DNA traces shark fins to American waters

A new DNA-based study has shown that many of the hammerhead sharks that are butchered to feed Asian demand for shark-fin soup start their lives in American waters.

According to a report in National Geographic News, the researchers traced finds from the scalloped hammerhead shark species-collected at the world's biggest fin market in Hong Kong-back to rare populations in the Atlantic and Indo-Pacific oceans.

The trade in shark fins supplies Asian markets with the key ingredient in the luxury dish shark-fin soup.

The practice claims up to 73 million sharks annually, including up to 3 million hammerheads. The finless fish are usually tossed back into the ocean to die.

Because the vast flow of shark fins to global markets usually operates in secret, conservationists have been left in the dark about where the sharks are killed.

Governments can't control the trade if they don't know how many sharks are being taken from their waters.

The shark-fin market is "like this big Wild West show (that) no one is monitoring," said study leader Demian Chapman.

But, the new DNA technique, which Chapman worked on at Nova Southeastern University, may be a tool for controlling the shark trade.

Chapman and colleagues took small tissue samples from 62 hammerhead fins at the Hong Kong market.

The team then ran a DNA sequence of a particular part of the shark's genome and compared it to a "map" of hammerhead DNA sequences culled from global research efforts.

The results showed that 57 of the 62 Hong Kong fins had come from sharks in either the Atlantic or the Indo-Pacific.

21% of the 57 fins had originated on sharks from the western Atlantic-including the Gulf of Mexico and the North American Atlantic coast as far south as Brazil.These populations are considered endangered by the International Union for Conservation of Nature.

According to Chapman, finding so many sharks from the depleted waters of the western Atlantic surprised the team, and it suggested that overfishing is still a problem in the region.

"Sharks are declining rapidly worldwide, and losing the top of the marine food chain could have vast repercussions for the rest of the ocean-and even us," Chapman said.

Also, the sharks' decline is disturbing because shark species have existed on Earth for nearly five million years, Chapman added.

"I don't think anybody wants to be part of a generation that's snuffed out an animal that's been in the oceans that long," he said.