Comparative economic analysis of full culture and fattening systens of mangrove oysters Crassostrea spp. at Cananéia estuary, São Paulo State, Brazil

Abstract

The aim of this study was to compare two systems of production of the mangrove oyster Crassostrea spp. in the region of Cananéia-SP, the full culture and the "fattening†culture, expression used for the finishing phase of the culture cycle, on the technological and economic point of view, to show which system is most profitable. In the full culture, it was used the initial density of 42 dozen oyster m^-2, and the survival rate at end of 22 months ranged from 25% to 50%. In the fattening culture were used oysters with average height of 50 mm at the initial density of 25 dozen m^-2, which were grown for six months. The lowest survival rate observed in the "fattening†culture was 64%, and the highest, 80%. The full culture has not demonstrated economic viability because its production cost is much higher than the selling prices charged in the local market. In the "fattening†culture it was found that the Internal Rate of Return (IRR) ranged from 20.65% to 102.11% from the sale prices of R$ 3.50 and R$ 4.50, in the two survival rates studied. The highest Net Present Value (NPV) obtained was R$ 355,286.74 for the sale price of R$ 4.50, with a rate of 10.75%, and the smaller was R$ 1,547.50 for the sale price of R$ 3.50 with a rate of 20%, at the lowest survival rate (64%). The results obtained confirm what has been observed in the region, that is, the economic viability of the fattening culture. This fact can explain the expansion of the oyster "fattening†among the Cananéia producers.