United
States
Environmental
Protection
Agency
EPA­
910­
D­
01­
001
May
2001
Issue
Paper
1
Salmonid
Behavior
and
Water
Temperature
Prepared
as
Part
of
EPA
Region
10
Temperature
Water
Quality
Criteria
Guidance
Development
Project
Sally
T.
Sauter,
U.
S.
Geological
Survey
John
McMillan,
Hoh
Tribe
Jason
Dunham,
U.
S.
Forest
Service
Salmonid
Behavior
and
Water
Temperature
Contents
Abstract
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1
Introduction
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2
What
are
final
and
acute
preference
temperature?
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11
What
is
acclimation
temperature?
How
does
it
influence
the
acute
preference
temperature
of
salmonids?
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11
What
other
ecological
factors
influence
the
acute
preference
temperature
of
salmonids?
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12
Why
does
food
availability
in
the
wild
and
under
laboratory
conditions
affect
water
temperatures
selected
by
salmonids?
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13
How
does
water
temperature
affect
the
feeding
behavior
of
salmonids?
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13
How
does
water
temperature
affect
salmonid
behavior
at
different
life
stages?
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14
Larvae
and
juveniles
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14
Smolts
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15
Adult
potamodromous
migrations
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15
Spawning
migrations
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15
Adult
holding/
refugia
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16
Spawning
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17
Do
ecological
interactions
influence
the
behavior
of
salmon?
What
about
observations
of
individual
salmonids
using
habitat
that
lab
studies
suggest
is
too
warm?
Don't
these
observations
suggest
that
the
laboratory­
based
data
are
skewed?
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17
Does
water
temperature
affect
the
predator
avoidance
behavior
of
juvenile
salmonids?
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19
Does
water
temperature
affect
the
predatory
fish
that
feed
on
juvenile
salmonids?
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20
What
is
competition
and
how
does
water
temperature
influence
it?
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21
Does
water
temperature
affect
competition
between
nonnative
salmonids,
such
as
brook
trout,
and
native
salmonids?
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21
Does
water
temperature
influence
intraspecific
competition
between
native
salmonids?
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22
Does
water
temperature
influence
interspecific
competition
between
salmonids
and
other
fishes?
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23
What
is
the
role
of
cold­
water
refugia
in
salmonid
habitat?
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23
How
do
salmonids
use
cold­
water
refugia?
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24
Conclusion
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25
Literature
Cited
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27
1
Salmonid
Behavior
and
Water
Temperature
Issue
Paper
1
Salmonid
Behavior
and
Water
Temperature
Prepared
as
Part
of
Region
10
Temperature
Water
Quality
Criteria
Guidance
Development
Project
Sally
T.
Sauter,
John
McMillan,
and
Jason
Dunham
Abstract
Animals
react
not
only
to
immediate
changes
in
their
environment
but
also
to
cues
that
signal
long­
term
changes
to
which
they
must
adapt
to
survive.
A
proximate
factor
stimulates
an
animal's
immediate
behavioral
response,
whereas
what
is
known
as
an
ultimate
factor
causes
an
animal
to
adjust
its
behavior
to
evolving
conditions,
thereby
increasing
its
fitness
and
chances
of
long­
term
survival.
The
Salmonid
family
are
cold­
blooded
organisms
that
can
respond
to
an
uncomfortable
water
temperature
by
moving
from
one
spot
to
another
to
maintain
thermal
comfort.
If
the
reason
they
move
is
because
of
a
discrepancy
between
the
temperature
of
the
surrounding
water
and
a
"
set
point"
in
their
brains
that
registers
thermal
comfort,
their
response
is
known
as
behavioral
thermoregulation.
In
this
paper
we
discuss
two
kinds
of
behavioral
thermoregulation:
reactive
and
predictive.
The
reactive
kind
is
in
response
to
discomfort
that
is
temporary
and
short
term,
and
so
it
is
a
response
to
a
proximate
factor,
as
described
above.
Predictive
thermoregulation
occurs
when
the
temperature
of
the
water
in
which
salmonids
choose
to
swim
reflects
their
adaptation
over
time
to
a
changing
environment
and
thus
is
a
response
to
an
ultimate
factor,
as
described
above.
Sometimes
water
temperature
stimulates
behavior
that
has
nothing
to
do
with
thermal
comfort.
What
is
known
as
orientation
behavior
occurs
when
water
temperature
cues
fish
to
locate
prey
or,
say,
reduce
competition
with
other
fish.

In
natural
environments,
the
proximate
and
ultimate
ecological
factors
driving
thermal
behavior
are
frequently
complex
and
not
easily
separated.
Understanding
the
underlying
mechanisms
and
adaptive
value
of
a
behavioral
response
nonetheless
is
helpful
when
considering
the
influence
of
anthropogenic
or
human­
caused
changes
in
water
temperature
on
salmonid
populations.

When
human
activity
alters
water
temperature,
the
impact
may
interfere
with
the
successful
adaptations
that
salmonids
have
made
to
local
conditions
and
historical
temperature
patterns
in
the
Pacific
Northwest.
Higher
peak
summer
water
temperatures
caused
by
human
activity,
for
example,
may
reduce
or
even
eliminate
salmonid
feeding
in
some
streams,
increase
harmful
metabolic
effects,
and
increase
the
feeding
activity
of
fish
that
prey
on
juvenile
salmonids.
To
counter
these
negative
effects
brought
on
by
higher
temperatures
and
to
ensure
the
long­
term
survival
of
native
salmonid
populations,
it
may
be
necessary
to
protect
and
restore
cold­
water
refuges,
which
human
activities
may
be
degrading.
Activities
such
as
irrigation
and
dam
construction
can
harm
cold­
water
refuges
by
reducing
variation
in
water
temperature
and
flow,
reducing
channel
complexity,
and
disrupting
seasonal
recharge
of
groundwater,
whose
flow
2
Salmonid
Behavior
and
Water
Temperature
not
only
protects
resident
salmonids
from
extreme
seasonal
temperature
fluctuations
but
also
may
shelter
migrating
salmonids
that
travel
long
distances.

Introduction
Many
species
of
native
salmonids
inhabit
the
freshwaters
of
the
Pacific
Northwest.
A
large
number
of
these
species
are
anadromous
 
they
migrate
from
the
ocean
to
spawn
in
streams.
Many
species
have
both
anadromous
and
completely
freshwater
forms.
As
a
group,
the
salmonids
display
broad
genetic
flexibility
in
their
physiological,
behavioral,
morphological,
and
developmental
capacity.
This
flexibility
has
fostered
their
rapid
expansion
and
divergence
in
the
highly
diverse
habitats
of
the
Pacific
Northwest.
However,
human
activities
have
eliminated
much
of
this
diversity
and
pose
a
serious
threat
to
the
long­
term
survival
of
remaining
populations.
Much
of
the
decline
in
salmonid
populations
is
directly
attributable
to
the
effects
of
hydroelectric
development
and
land
use
practices
on
water
quality
and
quantity.
Unfavorable
natural
cycles
in
climate
and
ocean
conditions
have
exacerbated
the
human­
induced
decline
in
native
salmonids.

Three
largely
human­
caused
water
temperature
problems
represent
a
serious
and
continuing
threat
to
remaining
native
salmonid
populations
in
Pacific
Northwest
streams:
(
1)
increasing
stream
temperatures,
(
2)
shifts
in
annual
temperature
regimes
(
multiple
external
and
internal
factors
affecting
a
stream's
temperature),
and
(
3)
loss
of
cold­
water
refuges
and
connectivity.
One
reason
for
this
threat
is
that
much
of
salmonid
behavior
is
influenced
by
water
temperature.

Water
temperature
influences
the
behavior
of
fish
more
than
any
other
nonliving
variable
(
Beitinger
and
Fitzpatrick
1979).
Because
salmonids
are
cold­
blooded
organisms
and
live
under
temporally
and
spatially
heterogeneous
thermal
conditions,
water
temperature
can
be
thought
of
as
a
resource
that
fish
utilize
through
behavioral
means
to
control
body
temperature
within
narrow
limits.
Water
temperature
can
serve
as
a
proximate
(
immediate)
or
ultimate
(
evolutionary)
cue
in
a
behavioral
response.
Whenever
the
adaptive
value
of
a
behavioral
response
to
water
temperature
is
body
temperature
regulation,
the
behavioral
response
is
known
as
behavioral
thermoregulation
(
Reynolds
1977).
Behavioral
thermoregulation
helps
salmonids
adapt
through
increased
fitness
and
survival
(
Beitinger
and
Fitzpatrick
1979,
Magnuson
et
al.
1979,
Neill
1979,
Reynolds
and
Casterlin
1979,
Crawshaw
et
al.
1981).

Behavioral
thermoregulation
may
be
either
predictive
or
reactive
(
Neill
1979).
This
delineation
is
based
primarily
on
our
ability
to
predict
the
environmental
temperature.
In
response
to
predictable
thermal
characteristics
of
the
environment,
such
as
seasonal
temperature
changes,
salmonids
show
inheritable
local
behavioral
adaptation.
Salmonids
also
sense
and
respond
to
their
immediate
thermal
environment;
this
is
reactive
behavioral
thermoregulation.

A
salmonid's
behavioral
response
to
water
temperature
is
not
always
behavioral
thermoregulation,
however
(
Reynolds
1977).
Reynolds
provides
the
following
examples
of
evolutionarily
adaptive
nonthermal
ecological
factors
that
can
be
immediately
cued
by
thermal
stimuli:
habitat
selection,
intraspecies
size
segregation,
interspecies
niche
differentiation,
isolating
mechanisms,
predator
avoidance,
prey
location,
escape
reactions,
and
migrations
3
Salmonid
Behavior
and
Water
Temperature
(
thermoperiodic,
daily,
seasonal,
spawning)
(
see
Table
1).
In
a
natural
environment,
it
is
frequently
difficult
to
determine
whether
the
observed
behavioral
responses
of
salmonids
are
primarily
to
water
temperature
or
to
a
combination
of
ecological
cues,
such
as
water
temperature,
daily
exposure
to
light,
and
stream
flow.
However,
water
temperature
is
a
controlling
factor
for
all
biochemical
and
physiological
processes,
and
exerts
strong
influence
on
salmonid
behavior.

Table
2
lists
the
behavioral
thermoregulatory
responses
of
salmonids
to
water
temperature
by
species
and
life
stage.
The
table
summarizes
the
available
scientific
literature
on
salmonid
preference
and
avoidance
temperatures.
Some
of
the
literature
provides
clear
examples
of
innate
thermal
preferences
of
different
salmonids
during
their
life
cycle.
These
preferences
are
determined
through
evolutionary
adaptation
to
predictable
annual
thermal
regimes
and
are
examples
of
predictive
behavioral
thermoregulation.
In
Table
2,
the
laboratory­
derived
preference
temperatures
of
salmonids
are
listed
under
acute
and
final
preference
temperatures.
Acute
preference
temperatures
are
influenced
by
acclimation
temperature,
which
is
discussed
later
in
this
paper.

The
literature
also
discusses
the
avoidance
temperatures
of
salmonids
at
specific
life
history
stages.
Avoidance
of
extreme
water
temperatures
falls
under
reactive
behavioral
thermoregulation,
and
these
data
are
presented
when
available.
Like
acute
preference
temperature,
acute
avoidance
temperature
is
strongly
influenced
by
the
acclimation
history
of
fish.
The
preferred
and
avoidance
temperatures
of
native
salmonids
have
not
always
been
investigated
for
different
life
stages
under
controlled
laboratory
conditions.
When
available,
we
have
included
primary
literature
in
Table
2
that
suggests
the
preferred
and
avoidance
temperatures
of
different
salmonids
based
on
observations
in
the
field
of
fish
distributions.
However,
water
temperatures
collected
during
field
observations
of
salmonids
reflect
the
influence
of
many
ecological
factors
besides
water
temperature
that
act
on
fish
in
their
natural
habitat.
Although
laboratory
studies
are
very
different
from
conditions
in
the
wild,
a
laboratory
approach
does
allow
the
effects
of
temperature
to
be
studied
under
controlled
conditions.
Even
under
controlled
laboratory
conditions,
differences
between
studies
in
feeding
protocol,
temperature
at
which
fish
are
acclimated,
and
whether
fish
are
held
under
fluctuating
or
constant
temperature
cycles
all
influence
the
preference
and
avoidance
temperatures
of
salmonids.
In
general,
the
acute
preference
temperature
of
salmonids
increases
with
increasing
acclimation
temperature
(
Cherry
et
al.
1975),
and
salmonids
on
restricted
rations
tend
to
prefer
lower
water
temperatures
than
their
well­
fed
cohorts
(
Brett
1971).

Table
1.
Summary
of
the
three
kinds
of
behavioral
responses
to
water
temperature
Behavioral
Response
Proximate
Factor
Ultimate
Factor
Adaptive
Value
Time
Period
Predictive
behavioral
thermoregulation
Thermal
or
nonthermal
cue
Water
temperature
Body
temperature
regulation
Evolutionary
Reactive
behavioral
thermoregulation
Thermal
cue
Water
temperature
Body
temperature
regulation
Immediate
Orientation
behavior
Thermal
cue
Nonthermal
ecological
factor
Varies
 
see
text
for
examples
Immediate
4
Salmonid
Behavior
and
Water
Temperature
Table
2.
Summary
of
scientific
studies
on
preference
and
avoidance
temperatures
of
salmonids
Species:
Bull
trout
(
Salvelinus
confluentus)

Life
stage
Location;
wild/
hatchery
Aquatic
system
Preferred
field
temp
°
F
(
°
C)
Acclimation
temp
°
F
(
°
C)
Temp
regime
Citation
juvenile
Throughout
NW
bull
trout
range;
wild
stream
42.8­
48.2
(
6­
9)
AWAT

55.4­
57.2
(

13­
14)
MDMT
N/
A
natural
(
see
text
on
thermal
regimes
below)
Reiman
and
Chandler
1999
juvenile
Lake
Pend
Oreille,
ID;
wild
stream
46.04­
57.02
(
7
.8­
13.9)
MDMT
N/
A
natural
Saffel
and
Scarnecchia
1995
juvenile
Lake
Pend
Oreille,
ID;
wild
stream
46.4­
48.2
(
8­
9)
instantaneous
N/
A
natural
Bonneau
and
Scarnecchia
1996
juvenile
Flathead
River,
MT;
wild
stream

60.62
(

15.0)
unknown
N/
A
natural
Fraley
and
Shepard
1989
juvenile
&
adult
Columbia
River,
Kootenay,
BC,
Canada;
wild
stream
53.6
(
12.0)
MDMT
51.26
(
10.7)
MDAT
52.88
(
11.6)
MWMT
50.36
(
10.2)
MWAT
N/
A
natural
Haas,
unpublished
manuscript
adultspawning
Flathead
River,
MT;
wild
stream

50
(

10.0)
unknown
N/
A
natural
Fraley
and
Shepard
1989
adultupstream
migration
Blackfoot
River,
MT;
wild
stream
63.86
(
17.7)
DAT
N/
A
natural
Swanberg
1997
Species:
Cutthroat
trout
(
Oncorhynchus
clarki)

Life
stage
Location;
wild/
hatchery
Aquatic
system
Preferred
field
temp
°
F
(
°
C)
Acclimation
temp
Temp
regime
Citation
juvenile
&
adult
Lake
Pend
Oreille
drainage,
ID;
wild
stream
50­
57.2
(
10­
14)
instantaneous
N/
A
natural
Bonneau
and
Scarnecchia
1996
Species:
Steelhead
trout
(
Oncorhynchus
mykiss)

Life
stage
Location;
wild/
hatchery
Aquatic
system
Preferred
field
temp
°
F
(
°
C)
Acclimation
temp
Temp
regime
Citation
juvenilesubyearling
South
Umpqua
River,
OR;
wild
river
59
(
15.0)
DMAT
N/
A
natural
Roper
and
Scarnecchia
1994
juvenileyearling
South
Umpqua
River,
OR;
wild
river
64.04
(
17.8)
DMAT
N/
A
natural
Roper
and
Scarnecchia
1994
Life
stage
Location;
wild/
hatchery
Aquatic
system
Avoidance
field
temp
°
F
(
°
C)
Acclimation
temp
Temp
regime
Citation
juvenile
northern
California;
wild
stream

73.4
(

23)
N/
A
natural
Nielsen
et
al.
1994
5
Salmonid
Behavior
and
Water
Temperature
Table
2.
Summary
of
scientific
studies
on
preference
and
avoidance
temperatures
of
salmonids
(
continued)

Species:
Rainbow
trout
(
Oncorhynchus
mykiss)

Life
stage
Location;
wild/
hatchery
Aquatic
system;
feeding
Acute
preference
temp
°
F
(
°
C)
Acclimation
temp
°
F
(
°
C)
Temp
regime
Citation
juvenile
New
and
East
Rivers,
VA,
USA;
hatchery
tank;
starved
(
see
text
above
on
feeding)
52.9
°
F
[
51.1­
53.1]
(
11.6
°
C
[
10.6­
11.7])
54.7
°
F
[
54.5­
56.1]
(
12.6
°
C
[
12.5­
13.4])
57.9
°
F
[
57.9­
59.2]
(
14.4
°
C
[
14.4­
15.1])
62.4
°
F
[
61.2­
62.4]
(
16.9
°
C
[
16.2­
16.9])
64.5
°
F
[
64.2­
65.6]
(
18.1
°
C
[
17.9­
18.7])
68.2
°
F
[
67.5­
69.1]
(
20.1
°
C
[
19.7­
20.6])
71.6
°
F
[
70.5­
72.5]
(
22.0
°
C
[
21.4­
22.5])
42.8
(
6)
48.2
(
9)
53.6
(
12)
59
(
15)
64.4
(
18)
69.8
(
21)
75.2
(
24)

