Title: Charting a Low-Carbon Future for Sustainable Aquatic Food Value Chains 1 Introduction This note is a synthesis of a comprehensive discussion paper: Charting Low-Emission Pathways Across Aquatic-Food Value Chains. The discussion paper, based on eight case studies, contributes to answering the question: given that the fisheries and aquaculture sector greenhouse gas (GHG) emissions are relatively low compared to other animal production systems – why invest in decarbonizing the sector? This synthesis summarizes the main areas of action for decarbonizing aquaculture and fisheries primary-production systems and post-harvest processing, including cold-chain aspects and waste management, and points to short and long- term actions along with key areas requiring further research. Accurate, consistent and widespread assessments of GHG emissions in the sector are lacking due to studies taking different approaches and methodologies as well as the lack of global coverage (Box 1). However, current estimates of GHG emissions from the fisheries sector arrive at 1-2% and from aquaculture 0.5% of global emissions1, but as other ocean-based sectors, such as shipping or transport, have committed to reducing their emissions, a business as usual (BAU) approach will see this % increase relative to other sectors. Decarbonization of the sector has the potential to increase profits of many fish production systems, making the transition an opportunity to improve the sector’s environment and social outcomes while maintaining or enhancing its profitability. Box /infographic: Estimated CO2/kg of whole fish produced2,3,4,5; salmon4-8 kg CO2/kg produced; Tuna 3-7 kg CO2/kg produced; Tilapia 2-4 kg CO2/kg produced; anchoveta 1-2 kg CO2/kg produced; mussels 0.3-0.5 kg CO2/kg produced) In terms of global commitments – in addition to contributing to meeting climate change mitigation goals globally and nationally, decarbonizing help countries to comply with the Montreal Protocol, meet SDGs (including 2, 7, 12 and 14) and reduce biodiversity loss as well as maintaining the ocean’s biological pumpa a critical component for regulating global climate. Fisheries and aquaculture are a highly diverse sector with production focused on a range of species, using different gears, technologies and practices, with some production systems already reducing their emissions (e.g., anchoveta fisheries) while others face significant challenges (including the farming of carnivorous species). Much of the shift to lower GHG emission fish production systems is taking place in developed countries where policies, access to technologies and the financial resources support the transition. Nevertheless, case studies reveal significant potential for reduction stemming from diverse emission sources: with feed a The ocean's biological pump is a natural process where marine organisms transport carbon from the surface to the deep ocean. This occurs primarily through photosynthesis by phytoplankton, which absorb carbon dioxide at the surface. When these organisms die or excrete waste, the organic carbon sinks to deeper waters, helping regulate atmospheric CO₂ levels and contributing to long-term carbon storage. 1 production, transport, post-harvest processing, and losses and waste management as key contributors. Tailored solutions are needed to address these GHG emission hotspots while balancing environmental sustainability with socio-economic equity, particularly for vulnerable groups like women and small-scale farmers. A holistic approach involving technological advancements, improved management practices, financial support and policy reforms is essential for a successful transition to decarbonized fish value chains. Specific actions include improving feed efficiency, optimizing transport, adopting energy-efficient practices, reforming subsidies and minimizing waste. Future efforts should include cost-benefit analyses of decarbonization options, policy reforms, financing strategies, and case studies in developing countries' aquatic food systems – much of which will need to be supported by more and better data. Box/Map for the case studies: Four capture fisheries (Indian Ocean tuna, Peruvian anchoveta, African Great Lakes and West Africa marine) and four aquaculture production systems (Norwegian salmon, Egyptian tilapia, Mediterranean mussels, and Vietnam shrimp) were reviewed to identify GHG emission hotspots. The four fisheries and four aquaculture geographically focused case studies represent, by volume, at least 15% of all fisheries and 20% of aquaculture production globally6. Their GHG reduction pathways, which consider environmental, social, political and financial aspects, offer general principles and approaches to guide policymakers in making necessary changes, while detailed case-by-case analyses give specific transition guidance for each production system. 