Importance of Habitat in salmon declines and recovery

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Importance of Habitat in salmon declines and
recovery

• Ray HilbornSchool of Aquatic and Fishery
  SciencesUW

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What is wrong with salmon?The 4-Hs

• Harvest
• We take too many
• Habitat
• We degrade their streams
• Hydroelectric
• We block passage, turn rivers into lakes
• Hatcheries
• We try to mitigate for habitat loss by
  artificial production

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Structure of talk

• Trends in abundance
• How bad is the problem
• Ocean conditions the BIG driver
• Hydroelectric
• Harvest
• Hatcheries
• Habitat

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Myth IWe are running out of wild salmon
The truth there are nearly as many wild
salmon in western North America now as any time
since Europeans arrived
But this due primarily to Alaska, and in the
Lower 48 many stocks are extinct and most are
well below historical levels
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Bristol Bay wild sockeye
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Puget Sound Coho Wild Returns
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Chinook salmon past Bonneville Dam
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Myth IIThe ocean is big, unlimited and salmon
abundance is driven by freshwater and habitat
The truth most large scale variation in
salmon abundance is driven by ocean changes
But this only means it is harder to detect
anthropogenic impacts
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Historical sockeye population dynamics
Lake Nerka, SW Alaska
Schindler and Leavitt (2001)
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fishery catch
escapement
Schindler and Leavitt (2001)
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Effects of sockeye population on phytoplankton
production
Sockeye (1000s/km2)
Sockeye density
Algal pigments in lake sediments
Schindler and Leavitt (2001)
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Survival rate by Realm
Fallchinook
Springchinook
Coho
Arctic
SE Alaska
Coastal BC
Georgia Strait
Puget Sound
Coastal Washington
Columbia Basin
Coastal Oregon
California
Avg survival rate
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Coho survival rate by Domain
Survivalrate
Release year
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Fall chinook survival rate by Domain
Survivalrate
Release year
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Spring chinook survival rate by Domain
Survivalrate
Release year
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Coho survivalSST regression
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Coho survivalSST regression (incl. resid)
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Gulf of Alaska Small set of structuring
variables operating at different speeds - Whammo!
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Myth IIIThe decline of NW salmon is due to dams
The truth systems without dams have had
similar trends
But clearly dams are not good for salmon and
are part of the problem
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Chinook survival by river segment
Fall chinook
Spring chinook
Fall chinook
100
100
10
10
1
1
Survival rate
0.1
0.1
0.01
0.01
0.001
0.001
B W A S
B W A S
L T U
Columbia
Columbia
Fraser
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Chinook survival in Columbia Basin
Spring chinook
Fall chinook
Survival rate
Survival rate
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Chinook survival in Fraser Basin
Fall chinook
Survival rate
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Myth IVHatcheries are necessary to mitigate for
lost of habitat and over-harvest
The truth hatcheries have strong negative
impacts on wild salmon
But if we eliminate hatcheries we might have no
salmon left in some places
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Hatcheries

• The basic assumptions
• Freshwater habitat is limiting
• Egg to smolt survival in the wild is about 5
• Hatcheries can usually obtain 80 egg to smolt
  survival
• Release smolts ready to go to sea they dont
  need any freshwater habitat

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Why hatcheries were built

• To compensate for over-harvesting
• To compensate for habitat destruction
• To mitigate for dam impacts
• To buffer natural variation
• To provide extra fish for harvest
• To conserve threatened stocks

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Did Hatcheries Work

• We have over 300 hatcheries in the Pacific
  Northwest
• If hatcheries were the solution, we wouldnt
  have a problem!
• Much disagreement, what would have happened
  without hatcheries

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Concerns about hatcheries

• Generate over-harvesting on wild fish in mixed
  stock fisheries
• Compete with wild fish in freshwater and ocean
• Introduce and exacerbate diseases
• Genetically degrade wild fish by domestication
  and hybridization
• Provide an excuse to allow habitat loss

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Pink salmon hatcheries in Prince William Sound

• Largest hatchery program in North America
• 600 million fish stocked each year
• Competing hypotheses re marine fish stocking
• stocking augments wild production
• stocking replaces wild production
• We have BACI !!!!!!

