Why was a 'Bay Area foundation' referenced yet left nameless? I never understand the logic behind this convention..
Sometimes anonymity is a condition of the gift.
Do they artificially reintroduce the salmon once access is restored or does that “neighbourhood” of salmon somehow survives and keeps trying every year ?
Salmon hatcheries also artificially boost the quantity of salmon in the stream.
If a salmon hatchery released salmon at the base of a dam, when the fish return and the dam was now gone, they'd just keep going.
However, there's more to it than this, because dammed rivers lacking salmon hatcheries have seen salmon runs start once the dams are removed.
I don't think the old adage that salmon will only return to their original spawning grounds is the whole story.
Some percentage will just enter a different stream. Straying could be a genetic strategy, imperfect behavior, accidental, or some mix. And they're not all necessarily distinct; e.g. the genetic strategy might simply work by reducing accuracy in locating the original spawning ground.
Consider that even before humans streams and rivers would naturally be dammed, diverted, or otherwise change in a way that made it more difficult or impossible to reach the original spawning ground. What would be interesting is if the ratio of various phenotypes, like those that effect straying, has changed in response to the ecological upset caused by humans.
Stocking can give it a faster kickstart though
What I really love about the fish under discussion here is, for a long time they had no clue why some rainbow trout became steelhead, and some didn't. (They still don't know 100%) Such an interesting story, and a regular rainbow and a steelhead just seem almost like another species - different size, behavior and even taste when you eat them.
This will benefit Kokanee Salmon, a kind of salmon that spends all its life in fresh water and does not migrate to salt water like most salmon.
In Lewis Creek, they currently have access to only 1/2 mile of the creek, but in 2021 there were about 1000 of them returning (from Lake Sammamish) to spawn.