Bull Trout Proposed Critical Habitat Justification

The U.S. Fish & Wildlife Service (Service) has prepared this document to support the rationale for why bull trout habitats are essential for the conservation of the species and therefore should be proposed as critical habitat and to document the basis for identifying habitat occupancy by bull trout.

We have organized the document by six draft Recovery Units (RUs), 32 Critical Habitat Units (CHUs), and 99 Critical Habitat Subunits (CHSUs) (see text below for more detail).

Rationale for why habitat is essential may be applied across an entire watershed, a portion of a watershed, or an individual stream reach or water body segment, depending on the refinement and quality of available data. Similarly, scientific observations of bull trout occupancy may be documented only broadly within a watershed or specifically within a stream reach, depending on available data.

The text portion of this document captures a broader rationale for why habitat is essential at the level of the 32 CHUs and 99 CHSUs. Appendix 1 captures rationale for why each of the 118 core areas is or is not essential. Appendix 2 documents occupancy as specifically as possible for each of more than 3,500 water body segments and, if available, any specific rationale for why that segment is essential. However, in the majority of cases, there is no stream-specific rationale and the reader is referred back to the text for the entire CHSU. Also, the same citation of occupancy may be frequently repeated for individual stream reaches if that is the only citation that provides documentation across a broad area.