 Historical data suggests numbers were previously much higher; for example, in 1727, survivors of the "Zeewyk" shipwreck killed over 150 sea lions in the Southern Group alone.This has led to a 1727 population estimate of between 290 and 580 animals for the entire Houtman Abrolhos.Populations apparently fell dramatically between the 1840s and the 1880s, largely due to extensive commercial sealing in the area.