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CSI Shark.

Scientists work to protect species using DNA detective work, writes Ocean Correspondent, Cheryl-Samantha Owen

Millions of shark fins are sold at markets each year to satisfy the demand for shark fin soup, a Chinese delicacy.

But up until now it has been impossible to pinpoint which sharks from which regions are most threatened by this trade.

However, new, groundbreaking DNA research has traced scalloped hammerhead shark fins from the burgeoning Hong Kong market all the way back to the sharks' geographic origin. In some cases the fins were found to come from endangered populations thousands of miles away.

Published online in the journal Endangered Species Research, the findings highlight the need to better protect these sharks from international trade. The work was led by the Save Our Seas Foundation Shark Centre and the Guy Harvey Research Institute.

"Although we've known that a few million hammerhead shark fins are sold in global markets, we now have the DNA forensic tools to identify which specific hammerhead species the fins originate from, and in the case of scalloped hammerheads, also what parts of the world these fins are coming from," said Dr Mahmood Shivji, senior author on the paper and Director of the Save Our Seas Foundation Shark Centre and Guy Harvey Research Institute (GHRI), both at Nova Southeastern University in Florida.

The work shows the scalloped hammerhead fin trade is sourced from all over the globe and so must be globally tracked and managed.

Using CSI-like methods known as "genetic stock identification" or GSI, scientists analysed fingernail-sized DNA samples from 62 scalloped hammerhead shark fins that had been obtained in the Hong Kong fin market.

By examining each fin's mitochondrial DNA sequence (a section of the genetic code passed down by the mother and traceable to a shark's regional birthplace) the researchers were able to exactly match 57 of the 62 fins to an Atlantic or Indo-Pacific ocean origin.

The team analysed sequences taken from 177 live scalloped hammerheads in the Western Atlantic and determined the species is further divided into three distinct stocks in this region: northern (US Atlantic and Gulf of Mexico), central (Belize and Panama), and southern (Brazil). The scientists traced 21 per cent of the Hong Kong fins back to these Western Atlantic stocks.

Scalloped hammerheads in the region have been categorised as endangered by the IUCN (International Union for the Conservation of Nature) since 2006. This coastal species appears to have collapsed in the western North Atlantic and Gulf of Mexico.

"This type of DNA forensic testing of fins will be an incredibly useful tool to prioritise areas for conservation and ensure sharks aren't wiped out by excessive fishing," Dr Shivji said.

The new GSI technique takes DNA testing to the next level. It has been used to trace fish, sea turtle and marine-mammal catches back to their geographic origin. This study marks its first use with sharks. Dr Shivji is now working on developing GSI for more shark species, including other large hammerheads.

"We need to stop the drive to extinction that many shark species are currently facing. "These techniques give us essential and

otherwise unavailable data on exploitation levels, which will help to manage and protect hammerheads as well as many other species of sharks," said Chris Clarke, Director of the Save Our Seas Foundation.

Deadly delicacy

Shark fin soup originated in China and is considered a delicacy. It is consumed in countries throughout the world, although the main consumers of the soup are still in South East Asia.

Often the rest of the shark is discarded after being "finned" and left, immobile, to die a horrible death.

An estimated 100 million sharks are killed annually in this way. Research suggests that if the practice continues, many species of sharks could become extinct within ten years.

Besides the impact to the shark population, wildlife experts say 'finning' also harms other marine life by disrupting the ecosystem.

One of the reasons it is so rampant is that consumers do not know the implications of shark finning. It is also not common knowledge that the actual shark fin has little flavour and is mixed with chicken broth when making the soup.

Shark finning is currently controlled by the United Nations Convention on the Trade of Endangered Species of Flora and Fauna (CITES), which has been accepted by more than 150 countries around the world.

However, many countries are still not part of this agreement.

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Publication:7 Days (Dubai, United Arab Emirates)
Date:Jun 30, 2010
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