That's an interesting question: is the chemical itself a problem for the wild salmon? I doubt that the chemical itself, through exposure to wild salmon, would cause them a problem.
Where there may be a problem is in the effects on the food web of wild salmon, because the chemical is toxic to crustaceans. That includes copepods that live in the zooplankton and are an important component of the diet of juvenile wild salmon. If the chemical residues in the environment are sufficient to affect those copepod populations, then that could lead to a decline in the food resource for wild salmon.
However, this is all speculation. No one has done this work.