Whale shark populations off Ningaloo Reef in western Australia appear to be thriving despite active tourism there, according to a new study published in the January issue of the Ecological Society of America's Ecological Applications.

The study - done by an Australian marine scientist and an American computer programmer and astronomer - used computer-assisted photo identification to determine whether whale sharks were returning each season to Ningaloo. Whale sharks, the world's largest fish, have distinctive white lines and spots along their flanks, so the researchers used photos of the animals and fed them into a computer program that could identify each as individuals.

The scientists found that more whale sharks are returning to the northern area of Ningaloo Marine Park each season - which generally runs from April to June - and that two-thirds of the sharks photographed had visited the reef before. The researchers surveyed 5,100 images taken by scientists, divers and tourists as part of their study, nearly 10 times as much data as used in any previous survey.

West Australian marine scientist Brad Norman, one of the paper's authors, said the apparent growth of the whale shark population in Ningaloo indicates that well-managed eco-tourism can provide local communities with income while still preserving important habitat.

"Applying these guidelines to other locations along whale shark migration routes may offer a viable alternative to hunting these fish, one that yields both economic and conservation benefits," Norman said.