1990 Grayling Spawning Report 



CHARACTERISTICS OF SPAWNING HABITAT 



Visual Characteristics 



Ripe grayling usually were found in riffle areas over gravel 

 which appeared "bright" due to the absence of periphyton and/or 

 silt and sand sized material on the surface of the streambed. 

 These riffle areas of "bright" gravel were often associated with 

 recently created side channels, below beaver dams and irrigation 

 diversion structures, and/or near mouths' of tributaries where 

 alluvial gravel fans had formed. Electrof ishers became relatively 

 efficient at identifying areas where ripe grayling were likely to 

 be captured by the middle of the spawning season. These areas 

 could be characterized as being in areas of hydrologic instability, 

 often in recently cut side channels where a riffle with "bright" 

 gravel was situated near a pool or run, or over recently deposited 

 gravels . 



Measured Characteristics 



Velocity, depth, and substrate composition measurements were 

 taken across eleven sites where ripe grayling were captured. Ripe 

 grayling were captured at depths averaging 2.2 feet with 

 water velocities averaging 1.9 fps at . 6 depth and 1.1 fps at . 1 

 depth (Table 4). Substrate composition at capture sites averaged 

 11% silt, 20% sand, 32% small gravel, 31% large gravel, and 6% 

 cobble (Table 4). Available velocities, depths, and substrate 

 compositions in adjacent areas were also measured. Available 

 velocities averaged 1.5 fps at 0.6 depth and 0.9 fps at 0.1 depth 

 (Table 4). Available depths averaged 1.8 feet. Available 

 substrate composition averaged 14% silt, 23% sand, 32% small 

 gravel, 24% large gravel, and 7% cobble. From these measurements 

 it appears that grayling may select deeper, and possibly, faster 



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