2. A Sustainable Catch: Charting a Low-Carbon Future in Fisheries and Aquaculture 2.1 Decarbonization Across Aquaculture Systems A multi-faceted approach that includes adoption of technologies, innovative financing, exploring low-trophic marine organisms as farmed species or feed alternatives, and optimizing feed management across production systems is needed to decarbonize aquaculture systems. By decoupling nutrition efficiency from environmental impact, sustainable aquaculture that supports decarbonization while reducing costs and boosting productivity is possible. Aquaculture (feed and non-feed based) plays a pivotal role in food security and offers potential to address protein and nutrient demands sustainably, but its greenhouse gas footprint requires attention. Many production systems use traditional practices that tend to emit significant amounts of GHG, primarily due to feed production and consumption, energy use, and post- harvest spoilage. This section highlights the limitations of traditional practices and the need for transformative solutions. The technology for renewable energy sources such as solar, biofuels and micro-hydroelectric systems to power fish farming equipment, cold chains and processing facilities is well developed. However, while incorporating renewable energy sources is pivotal for decarbonizing aquaculture and achieving sustainable food production, energy use during the grow-out phase in fish farming is generally less significant compared to that of feed production where the raw materials and energy consumption are key emission sources7. 2 Transitioning from fishmeal and fish oil towards sustainable plant-based feeds, even those non- plant-based feeds with lower GHG footprints, appears to provide significant reductions in GHG emissions, but raises other concerns. Greater reliance on plant-based feeds—characterized by higher feed conversion ratios—may increase demand for raw materials like maize and soy, whose production has historically driven land-use conflicts and intensified water scarcity8. Fishmeal, on the other hand, has high nutritional value but raises ecological, biodiversity and fuel use concerns9. Potential substitute feed ingredients include insects, algae, and microbial proteins which offer lower emissions but face scalability challenges10, 11. Fungi-derived single-cell protein shows promise as a sustainable substitute for soy protein, reducing emissions and supporting efficient fish growth12. Cost poses a significant barrier to decarbonizing aquaculture feed, particularly for small-scale feed producers and farmers. Alternative feed ingredients tend to be more expensive than traditional fishmeal10. This cost premium limits adoption, especially in developing countries. Balancing cost efficiency with emission reduction remains a key challenge in sustainable aquaculture practices, including for decarbonization, and transitioning to feed-production technologies with a low carbon footprint requires innovative financing solutions. Non-fed aquaculture offers considerable potential for decarbonizing seafood production while enhancing ecosystem services. Seaweed and bivalve farms cause significantly lower greenhouse gas emissions than finfish farms due to their natural nutrient absorption and water quality enhancement capabilities, thus offering ecosystem benefits alongside decarbonization13. However, the farms require careful management to mitigate potential habitat degradation from farm activities, including from large-scale seaweed production14. Innovative integrated systems like Integrated Muli-Trophic Aquaculture (IMTA), agrivoltaics (combined fish farming and energy production), and aquaponics offer pathways to aquaculture decarbonization. IMTA, for example, leverages resource efficiency by cultivating diverse species that complement each other and recycle nutrients15. Recirculating Aquaculture Systems (RAS) coupled with renewable energy can address other environmental problems such as waste treatment. While these diverse systems have been successfully implemented in developed nations, their application, primarily IMTA, is only emerging in developing countries and requires support. Some integrated systems may increase investment costs, production times, operational complexity (especially for scaling), certification costs and competition for land use. Nevertheless, promoting the adoption of renewable energy sources in IMTA systems further supports decarbonizing aquaculture and achieving sustainability. Improved aquaculture practices such as automated feeding systems, selective breeding and precision feeding practices can effectively reduce uneaten feed and optimize nutrient utilization, minimizing energy waste. Reducing fish mortality and waste from processing can also reduce 3 GHG emissions. Furthermore, selective breeding can foster fish varieties with improved growth rates and feed conversion ratios, leading to lower emissions15. Marine aquaculture emerges as a relatively more sustainable alternative, with studies indicating approximately 40% lower GHG emissions per unit of product compared to freshwater systems16. Whether marine or freshwater, promoting systemic change will be required. Transitioning to low GHG emission aquaculture can facilitate economic and social empowerment for women, youth and other marginalized small-scale producers while enhancing environmental sustainability. Policy interventions, access to finance and training can empower these producers, by addressing the increased capital costs required to adopt advanced technologies, which in turn can help reduce operating and certification costs 17. Additionally, targeted support for training programs—such as those focused on feed management—and improved access to high-quality feed and equipment are essential for fostering inclusive and sustainable growth in the sector. 