How do you get the Ghostfish in Stardew Valley?

How do you get the Ghostfish in Stardew Valley? The Ghostfish is a fish that can be acquired by killing ghosts in the dungeon or fishing in the underground lake at Mining Cave at level 20 or 60 with fishing level 3.

The Ghostfish is a fish that can be acquired by killing ghosts in the dungeon or fishing in the underground lake at Mining Cave at level 20 or 60 with fishing level 3.