So far as wild rainbows in Appalachian watersheds go, while it is true that the majority of fish are spring spawners, there are also fair numbers of autumn spawners.
Over 20 years ago, while fishing in the Harper Creek watershed in the Pisgah NF in western North Carolina, I ran into a NC fisheries biologist on his day off who was also fishing. We go to talking and he told me that many of the wild RT pops. in the state had both spring and fall spawners. He said that hatchery engineering of the original stock (these wild pops almost all came from Federal fish) produced fall spawners to begin with. He said that once in the creek and established, some of the fish reverted to spring spawning. Others though, stayed fall spawners. He said they did not know why this was so, but that 2 possible factors were, the competition by brown trout and stream gradient. He said that they had noticed that the stronger the brown trout pop. in a given stream, the more likely the RT were to revert to spring spawning.
He also said that the higher gradient the stream, the more likely that RT which came from fall spawning stock were to keep spawning in autumn and not revert.
That's what he said anyway...