2.2 Decarbonization of Fisheries Managing fisheries for sustainability supports decarbonization of the sector. Governance and management reforms are essential for preserving fish stocks, protecting the ocean's carbon sequestration capacity, and ensuring an inclusive transition to low-carbon systems, with social equity as a required outcome. Management measures include curbing overfishing, incentivizing the phasing out of destructive fishing methods and the uptake of best practices and low- emission technologies. Fisheries are often overlooked by policy makers in global decarbonization efforts even though decarbonization can also help to address the environmental impact of industrial fishing. While providing vital food sources, fishing contributes significantly to GHG emissions through fuel consumption – not least in the case of high-impact gear like bottom trawls18. Tackling these issues requires a multifaceted approach encompassing both technological innovation and robust fisheries management. Transitioning to low-carbon technologies, practices and infrastructure includes using energy- efficient vessels and renewable energy sources and optimizing transport and processing systems to minimize emissions. Significant emission reductions, expressed often as lower fuel-use intensity, can be achieved through a two-pronged approach: adopting low-impact fishing gear and technologies, such as fuel-efficient vessels and selective fishing techniques, alongside robust control of fishing effort and reformed subsidy policies19. This means that technological advancements must be complemented by effective policy measures to ensure responsible deployment of technologies and prevent unintended consequences. Controlling fishing effort includes implementing catch quotas, spatial and seasonal closures, and regulations on the use of fishing gear, in order to protect vulnerable ecosystems, and promote sustainable fish populations. Fishing practices like bottom trawling, prevalent in many regions, can contribute significantly to GHG emissions and marine ecosystem damage due to high fuel consumption, and potentially 4 destructive gear and its use20. Lack of robust oversight exacerbates these issues, particularly in areas lacking effective regional fisheries management arrangements. Furthermore, addressing operational inefficiencies in small-scale fisheries through, for example, speed reduction along with responsible practices can contribute to emission reduction. Infographic: Fuel Consumption in Various Fishing Practices primarily from Danish fisheries (Bastardie et al. 2022) Low Fuel Use Intensity Practices: Dredging for Mollusks: 0.0072-0.0122 L/kg.; returns between 25-40 EUR/L Pelagic Seining for Mackerel and Herring: Demonstrated a FUI of 0.071 L/kg; 25.87 EUR/L, Tuna fishing using purse seine gear (based on study of 93 purse seine vessels 368 L/mt; n/a (Parker et al., 2015). High Fuel Use Intensity Practices: Bottom Trawling for Crustaceans: 1.1309-2.1515 L/kg; 3.24-4.87 EUR/L) Mixed Demersal Fisheries: 0.15-1.26 l/kg Box: West African fisheries face significant hurdles in decarbonization due to extensive bottom trawling in the face of weak regulations and high energy consumption. This results in the loss of ecosystems and their services. While innovations like "lift nets" using lamps offer fuel efficiency, especially when solar powered, careful management is crucial to prevent overfishing including robust regulatory frameworks21. The use of Fish Aggregating Devices (FADs) presents a complex dilemma for decarbonization efforts. While they offer potential benefits by improving fishing efficiency and reducing fuel consumption, research suggests that FAD-dependent purse seiners often exhibit higher fuel use intensity due to larger vessel size and accompanying supply vessels18, 22. FADs also come with significant trade-offs, including increased bycatch of vulnerable species, the risk of becoming marine debris, and potential disruption of natural fish behaviors. While biodegradable FADs and improved management practices are being explored, realizing FADs' sustainability potential as a tool for decarbonizing fisheries remains challenging23. Comprehensive assessments of fishing fleets are crucial for understanding their environmental impact and implementing effective mitigation measures. Ultimately, achieving decarbonization requires a holistic approach encompassing technological innovation and robust regulations or other management arrangements for sustainable fishing practices, combined with an enabling environment that promotes and facilitates compliance. Social equity must be woven into decarbonization strategies. Women, who contribute significantly to post-harvest processing in fisheries, require targeted training, access to energy- efficient equipment, and equitable opportunities to participate in decision-making processes24. Supporting small-scale fishers and fish workers through cooperative models, access to financing, and capacity building can help them transition to sustainable practices while maintaining their livelihoods. Social protection and broader labor-market interventions, especially for vulnerable 5 groups, can further facilitate this transition, fostering economic empowerment alongside environmental benefits. In summary, by integrating technological innovation with strong and inclusive governance and management frameworks, it becomes possible to establish a pathway towards decarbonized fisheries that balance economic and social needs with environmental sustainability. This approach will mitigate the sector's contribution to climate change, safeguard marine biodiversity, and support the long-term health of the ocean along with the livelihoods that depend on fisheries. 