
her
fish
families.
Given
the
data
compilation
for
Salmonidae
in
this
report
(
Table
4)
and
the
compilation
by
Coutant
(
1972)
(
see
McCullough
1999,
Tables
13
and
14),
one
can
infer
a
range
of
UUILT
for
the
families
Salmonidae,
Cyprinidae,
and
Centrarchidae
to
be
73­
78
°
F
(
23­
25.6
°
C),
84­
91
°
F
(
29­
33
°
C)
(
Table
13),
and
91­
98.6
°
F
(
33­
37
°
C)
(
Table
14),
respectively.
The
range
for
Salmonidae
accounts
for
the
response
of
chinook,
coho,
sockeye,
chum,
and
pink
salmon;
steelhead;
Atlantic
salmon;
and
brown,
brook,
and
lake
trout.
There
appears
to
be
very
little
variation
in
UUILT
among
species
in
family
groups,
except
for
a
higher
lethal
limit
for
redband
trout
and
a
lower
one
for
bull
trout
.
These
two
species
appear
to
broaden
the
UUILT
range
to
71.6­
80.6
°
F
(
22­
27
°
C)
for
the
Salmonidae.
The
Cyprinidae
and
Centrarchidae
are
significantly
more
tolerant
of
warm
water.
However,
they
are
effective
competitors
to
t
he
coldwater
species
that
are
the
primary
native
species
in
the
Pacific
Northwest,
because
they
are
very
active
feeders
at
temperatures
>
68
°
F
(
20
°
C).
This
capability
allows
Cyprinidae
and
Centrarchidae
to
increasingly
exclude
cold­
water
species
at
temperatures
in
this
range.
This
is
a
partial
explanation
for
the
disappearance
of
salmonids
from
streams
when
maximum
temperatures
are
in
the
range
of
71.6­
75.2
°
F
(
22­
24
°
C)
(
see
McCullough
1999).

The
small
range
in
UUILT
among
all
the
salmonids
surveyed
and
the
lack
of
overlap
with
the
ranges
expressed
by
the
cyprinids
and
centrarchids
indicates
fundamental
differences
among
major
families
of
fish
and
a
narrow
window
within
which
pot
ential
adaptations
would
likely
be
expressed.
If
the
differences
among
species
within
a
family
are
so
minimal,
it
is
unlikely
that
25
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
significant
differences
would
emerge
within
a
species
(
i.
e.,
at
a
stock
level).

The
UUILT
values
listed
above
for
salmonids
represent
essentially
the
juvenile
life
stages.
Studies
have
been
cited
here
showing
that
UUILT
values
for
adult
salmon
tend
to
be
3.6­
5.4
°
F
(
2­
3
°
C)
lower
than
those
for
juveniles
of
the
species.
This
response
of
adults
in
freshwater
may
be
linked
to
the
preferred
temperatures
in
ocean
environments
that
the
fish
inhabited
for
several
years
prior
to
their
entry
into
rivers.

Differences
in
response
in
thermal
tests
can
usually
be
attributed
in
part
to
test
conditions.
Numerous
factors
can
be
listed
as
reasons
for
differences
in
responses
among
studies
for
a
given
species.
Different
test
results
appear
to
be
more
common
in
tests
of
temperature
preference
than
in
UILT
tests.
Test
apparatus
has
a
role
in
determining
results
as
well
as
season,
sex,
size,
and
so
on.
Because
preference
involves
behavioral
traits
and
appears
to
be
less
precise
an
index
to
estimate,
UILT
values
are
emphasized
in
this
discussion.

