92 ILLINOIS STATE ACADEMY OF SCIENCE 



Of the fish used, the yellow perch and steelhead trout 

 proved the most resistant and satisfactory. Excellent 

 results were obtained during the summer of 1911 in the 

 tests with these two varieties. However, it seemed de- 

 sirable to postpone publication until the experiments 

 could be extended and the results verified by subsequent 

 cultures. Consequently, early in the season of 1912, 

 large reinforced concrete tanks were built and the ex- 

 periments were conducted out of doors. Yellow perch 

 were gotten again from the nearby lakes and Turtle 

 Mountain region and passed through the control experi- 

 ments, duplicating those of 1911. When the perch were 

 transported properly and the acclimatizing experiments 

 conducted with care, the percentage of loss was only 10 

 per cent, including the losses which came from injuries 

 in transportation and failure to recover from the fatigue 

 of the trip. It was found that from 300 perch received 

 on the 19th of July, 246 were vigorous and absolutely 

 normal when examined in the floating fish pens on August 

 12. The following year we recaptured yellow perch from 

 Devils Lake, proving that they had survived the change 

 one year. 



In the latter part of May, 1912, a shipment of rainbow 

 trout was received from the United States Fish Hatchery 

 at Spearfish, South Dakota. They were placed in tanks 

 containing well water on May 22. There Avere many 

 fatalities during the month of June, due to mechanical 

 troubles with the pumping plant of the station. On July 

 3, the trout which remained alive from the shipment re- 

 ceived six weeks before were transferred to the tanks 

 outside of the building into which there was introduced a 

 mixture of lake and well water. An exceedingly high 

 temperature during the 3d and 4th of July raised the 

 temperature of the upper lake water 10 degrees above 

 that which had been in the indoor tank water. Further- 

 more, they had been placed in newly built concrete tanks 

 from which soluble salts had not been sufficiently removed 

 by long continued washings with the fresh or well water. 

 The result was that out of 100 placed in the tank at this 

 time, 40% died within 36 hours. There was a lowering 

 of the oxygen content of the water, a great increase in 