2.3 Low-Emission Cold Chain Technologies Cold chains play a crucial role in the fisheries and aquaculture sector, to reduce waste and improve quality, but inefficient equipment, outdated technologies and reliance on fossil fuels contribute significantly to GHG emissions. Actionable decarbonizing solutions such as implementing energy-efficient technologies like LED lighting, enhanced insulation, low-GWP refrigerants such as NH3 and CO2 in transport systems, renewable-powered refrigeration, and optimized transport routes, can drastically reduce emissions25. Furthermore, minimizing post- harvest losses through improved handling practices reduces the need for energy-intensive refrigeration. Widespread adoption of energy-efficient technologies often requires high upfront costs, raise safety concerns and requires technical expertise. Infographic or Box: Upgrading equipment and insulation can reduce energy consumption by 15- 20%, leading to cost savings and lowered emissions. Integrating solar or wind power into cold chain operations can reduce grid electricity dependence by up to 60%, mitigating emissions by 246,000 kg CO₂ annually (World Bank internal report). Box: Solar-powered storage systems deployed in areas of Africa’s Great Lakes region, are proving to be a reliable refrigeration option, with minimal emissions impact. By incorporating thermal energy storage, such as phase change materials (PCMs), the systems ensure uninterrupted cooling even in remote areas with intermittent sunlight26 Ice remains a predominant method for cooling fish, especially in small-scale operations, leading to significant energy consumption and carbon emissions. Current practices often involve inefficient ice storage and transport, resulting in substantial ice loss and greater environmental impacts. Sustainable alternatives to traditional ice-based cold chains such as Phase Change Materials (PCMs) and insulation materials offer a promising solution for maintaining consistent temperatures during transport and short-term storage, reducing reliance on mechanical refrigeration and lowering operational costs and emissions. Additionally, vacuum-sealed packaging extends shelf life, minimizing cooling needs. Policies that offer financial incentives, supporting energy-efficient technologies and encourage infrastructure development, can accelerate industry adoption and decarbonization. Investing in research and development for more accessible sustainable refrigerants, training and fostering collaboration will unlock further innovations. 6 2.4 Technology-driven Decarbonization in Fisheries and Aquaculture Most current fisheries and aquaculture practices heavily rely on fossil fuels, contributing to greenhouse gas emissions. Renewable energy sources like solar, geothermal, and micro- hydroelectric systems are potential technologies for powering fishing vessels, aquaculture activities, and cold-chain systems. Additionally, automation and robotics can significantly enhance energy efficiency through precision feeding, monitoring, and harvesting processes. Advanced technologies such as blockchain and artificial intelligence (AI) promote transparency, accountability, and resource management with the potential for further energy reduction throughout the value chain. 2.5 Sustainable Choices While specific technological innovations are crucial to decarbonizing the sector, lasting and significant impact hinges on adopting sustainable practices across entire value chains. Primary producers as well as processors and transport and distribution actors play a key role in decarbonization by implementing sustainable practices and using efficient feed production methods and energy-saving technologies. Importantly, consumers can contribute by becoming more aware of and making conscious seafood choices that support sustainable practices. A theory of change which identifies drivers of change provides a strategic framework to target desired behavioral changes along with accompanying risks and assumptions for that to happen. Strategies for behavioral change need to be inclusive of marginalized groups. Empowering stakeholders at every level to adopt new behaviors contributes to effective decarbonization of the sector27. 2.6 Fish Waste Management for Decarbonization Fish loss and waste (FLW) throughout the fishing and aquaculture value chains is a major contributor to greenhouse gas emissions mainly due to methane released from decomposing waste in anaerobic condition – in addition to this waste leading to the need to produce additional volumes. Therefore, minimizing waste at every stage of the value chain is key to reducing GHG emissions. Selective fishing gear to reduce unwanted bycatch, effective health management in aquaculture, and improved cold chain logistics with energy-efficient practices, and alternatives to refrigeration contribute to decarbonizing value chains and increasing economic returns. Decarbonization is further enhanced by developing innovative ways to repurpose fish byproducts and diversifying waste management routes such as biogas capture, anaerobic