Photo credit: Marine Stewardship Council
Reviewing: Clark, Z.S.R., Miller, A.D., Sherman, C.D.H., Morris, S., Weeks, A.R., & Butcher, P.A. (2025). Improving white shark detection capabilities in an Australian bather protection programme using environmental DNA. Ices Journal of Marine Science, 82(4). https://doi.org/10.1093/icesjms/fsaf043
Sharks and Humans
Sharks are an incredibly diverse group with each species playing a critical role in maintaining the balance and health of marine ecosystems. As apex predators, sharks regulate the food chain by feeding on sick, wounded, and overabundant animals. This also prevents a population boom of any other species, which preserves natural ecosystem dynamics. Despite this important role, sharks are often met with fear, anger, and aggression from humans because of sensationalized negative interactions. As a result, regions with high rates of interactions between humans and sharks can suffer economically due to lack of tourism, face societal pressures against conservation, and deal with risks to human and animal life. Many of these regions around the world have implemented programs to reduce potentially dangerous interactions. Clark’s team takes a close look at bather protection programs in eastern Australia through a 14-month study analyzing the most effective methods for detecting sharks at popular swimming beaches.
Shark Detection Methods and eDNA Technology
The New South Wales (NSW) Shark Management Program in eastern Australia has utilized several methods of shark detection to minimize human-shark interactions. Historically, scientists chose to use remote sensing. While there are many benefits, these methods can pose physical harm to sharks or struggle under weather conditions like storms. The 2025 study asserts that the addition of environmental DNA (eDNA) technology would enhance shark detection and consequently protect swimmers and sharks alike. Scientists collected eDNA from water samples in the study region and analyzed it for genetic materials from the target shark species.
This technology is beneficial because it provides data on whether a shark species has been present without requiring visual identification of an individual. Researchers collaborating on Clark’s study conducted a 14-month study across three high visitation sites for white sharks in eastern Australia with the goal of comparing eDNA detections with detections simultaneously received from remote sensing. Ultimately, this comparison of methods would provide valuable insight into patterns of white shark presence and proximity to shore.
Figure 1: Map of sample locations from northern New South Wales. A: Lennox Head. B: Evans Head. Courtesy of Clark et al. 2025.
eDNA was collected weekly from three study sites (Figure 1: Lennox Head, Ballina, and Evans Head) over a 14-month period. Concurrently, long fishing lines were used to catch sharks that were then tagged with acoustic receivers. Researchers compared data received from eDNA with that received from remote sensing and fishing lines and assessed how well the data lined up. By the end of the study, eDNA technology produced 94 positive white shark detections from 209 samples. 110 white sharks were caught on fishing lines, and 102 of those were tagged with acoustic receivers.
Study Results and Conclusions
The results from Clark’s team’s study confirmed the previous knowledge that white sharks are more present in the cooler winter months of June-October. The study also found that less than 50% of the data between eDNA and remote sensing agreed. This means that over half of the days that eDNA was present in a region, there was no physical shark sighting.
The results from the study demonstrate that, while each shark detection method has benefits, a combination of multiple methods would most accurately predict shark movements and subsequently inform bather protection programs and protocols. eDNA is a novel technology that adds accuracy to shark detection, but visually identifying sharks is still crucial for emergency responses. In order to visually spot a shark, planes, drones, boats, or eagle-eyed lifeguards are necessary. Once a shark is seen, an alarm will sound or a color-coded flag will fly, alerting swimmers to clear the water until it is deemed safe again.
Figure 2: Shark warning sign at Pyramid Rock Beach, Oahu, Hawaii. Photo courtesy of Christine Cabalo.
The ocean is the sharks’ natural habitat, yet many humans dread interacting with them in the water. Sharks have become a symbol of terror, danger, and aggression because of fearmongering. However, if these bather protection programs are successful, the already low rate of shark attacks will lower even more. Hopefully, this will help swimmers understand that sharks are not hunting humans, and both species can coexist in the ocean.
I am a student in the Master of Oceanography program at the University of Rhode Island and enjoy scuba diving, boating, walking my dogs, reading, and being with friends and family.
