Spatio-temporal monitoring and modeling approach for the sustainable management of Paracentrotus lividus populations in the Mediterranean Sea

Paracentrotus lividus has a key ecological role in Mediterranean coastal ecosystems, yet its populations are declining in several regions. Understanding the environmental drivers of its distribution is essential for effective conservation. This study combines a decade-long population assessment (2013–2022) in Corsica Island (France) with species distribution modeling using Boosted Regression Trees (BRT). Field surveys at eight sites analyzed population densities by size class and environmental variables over the studied period. Nine additional sites were monitored since 2021 to complete the database for BRT modeling. Key predictors were used to understand and predict habitat suitability for P. lividus, such as infralittoral rocky substrates, depth, salinity, sea surface temperature and temperature anomalies. This study highlights that sea urchin densities declined significantly at most sites, with Southern locations maintaining higher abundances. One northern site exhibited persistently low densities, likely due to past overexploitation and habitat degradation. Over the monitoring period, 'large' sea urchins declined by 54–79 % and 'medium' ones by 72–100 %, with sharp decreases after 2016. These trends correlate with increasing marine heatwaves, suggesting thermal stress as a contributing factor. This hypothesis is supported by the BRT model results. The main influencing predictors were the presence of rocky substrates, followed by depth and the frequency of temperature anomalies. This study highlights severe population declines and underscores the need for localized conservation strategies. Reinforcing no-take zones and co-management efforts, integrating ecological data with adaptive policies, is critical to ensuring P. lividus resilience in the Mediterranean.