(
see
text
on
acclimation
below)
stable
Cherry
et
al.
1975
juvenile­
1
month
6
months
10
months
12
months
Ontario,
Canada;
hatchery
tank;
unknown
62.7
(
17.08)
62.5
(
16.92)
64.2
(
17.88)
59.4
(
15.21)
62.4
(
16.91)
62.9
(
17.20)
60.4
(
15.75)
51.7
(
10.95)
58.7
(
14.82)
55.1
(
12.85)
47.1
(
8.40)
50.4
(
10.20)
50
(
10)
59
(
15)
68
(
20)
50
(
10)
59
(
15)
68
(
20)
50
(
10)
59
(
15)
68
(
20)
50
(
10)
59
(
15)
68
(
20)
stable
Kwain
and
McCauley
1978
Life
stage
Location;
wild/
hatchery
Aquatic
system;
feeding
Avoidance
temp
°
F
(
°
C)
Acclimation
temp
Temp
regime
Citation
juvenile
New
and
East
Rivers,
VA,
USA;
hatchery
tank;
starved
<
41>
55.4
(<
5
>
13)
<
46.4
>
59
(<
8
>
15)
<
51.8
>
62.6
(<
11>
17)
<
55.4
<
66.2
(<
13
>
19)
<
55.4
<
66.2
(<
13
>
19)
<
60.8
>
73.4
(<
16
>
23)
<
66.2
>
77
(<
19
>
25)
42.8
(
6)
48.2
(
9)
53.6
(
12)
59
(
15)
64.4
(
18)
69.8
(
21)
75.2
(
24)
stable
Cherry
et
al.
1975
6
Salmonid
Behavior
and
Water
Temperature
Table
2.
Summary
of
scientific
studies
on
preference
and
avoidance
temperatures
of
salmonids
(
continued)

Species:
Rainbow
trout
(
Oncorhynchus
mykiss)

Life
stage
Location;
wild/
hatchery
Aquatic
system;
feeding
Final
preference
temp
°
F
(
°
C)
Acclimation
temp
Temp
regime
Citation
subyearling
Otterville,
Ontario,
Canada;
hatchery
tank;
fed
71.6
(
22)
N/
A
stable
Javaid
and
Anderson
1967
subyearling
Otterville,
Ontario,
Canada;
hatchery
tank;
starved
64.4
(
18)
N/
A
stable
Javaid
and
Anderson
1967
subyearling
Campbellville,
Canada;
hatchery
tank;
fed
64.4­
66.2
(
18­
19)
N/
A
stable
McCauley
and
Pond
1971
juvenile
Waterloo
County,
Ontario,
Canada;
hatchery
tank;
unknown
52.3
(
11.3)
N/
A
stable
McCauley
et
al.
1977
adult
unknown
tank;
unknown
55.4
(
13)
N/
A
stable
Garside
and
Tait
1958
adult
New
and
East
Rivers,
VA,
USA;
hatchery
tank;
starved
64.4
(
18)
N/
A
stable
Cherry
et
al.
1975
adult
New
and
East
Rivers
VA,
USA;
hatchery
tank,
starved
66.6
(
19.2)
N/
A
stable
Cherry
et
al.
1977
Life
stage
Location;
wild/
hatchery
Aquatic
system
Final
field
preference
temp
°
F
(
°
C)
Acclimation
temp
°
F
(
°
C)
Temp
regime
Citation
juvenile
&
adult
Columbia
River,
Kootenay,
BC,
Canada;
wild
river
57.6
(
14.2)
MDMT
N/
A
natural
Haas,
unpublished
manuscript
adult
Horsetooth
Reservoir,
Colorado;
unknown
reservoir
66.0­
69.9
(
18.9­
21.1)
ATU
N/
A
natural
Horak
and
Tanner
1964
adult
Lake
Michigan;
unknown
lake
61.7
(
16.5)
unknown
N/
A
natural
Spigarelli
1975
7
Salmonid
Behavior
and
Water
Temperature
Table
2.
Summary
of
scientific
studies
on
preference
and
avoidance
temperatures
of
salmonids
(
continued)

Species:
Spring
chinook
salmon
(
Oncorhynchus
tshawytscha)

Life
stage
Location;
wild/
hatchery
Aquatic
system;
feeding
Acute
preference
temp
°
F
(
°
C)
Acclimation
temp
°
F
(
°
C)
Temp
regime
Citation
subyearling
Dungeness,
WA;
hatchery
tank;
unknown
53.6­
55.4
(
12­
13)
(
all
acclimation
temps)
41,
50,
59,
68,
and
73.4
(
5,
10,
15,
20,
and
23)
stable
Brett
1952
Life
stage
Location;
wild/
hatchery
Aquatic
system;
feeding
Final
preference
temp
°
F
(
°
C)
Acclimation
temp
°
F
(
°
C)
Temp
regime
Citation
subyearling
Dungeness,
WA;
hatchery
tank;
unknown
53.1
(
11.7)
N/
A
stable
Brett
1952
smolt
Little
White
Salmon
N.
F.
H.;
hatchery
tank;
satiation
62.1
(
16.7)
increasing
temp
acclimation,
3.6
(
2)
per
month,
range:
46.4­
57.2
(
8­
14)
stable
Sauter
1996
Life
stage
Location;
wild/
hatchery
Aquatic
system
Preferred
field
temp
°
F
(
°
C)
Acclimation
temp
°
F
(
°
C)
Temp
regime
Citation
adult
Lake
Michigan;
hatchery
lake
63.1
(
17.3)
N/
A
natural
Spigarelli
1975
Species:
Fall
chinook
salmon
(
Oncorhynchus
tshawytscha)

Life
stage
Location;
wild/
hatchery
Aquatic
system;
feeding
Preferred
temp
°
F
(
°
C)
Acclimation
temp
°
F
(
°
C)
Temp
regime
Citation
subyearling
upriver
bright
stock
from
Little
White
Salmon
N.
F.
H.;
hatchery
tank;
satiation
63.1
(
17.3)
increasing
temp
acclimation,
3.6
(
2)
per
month,
range:
53.6­
57.2
(
12­
14)
stable
Sauter
1996
smolt
upriver
bright
stock
from
Little
White
Salmon
N.
F.
H.;
hatchery
tank;
satiation
51.6
(
10.9)
60.8
(
16)
stable
Sauter
1996
8
Salmonid
Behavior
and
Water
Temperature
Table
2.
Summary
of
scientific
studies
on
preference
and
avoidance
temperatures
of
salmonids
(
continued)

Species:
Coho
salmon
(
Oncorhynchus
kisutch)

Life
stage
Location;
wild/
hatchery
Aquatic
system;
feeding
Acute
preference
temp
°
F
(
°
C)
Acclimation
temp
°
F
(
°
C)
Temp
regime
Citation
subyearling
Nile
Creek,
BC,
Canada;
hatchery
tank;
unknown
53.6­
57.2
(
12­
14)
41,
50,
59,
68
and
73.4
(
5,
10,
15,
20
and
23)
stable
Brett
1952
Life
stage
Location;
wild/
hatchery
Aquatic
system;
feeding
Final
preference
temp
°
F
(
°
C)
Acclimation
temp
°
F
(
°
C)
Temp
regime
Citation
subyearling
Bockman
Creek,
WA;
wild
starved
24
hr
prior
to
experiment
52.9
range:
44.6­
69.8
(
11.6
range:
7­
21)
50
(
10)
stable
Konecki
et
al.
1995
subyearling
Bingham
Creek,
WA;
wild
starved
24
hr
prior
to
experiment
69.8
range:
42.8­
60.8
(
9.9
range:
6­
16)
50
(
10)
stable
Konecki
et
al.
1995
adult
Lake
Erie;
hatchery
tank;
unknown
52.5
(
11.4)
unknown
stable
Reutter
and
Herdendorf
1974
Life
stage
Location;
wild/
hatchery
Aquatic
system
Preferred
field
temp
°
F
(
°
C)
Acclimation
temp
°
F
(
°
C)
Temp
regime
Citation
adult
Lake
Michigan;
hatchery
lake
63.1
(
17.3)
N/
A
natural
Spigarelli
1975
Species:
Chum
salmon
(
Oncorhynchus
keta)

Life
stage
Location;
wild/
hatchery
Aquatic
system;
feeding
Acute
preference
temp
°
F
(
°
C)
Acclimation
temp
°
F
(
°
C)
Temp
regime
Citation
juvenilesubyearling
Nile
Creek,
BC,
Canada;
hatchery
tank;
unknown
53.6­
57.2
(
12­
14)
(
all
acclimation
temps)
41,
50,
59,
68
and
73.4
(
5,
10,
15,
20
and
23)
stable
Brett
1952
adultmigration
unknown
stream
44.6­
51.8
(
7­
11)
unknown
N/
A
natural
Groot
and
Margolis
1991
Life
stage
Location;
wild/
hatchery
Aquatic
system;
feeding
Final
preference
temp
°
F
(
°
C)
Acclimation
temp
°
F
(
°
C)
Temp
regime
Citation
subyearling
Nile
Creek,
BC,
Canada;
hatchery
tank;
unknown
57.4
(
14.1)
N/
A
stable
Brett
1952
9
Salmonid
Behavior
and
Water
Temperature
Table
2.
Summary
of
scientific
studies
on
preference
and
avoidance
temperatures
of
salmonids
(
continued)

Species:
Pink
salmon
(
Oncorhynchus
gorbushka)

Life
stage
Location;
wild/
hatchery
Aquatic
system;
feeding
Final
preference
temp
°
F
(
°
C)
Acclimation
temp
°
F
(
°
C)
Temp
regime
Citation
subyearling
Dungeness,
WA;
hatchery
tank;
unknown
53.1
(
11.7)
N/
A
stable
Brett
1952
Life
stage
Location;
wild/
hatchery
Aquatic
system;
feeding
Preferred
field
temp
°
F
(
°
C)
Acclimation
temp
°
F
(
°
C)
Temp
regime
Citation
juvenilesubyearling
Dungeness,
WA;
hatchery
tank;
unknown
53.6­
56.3
(
12­
13.5)
41,
50,
59,
68
and
73.4
(
5,
10,
15,
20
and
23)
stable
Brett
1952
Species:
Sockeye
salmon
(
Oncorhynchus
nerka)

Life
stage
Location;
wild/
hatchery
Aquatic
system;
feeding
Acute
preference
temp
°
F
(
°
C)
Acclimation
temp
°
F
(
°
C)
Temp
regime
Citation
juvenilesubyearling
Issaquah,
WA;
hatchery
tank;
unknown
53.6­
57.2
(
12­
14)
5
°
,
10
°
,
15
°
,
20
°
and
23
°
C
stable
Brett
1952
Life
stage
Location;
wild/
hatchery
Aquatic
system
Acute
avoidance
temp
°
F
(
°
C)
Acclimation
temp
°
F
(
°
C)
Temp
regime
Citation
juvenile
Great
Central
Lake,
BC,
Canada;
wild
lake
<
39.2
>
64.4
(<
4
>
18)
N/
A
natural
LeBrasseur
et
al.
1978
Life
stage
Location;
wild/
hatchery
Aquatic
system;
feeding
Final
preference
temp
°
F
(
°
C)
Acclimation
temp
°
F
(
°
C)
Temp
regime
Citation
subyearling
Issaquah,
WA;
hatchery
tank;
unknown
58.1
(
14.5)
N/
A
stable
Brett
1952
Life
stage
Location;
wild/
hatchery
Aquatic
system
Final
field
preference
temp
°
F
(
°
C)
Acclimation
temp
°
F
(
°
C)
Temp
regime
Citation
subyearling
Babine
Lake,
BC;
wild
lake
51.1
(
15)
±
9
(
5)
DAT
N/
A
natural
Brett
1971
smolts
yearling
&
adult
adult
Cultus
Lake,
BC;
Wild
Horsetooth
Reservoir,
CO;
hatchery;
Okanagan
Reservoir,
WA;
hatchery
lake
reservoir;

Okanagan
reservoir
51.1­
55.0
(
10.6­
12.8)
DAT
N/
A
natural
Foerster
1937;
Horak
and
Tanner
1964;
Major
and
Mighel
1966
10
Salmonid
Behavior
and
Water
Temperature
Table
2.
Summary
of
scientific
studies
on
preference
and
avoidance
temperatures
of
salmonids
(
continued)

Species:
Mountain
whitefish
(
Prosopium
williamsoni)

Life
stage
Location;
wild/
hatchery
Aquatic
system
Preferred
field
temp
°
F
(
°
C)
Acclimation
temp
°
F
(
°
C)
Temp
regime
Citation
adultspawning
Sheep
River,
Alberta,
Canada;
wild
river
32­
46.4
(
0­
8)
DAT
N/
A
natural
Thompson
and
Davies
1976
adultspawning
Montana;
wild
river
<
41.9
(<
5.5)
instantaneous
N/
A
natural
Brown
1952
Life
stage
Location;
wild/
hatchery
Aquatic
system
Acute
preferred
field
temp
°
F
(
°
C)
Acclimation
°
F
(
°
C)
temp
Temp
regime
Citation
adult
Blacksmith
Fork
River,
UT;
wild
river
55.0
(
12.8)
DAT,
prespawning
49.3
(
9.6)
DAT,
postspawning
51.4
(
10.8)
DAT,
winter
61.5
(
16.4)
DAT,
spring
N/
A
natural
Inhat
and
Bulkley
1984
Life
stage
Location;
wild/
hatchery
Aquatic
system
Final
preferred
field
temp
°
F
(
°
C)
Acclimation
temp
°
F
(
°
C)
Temp
regime
Citation
adult
Blacksmith
Fork
River,
UT;
wild
river
63.9
(
17.7)
DAT,
prespawning
53.4
(
11.9)
DAT,
postspawning
49.8
(
9.9)
DAT,
winter
61.3
(
16.3)
DAT,
spring
N/
A
natural
Inhat
and
Bulkley
1984
Temperature
cycle
also
influences
the
preference
temperature
of
fish.
In
the
temperate
climate
of
the
Pacific
Northwest,
water
temperature
varies
daily
and
seasonally,
and
salmonids
in
their
natural
environment
are
exposed
to
fluctuating
water
temperatures.
In
contrast,
all
of
the
laboratory
experiments
cited
in
Table
2
have
acclimated
salmonids
to
a
stable
temperature.
Such
a
regime
is
less
physiologically
demanding
than
naturally
fluctuating
water
temperatures
(
Reynolds
and
Casterlin
1979),
and
if
feeding
and
acclimation
remain
constant,
fish
exposed
to
fluctuating
thermal
regimes
may
prefer
slightly
lower
water
temperatures
than
fish
acclimated
to
a
stable
temperature.
Because
the
experimental
designs
of
thermal
preference
studies
frequently
vary
in
these
important
factors,
Table
2
and
the
questions
and
answers
below
provide
more
information
from
primary
literature
sources
on
the
feeding
protocol,
acclimation
temperature,
and
temperature
cycle.

The
temperature
metrics
for
field
studies
are
given
in
Table
2
when
available;
frequently,
they
were
not
specified
in
the
primary
literature.
For
definition
of
temperature
metric
abbreviations
and
further
information
on
temperature
measurement
and
monitoring,
see
the
Temperature
Measurement
and
Monitoring
issue
paper.

Acute
laboratory
preference
and
avoidance
temperatures
usually
represent
an
average
temperature
calculated
from
multiple
temperature
readings
on
fish
location
in
a
thermal
gradient
taken
over
a
specific
period
of
time.
Final
preference
temperature
also
may
be
an
average,
or
it
may
be
derived
from
the
intercept
of
a
fish's
acclimation
and
acute
preference
temperatures.
11
Salmonid
Behavior
and
Water
Temperature
More
information
on
the
linkages
among
water
temperature,
life
stage,
and
other
ecological
factors
is
provided
in
the
questions
and
answers
below.

What
are
final
and
acute
preference
temperature?

The
final
preference
temperature
is
the
innate,
species­
specific
temperature
preference
of
an
organism
dictated
by
a
thermal
set
point
in
the
brain
(
Hammel
1968
in
Reynolds
1977).
Fish
placed
in
a
laboratory
temperature
gradient
will
move
toward
the
final
preference
temperature.
This
temperature
is
usually
reached
within
24
hours
after
an
animal
has
been
introduced
to
a
laboratory
temperature
gradient
(
Reynolds
and
Casterlin
1979).
Fry
(
1947)
defined
the
final
preference
temperature
as
"
a
temperature
around
which
all
individuals
[
of
a
given
species]
will
ultimately
congregate,
regardless
of
their
thermal
experience
before
being
placed
in
the
gradient"
and
that
temperature
"
at
which
the
preferred
temperature
is
equal
to
the
acclimation
temperature."
Using
this
definition,
the
final
preference
temperature
of
fish
can
be
determined
either
by
using
a
thermal
gradient
or
by
determining
the
acute
preference
temperature
of
fish
held
at
different
temperatures
and
using
regression
to
find
the
intercept
of
acclimation
temperature
with
acute
preference
temperature.

The
ecological
significance
of
a
species'
thermal
preference
is
that
it
frequently
coincides
with
the
species'
thermal
optimum
for
physiological
functioning.
This
optimum
may
shift
with
age
and
during
various
life
history
stages
of
an
animal
(
Reynolds
1977,
McCauley
and
Huggins
1979,
Kelsch
and
Neill
1990).
Innate
thermal
preferences
displayed
by
salmonids
with
age
and
development
reflect
genetic
adaptation
of
species
or
subspecies
(
stocks)
to
predictable
annual
thermal
conditions
in
their
environment
(
Magnuson
et
al.
1979).

