I can provide some ideas on why the SRFC Program has been reasonably successful, but I can’t compare it to programs that haven’t been.

Here goes:

The habitat in the Lower Snake has improved considerably. The huge flow fluctuations from Hells Canyon have been moderated so that the habitat isn’t flooded and dewatered on a daily/hourly basis.

Dworshak Dam is being used more to reduce temperatures in the Lower Snake to help out-migrating juveniles in the summer, and upstream migrating adults in the fall.

Perhaps most importantly, the spill program in the Lower Snake dams and the mainstem Columbia projects is a huge benefit to juvenile subyearling fall Chinook. So their survival through the hydropower system has improved considerably.

To some degree, these fish are less susceptible to harvest. The returning hatchery adults are clipped but if those adults spawn in the Lower Granite pool, and they do in large numbers, their progeny are not clipped (duh) since they are not hatchery origin. Unclipped fish are not subject to recreational angling in the Columbia River, although they remain subject to commercial fishing in the Lower Columbia, tribal fishing above BON, and harvest in the ocean.

And to a large extent, for this specific stock, it appears to be a 'numbers game'. That is, if you stock more hatchery fish, you get more adults back, those excess adults are allowed access to the spawning grounds, they appear to be spawning successfully, and the resulting recruits also return as adults. Not every population responds this way. But this one does.