The plural of ox is not oxes. It's oxen. So wouldn't it make sense to say foxen? What about moosen? Because it's not goosen. It's geese. Would it be meese? Do you Canadians hunt deer or Caribou? And fishes is a verb. Sheepen?
Actually I found this question interesting. I like words. That being said, one has to love the interwebs for instantaneous answers to obscure questions.