Title pretty much says it all.

fishbringer displays when pole equipped. Never disappears.

Comment out (add two dashes to the beginning of each line) or delete lines 306 and 309 in fishy.lua to make it appear when you equip fishing pole and disappear when you unequip it. /fb show will toggle it to always be on if you should change your mind and want it to behave that way again instead. You may need to do that once to get it in the right state if it doesn't work after making the edit.