yeah Dave,
I remember those fish. I was lucky enough to catch a few in the early to mid 1970's. They were chrome bright and super hard fighting! Just a shame that they couldn't have been brought back before their numbers were depleted.
I would think based on geographic proximity that the chinook in the North Fork Nooksack would be closest genetically speaking. This year was the first time in memory that we had a fishery on spring/summer chinook on the North Fork. I wonder if some brood stock could be provided to the Chilliwack hatchery instead. Of course, these fish don't have the bright red meat of the current Chilliwack hatchery stock, but they may be able to reproduce naturally in the system.
I wonder if those now extirpated summer chinook on the Chilliwack spawned above the lake? Or maybe in the upper reaches of Slesse creek? Spring and summer chinook in Washington seem to have adapted their run timing so they could reach the uppermost reaches of spawning water, that was the best place to hatch their eggs.