The fin whale (Balaenoptera physalus), also called the finback whale, razorback, or common rorqual, is a marine mammal belonging to the suborder of baleen whales. It is the second largest animal after the blue whale, growing to 27.3 metres (89.6 feet) long and weighing nearly 74 tonnes (73 long tons; 82 short tons).ike all other large whales, the fin whale was heavily hunted during the twentieth century and is an endangered species. Over 725,000 fin whales were reported taken from the Southern Hemisphere between 1905 and 1976, as of 1997 survived by only 38,000.