Is oyster farming eco-friendly?

Oct 9 · 5 min read

Oyster (and other bivalve) farming is the only fish farming activity that does not require an Environmental Impact Study in Portugal. This is because the Government itself acknowledges the neutral and positive impact that it has on the environment.

Francisco Bernardino, the CEO of Oysterworld and marine biologist, explains in this article the scientific and technical side of the positive impact linked to oyster production in restoring ecosystem balance, absorbing CO2 and acting as a natural biofilter.

Why Neutral?

It is considered as having a neutral impact firstly because oysters do not need processed animal food in order to grow. Their food (plankton) is naturally found in aquatic environments, therefore avoiding both the artificial introduction of nutrients and/or the extraction of resources to produce its own food.

Secondly, this type of production does not use any antibiotics, vaccines nor other types of chemical products.

Last but not least (and this can be considered more as a positive aspect as opposed to neutral), oyster farming reduces the need to extract oysters from natural banks. This is particularly relevant because the existing natural banks in Portugal are fragile and need to recover from extensive farming. It is also important to remember that until the 70’s, Portugal was the main oyster supplier in Europe — natural oyster banks of the River Sado and the River Tejo produced thousands of tonnes per year. Unfortunately, industrial and naval production with no environmental concerns polluted waters so much that oysters became extinct in the Tejo and only a few natural banks remained in the Sado. It was only recently that these natural banks started to expand, which is a very good indicator that the water quality is beginning to improve.

Why Positive?

Oceans and forests are the biggest absorbers of CO2 (long term carbon capturing from the atmosphere) that is released in the atmosphere. Because they are living beings, forests and algae hold carbon for a limited time period since when they decompose, the carbon is released again.

With bivalve that is not the case. Bivalve shell is made from calcium carbonate (CaCO3), which means that carbon is mineralized and solidified. It is therefore very difficult to be released back into the environment.

In practice, a massive bivalve production could give Earth its equilibrium back, not only by absorbing CO2 from the atmosphere, but also by absorbing the amount already absorbed by the oceans contributing to its acidification. It would be killing two birds with one stone: environmental equilibrium and a huge source of healthy protein. The biggest challenges for a project like this are simply the cost implications and technical difficulties related to producing it in the open sea (yes, it would need to be in the open sea).

Natural Biofilter

Bivalve have the capacity to remove bacteria, pollutants, nutrients, microalgae and small particles (eg. mud) from water. They are a fundamental piece to guarantee the healthy equilibrium in the marine ecosystem. In estuaries like the Sado, where there are large amounts of nutrients (and therefore oysters grow really fast hence the large quantity up until the 70’s), bivalve are very important to maintain the equilibrium and avoid environment deterioration. The natural banks are currently “dead” and completely submerged by mud, which would not happen if oysters were alive.

More than a decade ago, the United States of America have launched many programmes to recover and re-introduce bivalve in their estuaries. This is due to the logical conclusion that it is the most efficient, cheap and ecological way to restore their ecosystems equilibrium.

But there’s no need to go to the other side of the Atlantic Ocean to see the benefits of bivalve production. Spain streams in Galicia produce around 100 thousand tons of mussels per year. Both producers and scientists agree that without this production their water quality would be much worse.

Obviously, such a big monoculture brings about other problems but it still is of utmost importance to the water quality maintenance.

Artificial Reefs

It is unquestionable that natural reefs are beneficial to the environment, whether located in concrete or in sunken vessels. First, it is important to understand that open sea or sand banks are the equivalent to an extremely fertile land area which is desert because nothing permanently fixes (let’s blame the wind).

These areas are the most adequate ones to bivalve production because their food is water, and they allow for the boats circulation and the production infrastructure. These structures (iron tables, long-lines, etc…) will allow animals and plants to establish themselves and habitats to expand, increasing the natural productivity of the location.

The first time I watched this with my own eyes was in 2002, when diving in Sagres, where long-lines for oyster farming were in place (open sea but very close to the coast). The structure was installed in 1996 and the quantity of fish there was notorious. Fishermen who initially were against the installation of these structures but started welcoming them and asking for more to be installed!

There are various articles that prove this is the most interesting benefit of oyster farming, the best one being the Assessment of the Value of Shellfish Aquaculture in the Gulf of Mexico as a Habitat for Commercial and Recreational Fish Species, published by Auburn University. The monetary value associated with the positive impact of bivalve production in activities like extractive fishing is well explained in this article.

Francisco Bernardino - Founder and Chief Scientific Officer of Oysterworld

Francisco holds a Master in Marine Biology, and has always worked in the sector, having developed several consulting projects and participated in 2 aquaculture startups. Along his journey, he had the opportunity to develop offshore production projects, develop aquaculture viability studies, oyster production circles, to name a few.

About the project

Oysterworld is an oyster farming company with a production area of 18 ha in Setúbal. With the main goal of expanding its productive capacity to 360 tons per year, the project’s global investment is 2,1 M €. The company is setting up a group of crowdlending campaigns for a total of 1,07 M €.

Oysterworld’s project I was the first one available for investment as one of GoParity projects. It offered a yearly interest rate of 5,20% with a 2-year length. The sum of €120.000,00 was raised by 281 investors. As the first project turned out to be very successful, GoParity lunched Oysterworld’s project II, this time with a total amount of €150.000,00, raised by 358 investors.

For more information, please check:

Currently you can invest in the 3rd project of Oysterworld. After the successful funding of Oysterworld's previous projects, 30% of the total investment has already been invested and implemented.

This third stage of the investment hopes to complement and fasten the other components, like:

  • Production and supporting equipment
  • Soil transactions
  • Floodgates

Please check more information here:


GoParity is an impact financial platform, connecting sustainable project promoters looking for funding with a community of conscious investors willing to make money for good.


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GoParity is an impact investment platform that empowers people to save and make money by investing in impactful projects.



GoParity is an impact financial platform, connecting sustainable project promoters looking for funding with a community of conscious investors willing to make money for good.

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