YCT Multi-state Assessment February 10, 2003 



unsuitable based primarily on thermal regime, stream channel gradient, and minimal stream flow 

 (Appendix A). In a few cases entire 4th code HUC's were excluded. Information sources that 

 supported inclusion or exclusion of stream segments as historically occupied were noted. 

 Important information sources included, historical journal entries, scientific reports, and 

 evidence of basin transfers by headwater stream captures. Current occupancy of streams was 

 also evaluated as a possible rationale for inclusion. All stream and river habitat was included 

 within the historical range unless explicitly excluded by the fishery professionals. Our 

 delineation of historical range refines previous assessments of historical range. The amount of 

 historical range we estimated was then used as the baseline for comparison to the current status. 



Barriers to Fish Movement 



Since barriers to upstream fish movement have important implications for both historical range 

 and current status, known barriers believed to significantly affect distribution of YCT were 

 located and identified. Geological (i.e. bedrock waterfalls, naturally dry channel segments, etc.) 

 and anthropogenic barriers were located and classified. Geological barriers were considered 

 when potentially excluding lotic habitats fi'om the historical range. Anthropogenic barriers were 

 considered when assessing current distributions and various risks to conservation populations. 

 Only barriers of believed significance were included; however, much of the area had not been 

 surveyed for barriers. Significance of barriers as they related to risk and conservation of YCT 

 was identified (Appendix A). 



Current distribution 



For the purposes of this assessment, all stream segments currently occupied by YCT within their 

 historical range were included. Stream segments occupied by YCT outside historical range were 

 not included. Stream segments where YCT populations were supported or maintained by 

 stocking were not included in current distribution; however, stream segments that may have been 

 stocked with YCT in the past, but currently were maintained exclusively by natural reproduction 

 were included. All waters that supported YCT and appeared on the LLID hydrography layer, 

 regardless of level of introgression, were included. However, the genetic status of YCT within 

 each stream segment was classified (see below). In addition to genetic status, biologists ranked 

 the abundance of YCT inhabifing each stream segment. Additional notations for each occupied 

 segment included: a determination of which YCT form (i.e. large-spotted, fine-spotted or both) 

 was present; whether competing species (principally non-native salmonids) were present; 

 identification of restoration or conservafion activities implemented within each occupied 

 segment; and identification of land uses and fish management activities believed to be 

 influencing YCT in the occupied segments. These results were summarized by length of habitat 

 occupied and not by number of stream segments occupied. Number of stream segments was not 

 a meaningful measure because this number does not equate to number of populations and lengths 

 of stream segments varied widely. The stream segment information was aggregated within the 

 "conservation population" assessment (see below). 



Genetic Status 



Six classes idenfifying genefic status for stream segments were applied (Table 1). Four classes 

 were used for those stream segments that had been genetically tested and two classes for those 



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