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Sea urchin (management)

Observation et comptage d'oursins.
Observation et comptage d’oursins.
Oursin comestible <i>Paracentrotus lividus</i> dans l'herbier de Posidonie.
Oursin comestible Paracentrotus lividus dans l’herbier de Posidonie.

The edible sea urchin, Paracentrotus lividus, is much prized from the gastronomic point of view. This ‘caviar of the sea’ is fished by regulated commercial fishing, practised by snorkel divers or scuba divers, depending on the maritime area.

According to certain professional Mediterranean fishers, there has over the past few years been a decline in adult populations, to a greater or lesser extent according to the sector.

At the request of professional fishers, the Paul Ricard Oceanography Institute has launched a programme aimed at getting to know more about the species Paracentrotus lividus, assessing the state of the resource and improving its management. The experimental repopulation approach is being explored.

Scientifically, the work involves :
-  field work to assess the real state of the resource by carrying out counts of individuals at several sites in the region, and monitoring changes over time and space.
-  experimental work to study the feasibility of repopulation : production of juveniles, conditions of release into the sea, etc., effectiveness, ecological impact on the resource and on the natural biocenoses.

Repopulation trials
Planned at five sites in the Toulon region, two of them around Les Embiez, experimental release into the sea was carried out in 2010 and 2011. For this experiment, 1 500 000 juveniles of sea urchin were produced in the Paul Ricard Oceanography Institute hatchery.

But the question remains whether the sea urchins that are found after one or two years at these sites are indeed the result of these releases. Marking individuals of one or two millimetres is not possible, whence the idea of investigating the parenthood by means of genetic markers performed by the B2M team at the PROTÉE laboratory, University of South Toulon–Var.

Molecular tools will enable the analysis of populations at the various stations, the establishment of an identity card of the parenthood of the breeders used and the development of a paternity test allowing recognition of individuals at a site after release.

- University of South Toulon–Var B 2M team, PROTÉE laboratory (Dr. Joël Grillasca).

-  Toulon Provence Méditerranée (TPM) local authority
-  Caisse d’Épargne Côte d’Azur

> Watch the film on the opening page of the Research section : The Sea Urchin Programme (7mn 30s))

Functional schema of the experimental hatchery
(Technical design by Philippe Aublanc, drawings by Marine Delvil)