Unhygienix is out of fish, due to a strike of deliverymen from Lutetia. However, Getafix needs reasonably fresh fish for the magic potion. Asterix and Obelix volunteer to go fishing, and at sea immediately get lost in a storm. They end up in a strange land full of tan-skinned people with beads and feathers on their clothes. While they integrate with the natives well enough, the Gauls decide to leave when it becomes apparent that the chief wants Obelix to marry his daughter. They hitch a ride from a passing crew of Vikings, who decide that the Gauls are natives of this 'New World' and take them home as proof of their discovery, At the Vikings' village, Asterix and Obelix meet another Gaul named Castastrofix, a fisherman who was enslaved in a Viking raid. The Gauls escape, and return to the village with a fresh load of fish.
- Animated Adaptation: Used as the basis for Asterix Conquers America, released in 1994. However, it cut out the Vikings and included a secondary plot of Caesar wanting Getafix tossed off the edge of the world.
- Defeat Means Friendship: Asterix and Obelix are allowed to join the tribe after besting their best warriors.
- Every Episode Ending: Subverted; Cacofonix is present at the banquet, although Fulliautomatix is bashing him with his hammer to keep him from singing. Instead, Unhygienix is the one sitting under the tree, turning up his nose at a plate of fish being offered to him by his wife, Bacteria.
- Insane Troll Logic: The reason for the notoriously low quality of Unhygienix's fish is explained: He never fishes himself, he buys his wares from wholesalers who have certified it as high quality fish. The fact that the quality of the fish might drop when transported from Lutetia (Paris) to Armorica by oxcart over two weeks never occurs to him.
- Mistaken Nationality: Asterix and Obelix mistake the Native Americans for Cretans, then Iberians. The Vikings assume the two are Native Americans.
- Pass the Popcorn: When the latest fight over Unhygienix's fish breaks out, we see a Legionary patrol happily listening from outside the village, remarking on how nice it is when the Gauls fight each other for a change.
- Throw the Dog a Bone:
- As it is mostly set in either America or Scandinavia, this the only Asterix album from the Goscinny era in which not a single Roman is beaten up. Only two panels even feature any Romans, as a Roman patrol listens to the latest fight over Unhygienix' fish from just outside the village, happily remarking how nice it is when the Gauls fight each other for a change.
- The pirates appear, but since it's the captain's birthday, the Gauls refrain from sinking them. They do steal the entire birthday feast (except for a sausage), however.