The
term
acute
preference
temperature
describes
the
immediate
preference
temperature
of
a
fish
placed
in
a
laboratory
gradient
(
Reynolds
and
Casterlin
1979).
The
acute
preference
temperatures
of
fish
are
measured
within
a
short
period
(
usually
2
h
or
less)
after
the
fish
have
been
introduced
to
a
thermal
gradient.
Acute
preference
temperatures
are
strongly
influenced
by
the
fish's
acclimation
temperature.

What
is
acclimation
temperature?
How
does
it
influence
the
acute
preference
temperature
of
salmonids?

Acclimation
temperature
or
thermal
acclimation
refers
to
the
physiological
and
biochemical
restructuring
of
cellular
and
tissue
components
that
occurs
in
response
to
temperature
variations
of
2­
3
weeks
or
more
under
known
or
specified
thermal
conditions
in
the
laboratory
(
Reynolds
and
Casterlin
1979,
Withers
1992).
In
natural
environments,
both
nonthermal
factors
and
seasonal
changes
in
water
temperature
shape
the
restructuring
of
cells
and
tissues.
The
term
applied
to
this
natural
process
is
acclimatization
(
Reynolds
and
Casterlin
1979,
Crawshaw
et
al.
1990,
Withers
1992).
A
species­
innate
thermal
preference
can
be
altered
over
hours,
days,
and
weeks
by
thermal
acclimation
or
acclimatization
(
Reynolds
and
Casterlin
1979,
Withers
1992).
Thermal
acclimation
or
acclimatization
shifts
the
acute
preferred
temperature,
avoidance
temperatures,
and
thermal
tolerance
range
of
an
animal
as
a
result
of
physiological
adjustment
to
current
thermal
conditions
and
involves
"
feedback
to
the
genetic
material,
and
subsequently
to
the
protein
synthetic
system"
(
Hazel
and
Prosser
1974).
Changes
in
enzyme
12
Salmonid
Behavior
and
Water
Temperature
structure
and
lipid
membranes
are
perhaps
the
most
notable
alterations
seen
in
response
to
variations
in
temperature
(
Withers
1992).
The
result
of
acclimation
or
acclimatization
is
an
increase
in
the
overall
performance
and
survival
of
an
animal
in
its
environment.
Wild
salmonids
acclimatized
to
daily
average
temperatures
in
the
summer
show
slightly
higher
preference
temperatures
than
fish
acclimatized
to
daily
average
winter
temperatures.
The
effect
of
acclimation
temperature
on
the
preference
temperatures
of
rainbow
trout
under
laboratory
conditions
can
be
seen
in
Table
2
(
see
Cherry
et
al.
1975).

Although
salmonids
tend
to
be
adapted
to
a
narrow
temperature
range
(
and
thus
are
stenothermic),
they
show
some
capacity
to
acclimatize
to
higher
daily
and
seasonal
water
temperatures
(
Javaid
and
Anderson
1967,
Cherry
et
al.
1975).
Notable
differences
exist
in
the
degree
of
their
stenothermy
and
capacity
for
thermal
acclimation.
For
example,
the
literature
suggests
that
rainbow
trout
may
have
a
greater
capacity
for
thermal
acclimation
than
do
Pacific
salmon
or
char,
and
char
are
considerably
more
stenothermic
than
native
trout
or
salmon
(
Brett
1952,
Javaid
and
Anderson
1967).

It
is
important
to
remember
that
salmonids
are
physiologically
adapted
to
live
in
cold­
water
environments,
and
their
ability
to
acclimate
to
higher
water
temperatures
is
restricted
to
the
cold­
water
range
of
temperatures
in
which
they
evolved.
Under
laboratory
conditions,
acclimation
may
extend
the
thermal
limits
of
salmonids;
however,
in
nature
growth,
survival,
and
successful
reproduction
are
a
much
more
rigorous
test
of
thermal
tolerances.
Fish
may
be
able
to
physiologically
acclimate
to
some
extreme
thermal
conditions
in
laboratory
settings,
but
face
"
ecological
death"
under
natural
conditions
where
ecological
factors
such
as
food
availability
and
vulnerability
to
predation
are
important
components
of
survival
(
Magnuson
et
al.
1979,
Dickerson
and
Vinyard
1999).
Adaptation
to
higher
environmental
water
temperatures
and
altered
annual
thermal
regimes
may
require
many
generations
(
Nelhsen
et
al.
1991,
Adkison
1995,
Hendry
et
al.
1998);
however,
human­
caused
water
temperature
increases
may
be
of
such
magnitude
and
occur
so
rapidly
that
they
outpace
the
capacity
of
salmonid
populations
to
genetically
adapt
(
Quinn
and
Adams
1996).

What
other
ecological
factors
influence
the
acute
preference
temperature
of
salmonids?

Both
laboratory
and
field
experiments
have
shown
that
food
availability
affects
the
acute
thermal
preference
of
salmonids.
Brett
(
1971)
found
strong
evidence
that
restricted
food
conditions
in
Babine
Lake,
British
Columbia,
resulted
in
a
daily
pattern
of
vertical
migration
in
sockeye
salmon
less
than
1
year
old
(
subyearlings).
These
vertical
migrations
likely
represent
a
behavioral
response
to
both
thermal
stratification
of
the
lake
and
limited
rations.
By
behaviorally
thermoregulating
at
slightly
lower
water
temperatures
during
the
day,
then
migrating
to
the
surface
to
feed
at
dusk
and
dawn,
juvenile
sockeye
salmon
maximize
their
growth
potential
by
conserving
energy
when
food
is
limited.
In
the
laboratory,
Javaid
and
Anderson
(
1967)
starved
juvenile
rainbow
trout
acclimated
at
68
°
F
(
20
°
C)
and
found
that
the
selected
temperature
dropped
from
near
71.6­
64.4
°
F
(
22­
18
°
C)
in
a
day
once
food
was
withheld.
Selected
temperature
of
starved
juvenile
rainbow
trout
remained
at
64.4
°
F
(
18
°
C)
for
2
weeks
until
feeding
was
resumed,
when
fish
again
began
selecting
71.6
°
F
(
22
°
C)
water
temperatures
within
a
day.
13
Salmonid
Behavior
and
Water
Temperature
Another
factor
known
to
influence
temperature
selection
is
a
salmonid's
stock.
Stock
refers
to
populations
of
salmonids
that
originate
from
and
have
adapted
to
the
environmental
conditions
characteristic
of
specific
watersheds
(
Nehlsen
et
al.
1991).
As
mentioned
earlier,
one
environmental
characteristic
that
salmonids
adapt
to
behaviorally
is
predictable
annual
temperature
cycles.
As
a
result,
intraspecies
adaptations
may
be
seen
in
the
temperature
preferences
of
different
stocks
of
salmonids.
For
example,
Konecki
et
al.
(
1995)
found
slight
differences
in
the
temperature
preferences
of
two
populations
of
juvenile
coho
salmon.
Coho
salmon
originating
from
a
stream
with
lower
and
less
variable
water
temperatures
showed
slightly
lower
preference
temperatures
and
temperature
range
than
fish
originating
from
a
more
heterothermal
stream
(
Table
2).

The
age
of
salmonids
also
is
important
in
determining
their
temperature
preference.
Kwain
and
McCauley
(
1978)
found
that
the
preferred
temperature
of
rainbow
trout
decreased
steadily
with
age
(
Table
2).

Very
little
information
is
available
in
the
literature
on
the
effect
that
daily
temperature
fluctuations
have
on
salmonids'
preference
temperature.
Field
and
laboratory
studies
such
as
Brett
(
1971)
and
Hokanson
et
al.
(
1977)
have
found
that
fluctuating
water
temperatures
influence
the
thermoregulatory
behavior
of
salmonids.
Hokanson
et
al.
(
1977)
investigated
the
growth
and
mortality
rates
of
juvenile
rainbow
trout
held
at
constant
and
daily
fluctuating
temperatures
in
the
laboratory.
Rainbow
trout
held
at
daily
fluctuating
temperatures
did
not
acclimate
to
the
average
mean
temperature,
but
to
some
temperature
between
the
minimum
and
maximum
daily
temperature,
and
growth
and
mortality
responses
reflected
water
temperatures
about
34.7
°
F
(
1.5
°
C)
colder
than
fish
held
at
a
constant
temperature.
These
physiological
data
suggest
that
salmonids
acclimated
to
daily
fluctuating
temperature
cycles
may
select
lower
preference
temperatures
than
fish
held
at
constant
temperatures.

Why
does
food
availability
in
the
wild
and
under
laboratory
conditions
affect
water
temperatures
selected
by
salmonids?

The
rates
of
all
biochemical
reactions,
and
therefore
the
metabolic
rates
of
cold­
blooded
fishes,
are
controlled
by
temperature
(
Fry
1971,
Elliot
1976,
Beitinger
and
Fitzpatrick
1979).
As
metabolic
rate
increases
with
temperature,
so
does
the
need
for
food
to
keep
pace
with
metabolic
demand
(
Elliot
1976,
Brett
1995,
Higgs
et
al.
1995,
Jobling
1981)
(
see
Physiology
issue
paper
for
more
information).
Well­
fed
salmonids
tend
to
behaviorally
thermoregulate
at
slightly
warmer
water
temperatures;
the
combination
of
abundant
feeding
opportunities
and
warmer
water
tends
to
maximize
growth.
When
food
is
scarce,
salmonids
will
select
cooler
water
temperatures
to
lower
their
metabolic
rate
and
conserve
energy
stores.

How
does
water
temperature
affect
the
feeding
behavior
of
salmonids?

Increased
water
temperatures
and
a
longer
period
of
warmer
water
temperatures
increase
the
feeding
rate
of
salmonids
provided
that
food
is
not
limiting
and
water
temperatures
do
not
exceed
the
feeding
temperature
range
(
Elliott
1982,
Linton
et
al.
1998).
Linton
et
al.
(
1998)
reported
that
a
+
3.6
°
F
(
2
°
C)
increase
in
annual
water
temperature
regime
increased
the
feeding
rate
of
rainbow
trout
in
the
winter
and
spring
months,
but
significantly
decreased
feeding
rate
at
14
Salmonid
Behavior
and
Water
Temperature
peak
summer
temperatures
68
°
F
(
20
°
C),
leading
to
an
overall
decline
in
growth
rate.
Appetite
suppression
occurred
at
lower
temperatures
in
larger,
older
fish
(
Linton
et
al.
1998).
At
temperatures
above
a
species
preferred
temperature
range,
feeding
rate
may
continue
to
increase
up
to
a
point,
but
growth
potential
decreases
(
Linton
et
al.
1998).
Appetite
suppression,
leading
to
a
decrease
in
feeding
rate
also
occurs
in
fish
as
temperature
increases
above
a
species'
preferred
range
and
may
be
a
result
of
decreased
activity
in
response
to
high
metabolic
demand
(
Jobling
1981,
Linton
et
al.
1998).
Elliott
(
1991)
found
that
Atlantic
salmon
(
Salmo
salar)
stopped
feeding
at
elevated
water
temperatures,
but
quickly
resumed
feeding
once
water
temperature
was
lowered.
Research
indicates
that
the
appetite
of
juvenile
sockeye
salmon
is
completely
inhibited
at
75.2
°
F
(
24
°
C),
and
that
the
return
of
appetite
is
temperature­
dependent
(
Brett
and
Higgs
1970,
Brett
1971).

How
does
water
temperature
affect
salmonid
behavior
at
different
life
stages?

Larvae
and
juveniles.
Juvenile
salmonids
require
a
variety
of
water
temperatures.
In
general,
larvae
and
young
juveniles
tend
to
be
attracted
to
slightly
warmer
water
temperatures
for
feeding
and
growth
than
are
larger
juveniles
and
adult
fish.
The
innate
thermal
preference
of
some
fish
frequently
decreases
from
the
larvae
through
juvenile
stages
(
Magnuson
et
al.
1979,
McCauley
and
Huggins
1979),
although
research
on
age­
related
changes
in
the
thermal
preference
of
salmonids
is
scarce.
Research
by
Kwain
and
McCauley
(
1978)
(
see
Table
2)
on
juvenile
rainbow
trout
found
a
steady
decrease
in
the
thermal
preference
of
rainbow
trout
with
age,
with
larvae
preferring
temperatures
near
66.2
°
F
(
19
°
C),
whereas
yearlings
selected
water
temperatures
of
about
55.4
°
F
(
13
°
C).

McCullough
(
1999)
notes
that
the
higher
thermal
preferences
of
young­
of­
year
(
YOY)
salmonids
may
attract
this
age
group
to
warmer
downstream
waters,
improving
growth
opportunities
early
in
the
season.
The
study
cautioned,
however,
that
as
seasonal
water
temperatures
increase
and
the
preferred
temperature
of
the
YOY
age
class
decreases,
this
age
group
is
least
capable
of
reactive
behavioral
thermoregulation
because
of
limited
swimming
capacity.
YOY
fish
may
be
physically
incapable
of
escaping
unfavorably
high
stream
temperatures
by
migrating
to
cooler
upstream
reaches.

Juvenile
and
adult
salmonids
frequently
move
downstream
to
warmer
water
temperatures
in
the
fall
and
avoid
extreme
cold­
water
conditions
in
upstream
reaches
during
the
winter
(
Bjornn
1971,
Pettit
and
Wallace
1975,
Brown
and
MacKay
1995,
Northcote
1997,
Jakober
et
al.
1998).
Cold
winter
temperatures
are
also
known
to
prompt
reactive
behavioral
thermoregulation
in
juvenile
rainbow
trout
and
coastal
cutthroat
trout.
These
juveniles
will
migrate
downstream
to
overwinter
in
warmer
main­
stem
areas
following
emergence
(
Behnke
1992,
Trotter
1989).
Cederholm
and
Scarlett
(
1981)
report
that
juvenile
winter
steelhead
leave
their
natal
tributaries
to
overwinter
in
warmer
downstream
reaches.

For
anadromous
salmonids,
such
as
spring
and
fall
chinook
salmon
and
steelhead,
there
is
considerable
variation
in
juvenile
freshwater
life
history
patterns.
The
temperature
requirements
for
larvae
and
rearing
juvenile
trout
and
salmon
are
similar;
however,
the
time
of
freshwater
residence
is
quite
variable.
For
example,
spring
chinook
salmon
rear
for
a
year
in
headwater
streams
before
juveniles
emigrate
during
the
spring
freshet,
whereas
juvenile
fall
chinook
salmon
15
Salmonid
Behavior
and
Water
Temperature
rear
in
mainstem
rivers
and
emigrate
as
subyearlings
during
the
summer
after
several
months
of
freshwater
rearing.
Steelhead
use
headwater
streams
for
rearing
and
emigrate
in
the
spring,
as
do
spring
chinook
salmon,
but
juveniles
may
occupy
headwaters
for
2
or
3
years
before
emigrating.
Therefore,
protective
water
temperature
criteria
must
address
the
distribution
and
juvenile
life
history
pattern
of
each
anadromous
species.

Smolts.
Smoltification
is
a
period
of
profound
developmental
change
in
juvenile
salmonids.
The
physiological
development
that
accompanies
smolt
migration
contributes
to
the
complex
interaction
between
water
temperature
and
emigration
behavior
of
juvenile
salmonids.
By
controlling
biochemical
and
physiological
reaction
rates,
water
temperature
affects
the
physiological
development
of
smolts,
as
well
as
the
timing
and
duration
of
smoltification.
Of
particular
significance
is
the
inhibition
of
the
gill
ATPase
osmoregulatory
enzyme
at
high
water
temperatures,
which
leads
to
a
loss
of
migratory
behavior
in
salmonids
(
see
Physiology
issue
paper).

One
area
that
has
not
been
investigated
is
whether
cold­
water
refuges
have
a
role
in
supporting
emigration
and
physiological
smolt
development
in
salmonid
stocks
that
undergo
long
summer
emigrations.

Adult
potamodromous
migrations.
Potamodromous
migration
patterns
are
important
life
history
variants
for
freshwater
populations
of
native
salmonids.
These
migrations
support
genetic
diversity
in
the
overall
salmonid
populations
and
direct
fish
to
more
spatially,
seasonally,
and
developmentally
suitable
habitat
(
Northcote
1997).
Water
temperature
generally
increases
longitudinally
in
streams
from
upstream
to
downstream
reaches,
and
unfavorably
high
temperatures
in
downstream
reaches
may
create
thermal
barriers
that
limit
or
halt
migrations.
Thermal
barriers
cause
habitat
fragmentation,
disrupting
migration
patterns
and
isolating
smaller
populations
from
the
overall
population.
The
preferred
temperatures
for
nonspawning
adults
during
migration
provide
a
useful
temperature
range
from
which
seasonal
thermal
conditions
in
watersheds
can
be
evaluated
for
migratory
functionality.
However,
extreme
water
temperatures
may
pose
a
more
serious
migratory
barrier
than
water
temperatures
ranging
a
few
degrees
above
the
cited
preferred
migratory
temperature
range
of
a
species.

