Grossissement des juveniles de palourdes Ruditapes decussatus (L., 1758), sur l'estran de Zarat (golfe de Gabes, Tunisie), dans des conditions experimentales

Abstract

The growth potential of clam Ruditapes decussatus (L. 1758), grown in 1 m2 mesh bags on the Zarat Estuary (Gulf of Gabès) was assessed from July 2006 to November 2007 In the first experience, three intertidal levels were compared during 16 months. Each level was represented by a triplicate of bags containing 150 individuals. In a second experience, three different densities were compared during 17 months. Hence, two bags of 100 individuals each and two other ones of 200 individuals each were aligned to the first experience on the level in the adjacent line of high tide. From an initial calibrated clam population characterized by a 28,4 ± 0,1 mm shell length and 4,71 ± 0,01g total wet weight, the best growth in length of 36,85 ± 0,5 mm and wet weight of 10,57 ± 0,5 g were recorded for the densities of 100 and 200 individuals / m2, respectively. However, no significant (P> 0.05) effect of the different intertidal levels as well as of different tested densities on growth was detected at the end of the experiments. A significant growth occurred during the first year in all areas during which highest growth rates were observed in spring (April - May). At the end of this phase, clams reached the authorized exploited size (35mm). After this period, a phase of stopping growth was observed until the end of the experiments. The results of this study showed the possibility of the clam Ruditapes decussatus culture in the Zarat estuary. Otherwise, areas not focalized by fishing offer an important potential for culture. Samples reared at different densities suggested that R. decussatus could be cultivated at 200 individual / m2. Thus the quantity recovered from the sort of fishing and whose size is lower than the authorized exploitation could be improved.