https://www.scientificamerican.com/article/whale-food-could-feed-the-world/

“The whale’s example shows that we can reap vastly increased returns from the biological economy of the oceans. The 270 million tons of krill on which the Antarctic whales fed in their heyday would be more than enough to supply the annual requirements of the entire U.S. population. There are growing indications that krill may be a timely subject. Some 250 ships and 16,000 men—the largest whaling fleet in history—are now operating in the Antarctic Ocean. They depend mainly on the fin whale. If and when this species follows the blue and humpback whales into near-extinction, whalers may find it worthwhile to turn their attention to krill.”

—Scientific American, January 1958