Dissolved Nitrogen Concenfrotions in the Columbia and Snake 

 Rivers in 1970 and Their Effect on Chinook Salmon 



and Steelhead Trout 



By 



WESLEY J. EBEL, Fishery Biologist 



National Marine Fisheries Service, Biolog-ical Laboratory 

 Seattle, Washington 98102 



ABSTRACT 



Concentrations of dissolved nitrogen gas varied widely in 1970 but were generally 

 lower in the Columbia River than in 1968-69. Concentrations were high, however, in 

 some areas of the Snake River in the spring and early summer, mainly because of spill- 

 ing of water at Little Goose Dam. Symptoms of gas bubble disease were widespread 

 in Snake River juvenile and adult chinook salmon (Oncorhynchus tshawytscha) and 

 steelhead trout (Salmo gairdneri) . There were substantial losses of fish, particularly 

 juveniles, during periods of high concentration of dissolved nitrogen gas. 



INTRODUCTION 



Continued evidence of the supersaturation 

 of dissolved nitrogen gas associated with spill- 

 ing of water at dams in the Columbia River 

 Basin has prompted the U.S. Army Corps of 

 Engineers to undertake studies to develop a 

 mathematical model for prediction of concen- 

 trations of dissolved nitrogen and to examine 

 means of designing spillways that do not super- 

 saturate the water. It was hoped that infor- 

 mation from the develo])ment of the model 

 would also enable the Corps to modify present 

 spillway operations to reduce nitrogen gas con- 

 centrations in the Columbia and Snake Rivers. 



This report summarizes the water sampling 

 data provided by the National Marine Fisheries 

 Service for the model and briefly reviews some 

 studies of the effects of supersaturation of dis- 

 solved nitrogen on some salmonids. Concen- 

 trations of dissolved nitrogen gas were mea- 

 sured twice a month from April to August 1970 

 in the lower 200 km of the Snake River and 

 the lower 640 km of the Columbia River. The 

 effects (unusual mortality and symptoms of gas 



bubble disease) of the concentrations were ex- 

 amined among various populations of juvenile 

 and adult chinook salmon (Oncorhyvchus tsha- 

 wytscha) and steelhead trout (Salmo galrd- 

 neri) . 



METHODS 



Dissolved Nitrogen Concentrations 



Stations from the forebay of Little Goose 

 Dam to Astoria, Oreg., were reached by air- 

 craft and sampled semimonthly from 7 April to 

 18 August 1970 (Figure 1 and Table 1). On 

 some trips, the aircraft could not land at all 

 stations because of high winds near some 

 sampling sites. Each set of samples was ob- 

 tained in a single day, usually on the second 

 and fourth Tuesday of the month. Samples 

 from forebay stations were taken at the surface 

 and at 10 m; samples from tailrace stations 

 were taken at the surface only. Data were 

 collected on dissolved nitrogen, dissolved oxy- 

 gen, and related water temperatures. The 

 sampling techniques and analytical procedures 



