Guernsey Sea Farms

The oysters are started off inside the main building where brood-stock are reared on heated water and fed cultured micro algae. Once mature, oysters are induced to spawn under controlled conditions. A single oyster can produce 20 to 30 million eggs, but, as the progeny grow, this number is gradually whittled away by frequent screening so that only the fastest and most robust oyster seed comes through.

Oysters begin their life as microscopic free-swimming larvae where they are carefully nurtured in heated seawater and fed specially grown algae. After two weeks they change to become sedentary spat and are transferred from larvae tanks to up-welling tubes where high flows of water and food is passed through them. These tubes may look small but can each hold up to 7 million young spat. As they grow they change from looking like fine silt to dark grey gravel and need to be examined under the microscope every day.

Producing sufficient quantities of prime quality algae of the right species is a vital but laborious process. Algae starts off in test tubes and is then grown in larger and larger volumes from bubbling flasks to polythene tubes and finally to large tanks outside.

After 4 to 8 weeks in the hatchery seed is placed in up welling units outside, and although it is no longer on heated water, it is still fed cultured algae. Once it reaches 3 or 4mm in size seed is placed in meshed boxes and transferred to the main pontoon. A highly efficient paddle wheel system, using 10 times less power than conventional pumps, is used to move water through the oyster seed at a rate of 30 tons a minute.

With 45 years of experience working with oysters between them, Mark and Penny Dravers are always happy to advise oyster and clam farmers.