February 14, 2013 | 4
What do the world’s biggest fish and the Big Dipper have in common? Believe it or not, the answer is math. One of the same algorithms developed to help astronomers study the stars in the sky is being used to conserve and understand whale sharks (Rhincodon typus) under the sea.
It turns out that each whale shark has a unique pattern of spots located behind its gills. By studying photographs and videos of whale sharks—often taken by vacationers—and running those images through the algorithm, scientists can identify individual sharks and track them as they swim through the ocean.
The idea dates back to a paper published in the Journal of Applied Ecology in September 2005 which showed that algorithms first developed by astronomers to study images from the Hubble space telescope could be used to identify individual whale sharks with 90% accuracy. Scientists had previously done this task manually, a slow and time-consuming process that this algorithm partially automates (scientists need to straighten and crop the photos before feeding them into the system).
The nonprofit wildlife conservation group Ecocean put the idea to use and launched the online Whale Shark Photo-ID Library, where people around the world can upload their whale shark photos and other sighting information. To date, more than 43,000 photos have been collected, providing information on more than 3,800 individual whale sharks. Citizen scientists who participate get emails letting them know if the shark they photographed is new to the collection or if has previously been identified. Then they receive additional emails every time the same shark is sighted.
The project got an extra boost recently when a new paper, published October 24 in Wildlife Research, affirmed the effectiveness of the algorithm as compared to manual identifications. Researchers downloaded photos and videos from Flickr and YouTube and were able to identify individual whale sharks up to 85 percent of the time. According to lead author Tim Davies, a PhD student at Imperial College London, this means photographs taken by tourists and posted publicly can be of use by scientists and conservationists. “Hopefully, this will give whale shark research around the world confidence in using this source of free data,” he said this month in a prepared release. “In the Maldives in particular, where whale shark tourism is well established and very useful for collecting data from throughout the archipelago, our results suggest that whale shark monitoring effort should be focused on collecting tourist photographs.”
I don’t know about you, but right now I want to buy a wetsuit and hop on a plane to the Maldives.
Of course, whale sharks are found in many locations besides the Maldives. They have a fairly large territory, including stretches of the Atlantic, Pacific and Indian oceans at various times of the year. But despite their size—which can reach 10 meters or more—it hasn’t always been easy to track them or to figure out where the big fish go when they migrate. A new review paper published January 29 in the Journal of Fish Biology looks at a number of previous studies—including genetic evidence, satellite tracking information, and photo-matching—and hypothesizes that there is a broad level of connectivity between the world’s whale sharks and includes a model suggesting that all of the animals are, in fact, part of a global meta-population.
The authors, from the University of Adelaide in Australia and other institutions, say understanding of whale shark migration patterns can help to identify possible mating and breeding sites that could require conservation efforts and even predict how the species will adapt to warming oceans and a growing threat from humans.
High Fashion vs. Soup?
Yes, despite the potential eco-tourism benefits of whale sharks, the big beasties are in danger from something I have written about here many times before: the capturing of sharks and cutting off their fins for use in the Chinese delicacy known as shark fin soup. Although whale sharks are not seen as one of the primary drivers in the shark fin trade, a paper published last March in the Journal of Fish Biology identified the trade as “an emerging crisis” for the species and suggested that whale sharks are increasingly targeted for their fins.
All of which brings us, oddly enough, to fashion. Last November wildlife and fashion photographers Kristian Schmidt and Shawn Heinrichs took two female models underwater to photograph them alongside several massive whale sharks. The striking photographs are intended to call attention to the threats whale sharks face and to raise money for the conservation organization WildAid.
The photos were taken in the Philippines, another whale shark eco-tourism destination. As Heinrichs writes on his Web site: “Just a [sic] two years ago in these very waters, divers discovered a live juvenile whale shark that had all its fins cut off. Though legally protected in the Philippines, poaching of whale sharks had continued because the shark fin traders enticed poor local fishermen to earn money from exploiting these vulnerable animals. Less than a decade prior, the local populations of whale sharks had been all but wiped out to satisfy demand for shark fins in China. Now finally, local communities have found a way to earn a living from whale shark tourism, and rather than targeting and killing them, they now are passionate about protecting them.” The photographers point out that some conservation groups oppose the whale shark tourism, but it is providing essential income for a community recently devastated by a typhoon.
Whale sharks are listed as “Vulnerable to Extinction” on the IUCN Red List of Threatened Species, although most researchers agree that further research is necessary to determine their true population status. This recent work goes at least part of the way toward answering that question.
Photos used under Creative Commons license