PAPERS PRESENTED AT GENERAL SESSIONS 91 



It was further found that the fish taken from fresh 

 water lakes and transported 100 miles or even a shorter 

 distance required some time to recover from the effects 

 of transportation. Usually the fish which were weakened 

 or injured through transportation would be eliminated 

 during the first four to six days they were in the experi- 

 mental tanks. At the expiration of this period, Devils 

 Lake water was mixed with the water from the deep well 

 in the portion of one to three. At intervals of two to 

 three days, the proportion of Devils Lake water entering 

 the tanks was increased until the wholly undiluted De- 

 vils Lake water was supplied to the experimental tanks. 

 Under average conditions, with average shipments, it 

 was found that this process of increasing the per cent of 

 Devils Lake water could be completed within ten to twelve 

 days. After the fish had been retained in these experi- 

 mental tanks for a period of one to three weeks, they were_ 

 transferred to anchored floating fish pens in order that 

 their condition and behavior might be kept under ob- 

 servation for several weeks. It will be noted that the 

 specific gravity of the Devils Lake water to which they 

 had become adjusted in the acclimatizing experiment was 

 1.019. It is to be further observed that they were taken 

 from water having an osmotic pressure of .03 to .04 of an 

 atmosphere and they were placed in water having an 

 osmotic pressure of 4.6 atmospheres. As previously 

 stated, it was found necessary to keep the temperature of 

 the tank water within the range of 17 to 19 degrees C, 

 and to maintain an oxygen content not lower than 4 cubic 

 centimeters per liter in order to secure the best results. 



The transfer to the floating fish pens in the lake was 

 more successful if it was done in the evening or during 

 cloudy days, presumably because the temperature of the 

 lake water was lower at those times than during periods 

 when it had been subjected to the heat accompanying 

 bright sunshine for some hours. Floating tanks were 

 found to be far more satisfactory than submerged ones. 

 The latter gathered too much fioating debris and sand 

 which, of course, would interfere materially with the 

 respiratory apparatus of the fish placed in the submerg- 

 ed pens. 



