Table 2. — Concentrations of dissolved nitrogen and oxygen gas and related water temperatures in the Columbia 



and Snake Rivers, 7 April to 18 August 1970. — Continued 



Effect of Dissolved Nitrogen on Fish 



Various populations of juvenile and adult 

 salmon and trout were examined in 1970 for 

 mortality and symptoms of gas bubble disease 

 that resulted — directly or indirectly — from 

 supersaturation of dissolved nitrogen in the 

 Snake and Columbia Rivers. 



There were substantial mortalities due to 

 supersaturation of nitrogen among stocks of 

 juvenile chinook salmon held in cages at var- 

 ious depths near Ice Harbor Dam (Tables 3 



Table 3. — Mortality of juvenile spring chinook salmon 

 of wild (native) origin held in cages at various 

 depths in the forebay of Ice Harbor Dam, 21-28 May 

 1970.' 



Holding 

 time 



Cage depth (m) and mortality (%) 



Surface 



75-1.0 m 



1.5-2.0 m 



3.0-4.0 m 

 (control) 



0-4.5 m 



24 hours 60 



48 hours 92 



7 days 100 



No test No test 



=6 



M5 



' Water temperature was 11.9° C and dissolved nitrogen 

 concentration was 127% of saturation at start of test; water 

 temperature was 12.4° C and dissolved nitrogen concen- 

 tration was 127% of saturation at end of test. 



■ 17% of survivors had symptoms of gas bubble disease. 



^ 94% of survivor: had symptoms of gas bubble disease. 



through 6) . I believe that data from the 0-4.5 m 

 cage are probably most representative of what 

 may have happened to migi'ating juvenile fish 

 because the caged fish could sound at their vo- 

 lition to 4.5 m. Mortalities in the 0-4.5 m cage 

 ranged between 45 and 68% from late May 

 to early July. 



Examination of juvenile migrants taken in 

 gatewells at Ice Harbor indicated that 25 to 

 45 '^f of the chinook salmon and 30 to 58 Tr of 

 the steelhead trout had symptoms of gas bubble 



Table 4. — Mortality of juvenile fall chinook salmon of 

 hatchery (Wahkeena Pond) origin held in cages at 

 various depths in the forebay of Ice Harbor Dam, 

 4-11 June 1970.' 



Holding 

 time 



Cage depth (m) and mortality (%) 



Surface 



.75-1.0 m 



1.5-2.0 m 



3.0-4.0 m 

 (control) 



0-4.5 m 



24 hours 



48 hours 



7 days 



98 



98 



100 



64 



98 



100 



'40 



'2 



'68 



' Water temperature was 12.4° C and dissolved nitrogen 

 concentration was 127% of saturation at start of test; water 

 temperature was 13.8° C and dissolved nitrogen concen- 

 tration was 132% of saturation at end of test. 



- 97% of survivors had symptoms of gas bubble disease. 



•^ 92% of survivors had symptoms of gas bubble disease. 



' 100% of survivors had symptoms of gas bubble disease. 



