It certainly seems surprising that Okanagan sockeye have rebounded as well as they have, especially when compared to Fraser stocks. All those dams on the Columbia providing obstacles for both upstream and downstream migration. High water temps as the Okanagan and Columbia pass through seriously hot dry terrain. Relatively high population density in the Canadian part of the Okanagan watershed. The Fraser has some advantages in these respects and yet is struggling so badly. Above posts suggest ocean conditions are relatively same for most stocks in the PNW.
This population is still a fledgling, with off-year stocks much lower than even, but there is much cause for hope. Some excellent spawning habitat in the Shingle Creek drainage had passage restored in 2014 and now there is official access to Okanagan Lake and its creeks. The province was opposed to this for many years, purportedly due to concerns over impacts on kokanee stocks. DFO and FN were agreed long before. There have been small releases of sockeye fry into Okanagan for 4 or 5 years already in anticipation of opening passage.