Plenty of interesting comments/observations in this thread. I don't fish the Bow much at all, but I might add a few questions/comments to the discussion:
When comparing the Bow to how it was "x" years ago, one thing that doesn't seem to be discussed much is the fact that Calgary has grown so much over those past "x" years, to now a city of well over 1 million. As the city has grown, how has water quality been affected - more concrete/pavement (and runoff from same, washing in who knows what), more treated sewage water volume, more developments along the riverbanks, altering the banks and sedimentation, etc.
Also, it seems to me that when we talk about the health of the fishery, we focus primarily on the trout (for obvious reasons) - but isn't it the entire riverine ecosystem that we should be examining? Maybe we are - but what about the health of invertebrates in the river (trout food), and other fish species like whitefish, suckers (competitors for trout food)?