I run the Athabasca river, so am familiar with all the crossings for a about 100 miles.
The banks are pretty high, so they use the breaks to come down, and there are certain areas they ford frequently.
I spot and stalk these areas, and also call in the evening.
About 25 years ago when I was guiding a favorite method was to check for tracks going onto the islands, and calling.
The next morning , I would slide into the narrow channels betweeen the island and the shore, drifting down past the till it was okay to fire up the kicker, then head to the next one, and so forth.
Very sucsessful way of hunting....
Cat