As far as i know forge doesn't provide a hook where a fishing rod is casted (altough a hook is provided to handle the catch of fish/loot). It depends on what you are trying to achieve...a way you could go about this is to check for when a FishingBobberEntity joins the world (that would mean a rod has been casted). You can do this by listening to the EntityJoinWorldEvent and checking if the spawned entity is an instance of FishingBobberEntity