Whaling was the harvesting of whales by Humans for numerous purposes. This practice had been occurring on Earth for centuries. The people employed in this industry were called whale hunters. They went to sea in whaling ships. They hunted the whales with harpoons and flensed the whales with several cutting tools.
Whaling turned into a lucrative business in the 19th century. Within a century, the business saw tremendous advances in the hunting and processing of whales. A number of species, like the blue whales, were nearly driven to extinction, while other species, like the humpback whales, saw their numbers drop precipitously. Alarmed by this trend, several countries banned whaling. However, other countries and pirates continued hunting whales well into the 21st century. Sometime in that century, the humpback whales became extinct. (Star Trek IV: The Voyage Home)