Spawning
migrations.
Water
temperature
is
a
critical
environmental
factor
during
the
spawning
migrations
of
salmonids
because
the
fish
fast
during
the
migrations
and
must
rely
on
stored
energy
reserves
to
complete
the
journey
(
Berman
and
Quinn
1991,
Coutant
1999).
Although
salmonid
spawning
migrations
occur
throughout
the
year,
high
water
temperatures
are
most
likely
to
delay
or
be
stressful
to
fish
during
summer
and
fall
migrations
(
Table
3).
In
addition,
salmonid
stocks
that
make
long­
distance
migrations
to
inland
spawning
grounds
during
the
summer
and
fall
may
be
more
vulnerable
to
increased
water
temperatures
and
loss
of
cold­
water
refuges.
Increased
water
temperatures
are
reported
to
create
migrational
blockages
for
several
species
of
salmonids
when
water
temperatures
exceed
69.8
°
F
(
21
°
C)
(
Beschta
et
al.
1987,
Major
and
Mighell
1967,
cited
in
ODEQ
1995).
For
bull
trout,
water
temperatures
>
55.4
°
(
13
°
C)
reportedly
block
migratory
behavior
(
ODEQ
1995,
Independent
Scientific
Group
1996,
Spence
et
al.
1996).
Higher
water
temperatures
during
spawning
migrations
also
increase
the
harmful
16
Salmonid
Behavior
and
Water
Temperature
Table
3.
Seasonal
spawning
migration
timing
of
Pacific
Northwest
salmonids
Species
Spawning
migration
timing
Citations
Steelhead
(
O.
mykiss)
Winter
stocks:
November­
April
Summer
stocks:
May­
October
Wydoski
and
Whitney
1979;
Spence
et
al.
1996;
Hicks
1999
Spring
chinook
salmon
(
O.
tshawytscha)
May/
June
Wydoski
and
Whitney
1979;
Berman
and
Quinn
1991;
Nehlsen
et
al.
1991;
Spence
et
al.
1996;
NMFS
chinook
status
review
Fall/
summer
chinook
salmon
(
O.
tshawytscha)
Early
fall
Nehlsen
et
al.
1991;
NMFS
chinook
status
review
Coho
salmon
(
O.
kitsutch)
Early
fall
into
November;
early
July
on
Olympic
Peninsula
Wydoski
and
Whitney
1979;
Spence
et
al.
1996;
NMFS
coho
status
review
Pink
salmon
(
O.
gorbuska)
Late
summer
to
early
fall,
every
other
year
Wydoski
and
Whitney
1979;
Spence
et
al.
1996;
Nehlsen
et
al.
1991
Chum
salmon
(
O.
keta)
Fall
and
winter;
summer
in
Olympic
Peninsula
Wydoski
and
Whitney
1979;
Spence
et
al.
1996
Sockeye
salmon
(
O.
nerka)
Spring
through
fall
Wydoski
and
Whitney
1979;
Quinn
and
Adams
1996
Anadromous
coastal
cutthroat
trout
(
O.
clarkii)
July
through
fall
Wydoski
and
Whitney
1979;
Spence
et
al.
1996;
Hicks
1999;
Trotter
1989;
NMFS
1998
Potamodromous
coastal
cutthroat
trout
(
O.
clarkii)
Very
late
winter
to
early
spring
Trotter
1989
Westslope
cutthroat
trout
(
O.
clarkii)
Very
late
winter
to
early
spring
Trotter
1989
Rainbow/
redband
trout
(
O.
mykiss)
Spring
Wydoski
and
Whitney
1979;
Reiser
and
Bjornn
1979
Bull
trout
(
S.
confluentus)
Late
summer
through
fall
Wydoski
and
Whitney
1979;
Baxter
and
Hauer
2000
Mountain
whitefish
(
P.
williamsoni)
Fall
Wydoski
and
Whitney
1979;
Spence
et
al.
1996
metabolic
effects
on
adult
fish.
Prolonged
exposure
to
elevated
temperatures
during
migration
is
significantly
related
to
prespawning
mortality,
and
increased
metabolic
costs
may
deplete
energy
reserves
before
fish
reach
spawning
grounds,
reducing
the
size
and
number
of
viable
eggs
(
Idler
and
Clemens
1959,
Gilhousen
1980,
Godfrey
et
al.
1954,
Andrew
and
Geen
1960,
CDE
and
IPSFC
1971,
cited
in
ODEQ
1995).

Changes
in
the
annual
thermal
regimes
may
also
result
in
long­
term
behavioral
changes
to
the
timing
of
migratory
patterns.
Quinn
and
Adams
(
1996)
observed
that
Columbia
River
basin
sockeye
salmon
now
migrate
approximately
6
days
earlier
than
historically.
The
migration
of
the
sockeye
salmon
is
cued
by
their
exposure
to
light,
but
the
earlier
migration
timing
is
a
result
of
alterations
to
thermal
and
hydrological
regimes
in
the
river
(
Quinn
and
Adams
1996).

Adult
holding/
refugia.
To
reduce
the
energy
costs
of
oversummering
in
fresh
water
before
spawning,
salmonids
may
select
holding
habitat
based
on
nonthermal
cues,
such
as
groundwater
flow,
which
later
in
the
season
provides
critical
cold­
water
refuge.
This
type
of
behavior
falls
under
predictive
behavioral
thermoregulation.
Examples
of
this
are
seen
in
adult
spring
chinook
salmon,
which
migrate
into
the
tributaries
in
the
spring
and
oversummer
in
fresh
17
Salmonid
Behavior
and
Water
Temperature
water
before
spawning.
Berman
and
Quinn
(
1991)
found
that
adult
spring
chinook
salmon
in
the
Yakima
River
selected
holding
sites
associated
with
islands,
pools,
and
rock
outcrops
in
the
spring,
and
that
these
areas
provided
thermal
refuges
during
the
summer.
A
cooler
holding
habitat
reduces
basal
metabolic
demand
during
the
summer
and
is
critical
to
successful
reproduction.
Torgersen
et
al.
(
1999)
reported
that
adult
spring
chinook
salmon
holding
in
the
Middle
Fork
of
the
John
Day
River
also
select
holding
sites
early
in
the
season
that
provide
coldwater
refuge
during
the
summer.

Spawning.
Salmonid
reproduction
occurs
within
a
variety
of
habitats
ranging
from
streams
and
lakes
to
intertidal
sloughs
(
Groot
and
Margolis
1991,
Spence
et
al.
1996).
The
timing
of
spawning
activity
is
genetically
controlled,
and
many
stocks
have
adapted
to
their
locales,
which
likely
enhances
survival
and
reproductive
success
(
Nehlsen
et
al.
1991,
Sheridan
1962,
Royce
1962,
Burger
et
al.
1985,
Brannon
1987,
NMFS
1998).
Most
stocks
of
Pacific
salmon,
including
summer/
fall
chinook,
fall
coho,
pink,
chum,
and
sockeye
salmon,
have
evolved
to
spawn
in
the
fall
when
stream
flows
are
lowest
and
water
temperatures
decline.
Other
stocks,
such
as
spring
chinook
and
summer
coho,
typically
spawn
during
late
summer
months.
The
trout
indigenous
to
the
Northwest
evolved
to
spawn
in
the
spring
and
are
stimulated
by
rising
water
temperatures
and
high
flows
(
Hicks
1999).
Increased
water
temperatures
on
the
spawning
grounds
can
also
lead
to
the
cessation
of
spawning
activity
(
Spence
et
al.
1996).

Literature
reviews
by
Bjornn
and
Reiser
(
1991)
and
Spence
et
al.
(
1996)
summarize
salmonid
spawning
temperatures
as
ranging
from
33.8
°
F
(
1
°
C)
to
68
°
F
(
20
°
C)
with
most
spawning
occurring
at
temperatures
between
39.2
°
F
(
4
°
C)
and
57.2
°
F
(
14
°
C.)
Table
4
lists
water
temperatures
at
which
spawning
of
different
salmonids
has
been
observed
(
Reiser
and
Bjornn
1979,
ODEQ
1995,
Spence
et
al.
1996).
The
temperature
metrics
are
not
given
with
these
studies
but
are
assumed
to
be
either
instantaneous
or
daily
average
temperatures
(
DAT)
at
the
time
of
spawning.
Spawning
temperatures
likely
reflect
optimal
physiological
temperatures
for
incubation
and
development
of
eggs
rather
than
preference
temperatures
of
spawning
adults.

Despite
the
variations
in
observed
spawning
temperatures,
the
Independent
Scientific
Group
(
1996)
states
that
the
optimal
temperature
for
anadromous
salmonid
spawning
is
50
°
F
(
10
°
C)
and
that
stressful
conditions
for
anadromous
salmonids
begin
at
temperatures
greater
than
60.08
°
F
(
15.6
°
C,)
with
lethal
effects
occurring
at
69.8
°
F
(
21
°
C).

Do
ecological
interactions
influence
the
behavior
of
salmon?
What
about
observations
of
individual
salmonids
using
habitat
that
lab
studies
suggest
is
too
warm?
Don't
these
observations
suggest
that
the
laboratory­
based
data
are
skewed?

The
acute
and
innate
final
preference
temperatures
of
fishes
are
often
superseded
by
their
more
immediate
nonthermal
needs
(
Reynolds
1977,
Reynolds
and
Casterlin
1979).
Frequently,
other
environmental
variables
such
as
food
availability
or
competitive
interactions
provide
the
adaptive
value
of
a
thermal
response
(
Reynolds
1977).
Under
these
circumstances,
water
temperature
may
influence
fish
behavior
by
serving
as
an
orientation
or
direction
cue.
Nonthermal
ecological
factors
such
as
stress,
migrations,
niche
differentiation,
escape
reactions,
photoperiod,
intra­
and
interspecies
interactions,
prey
location,
disease,
and
chemicals
can
affect
18
Salmonid
Behavior
and
Water
Temperature
Table
4.
Selected
water
temperatures
for
spawning
by
Pacific
Northwest
salmonids.
For
the
purpose
of
water
temperature
criteria
protective
of
spawning
salmonids,
these
references
are
assumed
to
be
Daily
Average
Temperatures
(
DAT)

Species
Selected
Spawning
Temperature
Range
°
F
(
°
C)
(
DAT)
Citation
Steelhead
(
O.
mykiss)
50­
55
(
10­
12.8)
Bell
1991
Spring
chinook
salmon
(
O.
tshawytscha)
39.9­
64
(
4.4­
17.8)
Olson
and
Foster
1955,
cited
in
ODEQ
1995
Fall/
summer
chinook
salmon
(
O.
tshawytscha)
41­
56.1
(
5­
13.4)
Raleigh
et
al.
1986,
cited
in
ODEQ
1995
Coho
salmon
(
O.
kitsutch)
50­
55
(
10­
12.8)
Bell
1991
Pink
salmon
(
O.
gorbuska)
46.4­
55.4
(
8­
13)
Independent
Scientific
Group,
1996
Chum
salmon
(
O.
keta)
46.4­
55.4
(
8­
13)
Independent
Scientific
Group,
1996
Sockeye
salmon
(
O.
nerka)
36.1­
46.4
(
2.3­
8)
Brannon
1987
Anadromous
coastal
cutthroat
trout
(
O.
clarkii)
42.9­
62.9
(
6.1­
17.2)
39.9­
48.9
(
4.4­
9.4)
Beschta
et
al.
1987;
Trotter
1989
Potamodromous
coastal
cutthroat
trout
(
O.
clarkii)

41­
42.8
(

5­
6)
Trotter
1989
Westslope
cutthroat
trout
(
O.
clarkii)
44.9­
55.0
(
7.2­
12.8)
Beschta
et
al.
1987;
Trotter
1989
Rainbow/
redband
trout
(
O.
mykiss)
up
to
68
(
20)
50­
55
(
10­
12.8)
Hicks
1999
(
literature
review)
Behnke
1992
Bull
trout
(
S.
confluentus)
peak:
<
44.6
(<
7)
cessation:
>
50
(>
10)
Geotz
1989;
Pratt
1992;
Kraemer
1994;
Fraley
and
Shepard
1989;
James
and
Sexauer
1997;
Wydoski
and
Whitney
1979
Mountain
whitefish
(
P.
williamsoni)
37.4­
41
(
3­
5)
Brown
1952,
1972;
Breder
and
Rosen
1966;
Bruce
and
Starr
1985;
Hildebrand
and
English
1991
the
behavioral
responses
of
fish
to
thermal
stimuli
(
Reynolds
1977).
Several
examples
are
listed
below:

1.
Juvenile
sockeye
salmon
make
daily
vertical
migrations
to
feed
in
warmer
surface
waters,
and
return
to
colder,
deeper
waters
to
lower
metabolic
costs
when
food
is
limited
(
Brett
1971).

2.
Some
bacterial
diseases
alter
the
thermoregulatory
behavior
of
fish
by
increasing
their
preference
temperature
(
Reynolds
et
al.
1976a,
Reynolds
1977c,
Reynolds
and
Covert
1977).
By
increasing
body
temperature
in
response
to
bacterial
invasion,
fish
may
enhance
their
immune
response
to
pathogens
(
Kluger
1978).

3.
A
study
by
Scrivener
et
al.
(
1994)
found
that
juvenile
ocean­
type
fall
chinook
salmon,
rainbow
trout,
and
mountain
whitefish
moved
from
the
Fraser
River
into
a
small
tributary
19
Salmonid
Behavior
and
Water
Temperature
creek
during
the
summer.
The
authors
suggest
that
proximate
cues
of
warmer
water
temperatures
and
clearer
water
attracted
juvenile
salmonids
into
the
tributary,
where
feeding
opportunities
were
enhanced.

4.
Research
by
Fraser
et
al.
(
1993)
found
that
juvenile
Atlantic
salmon
(
Salmo
salar)
switched
between
diurnal
and
nocturnal
foraging
in
response
to
changes
in
water
temperature.
At
warmer
water
temperatures
characteristic
of
spring,
summer,
and
fall
months,
the
salmon
fed
mostly
during
the
daylight
hours.
When
water
temperatures
were
decreased
to
reflect
temperatures
experienced
by
fish
during
winter
months,
nocturnal
feeding
increased
and
daylight
feeding
decreased.
Feeding
probably
decreased
when
water
temperatures
were
colder
because
fish
digested
food
more
slowly
and
because
metabolic
rates
were
lower
at
colder
water
temperatures.
The
authors
concluded
that
the
increase
in
nocturnal
feeding
at
colder
water
temperatures
may
reflect
increased
avoidance
of
light
in
juvenile
salmon
at
low
water
temperatures.
At
colder
water
temperatures,
the
escape
responses
of
fish
are
decreased,
and
increased
avoidance
of
light
may
provide
adaptive
value
through
predator
avoidance.

The
interactions
between
salmonid
thermal
behavior
and
predation
and
competition
are
important
considerations
and
are
discussed
below.
Additional
information
on
multiple
stressors
and
environmental
interactions
can
be
found
in
the
Interactions
issue
paper.

Does
water
temperature
affect
the
predator
avoidance
behavior
of
juvenile
salmonids?

Higher
water
temperatures
may
affect
predation
on
juvenile
salmonids
in
several
ways.
Salmonids
may
be
more
vulnerable
to
predation
when
stressed
by
suboptimal
elevated
water
temperatures.
Mesa
(
1994)
found
that
subyearling
spring
chinook
salmon
acutely
stressed
by
handling
or
agitation
were
lethargic
and
more
vulnerable
to
northern
pikeminnow
(
Ptychocheilus
oregonensis)
predation
than
nonstressed
fish.
However,
a
study
of
subyearling
fall
chinook
salmon
with
acute
high
water
temperatures
did
not
show
increased
predation
vulnerability
to
smallmouth
bass
(
M.
Mesa,
USGS
Biological
Resources
Division,
personal
communication).
If
juvenile
salmonids
lose
equilibrium
due
to
acute
thermal
shock,
their
ability
to
avoid
predators
may
be
significantly
reduced.
Juvenile
rainbow
trout
and
chinook
salmon
were
selectively
preyed
upon
by
larger
fishes
when
thermally
shocked
(
Coutant
1972a,
as
cited
in
Hicks
1999).
The
relative
vulnerability
to
predation
increased
with
duration
of
sublethal
exposure
to
lethal
temperatures
through
incapacitation.
Coutant
(
1972b)
found
that
the
vulnerability
of
juvenile
rainbow
trout
to
predation
depended
on
temperature
and
the
duration
of
exposure
to
high
water
temperatures.

Temperature
stress
may
also
compromise
the
immune
system
of
fish,
making
them
more
susceptible
to
disease
(
Becker
and
Fujihara
1978).
The
physiological
stress
of
elevated
water
temperatures
combined
with
other
stressors
such
as
disease
in
turn
increases
salmonid
susceptibility
to
predation.
When
confronted
by
predatory
fish,
juvenile
salmonids
must
have
the
scope
for
"
burst"
swimming
to
avoid
predators.
However,
when
challenged
by
either
a
low­
to­
moderate
or
a
high
infection
level
of
Renibacterium
salmoninarum
(
the
infective
bacterium
for
bacterial
kidney
disease),
infected
subyearling
spring
chinook
salmon
were
twice
as
likely
as
noninfected
fish
to
be
consumed
by
either
northern
pikeminnow
or
smallmouth
bass
20
Salmonid
Behavior
and
Water
Temperature
(
Mesa
et
al.
1998).
Infection
with
the
disease
apparently
reduced
the
chinooks'
scope
for
activity,
making
the
them
more
vulnerable.
Many
other
physiological
and
environmental
stressors
may
act
in
concert
with
suboptimal
water
temperatures
to
increase
salmonid
susceptibility
to
predation
(
see
Interactions
issue
paper).

Does
water
temperature
affect
the
predatory
fish
that
feed
on
juvenile
salmonids?

Higher
water
temperatures
increase
the
feeding
rate
of
predatory
fish
such
as
the
native
northern
pikeminnow.
This
problem
is
magnified
by
the
widespread
occurrence
of
nonnative
predatory
fish
in
Pacific
Northwest
waters.
Many
of
these
introduced
fishes
function
best
in
cool
waters
that
serve
as
a
transition
between
the
cold
water
optimal
for
salmonids
and
warmer
water
optimal
for
warm­
water
fish.

