Christopher Tretter, Idaho Department of Lands, ctretter@idl.idaho.gov (Presenter)
Scott Marshall, Idaho Department of Lands, smarshall@idl.idaho.gov
John Gravelle, Pine Orchard, Inc., jag@pineorchard.com


Accurate delineation of the upstream boundary between fish-bearing and non fish-bearing waters is a crucial component of watershed-scale forest use planning and management. Little survey data generally exist to identify the upper limits of fish distribution in forested watersheds, yet the boundary between fish-bearing and non fish-bearing waters has significant management implications related to timber harvest regulations, forest road location and construction methods, and a broader understanding of headwater aquatic ecosystems. These regulatory, economic, and ecological concerns have led to developments in spatial modeling that predict the upstream extent of fish distribution. In 2007 and 2008, upstream fish distribution was examined in 10 watersheds of northern Idaho. Using a logistic regression model developed by the Washington Department of Natural Resources (WDNR), optimization of a physically based predictive approach was tested. Although results varied depending on watershed and subbasin, the total length of stream correctly classified was very similar to results attained in Washington.