Studies
of
UILT
on
salmonids,
cyprinids,
and
centrarchids
conducted
by
Cherry
et
al.
(
1977)
can
be
assumed
to
eliminate
pot
ential
methodological
variations.
These
researchers
found
t
hat
the
UUILTs
for
these
fish
families
were
73.4­
77,
78.8­
96.8,
and
95­
96.8
°
F
(
23­
25,
26­
36,
and
35­
36
°
C),
respectively.
The
salmonids
tested
in
this
study
included
rainbow
trout,
brown
trout,
and
brook
trout.
Brett
(
1952)
measured
UUILT
on
several
salmon
species
(
O.
tshawytscha,
O.
kisutch,
O.
gorbuscha,
O.
keta,
and
O.
nerka).
Brett's
work
is
the
most
complete
analysis
of
thermal
effects
on
fish
physiology
available
in
the
literature.
It
provides
a
useful
comparison
of
these
five
species
and
can
also
be
said
to
eliminate
variation
att
ributed
to
methodology.
He
found
that
among
species
of
Pacific
salmon
the
UUILT
values
varied
only
from
74.8
to
77.2
°
F
(
23.8­
25.1
°
C).
Similarly,
when
CTM
method
was
used
to
test
thermal
tolerance
of
five
species
of
trout
(
rainbow,
brown,
brook,
Gila,
and
Arizona
trout),
CTM
values
of
84.9,
85.8,
85.6,
85.3,
and
84.9
°
F
(
29.4,
29.9,
29.8,
29.6,
and
29.4
°
C,)
respectively,
were
determined
(
Lee
and
Rinne
1980).
All
species
were
collected
in
the
southwestern
United
States.
The
rainbow,
brown,
and
brook
trout
were
introduced
and
the
Gila
and
Arizona
trout
were
native
to
this
climatic
region.
Despite
these
differences
in
geographic
origin,
species,
and
cultural
history
(
hatchery/
wild),
CTM
values
differed
by
a
maximum
of
0.9
°
F
(
0.5
°
C)
among
species.
(
Note
that
CTM
and
UILT
test
methodologies
are
fundamentally
different
and
yield
different
kinds
of
information
on
thermal
tolerance.)

A
recent
study
(
Myrick
and
Cech
2000)
of
thermal
physiology
in
two
rainbow
trout
strains
(
Eagle
Lake
and
Mt.
Shasta)
from
California
lakes
revealed
no
strain­
related
differences
in
thermal
tolerance,
and
moreover
found
that
CTM
values
for
these
rainbow
trout
strains
were
very
similar
to
values
found
for
many
other
salmonids,
including
brook
trout,
brown
trout,
Atlantic
salmon,
Gila
trout,
another
rainbow
trout
stock,
and
Little
Kern
River
golden
trout.

What
is
the
variation
in
thermal
response
within
a
species?

One
of
the
most
extensive
and
earliest
evaluations
of
geographic
variation
in
UILT
available
is
by
Hart
(
1952).
Comparisons
were
made
of
stocks
from
10
species
ranging
in
distribution
from
Ontario
to
Tennessee
to
Florida.
Stock
differences
in
UILT
were
found
in
only
three
of
these
species,
but
in
these
cases
the
stocks
were
taxonomically
distinct
subspecies
that
also
were
26
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
differentiated
morphologically.
In
two
species,
each
having
recognized
subspecies,
there
were
no
differences
in
UILT
or
lower
incipient
lethal
temperature
(
LILT)
values.
Another
two
species
having
subspecies
were
not
different
in
UILT
but
might
have
differed
in
LILT.
In
two
species
having
no
recognized
subspecies,
the
stocks
sampled
over
t
his
large
geographic
range
had
no
geographic
differences
in
UILT.
Hart
concluded
that
the
southern
stocks
of
a
species
had
no
greater
resistance
to
high
temperature
than
the
northern
stocks,
the
exception
being
if
they
were
taxonomically
and
morphologically
distinct.
Even
then
there
were
not
always
differences.
Among
the
species
studied,
each
tended
to
occupy
similar
thermal
regimes
across
the
extent
of
its
range.

Similar
results
were
found
by
McCauley
(
1958)
in
thermal
tolerance
tests
o
f
Salvelinus
spp.
McCauley
found
that
two
stocks
of
Salvelinus
fontinalis
failed
to
reveal
any
difference
in
response.
However,
McCauley
repo
rted
a
difference
in
response
between
two
subspecies
of
S.
alpinus,
(
S.
a.
willughbii
and
S.
a.
alpinus).
However,
the
geometric
mean
resistance
at
1,000
min
exposure
occurred
at
approximately
76.5
°
F
(
24.7
°
C)
with
S.
a.
willughbii
and
at
75.9
°
F
(
24.4
°
C)
with
S.
a.
alpinus.
Even
though
McCauley
reported
a
highly
significant
difference
between
the
subspecies,
the
actual
difference
in
thermal
tolerance
was
negligible
in
a
management
context.

