Gametogenic cycle of Crassostrea gigas in contrasting Mediterranean habitats: marine (Gulf of Tunis) and continental (Bizert lagoon) culture sites

BACKGROUND: The gametogenic cycle of Crassostrea gigas, a species imported into the Mediterranean for aquaculture, has been studied (May 2005 to July 2006) in two contrasting habitats of Tunisia: the Bizert lagoon, where oyster farms have been developed since 1970, and the Gulf of Tunis, where oysters have been experimentally farmed during this study, to assess the potential of this latter marine area for sustaining oyster-culture. RESULTS: The sexual cycle of the species was described through the histological examination of the gonads, the estimation of oocytes diameter, and the assessment of its condition and gonadal condition indices. The applied techniques gave similar results. The gametogenic cycle of C. gigas was precocious and more intense in oysters farmed within the lagoon than in the marine area, considering as well gonadal growth, maturation stages and gametes release. CONCLUSIONS: The obtained results are probably related with the different environmental conditions of the studied habitats, temperature and food supply, in particular. The sexual cycle of the species was successfully completed in the marine area, stressing the invasive character of C. gigas.