If you are a Catholic who lives your faith in public (as every Catholic should), you are likely to be asked this week a question along these lines: Why do you eat fish but not meat? Or, perhaps, you may be asked this question: Isn't fish a kind of meat? Unfortunately, many Catholics do not know how to adequately answer these questions.
This is a topic about which I have written several times before (Feb. 27, 2015, Feb. 27, 2009, and Feb. 15, 2008). I won't go through the lengthier explanations today - you can read those again on your own if you wish - but I will remind you of a very good and simple reason why we can eat fish but not meat on the Friday's of Lent and Ash Wednesday.
This reason comes from John Myre (about whom I know nothing more) in his Liber Festivalis, which he wrote in the late fifteenth century:
For when God, for Adam's sin, cursed the earth and the land, he cursed not the water; wherefore it is lawful for a man to eat in Lent that which cometh out of the water.
Catholics, then, are allowed to eat fish because it is a sign of God's mercy.