Question
Why does fish have to be eaten separately from meat?
Answer
The Talmud teaches that it is dangerous to eat meat and fish together. The commentaries are not certain whether the Talmud refers to a physical danger or a spiritual danger, so they banned eating them together out of doubt. They may be eaten at the same meal, but traditionally they are separated by eating bread or some kind of food, and drinking something between the meat and fish.
Rabbi Ephraim Nisenbaum