EXPERIMENTAL RELEASE OF JUVENILE SEA URCHINS (PARACENTROTUS LIVIDUS) IN EXPLOITED SITES ALONG THE FRENCH MEDITERRANEAN COAST

During the past 40 y, natural stocks of the edible sea urchin Paracentrotus lividus have declined sharply in many sites along the French Mediterranean coast. Despite current management measures, this resource remains at low densities, raising concerns among commercial fishermen and managers. The reseeding of depleted sea urchin populations is currently under consideration. In this study, a pilot-scale experiment was conducted to assess the feasibility of such an operation and to evaluate the impact on both the population structure and genetic diversity of wild communities. The genetic diversity and population differentiation of wild populations was assessed before reseeding five depleted populations with 250,000 hatchery-produced juveniles. A year after release, parentage assignment tests were performed on small recaptured sea urchins to address their origin. Sea urchins from the hatchery were found at two of five sites, representing 3% and 12% of the total recaptured urchins in the concerned sites. The genetic analysis performed with six microsatellite loci revealed genetically homogeneous populations in the area studied. Within and among populations, genetic diversity seems not to be affected by introducing juveniles from the hatchery into wild populations. Therefore, following strict recommendations, reseeding could be considered a potential and efficient management tool to restock or sustain overexploited populations in areas where natural recruitment appears insufficient.