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11 <br />6 <br /> with fish monitoring in 1985 at each flow period. Previous data showed that <br /> backwater and eddy habitats were used most frequently during runoff, while pool <br />. <br /> and eddy habitats were used most frequently during the base flow period. For <br /> this analysis, runoff was defined as April 1 - July 31 and base flow as August 1 <br /> - March 31. Backwater and eddy habitats were enumerated and measured from <br />e <br /> RMI 0 - 127 during runoff (May 20-23, 26-30, and June 11). Flows during the <br /> period ranged from 7700-9410 cubic feet per second (cfs) (USGS). During the <br />. spawning period, spawning bar habitat was evaluated by identifying and <br /> enumerating total distance (RMI) of potential spawning sites and determining <br /> gradient through the different spawning reaches. Potential spawning areas were <br /> identified by collection of ripe fish or past radiotelemetry observations <br />. <br /> (Wick et al. 1983, 1985a, and 1985b; Tyus 1984). Spawning habitat was evaluated <br /> from RMI 8-21 on July 20-21 at flows of 1450-1770 cfs (USGS). At baseflow, pool <br /> and eddy habitats were evaluated from RMI 52.5-121 on September 16, October 5-7, <br /> <br />and October 27. Flows during the evaluation ranged from 250 - 619 cfs (USGS). <br />Distance was determined with the aid of a range finder. Depths were determined <br />. with a Lowrance chart recording depth finder or graduated meter stick. During <br />the spawning period, river gradient was determined using a surveying level and <br />stadia rod. <br />. For spring habitat analysis, backwater habitat was divided into Class 1 <br />0 lm in average depth) and Class 2 (0.5 - 1.Om in average depth) categories. <br />Only eddies that exceeded 5 x 5m area and lm maximum depth were measured. <br />. During fall habitat analysis, pool and eddy habitats were divided into Class 1 <br />0 2m maximum depth) and Class 2 (1-2m maximum depth) categories. The basis for <br />class divisions is discussed in greater detail in the model description <br />. (Appendix B). Using the habitat data collected and past fish collection records <br />from 1979-1985 on the Yampa River, a Habitat Suitability Index (HSI) model was <br />a