Steelhead trout life history

1
Steelhead trout life history

• SDP/DSV models meet data

W. Satterthwaite M. Mangel - UCSC, D. Swank,
S. Sogard, M. Beakes - NOAA J. Merz -
EBMUD, Cramer Fish Sciences R. Titus E.
Collins - CDFG
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Thinking about steelhead life history

• Why mature as resident?
• Avoid ocean mortality
• Potentially easier iteroparity
• Why smolt and emigrate?
• Much larger size gt higher reproductive success
• Why take action when young?
• Less cumulative risk of mortality in stream
• Why take action when older?
• Larger size at spawning higher reproduction
• Larger size at emigration higher survival

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Model algorithm
Tradeoff between future growth, further mortality
risk

• Postulates existence of decision windows
• Assess current size and potential for future
  growth as parr
• Assess expected fitness if smolt/mature at
  current size
• Compare with expected fitness of growing to a
  larger size and making an optimal decision in the
  future
• (discount for mortality)
• For now, concentrate on females

4
Timing is everything (thanks to D. Swank)
Age 4
Age 3
Age 2
Age 1
Age 0
Age 5
rainbow
Birth
1.1
smolt-1
1.2
1.3
freshwater parr
1.4
rainbow
mature resident parr
?
2.1
smolt-2
2.2
smolt
immature ocean
2.3
mature ocean
rainbow
maturity decision
smolt decision
3.1
smolt-3
3.2
3.3
5
Timing is everything (thanks to D. Swank)
Age 4
Age 3
Age 2
Age 1
Age 0
Age 5
rainbow
Birth
steelhead
smolt-1
rainbow
freshwater parr
steelhead
smolt-2
mature resident parr
rainbow
smolt
steelhead
smolt-3
ocean steelhead
rainbow
steelhead
smolt-4
maturity decision
smolt decision
. . .
6
Timing is everything (thanks to D. Swank)
Age 4
Age 3
Age 2
Age 1
Age 0
Age 5
rainbow
Birth
steelhead
smolt-1
rainbow
freshwater parr
steelhead
smolt-2
mature resident parr
rainbow
smolt
steelhead
smolt-3
ocean steelhead
rainbow
steelhead
smolt-4
maturity decision
smolt decision
X
7
Timing is everything (thanks to D. Swank)
Age 4
Age 3
Age 2
Age 1
Age 0
Age 5
rainbow
Birth
steelhead
smolt-1
rainbow
freshwater parr
steelhead
smolt-2
mature resident parr
rainbow
smolt
steelhead
smolt-3
ocean steelhead
rainbow
steelhead
smolt-4
maturity decision
smolt decision
8
Timing is everything (thanks to D. Swank)
Age 4
Age 3
Age 2
Age 1
Age 0
Age 5
rainbow
Birth
steelhead
smolt-1
rainbow
freshwater parr
steelhead
smolt-2
mature resident parr
rainbow
smolt
steelhead
smolt-3
ocean steelhead
steelhead
smolt-4
maturity decision
smolt decision
9
Dynamic State Variable model

• F(l,g,e,t)
• F expected lifetime fitness
• l size
• g developmental switch, maturity
• e developmental switch, smolting
• t time
• G(l,g,e,t) - future size at time t1
• s(t) - survival to time t1

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Dynamic State Variable model

• F(l,b,g,e,t)
• F fitness
• l size at t end of window
• b size at start of window
• g developmental switch, maturity
• e developmental switch, smolting
• t time
• G(l,b,g,e,t) - updated future size

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Terminal reward - Spawning

• Latest possible spawning
• F(l,g,e,Tsf) ?(l) if g1,
• F(l,g,e,Tsf) 0 otherwise

12
Terminal reward - Spawning

• Latest possible spawning
• F(l,g,e,Tsf) ?(l) if g1,
• F(l,g,e,Tsf) 0 otherwise
• Earlier spawnings
• F(l,g,e,ts) ?(l) s(t)F(G(l,g,e,ts),g,e,ts1)
  if g1,
• F(l,g,e,ts) s(t)F(G(l,g,e,ts),g,e,ts1)
  otherwise

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Terminal reward - Emigrating

• F(l,g,e,te) ?(l)? if e1,
• F(l,g,e,te) s(t)F(G(l,g,e,te),g,e,te1)
  otherwise
• F(l,g,e,t) s(t) F(G(l,g,e,t),g,e,t1)

Updating - Outside Windows
14
Terminal reward - Emigrating

• F(l,g,e,te) ?(l)? if e1,
• F(l,g,e,te) s(t)F(G(l,g,e,te),g,e,te1)
  otherwise
• F(l,g,e,t) s(t) F(G(l,g,e,t),g,e,t1)

Updating - Outside Windows
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Maturity Decision Window

• F(l,b,g,e,tdg) s(t) maxg( F(G(l,b,g,0,tdg),g,e
  ,tdg1))
• if ge0,
• F(l,g,e,tdg) s(t) F(G(l,b,g,e,tdg),g,e,tdg1
  ) otherwise.

