There is one obvious FACT that has eluded some people in this discussion... The decline in Bow river trout and aquatic invertebrate populations are uniform from Banff too the Bassano dam, regardless of the degree of fishing pressure.
And how we interpret statistical data can be subject to flaws in perception. For example, lets say we analyzed the anual fish eating, avian predator counts for the past 20 years. Pelican's, Cormorants, Osprey, Eagles. We could come to the conclusion that since their numbers on the Bow have increased significantly, then there must be more fish! Which we know is not the case.
The rise in these Avian predators is mostly due to the fact that we have been stocking lakes and ponds all over southern Alberta and in many community lakes in the Calgary area. Storm ponds are full of Goldfish, Prussian Carp, and we have numerous stocked put and take public lakes, private ponds, (golf courses), Irrigation Canals full of thousands of trapped fish and so forth in the area. We have been doing this for many decades. It has become a fish eating Paradise for these birds.