A new test developed by a Florida International University (FIU) scientist offers a way to detect rare hammerhead sharks without needing to catch or observe them directly. The method, based on environmental DNA (eDNA), identifies genetic material left behind in water, revealing the presence of these elusive animals.
In a study published in Frontiers in Marine Science, Diego Cardeñosa, an FIU marine biologist affiliated with the Institute of Environment and the Global Forensic and Justice Center, demonstrated how this eDNA test can help locate and protect endangered hammerhead species. The technology is particularly significant for small-bodied hammerheads such as the scalloped bonnethead, scoophead, and Pacific bonnethead. Overfishing has drastically reduced their populations, making them difficult to study and hampering conservation efforts.
“Just by screening different locations along their distribution range from Mexico to Northern Peru, we can identify high-priority areas where conservation resources might be needed,” Cardeñosa said. “The short-term goal is to find these three species, as they’re likely among the most critically endangered coastal sharks in the world.”
Cardeñosa noted that these sharks were once abundant but now inhabit remote coastal habitats with limited scientific monitoring and weak fisheries management. His research took place in Colombia’s Uramba/Bahía Málaga National Natural Park, which may serve as one of the last refuges for these species.
“You can drop a hook and line there and, within 10 minutes, catch one or two of these species,” he said. He added that sightings elsewhere are extremely rare: “That’s how hard it is to find them,” Cardeñosa said. “It’s on us if we want to act to protect them or if we just let them slip away.” The scalloped bonnethead was last recorded in Mexico in 1994; the scoophead was last seen there in 2007; and only recently was one found in Honduras after decades without evidence.
Cardeñosa emphasized the broader importance of protecting these sharks: “A lot of these are some of the most derived or newest shark species on the evolutionary scale,” he said. “If they disappear, we’re also losing a piece of our planet’s evolutionary history. Extinction is forever, and that’s enough reason for me to do something.”
He hopes his work will raise awareness about overlooked shark species and demonstrate what eDNA testing can achieve: “It’s fascinating that you can take a simple water sample and know whether a species was there or not,” he said.
The eDNA data can guide protection efforts by identifying priority areas for conservation. The method also allows DNA samples collected today to be stored for future research on other aquatic species that may have inhabited those waters.
