Whale Sharks Can Be Identified using Astronomical Star Pattern Recognition Program

The largest fish in the world, whale sharks, are at risk of extinction. Earthwatch volunteers in Australia working with marine biologist Brad Norman will apply a new computer algorithm, adapted from one used by astronomers to recognize star patterns, to identify individual whale sharks and help in their conservation.

Computer software developed by astrophysicists to locate stars and galaxies in the night sky could help save the whale shark—whose spotted skin patterns are like a starry sky—from extinction, according to new research published in the Journal of Applied Ecology. The unique product of an interdisciplinary collaboration will be used this summer by Earthwatch volunteers working in Ningaloo Marine Park, Western Australia, to "virtually tag" individuals and chart their movements.

Australian marine biologist Brad Norman and information architect Jason Holmberg, both of ECOCEAN, worked with astrophysicist Dr. Zaven Arzoumanian of the Universities Space Research Association and NASA Goddard Space Flight Center to develop the computer software. They discovered that a pattern-matching algorithm developed by astronomers to locate celestial objects could be used to identify individual whale sharks. Whale sharks' characteristic white spots are analogous to bright stars in the night sky, allowing the trio of researchers to adapt the star pattern recognition technique to their spot patterns.

"Photo-identification has been used for the flukes of whales and also animals such as leopards, zebras, cheetahs, and giraffes," said Norman, principal investigator of Earthwatch's Whale Sharks of Ningaloo Reef project. "Some computer-aided matching has been attempted, but I am not aware of anything as high-tech or ground-breaking as this."

"This is an example of space technology finding an important application here on Earth," said Arzoumanian.

Whale Sharks are the largest living fish on Earth, yet there were less than 350 confirmed sightings of these gentle giants prior to the mid-1980s. Although they are found around the world in tropical and warm seas (except the Mediterranean), whale sharks are uncommon and are threatened by unsustainable fishing practices in some regions. They are listed as "vulnerable to extinction" by the World Conservation Union (IUCN).

A major hurdle in the conservation and management of whale sharks has been the absence of accurate data on their population biology and movements. Photographic identification was attempted before, but the unmanageable task of making visual identification in large data sets made it impractical. This breakthrough in identifying individual spot pattern "fingerprints," by automating the pattern-matching process, will help fill that gap.

Once photographed, the technique means a whale shark has been "virtually tagged." According to Norman: "Identifying individuals repeatedly through photography can also inform biological observations such as age of maturity, growth rate, and foraging ecology."

For instance, a recent report by the BBC (http://news.bbc.co.uk/2/hi/science/nature/4620960.stm) based on diver observation suggests that whale sharks at Ningaloo Reef are smaller than in previous years. Norman intends to track the growth of individuals using advanced in-water measuring technology, adding vitally-needed data to this issue.

Earthwatch teams working with Norman and Holmberg on the Whale Sharks of Ningaloo Reef project, starting in April 2006, will be applying the new technique to individually identify whale sharks at a significant congregation area on the coast of Western Australia. Volunteers will be taking identifying photos of the whale sharks' spots, as well as monitoring their behavior relative to other divers and collecting samples of plankton, the whale shark's food resource.

The authors have devoted their own time and resources to set up the ECOCEAN Whale Shark Photo-identification Library to act as a single repository for whale shark photographs taken by divers and tourists, acting as "virtual research assistants," as well as researchers. The library went online in 2003 and currently reflects almost 1,500 whale shark encounters, representing 400 sharks, from people in 27 countries around the world.

"The implications of this computer-aided identification technique and web-based photo library for management and conservation of whale sharks may be profound," said Norman. "The Library will enable us to gain better insight into the numbers of whale sharks that are surviving in the wild." With additional information about the population size, structure, and movements of whale sharks, it will be possible to know how to direct conservation efforts and whether marine reserves are effectively protecting them.

Earthwatch Institute is an international nonprofit organization that supports scientific field research by offering members of the public unique opportunities to work alongside leading field scientists and researchers. Earthwatch's mission is to engage people worldwide in scientific field research and education to promote the understanding and action necessary for a sustainable environment. 2006 marks the 35th Anniversary of Earthwatch Institute.

More information on ECOCEAN is available at http://www.ecocean.org

To learn about volunteering on Whale Sharks of Ningaloo Reef, go to http://www.earthwatch.org

For more information, see Zaven Arzoumanian et al (2005). An astronomical pattern-matching algorithm for computer-aided identification of whale sharks Rhincodon typus. Journal of Applied Ecology 2005, 42: 999-1011. The article is published online at http://www.blackwell-synergy.com/doi/full/10.1111/j.1365-2664.2005.01117.x

The finding was recently highlighted in the January 10, 2006 issue of the journal Current Biology 16 (1): R3-R4.