Diving at dawn and dusk help tuna to navigate with internal compass

London, August 24 (ANI): A new study has suggested that tuna dive fast and deep twice a day, namely around dawn and dusk, because they use an internal compass to navigate.

It has long been known that tuna dive around dawn and dusk but no one has been quite sure why.

According to a report in New Scientist, to find out, Jay Willis at the University of Tasmania in Hobart, Australia, and colleagues attached tags to 21 southern blue fin tuna and used them to monitor water temperature, time, depth and light levels for 135 days.

The team found that the tuna initiated these "spike dives" when the sun was precisely 6 degrees below the horizon, 30 minutes before dawn and 30 minutes after sunset.

At this time of day, magnetic interference created by the solar wind is at its lowest.

Since some fish can detect and navigate using magnetic fields, Willis thinks that diving at this time may help tuna to get a clearer magnetic signal.

As surface wind and waves also cause interference, Willis suggests that they dive deep to "fine-tune their personal compass". (ANI)