Shark fin soup: Scientists now can tell which kind of shark

NEW YORK (Aug. 23) – The growing demand for shark fins – the main ingredient in shark fin soup – is driving many shark species toward extinction, in part because international regulators lack a cost-effective means of determining which species the fins are actually coming from … until now, that is. Researchers from the New York-based Wildlife Conservation Society (WCS), working with partners from Nova Southeastern University, have developed a reliable genetic test that will identify shark species from their fins alone, taking a bite out of the massive uncertainties inherent in protecting these vulnerable marine predators. Their results are published in the recent issue of the journal Conservation Biology.

"We have developed an efficient way to achieve accurate and rapid identification of shark body parts, including dried fins," says Mahmood Shivji, one of the co-authors of the paper.

While commercial fishing fleets have targeted many shark species for some time, the recent popularity of shark fin soup in Asian markets is driving an upsurge in the number of sharks caught. To conserve onboard space for more valuable species and maximize profits from shark catches, many commercial fishing boats simply cut off a shark's fins – a practice known as finning – and toss the mortally wounded fish back into the ocean.

The new test uses a common genetic amplification method known as polymerase chain reaction, or PCR, to identify six species of shark commonly caught in North Atlantic waters: blue, dusky, porbeagle, silky, and longfin and shortfin makos. These sharks are sought after in the global fin market, and are also frequently caught as bycatch in tuna and swordfish fisheries.

Using samples from 33 species of closely related sharks, researchers were able to identify the six target species with near 100 percent accuracy. The test proved effective for dried fins as well as fresh samples. Shivji and his colleagues can now identify up to 10 species with genetic testing, and plan to be able eventually to test for 35 species of commercially exploited shark. The difficulties in identifying species solely from their fins have resulted in a near total lack of catch data needed for effective regulation. This kind of tool will be especially useful in monitoring whether any protected species, such as the basking shark, are being traded in violation of regulations. More broadly, being able to identify fins to species may encourage better recordkeeping on how many sharks of which species are being caught, and this will facilitate a clearer understanding of whether populations are threatened.

"This new identification method has big implications for shark fisheries and trade monitoring," said Dr. Ellen K. Pikitch, director of WCS's Marine Program. "Conservationists will finally be able to get a glimpse into the impact that high seas fisheries are having on wild shark populations. Further this test can serve as a model for a wide array of conservation dilemmas involving wildlife products that are difficult to identify."

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