Les 4 Marais : when aquaculture is reinvented in salt marshes

Imagine a basin where fish, mussels, sea worms, sea lettuce and all different species live together and, above all, complement each other. Each has a role to play in water filtration, production and purification. Les 4 Marais, awarded the “Agriculture” prize by Futur(e)s Food, cultivates a unique ecosystem that requires few inputs while generating a varied and rich production. The system uses 1.5 kg of granules to produce not only 1kg of sea bass, but also 2 kg of mussels, 400 g of sea worms and 4 kg of sea lettuce – quantities that illustrate the bio­ -efficiency of the model. “This approach is guaranteed to boost productivity on small surfaces,” explains the system’s designer Thomas Miard, “while reinforcing the ecosystem’s resilience in the face of environmental fluctuations.”

Les 4 Marais was born of a reflection, almost a personal challenge, for this researcher with a passion for natural ecosystems. He designed a system that mimics a closed-circuit food chain, allowing each species to contribute to the balance of the whole. “Everything is interconnected. In fact, what we’re doing is simply co-piloting nature,” explains Thomas with humility, seeing in this model the promise of resilient aquaculture. Indeed, in the case of extreme conditions, such as a plunge in water salinity or periods of drought, the integrated ecosystem adapts, compensating for any losses. A precious balance in a context of increasingly frequent and intense climate change. “With global warming, we’re going to have to adapt to periods of extremes. This type of breeding enables us to maintain a stable production even in the event of environmental fluctuations,” explains Thomas.

From shrimp to samphire
However, developing and mastering this model comes with challenges. Thomas has spent years fine-tuning his basins, and the interconnection of species requires multidisciplinary expertise: “You have to be a biologist, an aquaculturist, a botanist and even something of a chemist.” But versatility pays off: with nine species currently produced, Les 4 Marais is able to offer a wide range of products, from shrimp to samphire and highly prized edible seaweed. Despite its undeniable advantages, this model remains rare, as it challenges the conventional practices of well-established monoculture aquaculture. Yet Thomas Miard is convinced that, with Les 4 Marais, he has paved the way for a model that can be replicated worldwide. Whether the water is fresh water, salt water or brackish, whether the species are local or exotic, this multi-trophic system can integrate any type of species into a circuit of cohabitation and interdependence. By modulating the species, every basin in the world could recreate a sustainable ecosystem, and thus help aquaculture evolve to meet the urgent challenges concerning food and the environment.

“The idea is to turn it into a global model,” explains Thomas, who sees in this method an alternative for the regions of the world most vulnerable to the resource crisis. Imagine an aquaculture that is self-regulating, produces in a sustainable manner and limits waste: that’s the message behind this project, which Thomas hopes to see widely disseminated, thanks to the visibility offered by the Futur(e)s Food initiative. “Aquaculture can be something other than a polluting, energy-guzzling industry. This award is one more step towards getting things moving and inspiring the sector to take the turn towards balance and sustainability.”

By Alice Polack et Jean-Pierre Montanay