Stocking density effect on the growth and mortality of juvenile European flat oyster (Ostrea edulis Linnaeus, 1758)

The effect of stocking density on the growth and mortality of the European flat oyster (Ostrea edulis Linnaeus, 1758) reared in lantern nets was evaluated, starting from spat up to the end of juvenile phase. Oysters were deployed in a raft on the Basque coast (SE Bay of Biscay) for 18 months. Oysters were divided into four densities ranging from 25% to 100% of surface coverage. At the end of the experiment, oysters from an initial mean height and wet weight of 22.79 ± 3.70 mm and 1.00 ± 0.30 g reached mean values of 55.86 ± 8.21 mm and 19.08 ± 9.66 g, respectively. Although significant differences were detected in the growth of oysters reared at different stocking densities, these differences were not density dependent. On the other hand, mortality increased with time showing relatively high values (27%–38%), but especially at the end of the study when oysters at the highest density showed values up to 50%. In conclusion, stocking density had no effect on the growth, but had a negative effect on the survival at the highest density. A stocking density of 75% is recommended as the optimum for rearing O. edulis in the Basque coast. ‐Determination of the stocking density effect on the growth and mortality of Ostrea edulis reared in a suspended system for 18 months in the Basque coast. ‐Stocking density had no effect on the growth but had a negative effect on the survival of flat oysters at the highest density. ‐A stocking density of 75% of surface coverage was recommended as the optimum treatment.