» 



The use of gastric levage in this study was an accurate 

 method for securing stomach contents of brook and rainbow trout 

 for analysis (Table 8) . The method was slightly less efficient 

 in removing the stomach contents of burbot. Most of the 

 inefficiency, however, occurred early in the sampling season and 

 our efficiency improved as the summer progressed. 



Table 8. Gastric levage efficiency (by volume) and efficiency 

 sample size for brook trout, rainbow trout, and burbot in the 

 upper Big Hole River drainage, June 18 to August 23, 1990. 



Species Efficiency Sample Size 



Brook trout 92% n=5 



Rainbow trout 100% n=l 



Burbot 83% n=4 



Substrate Composition of Spawning Sites 



Mean percentage composition of the substrate at the six 

 spawning sites is shown in Table 9. The substrate is primarily 

 sand and gravel at all of the sites. The greatest amounts of 

 fines (silt and sand particles) occurs at site J (Buffalo Ranch 

 1) . Site J is located at the point where the North Fork of the 

 Big Hole River empties into the main river. On days of average 

 or above average water clarity, large amounts of sand and 

 small-gravel sized sediments were seen moving out of the North 

 Fork and into this spawning site in the main stem. 



21 



