Evaluating Salmon Rearing Limitations in River Deltas

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North Fork Skagit River Fishtown Bar area.JPG
This effort is linked to Coordinated Investment pilot work

Skagit River System Cooperative in collaboration with NW Fisheries Science Center and regional partners will evaluate how different parts of river deltas provide opportunities for juvenile salmon, allowing planners to determine what sites are likely to provide the most benefits.


  • Project Contract in PRISM
  • Uses 10- 20 years of outmigrant data collected by the Washington Department of Fish and Wildlife (Skagit) and Tulalip Tribes (Snohomish River)and proposed to relate these to measurements of density and size of juvenile Chinook salmon in tidal deltas to derive independent estimates of capacity for each system.
  • Additional system level variation is explained by distributary network connectivity using Skagit models.
  • Examines the influence of habitat types (forested riverine tidal, scrub-shrub, and estuarine emergent marsh) on growth potential through their effects on invertebrate abundance and (because prey vary in energetic value) their composition.
  • We will quantify differences in the juvenile salmon rearing value of different habitat types with bioenergetics models, which estimate the energy an organism can allocate toward growth by incorporating prey consumption, prey energetic value, and metabolic activity as influenced by temperature.
  • Predictions from models can be directly tested using individual habitat-specific growth estimates derived from otolith microstructure.
  • These data have been collected for fish from the Skagit tidal delta, but not synthesized into a bioenergetics model. We propose to complete this task, and collect and analyze existing samples from the Snohomish, Nooksack and Nisqually to run and test the bioenergetics model for each system.
  • The resultant analysis will reveal how local temperature and prey variation in different habitat types can influence growth, and the habitat-specific capacity of these types.
  • These valuations will be applied to existing GIS layers on habitat types and connectivity to determine the system-wide growth opportunities in the two systems.
  • This tool could then be used to prioritize restoration of different habitat types if temperature or prey availability strongly constrains density-dependent growth.
  • In addition, the tool could be used to predict how climate change impacts on the abundance and distribution of habitat types through sea level rise, and local temperature increases in these habitats, will likely impact growth opportunities for juvenile fish.
  • The primary outcomes of this analysis will be:
    1. Assessment of density dependence in two estuaries factoring total habitat availability, habitat conditions, and connectivity
    2. Bioenergetics modeling of habitat-specific growth potential including prey inputs, diet, temperature, and local rearing densities
    3. Empirical testing of bioenergetics model using otolith-based growth increments in each system
    4. Evaluation of the benefits of different planned and hypothetical restoration projects

Related Materials


  • Funded by ESRP program in state FY 2013-15
  • The project expanded from the originally envisioned Skagit and Snohomish deltas to include the Nooksack and Nisqually deltas
  • Supported by NOAA

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