Two whale sharks documented by WA researchers for the past 22 years are believed to be the longest studied individual wild sharks in the world.
Stumpy and Zorro have been photographed making their annual pilgrimage to Ningaloo Reef since 1994 by Brad Norman and David Morgan from the Centre for Fish and Fisheries Research at Murdoch University.
They are easily identifiable by the shapes of their tail fins, and the researchers estimate Stumpy and Zorro to be at least 40 years old, suggesting they could continue visiting WA for another two decades, given the species are thought to live to about 80 years old.
Dr Norman said the studies were helping he and Associate Professor Morgan understand when whale sharks first matured and became reproductively active.
"Based on photographs on the shape and length of the claspers, which are the paired external reproductive organs of whale sharks up to 60cm long, Zorro first reached maturity in 1998 and Stumpy in 2001," he said.
"Our longitudinal studies have also revealed when Zorro and Stumpy became sexually active, as evidenced from scarring on the claspers, which for Stumpy has been since at least 2005."
Whale sharks are the largest known fish species and have recently been listed as endangered by the International Union for Conservation of Nature.
Female whale sharks can give birth to litters of 300 pups, however, neither mating nor pupping has been observed with Stumpy and Zorro.
Dr Norman said the two fish may have fathered many offspring, and ongoing research would involve satellite tracking to find where the mature animals migrated to and, ultimately, where breeding occurred.
"Identification and protection of these critical habitats will be imperative for the long-term conservation of this remarkable species," he said.
