Minnesota DNR and the University of Minnesota, have done a DNA study on Brook Trout in SE Minnesota (Driftless Area).
Study has revealed that the "Native Brook Trout" strain has outlasted the "Stocked Brook Trout" strain (from Maryland)!
The Maryland Brook Trout, look identical to the Minnesota Brook Trout, but their DNA is different. Which explain why, that there were no Maryland Brook Trout found in the streams that were not Hatchery Released.
Brook Trout released stopped decades ago, but no Maryland Brook Trout were discovered in the research. This has broad implications to other policies of the DNR for restocking area waters, with fish stock not from the same watershed.