44 ILLINOIS ACADEMY OF SCIENCE. 



fishing in this State. The Illinois product of mussel-shells in 1894 

 was 24 tons, in 1899 it was 2,500 tons, and in 1908 it was 20,000 

 tons, with a value during the latter year of $184,000 for shells 

 and $170,000 for pearls and slugs. This must, of course, result 

 in the prompt destruction of the mussel population of our streams. 



To summarize these statements in a sentence, it is plain that 

 the clam fisheries of the State are being rapidly exhausted, and 

 that the European carp is, with the aid of the fishermen, rapidly 

 swamping and smothering out several of our native food fishes, 

 both coarse and fine, excepting, however, the sunfishes and the 

 black bass. This seems due not to direct competition between the 

 native and the imported species, but to human interference under 

 the economic motive. We have here a substitution process at 

 work, like that of our pioneer agriculture, but differing from 

 that in the fact that it has been unintentional and hitherto un- 

 noticed. If these present tendencies continue we shall apparently 

 have, in time, our larger and more important fishing streams pro- 

 ducing little but carp, sunfishes, black bass, gizzard-shad, dog- 

 fish, and gars, with even the catfishes engaged in a somewhat 

 doubtful struggle for existence. 



Several additional dangers now threaten the Illinois River, 

 much the most important of our productive waters. It may be- 

 come overloaded with sewage from Chicago and from the cities 

 on its banks ; the establishment of manufactories along its course 

 or on its contributing waters may befoul it with chemical wastes 

 poisonous to fish or injurious to their food supply, a process 

 which has completely depopulated many streams in the eastern 

 states, and which some of these states are now seeking to correct, 

 at great expense and trouble, by legal restrictions and adminis- 

 trative control. Our recent work shows that the productivity of 

 a stream is dependent upon the extent and condition of its back- 

 waters and the period of its overflow, a fact which makes drain- 

 age district operations on the river bottoms a menace to its pro- 

 ductiveness. The same is true of measures for straightening 

 the stream and confining it to its channel, such as are likely to be 

 necessitated if the Illinois is to become at any time a great artery 

 of commerce. 



These conditions require prompt, vigorous and intelligent recti- 

 fication and control if we are to preserve and improve the natural 

 resources represented in our lakes and streams — measures quite 

 beyond the reach of any power except that of the State. If time 

 permitted, I should be pleased to enter upon a discussion of 



