10 American Fisheries Society 



carried out an action against the State of Illinois for polluting 

 the waters on which St. Louis was dependent; and the conditions 

 of the drainage canal, of the Illinois water and of all the water 

 from Chicago down stream have been very carefully investigated. 

 Now if you obsefve the river just below the point at which the 

 drainage canal has emptied into it you will convince yourself very 

 readily that it is nothing more in summer time at least, when the 

 flow is reduced to nearly the lowest terms — it is nothing more than 

 an open sewer, a septic tank in which the sewage has been deposited 

 and in which changes are taking place to make over that organic 

 material into a form such as can be utilized by the higher organisms. 

 The little streams that run in are different in character. I have 

 known of, and have seen, numerous instances where, watching 

 such a little stream at the point of entering into the larger, one 

 could see fish come down stream, swim up to what you would 

 fix in your mind as the arbitrary line of division between the 

 relatively pure waters of the small stream and the highly polluted 

 waters of the main river; the carp would come to that line, stick 

 their noses over it and go back again; come up again and do the 

 same thing. They were possessed with a desire to migrate, but 

 that desire was overcome by the conditions that they faced when 

 they started to move from the smaller water into the larger. It 

 is only very rarely one can see anything of that kind, because 

 these larger fish often will pass into and through the highly pol- 

 luted water in the endeavor to seek other regions where food is 

 more abundant, or where for some other reason they desire to 

 make their home. 



Now then, the mere presence or movement of fish in any water 

 is not necessarily indicative of the quality of that water. The 

 second thing, of course, to which your attention must be called, 

 is that different kinds of fish are very different in their suscepti- 

 bility to impure water. From recently published experiments 

 and tables it may be seen that the bullhead, for example, has a 

 power of resistance or an indifference to polluted conditions 

 which as compared to a minnow will be as forty-five to one, — 

 so great is the difference between those two kinds of fish. Most 

 of our valuable fish are rather sensitive to conditions of pollution, 

 and do not find themselves happy or well situated in waters that 

 are polluted to any extent, while some other fish can exist appar- 

 ently without being incommoded. 



