Shivji and Clarke have developed six tests that tease out a species-specific stretch of shark DNA that serves as a molecular ID tag.
Commercial fisheries that hunt sharks for meat gut them at sea and remove the heads, tails, and fins, leaving just the carcass, or "log," which makes the fish easier to freeze.
The process removes the distinguishing characteristics that make it possible for fishery enforcement officials to identify species in the wholesale markets, said Margo Schultze-Haugen, a biologist and fishery management specialist at the National Marine Fisheries Service, based in Silver Spring, Maryland. Some genetic testing is done but only on a very limited basis.
Shivji and Clarke's new genetic tests are improved versions that allow testing for six species of shark "all in one tube": blue, dusky, porbeagle, silky, and long- and shortfin mako.
"A quick, cheap genetic test that enables us to recognize individual shark species will facilitate good fisheries management," said Schultze-Haugen. "It will also help us enforce fishery closures, quotas, and minimum-size requirements."
Most importantly, the tests can be done using dried or fresh shark body parts. Shivji tested the procedure on dried shark fins from Asian and Mediterranean markets.
Of the 400 species of shark worldwide, about 50 are found in the global markets. But statistics are meager, because most countries don't have the resources for fisheries management. Harvest estimates range from 80 to 150 million sharks per year.
Sharks could be particularly vulnerable to overfishing. They grow slowly, produce few offspring, and take between two and 18 years, depending on the species, to reach sexual maturity.
Hong Kong, the world's shark-fin center, handles about 50 percent of the market, said Clarke. Singapore ranks second.
Clarke investigated the shark-fin trade while living in Hong Kong. Fluent in Mandarin, she was able to operate among the Hong Kong residents, who mainly speak Cantonese.
She visited warehouses where dried fins are sorted, and persuaded the owners to let her take small samples for her and Shivji's genetic studies. She wanted to understand the shark-fin market categoriesfor example, whether Chinese names correlate with certain species.
For two months Clarke enjoyed open access to shark-fin auctions at the warehouses, where she recorded prices. Then, as it happened, conservationists visited Hong Kong and showed films of finning. A backlash from the shark finning community resulted, and the warehouses blacklisted Clarke.
"Apparently they made a poster of me that said, 'Don't talk to this woman,'" Clarke said. But Clarke had already completed the research for her thesis. She and Shivji continue the work that may help regulate the shark-fin market.
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