March, 1963 



Larimore & Smith: Fishes of Champaign County 



339 



species on certain ecological factors. These 

 factors ma}' occur together in one stream 

 system, thus bringing two species together, 

 or they may be separated in another 

 stream system, thus separating species. 

 Two species might occur together tempo- 

 rarily or abnormally, as during periods of 

 low water when many species may be 

 forced into constricted water areas. 



Thompson & Hunt (1930:66) stated, 

 "Most instances of the association of dif- 

 ferent species of fishes are explained satis- 

 factorily by similar environmental prefer- 

 ences." However, they pointed out a very 

 significant exception to this statement in 

 their discovery of a close association be- 

 tween Hybopsis biguttata and Notropis 

 chrysocephalus. For these two species, they 

 suggested a direct dependence, at least at 

 some stage in the life cycle. Our 1959 



surveys with respect to the general abun- 

 dance and occurrence of fishes as recorded. 

 Some of the variables in such compari- 

 sons were eliminated by consistently fol- 

 lowing throughout each survey a proce- 

 dure adapted to it and by excluding from 

 consideration any stations that in either 

 survey were influenced strongly by pollu- 

 tion or that were not visited by both sur- 

 vey parties. Seventy-one collections were 

 then available for comparison. 



Average Number of Species 

 Per Station 



A consistently larger number of species 

 per station was found in collections taken 

 in the 1959 than in the 1928 survey. The 

 average was 13.2 species per station in 

 1928 and 19.0 in 1959; the ratio was 

 1 :1.4, table 13. The samples taken in the 



collections revealed a significant (P less later survey were considerably larger nu- 

 than 0.01) association between these two merically and thus might be expected to 



minnows when all the collections for the 

 county were considered together, but no 

 consistency of association in any of the 

 separate drainage systems, even though 

 both species were taken in rather great 

 numbers in four of the systems. 



GENERAL ABUNDANCE 

 AND OCCURRENCE 



The use of collecting methods in 1959 

 that differed from those of 1928 contribu- 

 ted to the difficulty of comparing the two 



contain a higher percentage of those 

 species present at the collecting stations. 

 In the two surveys, the drainages were in 

 the same order with respect to average 

 number of species per station ; for example, 

 in each survey, the Middle Fork had the 

 largest number of species per station and 

 the Embarrass the smallest number. 



In the 1959 survey, quantitative col- 

 lections from the blocked-off stations 

 produced between 88 and 97 per cent of 

 the total number of species collected at 



Table 13. — Average number of species per station and average number of fish per 100 square 

 yards taken in 1928 and 1959 at 71 stations (not noticeably affected by pollution) in five major 

 drainages of Champaign County (no quantitative samples were taken from the Little Vermilion) ; 

 also, average number of pounds of fish per 100 square yards in 1959. 



