A strategy for growing hatchery-reared Pacific oysters ( Crassostrea gigas Thunberg) to market size — Experiments and observations on costed small-scale trials

Abstract

Pacific oysters were grown to market size in a costed experiment. 165 700 spat from three hatchery spawnings were kept in trays during their first year and part of their second year, and then kept on the ground for 2–3 years. Of the 22% which survived after 4 years, 60–75% had reached market size (75 g). The cost of rearing the oysters to this size was about 56% of their final value. Stock grown in trays in the first year at a maximum density of 0.4 g live weight per cm 2 of tray base area (g cm −2) compared to 0.67 g cm −2 showed a small advantage in growth and value which was outweighed by the extra cost of equipment and labour. Overwinter stocking densities of up to about 2 g cm −2 did not affect survival. Survival of stock relaid on the ground was related to size. Small-scale density experiments showed that best growth and yield after 2 years was obtained from oysters relaid at ca. 250 m −2, and that growth stopped at a stocking density of 20 kg m −2.