A Grouper basks in front of an artificial reef which represents for him a good hiding place -

François Launay

  • A vast study, led by Ifremer in the harbor of Toulon, aims to determine the effectiveness of artificial reefs.

  • This four-year study is unprecedented in its scope.

Artificial reef projects are legion on the French coasts, but are they really effective?

A vast study, led by Ifremer in the harbor of Toulon, will attempt to objectify these installations which lack feedback.

Along the oceanographic quay of the French Research Institute for the Exploitation of the Sea (Ifremer), you just have to bend down to see artificial seagrass, imitated posidonia in polypropylene, and below, concrete blocks, made in 3D printing, acting as rocks to shelter juvenile fish.

A degraded area

Since they were installed in June, researchers have observed 944 individuals from 28 species, including six heritage ones such as sar, wrasse, wolf, sea bream, details Marc Bouchoucha, ecologist engineer at Ifremer.

But how will this new abundance and biodiversity affect fish stocks?

How many artificial reefs are needed to rehabilitate 100% artificialized and degraded areas such as the port of Toulon, contaminated with lead, mercury, copper?

Tires submerged in the 1980s

To measure it, researchers have created a digital twin of the harbor, installed continuous fish size measurement tools and will deploy rotating video stations outside the port.

Because if the juvenile fish are naturally brought back to the coast by the currents, what do they become once they are adults?

Should man deploy a marine corridor for them? Asks Marc Bouchoucha, for example.

Since 1960, many initiatives have multiplied, especially in the Mediterranean, sometimes with heresies, such as submerged tires in the 1980s. Since then, perfected processes have been developed such as those of the Montpellier start-up Seaboost, partner of the study conducted in Toulon.

But in 2012, a State report deplored the lack of sufficient experience feedback to "draw definitive lessons".

"Today, we are solid in saying that when we equip a structure, we promote the return of life", confirms Julien Dalle, project director at Seaboost, who for example equipped the port of Marseille or Cap d ' Agde.

He hopes that the study, carried out by Ifremer, Seaboost but also the metropolis of Toulon and the CCI of Var, manager of the port, "will make it possible to better identify the repercussions of such installations and their calibration".

The four-year study is unprecedented in terms of the scale of the experimental reefs installed (3 stations of 50 m2 each) and the frequency of monitoring.

It will take two years to refine the observations and make recommendations on the conduct of such projects.

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  • Mediterranean

  • Toulon

  • study

  • Fish

  • Biodiversity

  • Sea