Plastic bottles on fishing nets reduce dolphin bycatch by 88 percent

A simple, low-cost intervention using discarded materials is showing promise in reducing the accidental death of marine mammals. Researchers at Newcastle University have demonstrated that attaching empty plastic bottles to gillnets can decrease dolphin bycatch by 88 percent. This development offers a potential lifeline for cetacean populations, as gillnets — often made of thin, acoustically invisible nylon — frequently trap dolphins and porpoises that are unable to detect the barrier through their natural echolocation.

The solution functions as an acoustic reflector. Because dolphins rely on sound waves to navigate and hunt, the air-filled cavities within the plastic bottles create a distinct echo when struck by a dolphin's sonar. This signal effectively acts as an early warning, allowing the animals to perceive the otherwise stealthy nets and navigate around them. According to findings published in the journals Fisheries Research and Marine Mammal Science, this method does not interfere with the ability of fishers to catch their target species, a factor deemed critical for ensuring the widespread adoption of the practice.

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Testing and Implementation

The research spanned several years, with trials conducted in diverse marine environments. In early studies, researchers monitored over 1,600 deployments in Zanzibar, Peru, and Brazil. While the results varied, with surface-set nets showing less efficacy, potentially due to ambient surface noise, the bottom-set gillnet fishery in Brazil yielded highly positive data. A subsequent study, which monitored 318 fishing trips between 2020 and 2025, confirmed the 88 percent reduction in bycatch.

Per Berggren, Emeritus Professor of Marine Megafauna Conservation at Newcastle University, emphasizes the dual benefit of the approach. Beyond the immediate impact on dolphin survival, the project repurposes plastic waste that would otherwise contribute to ocean pollution. The bottles are securely fastened to the nets, and trials indicated no loss of the materials during deployment. Ongoing research is now evaluating the scalability of this method in fisheries across Cambodia and the Congo.

Conservation Context

The challenge of gillnet entanglement remains a global crisis. Data from the World Wildlife Fund indicates that bycatch is the single largest cause of mortality for small cetaceans, with hundreds of thousands of dolphins, porpoises, and small whales dying annually. In regions like the upper Gulf of California, such threats have pushed populations like the vaquita porpoise to the brink of extinction. In the United Kingdom, static gillnets are responsible for the highest number of marine mammal deaths among various gear types, leading advocacy groups to call for a transition toward safer, alternative fishing technologies.

Other mitigation efforts include the use of solar-powered LED lights, which have shown success in deterring sea turtles and some shark species, and have been tested to reduce dolphin bycatch in Peruvian fisheries. However, the plastic bottle method is highlighted by researchers for its accessibility and near-zero cost, making it a viable solution for small-scale fishers in developing nations who operate with limited financial margins.

Broader Implications of Plastic Waste

The reliance on plastic is paradoxical in the context of marine health. While upcycled bottles may help protect dolphins from nets, the accumulation of discarded plastic remains a systemic threat. Research published in the Journal of Cleaner Production highlights that coastal islands often serve as "traps" for international plastic waste carried by ocean currents. In many Latin American nations, the lack of robust waste-management infrastructure means that significant amounts of debris are carried downstream from urban centers to the coast.

Scientists note that the material properties of plastic are also being explored for technological advancements. Recent research, highlighted by the American Chemical Society, suggests that PET plastic bottles can be converted into high-performance carbon powder for use in supercapacitors. These components store and release energy for electric vehicles and electronics more efficiently than some traditional materials. While the technology is in its developmental stages, it reflects a growing scientific effort to treat post-consumer plastic as a resource rather than solely as waste.

What to Watch Next

• Scaling Trials: Expanded testing is currently underway in Cambodia and the Congo to determine if the 88 percent bycatch reduction rate remains consistent across different regional fisheries.
• Policy Integration: The Newcastle team is working with international agencies to encourage the formal adoption of bottle-based acoustic reflectors in global fisheries management policies.
• Commercial Development: Research into PET-based energy storage devices is moving toward potential commercial viability within the next 5 to 10 years, which could further incentivize the collection and proper handling of single-use bottles.
• Fisheries Transition: Advocacy groups continue to press for the phase-out of certain high-risk gillnet designs in favor of more detectable or alternative gear types by the end of 2026.