The Importance of Small Mediterranean Islands as Refuge for the Endangered Species as Patella ferruginea: Case of Sebiat Island

The aim of this study was to validate the biodiversity potential and assess the conservation value of Sebiat Island (also known as Gerardi Island), with a view to its possible integration into the Mediterranean small islands network. The results revealed the presence of a relatively large population of Patella ferruginea—724 individuals, with a density of 1.09 ind/m. The significant presence of juveniles is a critical indicator of active recruitment and population renewal within the study area. However, the absence of very large individuals suggests anthropogenic pressure, as poachers typically target specimens larger than 60 mm in length. In addition to P. ferruginea, several other endangered and ecologically important species were identified on the island. These include the red calcareous alga Lithophyllum byssoides, the brown algae Cystoseira spp., and fragile habitats such as vermetid bioconstructions formed by the sessile gastropod Dendropoma lebeche, as well as Posidonia oceanica meadows in the sublittoral zone. Given the island's rich biodiversity and ecological value, the establishment of a formal protection plan is recommended to ensure the long-term conservation of Sebiat Island and its unique marine habitats.