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

Abstract

Patella ferruginea is the most endangered endemic marine inverte­brate 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 Medi­terranean. 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. Lar­ge 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.