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Prince William Sound salmon production
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Total return
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Wild fish production
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Myth VThe collapse of salmon in the late 80s and
90s is due to habitat changes
The truth habitat has not changed that much
But habitat is definitely declining
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Few (if any) attempts to integrate all factors in
combined analysis

• We have detailed harvest models
• We have no hatchery impact models in use
• Changes in ocean conditions are being better
  understood but not used in evaluating recovery
  plans
• A number of habitat models, EDT the most used

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Framework for impact of habitat

• Multi-stage life history model from Moussalli
  and Hilborn 1986
• each life history stage as a Beverton-Holt curve
  with a productivity (initial slope or survival)
  and a capacity
• Key question is how to relate habitat to
  productivity and capacity

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Sharma coho carrying capacity
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Key Model ComponentsSHIRAZ

• Spatially explicit reaches or estuarine areas
• Life stages as many as you want
• Stocks may be life histories, wild/hatchery etc
• Capacity and productivity any life history
• Habitat characteristics by reach
• Stochastic factors (flows, ocean survival etc)
• Functional relationships between habitat
  characteristics and stochastic factors and
  productivity and capacity

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Reach Characteristics

• Passage
• Square meters spawning gravel
• Distance
• Square meters rearing habitat
• Percent fines in gravel
• Watershed area by reach
• Percent impervious by reach
• Temperature, DO etc.

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Functional relationships

• Spawning gravel and egg capacity
• fines in gravel and egg to fry survival
• Up the the user to define what you want to use
• Will ultimately build a library of functional
  relationships much like EDT
• But the user will decide which ones to use from
  the library

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General model framework

• Read in the data
• reach-specific habitat
• hatchery input
• Functional relationships
• Hatchery practice
• Harvest and ocean conditions specification
• habitat interventions
• Loop over time
• Calculate the change in habitat
• Calculate the change in population size
• End the loop

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Habitat Changes

• Annual habitat change habitat degradation
• Habitat change due to a 1-time event habitat
  restoration

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Hatchery Influence

• Affect wild fish through competition
• Interbreeding can cause domestication of wild
  fish, and reduced survival

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Functional RelationshipsMark I version

• Spawner capacity depends on gravel area
• Egg survival as a function of fines
• Fry survival as a function of percent impervious
  and rearing area

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Spawners to Egg

• capacity depends on gravel area
• productivity depends on age specific fecundity
  and age distribution of spawners

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Eggs to Fry

• capacity is unlimited
• productivity depends upon fines

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Fry to Smolt

• capacity determined by rearing area
• productivity determined by impervious

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Other outstanding issuesBeyond current efforts

• Allow for parameter uncertainty
• Formalize reality checks
• Potentially imbed the above in formal Bayesian
  framework

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Current status

• Muckelshoot tribe using to meet TRT requirements
  for a rebuilding plan Green River chinook well
  developed, White and Lake Washington just
  beginning
• Joint work with NMFS and Mark Sheuerell to
  interface SHIRAZ with PRISM dynamic hydrology
  models

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Essential Fish HabitatSHIRAZ provides a format

• To calculate the sensitivity of population size
  to each habitat indicator in each area
• This allows a quantitative ranking of the
  importance of different habitat characteristics
  and sites
• This ranking can be used to define essential,
  much like NMFS defines overfishing

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Summary I

• Current work in evaluating natural and
  anthropogenic impacts on salmon suffer from lack
  of unified modelling framework
• SHIRAZ can serve as an initial general model
  structure for cost benefit analysis, policy
  evaluation, and parameter estimation

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Summary II

• The Ocean, and the four Hs are all important
• We need to identify where time, effort and money
  will be best spent in salmon restoration
• This will require a new generation of models,
  data collection and analysis