350 



Illinois Natural History Survey Bulletin 



Vol. 28, Art. 2 



the disposal plant to its junction with the 

 East jiranch; and Section 3, the stream 

 (actually the Salt Fork) from the junc- 

 tion of the Kast and West branches down- 

 stream for a distance of 4 miles. 



Section 1 presumably was relatively 

 free of pollution when Forbes ^' Richard- 

 son collected at least 23 species there. In 

 1928. Thompson ^' Hunt described this 

 section as clean and relatively free of pol- 

 lution ; they reported 20 species in the 

 area. Since 1928, however, waste water 

 from the northward expansion of Urbana 

 and from several industrial plants has 



polluted this portion of the stream. In 

 1959, only 15 species of fish were found 

 there, table 24. 



Examples of species that disappeared 

 early from this section were the spotted 

 sucker, golden redhorse, suckermouth min- 

 now, black bullhead, black crappie, and 

 two species of darters. Species that disap- 

 peared in recent years (as pollution in- 

 creased) were the grass pickerel, tadpole 

 madtom, brook silverside, and bluegill. 

 The most notable examples of species ap- 

 pearing in the section for the first time 

 after 1900 were the carp, common shiner, 



Table 25. — Number of fish per 100 square yards and number of species taken at sampling 

 stations above and below sewage disposal plant on the West Branch of the Salt Fork by Thomp- 

 son & Hunt and by Larimore & Smith. Presence of a species in very small numbers is indi- 

 cated by +. 



Table 26. — Number and weight (pounds) of fish per 100 square yards, and average number 

 of species per station, collected in 1959 at various stations in two streams, one polluted (part of 

 West Branch and Salt Fork) and one unpolluted (part of East Branch and Salt Fork). Each 

 station is located with reference to stream size. 



•Classification used by Thompson & Hunt (1930). In our work, we considered the numerals as designating size 

 limits, so that a stream classified as size 4-8 had a drainage area of more than 4 and not more than 8 square miles. 



