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Distribution, habitat and population densities of the invasive species Pinctada radiata (Molluca: Bivalvia) along the Northern and Eastern coasts of Tunisia

2009; Roscoff Biological Station; Volume: 50; Issue: 2 Linguagem: Inglês

2262-3094

Sabiha Tlig‐Zouari, Lotfi Rabaoui, Ikram Irathni, Oum Kalthoum Ben Hassine,

Parasite Biology and Host Interactions

The pearl oyster Pinctada radiata (Leach, 1814) is an alien species introduced to the Mediterranean Sea and recorded in Tunisia many years ago. However, since its record in Tunisian inshore areas, no studies have been carried out about the spread of this invasive mollusc. Thus, the status of this species is still poorly known and there is a knowledge- gap about its distribution and ecology. The present work is a contribution to the knowledge of the pearl oyster distribution and density of individuals along the northern and eastern Tunisian coasts, at depths situated between 0 and 6 metres. A large part of Tunisian coast was surveyed, stressing some observations concerning the species ecology and its preferred biotopes. The size structure of the five densest populations was also described. Pinctada radiata has not yet reached the northern coasts (Tabarka and Bizerta coasts). Density of individuals varied from one locality to another between 0 and 62.67 ± 6.11 individuals m-2. This mollusc prefers to be attached to vertical solid substrata (natural or artificial) within marine habitats with relatively high hydrodynamic conditions. Confined localities such as those inside lagoons seem not to be the preferred habitat for the proliferation of this immigrant species. Size structure analysis showed that the majority of the five examined populations, except for Tunis north lagoon and La Marsa, were dominated by large individuals exceeding 42 mm in shell height. It is worth noting that the maximum size (100.5 mm) recorded in the lagoon of Bizerta (Njila) is higher than that recorded in previous studies, in particular in its origin habitat (Red Sea). This suggests that Pinctada radiatais well adapt-