Yup.. it is RNG based on the level of fish you get like avatar.zero said. I went out and spent maybe an hour fishing and got 1x5* 6x3* 3x2* and like 10x1* so I think I got like 45 or so? Which was more than enough for a lot of wraps to last a few days.

Mossy bait is used specifically to catch troll head fish in the black forest.