567 



Table III 



Indicating the relative resistance of the more common species of fishes to ie 

 taken i7i the waters of Northern Illinois, together with data as to the best type 

 of ecological environment for each species. In column 2 the resistance of the least 

 resistant species is arbitrarily taken to he unity. 



Lepoi7iis cyanellus 



(Blue-spotted sunfish) 

 Ameiurus melas 



(Black bullhead) 



15.0 



45.0 



Pools in creeks. Often with mud bottom. 



Ponds; pools in small creeks. 

 Mud bottom among vegetation. 



While in Table III only eighteen species of fishes are listed, the 

 comparative resistance of other species may be estimated by compar- 

 ing their resistance with that of some one of the listed species. By 



