Against the backdrop of continuous global population growth and changes in dietary structures, aquaculture has emerged as one of the fastest-growing food production sectors. However, as its scale expands, concerns about its environmental impacts, particularly greenhouse gas (GHG) emissions, have grown. Have you ever wondered how much GHG is emitted during the production of the fish, shrimp, and shellfish on your plate? Where do these emissions come from, and how can they be reduced?
Professor Hong Yang from the Department of Geography and Environmental Science at the University of Reading systematically reviewed global research on GHG emissions from aquaculture through a review article. Based on 1821 relevant publications from the Web of Science database, the study analyzed emission sources, species differences, regional characteristics, and mitigation strategies, providing a scientific basis for the low-carbon transformation of the industry. The article has been published in Frontiers of Agricultural Science and Engineering (DOI: 10.15302/J-FASE-2025665).
The research found that GHG emissions from aquaculture mainly originate from four stages: feed production, energy consumption during farming, biogeochemical processes in ponds or waterbodies (such as methane and nitrous oxide release), and land-use change and infrastructure construction. Among these, feed production is the largest source of emissions in most fed aquaculture systems, accounting for 52% in Chinese studies. In regions dominated by freshwater pond aquaculture, such as China, methane emissions are particularly prominent, contributing approximately 90% of total GHG emissions from aquaculture systems.
There are significant emission differences between different aquaculture species. For example, unfed bivalve (e.g., oysters, clams) and seaweed farming have extremely low or even negative emissions, and can instead act as carbon sinks through carbon sequestration. Herbivorous or omnivorous fish (e.g., carp, tilapia) also have relatively low emissions under moderate farming intensity. In contrast, intensively farmed carnivorous fish (e.g., salmon, trout) and shrimp have significantly higher carbon emission intensity due to high feed and energy demands, with some even comparable to terrestrial livestock.
From a geographical perspective, China is the world's largest emitter of GHGs from aquaculture, accounting for more than half of the global total. Followed by other Asian countries such as India, Indonesia, and Vietnam. These regions generally adopt pond farming models, with prominent methane emission issues. While developed countries like Norway and Canada have relatively low total emissions, their carbon emission intensity per unit product is high due to energy-intensive farming methods (such as recirculating aquaculture systems) and long-distance transportation.
Faced with these challenges, scientists have proposed various mitigation pathways. For instance, optimizing feed formulations and improving feed utilization efficiency can reduce carbon emissions at the source. Promoting renewable energy and enhancing equipment energy efficiency help reduce direct emissions during farming. In addition, improving water and waste management, developing integrated multi-trophic aquaculture, and restoring blue carbon ecosystems such as mangroves have also been proven effective in reducing methane and nitrous oxide emissions.
The author emphasizes that aquaculture is not necessarily a high-carbon industry; its climate impact depends on farming practices, species selection, and technological levels. In the future, through policy guidance, technological innovation, and industry collaboration, aquaculture is expected to achieve low-carbon transformation while ensuring food security, contributing to global climate goals.