Blue whale hunting is banned by the International Whaling Commission, and the blue whale is listed as endangered by the IUCN Red List of Endangered Species and the U.S. Endangered Species Act as of 2014. Other conservation efforts include monitoring populations by satellite tags and shipboard observers.
Because of their size, blue whales were not targeted by whalers until the late 19th century, when the deck-mounted harpoon cannon was invented. From then until the IWC ban on hunting in 1966, blue whale populations decreased 70 to 90 percent. Illegal hunting continued to occur until the late 1970s, but from then until 2014, there has been no commercial hunting of blue whales, except for isolated incidents.
Apart from hunting, blue whales face threats such as ship strikes, entanglement in commercial fishing gear, noise from oceangoing vessels and habitat degradation due to pollution and global warming. Satellite tagging helps researchers learn whale routes to avoid confrontations with vessels and fisheries. Observers in areas of widespread fishing and ship traffic help avoid collisions and entanglements. The use of acoustic pingers helps ward off blue whales and other marine mammals from fishing sites. Areas of ongoing monitoring and research include habitat degradation through pollution in areas of blue whale population, such as the St. Lawrence River area of the North Atlantic, and the melting of Antarctic ice due to global warming.