New environmental DNA test could help rare hammerhead sharks fight extinction

A groundbreaking test developed by an FIU scientist can detect small, elusive hammerheads without anyone ever setting eyes on them — a critical new tool for species fighting for survival.

This first-of-its-kind test can detect traces of the sharks without ever catching or disturbing them. Like faint biological echoes lingering in the current, the test reveals where the sharks have been by identifying fragments of genetic material left behind in the water. In a recent study published in Frontiers in Marine Science, FIU marine biologist Diego Cardeñosa, who is affiliated with FIU's Institute of Environment and the Global Forensic and Justice Center, demonstrates the test’s effectiveness, showing how it can help scientists locate and protect these endangered species.

Small-bodied hammerhead sharks like the scalloped bonnethead, scoophead and Pacific bonnethead have been pushed to the brink by overfishing, leaving so few that scientists have struggled to study them. With their lives and habitats largely unknown, conservation efforts have fallen behind — until now. Cardeñosa’s new environmental DNA (eDNA) test could change the fate of these critically endangered sharks.

“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 believes these hammerhead sharks were once abundant. They inhabit shallow, remote coastal habitats where scientific monitoring is limited and fisheries management is weak. Colombia’s Uramba/Bahía Málaga National Natural Park, the site of his research, may be one of the last refuges where researchers can still find them.

“You can drop a hook and line there and, within 10 minutes, catch one or two of these species,” he said. Elsewhere, sightings are nearly nonexistent: the scalloped bonnethead was last recorded in Mexico in 1994, and the scoophead in 2007. In Honduras, one of these species was only recently discovered after decades without a trace.

“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.” 

For Cardeñosa, the urgency goes beyond ecosystem roles.

“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 research not only raises awareness of these overlooked species but also sparks curiosity about how powerful this new method can be.

“It’s fascinating that you can take a simple water sample and know whether a species was there or not,” he said.

With such a vast range to cover, the data provide critical information on where to focus protection efforts and how to maximize impact. The science can also help more than just hammerheads. Once the water sample is collected and DNA extracted, that information can be stored in a lab for years. So if future scientists want to study another species that might have lingered in the area, the DNA will still be there.