March 28, 2012
A Case Of Misidentification: Two Sharks Could Be Endangered
Confusion of identity between two shark species may threaten the survival of both. A new and unnamed shark species originally discovered off the Eastern United States seaboard discovered by Nova Southeastern University Oceanographic Center (NSU-OC) has a cousin that shares a striking resemblance: The endangered scalloped hammerhead shark.
In an article published in the April 2012 issue of the scientific journal Marine Biology, scientists have revealed the new look-alike species to be found as far south as the coast of lower Brazil, more than 4,3000 miles away. This confirms beliefs of the new species´ widespread population. This also means the look-alike species could face the same environmental pressures as its scalloped hammerhead cousin, who is currently being fished unsustainably for its prized fins.
As tens of millions of sharks are being killed for their meat globally, the shark population has seen a sharp decline, prompting international protection efforts to protect the sharks and reduce unsustainable fishing.
“It´s very important to officially recognize, name and learn more about this new hammerhead species and the condition of its populations through systematic surveys,” Shivji says. “Without management intervention to curtail its inadvertent killing, we run the risk that overfishing could eradicate an entire shark species before its existence is even properly acknowledged.”
The new species was discovered by Shivji´s team in 2005 as they were examining the DNA of sharks they mistook for the endangered scalloped hammerhead. A research team from the University of South Carolina then independently confirmed the new species in 2006.
By combining the genetic evidence from both the NSU and South Carolina research teams, it is believed at least 7% of sharks thought to be the Scalloped hammerhead are actually the new, look-alike species. This means the overall population of the scalloped hammerhead shark is smaller than previously estimated. The endangered shark is currently being reviewed by the US National Marine Fisheries Service to determine if it should be listed as “threatened” or “endangered” under the US Endangered Species Act. The International Union for Conservation of Nature and Natural Resources (IUCN) has already listed the scalloped hammerhead on the “red list” of endangered species. The new species, however, isn´t on either list.
“We hope that during this important scalloped hammerhead status review, the new look-alike species will be recognized, and possible impacts of historical mix-ups between the two species on past scalloped hammerhead stock assessments will be considered,” says Shivji.
The reduction of either of these species could upset the delicate balance in the oceans ecosystem. One prior study offers a warning for what could happen if the overfishing of the hammerhead is not stopped: A large reduction of sharks off the US east coast has been associated with a large increase in population of their biggest prey, the cownose ray. The cownose ray was responsible for overeating the bay scallop, which in turn cause a steep reduction in supply for scallops in the fishing industry.
Researchers hope this new study will help them protect not only both species of shark but also the delicate oceanic ecosystem in which they live.
Image Caption: Sphyrna lewini (scalloped hammerhead shark) Copyright: Save Our Seas Foundation/Peter Verhoog