Physical and chemical parameters of several oyster growing areas in Tasmania

Abstract

Physical and chemical parameters at five Pacific oyster (Crassostrea gigas) growing areas in Tasmania - Pittwater, Pipeclay Lagoon, Little Swanport, Georges Bay and Simpsons Bay - were measured as part of a study to determine the carrying capacity of the areas for oyster farming. This has provided valuable environmental data for these areas. The hydrodynamic regimes at each area except Simpsons Bay were studied, including high and low water volumes, flushing rates, flow rates and depth contours. Temperature, salinity and concentrations of nitrates, phosphates, silicates and chlorophyll a were measured monthly at several sites in each area. The change in these parameters over different time scales also was examined at two sites in Pittwater and indicated temporal and spatial variability in the environmental parameters measured. Intensive sampling for nutrients and chlorophyll a around the oyster farms in each area did not show any clear trends in concentrations. A comparison of the environmental conditions and the production of oysters from each growing area shows that Pipeclay Lagoon is by far the most productive, and that it has comparatively shallow water and rapid flushing rate. This suggests that a rapid turnover of oceanic water is important for supplying food to the oysters. Chlorophyll a and nutrient concentrations, however, were similar at all growing areas.