Comment by metalman

salmon mostly prefer to return to there natal habitat, but there are a significant number of fish that are wanderers and colinists, so there are now salmon runs happening in far northern watersheds that have only recently become warm enough for juvinile fish. also, fish from clutches of eggs that are transplanted to streams with no fish, become native, which points to the homing instinct bieng re attached with each generation rather than hard coded geneticly, though that may happen in some sub species