YCT Multi-state Assessment 



February 10,2003 



" For example, if you have a 60 km length of connected habitat that is very complex and high 

 quality it would receive a rank of "1" (original rank of "2" due to length decreased to "1" 

 because of high quality habitat). 



Two other variables that Rieman et al. (1993) suggested evaluating were population replication 

 and synchrony between populations. At this time we believe that these variables are somewhat 

 less important because the majority of YCT populations occupy dispersed habitats across the 

 range. It will likely be important to assess the variables in the future as conservation actions are 

 taken to restore populations. Subsequent assessment of these variable could best be ranked using 

 spatial queries within a GIS application after all other data is entered in a spatially explicit GIS 

 database. 



The ad hoc committee also discussed whether it was important to acknowledge the source/sink 

 relationships that may exist between headwater YCT population and those YCT populations that 

 might exist lower in a drainage, especially where barriers to upstream movement might exist. 

 While headwater YCT populations that are isolated by impassible barriers to upstream fish 

 movement and thus could not be re-founded if they went extinct, these headwater populations 

 may be important sources for re-founding and augmenting lower populations. The ad hoc 

 committee felt it was important to capture in a database where these types of relationships 

 between populations occur. This will be handled by a simple identifier check indicating that a 

 given population operates as a source. Any downstream population would then automatically 

 become a "sink" recipient. 



Page - 58 



