HN user
I live to the west of you out on the peninsula and we couldn't get milk for the past week and a half. As in there wasn't a single carton of milk anywhere in multiple stores. Curious if it's just smaller towns relying on distribution from the city, and getting cut off first or what. I figured Seattle would have had similar issues.
It generally happens pretty quickly. Salmon seem to all have a "stray rate", where some percent will stray from their natal river on their spawning run. It makes sense, as it allows for colonization of new habitat, or to revive extinct populations. A lot of the current salmon habitat from Washington north was under glaciers not too long ago. So they have been doing this exact thing for millennia.
Straying is partly why you can see salmon spawning above former dam sites, even shortly after removal. It's also why you will occasionally see salmon in a stream with no documented population (sockeye salmon on the oregon coast for example).
As for how long it takes for a population to take hold I'm not sure. But I have read about salmon populations getting completely wiped out by landslides and recovering in 50 years or so, including the same adaptations (for example larger bodies for navigating a steep gorge) that the extinct population held. So potentially pretty quickly in the grand scheme of things.
I definitely agree with bush planes being pragmatic vehicles of utility, and are generally stripped down pretty bare. But I've heard more than one bush pilot refer to his plane as the SUV of the bush, generally these were larger planes like Beavers or a 206 though. Seeing a full size fridge placed sideways in Beaver (with the doors removed and the ends sticking out either side) and you'll see why that say that!
On theory I have heard relates to the fishing pressure in the North Pacifci Gyre. From what I understand Chinook and other anadromous species typically make one revolution per year (it's not uncommon for US born fish to be caught off Japan and Kamchatka). With an increase in fishing pressure fish just don't live as long any more without being caught. So the one, two, and three salt fish (two salt being a fish that has spent 2 years in the salt water), are more likely to pass on there genes. Being that how long a fish stays in salt water is largely genetic it would be easy to remove those genes from the gene pool in a relatively short time. I'm sure other factors like dams without fish passage on the Upper Columbia and Elwah (two rivers known for their large salmon) also played a factor.
Additionally fish hatcheries largely select for fish that return at a younger age as they will return in larger numbers, and with such a huge amount of hatchery fish that would further drive down the average size. As would any spawning between wild and hatchery fish (although the reproductive fitness of hatchery fish is particularly bad).