Yes, there is a bait for the fire ammonite which you can fish out from the schools, from the NPC you can summon via item gained by fishing in your garrison, or by buying it at the Auction House. It significantly improves your chances of fishing out the fire ammonites.
However, you don’t need the bait to fish them. Just search the lava pools all over Frostfire Ridge and find the schools you can fish from.