I caught quite a few of these while I was skill up fishing in Qufim on the cliff to the left of the Jeuno entrance. I went from 54-65 fishing there, I need to fish more been busy with Alchemy lately.
I also caught one of these while fishing in Batallia Downs as a lvl 18 fisher + fishing gear. I was fishing with a Halcyon Rod and Minnow lure. That being said, I fished for 3 game days and only got one.