How did Subb convince the captain of Bouton de Rose to release the dead whales?

The Pequod comes upon a French ship, the "Bouton-de-Rose." Starbuck asks about Moby Dick, but the sailor on the ship has not even heard of the notorious whale. The crew of the Rose-Bud has two whales that appear to have oil, but Stubb notices that one of the whales may have ambergris. Stubb concocts a plan in which he tells the captain of the Rose-Bud that his whales are useless and should be left behind lest they damage their ship. The captain of the Rose-Bud takes Stubb's advice ,and after the Rose-Bud departs from the Pequod, Stubb secures the whale carcass with the ambergris for the Pequod.