Fig. 1. — Distribution of Etheostoma gracile in the upper Mississippi River valley and the total 

 (inset). The circled dot represents the study area. 



range of the species 



edited by Robeit M. Zevvadski, associate technical edi- 

 tor of the Sui\ey. 



Dr. Hobart M. Smith, Professor of Zoology at the 

 University of Illinois, offered helpful suggestions and 

 read the manuscript. Dr. Bruce B. Collette, U.S. Na- 

 tional Museum, served as special guest reviewer. 



DESCRIPTION OF STUDY AREA 



The area selected for study (the circled dot in Fig. 1 ) 

 is in the vicinity of the Route 37 bridge 1 mile north- 

 east of La Clede, Fayette County, Illinois, a site known 

 to have a large population of slough darters (Fig. 2). 

 The study area is an appro.ximatcly %-niilc stretch 

 of Dismal Creek with overhanging vegetation. It ex- 

 tends from the mouth of a temporary tributary west of 

 the highway bridge to the mouth and lower reaches 

 of a semipermanent tributary east of the bridge. 



Dismal Creek is a medium-sized stream flowing 

 through dissected clay hills on Illinoian glacial till in 

 the Wabash River watershed. It arises in extreme south- 

 eastern Fayette County, flows about 15 miles sfiutheast, 

 and empties into the Little Wabash River in adjacent 

 Clay County near the town of Louisville. 



The creek fluctuates greatly in size, depending on 

 the season. In the spring it consists of a few ]W)ols up 



to 20 feet wide and occasionally more than 6 feet deep, 

 each connected by narrow, fine gravel riffles. In the 

 fall the.se pools are 10-15 feet wide and usually no 

 more than 2-3 feet deep. 



During drought periods the creek is discontinuous, 

 as the water level falls below the level of the riffles and 

 many of the pools stagnate. Some of the pools have 

 sand or clay bottoms; others have bottoms of mud cov- 

 ered with fallen leaves, twigs, and other debris. Because 

 of the variety of bottom ty]X's, the stream has a number 

 of microhabitats. 



There is considerable ])ollulion from the waste of 

 grazing farm animals. The water temperature (in shade) 

 clo.sely ])arallels the air ti-mperatiue. deviating, at least 

 throuijhout the sprins; months, no more than 2 F. 



METHODS 



The study area was visited 23 limes from February 

 14, 1964, to December 12, 1964. Collections were taken 

 at about 2-week intervals in February, March, and 

 April; weekly intervals in May and Juni'; 2-week inter- 

 vals in July and August; and 4-wcek intervals from 

 Sc]jtember to December. The specimens collected for 

 study were distributed as follows: February. 53; March, 

 25; April, 34; May, 6; June, 29; July, 93'; August, .35; 



I 



