Emigration behavior of resident and anadromous juvenile O. mykiss: exploring the interaction among genetics, physiology and habitat

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Emigration behavior of resident and anadromous
juvenile O. mykiss exploring the interaction
among genetics, physiology and habitat Se
an Hayes, Chad Hanson, Morgan Bond, Devon
Pearse, Andrew Jones, Carlos Garza, Bruce
MacFarlane
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Scott Creek

• Small watershed (75km2)
• 23km of stream accessible to anadromous fish
• native resident fish above barriers
• Small hatchery
• Dynamic flow regime
• (28m3 s-1 to 0.1m3 s-1)
• Small Estuary (closes seasonally)

Map Rob Schick, NMFS
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Scott Creek O. mykiss life history strategies
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Scott Creek
X barrier
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?
x
x
x
Proportion of fish assigned to Resident or
Anadromous
ancestry by habitat
100
90
80
70
Anadromous
60
Resident
50
40
30
20
10
0
Above Barrier
Upstream
Smolt trap
Estuary
7
Genotype distribution in upper watershed
0.40
0.30
Resident (n128)
Frequency
Anadromous (n209)
0.20
0.10
0.00
50
70
90
110
130
150
170
190
210
230
250
270
Fork length
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Emigration rate from above anadromy barrier

• 400 fish PIT tagged above
• 2.3 over the falls
• 1.8 detected at smolt trap

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Na K-ATPase Physiology
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Na K-ATPase Physiology
Resident
6
Anadromous
Frequency
4
2
0
0
2
4
6
8
10
12
14
16
ATPase
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Why do wild fish migrate at such small sizes?
0.16
0.12
Frequency
0.08
0.04
0
50
70
90
110
130
150
170
190
210
230
250
Fork Length (mm)
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Does estuary serve as nursery habitat?(Morgan
Bonds thesis)
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Is the estuary a nursery?
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What happens when water quality degrades?
gt45 detected moving Upstream each
fall (probably gt90)
3 km
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Size of recaps at smolt trap in spring
20
18
16
Upstream
Estuary (previous summer)
14
12
Frequency
10
8
6
4
2
0
60
80
100
120
140
160
180
200
220
240
260
280
300
Fork Length
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A tale of two watersheds
No estuary available
(in Central California)
Year 1
Functional estuary present
Year 1
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• Land Owner support
• Big Creek Lumber Company
• The Wilson Family
• Monterey Bay Salmon and Trout Project
• Cal Poly Swanton Ranch
• Lockheed Martin

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Implications of resident trout studies

• Should residents be counted in steelhead
  populations for delisting criteria?
• Residents may become steelhead, but this probably
  happens at low frequencies
• Results of resident contribution to anadromous
  breeding pending

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Estuary Environmental Conditions
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Influence of genotype on migration behavior
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Steelhead in Scott Creek
Typical spring downstream migrant (smolt?)
85 of returning adults use estuary pathway
100mm
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Big smolts are less likely to stay
Probability of recapture
lt
Fork Length (mm) at Trap
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Conclusions

• Central Coast steelhead adapt for estuarine use
• Steelhead strategies without estuary
• Longer upstream rearing
• Fewer smolts, reduced anadromy?

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Density-dependent Estuary Growth in Steelhead
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Implications for Local Rivers

• Larger river- may have more rearing capacity
  larger smolts upstream
• BUT is there enough water?
• Estuary issues
• Breaching
• Estuary size reduced?
• Enough flow to connect with watershed?

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Lagoon fish move upstream in the fall and then
back down in spring
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Early 20th century spawning population was 4-10
times larger
Escapement ??
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Why is estuary growth so good?(Jeff Hardings
diet studies)
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But where does food come from?

• Upper watershed growth poor
• Insect diet
• Low flow
• Low light
• low nutrient input into estuary

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Hypothesis- Nutrient flow from marine derived
nutrients (kelp) enhances productivity (Alison
Collins senior thesis)
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Why dont all fish recruit to the estuary?