A new study from the University of Oxford has revealed that an incentive programme increased live releases of endangered species caught as bycatch. However, unexpectedly, the overall positive impact was reduced by some vessels increasing catches of these species. The study, published in the journal Science Advances , is the world's first randomised controlled trial to conclusively assess the effectiveness of an incentive-based marine conservation programme.
Large, long-lived marine animals such as sharks and rays are amongst the world's most threatened groups, primarily due to overfishing in targeted and bycatch fisheries. In small fisheries, households rely on marine resources for their food and income, creating trade-offs between biodiversity and wellbeing outcomes. Incentives therefore can provide a cost-effective and equitable option for balancing the needs of people and biodiversity. However, incentives can also change behaviour in unexpected ways, which means their impacts need to be rigorously tested before scaling up.
Oxford researchers worked with local NGO Kebersamaan Untuk Lautan (KUL) to evaluate a pay-to-release programme that compensated fishers for safely releasing two Critically Endangered groups of species: hammerhead sharks (Sphyrna) and wedgefish (Rhynchobatus), in small-scale fisheries in Indonesia. Hammerhead sharks and wedgefish are threatened by overfishing and are often caught as bycatch during fishing for other species.
Right: A fisher tags wedgefish ready for release. Aceh, Indonesia. © Liam Webb. Left: A fisher shows a video of him safely releasing a Critically Endangered wedgefish, on the waterproof camera provided by KUL. © Francesca Page.
The study evaluated the first 16 months of the programme (May 2022 - Aug 2023), which involved 87 vessels randomly split into two groups; one group were eligible to receive compensatory payments for live releases while the other acted as a 'control' and were not offered payments. Fishers proved they had safely released hammerheads and wedgefish by taking videos on provided cameras, which needed to show the released fish safely swimming away and out of sight. The compensatory payments were in line with what the fishers could have made by selling the sharks and rays in local markets, based on previous work also conducted by the same Oxford team.
The programme proved highly successful in motivating fishers to release the Critically Endangered species: 71% of wedgefish that were caught were released, whilst 4% of caught hammerheads were released. However, the experimental evaluation revealed that the programme also encouraged some vessels to increase their catches to receive more payments at the expense of conservation goals. When this was taken into account, wedgefish mortality was only 25% lower in the treatment condition relative to the control, while hammerhead mortality was 44% higher.
A short film about the NGO Kebersamaan Untuk Lautan ('Togetherness for the Ocean'), featuring Dr Hollie Booth and describing the incentives programme.
The results provided critical insights for adapting KUL's incentive programmes; since the study, KUL have 1) adjusted the amount of compensation offered to fishers, so that it is based on size classes, 2) capped the number of allowable compensated releases per vessel per week, and 3) piloted a new gear swap scheme, to avoid catches of threatened species in the first place. Although no formal analysis has been completed for the second phase, preliminary results look promising. KUL have also continued running the programmes as randomised controlled trials, together with Oxford researchers, with financial support from the UK's Darwin Initiative.
Lead researcher Dr Hollie Booth (Department of Biology, University of Oxford) said: 'Incentive-based programmes play a critical role in effective and socially just nature conservation. We can't expect small-scale resource users to bear the majority of the costs of conservation, especially when there are wealthier and more powerful stakeholders causing major negative impacts. However, as our study has shown, incentives must be well designed and robustly evaluated to incentivise the right behaviour and ultimately deliver positive outcomes for nature and people.'
