Catholics are obligated to not eat "meat" on Ash Wednesday and Fridays during Lent. However, when used by Catholics, the term "meat" doesn't encompass fish. I remember being taught this, and I asked my grandmother, "But isn't fish a form of meat?" She then showed me a page from an explicitly Catholic glossary that defined "meat" as flesh that comes from land animals specifically, so it didn't include seafood at all. It's silly as hell to me that an animal living underwater somehow negates the "meat" property from its flesh when you consume it.