Residualized
Residualized is a term used for anadromous fish that remain and reside in their natal stream instead of migrating into the ocean during their adult phase. For example, a percentage of juvenile steelhead remain in the river instead of undergoing smoltification in spring. These juvenile steelhead then become residualized and live as adult rainbow trout in rivers. Residualized fish can interbreed with their anadromous version when they return to spawn.