Lentic habitat preferences of juvenile Chinook salmon in experimental arenas Chris Sergeant R.Tabor.
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Transcript of Lentic habitat preferences of juvenile Chinook salmon in experimental arenas Chris Sergeant R.Tabor.
Lentic habitat preferences of
juvenile Chinook salmon in
experimental arenas
Chris Sergeant
R.Tabor
Habitat and salmon
• In both streams and lakes, salmon are often found in shallow, nearshore zones
• Functions of nearshore habitat:
• Foraging• Refuge• Migration corridor
• Little is known about juvenile Chinook salmon that rear in lakes before migrating to saltwater
Lake Washington nearshore habitat and Chinook salmon
• L. Washington Chinook listed as threatened under the ESA
• Human-induced habitat changes: a main cause of salmon population decline?
• Shoreline restoration projects
• Does nearshore habitat affect the productivity of Chinook salmon in Lake Washington?
Ship Canal
Cedar River
Emergence: January - March
River Lake
Pelagic/Littoral: May - July
Littoral
Salt Migration: June – Sept.
Cedar River juvenile Chinook:
Life history patterns
Temporal movement
• Littoral zone: January – June
• Pelagic zone: Mid-May - July
Field observations of lake-rearing chinook(Tabor and Piaskowski 2001)
Habitat use patterns
• Low bottom slope• Sand, gravel substrate• Shallow water < 0.5 m
R.Tabor
Try isolating the habitat variables!
• Examine effects of physical habitat factors
• Slope
• Substrate
• Substrate-cover combinations
• Examine effects of biotic factors
• Predator presence
• Ontogenetic shifts
2004 objectives
SlopePredator present
Predator absent
NA
5%
10%
15%
20%
SubstratePredator present
Predator absent
Sand
Gravel
Sand/Cobble
Cobble
Predator present Predator absent
SubstrateNo
coverWoody debris
Overhead cover
No cover
Woody debris
Overhead cover
Sand
Gravel
Sand/Cobble
Cobble
N = 80Y = % fish in each slope; water column location;
location within slope patch
N = 20Y = % fish in each substrate
N = 60Y = % fish in each
substrate/cover combination
Observe over 3 diel periods, repeat for 2 life stages
Slope experiments Substrate experiments
Substrate/Cover experiments
Methods cont’d
• Source of fish: WDFW Issaquah Creek hatchery
• Fish were fed daily in holding tanks, but not during experiments
• Before experiments:
• Naïve fish chosen randomly• Holding cage within arena• Acclimation period
• After acclimation period, observations were made over the following 24-hour period
5%
15%
10% 20%
Slope arena
Slope experimentsFry
• No diel or predation effects
• Deep neutral area most preferred
• 20% slope least preferred
• Cutthroat most often in 5% or neutral area
0.0
0.2
0.4
0.6E
lect
ivit
y in
dex
(al
ph
a)
0.0
0.2
0.4
Slope
Neutral area 5% 10% 15% 20%0.0
0.2
0.4
Crepuscular
Night
No cutthroat
Cutthroat presentDay
Slope experimentsPresmolts
Ele
ctiv
ity
ind
ex (
alp
ha)
0.0
0.2
0.4
0.0
0.2
0.4
0.6
No cutthroatCutthroat present
Slope
Neutral area 5% 10% 15% 20%0.0
0.2
0.4
Crepuscular
Night
Day
• No diel or predation effects
• Strong preference for deep neutral area
• Both 15% and 20% slopes avoided
Substrate arenas
Pro
po
rtio
na
l us
e
0.0
0.2
0.4
0.0
0.2
0.4
0.6
Substrate
Sand Gravel Sand/Cobble Cobble0.0
0.2
0.4
Crepuscular
Night
Day
SculpinNo sculpin
Substrate experimentsFry
• Substrate preferences shift with diel period
• No predation effect
• Sculpin mainly in cobble, rarely in sand
