[buttercakes]

Some inland rivers do import fish from other rivers to seed their hatcheries, but as an attempt to separate the hatchery and native runs based on run timing. E.g. steelhead from smaller coastal systems are used in lower Columbia tributaries in Oregon and SW Washington because they are genetically programmed to return and spawn in Nov/Jan and are generally gone before the native show up later in Feb/March. But this still creates artificial competition for resources once the fry from both runs have hatched.