21st February 2024

Aquaculture Feed – What are the impacts and what are the alternatives?


  • Aquaculture feeds are produced from marine and plant-based ingredients.
  • However, current sources of feed ingredients can have adverse effects to the environment.
  • To mitigate the environmental impacts of aquaculture feed as the industry continues to grow, it is essential that new alternative feed sources are developed and implemented.

 

As global salmon aquaculture continues to grow, so does the demand for nutritious and sustainable aquaculture feed. Feeds contain a variety of ingredients from both plant and marine sources. However, the environmental impacts associated with many commonly used ingredients, such as soy and fish meal, means that alternative ingredient sources are urgently needed to ensure impacts to the environment are mitigated.

What is farmed aquaculture feed made of?

A number of ingredients from multiple animal and plant sources are used to produce salmon feed. The proportions of ingredients used vary between producers and nations, however it has been estimated approximately 60-70% of salmon feed ingredients are from plant sources (e.g. soy, sunflower, rapeseed, corn and wheat), while approximately 20-40% is of marine origin (e.g. fish meal, fish oil, trimmings). Additional small amounts of supplements are also added (e.g. vitamins and minerals)(1–3).

Historically Scottish salmon feed has contained greater percentages of marine ingredients than many other salmon producing nations (e.g. Norway). This is in part to ensure high levels of Omega-3 are achieved in farmed Scottish salmon products (2). Industry trends indicate a falling reliance on marine ingredients in feeds, resulting in an increased use of non-marine sources, however, it is vital that the environmental impacts of alternative ingredients are also assessed(1,4).

The environmental impact of feed

Salmon aquaculture is often presented as a low carbon method of food production, however, feed is usually considered separately and can have a significant carbon footprint as well as wider reaching environmental impacts. It is estimated that fish feed represents 90% of fish farm gate green house gas (GHG) emissions (5,6).

The GHG emissions of feed vary between ingredients, though it is estimated that ~73% of GHG emissions from Scottish fish feed is from plant-based ingredients, with soy, rapeseed and wheat being highlighted as high emission sources(3,5). Soy is of particular note due to high emissions and environmental impacts resulting from land clearance for production, as well as agriculture and transportation emissions(7). Soy has been widely utilized as an alternative to fish meal in feed due to a high protein content, however as awareness of the environmental impacts associated with soy production use has grown, new alternatives have been increasingly sought.

Fish meal is commonly used in feed production to provide a source of protein, while fish oil is a source of omega-3 (an essential nutrient required for farmed fish production) in the farmed salmon diet (8). Fish meal and fish oil (FMFO) are predominantly sourced from wild forage fish, however concerns over ecological impacts and sustainability has led to alternative sources of protein and omega-3 being explored.

Microplastic and chemical contamination

Increasing concern over the presence of microplastics and chemical contamination in fish meal also highlights a need to transition to alternative sources of protein in feeds. Forage fish and bycatch used in feed are a route of microplastic into aquaculture systems (9–11). This microplastic can enter aquaculture feed via fish meal and transition along the food chain.

Chemical contamination in aquaculture fish has also been identified, with feed noted as an important route for the uptake of chemicals(12). These contaminants can enter the food chain via feed as well as from the surrounding environment. PFAS present in fish meal has also been identified as a source of contamination in the food chain, with further research urgently needed in this area (13).

What are the alternatives?

Efforts to reduce the GHG emissions and environmental impacts of aquaculture feed have included a move away from soy and fish meal and fish oil use, increasing use of locally sourced ingredients and reducing a reliance on plant-based ingredients.

A number of alternative sources of feed protein have been investigated. In some nations it has become increasingly common for trimmings (i.e. fish by-products) to be utilized as a source of marine protein in feed, however, consistent quality and availability is an issue.

The use of insect meal has been suggested as an alternative, providing a comparable protein content to fish meal and greater than soy (50-80% protein content compared to 60-68% of fish meal and 48% of soy meal)(7). Research has indicated that insects could provide an effective source of protein and amino acids in fish diets, with relatively low environmental impacts compared to soy or fish meal and is becoming increasingly competitively priced. However, current capacity to produce large volumes of insect meal is limited, while consumer perception is an issue too.

Single celled proteins (SCP) such as algae, and fungi have been explored as another alternative protein source, with advantages over soy including reduced land and water demand and protein content of 50-70%(14). SCPs have good potential to provide a sustainable protein source, however current issues of scaling and economic costs are  key barriers to widespread adoption in feed production.

Omega-3 in farmed fish diets is mainly sourced from fish oil, however many plant alternatives do not provide a sufficient source of omega-3. This has been a bottleneck in the transition away from marine ingredients, however development of alternative sources of omega-3 is progressing. In Norway some industrially produced algae sources have been adopted in feed production, while genetically modified oilseed crops (e.g. canola oil) have also been explored and approved for use (5,15,16).

 Summary

Sustainable feed ingredients are essential to limit the environmental impacts of aquaculture. Though progress has been made in reducing the proportion of marine ingredients used in feed, many currently used alternatives bring their own environmental challenges. As the industry continues to grow, so too will the demand for feed.  It is therefore essential that sustainable alternatives to feed ingredients are invested in and adopted to mitigate these impacts going forward.

