EBEL. DAWLEY, and MONK: THERMAL TOLERANCE 



when supersaturation of nitrogen is present. 

 Tests in the deep (9-m) tank, where fish were 

 free to roam from the surface to the bottom, 

 revealed that mortality rates were much lower 

 and tolerance to temperature increases was in- 

 creased if the juveniles had the option to sound 

 when subjected to temperature increases. 



4. Coho were the most tolerant, chinook next, 

 and steelhead the least tolerant to temperature 

 increases when the water was supersaturated 

 with nitrogen. When supersaturation was not 

 a factor, coho and steelhead were about equally 

 tolerant to temperature increases and chinook 

 the least tolerant. 



5. Any increase in temperature allowed over 

 the ambient temperature (whether high or low) 

 of the river during periods of supersaturation 

 of nitrogen will be detrimental to migrating ju- 

 venile salmon and trout. Temperature stan- 

 dards should account for the effect of supersatu- 

 ration of nitrogen gas. 



LITERATURE CITED 



Beiningen, K. T., and W. J. Ebel. 



1971. Dissolved nitrogen, dissolved oxygen, and 

 related water temperatures in the Columbia and 

 lower Snake Rivers, 1965-69. Natl. Oceanic 

 Atmos. Admin., Natl. Mar. Fish. Serv., Data Rep. 

 56, 60 p. 

 Brett, J. R. 



1952. Temperature tolerance in young Pacific 



salmon, genus Oncorhynchus. J. Fish. Res. Board 

 Can. 9: 265-323. 

 1958. Implications and assessments of environ- 

 mental stress. In P. A. Larkin (editor). The in- 

 vestigation of fish — power problems, p. 69-83. 

 H. R. MacMillan Lectures in Fisheries, Inst. Fish., 

 Univ. B.C., Vancouver, B.C. 

 COUTANT, C. C. 



1969. Temperature, reproduction and behavior. 

 Chesapeake Sci. 10: 261-274. 



DuRKiN, J. T., D. L. Park, and R. F. Raleigh. 



1970. Distribution and movement of juvenile 

 salmon in Brownlee Reservoir, 1962-65. U.S. 

 Fish Wildl. Serv., Fish. Bull. 68: 219-243. 



Ebel, W. J. 



1969. Supersaturation of nitrogen in the Columbia 



River and its effect on salmon and steelhead trout. 



U.S. Fish Wildl. Serv., Fish. Bull. 68: 1-11. 

 Ebel, W. J., and C. H. Koski. 



1968. Physical and chemical limnology of Brovioilee 

 Reservoir, 1962-64. U.S. Fish Wildl. Serv., Fish. 

 Bull. 67: 295-335. 



Fry, F. E. J., J. S. Hart, and K. F. Walker. 



1946. Lethal temperature relations for a sample 



of young speckled trout, (Salvelinus fontinalis). 



Univ. Toronto Stud., Biol. Ser. 54 (Publ. Ont. 



Fish. Res. Lab. 66) : 9-35. 

 MiHURSKY, J. A., and v. F. Kennedy. 



1967. Water temperature criteria to protect 

 aquatic life. Am. Fish. Soc, Spec. Publ. 4: 20-33. 



PuGH, J. R., A. B. Gro\'es, and W. J. Ebel. 



1969. Experimental tank to simulate certain res- 

 ervoir conditions. J. Fish. Res. Board Can. 26 : 

 1956-1959. 



Smith, .1. R., J. R. Pugh, and G. E. Monan. 



1968. Horizontal and vertical distribution of ju- 

 venile salmonids in upper Mayfield Reservoir, 

 Washington. U.S. Fish Wildl. Serv., Spec. Sci. 

 Rep. Fish 566, 11 p. 



843 



