Aquaculture became a hot-topic from the moment when we discovered several threats are linked to this farming. As our global population continues to grow, we need more food, and notably fish. According to the Food and Agriculture Organization of the United Nations (FAO), more than 10% of the world's population depends on fish as their main source of animal protein. Nevertheless, fisheries have closed their eyes on various issues (eyes on sanitary, ecological and even ethical issues).
This culture needs huge quantities of food to feed all fish populations. For example, to feed salmon or trout, we need flour and oil from other fish, which are caught by trawlers. These boats are damaging the seabed and leaving nothing for other species (birds, seals, whales, … ).
Fish farming stocks fish in very high densities, promoting stress and the spread of disease. In this case, it is easy for diseases or parasites to develop. The media shared images of salmon “piled up” and injured. Wounds are due to sea lice (small crustaceans) that feed on their flesh.To limit this risk, farmers treat animals with antibiotics, antifungals, and other pesticides, which are subsequently found in their flesh. In addition to the risk of infection for a human, parasites can spread to wild populations of fish. Indeed, it appears that fish flee the farms throught holes in the nets, then transmitting their diseases and chemical infection to healthy ones.
Intensive farming also includes big areas, oftentimes originally wild, but then transformed and degraded by industries. In the case of shrimp farming, mostly taking place in Asia, mangroves are destroyed then deserted three to five years later, because of the gradual formation of toxic sludge at the bottom of the ponds (a mixture of excrement and chemicals), which leaves an area unsuitable for any other use. Another example, according to Greenpace ONG, a typical salmon farm with 200,000 salmon produces the same amount of fecal matter as a city of 62,000 inhabitants.
In response to this, scientists and biologists are now developing solutions, to allow more ethical, ecological and sustainalble ways of production.
Focus on several projects :
- Mastering the closed-loop system
Closed basins are the most common way of farming fish. Finding solutions in this sector should notably reduce pollution in the ocean. So how does it work ?
Three points are developed here. Firstly, a closed irrigation system, the “recirculating aquaculture systems” (RAS), treats and reuses water in a cycle. This approach could reduce water pollution and protect habitats near marine farms (because avoid to reject diseases or chemical products). Also, sensors help to regulate water settings as nutrient levels, and avoid overdose of harmful products. Secondly, this type of farm has found alternatives for traditionnal feeding ressources (fish oil and flour), using insect proteins, microalgae and fermented ingredients. Intakes are the same for fish, but allow to no longer depend on fisheries, and therefore cause less damage to marine ecosystems. Thirdly, another interesting point concerns waste recycling. By using a new technique, the integrated multi-trophic aquaculture (IMTA), the closed-loop system combines fish, seaweeds and bivalves (shells) to create a sustainable farming environnement. For example, nutrients from fecal matter are absorbed by plants, which grow and create a habitat for shellfish whose role is to recycle water by removing pollutants.
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Focus in Ireland : An oyster farm cleans more than a wastewater treatment plant
Indeed, shellfish are able to recycle water. This phenomenum has been studied by a scientific team for the University of Galway. They discovered that an oyster farm cleans more than a wastewater treatment plant for 10,000 people each year. Oyster [Magallana gigas species] is able to eliminate on average 2.36 kilos of nutrients expressed in phosphorus equivalent, which is about six times more than the pollution linked to the operation itself. In addition, oysters need carbon to grow, which represents the equivalent of 73% of the production of carbon from the farming cycle. In comparison to the impact of other types of farm, that's about one-tenth of beef and about one-quarter of chicken.
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Healthy and sustainable aquaculture with aqua-biomimicry
To complete our previous points, a French scientist with a PhD in Anthropobiology, Philippe Stefanini, theorized a new way of production : the aqua-biomimicry. His work proposes a return to non-industrial farms, by enhacing the natural system. Indeed, whereas our manner of raising fish is intensive and needs a lot of technical adjustments (chemical, technological, … ), the scientist says that Nature is able to produce matter alone, and autoregulate it. In this case, we should rebuild the real ecosystem, with natural actors (fish, seaweeds, bivalves, …) and let things take their course. “The central idea is to turn the tables : aquaculture production should no longer be an isolated end, imposed on the environment, but the natural by-product of a functional and self-regulating aquatic ecosystem", said P.Stefanini. In this form of ecosystem, one major actor is the microbiota (sediments and biofilms). This microorganism doesn’t interest the actual farms which destroyed / biosynthetically replaced it. But in nature, it acts as a biological filter and an immune shield, limiting the establishment of pathogens and therefore, limits the need of sanitary chemicals while strengthening the robustness of the species.
A well-known example is the Kush Shellfish Seafarm (located in Co.kerry), first organic rope mussels producer. They are farming mussels on recycled ropes and biodegradable materials, in a protected bay site. Water is checked every month to guarantee a healthy environnement. They simply use phytoplankton as food for the shells and don’t need any chemical produce. In addition, this project is supported by the EIM and European subventions.
These discoveries look encouraging and reassuring for the future. Now, we need to find alternatives to traditional ways of aqua-production, which are only representing threats for us and our environnement.
To go further you can read the posters created by NOAA Fisheries :
- https://www.fisheries.noaa.gov/s3//2022-03/Fact-Sheet-Aquaculture-Provides-Beneficial-Ecosystem-Services.pdf
- https://www.fisheries.noaa.gov/s3//2022-03/Fact-Sheet-Sustainable-Aquaculture-Feeds-and-Fish-Nutrition.pdf
- https://www.fisheries.noaa.gov/s3//2022-03/Fact-Sheet-Aquaculture-and-Environmental-Interactions.pdf
Sources and credits :
Definition of the subject : https://oceanfdn.org/fr/sustainable-aquaculture/
Definition of Sustainable aquaculture : https://www.eelink.net/biodiversite-nature/aquaculture-circuit-ferme/#aquaculture-durable-et-circuit-ferme-maitriser-le-systeme-ras-pour-reduire-limpact-sur-la-biodiversite-marine
Definition of biomimicry : https://www.goodplanet.info/2026/02/17/une-aquaculture-saine-et-durable-avec-laqua-biomimetisme/
Oyster farm in Ireland : https://www.especes-menacees.fr/demonstration-en-irlande-avec-une-analyse-du-cycle-de-vie-total-une-ferme-ostreicole-nettoie-plus-quune-station-depuration-pour-10-000-personnes-et-le-service-environnemental-vaut-2-millio/
Actual threats of aquaculture : https://www.viande.info/aquaculture#biblio
Mussels farm in Ireland : https://www.youtube.com/watch?v=H5x5HuXs94k
Head Picture : © WaterFrame/Alamy Stock Photo
Picture 1 : © Getty Images/Dudits
Picture 2 : © Corin Smith
Picture 3 : © Marcos Pin
Picture 4 : © E&E website
Picture 5 : © Judith Oakley
Picture 6 : © St Andrews