Flat oyster (Ostrea angasi) growth and survival rates at Georges Bay, Tasmania (Australia)

An in situ study of growth and survival rates of flat (native) oysters (Ostrea angasi) was conducted on beds of oysters in Georges Bay, Northeast Tasmania, from February 1994–February 1995. Shell length and whole weight of three size groups of tagged flat oysters were measured at 1–3 month intervals at three sites. Mean increase in shell length ranged from 7 to 28 mm and live weight from 40.3 to 47.0 g for large to small oysters, respectively. Significant differences were shown in the increase in shell length and live weight between sites and size classes. Instantaneous mortality rates were variable between sites and sizes with percentage mortality ranging from 6.43% to 22.95%. The data were also analysed using Fabens parameterisation of the von Bertalanffy growth equation for tag recapture data. Growth curves generated were significantly different with calculated L∞ and k values ranging from 103.5 to 118.8 mm and 0.560 to 0.661 year−1, respectively. Length–weight equations were also calculated for each site. Most shell growth occurred during the warmer months from late spring to autumn. Growth rates found in this study were slightly greater at two sites than those obtained from studies on flat oysters in Victoria