In recent years, starfish have colonized the bays of Brittany. They are voracious, devouring mussels, oysters, and other shellfish, much to the dismay of local shellfish farmers. Researchers are now trying to find ways to turn these “little ladies” from what seems like a plague into a useful resource.
[Originally published on April 5, 2025]
For the year 2023 alone, scientists estimated that in the bays of Concarneau and Douarnenez, starfish represented a biomass of 1,300 tons—likely thousands of tons across French waters.
Considering that a single starfish can consume up to 10 mollusks in 24 hours, shellfish farmers have good reason to worry.
Guillaume Nicolle, a mussel farmer, cultivates rope-grown mussels and witnesses the starfish’s voracious appetite daily. Between the starfish and seabream, 30 to 40% of his mussels are eaten. “Starfish are predators for us,” he says. “There is a regulation in Finistère that calls for the destruction of this species, which is considered invasive.”
In 2022, scientists estimated the starfish biomass in the bays of Concarneau and Douarnenez at 1,300 tons.
An Invasive Species Without Predators
In recent years, Nicolle has seen starfish proliferate with no solution in sight. They have no natural predators, and their larvae, carried by currents, develop even inside protective nets.
Currently, the only method for the mussel farmer is to remove them by hand. Once brought ashore, the starfish are incinerated as ordinary waste.
Yet scientists are convinced these starfish have “magical” properties waiting to be discovered.
A Project to Valorize Starfish
Since 2021, fishermen and scientists from the Concarneau Natural History Museum have been working together on the Valasterid project to find ways to make use of starfish.
The biomass was first quantified, followed by a targeted fishing campaign in the Bay of Quiberon. “In just 1.5 hours, one ton of starfish was collected—it’s remarkable,” explains Maxime Kéraudran, coordinator of the starfish projects at the Concarneau marine station.
In laboratories, scientists have been studying their properties. Starfish could potentially be used in medicine, treatments for cancer and inflammatory diseases, cosmetics, biomaterials, or animal feed.
At the Roullier Group in Saint-Malo, a machine that simulates a cow’s stomach was designed: researchers place fodder and a molecule derived from starfish to test whether it can improve the digestibility of the feed. This is crucial because if animals better absorb their rations, they could produce more milk or meat.
Other experiments are conducted with plants: could starfish-derived compounds help them resist water or heat stress caused by climate change?
Promising Studies
The studies are ongoing, but if successful, they could turn the “enemy” starfish into an opportunity. Fishermen might even be paid to collect them.
The first results are promising, but scientists remain cautious. “Starfish have a role to play in their ecosystem,” warns Maxime Kéraudran. “The idea is not to endanger starfish populations but to find a balance. This resource, currently wasted, needs to be transformed into something useful.”