Substrate experimentsPresmolt
Substrate
Sand Gravel Sand/Cobble Cobble0.0
0.2
0.4
Pro
po
rtio
nal
use
0.0
0.2
0.4
0.0
0.2
0.4
0.6
Crepuscular
Night
Day
Sculpin
No sculpin• Similar, but looser, trends than fry
• No predation effect
Substrate-Cover arenas
Substrate-Cover arenas
Substrate-coverexperiments
PresmoltSculpin present
Substrate
SandGrav SC Cobb0.00
0.05
0.10
0.15
FrySculpin present
Pro
port
iona
l use
0.00
0.05
0.10
0.15
PresmoltNo sculpin
SandGrav SC Cobb
FryNo sculpin
No coverOverhead coverWoody debris
No coverOverhead coverWoody debris
• No cover, cobble most used by fry
• No patterns in presmolt data
• Note small y-axis scale
Conclusions• Experimental findings support Lake Washington field observations of Tabor and Piaskowski (2001)
• Slope experiments:• No strong selection for slope• Steep slopes avoided
• Substrate experiments:• At night, fry preferred finer substrate• No strong preference during day and crepuscular
• Substrate/cover experiments:• No strong preference for any particular substrate/cover combination
• Diel and predation effects were not usually present
• Larger arenas
• Examine substrate/cover combinations
• Cruising predators• Predator density thresholds• Combinations of predators
Directions for future experimental research
Acknowledgements• Committee: Dave Beauchamp, Tom Quinn, Roger Tabor
• Seattle Public Utilities: Julie Hall, Keith Kurko
• USGS – Sand Point: Jeff Duda, Reg Reisenbichler
• UW Hatchery: Dave Rose, Jon Wittouck
• WDFW Issaquah Creek Hatchery
• Beauchamp group: Alison, Angie, Erik, Hilary, Jen, Jim, Liz, Mike, Nathanael, Sarah, Steve
UNIVERSITY OF WASHINGTON
How many docks are out there?
0
500
1000
1500
2000
2500
3000
1940 1950 1960 1970 1980 1990 2000
Year
Nu
mb
er o
f D
ock
s
0.0
10.0
20.0
30.0
40.0
Nu
mb
er o
f D
ock
s/M
ile
Hockett DataUW Data
Figure courtesy of J. Toft
Slope experiments:Water column location
Fry0.0
0.2
0.4
0.6
0.8
1.0P
rop
ort
ion
al u
se
0.0
0.2
0.4
0.6
0.8 Cutthroat presentNo cutthroat
Water column location
Bottom Middle Top Entire0.0
0.2
0.4
0.6
0.8
Crepuscular
Night
Day • Top of the water column rarely used
• Bottom of the water column used heavily at night, especially around predators
0.0
0.2
0.4
0.6
0.8
1.0P
rop
ort
ion
al u
se
0.0
0.2
0.4
0.6
0.8Cutthroat presentNo cutthroat
Water column location
Bottom Middle Top Entire0.0
0.2
0.4
0.6
0.8
Crepuscular
Night
Day • Top of the water rarely used
• No predation effect
Slope experiments:Water column location
Presmolt
Slope experiments:Patch location
Fry
0.0
0.2
0.4
0.6P
rop
ort
ion
al u
se
0.0
0.2
0.4
Slope unit location
Nearshore Center Offshore Cruiser0.0
0.2
0.4
Cutthroat presentNo cutthroat
Crepuscular
Night
Day• No diel or predation effect
• Cruising fish most common
0.0
0.2
0.4
0.6
0.8P
rop
ort
ion
al u
se
0.0
0.2
0.4
0.6
Slope unit location
Nearshore Center Offshore Cruiser0.0
0.2
0.4
0.6
0.8
Cutthroat presentNo cutthroat
Crepuscular
Night
Day
Slope experiments:Patch location
Presmolts
• No diel or predation effect
• Offshore and cruisers most common
Slope experiment summary
• The presence of cutthroat trout and effect of diel period had minimal effects on slope preferences
• Deep neutral area most preferred habitat patch by fry and presmolts
• Steep slopes avoided
• At night, most fish move to bottom of water column
• Most presmolts used offshore regions of slope patches or cruised
• No strong preference for any slope patch