Two recently published studies have shown that using plastic bottles as reflectors on the gillnets led to dolphin bycatch reduction of 88%, while the fish catch remained the same. Reflectors are devices attached to fishing nets to make them acoustically visible to echolocating marine mammals like dolphins and porpoises.

The team tested an idea, developed by Professor Per Berggren at Newcastle University, UK, of 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.

Published in the journals Fisheries Research and Marine Mammal Science, the studies showed that attaching empty drink bottles to the nets reduced the accidental capture of dolphins in fishing nets, the leading threat to marine mammals worldwide.

Gillnets are made from nylon and are almost invisible (acoustically and visually) to the animals in the water. Discarded plastic bottles with air inside attached to fishing nets act as sound reflectors while glass bottles with metal bolts inside attached to the nets produce a clinking sound, both helping dolphins detect and avoid the nets while allowing fishers to continue catching their target species.

The lead and senior author of the studies, Per Berggren, Emeritus Professor of Marine Megafauna Conservation, School of Natural & Environmental Sciences, Newcastle University, said: “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.  Attaching plastic bottles to fishing nets can reduce dolphin bycatch globally and is something that every fisher can afford.

“It’s also rewarding to know that we are using some of the plastic waste that spoils our oceans. The bottles are securely attached to the nets and we did not lose any plastic bottle during the trials.

“We are excited to share this method and spread the word and work with governments and agencies around the world to encourage the adoption of this low-cost mitigation method to reduce marine mammal mortalities in fisheries.

“This is genuinely recycling that rescues dolphins.”

Bottles tested in driftnet and bottom-set fishing

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 studied in Peru and Zanzibar. In contrast, in Brazil plastic bottles showed promise in the bottom-set gillnet fishery, potentially reducing dolphin bycatch while increasing fish catch, though further trials were needed to confirm this.

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

Professor Bergen added: “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.”

Further research testing the use of plastic bottles is now underway in Cambodia and Congo fisheries.

Reference

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

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

Top image caption:

Up-cycled glass bottle pingers and plastic bottle acoustic reflector trials. a) Workshops were held with fishermen in the targeted fisheries to introduce the project and secure participants. b) glass bottle pinger attached to a surface-set driftnet. c) Plastic bottle acoustic reflector attached to a surface-set driftnet. d) dolphin bycatch in a surface-set driftnet during the trial.