Way back in the 1950s CA successfully conducted a study on San Joaquin River Chinook using tangle nets to capture fish to attach acoustic tags. Reason for the study was to see the response of the fish to low flows, low DO, and high temperatures in the lower river-basically around Stockton. These were Fall fish.
They tracked the fish, having spread recorders through the delta. I forget. now, the final conclusions, but they had enough recoveries to get an idea of migration patterns and response to conditions. So, if the bay is warm, the rive warm, and DOs low there is some information out there as to what the fish will do.
They may have done this study over a couple of years.
The Fraser is reportedly flowing at 75% of average and warmer than average. This information has been used since at least the 80s to understand how the sockeye and pink respond and I am sure that DFO has a clue as to how it affects the other species.