The Basques, among other things, were the first European whalers. In the Middle Ages, it seems a particular whale type now known as the Right Whale was very common in the Bay of Biscay. We now know these creatures as Right Whales, because they were the "right" whales for later fishermen--they were slow swimmers, and their bodies floated. This made them favored prey in the later 18-19th Century whaling era.
Around the 11th Century, many of the Basque communities along the coast found that these whales were very profitable to slaughter when one occasionally was beached. The blubber could be boiled down for lighting fuel, and the meat could be eaten. These accidental strandings were so advantageous, the Basques took to taking boats out to try to drive whales into shallow water. If noise and threatening advances forced the whale to beach, it could be killed with lances.
By the 12th Century, this was a highly organized business. Stone watchtowers were built, and when a whale was sighted, the alarm would be sounded, and everyone would head out after it. As many as 20 villages would combine to slay a single whale, sharing the rewards, except for the tongue, which went to the church as a favored delicacy.
This became so important that at least six Basque towns have whales or whaling as a feature of their coats of arms. Later, the whales were hunted more actively, and would be killed at sea with harpoons. In fact, harpoon is from the Basque word arpoi. Several other whaling terms have Basque origins.
The Basques began searching far out at sea for the whales. Whether this was because the whales became scarce in the Biscay area, or simply because whaling was so profitable isn't clear. The Basques almost completely monopolized European whaling until the 1500s. The only other area in the North Atlantic where Right Whales are found frequently is in the Western Atlantic, near the coast of Newfoundland. Apparently the Basques found this area, but kept it a closely guarded secret. At first, even whales killed at sea were towed to shore to be cut up, and have the fat boiled, but later this was done at sea, despite the obvious hazard of fire on wooden ships. The Basque also began fishing for Cod, and salting it at sea during this time.
Eventually the British and Dutch got into whaling. But even they usually had Basques as "experts" on their ships for many years. Eventually, many Basques gave up whaling in favor of privateering, which they found more profitable.
The only other people who were doing this early on where the Norse. The colony in Iceland was particularly active and Bergen, Norway, was early on a major whaling center. But they never were as important commercially as the Basques.