Hydropower
development
of
northwest
rivers
has
raised
seasonal
water
temperatures
and
the
period
of
warm
water
in
the
fall,
thus
lengthening
the
seasonal
feeding
period
of
predatory
fish.
Impoundment
has
also
changed
the
migratory
behavior
of
juvenile
salmonids
by
concentrating
migrants
in
dam
forebay
and
tailrace
areas,
creating
unusually
abundant
feeding
opportunities
for
predators,
particularly
northern
pikeminnow,
which
feed
heavily
when
prey
is
abundant
(
Poe
et
al.
1991,
Vigg
et
al.
1991,
Petersen
and
DeAngelis
1992).
Impoundments
also
have
slowed
river
flow,
prolonging
migration
time
and
the
length
of
time
migrants
are
exposed
to
predators
(
Poe
et
al.
1991).
In
large
northwest
rivers,
the
most
significant
predator
on
juvenile
salmonids
is
the
northern
pikeminnow,
a
native
cyprinid
species
(
Poe
et
al.
1991,
Mesa
1994).
Competition
for
food
between
the
native
northern
pikeminnow
and
introduced
predators,
such
as
smallmouth
bass
and
walleye,
may
increase
northern
pikeminnow
predation
pressure
on
juvenile
salmonids
(
Li
et
al.
1987,
Poe
et
al.
1994).

During
the
summer
months,
fish
impoundment
reduces
river
flow
and
seasonal
water
temperatures
rise,
providing
optimal
conditions
for
smallmouth
bass
that
use
the
warmer,
quieter
nearshore
areas
where
subyearling
fall
chinook
salmon
rear.
This
habitat
overlap
leads
to
high
predation
by
the
introduced
bass
(
Gray
and
Rondorf
1986,
Poe
et
al.
1991,
Tabor
et
al.
1993,
Giorgi
et
al.
1994,
Poe
et
al.
1994,
Zimmerman
and
Parker
1995,
Petersen
et
al.
2000).
Petersen
et
al.
(
2000)
used
bioenergetics
modeling
to
estimate
loss
of
emigrating
salmonids
to
northern
pikeminnow
and
smallmouth
bass
predation
in
the
lower
Snake
River
under
current
impounded
conditions
and
simulated
unimpounded
conditions.
The
model's
input
temperature
regime
was
manipulated
to
reflect
the
current
impounded
thermal
regime
and
the
predicted
decrease
in
water
temperatures
if
the
four
lower
Snake
River
dams
were
removed
(
unimpounded)
while
holding
all
other
model
parameters
and
inputs
(
diet,
population
size,
age
structure)
constant.
Under
these
temperature
simulations,
Petersen
et
al.
(
2000)
estimated
a
7%
decrease
in
predation
loss
of
salmonids
to
smallmouth
bass,
and
about
a
9%
decrease
in
loss
to
northern
pikeminnow
under
the
cooler,
unimpounded
thermal
conditions
simulated
for
the
lower
Snake
River.

Warmer
water
temperatures
also
increase
the
abundance
of
predators
that
feed
on
juvenile
salmonids.
Maule
and
Horton
(
1985)
studied
growth
and
fecundity
of
walleye
in
the
John
Day
Reservoir
below
McNary
Dam
on
the
Columbia
River
and
found
that
the
reservoir
habitat
provided
low
flow
conditions
and
nearly
ideal
water
temperatures
for
walleye
growth.
Water
temperatures
in
the
reservoir
remained
at
or
near
the
thermal
optimum
for
walleye
food
21
Salmonid
Behavior
and
Water
Temperature
consumption
(
71.6
°
F
[
22
°
C])
during
the
growing
season,
but
did
not
increase
to
the
maximum
(
80.6
°
F
[
27
°
C])
(
Kitchell
et
al.
1977b,
Maule
and
Horton
1985).
Maule
and
Horton
(
1985)
also
reported
walleye
from
the
John
Day
Reservoir
growing
at
close
to
the
highest
rate
reported
for
the
species.

What
is
competition
and
how
does
water
temperature
influence
it?

Salmonids,
like
other
animals
and
plants,
compete
with
members
of
their
own
species
(
intraspecific
competition)
and
with
other
species
(
interspecific
competition)
for
limited
resources.
In
natural
environments,
resources
such
as
food
and
habitat
often
are
limited.
Water
temperature
is
an
aspect
of
habitat
that
can
favor
or
exclude
one
fish
species
over
another,
influencing
distribution.

Ecologists
generally
recognize
two
forms
of
competition:
exploitative
and
interference.
Exploitative
competition
occurs
when
individuals
compete
for
access
to
a
limited
resource,
which
one
species
depletes
so
that
it
cannot
be
used
by
other
species
(
Begon
and
Mortimer
1986).
Interference
competition
occurs
when
individuals
compete
with
each
other
for
a
limited
resource.
A
common
example
in
salmonids
is
territoriality
(
Grant
et
al.
1998).
Salmonids
often
hold
feeding
territories
and
monopolize
access
to
resources
within
the
defended
territory.

Temperature
regime
is
key
to
the
outcome
of
competitive
interactions
within
a
fish
community.
Fish
competing
within
their
optimum
temperature
range
have
an
improved
capability
of
performing
compared
with
species
operating
outside
their
optimum
temperature
range.
The
ability
of
salmonids
to
compete
for
short­
and
long­
term
survival
at
the
upper
end
of
their
thermal
tolerance
range
involves
multiple
factors,
including
swimming
performance;
fecundity
under
a
warm
thermal
regime;
defending
feeding
stations;
consuming
food
even
in
the
absence
of
competition;
sustaining
maintenance
requirements
and
growing;
finding
cold­
water
refuges
and
escape
cover;
avoiding
cumulative
mortification
(
Kilgour
and
McCauley
1986,
as
cited
in
McCullough
1999);
and
resisting
disease,
as
well
as
avoiding
direct
short­
term
thermal
death.
Temperature
regime
operates
directly
on
community
composition
through
a
species'
thermal
tolerance
and
preference.
When
thermal
regimes
exceed
the
optimum
for
salmonids,
their
suitable
habitat
area
shrinks
and
warm­
water
tolerant
species
may
fill
these
niches
(
McCullough
1999).

Does
water
temperature
affect
competition
between
nonnative
salmonids,
such
as
brook
trout,
and
native
salmonids?

Nonnative
brook
trout
(
S.
fontinalis)
have
extensively
colonized
the
inland
western
United
States
(
Adams
1999)
and
may
pose
a
serious
threat
to
native
salmonids,
particularly
cutthroat
trout.
Because
brook
trout
do
not
hybridize
with
cutthroat
trout,
they
are
believed
to
affect
the
latter
primarily
through
predation,
disease
transmission,
or
competition.
Generally,
competition
is
cited
as
the
most
important
factor
(
Young
1995).

Temperature
can
have
a
dramatic
effect
on
the
coexistence
of
cutthroat
and
brook
trout.
DeStaso
and
Rahel
(
1994)
studied
interactions
between
brook
and
Colorado
cutthroat
trout
(
O.
c.
pleuriticus)
in
experimental
stream
tanks
at
different
water
temperatures.
At
temperatures
of
22
Salmonid
Behavior
and
Water
Temperature
50
°
F
(
10
°
C,)
brook
and
cutthroat
trout
were
nearly
equal
competitors,
but
at
68
°
F
(
20
°
C)
brook
trout
were
dominant.
Schroeter
(
1998)
studied
competitive
interactions
between
brook
and
Lahontan
cutthroat
trout
in
experimental
field
tanks
with
a
natural
water
supply
(~
59
°
F
[
15
°
C])
and
found
brook
and
cutthroat
trout
to
be
equal
competitors,
unless
density
of
the
former
was
high
(
2
brook:
1
cutthroat
trout).
Adams
(
1999)
suggested
that
upstream
limits
to
the
distribution
of
brook
trout
could
result
from
a
growth
disadvantage
in
higher
elevation
streams
with
shorter
growing
seasons.

Water
temperature
also
influenced
behavioral
dominance
and
growth
in
a
study
of
competition
between
brook
trout
and
bull
trout.
McMahon
et
al.
(
1999)
measured
growth
of
subyearling
bull
trout
and
brook
trout
in
sympatry
(
both
species
together)
and
allopatry
(
each
species
tested
separately)
at
four
temperatures
(
46.4
°
F,
[
8
°
C],
53.6
°
F,
[
12
°
C],
60.8
°
F,
[
16
°
C],
and
68
°
F
[
20
°
C]).
In
allopatry,
bull
trout
and
brook
trout
growth
was
similar
at
lower
temperature
(
46.4
°
F
[
8
°
C]
and
53.6
°
F
[
12
°
C]),
but
brook
trout
grew
significantly
faster
than
bull
trout
at
higher
water
temperatures
(
60.8
°
F
[
16
°
C]
and
68
°
F
[
20
°
C])(
see
Physiology
issue
paper).
The
presence
of
brook
trout
had
a
significant
negative
effect
on
the
growth
of
bull
trout.
Bull
trout
in
sympatry
with
brook
trout
averaged
25%
lower
growth
than
in
allopatry
at
all
temperatures.
In
contrast,
the
presence
of
bull
trout
had
a
significant
positive
effect
on
brook
trout
growth,
especially
at
temperatures
(>
53.6
°
F
[
12
°
C]),
where
brook
trout
growth
in
sympatry
averaged
40%
higher
than
in
allopatry.
The
results
of
this
study
suggest
that
increases
in
water
temperature
tend
to
favor
brook
trout
because
of
their
higher
temperature
tolerance
and
preference
range
as
well
as
their
behavioral
dominance
(
Nakano
et
al.
1998)
when
reared
with
bull
trout.
This
competitive
advantage
would
be
most
pronounce
at
water
temperatures
(>
53.6
°
F
[
12
°
C]).
In
habitats
where
nonnative
brook
trout
are
present,
cooler
temperature
criteria
may
be
appropriate
to
protect
native
cutthroat
trout
and
bull
trout.

Does
water
temperature
influence
intraspecific
competition
between
native
salmonids?

The
response
of
salmonids
to
temperature
may
depend
on
developmental
stage,
age,
or
body
size.
The
effect
of
size
on
thermal
response
is
poorly
understood
(
Elliott
1981),
but
there
is
some
evidence.
For
example,
Meeuwig
(
2000)
found
the
growth
response
of
cutthroat
trout
to
vary
as
a
function
of
body
size
(
range
of
mean
body
lengths
among
treatment
groups
=
29.5­
121
mm).
Larger
cutthroat
trout
grew
less
at
higher
chronic
temperatures
(
range
of
exposure
=
53.6
°
F­
75.2
°
F
[
12
°
C­
24
°
C]).
Potential
competitive
interactions
within
or
among
cohorts
may
therefore
be
affected
by
temperature.
The
exact
nature
of
potential
growth
responses
and
implications
for
intraspecific
competition
has
yet
to
be
clearly
defined
in
the
literature,
however.

The
effect
of
temperature
on
the
size
and
age
of
migrating
fish
may
also
affect
intraspecific
competition.
For
example,
the
effect
of
temperature
on
the
age,
size,
and
timing
of
emigration
by
Pacific
salmon
(
e.
g.,
Holtby
1988,
Holtby
et
al.
1989)
may
affect
the
dynamics
of
competitive
interactions
among
juveniles.
A
field
study
by
Haas
(
unpublished
manuscript)
investigated
the
effect
of
small
increases
in
water
temperature
on
the
competitive
dominance
of
bull
trout
and
rainbow
trout
in
streams.
This
study
found
that
bull
trout
density
showed
a
decreasing
trend
whereas
rainbow
trout
density
showed
an
increasing
trend
with
rising
maximum
stream
temperatures
above
55.4
°
F
(
13
°
C).
23
Salmonid
Behavior
and
Water
Temperature
Another
study
by
Northcote
(
1997)
described
a
long­
term
program
of
research
to
understand
competition
between
coastal
cutthroat
trout
and
Dolly
varden
char
in
lakes
of
British
Columbia.
One
finding
suggests
that
lower
water
temperatures
in
winter
as
well
as
summer
influence
the
pattern
of
competitive
interactions
between
native
salmonids.
In
natural
habitats,
Northcote
(
1997)
found
that
cutthroat
trout
used
primarily
epilimnetic
habitats
(
shallower
waters)
while
char
used
hypolimnetic
(
deeper)
habitats.
In
lakes
with
experimentally
introduced
sympatric
populations
of
trout
and
char,
the
same
pattern
was
found.
When
only
char
were
introduced
into
lakes,
the
fish
showed
a
pronounced
shift
toward
shallower
water.
Trout
did
not
show
a
change
in
habitat
use
in
the
absence
of
char.
This
suggested
that
coastal
cutthroat
trout
might
exclude
Dolly
varden
char
from
shallow
habitats
in
lakes.
Interestingly,
the
pattern
of
segregation
was
not
observed
in
winter,
when
char
frequently
used
shallow
habitats.
The
seasonal
pattern
of
segregation
may
reflect
an
influence
of
temperature.
Temperatures
are
lower
in
winter,
and
char
are
known
to
have
lower
thermal
optima
than
trout
(
e.
g.,
McMahon
et
al.
1999).
Alternatively,
temperature
may
be
indirectly
affecting
the
distribution
of
char
through
an
influence
on
preferred
prey
or
another
key
resource.
The
specific
influence
of
temperature
has
yet
to
be
clearly
demonstrated
in
this
system,
but
it
is
clear
that
changes
to
thermal
regimes
may
influence
interspecific
interactions.

Does
water
temperature
influence
interspecific
competition
between
salmonids
and
other
fishes?

In
many
streams
of
the
Pacific
Northwest,
salmonids
dominate
in
headwater
fish
assemblages
but
are
replaced
by
other
species
in
downstream
areas.
In
particular,
cyprinids
tend
to
occupy
similar
habitats
(
e.
g.,
midwater
feeding)
in
warmer
downstream
habitats
(
see
predation
section
above).
This
longitudinal
variation
in
streams
may
be
manifested
as
vertical
stratification
in
lakes
(
e.
g.,
salmonids
in
colder
hypolimnion).
Reeves
et
al.
(
1987)
found
water
temperature
influenced
interactions
between
redside
shiner
(
Cyprinidae:
Richardsonius
balteatus)
and
juvenile
steelhead
trout.
In
warmer
(
66.2
°
F
­
71.6
°
F
[
19
°
C­
22
°
C])
water,
redside
shiners
appeared
to
affect
the
growth
of
steelhead
trout,
and
they
used
a
wider
variety
of
habitats
in
the
presence
of
trout.
Hillman
(
1991)
found
that
water
temperature
influenced
the
interactions
between
redside
shiner
and
juvenile
chinook
salmon.
Shiners
affected
the
distribution
of
juvenile
chinook
salmon
in
the
laboratory
when
temperatures
were
warmer
(
66.2
°
F
[
18
°
C]­
69.8
°
F
[
21
°
C])
but
not
at
cold
temperatures
(
53.6
°
F
[
12
°
C]­
59
°
F
[
15
°
C]).
Taniguchi
et
al.
(
1998)
similarly
studied
competition
between
trout
(
brook
trout
and
brown
trout,
Salmo
trutta)
and
creek
chub
(
Cyprinidae:
Semotilus
atromaculatus)
and
found
the
latter
to
be
competitively
dominant
at
higher
(>
68
°
F
[
20
°
C])
water
temperatures.
This
pattern
extended
to
longitudinal
zonation
of
fish
within
streams.
Less
is
known
of
the
influence
of
temperature
on
behavioral
interactions
between
nonnative,
nonsalmonid
fishes
(
e.
g.,
many
species
of
centrarchid
fishes
introduced
for
sport
fisheries)
and
native
salmonids.
Because
many
of
the
introduced
nonsalmonid
fish
are
warm­
water
species,
the
capability
of
salmonids
to
compete
or
avoid
predation
should
be
reduced
considerably
as
temperatures
increase
(
see
predation
section
above).

What
is
the
role
of
cold­
water
refugia
in
salmonid
habitat?

Cold­
water
refugia
protect
salmonids
from
extreme
water
temperatures
and
also
permit
them
to
behaviorally
thermoregulate
to
conserve
energy
when
water
temperatures
are
suboptimal.
24
Salmonid
Behavior
and
Water
Temperature
In
stream
reaches
that
have
warmed
above
levels
optimal
for
salmonids,
fish
persist
by
using
cold­
water
refugia
(
Berman
and
Quinn
1991,
Li
et
al.
1994,
Neilson
et
al.
1994,
McIntosh
et
al.
1995a,
Torgersen
et
al.
1999,
King
1937,
Mantelman
1958,
Gibson
1966,
as
cited
in
McCullough
1999).
Extreme
water
temperatures
are
physiologically
stressful
to
salmonids
and
can
result
in
direct
and
indirect
mortality
of
fish.
Salmon
behaviorally
respond
to
stressfully
high
water
temperatures
by
seeking
cooler
water.
Suboptimal
water
temperatures
may
result
in
upstream
migrations,
or
salmonids
may
explore
local
habitat
for
cold­
water
refugia.
A
study
of
steelhead
in
northern
California
streams
found
that
age­
1
steelhead
moving
into
thermally
stratified
pools
with
cold
groundwater
input
when
temperatures
in
streams
increased
to
73.4
°
F
(
23
°
C)
during
the
warmest
part
of
the
day
(
Nielsen
et
al.
1994).
Snucins
and
Gunn
(
1995)
reported
a
similar
example
of
reactive
behavioral
thermoregulation
by
lake
trout
(
Salvelinus
namaycush).
When
water
temperatures
peaked
during
the
summer
in
a
warm
isothermal
lake,
large
lake
trout
began
utilizing
a
cold­
water
seep.
This
behavior
was
unusual
because
the
seep
was
located
on
the
shoreline
of
the
lake
in
shallow
water,
and
lake
trout
prefer
deep
water.

