I'm currently playing around with Unnamed Animal Mod as I want to make a showcase vid and can't find Humphead Parrotfish. After looking through the code for a bit I found the following in the checkFishSpawnRules function of the HumpheadParrotfishEntity class:

worldIn.getLevelData().getDayTime() < 12000 && worldIn.getLevelData().getDayTime() > 24000

As there is no number smaller than 12000 and bigger than 24000 that would mean the Humphead Parrotfish will never spawn.

To me that looks fishy (pun intended), but maybe I'm overlooking something.

Oh boy. I had this problem in game and fixed it, but must have reverted my commit. My bad, I'll try to fix it soon!