TUNA dive fast and deep twice a day because they use an internal compass to navigate, a new study suggests.
It has long been known that tuna dive around dawn and dusk but no one has been quite sure why. To find out, Jay Willis at the University of Tasmania in Hobart, Australia, and colleagues attached tags to 21 southern blue fin tuna (Thunnus maccoyii) and used them to monitor water temperature, time, depth and light levels for 135 days (Behavioral Ecology and Sociobiology, DOI: 10.1007/s00265-009-0818-2).
The team found that the tuna initiated these “spike dives” when the sun…
