COLUMBIA RIVER WATER 



PUMP 



FIG. 2 Plan view of 1.5 x 3.3 m tank used to determine if juve- 

 nile fish can detect and avoid N ., supersaturated water. 



replicate test is conducted (using fish from the 

 same population) by switching the "high" N 2 

 and "low" N 2 channels. A sample of 20 fish is used 

 for each test. 



Preliminary tests have been conducted on two 

 species of fish; juvenile steelhead trout and fall 

 chinook salmon. During the first test 50 o/ -> of the 

 steelhead died in 42.5 hr; in the replicate test a 

 50% mortality was reached in 43 hr. The survivors 

 from both tests had external gas bubble disease 

 symptoms. No mortalities occurred in the two 

 replicate chinook tests (within 192 hr) and only 

 10% showed external N 2 symptoms. These two 

 preliminary tests indicate that the juvenile steel- 

 head did not avoid the high gas concentration 

 while fall chinook salmon did. Results from the 

 intermittent exposure tests in Table 1 of this report 

 show juvenile steelhead to be less tolerant to con- 

 centrations of dissolved nitrogen than chinook. 



N 2 BIOASSAY TESTS 



Two types of N 2 bioassays have been con- 

 ducted at the Prescott Facility since 1971: 1) 

 tests using deep (1.8 x 2.5 m) and shallow (1.8 x 

 1 m) test tanks at prevailing river levels of N 2 

 and 2) tests using small 175 ? tanks (0.33 m water 



depths) at constant 

 and 100% saturation. 



N, levels of 130, 120, 110, 



Mortality in Deep and Shallow Tanks 



The primary objective of these tests was to 

 determine if water depth enhanced fish survival. 

 Table 2 summarizes the species used, number of 

 fish in each test, test duration, range and average 

 nitrogen levels and the total percent mortality that 

 occurred during the test. The N 2 levels, as indicated 

 in Table 2, were either created artificially or were 



TABLE 2. Summary of the Numbers of Each Species Held in the Three Tanks (Two Each 1-m 



Deep and a 2.5-m Deep Tank) Used for Bioassay Tests at the Prescott Facility. Included in the 



table is the number of days the fish were held and the N 2 saturations. The percent mortality 



that occurred in each tank is shown for each species. 



'Control tank gas equilibrated 



-R = naturally occurring river levels 



Research at Prescott 13 