During
summer
months,
cold­
water
refugia
likely
contract
streamflow
and
maximum
stream
temperatures.
As
cold­
water
refugia
contract,
competition
between
salmonids
for
this
thermal
resource
may
intensify,
creating
additional
stress.
Neilsen
et
al.
(
1994)
found
that
age­
0
and
age­
1
juvenile
steelhead
were
less
likely
to
use
the
cold­
water
refugia
than
older
juveniles
when
oxygen
levels
were
low.
Low
oxygen
levels
may
have
incurred
high
costs
among
younger
steelhead,
overshadowing
the
benefit
of
thermoregulatory
behavior.
This
study
also
reports
that
fish
using
refugia
were
distinctly
quiescent.
A
study
of
lake
trout
thermoregulatory
behavior
by
Snucins
and
Gunn
(
1995)
found
that
only
the
largest
lake
trout
used
the
spatially
limited
refugia,
raising
the
possibility
that
intraspecific
competitive
exclusion
was
limiting
use
of
the
refugia.
Degradation
or
elimination
of
cold­
water
microhabitat
from
human
activities
may
put
some
salmonid
stocks
at
risk,
because
the
fish
can
become
marooned
in
pools
or
stream
sections
where
the
rising
water
temperatures
result
in
either
direct
or
indirect
mortality.

How
do
salmonids
use
cold­
water
refugia?

Because
salmonids,
like
most
fish,
take
on
the
temperature
of
their
surrounding
environment,
they
control
their
body
temperature
behaviorally
rather
than
physiologically.
Behavioral
thermoregulation
requires
a
range
of
water
temperatures
from
which
fish
can
select
those
most
appropriate
to
their
immediate
ecological
and
physiological
needs.
Research
by
Torgersen
et
al.
(
1999)
and
Berman
and
Quinn
(
1991)
suggests
that
cold­
water
microhabitat
is
important
to
spring
chinook
salmon
that
oversummer
in
freshwater
prior
to
spawning.
The
cold
water
protects
the
chinook
from
extreme
summer
water
temperatures
and
reduces
metabolic
costs
in
freshwater
prior
to
spawning,
thereby
improving
spawner
fitness.
Brett's
(
1971)
research
on
subyearling
sockeye
salmon
in
Babine
Lake
strongly
suggests
that
juvenile
sockeye
used
the
vertical
thermal
variability
of
the
lake
to
conserve
energy
for
optimal
growth.

Cold­
water
refugia
may
be
particularly
useful
to
salmonid
populations
that
(
1)
reside
at
the
southern
end
of
their
range,
(
2)
inhabit
marginally
suitable
habitat,
and
(
3)
undertake
extensive
migrations
in
the
inland
northwest.
Research
further
suggests
that
the
long­
term
persistence
of
some
native
salmonid
populations
in
the
Pacific
Northwest
may
depend
on
the
availability
of
cold­
water
refugia,
especially
during
hot
and
dry
climatic
cycles.
25
Salmonid
Behavior
and
Water
Temperature
Water
temperatures
affect
the
spatial
distribution
of
salmonids
along
the
stream
course
(
Roper
et
al.
1994,
Theurer
et
al.
1985),
and,
at
finer
spatial
scales,
salmonids
use
thermal
refugia
to
avoid
stressful
temperatures
(
Gibson
1966,
Kaya
et
al.
1977,
Berman
and
Quinn
1991,
Ebersol
et
al.
2000).
Habitat
and
thermal
diversity
are
especially
high
in
alluvial
floodplain
river
segments
(
Brown
1997,
Cavallo
1997,
Frissell
et
al.
1996),
in
part
because
in
this
geomorphic
setting,
hyporheic
groundwater
helps
to
create
thermal
refugia
(
Poole
and
Berman
in
press).
Dams,
however,
often
are
built
at
constrictions
in
rivers
just
below
large
alluvial
plains
to
maximize
their
reservoir
storage
capacity
yet
minimize
their
physical
size.
Dams
therefore
tend
to
inundate
alluvial
river
segments
(
National
Research
Council
1996)
where
hyporheic
buffering
is
prevalent
(
Coutant
1999,
Poole
and
Berman
in
press),
eliminating
the
cold­
water
refugia
in
these
reaches.
Other
human
land
use
activities
such
as
logging,
grazing,
and
farming
can
also
reduce
the
abundance
of
thermal
refugia
in
stream
reaches
(
see
Spatio­
Temporal
issue
paper).
Therefore,
whether
through
inundation
of
alluvial
river
segments
behind
dams
or
simplification
of
in­
stream
habitat
from
land
use
activities,
human
activities
have
reduced
the
availability
of
thermal
refugia
within
Pacific
Northwest
stream
reaches.
This
loss
of
thermal
refugia
may
create
higher
levels
of
thermal
stress
during
the
warmest
months
of
the
year
(
Ebersol
et
al.
2000)
or
during
migration
through
warm
river
segments.

Conclusion
The
family
Salmonidae
is
a
group
of
cold­
water­
adapted
fish.
Three
genera
of
salmonid
predominate
in
the
Pacific
Northwest:
(
1)
Salvelinus
spp.­(
char),
(
2)
Oncorhynchus
spp.­(
trout
and
salmon),
and
(
3)
Prosopium
spp.­(
whitefish).
Native
salmonids
have
dominated
the
freshwaters
of
the
Pacific
Northwest
because
historically
water
temperatures
supported
their
ecological
and
physiological
requirements.
To
protect
and
restore
native
Pacific
Northwest
salmonids
will
require
protecting
and
restoring
the
natural
thermal
characteristics
of
their
environment.

Human
activities
have
altered
the
thermal
characteristics
of
rivers
and
streams
in
the
Pacific
Northwest.
Logging,
farming,
and
hydropower
development
have
(
1)
changed
the
natural
annual
thermograph
of
rivers
and
steams,
disrupting
adaptive
life
history
strategies
of
salmonid
populations;
(
2)
increased
summer
maximum
temperatures,
which
may
interfere
with
migrations
and
result
in
feeding
cessation,
thermal
stress,
increased
predation
pressure,
and
competitive
interaction
that
alter
the
distribution
and
abundance
of
native
salmonids;
and
(
3)
reduced
or
eliminated
cold­
water
refugia,
which
is
an
important
source
of
thermal
heterogeneity
in
aquatic
systems,
providing
protection
from
thermally
stressful
maximum
water
temperatures
and
crucial
habitat
diversity
for
behavioral
thermoregulation.
From
a
behavioral
perspective,
the
following
considerations
are
important
in
developing
water
temperature
criteria
protective
of
native
Pacific
Northwest
salmonids:

1.
Anadromous
Pacific
salmon
and
steelhead
display
local
adaptation
to
predictable
annual
thermal
cycles.

2.
The
distribution
and
behavioral
aspects
of
juvenile
life
history
patterns
such
as
rearing
characteristics,
length
of
freshwater
rearing,
and
emigration
timing
of
each
anadromous
species
are
affected
by
water
temperature.
26
Salmonid
Behavior
and
Water
Temperature
3.
Migratory
behavior
of
juvenile
anadromous
salmonids
is
influenced
by
water
temperature.
Gill
ATPase,
an
enzyme
that
is
crucial
for
seawater
osmoregulation,
is
sensitive
to
elevated
water
temperatures.
Decreasing
gill
ATPase
activity
is
associated
with
loss
of
migratory
behavior
in
anadromous
juvenile
salmonids.
For
successful
smoltification
in
anadromous
salmonids,
research
suggests
spring
water
temperatures
must
not
exceed
53.6
°
F
(
12
°
C)
(
Zaugg
and
Wagner
1973).
Summer
water
temperatures
for
subyearling
fall
chinook
salmon
emigration
suggest
that
fall
emigrants
may
be
more
successful
at
higher
water
temperatures
than
spring
emigrants.

4.
Native
char
populations
are
the
most
stenothermic
salmonids
found
in
Pacific
Northwest
freshwaters.
Char
prefer
water
temperatures
near
44.6
°
F
+
9
°
F
(
7
°
C
+
5
°
C)
(
Reiser
and
Bjornn
1979,
Bonneau
and
Scarnecchia
1996,
Spence
et
al.
1996).

5.
Water
temperatures
of
(>
73.4
°
F
[
23
°
C])
for
even
short
periods
of
time
(
hours)
result
in
movement
into
cold
water
refugia
by
Pacific
salmon
and
trout
(
Neilsen
et
al.
1991).
Colder
water
temperatures
are
required
for
adult
migration.

6.
Mean
daily
water
temperatures
(>
69.8
°
F
[
21
°
C])
decrease
or
eliminate
feeding
behavior
by
Pacific
salmon
and
trout
(
Hokansen
et
al.
1977).

7.
Larvae
and
juvenile
salmonids
require
a
variety
of
water
temperatures
for
behavioral
thermoregulation
to
optimize
physiological
functioning.
A
certain
amount
of
thermal
diversity
is
important
and
commonly
available
in
undisturbed
naturally
occurring
rearing
habitat.
Water
temperature
criteria
can
play
a
central
role
in
the
protection
and
rehabilitation
of
rearing
habitat
by
protecting
and
promoting
restoration
of
cold­
water
refugia,
and
by
setting
numeric
criteria
for
water
temperature
based
on
the
optimal
temperatures
that
drive
behavioral
thermoregulation.

8.
Potamodromous
salmonids
display
a
wide
array
of
freshwater
migratory
strategies
that
support
different
life
history
stages
and
facilitate
genetic
exchange
between
isolated
populations,
thus
forming
a
metapopulation.
Fluvial
 
afluvial
migration
(
from
streams
to
rivers)
is
one
migratory
pattern
seen
in
bull
trout.
Cold­
water
refugia
contributes
to
habitat
connectivity
and
may
help
support
bull
trout
migrations.

9.
Higher
seasonal
water
temperatures
and
longer
periods
of
warm
water
in
aquatic
systems
increase
the
feeding
rate
of
predatory
fish
species
that
prey
on
juvenile
salmonids.

10.
The
preference
temperatures
of
juvenile
char,
trout,
and
salmon
suggest
that
interspecific
competition
plays
a
role
in
the
distribution
and
phylogenetically
derived
thermal
preferences
of
these
fish.

11.
Water
temperature
may
play
a
crucial
role
in
determining
whether
a
native
salmonid
is
displaced
by
an
introduced
salmonid.
Native
salmonids
may
be
better
able
to
compete
at
colder
water
temperatures
with
introduced
salmonids
such
as
the
brook
trout.
27
Salmonid
Behavior
and
Water
Temperature
12.
Many
of
the
introduced
fishes
in
the
Pacific
Northwest
are
cool­
and
warm­
water
fish,
such
as
smallmouth
bass
and
walleye,
that
do
well
in
the
impounded
reservoirs
characterized
by
reduced
water
flow,
moderate
winter
temperatures,
and
warmer
water
temperatures
during
the
summer
and
fall.
These
characteristics
do
not
favor
salmonid
species.
Native
fish
species,
including
salmonids,
are
no
longer
the
dominant
species
in
many
high­
order
reaches
of
the
lower
Columbia
River
basin
(
Li
et
al.
1987).
Increased
water
temperatures
in
reservoirs
are
an
important
determinant
in
this
succession,
although
lack
of
reservoir
flow
and
the
resulting
loss
of
the
riverine
ecosystem
also
contribute
significantly
to
the
problem.

13.
Existing
cold­
water
refugia
may
be
important
to
salmonids
migrating
through
main­
stem
rivers
and
large
tributaries.
Cold­
water
refugia
are
also
important
to
spring
migrants,
such
as
chinook
salmon,
because
refugia
provide
cold­
water
holding
habitat
over
the
warmest
part
of
the
summer
prior
to
spawning.

14.
Loss
of
thermal
refugia
from
inundation
of
alluvial
river
segments
behind
dams
may
have
important
implications
for
migrating
juvenile
and
adult
salmonids,
resulting
in
potentially
higher
levels
of
thermal
stress
during
the
warmest
months
of
the
year
(
Ebersol
et
al.
2000)
or
during
migration
through
warm
river
segments.

Literature
Cited
Adams
SB.
1999.
Peer
review
of
bull
trout
temperature
criteria.
Report
for
U.
S.
Environmental
Protection
Agency,
Seattle,
WA.

Adkison
MD.
1995.
Populations
differentiation
in
Pacific
salmon:
local
adaptation,
genetic
drift,
or
the
environment?
Can
J
Fish
Aquat
Sci
52:
2762­
2777.

Andrew
FJ,
Geen
GH.
1960.
Sockeye
and
pink
salmon
production
in
relation
to
proposed
dams
in
the
Fraser
River
system.
Int
Pacif
Salmon
Fish
Comm
Bull
XI.
259
pp.

Baxter
CV,
Hauer
FR.
2000.
Geomorphology,
interaction
of
hyporheic
exchange,
and
selection
of
spawning
habitat
by
bull
trout
(
Salvelinus
confluentus):
A
multi­
scale,
hierarchical
approach.
Can
J
Fish
Aquat
Sci
57:
1470­
1481.

Becker
CD,
Fujihara
MP.
1978.
The
bacterial
pathogen
Flexibacter
columnaris
and
its
epizootiology
among
Columbia
River
fish.
A
review
and
synthesis.
Am
Fish
Soc
Monogr
2:
92
pp.

Begon
M,
Mortimer
M.
1986.
Population
ecology:
A
unified
study
of
animals
and
plants.
London:
Blackwell
Scientific
Publications.

Behnke
RJ.
1992.
Native
trout
of
western
North
America.
Monograph
6.
American
Fisheries
Society,
Bethesda,
MD.

Beitinger
TL,
Fitzpatrick
LC.
1979.
Physiological
and
ecological
correlates
of
preferred
temperature
in
fish.
Am
Zool
19:
319­
329.

Bell
MC.
1991.
Fisheries
handbook
of
engineering
requirements
and
biological
criteria.
U.
S.
Army
Corps
of
Engineers.
Fish
Passage
Development
and
Evaluation
Program,
North
Pacific
Division,
Portland,
OR.

Berman
CH,
Quinn
TP.
1991.
Behavioral
thermoregulation
and
homing
by
spring
chinook
salmon,
Oncorhynchus
tshawytscha
(
Walbaum),
in
the
Yakima
River.
J
Fish
Biol
39:
301­
312.
28
Salmonid
Behavior
and
Water
Temperature
Beschta
RL,
Bilby
RE,
Brown
GW,
Holtby
LB,
Hofstra
TD.
1987.
Stream
temperature
and
aquatic
habitat:
Fisheries
and
forestry
interactions.
In:
Salo
EO,
Cundy
TW,
eds.
Streamside
management:
forestry
and
fishery
interactions.
College
of
Forest
Resources,
University
of
Washington,
Seattle.
Contribution
No.
57.
Proceedings
of
a
Symposium
held
at
University
of
Washington,
February
12­
14,
1986,
pp.
191­
231.

Bjornn
TC.
1971.
Trout
and
salmon
movements
in
two
Idaho
streams
as
related
to
temperature,
food,
stream
flow,
cover,
and
population
density.
Trans
Am
Fish
Soc
100:
423­
438.

Bjornn
TC,
Reiser
DW.
1991.
Habitat
requirements
of
anadromous
salmonids.
Influence
of
forest
and
rangeland
management
on
salmonid
fishes
and
their
habitats.
Am
Fish
Soc
Special
Publ
19:
83­
138.

Bonneau
JL,
Scarnecchia
DL.
1996.
Distribution
of
juvenile
bull
trout
in
a
thermal
gradient
of
a
plunge
pool
in
Granite
Creek,
Idaho.
Trans
Am
Fish
Soc
125:
628­
630.

Brannon
EL.
1987.
Mechanisms
stabilizing
salmonid
fry
emergence
timing.
In:
Smith
HD,
Margolis
L,
Wood
CC,
eds.
Sockeye
salmon
(
Oncorhynchus
nerka)
population
biology
and
future
management.
Can
Spec
Publ
Fish
Aquat
Sci
96:
120­
124.

Breder
CM,
Rosen
DE.
1966.
Modes
of
reproduction
in
fishes.
Garden
City,
NY:
Natural
History
Press.

Brett
JR.
1971.
Energetic
responses
of
salmon
to
temperature.
A
study
of
some
thermal
relations
in
the
physiology
and
freshwater
ecology
of
sockeye
salmon
(
Oncorhynchus
nerka).
Am
Zool
11(
1):
99­
113.

Brett
JR.
1995.
Energetics.
In:
Groot
C,
Margolis
L,
Clarke
WC,
eds.
Physiological
ecology
of
Pacific
salmon.
Vancouver:
UBC
Press,
pp.
1­
68.

Brett
JR.
1952.
Temperature
tolerance
in
young
Pacific
salmon,
genus
Oncorhynchus.
J
Fish
Res
Bd
Can
9(
6):
265­
323.

Brett
JR,
Higgs
DA.
1970.
Effect
of
temperature
on
the
rate
of
gastric
digestion
in
fingerling
sockeye
salmon,
Oncorhynchus
nerka.
J
Fish
Res
Bd
Can
27:
1767­
1779.

Brown
CJP.
1952.
Spawning
habit
and
early
development
of
the
mountain
whitefish,
Prosopium
williamsoni,
in
Montana.
Copeia
1952:
109­
113.

Brown
AG.
1997.
Biogeomorphology
and
diversity
in
multiple­
channel
river
systems.
Global
Ecol
Biogeogr
Lett
6:
179­
185.

Brown
LG.
1972.
Early
life
history
of
the
mountain
whitefish,
Prosopium
williamsoni
(
Girard),
in
the
Logan
River,
Utah.
MS
Thesis,
Utah
State
University,
Logan,
UT.
40
pp.

Brown
RS,
MacKay
WC.
1995.
Spawning
ecology
of
cutthroat
trout
(
Oncorhynchus
clarki)
in
the
Ram
River,
Alberta.
Can
J
Fish
Aquat
Sci
52:
983­
992.

