What is Variability ?

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What is Variability ?

• Change with location or through time in the
  capacity of a freshwater system to support salmon
  
• Spatial Variation
• Natural variability in conditions
• Variable intensity of human impacts
• Interaction between watershed condition and human
  effects
• Temporal Variation
• Interannual variation in weather
• Catastrophic disturbance
• Cyclical or unidirectional changes in climate
• Spatial-Temporal segregation is artificial -
  temporal changes in condition are a major factor
  in creating spatial variation

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Variability in Annual Coho Production
Bisson and Bilby 1998
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(No Transcript)
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Factors Associated with Coho Salmon
Abundance Snohomish Basin
Pess et al. 2002
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Temporal Variation

• Year-to-year variation in flow, temperature etc.
• Life history specific effects
• Examples
• Winter floods - decreased egg-fry survival
• Spring high flows - increase fry emigration
• Summer drought - decreased summer fry survival
  and growth
• Autumn high flow - enhanced access to spawning
  habitat
• Long-term variations
• Recovery from disturbance
• Climatic changes (PDO, global warming)

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Winter Flow and Population Performance
Unpublished data, Beamer and Pess (with apologies)
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Temporal Changes in Salmonid Production
E
high
C
F
A
Productivity
D
B
low
Time Since Disturbance (yrs)
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Temporal Changes in Salmonid Diversity
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Coho Salmon Productivity after the Eruption of
Mt. St. Helens
Juvenile Coho Production (mg/m2/d)
Year
Bisson et al. 1997
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Disturbed Site
Density (fish/m2)
Buffered Site
Density (fish/m2)
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Thrash Creek Biomass 3.00 g/m2
Beaver Creek Biomass 3.28 g/m2
5 Years after Disturbance
60 Years after Disturbance
Hicks et al. 1991
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Patterns in Stream Productivity
Low
Medium
High
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Questions

• 1) How can variability be incorporated into
  predictions of salmon capacity, growth and
  productivity?
• 2) What are the largest sources of uncertainty in
  predicting salmon response to freshwater habitat
  conditions?
• 3) What alternative scenarios of current and
  future conditions should the model strive to
  explore?
• 4) At what spatial scale should wood abundance be
  characterized to be most meaningful to salmon?
• 5) What habitat is most important freshwater,
  estuarine or marine?
• 6) What nutrient contribution from salmon
  carcasses is required to achieve maximum smolt
  production? How can this aspect of habitat be
  incorporated into the model?

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Q 12 Incorporating Variability

• Spatially explicit predictions - recognize that
  not all places are equal and a few locations can
  support the majority of all freshwater production
• Most influential life history stage varies
  interannually build in hydrological
  fluctuations (flood, drought) and adjust the
  survival of the affected life history stage
  accordingly
• Major disturbance events cause predictable
  patterns of change in productivity
• Recognize that the performance of the fish at one
  stage influences survival later in life higher
  spring-summer growth rates increase overwinter
  survival larger smolt size increases marine
  survival
• Failure to include factors other than physical
  habitat in relationships to salmon production a
  major source of uncertainty in current modeling
  approaches

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What is Salmon Habitat?
.

• Combination of physical, chemical and biological
  attributes
• Physical
• Access
• Sediment levels, channel morphology
• Chemical
• Water temperature
• Contaminants
• Nutrient availability
• Biological
• Primary and secondary production
• Competition and predation

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Q 3 Habitat Scenarios

• High Quality Salmon Habitat
• Low Elevation
• Low Gradient Channels
• Diversity of Riparian and Channel Conditions
• Low-level of Human Influence
• People and Salmon Occupy Similar Habitats

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Urbanization Effects on Fish Communities
Coho
0
20
40
60
Urbanization ( Impervious Area)
of fish community composed of coho salmon with
increasing levels of urbanization for 11
watersheds in King County, Washington. From
Lucchetti and Furstenberg 1993.
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Population in King, Pierce and Snohomish Counties
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Alternative Growth Scenarios

• Future development will disproportionately impact
  sites with high productive potential
• Evaluate effect of different patterns of
  development
• Concentrate new growth in already populated areas
• Unrestricted development focused on low relief,
  low elevation locations
• Current zoning plans

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Q 4 Appropriate Scale for Wood

• Wood-fish relationships are tenuous
• Relates to failure to consider other aspects of
  habitat
• Best relationships with winter abundance of coho
  salmon
• Ideally, wood abundance and distribution at the
  watershed scale
• Response to wood in a reach with a mix of
  conditions typically associated with high
  production will be greater than in a reach with
  poorer underlying condition for the fish

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Q 5 Which Habitat is Most Important

• Answer - All
• Relative importance vary with conditions
• Poor freshwater habitat and extreme weather
  conditions sufficient mortality may occur prior
  to smolting to preclude adjustments later
• More benign freshwater conditions and enough
  smolts may be produced to exceed estuarine
  capacity
• Recent experience on the Columbia indicates the
  significance of early marine rearing condition
• All habitats are connected
• Freshwater conditions can influence smolt size
  and number - affects survival in the estuary and
  ocean
• Estuarine conditions can also effect size and
  number of fish entering the ocean
• Ocean conditions dictate adult growth and
  survival, influences the number of fish returning
  and delivering nutrients to freshwater -
  influences freshwater habitat condition

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Q 6 Nutrient Contribution from Spawning Salmon
Average Weight (g)
salmon carcasses present
Bilby et al. 1998
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Sample Locations
Clallam
Hoko
Skagit
Dickey
Soleduck

Skykomish
Bogachiel
Snoqualmie
Hoh
Deschutes
Chehalis
Willapa
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Index of 15N Enrichment
Carcass Availability (kg/m2)
Bilby et al. 2001
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Approximate 15N Saturation Level
Bilby et al. 2001