There are two competing whaling rules:
Iron-holds-the-whale: a whale belongs to the first ship to lodge a harpoon in it, provided that ship remains in active pursuit of the whale.
Fast-fish, loose-fish: a whale belongs to the first ship to harpoon it, but only while it remains physically attached to that ship. If it breaks free, any ship may claim it.
For the purposes of this debate, the year is 1701.