Fish Culture in Inland Waters 261 



has occurred with the fishes in some of those streams ; but do we 

 know that one is the cause of the other? We think that sawdust 

 injured the fish, but do we know it ? " 



Doubtless the foregoing questions were asked to emphasize the 

 necessity for scientific investigation to prove or disprove prevalent 

 views concerning the subjects before trying to regulate them, — not 

 that Evermann himself probably doubted that certain kinds of pollu- 

 tion at least were injurious to fishes. There can be no doubt of 

 that, for it is known. At first, however, it was inferred. The 

 direct effect of certain chemicals upon organic substances was well 

 known. It was therefore supposed that these chemicals would be 

 injurious to organic life in a stream. There could be no doubt that 

 in concentrated form they would be. How much dilution would 

 render them harmless to fish life, or w'hether the water in the 

 stream would sufficiently dilute them was not known, and although 

 many investigations both in laboratory and in the field have been 

 made, the questions have not been settled to the extent that the re- 

 sults can be applied to every instance of pollution. Inferences are at 

 times apparently justifiable. For instance, when a stream once fre- 

 quented by fish is now deserted, and no other modification than exces- 

 sive pollution has taken place, it is not a wild guess to attribute the 

 fact to pollution. Such a case is the Passaic River in New Jersey. 

 When streams were frequented by fish up to the time mines were 

 opened on the banks, and as soon as mine waste was discharged into 

 the rivers the streams were forsaken by fish, it would appear reason- 

 able to attribute the disappearance to mine waste. On the other 

 hand, when cases of polluted streams frequented by fish are cited, 

 what answer can be given? 



It is necessary to ascertain the extent of the pollution and its 

 effects upon other organic life rather than directly upon the fish 

 themselves, for the deleterious effects may be upon the food supply 

 or some other essential condition. It is necessary to ascertain 

 whether the stream is actually frequented by fish more than tempo- 

 rarily. Certain fish may at some time or other ascend a stream 

 which is more or less polluted. They may not encounter sufficient 

 pollution to seriously affect them, or to turn them back, until a long 

 way upstream. The spawning places may be so polluted that the 

 fish cannot propagate. Their migration, in such instances, has been 

 in vain so far as the perpetuation of the race is concerned. Or 

 even if the fish spawn in polluted areas, the eggs may not develop 

 and no young fish be produced. 



W. C. Adams, of Massachusetts, says ('21, p. 29) : " Observa- 

 tions were made on the conditions in the Merrimac River, not for 

 the purpose of isolating and analyzing the different types of pollution, 

 but rather to determine whether any fish would frequent these 

 waters in their present state of defilement, and to observe something 

 of the fish life in the river. As stated elsewhere, the belief has 

 been general that the condition of this river was such that no migra- 

 tory fish would frequent it. This has proven to be erroneous by 

 the presence of alewives in the fishway at Lawrence during the past 



