This is especially puzzling because other tunas, most of which are far more migratory in nature lack such an organ. They travel and feed in waters as cold as 60 degrees and warm as 80 degrees. Yellowfin swim closer to the surface at night then they do during the day. They average an hourly swimming speed of 8.4 feet per second. Scientific theory suggests yellowfin move up and down in the water column searching for odor trails of baitfish and to help regulate their body temperature.
Migratory yellowfin make fewer vertical movements and maintain lower depths than feeding fish.
They demonstrate predictable swimming patterns that differ between night and day. Yellowfin can navigate via a magnetic based sensing organ located in their skull. They are able to know their exact position relative to fixed objects or topography 10 miles away. Late in the afternoon, they move away from their reference point or landmark and begin a circular and sometimes twisting searching pattern at an average of 5 knots from their starting point. By dawn, they are already at, or enroute to their starting point or landmark.