Heading towards an improved marine aquaculture sector

It’s one of the world’s fastest growing food industries and, with the introduction of some new strategies investigated by researchers at the University of Adelaide and The Nature Conservancy, could soon be one of its greenest.

In a new paper published in BioScience, Climate-Friendly Seafood: The Potential for Emissions Reduction and Carbon Capture in Marine Aquaculture, six principles are identified for industry and government to develop and maintain zero or even net-negative-emissions processes on a larger scale.

Aquaculture is a critical food source for the world’s growing population, producing 52 per cent of the aquatic animal products consumed, and marine aquaculture (mariculture) generates 37.5 per cent of this production and 97 per cent of the world’s seaweed harvest.

Dr Alice Jones, Industry Research Fellow at the University of Adelaide’s School of Biological Sciences and lead author of the study, says the analysis provides clear, climate-friendly principles for the marine farming industry and governments.

“For fin-fish farming operations, the most critical practices to avoid emissions include improvements in feed efficiency, transitioning from using diesel fuels to renewable alternatives, and improved siting of operations to eliminate impacts to blue carbon habitats (coastal ecosystems such as mangroves, tidal marshes and seagrass meadows),” Dr Jones says.

“We also found that the increased interest in seaweed farming, as part of the aquaculture mix, has the potential to offset carbon emissions.

“Seaweeds are produced for both human and animal food as well as vari­ous other products, including carrageenan, agar, iodine, biofuels (biogas, biomethane) bioplastics and fertilisers.

“Seaweed aquaculture is an effective source of carbon sequestration and well-sited mariculture ventures, where seaweed is cultivated for the purpose of climate-friendly products, have the potential to deliver negative carbon emissions.”

For the consumer, the study shows that eating an increased proportion of farmed bivalves and seaweed could be a climate-change mitigating measure.

“Unlike other sources of protein, bivalves (such as mussels and oysters) and seaweed have little, or no emissions associated with the “upstream” phase of farm production—because they don’t require feeding” Dr Jones, Environment Institute member says.

“On-farm emissions are almost solely due to the fuel and infrastructure needed to raise the animals, and downstream emissions are associated with getting products packaged and shipped to the grocery or retail store.

“As consumers we can take a critical step in reducing emissions by being conscious of where our seafood comes from. We can eat more seafood and buy local, to reduce the need for packaging, refrigeration and transportation.” Dr Alice Johns, Industry Research Fellow at the University of Adelaide’s School of Biological Sciences

“As consumers we can take a critical step in reducing emissions by being conscious of where our seafood comes from. We can eat more seafood and buy local, to reduce the need for packaging, refrigeration and transportation.”

The paper explores other strategies for consideration and adoption including:

Develop climate friendly on-farm operations - shift to low-emissions energy sources, use or reuse low-emissions, durable materials for farming infrastructure; reduce nutrient inputs and wastes that lead to environmental GHG emissions; explore the use of biofuels and clean energy power sources on-farm.

Design operations to protect the environment - site fed finfish operations away from sensitive blue carbon habitats, out in deeper or faster flowing waters; minimise feed waste to the environment; adopt climate-friendly grow-out strategies for bivalves that minimise benthic disturbance and sediment resuspension; explore the potential for both bivalve and seaweed mariculture to indirectly support or enhance blue carbon sequestration.

Diversification to support reduced greenhouse gas emissions - co-farming bivalves with seaweed can lead to a net reduction in CO2 emissions and co-farming fed finfish with sea­weed or bivalves to absorb excess nutrients, can reduce eutrophication and related blue carbon habitat degradation.

Dr Jones says more needs to be done to develop improved evaluation tools for carbon off-setting for mariculture operations, in what can be complex industry-environmental interactions, to make the most of the climate-friendly seafood opportunity.

“What we do know is that globally this is a growth industry – growth of 7.5 per cent a year for the past 50 years,” she says.

Global Aquaculture Scientist at The Nature Conservancy and a lead co-author of the study, Dr Heidi Alleway, says the study could be game-changing not only for marine applications, but other types of food production as well.

“It is vital that we find ways to establish and grow the aquaculture industry sustainably. We know how to do this for marine aquaculture, and now we also know how to do this with climate mitigation and a net zero emissions future in mind,” Dr Alleway says.

“If these principles are adopted, there is an opportunity to shape marine aquaculture to be at the forefront in addressing climate change impacts from food production.”