I got to love 4chan because it just reminds me the fact that I’m a catch, apparently.
Rooted from “plenty of fish in the sea” and fishings “catch and release” fishing. It’s common to have maximum catch limits while fishing, so you will release fish back into the water if you do not intend to keep it. A catch is anyone that you intend to hang onto, or state steadily. This user is saying they are valuable to date.