At up to 12.5 metres long the filter feeding whale shark is certainly big, but that doesn't make it easy to find.
Credit: iStockphoto/cdascher
PERTH: Perth-based scientists are trying to work out why females of the world's largest fish are shying away from Western Australia's Ningaloo Marine Park.
"Twenty to thirty years ago we knew nothing about whale shark migrations. [Renowned French oceanographer and explorer] Jacques Cousteau only encountered two in his lifetime," says Mark Meekan with Australian Institute of Marine Science.
Though adult males are frequently encountered around Ningaloo Reef today, experts still know little about the breeding and rearing habits of the species (Rhincodon typus).
Whale shark ecotourism is a thriving business in north Western Australia. Meekan hopes to sustain it at home, while spreading the message to third world neighbours who hunt the animal for food.
Spreading the word
"Even with only one village doing it, it would show there is sustainable income from whale sharks worth far more than the few cents a kilo they receive when they catch a shark and sell it," he said.
He has already tagged 55 whale sharks and photographed 500, but is none the wiser why females are so scarce at Ningaloo.
"About 80% of the sharks at Ningaloo are juvenile males, so Ningaloo Marine Park may be a nursery," he said. "Most shark populations are segregated, juveniles from adults, males from females and so forth, for good reason. Many shark populations are cannibalistic. So the juveniles, in particular, want to be somewhere else."
Research has already found that many whale sharks return to Ningaloo after swimming north as far as Java, Timor and Sumatra in Indonesia.
However – despite comparisons with photo libraries at Christmas Island, the Maldives, Mozambique and the Seychelles – no photographic data from Ningaloo been matched to other whale sharks in the Indian Ocean.
Tag tracking
In one instance a satellite transmitter worth US$3,000 was bitten off one of Meekan's tagged whale sharks. He says he had to send a student to retrieve it from a beach hut in West Timor.
"On Google Earth I was able to locate the hut it was still transmitting from, in the possession of a guy who found it hunting turtle nests. It cost us $300 to get it back, but the data was invaluable."
Already this season, with the help of ecotourism operators to tag and retrieve, Meekan has tagged 14 whale sharks at Ningaloo. "I intend to tag many more in the next two years," he says.
With support from the Western Australian Marine Science Institute, Apache Energy, CSIRO and the U.S. National Oceanographic and Atmospheric Administration (NOAA), the new project is hoped to open a new chapter into whale shark studies and their mysterious migratory patterns.
Follow Cosmos on Twitter!
twitter.com/cosmosmagazine
