Minecraft wiki entry for Fish_farming, associated text: As with every other item with durability in the game, you can combine them in an Anvil or in your inventory to gain more durability. With Mending, a fishing rod will heal with ordinary use -- like other Mending tools, it will be healed if you gain experience in any way, while holding it in either your main hand or offhand... and of course it's in hand while you're gaining experience from fishing!