YCT Multi-state Assessment February 10, 2003 



Within the assessment area two forms of YCT have been identified, but have not been 

 differentiated genetically: 1. a large-spotted form that was dominant in most of the upper 

 Yellowstone River basin and the lower Snake River basin from Palisades Reservoir downstream 

 to Shoshone Falls; and 2. a fine-spotted form that was dominant in portions of four watersheds in 

 the upper Snake River basin. We assessed the status of YCT from several perspectives including 

 a broad overview of the entire assessment area, a review of the relationship of the large and fine- 

 spotted forms, and a brief summary of specific conservation population status information. 



Methods 



We developed a standardized approach and consistent protocols that were used by all 

 participants who gathered together in localized workshops (Appendices A and B). Information 

 was gathered by the participants at each workshop and entered into a geographic information 

 system (GIS) and relational databases. Many different sources of information were used in this 

 assessment, but consistency was maintained by having one or two individuals attend all 

 workshops and facilitate data entry and answer questions raised by workshop participants. Since 

 this assessment relied upon exisfing information, sampling was not random, and in many cases 

 not independent; therefore, there are undoubtedly biases associated with these data. We discuss 

 the possible consequences of these biases when we present the results. We have attempted to 

 qualify and disclose the nature of these data through citations and by having the people that 

 provided infonnation identify the primary source of informafion (e.g. primarily based on 

 professional judgment, based on a minimum level of field information or linked to extensive 

 study). Sources of information were also referenced (e.g. field notes, agency files, reports or 

 publications) 



Geographic Information System 



We used the 4th code hydrologic unit code (8-digit EPA designation) as the primary unit for 

 organizing data input from the fisheries professionals. We also summarized historical range and 

 current status information using this stratification. The U.S. Geological Survey (USGS) created 

 the hierarchical hydrologic unit code (HUC) system for the United States in the 1970's. This 

 system divides the country into 21 Regions, 222 Sub-regions, 352 Accounting Units, and 2,149 

 Cataloging units based on surface hydrologic features. The smallest HUC used in this study was 

 approximately 448,000 acres (Hydrologic Units Maps of the Conterminous United States. 

 Reston, VA. United States Geological Survey. August 2002. http://water.usgs.gov/GlS/metadata/ 

 usgswrd/huc250k.html). 



We chose to use stream and river distance as measures of YCT occupancy, both for suspected 

 histoncal and known currently occupied habitats. Consequently, lake occupancy was not 

 directly assessed; however, all lakes that were located within the stream network were included, 

 as length values, if the stream network bisected the lake. Our assessment used GIS tools in 

 Arcview 3.2 along with extensions created for this project (Steve Carson, Montana Fish Wildlife 

 and Parks, Helena, Montana modified "ddeaccess.avx" and "routetool.avx" extensions that are 

 available from ESRl at http://arcscripts.esri.com) as well as a relational database within 

 Microsoft Access (modeled after the Montana Fish Wildlife and Parks' MFISH database that can 



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