Ah, one-handed implements. These are probably the most unique category of weapons in the game. Some are purely cosmetic. Others, like the aptly named Slapper Fish, have incredibly low combat damage. These are also all one-handed, which means they can be overlaid on any one-handed weapon except for spears. I don't know exactly why, but I expect it has to do with both the animations and how spears are held. Lore-masters will find the same problem with their staves, despite eventually learning how to dual wield. Two-handed weapons users will also find they can't use these either.
If you're interested in these, they make for home hilarious outfits. Imagine dual-wielding Breads of the Third Age or the Giant Flower! And, as usual, if there's another way of obtaining anything you see here, let me know in the comments.