digestion, composting and black soldier fly recyclingb. These approaches are resource efficient and help conserve resources by recovering energy, capturing methane, and producing nutrient-rich digestate thus reducing methane emissions. These approaches also help to conserve resources, but they may involve trade-offs, which need to be managed. Current waste management practices in this sector contribute significantly to greenhouse gas emissions. Developed nations often prioritize consumer preferences for fillets, discarding b Black soldier fly (BSF) recycling uses black soldier fly larvae (Hermetia illucens) to recycle organic waste into nutrient-rich fish feed. 7 valuable parts of fish often in line with government waste regulations, thus increasing waste in the first place. Disposal of fish waste in developing nations on the other hand may not be as advanced and may rely on less efficient methods like open dumps. There are opportunities to generate value for fish waste. Innovative approaches employed in some regions include fish waste for animal feed, oils, and leather products. Promoting alternative uses for fish waste and investing in recycling facilities can significantly reduce emissions. This not only benefits the environment but also supports local economies and enhances food and nutrition security. Measures that transition away from traditional methane emitting waste management practices and reduce fish loss and waste need to be region/country specific and consider technology availability and socioeconomic factors. Box: Examples of By-Product Use28,29 • Farmers use fishmeal as a high-protein ingredient in animal feed (e.g., poultry and aquafeed), while fish oil is rich in omega-3 fatty acids and used in supplements and pharmaceuticals. • Carotenoids from shrimp waste are extracted for use in aquaculture feeds to enhance the coloration of farmed seafood. • Collagen and gelatin derived from fish skin, scales, and bones are widely used in the food, cosmetic, and biomedical industries. They are known for their applications in anti- aging cosmetics, wound healing, and as gelling agents in food products. • Chitin extracted from crustacean shells are used in cosmetics, medical applications (wound healing, tissue engineering), and water purification due to their antibacterial and biodegradable properties. 3 Investing in a Sustainable Future 3.1 Closing Knowledge Gaps Realizing existing and potential solutions for decarbonizing fisheries and aquaculture necessitates addressing key knowledge gaps that hinder the transition. The main such knowledge gap is the economic justification and pathway for transitioning to decarbonized fisheries and aquaculture value chains. Filling this gap requires gathering fundamental and consistent information and using robust methodologies, to help quantify the costs and benefits of various options – including the option of doing nothing: • Quantifying emission reductions - collecting and generating robust data across regions to accurately measure the impact of decarbonization measures: one critical gap lies in accurately quantifying GHG emissions across various fish value chains, from production to consumption. This includes transportation, processing, and refrigeration, which can significantly influence the overall GHG emissions. This gap also includes robust methodologies for measuring emissions from aquatic food waste, a significant emission source often overlooked. Further understanding the carbon impacts of bottom trawling – a practice that can disrupt marine ecosystems and is fuel intense – is also needed. Life Cycle Analyses provide a comprehensive understanding of energy consumption, GHG emissions, resource use, and pollution across the entire life cycle of value chains and so 8 can help fill some of the existing knowledge gaps. Additionally, LCAs can help assess socio-economic impacts (e.g., job creation and public-health risks). • Going beyond fuel use reduction: this requires more than simply reducing emission output; it necessitates a shift towards holistic approaches. This involves exploring innovative mitigation measures that go beyond fuel use reduction, policies that manage tradeoffs and protect vital ecosystems and services such as the ocean’s biological pump, and responsible waste management strategies throughout fish value chains. In addition, socio-economic impacts, including the effects on marginalized groups and the need for gender-responsive training and incentives for low-carbon technologies, are recognized as critical areas requiring further exploration. • Understanding aquaculture - a double-edged sword: Aquaculture presents a unique challenge, offering potential for carbon sequestration but also contributing to GHG emissions through feed production, feed waste management, and energy use. Comprehensive data collection and LCAs is needed to accurately quantify the carbon footprint of different species and farming systems. This includes understanding biogenic GHG emissions from various aquaculture practices and clarifying the true potential of biogenic carbon fixation in these systems. Bridging these data gaps requires collaboration between scientists, policymakers, industry stakeholders, and consumers and developing data-driven solutions for decarbonizing the sector. 