ABSTRACT 



At Bonneville Deun most downstream-migrant salmonlds were ca\ight 

 during hovirs of darkness during the years 19^6, 19^9, 1950, and 1953. 

 In 1952, however, the majority were day migrants. Hourly fishing in 

 1952 and 1953 indicated that laaxlmum movement of chlnook salmon and 

 steelhead trout tends to occur at dawn smd dusk; additional data are 

 needed for blueback emd silver salmon. Although the data are far 

 frcBB conclusive, the percentage of chlnook salmon that migrate at 

 night appears to he more highly correlated with turbidity than with 

 days elapsed from start of sampling. Other factors, which imdoubtedly 

 affect day -night migration, were not tested. 



