Species and habitat rules

 
EDT is a system for rating the quality and quantity of stream habitat for a particular fish—or focal species—such as coho or chinook salmon. The measure of habitat value is the biological productivity and carrying capacity of the stream for the focal species as a result of habitat conditions.

Starting with a set of Environmental Attributes, the habitat quality is rated using a set of rules that relates conditions, such as water temperature, to the survival of a life stage of the focal species. The rules are developed by consulting with scientific experts on the habitat needs of the focal species and by referring to the scientific literature. EDT contains rules that describe these relationships for each Environmental Attribute (e.g., flow, temperature, sediment) for each life stage, for several fish species.

The quantity of habitat is assessed as the total area of different Stream Unit Types in a reach, weighted by their relative usage by life stage.

To assess the habitat in a stream for a particular focal species, then, requires a set of biological rules for that species. Rules for several anadromous salmonid species have been developed and have been successfully applied to many streams in Puget Sound and the Columbia River Basin. Rules for resident salmonid fishes are under development and should be available later this year—including cutthroat trout (coastal and interior), resident rainbow (coastal and interior), and bulltrout. Rules for sturgeon may be developed as well. The availability and status of EDT habitat rating rules are listed below.

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