An advanced method for tracking animals has indicated that 18 whale sharks have visited the Gulf of Eilat in the past two years, exceeding researchers' earlier estimates, according to which only three or four sharks visited during this period.
Whale sharks are the largest species of fish in the world.
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An individual whale shark that has come to the site for at least two consecutive years was also identified in the course of the tracking, which was conducted between May and September this year and last. These figures contradict the researchers’ earlier estimates according to which only three or four sharks visited during this period.
The whale shark, one of the most impressive visitors to Israel’s coasts, received its name due to its size and because it tends to swim close to the surface of the water like a whale. Although usually 12.5 meters in length, one measured 20 meters and weighed 34 tons.
Whale sharks eat plankton (marine organisms) and are not dangerous to humans. Their distribution is worldwide but doesn’t include the Mediterranean. They are an endangered species threatened by fishing vessels and commercial boats that cause injury and death.
The new data was gathered by Sharks in Israel, an NGO for protecting sharks and batoids (cartilaginous fish known as rays). Over the past six years, the organization has coordinated observations of cartilaginous fish from all over Israel with the public’s help, mainly through the “Whales in Israel” Facebook group.
The Israel Nature and Parks Authority have also observed the shark.
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Anyone filming the movement of the sharks is requested to do so without interfering with their movement and while maintaining a distance of at least three meters.
Over the past two years, Sharks in Israel requested that people send them any video footage they've captured of whale sharks. Footage was then verified by Wildbook, a website started by scientists that uses an algorithm to identify animals, by analyzing and comparing footage submitted from around the world. Whale shark are identified by their scars and white spots.
Sharks in Israel collected 58 filmed observations of whale sharks in the Gulf of Eilat and used 14 to identify 12 distinct sharks. The NGO noted that there are possibly more sharks that were not identified.
“The films come not only from the Nature and Parks Authority, but also from divers or people who were in the Gulf and identified a whale shark,” explains Sharks in Israel head Adi Barash, a doctoral student at the University of Haifa who studies sharks. “The same was done in other parts of the world, with people asked to film the left side of the shark so [that] we can identify them.”
Shir Bar, a volunteer in the organization, was the one who marked the arrangement of white spots on the whales’ bodies and analyzed the findings that led to identification. Bar, who relied on the Wildbook methods, also analyzed films from last year and identified additional individual sharks. This analysis led the NGO to the discovery that there were a total of 18 visitors to the Gulf of Eilat over these two years.
The sharks that arrive in Eilat and the Red Sea seem to be young. Barash believes that in adulthood they move elsewhere. But there is still not enough information about the identified sharks to know where they go from here.
Despite the NGO’s work, information about the whale shark's habits and schedule is quite limited. Scientists hope that databases, like that of Sharks in Israel, will provide valuable insight by keeping tabs on the species.
In the meantime, scientists also rely on information collected by means of transmitters attached to the sharks’ bodies. Saudi scientists have attached such transmitters to several sharks and plan to widely disseminate such information. Israeli and Saudi researchers overcome difficulties in cooperation that have existed until now.