We have an example of a river where the fish were left on their own to repopulate a section of river with fish passage restored. That is the Cedar, Approx 12 miles of river and 8 miles of creeks.

After building fish passage around the Landsburg Dam, every fish was trapped and DNA sampled, etc. The wild kings and coho were on their own. The interesting part of the experiment is wild kings mating with hatchery strays actually out produced the WXW pairings in recruits.

The sample size was small however, so maybe not enough to be conclusive. This needs more study as similar results are happening elsewhere with king salmon.

The kings and coho are increasing in number but nothing gangbusters. The steelhead in that river are pretty much gone. As a biologist explained it to me, the migrating lifestyle lost out to the stay in the river lifestyle. The rainbows in the Cedar are genetically identical to the steelhead, they just don't migrate to the ocean.

The kings prefer the main channel and the coho are taking up residence in the small feeder creeks. There is a lot to be learned here.

The river is open to C&R a few months a year.