How to add a loot table to a custom fishing rod?

I have made a custom fishing rod (the baited rod) and I want to make it so that it fishes up extra fish. I have tried to do this with procedures by spawning items when fishing occurs, but this doesn't seem to work. I thought I could give it a custom loot table to do a similar effect, but I dont understand how I can assign a loot table to the fishing rod item.