Flows into the return channel are currently at a minimal level because the boards hold the water elevation so high that the backwater effect at the top end of the diversion channel (200 yards or so upstream) is slackwater and the river flows are directed into the main channel.  Remove the boards and the flows will exceed 10 cfs.  And it’s October 15 so the boards need to be removed and the additional water flow will attract the spawners into the channel.