Oncorhynchus Bayesian ANalysis (OBAN)

A Statistical Model of Central Valley Chinook Incorporating Uncertainty

OBAN is a statistical modeling approach that incorporates mortality in all phases of salmon life history, and includes the effects of uncertainty in assessing population status.
The objectives of the project are to:
  1. estimate population vital rates by fitting predictions of the population dynamics model to observed indices of abundance;
  2. evaluate covariates that may explain dynamic vital rates (e.g., thermal mortality affects alevin survival rates in spawning reaches); and
  3. explicitly incorporate uncertainty in the estimation procedure by fitting in a Bayesian framework.

Delta Stewardship Council Objectives

OBAN is funded by the Delta Stewardship Council and was developed by a collaboration of R2 Resource Consultants, Inc., University of Washington, and NOAA Fisheries to meet the following Delta Stewardship Council objectives:

OBAN Models

The Sacramento River is home to four distinct Chinook (Oncorhynchus tshawytscha) stocks: fall, late fall, spring and winter runs. OBAN models are currently in the process of being constructed for two of these stocks: winter run and spring run.

The OBAN model is a user-friendly framework for exploring factors hypothesized to affect Central Valley Chinook population dynamics. For example, much of the variability in winter run abundance can be explained by temperature during egg incubation and indices of harvest.  Other factors that could be addressed include: access to rearing in Yolo Bypass, exports during the outmigration period, striped bass adult abundance indices, and near-shore ocean conditions.

Bioenergetics Model

We will use this model is to give a rough estimate of how temperature-dependent growth rates and survivals from one run of interest (e.g. winter-run) might vary, when there are data from only another run (e.g. fall-run). This will allow us to evaluate the uncertainty surrounding these environmental stressors as they influence growth and survival in the estuarine phase by using these survivals and growth rates as prior distributions to refine our Leslie Matrix model (Task 6). We will also be able to calculate the size and time of ocean entry (SOE and TOE) for the various runs and use these as inputs to Task 4.

Contact Information

The process of model development and refinement is an iterative one; therefore, comments and criticisms of the models and model descriptions are strongly encouraged. Please email comments/criticisms to Dr. Noble Hendrix (nhendrix@r2usa.com).