In
CTM
tests
of
two
stocks
of
Lahontan
cutthroat
trout,
Vigg
and
Koch
(
1980)
found
that
variation
owing
to
strain
differences
was
approximately
0.18­
0.9
°
F
(
0.1­
0.5
°
C),
but
that
differences
owing
to
water
source
(
i.
e.,
alkalinity)
were
36.8­
7.2
°
F
(
2.7­
2.9
°
C).
Konecki
et
al.
(
1993)
found
that
when
acclimatization
effects
were
eliminated
for
Washington
coho
stocks
collected
from
streams
with
greatly
different
thermal
environments,
there
was
no
significant
difference
in
CTM
values.
Sonski's
(
1984)
test
of
three
stocks
of
rainbow
trout,
including
redband
trout,
revealed
no
more
than
1.4
°
F
(
0.8
°
C)
difference
in
UILT
values.
In
thermal
testing
of
two
subspecies
of
largemouth
bass
(
Florida
and
northern)
acclimated
to
89.6
°
F
(
32
°
C),
CTM
values
were
41.8
°
C
±
0.4
SD
and
40.9
°
C
±
0.4
SD,
respect
ively
(
Fields
et
al.
1987).
But
the
authors
questioned
whether
these
differences
were
biologically
meaningful;
they
considered
the
chronic
thermal
maximum
to
be
more
meaningful.
These
values
were
39.2
°
C
±
0.64
and
37.3
°
C
±
0.60,
respectively.
These
differences
were
expressed
only
at
the
highest
(
i.
e.,
89.6
°
F
[
32
°
C])
acclimation
temperature
and
may
indicate
a
selective
advantage
of
the
Florida
subspecies
over
the
northern
under
conditions
of
high
thermal
stress.
Again,
these
differences
are
only
expressed
at
a
subspecies
level
and
are
not
great
in
magnitude.

Beacham
and
Withler
(
1991)
studied
the
survival
of
ocean­
type
and
stream­
type
juvenile
chinook
in
high
water
temperatures.
Twenty
separate
full­
sib
families
of
the
ocean­
type
(
hatchery)
and
32
full­
sib
families
of
the
stream­
type
chinook
(
wild)
were
produced
from
gamete
collections
and
matings
of
1
male
with
each
of
2
females.
The
stream­
type
population,
rearing
at
70.7
°
F
(
21.5
°
C),
had
a
total
mortality
of
79%
after
16
d.
The
ocean­
type
population,
rearing
at
71.6
°
F
(
22
°
C),
had
a
total
mortality
of
74%
after
18
d.
These
populations
responded
very
similarly
to
high
temperature
(
approximately
71.6
°
F
[
22
°
C])
in
about
18
d
of
expo
sure,
but
the
cumulative
mortality
curves
were
very
different.
The
st
ream­
type
population
had
approximately
70%
mortality
after
8
d,
whereas
the
ocean­
type
population
suffered
only
3%
mortality
in
the
same
time
period.
These
different
patterns
of
mortality
are
likely
a
result
of
adaptive
differences
in
the
populations
(
Beacham
and
Withler
1991).
The
authors
speculated
that
ocean­
type
chinook
27
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
are
better
adapted
to
warmer
water
conditions
because
they
spend
a
greater
portion
of
their
life
cycle
in
coastal
waters.

A
study
of
thermal
influences
on
physiology
of
two
rainbow
trout
strains
(
Eagle
Lake
and
Mt.
Shasta)
revealed
no
differences
in
thermal
tolerance
as
measured
by
the
CTM
method
(
Myrick
and
Cech
2000).
The
Eagle
Lake
rainbow
trout
(
O.
m.
aquiliarum),
originally
native
to
Pine
Creek,
California,
has
been
artificially
propagated
since
1956
because
of
concerns
for
habitat
degradation.
The
Mt.
Shasta
strain
is
an
inbred
hatchery
strain
derived
from
a
southeast
Idaho
trout
farm
and
Hot
Creek
strain
rainbow.
In
addition,
the
authors
found
no
differences
in
conversion
efficiency,
oxygen
consumption
rates,
or
swimming
performance.

Is
there
sign
ificant
gene
tic
flexibility
within
a
stock
tha
t
would
allow
for
ad
aptation
to
thermal
regimes?

Beacham
and
Withler
(
1991)
hypothesized
that
the
ocean­
type
population,
having
a
shorter
period
of
freshwater
residence
than
the
stream­
type
population,
is
better
adapted
to
warmer
waters
as
found
in
the
ocean
and
also
in
its
freshwater
habitats.
Consequently,
the
ocean­
type
population
is
bet
ter
adapted
to
short
­
term
exposure
to
high
water
temperature
than
is
the
stream­
type
population.
It
is
interesting
that
despite
the
differences
in
response
to
temperature
within
the
first
few
days,
the
two
British
Columbia
populations
had
similar
cumulative
mortalities
over
a
16­
to
18­
d
period.

