The group of sharks they found were between 6 to 12 m in size, with most in the 7.7 to 9 m size range. The water in the vicinity of the sharks was apparently very turbid, a sharp contrast to the normally clear blue waters of the Gulf. On running a plankton net tow across the area the research team was surprised to find that the plankton comprised largely of fish eggs. Apparently there had been a large fish spawning event and the sharks were feasting on the resulting spawn.

Whale sharks had first been found feeding on fish spawn off the barrier reef in Belize but this discovery is probably the first report of such behaviour in the open water / pelagic environment.

Pop-up Archival tags have been widely used in whale shark research and used very successfully in Seychelles (see Sagren vol.2.4), where they revealed for the first time that whale sharks make dives to depths of over 1000m. The tags monitor depth, temperature and light intensity which they store in user definable time periods. At a pre-determined time the tags release from the animal, float to the surface and transmit the data to the research team through the Argos Satellite system.

The recovered data can then be used to find out more about the behaviour of the sharks with respect to their diving patterns and temperature preferences both during the day and during the night. The light intensity levels can be used to ‘geo-locate’ the sharks positions during the course of the deployment, using the time of dawn and dusk and a complex mathematical calculation. Thus although the PAT tags do not track the sharks they will be able to give some indication of the sharks location and travel.

The tags deployed in the Gulf of Mexico are scheduled to detach in October and the research team is eager to see what new information these tags will provide on the whale sharks of the Gulf of Mexico.