University of Washington

Egg Growth Modeling: Spawned Egg to Emerged Fry

Version 2.1.6 [2025-Jul-17]

The salmon egg growth modeling process begins with egg deposition at the time of spawning and ends with fry emergence from the gravel. Development rate and survival can be modeled by various methods to determine fry emergence from the gravel. Multiple models of egg development rate and survival are available on this webpage. The user can specify the data inputs for river temperature and redd/carcass/adult counts, as well as the model parameters. Default parameters values are from studies referenced therein.

Historical temperatures provided by CDEC. Redd and Carcass data provided by CDFW.

For more information, see the Version Details page, and the References - Notes - Data Disclaimer page.

New Content released July 17, 2025.

Temperature Data
Use SHINY Tool to create temps.

Units:   
Redd Distribution Data (Spawning)


days


diagram SacPAS Egg Growth Model Process
General Instructions:
  1. Make a selection for "Temperature Data" and "Spawning Data".
    Either select from the green-blue lists, or click the radio button to choose the "Input or Upload" method to specify the input data.
  2. Additional options to specific input data have a light gray-blue background. Users can select the appropriate parent radio button to access these options.
  3. In the "Analysis and Results Display" in the pale yellow area, users can choose to generate a query url and control formats of summary results and graphic outputs.
  4. Below the "Analysis and Results Display" area, users can choose among temperature-dependent mortality models, density-dependence models and development-rate models.

Analysis and Results Display

or



    

Additional model controls below.

Option with database sources of Redd Distribution:
See Notes

Model Notes

Additional Model Controls

Temperature-Dependent Mortality (parameters are for °C temperatures)
   M = α ⋅ e β ⋅ Temp
Choose default calibration:



Pre-hatch egg:   α = x 10-  β =
Post-hatch alevin: α = x 10-  β =
   M = α ⋅ max ( Temp − β , 0 )
Choose default calibration:


per °C above critical temperature.
°C.
M = 1 − ( 1 − e − T k L T L ) e − T k U T U   (Jager 2011)
Eggs:   
Alevin:
(Oppenheim 2014)
Threshold (USGS 2018a, Trinity/Klamath model) no longer available.
See References-Notes.
line plot Comparison of survival models
Density-Dependent Mortality
For options below: S0 = Base survival (Sacramento 0.347; Trinity 0.687)
M = 1 − ( S 0 + μ 1 ⋅ N )
μ1 = Density-dependent survival per redd
M = S 0 / ( 1 + N / K )
K = Carrying capacity of redds.
Egg Development model
: Target ATUs °C days
(= 1724 °F days)
: Egg mass mg. (Range: 100 - 400)
Days = 1 / e10.404 - 2.043*log(T°C + 7.575)
Days = 1 / e6.872 - log(T°C + 0.332)
Hatching: °C days
(= 751 °F days)

(USGS,Trinity: 3000; Oppenheim,2014: 4925)
Comparison of egg growth models