These
authors
speculated
that
the
UILT
for
salmonids
may
vary
by
population,
depending
on
their
hist
ory
of
adaptation
to
temperature
regimes.
Differences
in
thermal
to
lerance
were
noted
in
time
to
death.
At
70.7
°
F
(
21.5
°
C)
the
entire
stream­
type
t
est
populat
ion
(
i.
e.,
all
families
of
the
stream­
type
populat
ion)
had
a
mean
time
to
death
of
3.4
(
0.10)
d.
At
71.6
°
F
(
22
°
C)
the
ocean­
type
population
had
a
mean
time
to
death
of
13.3
(
0.11)
d.
The
standard
error
for
the
stream­
type
population
in
time
to
death
was
approximately
3%;
that
among
the
ocean­
type
population
was
approximately
0.8%.
The
ocean­
type
population
had
a
greater
short­
term
tolerance
of
warm
water
temperatures
than
the
stream­
type
population,
but
had
a
reduced
additive
genetic
variation
in
mean
time
to
death.
The
estimated
heritability
of
mortality
rate
and
time
to
death
for
the
ocean­
type
chinook
population
was
zero.
These
results
indicat
e
that
the
ocean­
type
population
had
very
little
capacity
for
increased
adaptation
to
warmer
water
temperatures
because
it
was
fully
adapted
to
the
warmer
summer
conditions
found
in
its
coastal
stream.
However,
the
stream­
type
population
had
additive
genetic
variation
for
survival
at
high
temperatures
and
time
to
death
that
could
allow
it
to
further
adapt
to
high
water
temperatures.

Besides
survival,
what
other
key
biotic
responses
influenced
by
temperature
vary
among
stocks?

Growth.
Growth
is
a
good
indicator
of
performance
of
a
species
at
various
temperatures.
When
fed
to
satiation,
chinook
achieved
maximum
growth
rates
at
66
°
F
(
19
°
C)
(
Brett
et
al.
1982).
However,
at
this
temperature,
under
satiation
feeding,
Big
Qualicum
chinook
juveniles
(
approximately
3
g)
grew
at
a
rat
e
of
3.5%/
d,
whereas
the
Nechako
stock
had
a
significantly
lower
growth
rate
of
only
2.9%/
d.
Brett
et
al.
(
1982)
considered
this
difference
to
be
a
genetically
controlled
means
for
one
stock
to
achieve
greater
growth,
especially
in
the
optimum
28
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
temperature
range.
In
addition,
examination
of
growth
rates
on
Sacramento
River
chinook
revealed
that
at
68­
69.8
°
F
(
20­
21
°
C),
sublethal
growth
stress
becomes
significant
for
fish
fed
to
satiation
(
Marine
1997).
These
data
indicate
consistency
in
temperature
thresholds,
whereas
actual
growth
rates
differ
somewhat
among
stocks.

Wangila
and
Dick
(
1988)
studied
the
growth
response
of
two
strains
of
rainbow
trout
(
O.
mykiss)
and
their
hybrid
at
45
and
59
°
F
(
7
and
15
°
C).
The
two
strains,
Mt
.
Lassen
and
Tagwerker,
were
symbolized
as
LAS
and
TAG.
There
were
four
families
of
LAS,
three
of
TAG,
and
four
crosses
of
LAS
x
TAG.
Each
family
was
produced
by
matings
of
a
single
pair
of
parents.
Progeny
of
each
family
were
divided
into
four
groups
of
75
individuals
each,
two
of
which
were
tested
at
45
°
F
(
7
°
C)
and
the
other
two
at
59
°
F
(
15
°
C).
Trout
were
fed
three
times
per
day
to
satiation,
so
growth
rates
should
be
considered
maximum
at
each
temperature.
Wangila
and
Dick
found
significant
differences
among
strains
and
hybrid
in
specific
growth
rates
as
a
function
of
body
weight
during
growth
between
July
8
(
mean
st
arting
weight
3.3­
4.5
g)
and
October
15
(
ending
weights
10.5­
13.9g).
Growth
was
modeled
with
the
equation
log
e
G
=
a
+
b
log
e
W.

