Stream Pollution 45 



ever, when one has to contend with an intermediate situation there 

 is the greatest difficulty in deciding from the evidence obtained from 

 observations on fish alone what is the cause of the condition. Fish 

 are sufficiently active animals that they move into unoccupied terri- 

 tory and move out from it under varying circumstances and with 

 considerable promptitude. How they conduct themselves in refer- 

 ence to highly polluted streams is well shown by observations which 

 may be cited here. For the clearer comprehension of this instance, 

 let us recall that the city of Chicago discharges its wastes into a 

 huge drainage canal which at Lockport empties into the Des Plaines 

 and this latter stream in turn joins the Kankakee a few miles below 

 to form the Illinois river. These streams, and particularly the last 

 mentioned, has been under biological observation by the Illinois 

 State Natural History Survey under the direction of Professor S. A. 

 Forbes for some thirty years, so that records were made of its 

 character long before the construction of the drainage canal and the 

 addition to its waters of the highly polluted Chicago sewage. The 

 Illinois river has always been an important source of fish for anglers 

 and commercial fishermen. More recent records demonstrate how 

 the fish conduct themselves towards the radically changed con- 

 ditions and the observations are so pertinent to this inquiry that I 

 propose to discuss here their finding for comparison with records 

 made by various New York state officials at different places in this 



Fish Shun Pollution 



The definiteness with which fish avoid polluted waters and the 

 effects of such waters on them can be well shown by some citations 

 from observations on the Illinois river (Forbes and Richardson, 

 19T3). In the sanitary canal at Lockport they record (Sept. 1911) 

 " a few small shiners (Notropis atherinoides) one to two inches 

 long were alive in the water though in a dying state ; but all the 

 larger minnows of this species, * * * were stranded dead 

 along the shore. In the cooler weather of November, 191 1, 

 a larger proportion of the shiners were alive." In the Des 

 Plaines at Lockport " no fish were seen here in September, the water 

 being much too foul for even the most indifferent species." In 

 November they found " many shiners, nearly all alive but mostly 

 in a dying state, as if they had been carried down by the current 

 from above and overpowered by the toxic contents of the stream." 

 In August and September, 191 2, one could see " a marked contrast 

 between the two sides of the river, due to the fact that the water of 



