Whaleshark Movement Patterns Revealed
A new study has revealed complex movement patterns of whalesharks which included dives to up to 1,928m
Using satellite tags, a team of researchers found that whalesharks in the Gulf of Mexico use the shallow waters as expected but also spend periods of up to three days at depths greater than 50m.
Whalesharks are mostly observed feeding near the surface and little is known about their use of deeper waters. Between 2003 and 2012 the research team attached satellite tags to 35 whalesharks off the Yucatan Penisula and another three whalesharks off Florida in 2010.
The data gathered by John Tyminski from Mote Marine Laboratory in Florida and colleagues from the US and Mexico, showed that whalesharks feeding inshore changed their behaviour abruptly in the mid-afternoon when they undertook regular vertical dives.
Offshore, whalesharks were recorded to spend 95 per cent of their time at 500m or deeper, with the deepest dive recorded being 1,928m. Nearly half of these dive profiles showed brief intervals at about 475m which the researchers interpreted as foraging events.
'As the world's largest fish, the filter-feeding whale shark does not blindly vacuum the sea for food. On the contrary, these sharks show dynamic vertical movements patterns that likely evolved as an efficient means of getting the most out of planktonic prey patches both near surface and at great depths,' co-author of the study Dr Tyminski notes.
The study also found that whalesharks can remain at depths of more than 50m for more than three days continuously.
Researchers assume that shifting ocean conditions are responsible for the complex movement patterns.