University of Oxford
11a Mansfield Rd
OX1 3SZ
UK
25th April 2025
5 minutes read
A new study 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 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.
A fisher in KUL’s programme carefully releases a Critically Endangered wedgefish.
Image: Francesca Page
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.
The project ‘Kebersamaan Untuk Lautan ’(KUL), translating to ‘Togetherness for the Ocean’, is an initiative re-shaping shark conservation, bridging conservation and community welfare.
Image: 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.
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 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.”
The results demonstrate that even the most careful efforts to design a conservation programme may not account for all types of real-world uncertainties and complexities – and underline the importance of piloting with experimental designs before scaling.
Millions of Critically Endangered sharks – like the wedgefish shown here – are killed each year by becoming entangled in unselective fishing nets.
Image: Francesca Page
Senior researcher Professor Paul Ferraro (Johns Hopkins University) said: “Pay-to-release schemes for endangered species caught by local fishers are being implemented around the world. Yet these schemes tend to be implemented without anyone asking whether they actually make a difference to the catch of endangered species. It is concerning that so much money continues to be spent on conservation programs without rigorous evaluations of their impacts on biodiversity and socio-economic outcomes.”
Teuku Ridwan, Head of the Department of Marine Affairs and Fisheries of Aceh Jaya Regency said: “This initiative has had a tangible impact on strengthening the livelihoods of small-scale fishers, who form the backbone of coastal life in Aceh Jaya. We hope that the synergy between implementing organisations, fishing communities, traditional leaders, and local government continues to be strengthened to realise marine management that is just, sustainable, and rooted in local wisdom.”
The researchers highlight that taking this approach will ensure that conservation interventions can better contribute to bending the curve on biodiversity loss and delivering the Global Biodiversity Framework’s 2050 vision of ‘living in harmony with nature’.
To read more about this research, published in Science Advances, visit: https://www.science.org/doi/10.1126/sciadv.adr1000
Author
I completed my DPhil in the Biology Department in 2021 on Interdisciplinary Approaches to Shark and Ray Conservation, with a focus on small-scale fisheries in Indonesia. Since then I have been working with local researchers, NGOs and decision-makers in Indonesia to put my findings into practice, by designing and testing incentive-based approaches for marine biodiversity and human wellbeing outcomes with support from the Oxford Policy Engagement Network (OPEN) and the UK Darwin Initiative. This includes running the world's first Randomized Controlled Trial (RCT) of an incentive-based marine conservation program for Critically Endangered sharks and rays. In parallel, I have been working on mechanisms for improved accountability for nature-related impacts and dependencies in the private sector, through approaches to operationalise ambitious and evidence-based Nature Positive commitments which mitigate the negative environmental impacts of corporate value chains and channel funding towards measurable, additional and socially-just biodiversity outcomes. I am generally interested in conducting applied interdisciplinary research to make conservation more effective and socially just.
Aside from my research work at Oxford, I have also worked in the non-profit and private sector, with roles spanning community-based tourism and protected area management in East Africa; shark and ray fisheries and trade in SE Asia; and global environmental policy and corporate biodiversity strategies.
I grew up in Birmingham, and was the first person from my family to go to university after attending a poorly-performing state school. As such, I am passionate about promoting participation of women, minority groups, and people from low-income backgrounds in academia and conservation.
Author
E.J. Milner-Gulland is Tasso Leventis Professor of Biodiversity at the University of Oxford. Previously she was Professor of Conservation Science at Imperial College London, and she has also held lectureships in Resource Economics and Mathematical Ecology. Her PhD, at Imperial College London, was on the wildlife trade, with a focus on ivory, rhino horn and saiga antelopes. Her research group, the Interdisciplinary Centre for Conservation Science, undertakes a wide range of research, outreach and engagement projects, on five continents and in both marine and terrestrial settings. These include developing and applying methods for understanding, predicting, and influencing human behaviour in the context of local resource use in developing countries, and working with businesses to improve their environmental and social sustainability. Her team also works on controlling the illegal trade in wildlife and on designing, monitoring and evaluating conservation interventions in order to improve their effectiveness. She aims to ensure that all the research in her group is addressing issues identified by practitioners, and is carried out collaboratively with end-users, and builds the capacity of young conservationists, particularly in developing countries. She is the founder and chair of the Saiga Conservation Alliance and has launched a number of initiatives which aim to change the real-world conversation around conservation, including the Conservation Hierarchy approach to meeting a global vision of restoring nature and the Conservation Optimism movement. She is the Chair of the UK Government's Darwin Expert Committee and a Trustee of WWF-UK
Finally, I am passionate about the conservation ecology of the saiga antelope in Central Asia, and co-founded the Saiga Conservation Alliance in 2006.