Shltdh2o-
The "Dollies" and chinook use difference spawning habitats (chinook mainstems and Dollies headwater areas) those large fish were likely lake run or adfluvial fish. In most the species range the largest fish rear in lakes (more food for a longer period), the next anadromous, then fluvial and finally the resident life history.

Those lake feeding fish were in the river either migrating upstream to spawn or returning post spawn - not unlike anadromous fish we here in the western side of the mountains are familar with.

Tight lines
Smalma