354 



Illinois Natural History Survey Bulletin 



Vol. 28, Art. 2 



also were found. The proportion of the 

 fish population killed b\ this pollutant was 

 not known. The dead fish picked up and 

 examined represented most of the species 

 previousl\' taken in our collections. In 

 spite of the recurrinj^ kills, the disappear- 

 ance of only one species is attributed to 

 this pollution. A minnow {Notropis 

 amnis), taken at three stations in the 

 Sangamon near Fisher by Thompson & 

 Hunt, seemingly no longer occurs in the 

 county. 



On the upper Kaskaskia, severe pollu- 

 tion introduced at a point just south of 

 Champaign County near Ficklin has pro- 

 duced chronic to.xic conditions and fre- 

 quent fish kills. The Ficklin pollution 

 probably blocks the upstream movements 

 of certain species and thus influences the 

 composition of the populations within 

 Champaign County. 



The East Branch has had several fish 

 kills in recent years other than those 

 caused by domestic pollution from Ran- 

 toul and Chanute Air Force Base. One 

 such kill was said to have been caused 

 by the accidental release of a large vol- 

 ume of gasoline into the stream. Another 

 kill resulted from discharge into the 

 stream of solutions used for cleaning air- 

 craft. 



On the West Branch, an occasional 

 dead fish can be found, although so few 

 fish occur in the area below the disposal 

 plant that even if all were killed there 

 would not be a noticeable number of dead 

 individuals along the banks. Probably the 

 fish found dead were individuals that 

 moved into this area when water condi- 

 tions were temporarily tolerable and were 

 killed as conditions again became lethal. 



In the lower Salt Fork, fish kills fre- 

 quently have occurred below St. Joseph. 

 These probably have been the result of 

 overenrichment of the waters, where near- 

 pollution conditions are usually present. 

 Summer fish kills seem to be associated 

 with periods of very low water levels and 

 high temperatures; during such periods 

 septic conditions develop. Often in the 

 wintertime, blooms of green plants and 

 animals develop that cause the death of 

 fish over a long stretch of the river. Very 

 heavy algal blooms developed during Feb- 

 ruary and March of 1954. An abnormally 

 low amount of suspended silt was in the 



water when there developed a tremendous 

 green bloom composed mainly of Euglena 

 sp. (similar to E. sangiiinea) and a dia- 

 tom, Hantzschia mtiphioxus (identification 

 by Dr. P. C. Silva, then Associate Pro- 

 fessor of Botany, University of Illinois). 

 The organisms settled to the bottom of 

 the stream each day after dark and 

 blanketed the bottom materials. Many fish 

 were seen gasping along the shoreline of 

 the river and in small tributary water 

 sources. Dead fish could be seen all along 

 the river from St. Joseph as far down- 

 stream as Fairmount in Vermilion Coun- 

 ts These water conditions not only killed 

 many fish but caused the flesh of surviving 

 fish to be unpalatable. 



Ingression Into Polluted Waters 



During the spring and early summer of 

 1960, we made a series of seine hauls at 

 the West Branch stations sampled the 

 previous September. These seine hauls in- 

 dicated a certain amount of ingression of 

 fishes into polluted water, table 27. The 

 several species taken below the disposal 

 plant were represented by very few indi- 

 viduals. The creek chub, bluntnose min- 

 now, redfin shiner, and golden shiner 

 were the species most frequently taken in 

 these collections. 



Reinvasion of a stream area by species 

 once present is usually very rapid (Lari- 

 more, Childers, & Heckrotte 1960:269) ; 

 if chemical conditions below the disposal 

 plant were made suitable for the existence 

 of fish, the population would quickly build 

 up to what might be expected in streams 

 of similar size. 



Specific Tolerance to Pollution 



The following species were most fre- 

 quently found in the polluted water areas 

 sampled in 1959: creek chub, carp, silver- 

 jaw minnow, bluntnose minnow, redfin 

 shiner, golden shiner, stoneroller, green 

 sunfish, sand shiner, common shiner, spot- 

 fin shiner, white sucker, creek chubsucker, 

 topminnow, Johnny darter, and hornyhead 

 chub. The finding of a particular species 

 in a polluted area did not necessarily' mean 

 that this species was more pollution-tol- 

 erant than other species. Species found in 

 a polluted area may have been unusually 

 vagile, moving into the area during pe- 

 riods of improved water conditions; equal- 



