Many shark populations throughout the world face continued, massive declines. These are driven largely by the popularity of shark fin soup, which has created a highly lucrative but unsustainable market for shark fins.
Shark conservation in the U.S. and worldwide to counter these declines requires comprehensive management and trade monitoring. However, this has not been possible because little reliable information is available on the population structure of most shark species.
Initially, this shark forensics work focused on identifying microsatellite and mitochondrial DNA markers that would function effectively like a barcode for smooth hammerhead sharks (Sphyrna zygaena), whose fins are in especially high demand, the scalloped hammerhead (Sphyrna lewini) and the endangered porbeagle shark (Lamna nasus). The team has since expanded to work with tiger, great hammerhead, grey reef, and night sharks.
The researchers have been able to identify multiple markers by working with tissue samples from hundreds of sharks collected around the world. They then demonstrated that, using these unique markers they could in fact determine the species and population of origin for shark fins in a Hong Kong market.
Initial results revealed that for scalloped hammerhead fins, markets draw from global sources, with a significant number of fins taken from imperiled western Atlantic stocks. The work also provided the first information on global population structure for the porbeagle and smooth hammerhead, and expanded understanding of the scalloped hammerhead population. A side result of the work was the surprising discovery that some sharks can resort to non-sexual reproduction when mates cannot be found, for instance as a population shrinks.
By enabling managers and others to identify the source of market fins, the DNA markers work will enable population specific global shark management and allow the U.S. management community to play a leadership role such efforts.
Shivji’s work has received extensive national and international media coverage, and a description of the research is now a permanent part of the Smithsonian Museum of Natural History’s new Ocean Hall.