Table 1. — Number of daily water samples analyzed from the 

 river and each holding tank during the test period. 



Table 2. — Concentration (percentage saturation) of dissolved 

 nitrogen gas in the Columbia River and deep test tank, from 

 samples taken every 4 h during a 24-h period, 14-15 June 1972. 



Difference in con- 



Table 3. — Maximum and average difference from river values of water quality data monitored 



in each holding tank. 



'Tank supplied with unaltered Columbia River water. 



Tank supplied with Columbia River water; nitrogen gas content of water had been reduced to about 

 lOO^c of saturation. 

 "This is within the sampling and analysis error. 



Oxygen concentrations were quite erratic, on a day 

 to day basis, ranging from 65 to 132% of saturation. A 

 combination of factors affected gas content of water in 

 the control tank; the water flow had to be reduced to 

 26 liters/min to avoid exceeding the capacity of the 

 gas equilibration device. Moreover, control of the air 

 supply to the device required constant monitoring, 

 which we were not able to do. Supplemental oxygen 

 was added to the water in the control tank to increase 

 its oxygen content to about the same level (after 

 biological demand) as in the river. It is obvious that 

 this was not accomplished. The addition of 

 supplemental oxygen into the tank probably caused 

 lower concentrations (below 100%) of saturation of 

 nitrogen by "stripping." More efficient methods of 

 manipulating gas content are required if very precise 

 concentrations of gas are needed. Even though there is 

 disparity in gas levels in the control tank, it did not 

 seem to cause erratic behavior or unexplained mor- 

 tality of test fish. 



Slight variations between river and control tank 

 water do occur in data other than oxygen and nitrogen 

 (Appendix Tables 3 and 4), however, all remained in 



acceptable biological ranges throughout the test 

 period. 



Test tanks. — In the two test tanks which were to 

 reflect the prevailing Columbia River conditions (as 

 outlined previously), there were only slight variations 

 between the river and the tanks in water quality data 

 (Table 3 and Appendix Tables 1, 2, 4). 



The concentrations of nitrogen gas in tanks 1 and 2 

 averaged 1.4 percentage points lower than in river 

 water; this is within the 2% sampling and analysis 

 error inherent in the gas analysis techniques. 



MORTALITY AND INCIDENCE 

 OF SYMPTOMS OF GAS- 

 BUBBLE DISEASE 



Mortality and Symptoms in Relation 

 to Type of Tank 



The total mortality and incidence of the gas-bubble 

 disease symptoms that were recorded throughout the 

 test varied from tank to tank. 