3.2 Balancing tradeoffs A thorough understanding of the cost-benefit outcomes for various decarbonization strategies across diverse contexts is crucial for effectively making the case for profitability by decarbonizing and subsequent investment allocation. This will need to include social costs and benefits to ensure a just decarbonization transition, thoroughly assessing potential job losses and economic disruption in dependent communities, especially for marginalized groups including women and youth. Box A study at the European Union level mapped low-carbon energy innovations and efficiency solutions in fisheries and aquaculture value chains, analyzed current energy use and CO2e, and estimated costs to reduce them, assessing each solution’s financial viability. The study highlights the need for context-specific data to identify and implement tailored solutions.30 Additional sustainability aspects could be incorporated into such an analysis, for example evaluating edible product yield per ton of CO2e against nutrient density, thus identifying species and production methods offering the highest nutrient benefit for the lowest emissions. Such insights on nutrition and climate impact could help refocus production and consumption towards improved sustainability and efficient practices31. 9 The formulation of a multidimensional framework to assess trade-offs in decarbonizing aquatic food value chains, addressing both environmental, economic and social impacts, would accelerate transitioning. The framework could feature: • Holistic Assessment that considers environmental impact (GHG emissions, resource use), economic viability (costs, profitability), and social equity (gender relations, livelihoods). Tools such as Cost Benefit Analysis and Marginal Abatement Cost curves (identifying the most cost-effective strategies) could be applied in these assessments. • Data-Driven Insights that integrate quantitative data on production, emissions, costs and earnings, and social impact assessments to provide a comprehensive understanding of value chain dynamics. Life Cycle Analysis can support comprehensive insights into emissions along value chains and identify hotspots for improvement. • Multi-Criteria Decision Analysis (MCDA) to systematically navigate trade-offs between environmental, economic and social dimensions, ensuring balanced and context- sensitive decisions while assessing associated risks32. MCDA can include assessment that quantify how shifts in social equity impact the overall success of decarbonization efforts, helping to identify trade-offs and support decisions that foster inclusive, equitable growth. • Policy Integration & Stakeholder Engagement to align decarbonization actions with international climate policies and targets (e.g., SDGs) and actively engage producers, regulators, NGOs, consumers, and other stakeholders. A framework with these features can empower decision-makers to implement practical and sustainable decarbonization strategies for fisheries and aquaculture. 3.3 Shorter- and longer-term investments Investments in decarbonization across fish value chains require actions that prioritize both immediate impact and long-term sustainability. Shorter-Term Actions: There are practical, lower-cost strategies to help immediately decarbonize fisheries and aquaculture across value chains, from improved storage and processing to adopting renewable energy solutions, as outlined above, focusing on quick wins that demonstrate the economic and social benefits of sustainable practices. These include: • Scaling up successful interventions: to better understand how strategies from effective GHG-reducing projects can be replicated and expanded to other regions facing similar challenges. • Exploring emerging technologies: to further enhance decarbonization efforts in fisheries and aquaculture that could be applied in different contexts. • Developing skills: to enhance the uptake of low-carbon technologies and best practices, investing in training programs for actors along fisheries and aquaculture value chains. 10 • Providing targeted public funding: to promote initiatives exploring, for example, energy efficiency in processing facilities, electric vessels, low GHG fish feeds and alternative fuel sources for transportation targeting small to medium-scale enterprises. • Raising public awareness: to educate consumers, using campaigns about climate and related environmental impacts of seafood choices to promote sustainable consumption through certification and traceability programs. Longer-Term Actions: Building on short-term successes requires a comprehensive approach: • Policy Integration: Embedding fisheries and aquaculture decarbonization goals into national policies, regulations, and international trade agreements. • Technological Advancement: Funding research and development of next-generation low- carbon technologies specifically tailored to the needs of fisheries and aquaculture stakeholders. • Financial Incentives: Exploring and implementing innovative financing incentives, such as carbon pricing mechanisms and providing subsidies for sustainable practices to encourage adoption. Taking up short and longer-term actions and addressing these unknowns through collaborative efforts between governments, the private sector, civil society, and research institutions will be vital for achieving a sustainable and low-emission fisheries and aquaculture sector. 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