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Identification of environmental factors affecting growth and survival of the tropical oyster Crassostrea rhizophorae in suspended culture in the golfo de Cariaco, Venezuela

Abstract:

It was evaluated the growth and survival of Crassostrea rhizophorae juveniles (30 mm) in suspended culture in relation with environmental factors in Golfo de Cariaco, Venezuela, during six months (june-november 2002), in the period of discontinued upwelling and water stratification. Juveniles were maintained in enclosures with 100 individuals suspended to long line at 2-3 m from the surface. The oysters were analyzed monthly determining shell dimensions and dry mass of shell, and soft body, and fouling organisms on shells. Temperature was continually recorded with electronic thermographs and food availability (total and organic seston and phytoplanktonic biomass), oxygen concentration and salinity were determinated weekly. The 15-mm increase in shell height and the 70% of survival suggest a low culture feasibility of C. rhizophorae in Golfo de Cariaco (Turpialito locality). Slow growth rates were related to low food availability, mainly phytoplanktonic biomass. Fouling in enclosures and on shells, in addition to predation, principally by Cymatium spp. gastropods, were negative factors for culture. Reproduction could be an endogenous factor that affects somatic growth. Studies of growth and survival in continuing upwelling period (january-june), where food availability is high, as well as studies of fouling and predation influences are necessary to establish strategies for the C. rhizophorae culture in the Golfo de Cariaco.