When you try to enchant a fishing rod at a low level, you are given an option with no enchantment at all (not grayed out). The hover text is missing and clicking on it will give you back your fishing rod and reset the enchantments (i.e. new available enchantments), like when enchanting normally, however the fishing rod does not have an enchantment. When you are in survival mode it even takes the levels the "enchantment" costs.