This issue has been brewing for at least 8 years that I know of. Im not certain if this is the heart of the issue but Im fairly certain it is. I used to work where some of my co-workers were looking at the effects to native amphibians in high elevation lakes from stocked trout. These were lakes that did not have native trout populations, but were being stocked by DFG via airplane. It was a huge issue for many people.

Sounds to me like the high mountain lake concern has trickled down to include rivers as well. I havent been able to find any in-depth article explaining the issue in full so I havent got a complete grasp of whats going on just yet. Does anybody have a link for a more informative explanation of the issue?