338 



Illinois N.atur.al History Survey Bulletin 



Vol. 28, Art. 2 



Table 11. — Dejiree of association between four species of fish in the Sangamon drainage. 

 Correlation coefficient (r) of 0.438 is significant at the 0.02 level. 



Table 12.— Degree of association between four species of fish in the Middle Fork drainage. 

 Correlation coefficient (r) of 0.934 is significant at the 0.02 level. 



Notropis chrysocephalus — Erimy- 

 zon ohlou^iis. — These species formed 

 one of the least expected associations ob- 

 served among Champaign County fishes, 

 occurring in a significant (P 0.02 or 

 less) association in three of five drainage 

 systems, fig. 12. In the Sangamon drain- 

 age they were closely associated with the 

 two species previously discussed, table 11. 

 In the Middle Fork drainage, however, 

 they formed a strong association with 

 Phenacohius niirahilis and Catostomus 

 cornniersoiii, talile 12. 



Catostomus commersoni — Phena- 

 cobius mirabilis. — These two species 

 occurred in significant associations (P 

 0.02 or less) in three of the five Cham- 

 paign County drainages considered, as 

 well as in the county-wide analysis. They 



were significantly associated with Erimy- 

 zon obloncjus and Notropis chrysocephalus 

 in the Middle Fork drainage, table 12. 

 Both species were closely associated with 

 Hybopsis hicjuttata in the Salt Fork drain- 

 age, fig. 12. 



Miscellaneous Associations. — 

 Several species showed different associ- 

 ations in different stream systems; for 

 example, Notropis umbratilis was signifi- 

 cantly (P 0.02 or less) associated 

 with such species as Hypentelium nigri- 

 cans, Notemigonus crysoleucas, Notropis 

 chrysocephalus, Phenacobius mirabilis, and 

 Erimyzon oblongus, each association in a 

 different stream. This lack of similarity 

 or consistency in associations seems to 

 suggest little Interdependence between 

 species but rather dependence of certain 



SPECIES 



N crysoleucos 



H. biguttata 



C commersoni 



P. mirabilis 



E oblongus 



N chrysocephalus 



N. dorsolis 



E. buccota 



N. umbratilis 



H. nigricans 



SANGAMON SALT FORK KASKASKIA MIDDLE FORK EMBARRASS ALL STREAMS 





I 



4- 



_i_ 



I 



-I- 



I 



I 



.i_j 



I — I- 



Fig. 12. — Significant associations of several fishes in five drainages of Champaign County. 

 The coefficient of correlation (r) was better than the 0.02 level of significance except in the column 

 "All Streams," where the associations between Notropis dorsalis and Ericymba buccata and 

 between A', dorsalis and Ilybopsis biguttata were significant only to the 0.03 level. 



