I think the "bad strain" part is one of the parts that is uncertain. The genes are coming straight from wild fish. The question is what effect, if any, the hatchery raising process has on the genes getting passed on from Snider fish.

The potential problem as I understand it is that a greater proportion of the "less fit" genes are the ones surviving the hatchery process to head out to sea and return as Snider fish, whereas the "more fit" genes survive the wild spawning environment.