In the realm of marine conservation, one of the most pressing and elusive challenges has been the detection and preservation of small-bodied hammerhead sharks, species that teeter dangerously close to extinction. Traditional methods of studying these sharks—such as direct observation or capture—have proven insufficient due to their rarity and the cryptic nature of their habitats. However, a revolutionary scientific breakthrough by a Florida International University (FIU) researcher promises to dramatically reshape efforts to monitor and protect these critically endangered creatures. This cutting-edge methodology harnesses the power of environmental DNA (eDNA) to detect the presence of hammerhead sharks without ever needing to physically encounter them.
Environmental DNA refers to genetic material shed by organisms into surrounding water bodies through skin cells, mucus, feces, or other biological sources. These invisible genetic traces disperse and degrade over time, but modern molecular techniques can isolate and identify them with remarkable precision. FIU marine biologist Diego Cardeñosa, affiliated with both the Institute of Environment and the Global Forensic and Justice Center, pioneered a breakthrough eDNA assay specifically designed to detect three notoriously elusive hammerhead species: the scalloped bonnethead, the scoophead, and the Pacific bonnethead. This innovation marks the first successful use of eDNA to monitor these diminutive sharks, whose populations have been decimated primarily due to overfishing.
The implications of this new diagnostic tool are profound. The ability to detectDNA fragments in water samples, effectively creating a biological map of the sharks’ recent presence, allows scientists to identify critical habitats along a vast geographic range extending from Mexico down through northern Peru. By simply collecting small water samples from coastal ecosystems where these sharks are suspected to persist, researchers can analyze the genetic markers and obtain real-time data about species distribution. This non-invasive approach is transformative, permitting study without disturbing the fragile, and often inaccessible, marine environments these sharks inhabit.
Hammerhead sharks have long been a significant component of coastal marine biodiversity. Yet, their populations have sharply declined due to overexploitation by commercial and artisanal fisheries. The three targeted species are small and inhabit shallow, remote, coastal waters where conventional survey techniques are often unfeasible. Consequently, the current data on their population size, distribution, and ecology has been sparse and unreliable. Cardeñosa’s environmental DNA assay fills this critical knowledge gap by allowing for a highly sensitive detection that does not rely on visual sightings or physical catches—which have become almost impossible due to their rarity.
One compelling case study for this eDNA technique is Colombia’s Uramba/Bahía Málaga National Natural Park, one of the last refuges supporting these hammerhead sharks. In this protected area, the populations are still sufficiently robust that a simple hook and line fishing attempt may yield one or more individuals within minutes—a stark contrast to surrounding regions where sightings have become mere historical footnotes. For example, the scalloped bonnethead has not been documented in Mexico since 1994, while the scoophead’s last confirmed record dates back to 2007. In Honduras, it took decades of absence before a recent discovery revived hopes for these species’ survival in that region.
Cardeñosa emphasizes the urgent need to leverage this environmental DNA technology to prioritize conservation areas effectively. By mapping out high-priority locations where eDNA assays detect the hammerheads’ presence, managers and policymakers can channel scarce conservation resources with greater precision and impact. This strategic approach could help prevent these sharks from slipping silently into extinction—a fate that is irreversible and, regrettably, common among overlooked marine species. The stakes are not only ecological but also evolutionary, as these hammerheads represent some of the most recently evolved shark species with unique genetic lineages worth preserving.
Beyond conservation implications, the scientific potential of eDNA sampling is captivating. Cardeñosa underscores how a simple water sample can yield a wealth of information about the aquatic species that inhabit or traverse an area, akin to uncovering “ghosts of the current.” Not only does this method circumvent many logistical challenges faced by field biologists, but it also preserves genetic material that can be stored long term. This archived DNA can serve as a temporal snapshot, enabling future researchers to explore biodiversity patterns or detect changes in species populations without additional fieldwork.
The development of this DNA-based surveillance tool has broader applications beyond hammerhead sharks. Since the process involves general DNA extraction from water samples, the methodology allows for retrospective studies of various marine organisms, including fish, invertebrates, and microorganisms. This flexibility positions environmental DNA as a game-changing asset in marine biology and conservation science, enabling a paradigm shift in how researchers monitor biodiversity in coastal and oceanic ecosystems on global scales.
Despite its promise, the environmental DNA assay is not without its scientific challenges. Precise quantification of population sizes and differentiation between closely related species requires meticulous calibration and validation. DNA degradation rates in different water conditions and potential contamination issues must be carefully managed. However, the pilot study published in Frontiers in Marine Science demonstrates robust sensitivity and specificity, showing that these technical hurdles are surmountable with rigorous protocols.
Ultimately, the advent of eDNA as a tool to safeguard critically endangered hammerhead sharks holds transformative promise in reconciling human fishing activities with marine biodiversity preservation. It allows scientists to peer into otherwise opaque marine habitats remotely and continuously, obtaining actionable data that can shape conservation strategies proactively. The story of these small, enigmatic hammerheads exemplifies how innovative molecular techniques can illuminate species and ecosystems on the brink of disappearing. As Cardeñosa poignantly notes, extinction is forever—and these invisible genetic footprints in the water may be humanity’s last hope to save some of the ocean’s most vulnerable inhabitants.
Subject of Research: Animals
Article Title: Ghosts of the current: environmental DNA assays to detect conservation priority areas for three critically endangered hammerhead sharks
News Publication Date: 14-Oct-2025
Web References: 10.3389/fmars.2025.1688088
Image Credits: Diego Cardeñosa
Keywords: Fish, Conservation genetics, Life sciences, Marine fishes
