Stream Pollution 



43 



Species of Fish 



Ambloplites rupestris 

 (Rock bass) 



Perca flavescens 



(Yellow or American perch) 



Lepomis cyanellus 



(Blue-spotted sunfish) .... 



Ameitirus melas 

 (Black bull-head) . . 



Rela- 

 tive re- 

 sistance 



Best place to collect 



Clean-bottomed pools with rocks. 

 Creeks and small rivers. 



Abundant in some lakes. Also in 

 larger rivers but not in creeks. 



Pools in creeks. Often with mud 

 bottom. 



Ponds; pools in small creeks. Mud 

 bottom among vegetation. 



" While in the table only eighteen species of fishes are listed, the comparative 

 resistance of other species may be estimated by comparing their i esistance with 

 that of some one of the listed species. By placing a species of unknown resistance 

 in an experiment with one of the species given in the table one may obtain 

 results that will make it possible for him to compare the resistance of the un- 

 known species with that of any of the species listed. It should be pointed out 

 also, that fishes of the same large taxonomic group have in general a similar 

 power of resisting detrimental factors. Thus, the darters are a group possessing 

 for the most part a low ability to resist untoward conditions. The minnows 

 (Cyprinidae) are fairly resistant as a group; the sunfishes are more resistant 

 than the minnows; and the catfishes are notably our most resistant group of 

 fresh-water fishes. The place of an untried species in the resistance table can 

 be reckoned more or less accurately by placing it with the listed representatives 

 of the taxonomic group to which it belongs. 



" From column 3 of the table it will be seen that the resistance of the fishes 

 is rather closely correlated with the type of environment which they inhabit. 

 The more resistant species are found in ponds, shallow, muddy-bottomed lakes, 

 or in the stagnant pools of streams. These are the fishes which one sees in aquaria. 

 They are able to withstand increased temperature and wide fluctuation in the 

 oxygen and carbon-dioxide content of the water, and to some extent are able 

 to live in the presence of the excretory products of their own metabolism. The 

 stream fishes proper can not do this, and therefore die when placed for any length 

 of time in standing water." (After Wells, Bull. 111. State Lab. Nat. Hist., 

 1 1 ;567-568.) 



Bacteriologic Tests 



There is need to test in some accurate way the character of a 

 stream and the methods most generally employed have been bacterio- 

 logical and chemical. Bacteriological methods are developed with 

 reference to determining the character of the stream from the 

 standpoint of public health, which usually is considered to concern 

 only the human species. Consequently, determinations are made of 

 certain definite kinds of bacteria that are inimical to human welfare, 

 and little or no attention is paid to other elements in the situation. 

 It is conservative to say that our knowledge regarding the bacteria 

 is not adequate as yet to determine all of the forms found, or to 



