Whale shark population visiting Ningaloo thrives

Science Alert Australia 21 Dec 07;
ECOCEAN

The population of whale sharks visiting Ningaloo, Western Australia, appears to be healthy according to the results of a new, twelve-year study in the upcoming issue of the international journal Ecological Applications*.

The study contradicts previous findings of declines in the Ningaloo population and presents a new approach to analyzing the species. With many global reports finding shark populations in decline, these results provide a glimpse of hope.

"The study suggests that the management practices at Ningaloo are working for the whale shark", said Rolex Awards for Enterprise Laureate and marine biologist Brad Norman. "It is vital that this knowledge be made available to other parts of the world already undertaking or embarking upon whale shark conservation and eco-tourism projects."

Mr. Norman says global concern over the whale shark's future remains justified because of apparent declines in places where whale sharks are still hunted for their fins and meat and in view of sharks' slow population recovery rates.

Cutting-edge software was used to collect data for long-term monitoring, analysis, and management of this local aggregation of one of the world's rarest creatures. The study incorporated 5100 underwater images contributed by hundreds of researchers, divers and ecotourists.

The Ningaloo study forms part of a broader, global project analyzing the vulnerability of the deep sea giant to extinction. Population models based on the photographs, which represent almost ten times more data collected than any previous study, indicated a modest increase in the number of whale sharks returning annually to the northern area of Ningaloo Reef from 1995-2006.

The study also demonstrated the robustness and reliability of computer-assisted photo-identification in combination with ecotourism as a new way of studying populations of rare and endangered animals at a relatively low cost. The marine environment is expensive to research, and this type of collaborative 'citizen science' is a cost-effective, achievable way of better understanding the seas.

"To study whale sharks in a meaningful way, we really had to rethink how we collect data and how we analyze it. We began our work from the ground up, building our own tools on a tight budget and designing our study to be collaborative from the start." said Jason Holmberg, a programmer and author on the study. "The results surpassed our expectations, allowing hundreds of individuals to contribute and providing the necessary data to obtain a closer look at the population's health. This model can be cross-applied to a lot of other research areas."

The study was started in 1995 by West Australian marine scientist Brad Norman. His US colleagues Jason Holmberg and Dr Zaven Arzoumanian adapted astronomical software (originally developed for use with the Hubble space telescope) to recognize the unique pattern of spots on the skins of individual whale sharks. This technology was used recently to identify the 1000th whale shark from over 12,000 photos collected by a global research network, a remarkable feat for so rare an animal.

The project received international recognition with a Rolex Award for Enterprise in 2006.

The authors of the study also discovered that approximately two-thirds of the sharks visiting the reef every year are returning after previous visits. However, the remainder passed through the study area without further resighting, suggesting that some sharks swimming the reef may only be short-term visitors.

Despite the encouraging news from Ningaloo, the authors of the study caution that little is still known about the habits of the giant fish, especially when it is in open ocean or down deep. Their ongoing work may hold a few more surprises. "This study is the tip of the iceberg for whale sharks. Every time we look at the data, we ask more questions. That's the real joy of exploration." says Dr. Arzoumanian.

Whale shark numbers increase at Ningaloo
The Age 25 Dec 07;

The future for the gigantic whale sharks of the Indian Ocean looks good, according to the results of a recent study.

The 12-year study, published in the journal Ecological Applications, contradicts previous findings that the Ningaloo whale shark population, off the coast of Western Australia, is in decline.

Murdoch University marine scientist Brad Norman believes the population increase is a result of good environmental management in the region.

"The study suggests that the management practices at Ningaloo are working for the whale shark," Mr Norman said.

Mr Norman, along with US colleagues Jason Holmberg and Dr Zaven Arzoumanian, analysed 5,100 underwater images contributed by hundreds of researchers, divers and ecotourists between 1995 and 2006.

The researchers used astronomical software (originally developed for use with the Hubble space telescope) to recognise the unique pattern of spots on the skins of individual whale sharks.

Population models based on the photographs indicated a small increase in the number of whale sharks returning annually to the northern area of Ningaloo Reef during the past 12 years.

The authors of the study also discovered that approximately two-thirds of the sharks visiting the reef every year are returning visitors.

The use of donated images, coined "citizen science", allows members of the public to contribute to the research effort via the project's Ecocean website (www.whaleshark.org).

"It's great to give people a sense of involvement in the project. You don't have to be a professor to become involved," Mr Norman said.

Mr Holmberg said taking in contributions from the public helped expand the study without adding to its cost.

"To study whale sharks in a meaningful way, we really had to rethink how we collect data and how we analyse it," Mr Holmberg said.

"The results surpassed our expectations, allowing hundreds of individuals to contribute and providing the necessary data to obtain a closer look at the population's health. This model can be cross-applied to a lot of other research areas."

The report's authors believe the whale sharks still face pressure from places where they are hunted for their fins and meat, and due to their slow population recovery rates.

They said little was still known about the habits of the giant fish, especially when it was in open ocean or deep below the surface.

"This study is the tip of the iceberg for whale sharks," Dr Arzoumanian said.

"Every time we look at the data, we ask more questions. That's the real joy of exploration."

© 2007 AAP

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