The southern bluefin tuna (Thunnus maccoyii) is one of the largest bony fish in the world. The incredibly streamlined and powerful body is deepest near the middle of the first dorsal fin and tapers to a pointed snout. The lower half of the body is silvery white, whilst the anal fin is a dusky yellow colour. The tail is crescent-shaped and the first dorsal fin has a yellow or bluish hue.