Scientists Track Origins of Shark Fins Using DNA "Zip Codes"

sharks on ice photo

Photo by hewyk via Flickr CC

Part of the reason enforcing restrictions and bans on shark finning is so difficult is that it is nearly impossible to trace where shark fins landing in stores and restaurants came from. Without knowing the source, it's hard to put the smack down on illegal finning. However, that might change with a new method for using the "zip code" found in shark DNA, which helps researchers know exactly what part of the coastline a fin came from. Stony Brook University reports that a team of scientists led by the university's Institute for Ocean Conservation Science has figured out that dusky sharks and copper sharks -- both heavily hunted for their fins, with the dusky shark species classified as threatened by the IUCN -- have distinct populations living along different areas of coastlines. By looking closely at the "zip code" embedded in the DNA of the fin, the researchers can pinpoint from which population that shark came, and therefore get a step closer to finding out who is exploiting the species.

"By analyzing part of the genome that is inherited solely through the mother, we were able to detect differences between sharks living along different continents - in effect, their DNA zip codes," said Dr. Demian Chapman, leader of the research team and assistant director of science of the Institute for Ocean Conservation Science. "This research shows that adult females faithfully give birth along the continental region where they were born. If fished too much, the population will collapse, and it is extremely unlikely that it will be replenished from immigration of sharks from another region."

Because different shark species have varying habits for birthing and traveling, it is not necessarily possible for this strategy work across the board for sharks and tracking down the origin of fins. However, for specific species that tend to stay in certain areas as a distinct population, the new research presents a flicker of hope. Dr. Chapman pointed out that sampling programs for fins traveling to Asian markets must be established so that researchers and conservationists know which populations need the most assistance.

...The once common dusky shark is now rare and a species of concern for listing under the Endangered Species Act. At one time, these animals were common in ocean waters off the United States; however, a recent stock assessment of the sharks along the U.S. East Coast and in the Gulf of Mexico showed an 80 percent decline even though they have been protected since 2000. The recovery of the species is extremely slow because the average age of maturity is 20 years, its reproductive cycle only occurs every three years - including a two-year pregnancy - and its litter size is relatively small (three to 14 offspring).

The story of the dusky shark species has become frighteningly common. There is little to no discrimination shown among species when it comes to finning. Even the most iconic species, like Great Hammerheads and Great Whites, are at risk of disappearing entirely if the demand for shark fins, used primarily in shark fin soup, is not slowed or stopped.

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