90 ILLINOIS STATE ACADEMY OF SCIENCE 



this greatly desired result. A study of the experiments 

 which had been made by preceding workers offered small 

 hope of success provided their procedures were closely 

 followed. However, to make quite sure, a duplication of 

 the former experiments was made with the result that 

 those in charge of the Station work became convinced 

 that there Avas no hope of success in following the lines of 

 procedure formerly instituted. The problem was entirely 

 too complex for sltij guess work or merely empirical pro- 

 cedure. In other words, it was manifest that successful 

 culture and distribution of fish rested wholly upon as- 

 certaining, first, the phj^sical, chemical, and biological 

 facts which entered into this very complex problem. As 

 already indicated, these facts could be learned only 

 through analyzing many hundreds of collections, carrying 

 forward many experiments, and determining the limiting 

 factors of the life already present in Devils Lake. 



After determining that there seemed to be no inhibiting 

 toxic agents present, that there was ample oxygen in the 

 water and thousands of tons of available fish food, an 

 effort was then made to determine whether a successful 

 method of introducing fresh water fish into Devils Lake 

 might be established by following a procedure similar to 

 that which characterized the natural situation in former 

 years. Consequently, a series of tanks was built in the 

 Biological Station and they were supplied with special 

 devices for adding oxygen to the water as it was pumped 

 into the tanks. 



Yellow perch and other forms experimented with would 

 frequently show great distress and die within an hour 

 when placed in shallow water at a temperature of 24 de- 

 grees C, whereas when the temperature was kept loAver, 

 from 17 to 20 degrees C, they appeared to be quite com- 

 fortable. In view of this, the water was introduced into 

 the tanks at 17 to 19 degrees C. The aerating devices as- 

 sured a gas content of 4 to 6 cubic centimeters of oxygen 

 per liter. Yellow perch, steel-head trout, large-mouthed 

 black bass, pike, and some other varieties of fish were 

 used in the experiments conducted during the summers 

 of 1911 and 1912. 



