Wind influence in the oyster larvae transport within a complex bay: Anegada Bay, Argentina

ALVAREZ L.I., ALBERDI E., CUADRADO D.G. Y PERILLO G.M.E.

Foz do Iguassu

Congreso; The meeting of the Americas; 2010

Crassostrea gigas is an invasive species within the Argentina coast. In particular within Anegada Bay (between 39º50’ and 40º40’ S). However, many of their banks are being exploited for commercial activities and, recently, aquaculture developments have been started. A major problem is the potential migration of the larvae outside Anegada Bay towards the San Matías Gulf where the local oyster is being conserved. C. gigas outcompites the local oyster resulting in the potential elimination of the original one. The present study provides the results of a numerical langrangean model of the circulation of the bay including the displacement of the larvae and affected by the typical wind pattern of the region. Anegada Bay is a complex system of tidal channels, extensive coastal wetlands and islands. The system is mesotidal with ranges between 2 and 3.5 m. Although the dominant wind pattern is from the NW and SW most of the year, during the larvae hatch (summer period) the predominant wind is from the NNE and NE with mean speeds of the order of 34 km h-1. Mean water temperature is 20ºC, and typical current velocities in the San Blas Channel may reach up to 3 m s-1. The employed model is the 3D hydrodynamic module of the MOHID plus its langrangean biological module with a resolution of 100 m and 15 levels employing a sigma configuration. The model was run for the period of 90 days during the warm months of the southern summer using as external tidal forcing the Fes 2004 model. Model validation and calibration was made against tidal and wind data from two EMAC stations operated by IADO on site plus ADCP data obtained along a tidal cycle on a cross section of the San Blas Channel. The results of the model show that larvae are retained within the bay and in many cases they are forced along the inner tidal channels of the bay. It is clear that if the wind pattern is maintained, the larveae do not represent a danger to the local oysters within the San Matias Gulf.