 

References

  1. Jones A. How can retail and supply chains support demand for more sustainable aquaculture feed? Nuffield Farming Trust. Nuffield Farming; 2023. Available from: https://www.nuffieldscholar.org/sites/default/files/2023-09/Aisla%20Jones%20Nuffield%20scholarship%20report%20September%202023%20%28AP%29.pdf
  2. Shepherd CJ, Monroig O, Tocher DR. Future availability of raw materials for salmon feeds and supply chain implications: The case of Scottish farmed salmon. Aquaculture. 2017 Jan 20;467:49–62. Available from https://doi.org/10.1016/j.aquaculture.2016.08.021
  3. Monterey Bay Aquarium Seafood Watch. Atlantic Salmon – Scotland Marine Net Pens [Internet]. 2021 [cited 2024 Feb 14]. Available from: https://www.seafoodwatch.org/globalassets/sfw-data-blocks/reports/s/mba_seafoodwatch_atlantic_salmon_scotland.pdf
  4. Eroldoğan OT, Glencross B, Novoveska L, Gaudêncio SP, Rinkevich B, Varese GC, et al. From the sea to aquafeed: A perspective overview. Rev Aquac. 2023;15(3):1028–57. Available from: https://doi.org/10.1111/raq.12740
  5. McGoohan A, Tait J, Raybould A, Parris S, Hammond K. Fish farming in Scotland: Optimising its contribution to climate and environmental policies. 2023. Available from: https://www.innogen.ac.uk/sites/default/files/2021-08/Scottish%20Aquaculture%20Innovations_OU%20Executive%20Summary.pdf
  6. Hammer AJ, Millar C, Hennige SJ. Reducing carbon emissions in aquaculture: Using Carbon Disclosures to identify unbalanced mitigation strategies. Environ Impact Assess Rev [Internet]. 2022;96:106816. Available from: https://doi.org/10.1016/j.eiar.2022.106816
  7. WWF. THE FUTURE OF FEED: A WWF roadmap to accelerating insect protien in UK feeds [Internet]. 2021 [cited 2024 Feb 14]. Available from: https://www.wwf.org.uk/sites/default/files/2021-06/The_future_of_feed_July_2021.pdf
  8. Froehlich HE, Jacobsen NS, Essington TE, Clavelle T, Halpern BS. Avoiding the ecological limits of forage fish for fed aquaculture. Nat Sustain [Internet]. 2018;1(6):298–303. Available from: https://doi.org/10.1038/s41893-018-0077-1
  9. Mahamud AGMSU, Anu MS, Baroi A, Datta A, Khan MSU, Rahman M, et al. Microplastics in fishmeal: A threatening issue for sustainable aquaculture and human health. Aquac Rep [Internet]. 2022;25:101205. Available from: https://doi.org/10.1016/j.aqrep.2022.101205
  10. Thiele CJ, Hudson MD, Russell AE, Saluveer M, Sidaoui-Haddad G. Microplastics in fish and fishmeal: an emerging environmental challenge? Sci Rep [Internet]. 2021;11(1):2045. Available from: https://doi.org/10.1038/s41598-021-81499-8
  11. Wang Q, Li J, Zhu X, Sun C, Teng J, Chen L, et al. Microplastics in fish meals: An exposure route for aquaculture animals. Science of The Total Environment [Internet]. 2022;807:151049. Available from: https://doi.org/10.1016/j.scitotenv.2021.151049
  12. Henríquez-Hernández LA, Montero D, Camacho M, Ginés R, Boada LD, Ramírez Bordón B, et al. Comparative analysis of selected semi-persistent and emerging pollutants in wild-caught fish and aquaculture associated fish using Bogue (Boops boops) as sentinel species. Science of The Total Environment [Internet]. 2017;581–582:199–208. Available from: https://doi.org/10.1016/j.scitotenv.2016.12.107
  13. Li X, Dong S, Zhang W, Fan X, Wang R, Wang P, et al. The occurrence of perfluoroalkyl acids in an important feed material (fishmeal) and its potential risk through the farm-to-fork pathway to humans. J Hazard Mater [Internet]. 2019;367:559–67. Available from: https://doi.org/10.1016/j.jhazmat.2018.12.103
  14. Pereira AG, Fraga-Corral M, Garcia-Oliveira P, Otero P, Soria-Lopez A, Cassani L, et al. Single-Cell Proteins Obtained by Circular Economy Intended as a Feed Ingredient in Aquaculture. Foods [Internet]. 2022;11(18). Available from: https://doi.org/10.1016/j.jhazmat.2018.12.103
  15. Marine Conservation Society. Using microalgae in sustainable aquaculture [Internet]. 2021 [cited 2024 Feb 15]. Available from: https://www.mcsuk.org/news/using-microalgae-in-sustainable-aquaculture/
  16. Hatlen B, Larsson T, Østbye TK, Romarheim OH, Rubio LM, Ruyter B. Improved fillet quality in harvest-size Atlantic salmon fed high n-3 canola oil as a DHA-source. Aquaculture [Internet]. 2022;560:738555. Available from: https://doi.org/10.1016/j.aquaculture.2022.738555