Hubble Software IDs Rare Fish
NINGALOO, Western Australia, Dec. 31, 2007 -- Pattern-recognition software originally developed for the Hubble Space Telescope is helping marine biologists and conservationists study the largest fish in the world, the whale shark, through photographs and videos.
The whale shark, known as the "gentle giant" for its nonpredatory behavior, can be up to 20 meters long and weigh as much as 20 tons. The fish has a broad, flattened head and minute teeth. It eats tiny zooplankton, sieving them through a fine mesh of gill-rakers.
The whale shark, the largest fish in the sea, is a gentle giant that allows humans to swim quite close, allowing marine biologists and even tourists to help study the creatures by photographing the white lines and spots along the flanks of the animal, a unique pattern that serves as a "fingerprint" of each whale shark. (Photo: ©Brad Norman)
Listed as a rare species, relatively little is known about whale sharks, which live in tropical and warm seas, including the western Atlantic and southern Pacific. However, a new study combines computer-assisted photographic identification with ecotourism to study the rare species and suggests whale shark populations in Ningaloo are healthy. The study appears in the Ecological Society of America’s January issue of Ecological Applications.
Brad Norman, a marine scientist in Western Australia, founded Ecocean, a nonprofit association registered in Australia for conserving the unique marine environment. He began the whale shark study in 1995. Photographs were taken while swimming alongside each whale shark and photographing or videotaping the white lines and spots along the flanks of the animal.
Norman teamed with US computer programmer Jason Holmberg and astronomer Zaven Arzoumanian of Universities Space Research Association/NASA in Greenbelt, Md., who adapted software originally used with the Hubble Space Telescope. The pattern-recognition software developed by Holmberg and Arzoumanian allowed the group to positively identify individual whale sharks. Like a human fingerprint, the speckles and stripes pattern on the skins of whale sharks are believed to be unique to each individual.
The whale shark eats tiny zooplankton, sieving them through a fine mesh of gill-rakers. Unlike the megamouth and basking sharks, the whale shark does not rely on forward motion but can hang vertically in the water and "suck" food. (Photo: ©Brad Norman)
Ningaloo Reef, in Western Australia, is one of the best locations to find whale sharks, especially between April and June. The authors found that more whale sharks are returning to the northern area of Ningaloo Marine Park from season to season, suggesting the population is growing. In addition, they found that about two-thirds of the sharks were repeat visitors while one-third were sighted only once during the study period.
The authors said their study suggests that the management guidelines for whale shark ecotourism at Ningaloo appear to be on target.
“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.
As a rare and highly migratory fish, whale sharks are a big draw for Ningaloo’s ecotourism industry, where visitors pay to get close views and even swim with the sharks. In spite of their gargantuan size, whale sharks are fairly docile; the main risk comes from getting in the way of their very large and powerful tails.
The whale shark measures up to 20 meters long and can weigh as much as 20 tons. Divers can be seen on the fish's left for a size comparison. (Photo: ©Brad Norman)
Based on 5100 underwater images contributed by hundreds of researchers, divers, and ecotourists, the authors obtained almost 10 times more data than any previous study.
“To study whale sharks in a meaningful way, we really had to rethink how we collect data and how we analyze it,” said Holmberg. “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.”
Norman and colleagues note that while their study is encouraging for the Ningaloo whale shark populations, global concern over their future is justified, especially in areas where the sharks continue to be hunted for their fins and meat. The researchers hope others will apply their techniques to other whale shark populations, as well as to other species.
For more information, visit: www.whaleshark.org
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