ABSTRACT 



The blueback salmou spawning area of the Okanogan River 

 has been surveyed extensively each yeeir since the start of a 

 Canadian flood-control project in 1951. The spawning populations 

 have been estimated and their distribution above Rock Island Dam 

 detezmined. The large niiober of fish unaccoxmted for may be 

 partially attributed to mortalities caused by the high water 

 temperatures existing in the Okanogem River prior to spawning. 



The age, length, eind sex compositions of the 1957 Okanogan 

 River spawning escapement were determined from samples collected on 

 the spawning grounds. Althoiigh seme delay in passage occurred at 

 the thirteen newly completed drop structures, completeness of spawn- 

 ing was not abnonoally low. 



The occurrence of large numbers of 33 's ^ *^ spawning 

 population seems to be peculiar to the Okanogan River. 



The distribution of fish on the spawning grounds has not 

 changed appreciably since 1952. 



