salt and pepper disease.
yes the perch in William lake do have the salt and pepper disease
the pepper or host parasite lives the the flesh of the host.
salt is the natural enzyme the host or fish produces to fight the parasite
the fish is safe to eat if u cook it properly but can have a gritty texture to it.
that was one reason bass were introduced into William lake to eat all the perch rather than trying to kill them all and harming the brown trout.