Around 24 to 28 species of cetacean roam through the Azores, making it one of four places in the world where most species of this infraorder occur. Starting in the mid-19th century and ceasing in 1984, whaling (especially of sperm whale) heavily exploited this diversity. Beginning in the early 90s, whale watching quickly grew to popularity and is now one of the main economic activities in the Portuguese archipelago.