Actually my mother (age mid 70s) who grew up on a farm has said to me many times over the years her family only ate meat on Sunday. They were not vegetarians or some weird cult it was the way people were it was a normal way to eat.

Traditionally or historically (?) fish isn't seen as meat. And not just for religious reasons. My guess is people saw them as so different from land animals they were not classed as meat in the minds of our ancestors.