Slopes
for
the
regression
of
specific
growth
rate
on
mean
weight
were
significantly
different
among
the
two
strains
and
hybrid
at
45
°
F
(
7
°
C),
but
not
at
59
°
F
(
15
°
C).
The
high
degree
of
heterogeneity
of
slopes
at
45
°
F
(
7
°
C)
suggests
that
genetic
differences
were
significant
among
stocks
when
growth
took
place
at
temperatures
far
below
the
growth
optimum.
However,
at
temperatures
near
the
growth
optimum,
heterogeneity
in
slopes
for
this
regression
was
very
low.
This
study
leaves
unanswered
how
the
stocks
would
respond
under
a
temperature
above
the
growth
optimum.
It
could
be
that
under
stress,
one
stock
would
be
able
to
convert
more
of
its
food
intake
t
o
growth,
or
its
ability
to
feed
at
high
temperatures
might
be
greater
than
for
the
competing
stock.

Sadler
et
al.
(
1986)
tested
differences
in
specific
growth
rate
(
a
measure
that
assumes
exponential
growth)
for
two
rainbow
trout
strains
at
constant
temperatures
of
50
°
F
(
10
°
C)
and
61
°
F
(
16
°
C).
Significant
differences
in
strain
N
and
S
occurred
at
10
°
C
(
1.80
±
0.04
vs.
2.03
±
0.02)
(
±
SE)
and
at
16
°
C
(
2.29
±
0.11
vs.
3.00
±
0.09),
respectively.
Both
stocks
achieved
higher
growth
rates
at
the
higher
temperatures,
which
would
be
nearer
the
preferred
temperature
of
rainbow.
The
authors
attributed
the
greater
growth
rate
of
the
S
stock
(
Soap
Lake,
US,
domesticated
stock)
to
its
hatchery
selection
for
high
growth
rate
compared
with
the
N
strain
derived
from
wild
stock
from
a
river
in
Ontario.

A
study
of
two
strains
of
rainbow
trout
from
California
lakes
(
Eagle
Lake
subspecies
and
Mt.
Shasta
strain)
revealed
no
differences
in
food
consumption,
gross
conversion
efficiency,
resting
routine
oxygen
consumption
rate,
upper
CTM,
or
critical
swimming
velocity.
However,
over
a
temperature
range
including
50,
57.2,
66.2,
71.6,
and
77
°
F
(
10,
14,
19,
22,
and
25
°
C)
constant
temperature
growth
experiments,
the
Mt.
Shasta
strain
had
a
significantly
greater
growth
rate
than
the
Eagle
Lake
strain
only
at
71.6
and
77
°
F
(
22
and
25
°
C).
At
71.6
and
77
°
F
(
22
and
25
°
C),
growth
rates
for
these
two
strains
were
2.97%
vs.
3.51%
body
weight/
d
and
­
0.35%
and
0.05%
body
weight/
d,
respectively.
When
compared
with
other
rainbow
sto
cks
from
widely
separated
geographic
locales
at
71.6
°
F
(
22
°
C),
the
growth
rates
were
similar
to
those
from
Rainbow
Springs
Hatchery,
Ontario,
reported
by
Alsop
and
Wood
(
1997),
lower
than
those
for
29
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
Lake
Superior
rainbow
trout
(
3.94%
body
weight/
d)
(
Hokanson
et
al.
1997),
and
greater
than
reported
for
Oregon
juvenile
steelhead
(
1.7%
body
weight/
d,
at
72.5
°
F
[
22.5
°
C])
(
Wurtsbaugh
and
Davis
1977b,
as
reported
by
Myrick
and
Cech
2000).
However,
Myrick
and
Cech
(
2000)
attributed
much
of
the
difference
among
stocks
to
differences
in
juvenile
weight.
Weight
of
test
specimens
in
the
studies
above
by
Myrick
and
Cech
(
2000),
Hokanson
et
al.
(
1997),
Wurtsbaugh
and
Davis
(
1997b),
and
Alsop
and
Wood
(
1997)
were
2.3­
4.2
g,
0.2­
0.3
g,
1­
1.2
g,
and
6­
7
g,
respectively.
On
the
basis
of
studies
of
growth
at
constant
temperatures
within
the
overall
range
50­
77
°
F
(
10­
25
°
C),
Myrick
and
Cech
(
2000)
inferred
an
optimal
growth
rate
between
57.2
and
66.2
°
F
(
14
and
19
°
C),
bracketing
the
optima
found
by
both
Hokanson
et
al.
(
1977)
and
Briggs
and
Post
(
1997,
cited
by
Myrick
and
Cech
2000).

