Dissolved Oxygen Depletion in the Stockton Deep Water Ship Channel: Biological and Ecological Effects Conceptual Model

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How to Use This Model

The Biological and Ecological Effects Conceptual Model describes the:

  • primary drivers (shown in light blue) and secondary drivers (shown in magenta) that determine the exposure of fish to low DO episodes and that make the fish more susceptible to the effects once they are exposed, and
  • adverse effects of exposure to low DO conditions on eight fish species.

The overall structure of the biological/ecological model is presented in the diagram below.

Biological and ecological effects model

Primary Drivers

The following diagram is presented on the Biological and Ecological Effects Model Main Page. The diagram below is not functional, but clicking on one of the primary driver boxes on the Main Page graphic takes you to a page with a graphic depicting the secondary drivers that influence the primary driver. This graphic is followed by a general discussion of the relationships between the secondary drivers and primary driver, and descriptions of linkages that may exist amongst the secondary drivers.

Biological Effects Model

Secondary Drivers

Clicking on a secondary driver box on the primary driver graphic takes you to a detailed discussion of the linkage between that secondary driver and the primary driver. The text begins with a general discussion of how the secondary driver influences the primary driver (e.g., how exposure to toxicants influences the susceptibility of fish to low DO conditions).

Following this general text is text specific to eight fish species: steelhead, Chinook salmon, delta smelt, longfin smelt, Sacramento splittail, white sturgeon, green sturgeon, and striped bass. This species-specific text describes the:

  • hypothesis or hypotheses underlying the relationship;
  • data indicating the strength of this linkage (how much influence the secondary driver exerts over the primary driver);
  • level of scientific certainty associated with this linkage (how well it is understood and how its influence may vary over time or geography);
  • known mathematical relationships between the secondary and primary drivers, including whether there are critical thresholds; and
  • sources of the secondary driver in the reach. Where alternative hypotheses exist, each is presented, and the sources of data supporting each are listed.

Adverse Effects

Clicking on Adverse Effects of Low Dissolved Oxygen on Fish (dark blue box on the Biological and Ecological Model Main Page) takes you to text providing an overview of the effects of exposure to low DO concentrations on fish and the general mechanisms involved.

The diagram on the Adverse Effects page allows you to navigate to detailed discussions of each of seven adverse effects (e.g., direct mortality, reduced growth, altered behavior). These detailed discussions begin with a general discussion of the adverse effect, followed by text specific to each of the eight fish species. Navigation tools in this text allow you to move sideways across the model to see other text related to specific fish species.


Several tools are included in this model to help make it easier to understand the information presented and to facilitate access to information used in this model.

  • Terminology—lists many of the technical terms used in this model along with brief definitions. In the text of the model, you can click on words colored purple to read the definition for that word or click on Terminology on the navigation bar.
  • Acronyms—lists the acronyms used in the model and their definitions.
  • References Cited—lists the references used in the model. When available, PDFs of referenced documents are provided, or a link to a document is provided.
  • Download Text—Links to downloadable PDFs of text will be provided later.

Links to Other Resources

Links are provide to other websites or information related to DO in the DWSC.