Northern bluefin tuna is a highly prized species of tuna found in the northern hemisphere. In the Pacific ocean, it is also known as the Pacific bluefin tuna. Other synonyms include Thunnus maccoyii, Thunnus orientalis, Thunnus thynnus orientalis, and northern bluefin. In Japan, it is referred to as hon-maguro or "true tuna," and is a highly sought-after ingredient in sushi and sashimi. The Atlantic bluefin tuna, which is also referred to as Thunnus thynnus, is a closely related species found in the Atlantic ocean. Despite its popularity, overfishing and illegal harvesting have led to dwindling populations, and the northern bluefin tuna is now considered a critically endangered species.