Distribution, abundance and biological parameters of Cerastoderma glaucum (Mollusca: Bivalvia) along the Gabes coasts (Tunisia, Central Mediterranean)

Abstract

         The cockle Cerastoderma glaucum (poiret, 1789) represents one of the most common marine mollusc species present in soft bottom infralittoral assemblages in Tunisian waters. The status of the species is still poorly known and there is a knowledge gap about its distribution, abundance and biological parameters. The significant ecological role of C. glaucum in the ecosystem and its possible future commercial interest requires a better knowledge of its stock. This study aimed to investigate the distribution, abundance and biology of these cockles along the Gabes coast. Cockles were collected, treated and data were analysed. In terms of geographical occupation, maps of the population distribution were drawn. The results showed a scattered distribution pattern of the species according to location ranging between 0 and 270 individuals per square meter. The consequence was a remarkable biomass which represented 1290±326 tons of total fresh weight and high abundance levels reaching over 403±104 million individuals estimated in the area of 3723 hectares. The distribution of the species has also been investigated in consideration with the size which varied markedly according to location, while the shell length ranged between 5 and 37 mm. Samples presented a balanced sex ratio, with males dominating among smaller individuals and females predominating in larger size-classes contrary to previous findings on this species. The size at which 50% of the population reached maturity was 14.29 and 16.59 mm SL for males and females, respectively. Findings of the current study suggest that C. glaucum well proliferates in southern Tunisian waters.