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Maturity Decision Window

• F(l,b,g,e,tdg) s(t) maxg( F(G(l,b,g,0,tdg),g,e
  ,tdg1))
• if ge0,
• F(l,g,e,tdg) s(t) F(G(l,b,g,e,tdg),g,e,tdg1
  ) otherwise.
• F(l,b,g,e,tde) s(t) maxe( F(G(l,b,0,e,tde),g
  ,e,tde1))
• if ge0,
• F(l,g,e,tde) s(t) F(G(l,b,g,e,tde),g,e,tde1
  ) otherwise.

Smolting Decision Window
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Inputs Survival and Growth

• Survival CJS MARK-recapture model
• Pit tagged fish recapture rates
• Separate analysis of YOY vs older fish
• Seasonal but not yearly variation
• Biased low - confounded with emigration

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Inputs Survival and Growth

• Survival CJS MARK-recapture model
• Pit tagged fish recapture rates
• Separate analysis of YOY vs older fish
• Seasonal but not yearly variation
• Biased low - confounded with emigration
• Growth
• Energy balance, optimal foraging
• Temperature dependencies and allometries from
  literature, gut capacity and BMR from lab fits

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Coastal Growth
Valley Growth
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Coastal Growth Model Comparison with Data
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Life History Predictions - Coast
smolt
mature
wait
smolt
wait
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Life History Predictions - Coast
No residents
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Life History Predictions - Coast
Many age 1 smolts gt age 2 emigrants, a few older
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Coastal Growth - Estuary Effects
Hayes et al TAFS
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Life History Predictions - Coast
Threshold size of 110mm in late December
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Evidence for smolt threshold?
Length lt100 gt100 max p
Scott recap 30 0 98 0.0008
not 237 91
Soquel recap 56 21 230 0.84
not 223 61
GSF recap 7 0 89 0.053
not 81 13
BDG S recap 4 22 197 0.532
not 14 139
ASBRY recap 20 13 153 0.087
not 25 18


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Evidence for smolt threshold?
Length lt100 gt100 max p
Scott recap 30 0 98 0.0008
not 237 91
Soquel recap 56 21 230 0.84
not 223 61
GSF recap 11 0 89 0.026
not 79 13
BDG S recap 21 8 230 0.84
not 120 30
ASBRY recap 24 13 153 0.080
not 24 18


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Life History Predictions - American
mature
smolt
wait

• All smolt as YOY and emigrate age 1
• Threshold size of 150mm in late December
• (higher threshold than coast)

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Predictions - Mokelumne
mature
smolt
wait

• Most smolt as YOY and emigrate age 1
• Potential for slow growers to mature as parr

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Effects of changing environment

• Short term compare new growth vs. old thresholds
  (no response to survival changes)
• Coast much faster growth could yield mature
  parr. Easy to change average age at smolting.

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Effects of changing environment

• Short term compare new growth vs. old thresholds
  (no response to survival changes)
• Coast much faster growth could yield mature
  parr. Easy to change average age at smolting.
• Valley slow growth might yield mature parr.
  Need to preserve good growth environment in late
  summer.

35
Effects of changing environment

• Short term compare new growth vs. old thresholds
  (no response to survival changes)
• Coast much faster growth could yield mature
  parr. Easy to change average age at smolting.
• Valley slow growth might yield mature parr.
  Need to preserve good growth environment in late
  summer.
• Long term
• Both Most sensitive to emigration survival
• Importance of estuaries, passage through delta

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Future directions

• Bet-hedging
• Explicit estuarine state and decisions
• Refine functional relationship between
  temperature, flow, and growth
• Males

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smolting decision window
time of emigration
Decent chance of survival. Extra benefit from
another years growth outweighed by river
mortality, generation time.
Size
Too small to stand much chance of survival
Time
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smolting decision window
time of emigration
Decent chance of survival. Extra benefit from
another years growth outweighed by river
mortality, generation time.
Size
Too small to stand much chance of survival
Time
40
smolting decision window
time of emigration
Decent chance of survival. Extra benefit from
another years growth outweighed by river
mortality, generation time.
Size
Too small to stand much chance of survival
Time
41
coast
valley
Beakes et al. in prep
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