IttttodciCtOM 



PURPOSE 



Objectives of this research task were to gain insight into the environmental 

 requirements of the dominant macroinvertebrate genera and species of the 

 Yellowstone River and to describe the distribution of macroinvertebrates in 

 the Yellowstone and Tonoue rivers. 



SCOPE 



Water velocity and depth were chosen as the independent variables that 

 would be examined. Since current affects invertebrate distribution in several 

 ways, e.g., distribution of food and size of substratum, and because current 

 and discharge are closely interrelated, studies of the effects of current on 

 invertebrate distribution are meaningful and permit predictions about changes 

 in invertebrate communities occurring because of altered flows. Because of 

 the gently sloping morphology of the river channel, depth is also important; 

 both current velocity and depth are functions of discharge. 



Species diversity and river zonation analyses were made in an attempt 



to understand distributional patterns of invertebrates, provide baseline 



data, and record differences and similarities among populations at different 

 sampling stations. 



STUDY AREA 



Almost all of the length of the Yellowstone River outside of Yellowstone 

 Park was included in the study. Of the 20 invertebrate samplinq stations 

 employed in the study (figure 1), the uppermost, at Corwin Springs, is only 

 about seven river miles (11 km) below the park boundary, and the lowest, at 

 Cartwright, N.D., only about nine river miles (14 km) above the mouth of the 

 river. These stations are shown on a longitudinal profile of the river in 

 figure 2. 



The Tongue River also was extensively studied since the macroinvertebrate 

 fauna there influence the fauna of the lower Yellowstone River. Figures 3 

 and 4 show sampling stations employed on the Tongue River. 



Figures 5 through 14 illustrate selected samDling station locations and 

 characteristic views of the upper and lower Yellowstone River. 



