They do have baked and fried fish if I recall. I don't remember what kind it was. They may have a few other items on the buffet on the ships that were mentioned, but it has been awhile since I've been on either one. It certainly isn't much if they do.
The best thing is to go to the main dining room for dinner if you want seafood. They will post the menu for the night outside of the dining room every day.
is a link to some sample menus for the main dining room.