Pinna nobilis L., 1758 (Mollusca, Bivalvia) population dynamics and structure within the Miramare Marine protected area (Gulf of Trieste)

Growth and abundance of the Mediterranean bivalve Pinna nobilis have been investigated in four sampling sites of the Miramare MPA (Trieste, Italy) since 2008 by SCUBA divers using the circle-sampling technique. The mean population density values registered in 2008 and in 2009 are quite high, compared to those collected by several authors in other areas. The individual growth rate is faster than growth rates observed in other Mediterranean areas, with an annual shell length increase of 20 cm in the first year of life, 13 cm in the second year and nearly 10 cm in the third one. The estimated age of organisms reveals that in 2009 80% of the individuals were 2-3 years old. Given the high population density, the estimated age and the reproductive capacity of the monitored organisms, the Miramare MPA is likely to be an important site for the conservation and maintenance of Pinna nobilis populations in the Northern Adriatic Sea