Tracking Shark Fins with ‘zip code’ DNA

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An international team of scientists, led by the Institute for Ocean Conservation Science at Stony Brook University, has used DNA to determine that groups of dusky sharks (Carcharhinus obscurus) and copper sharks (Carcharhinus brachyurus) living in different coastal regions across the globe are separate populations of each species.

Both are large apex predators that are heavily exploited for the shark fin trade, which claims tens of millions of animals every year to produce the Asian delicacy, shark fin soup. Many of these species are declining as a result of this fishing pressure for their fins.

The dusky shark is classified as “Endangered” in the Western Atlantic by the International Union for Conservation of Nature as its population is below 20 percent of what it was two decades ago. These new studies show that the genetic differences among populations of these sharks are large enough for scientists to be able to track the actual origin of the fins on sale in Asian markets, enabling better regional monitoring and management of these threatened predators.

These research findings appear in two scientific articles. “Global phylogeography of the dusky shark, Carcharhinus obscurus: implications for fisheries management and monitoring the shark fin trade,” has been published online in the journal Endangered Species Research. “Phylogeography of the copper shark (Carcharhinus brachyurus) in the southern hemisphere: implications for the conservation of a coastal apex predator” will soon be published in the journal Marine and Freshwater Research. The primary objective of these studies was to identify any genetic differences among regional groups of dusky and copper sharks and establish how many distinct populations there are. The second objective was to determine if these population differences were great enough to allow scientists to reconstruct their contributions to fin trade in the future. Like many large sharks, these species have a wide distribution around the globe but are tied to coastal areas for reproduction.

“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