Currently trying to do the Ixal Dragonhead fishing daily for Snow Smelts, and I figure, since Crayfish Balls only ever give Gobys or Smelts here, then using Surface Slap on the Goby should guarantee a Smelt on the next hook, right?

Unfortunately not. It seems fishing doesn't even register the possibility of getting a quest fish until you actually hook a fish, because when you Surface Slap a Goby away, trying to fish again simply gives you an error saying that there's no suitable fish for your bait.

Given that I just fished up a couple dozen Gobys this time around, real bad luck run trying to get my Smelts, it'd be really nice if Surface Slap worked for these fish, particularly since Snow Smelts and Tangle Skippers share a pool with only one other fish with Crayfish Balls