Stock evaluation of the oyster Crassostrea brasiliana in mangroves of rivers and tidal creeks ("gamboasâ€Â) in Cananéia lagoon estuarine system (São Paulo State, Brazil)

Abstract

The Cananéia lagoon estuarine system, situated in 25^oS latitude at the Atlantic Coast of South America, holds one of the greatest natural stocks of oysters in Brazil. An estimative of Crassostrea brasiliana population in mangroves along the rivers and "gamboas†(or "marigotâ€Â) located in the Cananéia estuary is presented. This survey was conducted from October 1999 to January 2000. The structural characteristics of the mangroves and the estimative of the oyster stock were studied in whole extension of 18 rivers and 10 "gamboasâ€Â. The oysters settle, preferentially, on air roots of red mangrove Rhizophora mangle disposed on the first and second rows along the external fringe of tidewater. R. mangle or a mixture of R. mangle and Laguncularia racemosa occupied the most oyster productive mangroves. The oyster’s banks disappear, gradually, in direction to the riverhead, due to decreasing salinity. It was estimated that rivers and "gamboas†(tidal creeks) of Cananéia mangroves present a population of 5,505,732 dozen of oysters, among which 9.7% have commercial size (> 5 cm in height). It represents a great contribution for the stock of Cananéia estuary that should be carefully considered in a sustainable management of this important resource.