Density and population structure of Pinna nobilis (Mollusca, Bivalvia) in the Ghar El Melh lagoon (N-E Tunisia).

Abstract

This paper focuses on the study of Pinna nobilis population density and structure on Ghar El Melh lagoon. Fieldwork was conducted in 2007 in 4 stations distributed from the sea toward the lagoon. Population of P. nobilis inhabits Cymodocea nodosa meadows mixed with Ruppia and Nanozostera. A gradient in the population density, decreasing from the sea (9.63 ind.100m-²) to the internal lagoon (0.07 ind.100m-²), has been noted. Maximal age is estimated to be 9.7 years, and seems to be related to the improvement of water quality in the area under marine influence after the opening of a communication channel between sea and lagoon in 1996