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Growth and survival of the oyster of mangrove low Crassostrea rhizophorae condition of culture intermareal and submareal in the big lagoon of the bishop, Cariaco's Gulf, venezuela

Abstract:

To evaluate the growth and the survival rates of the oyster Crassostrea rhizophorae in a regime of sub-tidal and inter-tidal culture at Laguna Grande del Obispo, Gulf of Cariaco, Edo. Sucre, Venezuela, seeds of 32-35 mm in back-ventral length of the shell, were placed in baskets maintained in fixed parks. The oysters growth in length and dry biomass as well as mass of the shell and the survival rates in two culture systems were compared in two periods: the first (I), from October 2005 to January 2006, and the second (II) from February to September of 2006. Environmental parameters of temperature, salinity, a chlorophyll, seston, biofouling and rainfall were taken, based on relating them to the variability of the growth and the survival rates. During the first months, for both periods, a high and progressive mortality in the system of subtidal culture was experienced, related to the presence of the Cymatium poulsenii gastropod. On the contrary, oysters in intertidal conditions had a survival rate superior to 95% in both periods. The growth in length and biomass did not show significant differences, in the first months, between systems; in period I the organisms, both in subtidal and intertidal conditions, reached sizes of 43,3±3,43 and 48,2 ± 4,01 at the end of the test (3 months). In period II oysters of the intertidal system, reached 75,13 ± 5,16 mm (an increase the some 108%), during seven (7) months of culture. The results show a greater feasibility of the intertidal culture, the main reason being its avoidance of the incidence of predators, particularly Cymatium poulsenii.