Pig spawners in the nether

I went to the nether in 1.10.2 to find a terrible surprise.In the the nether fortress, where all the blaze spawners were supposed to be, I discovered Pig spawners instead.So far, ever since the update, that is the only kind of spawner in my survival world that I saw in the nether.I wasn't using commands on that particular word.I know that the default mob spawner is one with a pig in it.Do you think that would have anything to do with it?