Bruce
PG,
Starr
PJ.
1985.
Fisheries
resources
potential
of
Williston
Reservoir
and
its
tributary
streams.
Volume
II.
Fisheries
resources
potential
of
Williston
Lake
tributaries
 
a
preliminary
overview.
BC
Ministry
of
Environment,
Fisheries
Branch,
Fisheries
Technical
Circular
Number
69.

Burger
CV,
Wilmot
RL,
Wangaard
DB.
1985.
Comparison
of
spawning
areas
and
times
for
two
runs
of
chinook
salmon
(
Oncorhynchus
tshawytscha)
in
the
Kenai
River,
Alaska.
Can
J
Fish
Aquat
Sci
42:
693­
700.

Cavallo
BJ.
1997.
Floodplain
habitat
heterogeneity
and
the
distribution,
abundance
and
behavior
of
fishes
and
amphibians
in
the
Middle
Fork
Flathead
River
Basin,
Montana.
Division
of
Biological
Sciences,
University
of
Montana,
Missoula.
128
pp.
29
Salmonid
Behavior
and
Water
Temperature
Cederholm
CJ,
Scarlett
WJ.
1981.
Seasonal
immigrations
of
juvenile
salmonids
into
four
small
tributaries
of
the
Clearwater
River,
Washington,
1977­
1981.
In:
Brannon
EL,
Salo
EO,
eds.
Proceedings
of
the
Salmon
and
Trout
Migratory
Behavior
Symposium.
School
of
Fisheries,
University
of
Washington,
Seattle.
pp.
98­
110.

Cherry
DS,
Dickson,
KL,
Cairns
J.
1977.
Preferred,
avoided,
and
lethal
temperatures
of
fish
during
rising
temperature
conditions.
J
Fish
Res
Bd
Can
34:
239­
246.

Cherry,
DS,
Dickson
KL,
Cairns
J.
1975.
Temperatures
selected
and
avoided
by
fish
at
various
acclimation
temperatures.
J
Fish
Res
Bd
Can
32(
4):
485­
491.

Coutant
CC.
1972a.
Effect
of
thermal
shock
on
vulnerability
to
predation
in
juvenile
salmonids.
I.
Single
shock
temperature.
AEC
Research
and
Development
Report.
Battelle
Pacific
Northwest
Laboratories.
BNWL­
1521.

Coutant
CC.
1972b.
Effect
of
thermal
shock
on
vulnerability
to
predation
in
juvenile
salmonids.
II.
A
dose
response
by
rainbow
trout
to
three
shock
temperatures.
AEC
Research
and
Development
Report.
Battelle
Pacific
Northwest
Laboratories.
BNWL­
1519.

Coutant
CC.
1999.
Perspectives
on
temperature
in
the
Pacific
Northwest's
fresh
waters.
Environmental
Sciences
Division
Publication
#
4849
(
ORNL/
TM­
1999/
44).
Oak
Ridge
National
Laboratory,
Oak
Ridge,
TN.

Crawshaw
LI,
Wollmuth
LP,
O'Connor
CS,
Rausch
RN,
Simpson
L.
1990.
Body
temperature
regulation
in
vertebrates:
Comparative
aspects
and
neuronal
elements.
Schonbaum
E,
Lomax
P,
eds.
Thermoregulation:
Physiology
and
biochemistry.
New
York:
Pergamon
Press.

De
Staso
JD,
Rahel
FJ.
1994.
Influence
of
water
temperature
on
interactions
between
juvenile
Colorado
River
cutthroat
trout
and
brook
trout
in
a
laboratory
stream.
Trans
Am
Fish
Soc
123:
289­
297.

Dickerson
BR,
Vineyard
GL.
1999.
Effects
of
high
chronic
temperatures
and
diel
temperature
cycles
on
the
survival
and
growth
of
Lahontan
cutthroat
trout.
Trans
Am
Fish
Soc
128:
516­
521.

Ebersol
JL,
Liss
WJ,
Frissell
CA.
In
Press.
Relationship
between
stream
temperature,
thermal
refugia,
and
rainbow
trout
Oncorhynchus
mykiss
abundance
in
arid­
land
streams
in
the
northwestern
United
States.
Ecol
Freshwater
Fish.

Elliot
JM.
1976.
The
energetics
of
feeding,
metabolism
and
growth
of
brown
trout
(
Salmo
trutta
L.)
in
relation
to
body
weight,
water
temperature
and
ration
size.
J
Animal
Ecol
45:
923­
948.

Elliot
JM.
1981.
Some
aspects
of
thermal
stress
on
freshwater
teleosts.
In:
Pickering
AD,
ed.
Stress
and
fish.
San
Diego,
CA:
Academic
Press,
pp.
209­
245.

Fry
FEJ.
1947.
Effects
of
the
environment
on
animal
activity.
Univ.
Toronto
Stud.,
Biol.
Ser.,
No.
55.
Pub
Ont
Fish
Res
Lab,
No.
68.
62
pp.

Fry
FEJ.
1971.
The
effect
of
environmental
factors
on
the
physiology
of
fish.
In:
Hoar
WS,
Randell
DJ,
eds.
Fish
physiology.
Vol.
VI:
Environmental
relations
and
behavior.
San
Diego,
CA:
Academic
Press,
pp.
1­
98.

Foerster
RE.
1937.
The
relation
of
temperature
to
the
seaward
migration
of
young
sockeye
salmon
(
Oncorhynchus
nerka).
J
Fish
Biol
Bd
Can
3:
421­
438.

Fraley
J,
Shepard
B.
1989.
Life
history,
ecology,
and
population
status
of
migratory
bull
trout
(
Salvelinus
confluentus)
in
the
Flathead
Lake
and
River
system,
Montana.
Northwest
Sci
63:
133­
143.

Fraser
NHC,
Metcalfe
NE,
Thorpe
JE.
1993.
Temperature­
dependent
switch
between
diurnal
and
nocturnal
foraging
in
salmon.
Proc
R
Soc
Lond
B:
135­
139.
30
Salmonid
Behavior
and
Water
Temperature
Frissell
CA,
Ebersol
JL,
Liss
WJ,
Cavallo
BJ,
Poole
GC,
Stanford
JA.
1996.
Potential
effects
of
climate
change
on
thermal
complexity
and
biotic
integrity
of
streams:
Seasonal
intrusion
of
non­
native
fishes.
U.
S.
Environmental
Protection
Agency,
Duluth,
MN.
#
CR­
822019­
01­
0.

Garside
ET,
Tait
JS.
1958.
Preferred
temperature
of
rainbow
trout
(
Salmo
gairdneri,
Richardson)
and
its
unusual
relationship
to
acclimation
temperature.
Can
J
Zool
36:
563­
567.

Geotz
FA.
1989.
Biology
of
the
bull
trout
Salvelinus
confluentus:
A
literature
review.
U.
S.
Forest
Service,
Willamette
National
Forest,
Eugene,
OR.

Gibson
RJ.
1966.
Some
factors
influencing
the
distributions
of
brook
trout
and
young
Atlantic
salmon.
J
Fish
Res
Bd
Can
23:
1977­
1980.

Gilhousen
P.
1980.
Energy
sources
and
expenditures
in
Fraser
River
sockeye
salmon
during
their
spawning
migration.
Int
Pac
Salmon
Fish
Comm
Bull
XXII:
51
pp.

Giorgi
AE,
Miller
DR,
Sandford
BP.
1994.
Migratory
characteristics
of
juvenile
ocean­
type
chinook
salmon,
Oncorhynchus
tshawytscha,
in
John
Day
Reservoir
on
the
Columbia
River.
US
Nat
Mar
Fish
Serv
Fish
Bull
92:
872­
879.

Godfrey
H,
Hourston
WR,
Stokes
JW,
Withler
FC.
1954.
Effects
of
a
rockslide
on
Babine
River
salmon.
Bull
Fish
Res
Bd
Can
No.
101.

Grant
JWA,
Steingrímsson
SÓ,
Keeley
ER,
Cunjak
RA.
1998.
Implications
of
territory
size
for
the
measurement
and
prediction
of
salmonid
abundance
in
streams.
Can
J
Fish
Aquat
Sci
55
(
Suppl
1):
181­
190.

Gray
GA,
Rondorf
DW.
1986.
Predation
on
juvenile
salmonids
in
Columbia
River
reservoirs.
In:
Hall
GE,
Van
Den
Avyle
MJ,
eds.
Reservoir
fisheries
management:
Strategies
for
the
80'
s.
Reservoir
Committee,
Southern
Division
American
Fisheries
Society,
Bethesda,
MD.

Groot
C,
Margolis
L,
eds.
1991.
Pacific
salmon
life
histories.
Vancouver:
University
of
British
Columbia
Press,
564
pp.

Haas
GR.
2000.
Unpublished
manuscript.
Maximum
temperature
and
habitat
mediated
interactions
and
preferences
of
bull
trout
(
Salvelinus
confluentus)
and
rainbow
trout
(
Oncorhynchus
mykiss).

Hammel
HT.
1968.
Regulation
of
internal
body
temperature.
Ann
Rev
Physiol
30:
641­
710.

Hazel
JR,
Prosser
CL.
1974.
Molecular
mechanisms
of
temperature
compensation
in
poikilotherms.
Physiol
Rev
54:
620­
677.

Hendry
AP,
Hensleigh
JE,
Reisenbichler
RR.
1998.
Incubation
temperature,
developmental
biology,
and
the
divergence
of
sockeye
salmon
(
Oncorhynchus
nerka)
within
Lake
Washington.
Can
J
Fish
Aquat
Sci
55:
1387­
1394.

Hicks
M.
1999.
Evaluating
standards
for
protecting
aquatic
life
in
Washington's
surface
water
quality
standards.
Preliminary
draft
of
draft
discussion
paper
(
vol.
1)
and
draft
supplementary
appendix
(
vol.
2).
WA
Dept
of
Ecology,
Water
Quality
Program,
Olympia,
WA.

Higgs
DA,
MacDonald
JS,
Levings
CD,
Dosanjh
BS.
1995.
Nutrition
and
feeding
habits
in
relation
to
life
history
stage.
In:
Groot
C,
Margolis
L,
Clarke
WC,
eds.
Physiological
ecology
of
Pacific
salmon.
Vancouver:
University
of
British
Columbia
Press,
pp.
159­
316.

Hildebrand
L,
English
K.
1991.
Lower
Columbia
River
fisheries
inventory.
1990
Studies.
Volume
I
Main
report.
Submitted
to
B.
C.
Hydro
Environmental
Resources
by
R.
L.
&
L.
Environmental
Services,
Ltd.,
Edmonton,
Alberta
and
LGL
Ltd.,
Sydney,
BC.
31
Salmonid
Behavior
and
Water
Temperature
Hillman
TW.
1991.
The
effect
of
temperature
on
the
spatial
interaction
of
juvenile
chinook
salmon
and
the
redside
shiner
and
their
morphological
differences.
PhD
dissertation.
Idaho
State
University,
Pocatello,
ID.
90
pp.

Hokanson
KEF,
Kleiner
CF,
Thorslund
TW.
1977.
Effects
of
constant
temperatures
and
diel
temperature
fluctuations
on
specific
growth
and
mortality
rates
and
yield
of
juvenile
rainbow
trout,
Salmo
gairdneri.
J
Fish
Res
Bd
Can
34:
639­
648.

Holtby
BL.
1988.
Effects
of
logging
on
stream
temperatures
in
Carnation
Creek,
British
Columbia,
and
associated
impacts
on
the
coho
salmon
(
Oncorhynchus
kisutch).
Can
J
Fish
Aquat
Sci
45:
502­
515.

Holtby
LB,
McMahon
TE,
Scrivener
JC.
1989.
Stream
temperatures
and
inter­
annual
variability
in
the
emigration
timing
of
coho
salmon
(
Oncorhynchus
kisutch)
smolts
and
fry
and
chum
salmon
(
O.
keta)
fry
from
Carnation
Creek,
British
Columbia.
Can
J
Fish
Aquat
Sci
46:
1396­
1405.

Horak
OL,
Tanner
HA.
1964.
The
use
of
vertical
gill
nets
in
studying
fish
depth
distribution,
Horsetooth
Reservoir,
Colorado.
Trans
Am
Fish
Soc
93:
137­
145.

Idler
DR,
Clemens
WA.
1959.
The
energy
expenditures
of
Fraser
River
sockeye
salmon
during
the
spawning
migration
to
Chilko
and
Stuart
Lakes.
Progress
Report,
Int.
Pac.
Salmon
Comm.
80
pp.

Independent
Scientific
Group.
1996.
Return
to
the
river:
Restoration
of
salmonid
fishes
in
the
Columbia
River
ecosystem.
Prepublication
copy.

Inhat
JM,
Bulkley
RV.
1984.
Influence
of
acclimation
temperature
and
season
on
acute
temperature
preference
of
adult
mountain
whitefish,
Prosopium
williamsoni.
Environ
Biol
Fish
11(
1):
29­
40.

Jakober
MJ,
McMahon
TE,
Thurow
RF,
Clancy
CG.
1998.
Role
of
stream
ice
on
fall
and
winter
movements
and
habitat
use
by
bull
trout
and
cutthroat
trout
in
Montana
headwater
streams.
Trans
Am
Fish
Soc
127:
223­
235.

James
PW,
Sexauer
HM.
1997.
Spawning
behavior,
spawning
habitat
and
alternative
mating
strategies
in
an
adfluvial
population
of
Bull
trout.
In:
Mackay
WC,
Brewin
MK,
Monita
M,
eds.
Friends
of
the
bull
trout
conference
proceedings.
Bull
Trout
Task
Force
(
Alberta),
c/
o
Trout
Unlimited
Canada,
Calgary.

Javaid
MY,
Anderson
JM.
1967.
Thermal
acclimation
and
temperature
selection
in
Atlantic
salmon,
Salmo
salar,
and
rainbow
trout,
S.
gairdneri.
J
Fish
Res
Bd
Can
24:
1507­
1513.

Jobling
M.
1981.
Temperature
tolerance
and
final
preferendum­
rapid
methods
for
the
assessment
of
optimum
growth
temperatures.
J
Fish
Biol
19:
439­
455.

Kaya
CM,
Kaeding
LR,
Burkhalter
DE.
1977.
Use
of
a
cold
water
refuge
by
rainbow
and
brown
trout
in
a
geothermally
heated
stream.
Progressive
Fish­
Culturist
39:
37­
39.

Kelsch
SW,
Neill
WH.
1990.
Temperature
preference
versus
acclimation
in
fishes:
Selection
for
changing
metabolic
optima.
Trans
Am
Fish
Soc
119:
601­
610.

Kilgour
DM,
McCauley
RW.
1986.
Reconciling
the
two
methods
of
measuring
upper
lethal
temperature
in
fishes.
Environ
Biol
Fish
17(
4):
281­
290.

King
W.
1937.
Notes
on
the
distribution
of
native
speckled
and
rainbow
trout
in
the
streams
of
the
Great
Smoky
Mountains
National
Park.
J
Tenn
Acad
Sci
12:
351­
361.

Kitchell
JF,
Stewart
DJ,
Weininger
D.
1977.
Applications
of
bioenergetics
model
to
yellow
perch
(
Perca
flavescens)
and
walleye
(
Stizostedion
vitreum
vitreum).
J
Fish
Res
Bd
Can
34:
1922­
1935.

Kluger
MJ.
1978.
The
evolution
and
adaptive
value
of
fever.
Am
Sci
66:
38­
43.
32
Salmonid
Behavior
and
Water
Temperature
Konecki
JT,
Woody
CA,
Quinn
TP.
1995.
Critical
thermal
maxima
of
coho
salmon
(
Oncorhynchus
kisutch)
fry
under
field
and
laboratory
acclimation
regimes.
Can
J
Zool
73:
993­
996.

Konecki
JT,
Woody
CA,
Quinn
TP.
1995.
Temperature
preference
in
two
populations
of
juvenile
coho
salmon,
Oncorhynchus
kisutch.
Environ
Biol
Fish
44:
417­
421.

Kraemer
C.
1994.
Some
observations
on
the
life
history
and
behavior
of
the
native
char,
Dolly
Varden
(
Salvelinus
malma)
and
bull
trout
(
Salvelinus
confluentus)
of
the
north
Puget
Sound
region.
Draft
report.
Washington
State
Department
of
Fish
and
Wildlife,
Mill
Creek,
WA.

Kwain
W,
McCauley
RW.
1978.
Effects
of
age
and
overhead
illumination
on
temperatures
preferred
by
underyearling
rainbow
trout,
Salmo
gairdneri,
in
a
vertical
temperature
gradient.
J
Fish
Res
Bd
Can
35:
1430­
1433.

LeBrasseur
RJ,
McAllister
CD,
Barraclough
WE,
Kennedy
OD,
Manzer
J,
Robinson
D,
Stephens
K.
1978.
Enhancement
of
sockeye
salmon
(
Oncorhynchus
nerka)
by
lake
fertilization
in
Great
Central
Lake:
Summary
report.
J
Fish
Res
Bd
Can
35:
1580­
1596.

Li
HW,
Lamberti
GA,
Pearsons
TN,
Tait
CK,
Li
JL,
Buckhouse
JC.
1994.
Cumulative
effects
of
riparian
disturbances
along
high
desert
trout
streams
of
the
John
Day
Basin,
Oregon.
Trans
Am
Fish
Soc
123:
627­
640.

Li
HW,
Shreck
CB,
Bond
CE,
Rexstad
E.
1987.
Factors
influencing
changes
in
fish
assemblages
of
Pacific
Northwest
streams.
In:
Matthews
WJ,
Heins
DC,
eds.
Community
and
evolutionary
ecology
of
North
American
stream
fishes.
Norman,
OK:
University
of
Oklahoma
Press,
pp.
193­
202.

