For Christians, why isn't seafood considered meat? Because it's not red meat? During Lent can I eat?

Traditional Catholicism excludes fish because it was such a staple of life in ancient times. Red meat was considered a luxury, and that is why it is given up. Way back when red meat was not allowed at all during lent. As far as other seafood, that is kind of in that gray area, it almost qualifies as fish but it isn't fish. It is more a factor of convenience that most of these items are allowed because of today's lifestyle.