How can upcycled bottles help save dolphins from fishing nets?

Discarded plastic drink bottles could hold the key to protecting dolphins from one of the ocean’s deadliest hidden threats – fishing nets. Our researchers have shown that attaching upcycled bottles to nets can dramatically reduce accidental dolphin deaths, while helping fishers maintain their catches.  

Contents:

1. Dolphins and the bycatch problem
2. A simple solution
3. Testing the bottles around the world
4. Further testing and future planning
   
   

Dolphins and the bycatch problem

The accidental capture of whales and dolphins in fishing nets and ropes is a worldwide problem.

Known as bycatch, dolphins and whales can’t easily sense nylon fishing nets, which are almost acoustically and visually imperceptible in the water. The creatures then become entangled in them and unable to escape.

A new report suggests that more than 1,000 porpoises and dolphins are dying in this way each year.

It’s acknowledged that sound-making devices, often referred to as ‘pingers’, can effectively reduce some dolphin and porpoise bycatch. They work by emitting sounds that alert echolocating marine mammals to the presence of the otherwise almost undetectable fishing nets.

However, their adoption by fishermen is not universal, partly due to costs, maintenance, and incompatibility with all types of fishing gear. There’s also the possibility that dolphins and porpoises will become used to the ‘pings’ made by the devices.

Dolphin caught in surface driftnet off Peru. Photo credit: @ProdDelphinus

A simple solution

Our researchers have been tackling the bycatch problem in an innovative way.

The team tested an idea, developed by Professor Per Berggren, Emeritus Professor of Marine Megafauna Conservation, to determine whether discarded glass and plastic drinks bottles could provide a simple, low-cost way to reduce bycatch while also giving waste materials a useful second life.

'This is a good news story and something that we strive for - a simple solution which benefits both dolphins and the fishers who use the gear.' - Per Berggren, Emeritus Professor of Marine Megafauna Conservation, School of Natural & Environmental Sciences

Two recent studies, published in the journals Fisheries Research and Marine Mammal Science, have shown that by attaching empty drink bottles to the nets, the team was able to reduce the accidental capture of dolphins in fishing nets.

Discarded plastic bottles with air inside attached to fishing nets acted as sound reflectors, while glass bottles with metal bolts inside produced a 'clinking' sound. Both of these devices helped dolphins detect and avoid the nets while allowing fishers to continue catching their target species.

Using the bottles in this way also has positive implications for re-using waste materials in a cost-effective way. During the trials, the bottles were securely attached to the nets and none were lost.

Fisher hauling driftnet with glass bottle pinger to help dolphins detect and avoid net entanglement. Photo credit: @ProdDelphinus

Testing the bottles around the world

It was vital for the team to test the set-up with different types of fishing equipment.

The first study was conducted on surface-set driftnet fisheries in Zanzibar and Peru, and bottom-set nets in Brazil. More than 1,600 fishing net deployments with the attached bottles were monitored and compared with standard nets.

In Zanzibar and Peru, plastic bottles increased targeted fish catches. However, neither glass nor plastic bottles reduced dolphin, porpoise, or turtle bycatch in the surface-set fisheries.

Contrasting results were observed in Brazil. Here, plastic bottles showed promise in the bottom-set gillnet fishery, potentially reducing dolphin bycatch while increasing fish catch.

'The difference we saw in the success of the bottom set nets compared to the nets near the surface, may be that the surface water is a noisier environment reducing the efficacy of the plastic bottle reflectors.' - Per Berggren, Emeritus Professor

Keen to build on this promising result in Brazil, the experts expanded that trial in a second study. Between 2020 and 2025, 318 fishing trips were monitored to compare nets fitted with plastic bottles to standard nets. They found that nets with the attached plastic bottles reduced dolphin bycatch by 88%, while catches of commercially important fish remained unchanged.

Workshop with fishers in Brazil - using upcycled plastic bottles to reduce bycatch of dolphins in gillnets. Photo credit: @Federoco Sucunza

Further testing and future planning

These findings suggest that using these upcycled bottles could be a low-cost and inclusive option for fishermen to reduce bycatch.

The team is eager to collaborate with governments and agencies around the world to encourage the adoption of this method, and help reduce marine mammal mortalities in fisheries.

More research is currently underway, too, to understand how the bottles might work in different environments and with different fishing styles and gear. Further testing is currently happening in Cambodia and Congo fisheries.

You might also like…

• read the paper: Berggren, P., Alfaro-Shigueto, J., Mangel, J., Sharpe, M., Jiddawi, N., Neasham, J., Larre, G., Temple, A. J. (2026). ‘Upcycled glass and plastic bottles offer potential low-cost mitigation to megafauna bycatch in gillnet fisheries.’ Fisheries Research. https://doi.org/10.1016/j.fishres.2026.107748
• read the paper: Sucunza, F., Barth, A., Danilewicz, D., Dolman, S., von Fersen, L., Larre, G. G., Mangel, J. C., Ott, P. H., Alfaro-Shigueto, J., Temple, A. J., Tregenza, N., & Berggren, P. (2026). ‘Evidence of dolphin bycatch reduction with upcycled plastic bottles acoustic reflectors attached to bottom-set gillnets.’ Marine Mammal Science. https://doi.org/10.1111/mms.70189
• visit the press release: ‘Discarded plastic bottles help save dolphins from fishing nets’
• discover the work of Professor Per Berggren, Emeritus Professor of Marine Megafauna Conservation, School of Natural & Environmental Sciences
• explore what we do at our School of Natural and Environmental Sciences
• Marine Science Research | School of Natural and Environmental Sciences | Newcastle University

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