Populational status of the endangered mollusc Patella ferruginea Gmelin, 1791 (Gastropoda, Patellidae) on Algerian islands (SW Mediterranean)

Populational status of the endangered mollusc Patella ferruginea Gmelin, 1791 (Gastropoda, Patellidae) on Algerian islands (SW Mediterranean)Patella ferruginea is the most endangered endemic marine inverte¬brate on the Western Mediterranean coasts according to the European Council Directive 92/43/EEC. A total of 1,017 individuals were recorded in the present study along western Algerian islands, with mean densities ranging from 0.8 to 35.3 ind/m per linear transect and averages of 4.8 ind/m per linear transect for Western Habibas Island and 22 ind/m for Plane Island, making these islands a hot spot for the species in the Medi¬terranean. The expected total number of specimens in Habibas would therefore be 50,400. The mean size of P. ferruginea on the Habibas Islands (4.45 cm) was significantly (p < 0.001) greater than on Plane Island (2.78 cm). Recruitment was high in Plane Island and the northern sector of the western Habibas Islands. Lar¬ge adults had very conical shells. The fact that Habibas Islands is now a marine reserve could explain these differences in populations. Conservation of these populations should be a priority in order to avoid extinction of the species