Cartography and spatial distribution of natural deposit of sea urchin Paracentrotus Lividus Lamarck, 1816 (Echinodermata Echinoidea) in the region between El Jadida and Safi

A companion assessment of natural accumulation of sea urchin Paracentrotus lividus realized in June 2009 inthe region of El Jadida-Safi. This assessment has revealed the existence of a coast-wide gradient of density andsize that proportionate inversely with 80% of individuals covering the first 10 m while individuals ofintermediate size and large live in medium to large depths. In contrast this study clearly reveals theinterrelationship urchin / algae on one hand and the nutritional aggregation on the other hand. It notes thatyoung individuals whose size 30 mm are generally fed of Ulva lactuca, Halopitys incurvus, Cystoseirabaccata and Bifurcaria bifurcata. While Gracilaria multipartita, Laminaria digitata, Plocamium cartilagineumand Geliduim sesquipedale are feeding individuals of average size. Plocamium cartilagineum and Geliduimsesquipedalen which persist in the great depths feed bigger echinoids.