Fish like to key into spots where there is good flow and especially up-welling of flows through clean gravel. These flows provide oxygenation for the eggs.
With a bottom covered in algae like the Bow, redds look like places that have been swept clean.
So the end of a run as it shallows out before a riffle (and even in the top of the riffle) is often a good spot for a redd. Fish often look for some over hanging cover in addition to good flows and proper substrate size.
Take care of the next generation for future angling fun