Magnuson
JJ,
Crowder
LB,
Medvick
PA.
1979.
Temperature
as
an
ecological
resource.
Am
Zool
19:
331­
343.

Major
RL,
Mighel
JL.
1967.
Influence
of
Rocky
Reach
Dam
and
the
temperature
of
the
Okanogan
River
on
the
upstream
migration
of
sockeye
salmon.
Fish
Bull
66(
1):
131­
147.

Mantelman
II.
1958.
Distribution
of
the
young
of
certain
species
of
fish
in
temperature
gradients.
Izv
Vses
Nauchno­
Issled
Inst
Ozern
Rechn
Rybn
Khoz
47:
3­
61.
(
Translated
from
the
Russian
by
Fish
Res
Board
Can
Transl
Ser
257,
1960.)

Maule
AG,
Horton
HF.
1985.
Probable
causes
of
the
rapid
growth
and
high
fecundity
of
walleye,
Stizostedion
vitreum
vitreum,
in
the
mid­
Columbia
River.
Fish
Bull
83(
4):
701­
706.

McCauley
RW,
Elliot
JR,
Read
ALA.
1977.
Influence
of
acclimation
temperature
on
preferred
temperature
of
rainbow
trout,
Salmo
gairdneri.
Trans
Am
Fish
Soc
106:
362­
365.

McCauley
RW,
Huggins
NW.
1979.
Ontogenetic
and
non­
thermal
seasonal
effects
on
thermal
preferenda
of
fish.
Am
Zool
19:
267­
271.

McCauley
RW,
Pond
WL.
1971.
Temperature
selection
of
rainbow
trout
(
Salmo
gairdneri)
fingerlings
in
vertical
and
horizontal
gradients.
J
Fish
Res
Bd
Can
28:
1801­
1804.

McCullough
DA.
1999.
A
review
and
synthesis
of
effects
of
alterations
to
the
water
temperature
regime
on
freshwater
life
stages
of
salmonids,
with
special
reference
to
chinook
salmon.
Report
to
the
U.
S.
Environmental
Protection
Agency,
Region
10,
Seattle,
WA.

McIntosh
BA,
Price
DM,
Torgersen
CE,
Li
HW.
1995.
Distribution,
habitat
utilization,
movement
patterns,
and
the
use
of
thermal
refugia
by
spring
chinook
in
the
Grande
Ronde,
Imnaha,
and
John
Day
Basins.
Progress
report
to
the
Bonneville
Power
Administration,
Project
No.
88­
108,
FY
1995.

McMahon
T,
Zale
A,
Selong
J,
Barrows
R.
1999.
Growth
and
survival
temperature
criteria
for
bull
trout.
Annual
report
to
National
Council
for
Air
and
Stream
Improvement.
Bozeman,
MT.
33
Salmonid
Behavior
and
Water
Temperature
Meeuwig
MH.
2000.
Effects
of
constant
and
cyclical
thermal
regimes
on
growth,
feeding,
and
swimming
performance
of
cutthroat
trout
of
variable
sizes.
MS
thesis,
University
of
Nevada,
Reno.

Mesa
MG.
1994.
Effects
of
multiple
acute
stressors
on
the
predation
avoidance
ability
and
physiology
of
juvenile
chinook
salmon.
Trans
Am
Fish
Soc
123:
786­
793.

Mesa
MG,
Poe
TP,
Maule
AG,
Shreck
CB.
1998.
Vulnerability
to
predation
and
physiological
stress
responses
in
juvenile
salmon
(
Oncorhynchus
tshawytscha)
experimentally
infected
with
Renibacterium
salmoninarum.
Can
J
Fish
Aquat
Sci
55:
1599­
1606.

Nakano
S,
Fausch
KD,
Furukawa­
Tanaka
T,
Maekawa
K,
Kawanabe
H.
1998.
Resource
utilization
by
bull
char
and
cutthroat
trout
in
a
Montana
stream
in
Montana,
USA.
Jap
J
Ichtyol
39:
211­
217.

National
Research
Council.
1996.
Upstream:
Salmon
and
society
in
the
Pacific
Northwest.
Washington,
DC:
National
Academy
Press.
452
pp.

Nehlsen
W,
Williams
JE,
Lichatowich
JA.
1991.
Pacific
salmon
at
the
crossroads:
Stocks
at
risk
from
California,
Oregon,
Idaho,
and
Washington.
Fisheries
16(
2):
4­
21.

Neill
WH.
1979.
Mechanisms
of
fish
distribution
in
heterothermal
environments.
Am
Zool
19:
305­
317.

Neilsen
JL,
Lisle
TE,
Ozaki
V.
1994.
Thermally
stratified
pools
and
their
use
by
steelhead
in
northern
California
streams.
Trans
Am
Fish
Soc
23:
613­
626.

NMFS
(
National
Marine
Fisheries
Service).
1998.
Progress
of
species
status
reviews
in
NMFS
Northwest
Region.
File
1
pg
898.
pfd
at
NOAA
website
http://
www.
noaa.
gov.

NMFS
Chinook
Status
Review:
Myers
JM,
Kope
RG,
Bryant
GJ,
Teel
D,
Lierheimer
LJ,
Wainwright
TC,
Grant
WS,
Waknitz
FW,
Neely
K,
Lindley
ST,
Waples
RS.
1998.
Status
review
of
chinook
salmon
from
Washington,
Idaho,
Oregon,
and
California.
U.
S.
Department
of
Commerce,
NOAA
Tech
Memo.
NMFS­
NWFSC­
35.
443
pp.

NMFS
Coho
Status
Review:
Weitkamp
LA,
Wainwright
TC,
Bryant
GJ,
Milner
GB,
Teel
DJ,
Kope
RG,
Waples
RS.
Status
review
of
coho
salmon
from
Washington,
Oregon,
and
California.
U.
S.
Department
of
Commerce,
NOAA
Tech.

Northcote
TG.
1997.
Potamodromy
in
Salmonidae
 
Living
and
moving
in
the
fast
lane.
N
Am
J
Fish
Manage
17:
1029­
1045.

ODEQ
(
Oregon
Department
of
Environmental
Quality).
1995.
1992­
1994
Water
quality
standards
review.
Department
of
Environmental
Quality,
Standards
and
Assessment
Section.
Final
issues
papers.
Portland,
OR.

Olson
PA,
Foster
RF.
1955.
Temperature
tolerance
of
eggs
and
young
of
Columbia
River
chinook
salmon.
Trans
Am
Fish
Soc
85:
203­
207.

Petersen
J,
Barfoot
C,
Sauter
S,
Gadomski
D,
Connolly
P,
Poe
T.
2000.
Predicting
the
effects
of
dam
breaching
in
the
lower
Snake
River
on
predators
of
juvenile
salmon.
Report
prepared
for
U.
S.
Army
Corps
of
Engineers,
Walla
Walla
District,
Walla
Walla,
WA.

Petersen
JH,
DeAngelis
DL.
1992.
Functional
response
and
capture
timing
in
an
individual­
based
model:
Predation
by
northern
squawfish
(
Ptychocheilus
oregonensis)
on
juvenile
salmonids
in
the
Columbia
River.
Can
J
Fish
Aquat
Sci
49:
2551­
2565.

Pettit
SW,
Wallace
RL.
1975.
Age,
growth,
and
movement
of
mountain
whitefish
Prosopium
williamsoni
(
Girard),
in
the
North
Fork
Clearwater
River,
Idaho.
Trans
Am
Fish
Soc
1:
68­
76.
34
Salmonid
Behavior
and
Water
Temperature
Pianka
ER.
1994.
Evolutionary
ecology.
New
York:
Harper
Collins
College
Publishers,
pp.
82­
120.

Poe
TP,
Hansel
HC,
Vigg
S,
Palmer
DE,
Prendergast
LA.
1991.
Feeding
of
predaceous
fishes
on
out­
migrating
juvenile
salmonids
in
John
Day
Reservoir,
Columbia
River.
Trans
Am
Fish
Soc
120(
4):
405­
419.

Poe
TP,
Shively
RS,
Tabor
RA.
1994.
Ecological
consequences
of
introduced
piscivorous
fishes
in
the
lower
Columbia
and
Snake
Rivers.
In:
Stouder
D,
Fresh
K,
Feller
R,
eds.
Theory
and
application
in
fish
feeding
ecology.
Columbia,
SC:
University
of
SC
Press,
pp.
347­
360.

Poole
GC,
Berman
CH.
In
Press.
An
ecological
perspective
on
in­
stream
temperature:
Natural
heat
dynamics
and
mechanisms
of
human­
caused
thermal
degradation.
Ecol
Manage.

Pratt
KL.
1992.
A
review
of
bull
trout
life
history.
In:
Howell
P,
Buchanan
D,
eds.
Proceedings
of
the
Gearhart
Mountain
Bull
Trout
Workshop.
Oregon
Chapter
of
the
American
Fisheries
Society.

Quinn
TP,
Adams
DJ.
1996.
Environmental
changes
affecting
the
migratory
timing
of
American
shad
and
sockeye
salmon.
Ecology
77(
4):
1151­
1162.

Raleigh
RF,
Miller
WF,
Nelson
PC.
1986.
Habitat
suitability
index
models
and
instream
flow
suitability
curves:
Chinook
salmon.
US
Fish
Wildlife
Serv
Biol
Rep
82(
10.122).
64
pp.

Reeves
GH,
Everest
JD,
Hall
JD.
1987.
Interaction
between
redside
shiner
(
Richardsonius
balteatus)
and
the
steelhead
trout
(
Salmo
gairdneri)
in
western
Oregon:
The
influence
of
water
temperature.
Can
J
Fish
Aquat
Sci
44:
1603­
1613.

Reiman
BE,
Chandler
GL.
1999.
Empirical
evaluation
of
temperature
effects
on
bull
trout
distribution
in
the
Northwest.
Final
Report,
Contract
No.
12957242­
01­
0,
U.
S.
Environmental
Protection
Agency,
Boise,
ID.

Reiser
DW,
Bjornn
TC.
1979.
Habitat
requirements
of
anadromous
salmonids.
Gen
Tech
Rep
PNW96.
USDA
Forest
Service.
Pacific
Northwest
Forest
and
Range
Experiment
Station.
Portland,
OR.
54
pp.

Reutter
JM,
Herdendorf
CE.
1974.
Laboratory
estimates
of
the
seasonal
final
temperature
preferenda
of
some
Lake
Erie
fish.
Proc
17th
Conf
Great
Lakes
Res
1974:
59­
67.

Reynolds
WW.
1977a.
Temperature
as
a
proximate
factor
in
orientation
behavior.
J
Fish
Res
Bd
Can
34:
734­
739.

Reynolds
WW.
1977b.
Fever
and
antipyresis
in
the
bluegill
sunfish,
Lepomis
macrochirus.
Comp
Biochem
Physiol
57C
(
2):
165­
167.

Reynolds
WW,
Casterlin
ME.
1979.
Behavioral
thermoregulation
and
the
"
final
preferendum"
paradigm.
Am
Zool
19:
211­
224.

Reynolds
WW,
Casterlin
ME,
Covert
JB.
1976.
Behavioral
fever
in
teleost
fishes.
Nature
259:
41­
42.

Reynolds
WW,
Covert
JB.
1977.
Behavioral
fever
in
aquatic
ectothermic
vertebrates.
In:
Drugs,
biogenic
amines
and
body
temperature.
Proceedings
of
the
3rd
International
Symposium
on
Pharmacological
Thermoregulation,
Banff,
Alberta,
14­
17
Sept
1976
(
Karger,
Basel).

Roper
BB,
Scarnecchia
DL,
Marr
TJL.
1994.
Summer
distribution
of
and
habitat
use
by
chinook
salmon
and
steelhead
within
a
major
basin
of
the
South
Umpqua
River,
Oregon.
Trans
Am
Fish
Soc
123:
298­
308.

Royce
WF.
1962.
Pink
salmon
fluctuations
in
Alaska.
In:
Wilimovsky
NJ,
ed.
Symposium
on
Pink
Salmon.
H.
R.
MacMillan
Lectures
in
Fisheries.
Institute
of
Fisheries,
University
of
British
Columbia,
Vancouver,
BC.
pp.
15­
23.
35
Salmonid
Behavior
and
Water
Temperature
Saffel
PD,
Scarnecchia
DL.
1995.
Habitat
use
by
juvenile
bull
trout
in
belt­
series
geology
watersheds
of
northern
Idaho.
Northwest
Sci
69:
304­
317.

Sauter
ST.
1996.
Thermal
preference
of
spring
and
fall
chinook
salmon
during
smoltification.
MS
thesis.
Portland
State
University,
Portland,
OR.

Schroeter
RE.
1998.
Segregation
of
stream­
dwelling
Lahontan
cutthroat
trout
and
brook
trout:
Patterns
of
occurrence
and
mechanisms
for
displacement.
MS
thesis,
University
of
Nevada,
Reno.

Scrivener
JC,
Brown
TG,
Andersen
BC.
1994.
Juvenile
chinook
salmon
(
Oncorhynchus
tshawytscha)
utilization
of
Hawks
Creek,
a
small
and
nonnatal
tributary
of
the
upper
Fraser
River.
Can
J
Fish
Aquat
Sci
51:
1139­
1146.

Sheridan
WL.
1962.
Relation
of
stream
temperatures
to
timing
of
pink
salmon
escapements
in
southeast
Alaska.
pp.
87­
102.
In:
Wilimovsky
NJ,
ed.
Symposium
on
pink
salmon.
H.
R.
Macmillan
Lectures
in
Fisheries,
University
of
British
Columbia.
Vancouver,
British
Columbia,
Canada.

Snucins
EJ,
Gunn
JM.
1995.
Coping
with
a
warm
environment:
Behavioral
thermoregulation
by
lake
trout.
Trans
Am
Fish
Soc
124:
118­
123.

Spence
BC,
Lomnicky
GA,
Hughes
RM,
Novitzki
RP.
1996.
An
ecosystem
approach
to
salmonid
conservation.
ManTech
Environ
Res
Serv
Corp,
Corvallis,
OR.
TR­
4501­
96­
6057.

Spigarelli
SA.
1975.
Behavioral
responses
of
Lake
Michigan
fishes
to
a
nuclear
power
plant
discharge.
In:
Environmental
effects
of
cooling
systems
at
nuclear
power
plants.
International
Atomic
Energy
Agency
(
IAEA),
Vienna.
pp.
479­
498.

Swanberg
TR.
1997.
Movements
of
and
habitat
use
by
fluvial
bull
trout
in
the
Blackfoot
River,
Montana.
Trans
Am
Fish
Soc
126:
735­
746.

Tabor
RA,
Shively
RS,
Poe
TP.
1993.
Predation
on
juvenile
salmonids
by
smallmouth
bass
and
northern
squawfish
in
the
Columbia
River
near
Richland,
Washington.
N
Am
J
Fish
Manage
13:
831­
838.

Taniguchi
R,
Rahel
FJ,
Novinger
DC,
Gerow
KG.
1998.
Temperature
mediation
of
competitive
interactions
among
three
fish
species
that
replace
each
other
along
longitudinal
stream
gradients.
Can
J
Fish
Aquat
Sci
55:
1894­
1901.

Theurer
FD,
Lines
I,
Nelson
T.
1985.
Interaction
between
riparian
vegetation,
water
temperature,
and
salmonid
habitat
in
the
Tucannon
River.
Water
Res
Bull
21:
53­
64.

Thompson
GE,
Davies
RW.
1976.
Observations
on
the
age,
growth,
reproduction,
and
feeding
of
mountain
whitefish
(
Prosopium
williamsoni)
in
the
Sheep
River,
Alberta.
Trans
Am
Fish
Soc
105:
208­
219.

Torgersen
CE,
Price
DM,
Li
HW,
McIntosh
BA.
1999.
Multiscale
thermal
refugia
and
stream
habitat
associations
of
chinook
salmon
in
northeastern
Oregon.
Ecol
Appl
9:
301­
309.

Trotter
P.
1989.
Coastal
cutthroat
trout:
A
life
history
compendium.
Trans
Am
Fish
Soc
118:
463­
473.

Vigg
S,
Poe
TP,
Prendergast
LA,
Hansel
H.
1991.
Rates
of
consumption
of
juvenile
salmonids
and
alternative
prey
fish
by
northern
squawfish,
walleyes,
smallmouth
bass,
and
channel
catfish
in
John
Day
Reservoir,
Columbia
River.
Trans
Am
Fish
Soc
120:
421­
438.

Withers
PC.
1992.
Comparative
animal
physiology.
New
York:
Saunders
College
Publishing,
pp.
122­
191.

Wydoski
RS,
Whitney
RR.
1979.
Inland
fishes
of
Washington.
Seattle:
University
of
Washington
Press.
36
Salmonid
Behavior
and
Water
Temperature
Young
MK.
1995.
Colorado
River
cutthroat
trout.
In:
Young
MK,
ed.
Conservation
assessment
for
inland
cutthroat
trout.
USDA
Forest
Service,
Gen.
Tech.
Report
RM­
GTR­
256.
pp.
16­
23.

Zaugg
WS,
Wagner
HH.
1973.
Gill
ATPase
activity
related
to
parr­
smolt
transformation
and
migration
in
steelhead
trout
(
Salmo
gairdneri):
Influence
of
photoperiod
and
temperature.
Comp
Biochem
Physiol
45B:
955­
965.

Zimmerman
MP,
Parker
RM.
1995.
Relative
density
and
distribution
of
smallmouth
bass,
channel
catfish,
and
walleye
in
the
lower
Columbia
and
Snake
rivers.
Northwest
Sci
69:
19­
28.
