EVALUATION OF PACIFIC OYSTER CULTIVATION METHODS IN THE SOUTH WEST OF ENGLAND

The cultivation of the Pacific oyster, Crassostrea gigas, has been undertaken in the estuaries of the south west of England since the species was introduced into commercial cultivation in the UK in the 1970s. The industry has grown slowly following improvements to legislation and environmental conditions and it is now in a position to increase production. This study has been undertaken to assess different methods of cultivation used commercially in the south west of England for growing Pacific oysters. The two methods, the growth of oysters contained in bags placed on racks and oysters in bags placed directly onto the foreshore, were assessed at a site on the River Dart at Waddeton. The experiment set up the two methods with a replication of the five bags in two blocks. The trial was then repeated fully and partially a third time. The oysters were purchased as seed and grown within the treatments until they had reached commercial market size. Measurements were taken throughout the growing cycle and were used to assess the two growing methods. Additional environmental data was recorded in order to aid comparisons with other similar studies. Following the study it has emerged that there are no advantages in growth rates obtained from either cultivation method. Both methods produce market size Pacific oysters after 20 months, which is comparable with other study growth rates. The major difference comes from the costs associated with the two methods of cultivation; the cost of the shore based system produces an oyster at a saving of 20% compared to the rack culture. Site selection and substrata condition are the important factors to be considered when deciding which method of cultivation best suits individual operators