Design of marine ecosystems: Integrated Multitrophic Aquaculture
A method of designing ecosystems to produce fish, algae and shellfish taking inspiration from nature
This article has been translated with Google Translate. You may find language incoherences but we hope your comprehension won’t be compromised.
Fish, crustaceans, shellfish and even algae: we are consuming more and more products from the sea. In order to avoid overfishing, intensive aquaculture has developed strongly over the past 50 years. In 2016, more than half of seafood products came from this production method. Have we solved the problems of overfishing? Only partly and although we have succeeded in reducing the problems of overfishing, other problems have arisen: destruction of habitats, reduction in water quality, disappearance of mangroves …
These problems come from the pressure exerted by aquaculture on the environment: the concentration of a species generates waste that the environment is not able to assimilate. Concretely, when fish are fed, their droppings fall to the sea floor and dissolve in the water. In nature, seashells clean the sea floor and algae consume dissolved elements. In intensive aquaculture, there is too much manure and the quality of the environment deteriorates.
This is where integrated multitrophic aquaculture emerges. Behind this barbaric name hides a production method well known to permaculturalists: the reproduction of an ecosystem with complementary species. Instead of letting the environment fend for itself to deal with the droppings, we help it by adding shellfish and crustaceans under the fish to consume the excess organic matter. To treat dissolved matter, we add algae that feeds on it around the fish. This recreates the functioning of a normal balanced ecosystem in which the food of some is the waste of others!
Here is an example of an ecosystem considered and studied at the Paul Ricard Institute. The aquaculturist feeds the fish whose droppings partly feed sea urchins and mussels. Sea worms absorb the small organic particles that sea urchins and mussels let through, and algae consume the inorganic part of the droppings of all animals in the ecosystem. In this way, the institute manages to maintain and stabilize the quality of the water over time.
In practice, the Symbiomer company in Brittany uses these concepts with trout, scallops and seaweed that they produce for the cosmetics industry. They were able to demonstrate that their production model was sustainable ecologically but also economically! Everything is explained in this video 👇 (in French, but you can use Youtube subtitles)
As Symbiomer executives point out, it is best to design ecosystems with local species to reduce the chances of the increased pressure on the environment that occurs when a cultivated species manages to escape. This is why much research is underway, especially in Canada, to design ecosystems centered around the most consumed fish such as salmon or trout, using only species endemic to a given region. This helps reduce the risks of introducing a new species into a stabilized environment by reducing the number of « alien species » used.
This example shows us that the principles of permaculture can be applied in very different areas of the garden or market gardening. Integrated multitrophic aquaculture responds to the principles of observation of nature, creation of production, waste recovery, integration of elements in favor of synergies and increase in biodiversity, while drawing inspiration from the nature ! Even if an aquaculturist does not claim to be permaculture, we can see that the links with this movement are numerous.