As of 2006, two subspecies are named, each with distinct physical features and vocalizations. The northern fin whale, "B. p. physalus" (Linnaeus 1758) inhabits the North Atlantic and the southern fin whale, "B. p. quoyi" (Fischer 1829) occupies the Southern Hemisphere. Most experts consider the fin whales of the North Pacific to be a third, as yet unnamed subspecies—this was supported by a 2013 study, which found that the Northern Hemisphere "B. p. physalus" was not composed of a single subspecies. The three groups mix at most rarely.