186 Fortieth Annual Meeting 



flood in our great rivers, the spawning time of the bulk of 

 our fishes, and the climax period in the development of the 

 plankton. All coming together or following one another 

 in quick succession, as they normally do, conditions are as 

 favorable as possible for a large stock of young fishes. The 

 longer the period and the larger the scale of the spring 

 overflow, the better is the prospect for a heavy annual con- 

 tribution to the population of the stream. To this, no 

 doubt, is due the fact, clearly indicated by our recent river 

 work, that the plankton product of the Illinois system has 

 been greatly increased by the opening of the drainage canal 

 from Lake Michigan and the consequent raising of the 

 average level of the river by about three feet, this rise of 

 river level resulting, of course, in ,a more widespread and 

 longer-continued overflow. 



On the other hand, nothing can be m9re dangerous to 

 the continued productiveness of these waters than a shutting 

 of the river into its main channel and the drainage of bot- 

 tom land lakes for agricultural purposes. It is fortunate 

 for our fisheries when one of these lakes comes into the 

 possession, or under the control, of a hunting or fishing 

 club, for this insures its maintenance. The time has come, 

 in my judgment, when the state should consider seriously 

 the policy of preserving adequate breeding grounds and 

 feeding grounds for our river fishes, even if it has to acquire 

 and maintain them, since these waters are in imminent 

 danger otherwise of being practically depopulated. 



It is another interesting conclusion from our recent work 

 that the enormous outpouring of Chicago sewage into the 

 upper Illinois has thus far improved rather than impaired 

 its fitness for the maintenance of fishes. The organic wastes 

 thus emptied into the stream are laid hold of by bacteria 

 and protozoa, and passed up by successive steps to form the 

 flesh and bones of fishes, and thus finally those of men. 

 The same may be said of the organic wastes of the towns 

 along the banks of the stream. 



Still another conclusion of considerable practical interest 



