GRAYLING SPAWNING REPORT 



Streambed Composition 



The streambed within a known grayling spawning rifflp in 

 the Big Hole River contained 30/1 large gravel (particles between 

 6.0 and 0.5 inches), 507. fine gravel (particles between 0.5 and 

 0.09 inches), and 207. sand and silts (particles less than 0.09 

 inches), while a similar site not used by grayling in the North 

 Fork Big Hole River contained 30%, 407., and 307. of the same size 

 classes, respectively (Figure 7). There were lower percentages 

 of fine material (smaller than 0.25 inches in diameter) in the 

 Big Hole spawning site (307.) versus the North Fork site not used 

 for spawning (437.). There were statistically significant 

 differences between the two sites for the cummulative percentages 

 of material less than 0.374 inche'3 (p < O.02), less than 0.25 

 inch (p < 0.002), less than 0.09 inches (p < 0.004) based on 

 Mann-Whitney tests (Daniels 1973) computed using a STAtGRAPHICS 

 computer package version 2.6 ( STSC 1986). There were no 

 significant differences between cummulative percentages for the 

 other size classes analyzed. 



During the e;-<traction of the sample material we observed 

 that a real difference existed between the ti-jo -3ites. The main 

 stem Big Hole River site (where grayling were spawning) had very 

 little sand and silt material in tha upper one to two inches of 

 the streambed, but did have an abundance of sand and silt below 

 that level. The North Fork Big Hole River site (where no 

 grayling spawning was observed) had abundant sand and silt 

 observed on the surface. 



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