Swimming
speed.
Myrick
and
Cech
(
2000)
measured
the
critical
swimming
velocities
of
two
rainbow
trout
strains
assumed
to
be
genetically
different
(
juvenile
Eagle
Lake
and
Mt.
Shasta
trout
from
California
lakes)
over
a
temperature
range
from
50
to
66.2
°
F
(
10­
19
°
C).
They
reported
that
length­
specific
critical
swimming
velocities
were
not
statistically
different.
By
plotting
critical
swimming
speeds
(
Figure
1)
from
the
literature
summarized
by
Myrick
and
Cech
(
2000),
it
appears
that
the
various
trout
stocks
(
rainbow/
steelhead
and
golden
trout)
had
swimming
optima
of
57.2­
59
°
F
(
14­
15
°
C).
Only
the
Little
Kern
River
golden
trout
exhibited
a
sharp
decline
in
critical
velocity
at
temperatures
above
57.2
°
F
(
14
°
C).
No
studies
were
conducted
at
temperatures
greater
than
68
°
F
(
20
°
C),
but
one
would
assume
that
at
some
temperature
between
68
and
77
°
F
(
20
and
25
°
C)
a
more
dramatic
decline
in
swimming
speed
would
take
place.
The
literature
summarized
in
Figure
1
indicates
that
critical
swimming
velocity
(
BL/
s
or
body
length
per
second)
generally
declines
with
total
body
length
in
juveniles
over
the
range
85­
287
mm,
although
this
conclusion
is
formed
by
lumping
all
trout
stocks.
Body
length
then
appears
to
be
more
significant
as
a
so
urce
of
variation
in
critical
swimming
speed
than
is
genetic
differences.
However,
at
50
°
F
(
10
°
C),
Myrick
and
Cech
(
2000)
noted
a
significantly
great
er
critical
swimming
velocity
in
strains
of
co
astal
cutthroat
trout
(
Aberdeen
strain)
and
steelhead
(
Aberdeen
strain)
than
for
Eagle
Lake
rainbow,
Mt.
Shasta
rainbow,
Little
Kern
River
golden
trout,
and
coastal
cutthroat
trout
(
Shelton
strain),
which
were
more
similar.
Stocks
tested
at
50
°
F
(
10
°
C)
varied
in
length
from
89
to
120
mm.
Differences
in
swimming
speed
were
not
obviously
related
to
body
length.
30
Summary
of
Technical
Literature
Examining
the
Physiological
Effects
of
Temperature
SUPPORTING
DISCUSSION
AND
LITERATURE
 
SUBLETHAL
EFFECTS
Incubation
and
Early
Fry
Development
Which
temperatures
provide
optimum
conditions
for
incubation
and
early
fry
development
in
the
following
species?

Chinook
salmon.
Once
spawning
has
taken
place,
the
eggs
of
chinook
salmon
hatch
in
about
2
months
and
the
young
remain
in
the
gravel
for
2­
3
wk
before
emerging.
Many
researchers
have
tested
incubation
survival
at
constant
exposure
to
various
test
temperatures.
Complete
mortality
(
100%)
has
been
noted
at
incubation
temperatures
from
57
to
66.9
°
F
(
13.9­
19.4
°
C)
(
Donaldson
1955,
Garling
and
Masterson
1985,
Seymour
1956,
Eddy
1972,
as
cited
in
Raleigh
et
al.
1986).
Significant
mortality
(
over
50%)
has
been
noted
at
constant
incubation
temperatures
from
49.8
to
62
°
F
(
9.9­
16.7
°
C)
(
Donaldson
1955,
Seymour
1956,
Burrows
1963,
Bailey
and
Evans
1971,
as
cited
in
Alderdice
and
Velsen
1978;
Hinze
1959,
as
cited
in
Healy
1979).
A
constant
incubation
temperat
ure
of
46.4
°
F
(
8
°
C)
produced
more
robust
alevin
and
fry
Figure
1.
Critical
swimming
velocity
as
a
function
of
water
temperature.
Data
source
was
tabulated
in
Myrick
and
Cech
(
2000).
