Hi Rev,
I think I can shed some light on your questions...
12 inch growth rates over a year are probably a stretch in most instances for NW trout. But, 6 to 8 inches per year is pretty common, and that is a lot faster than our bass. The thing to remember about trout in most of our waters is that they usually don't have a good place to reproduce in lowland lakes (colder, flowing water, gravel), so usually they can only sustain fisheries when they are stocked.
12 inch bass are around 3-5 years old in WA state, and there doesn't seem to be much difference between eastern and western WA. Looking at some past reports I have, 4 years would be about average, and 6 is possible, but only in really poor conditions (bad water quality or lack of food).
As far as the slow growth rate justifying why we need to put bass back... I would disagree with those folks in most instances. Bass produce a LOT of offspring, and they mature at an average rate compared to the rest of the fish world. Usually, food becomes the limiting factor for predator (bass) success in a lake. If there is a lot of food, then a lot of those small fish can grow together. If there is limited food, then we need to crop some of those smaller bass to limit competition. I believe this is the driving concept behind the statewide slot limit. Limiting food is a common case in WA state. The warmwater folks that work with this stuff every day may disagree, but I think I am on the same page as them.
"I love hearing myself type."
I would say that walleye metabolism is closer to trout than bass in the wintertime. I say this because they spawn at lower water temperatures than bass and at almost the same time as most trout in local streams.
Chris