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Report 1 of 5:
The
Food Of Love - England
Introduction
There are two species of oyster marketed in the United Kingdom and throughout Europe - the native flat oyster, Ostrea edulis, and the Pacific oyster, Crassostrea gigas. The Pacific oyster was introduced in the 1970s and is cultivated - being bred in hatcheries and then grown on in the sea - usually in plastic mesh bags. Native oysters are almost all dredged from wild stocks, though these may be re-laid to grow and "fatten" on inshore beds. The process of fattening helps the oysters to become plump and succulent, although they actually contain almost no fat, as the reserves they build up are mainly glycogen, which is carbohydrate.
Native oysters spawn in the summer, and so are not marketed in the United Kingdom from May to the end of August. Pacific oysters rarely spawn at the temperatures in the United Kingdom and so can be sold all the year round.
Seed Oysters
Seed oysters can be purchased from commercial hatcheries and nurseries in the United Kingdom but cannot be imported, thus preventing the introduction of diseases. New growers should concentrate on the Pacific oyster, which tolerates a wider range of conditions and is less susceptible to disease than the native species.
Seed oysters of various sizes can be purchased. Most growers recommend starting with 10-12mm size seed oysters which have been reared in nurseries and weigh about 0.2 to 0.5 grams each. This means there are between 2,000 and 5,000 seed oysters per kilogram. New growers often start with half-grown oysters from other producers, buying them at a weight of 10-12 grams. Market size is from between 70 and 100 grams or 10,000 to14,000 oysters per tonne.
Farming techniques
Techniques for on-growing Pacific oysters are well established. Most oyster growers use plastic mesh bags, called 'poches', fastened onto steel or timber trestles with rubber bands. A few growers, who have firm gravel grounds, relay their larger oysters loose onto the bed.
Oysters are best farmed in sheltered waters where there is some mixing with fresh water. The Pacific oyster can withstand lower saline levels than the native oyster, but areas where there might be prolonged periods with salinity below 60% normal sea water should be avoided.
Movements of oysters from one area to another are closely controlled by licenses to prevent the spread of shellfish pests and diseases. The appropriate Fisheries Department in your part of the United Kingdom should be consulted about these regulations.
Pre-market storage
Oysters from some beds need to be held in purification or 'depuration' tanks before being marketed. Local Environmental Health Officers will advise if this is necessary. The design and operation of such tanks has to be approved by the Department of Health, in conjunction with the CEFAS Fisheries Laboratory, Weymouth, who will advise on system design. The Sea Fish Industry Authority at Hull has also prepared designs for purification systems to meet a range of requirements.
Oysters are grown close to the low water mark of Spring tides. At this level they only uncover to be worked on during alternate weeks. Growers hold supplies ready for market either in purification tanks or on trestles higher up the beach.
Once they have left the grower, oysters should never be stored in water unless it is in a specially designed system. They will stay alive and fresh for one week if stored correctly - deep shell down, in a cool place or refrigerator, covered with a damp towel.
Seasalter Shellfish (Whitstable) Ltd.
Native oysters have been fished commercially off Whitstable in Kent since Roman times. Whitstable Bay is part of the Swale estuary, a shallow area with good tidal interaction between land and sea giving ideal conditions for good algal production and shellfish growth.
Seasalter Shellfish (Whitstable) Ltd. owns two square miles of seabed off Whitstable known as the Pollard Ground where oysters and clams are grown. They also have a Crown fishery of similar size off the Isle of Sheppy. The 100 year old buildings at Whitstable Harbour house the main office, packing and depuration plant. During the last century, oysters stocks and markets declined throughout the United Kingdom due to disease, bad winters, pollution from a nearby paper mill and over fishing. After World War II, the industry as a whole became practically non existent.
During the early sixties, the Ministry of Agriculture and Fisheries began research on artificial breeding techniques for oysters using the Pacific oyster. A team of biologists, led by John Bayes, was employed to set up a hatchery at Whitstable and begin a re-stocking programme for both species. The Seasalter Shellfish Company has developed a method for the continuous production of algae, a water dwelling plant, which is the food of fish and shellfish alike. The key to successful algal production lies in continuous supply.
After nine months of being nourished by the algae, the oysters are grown to maturity out in the open sea. The Pollards Oyster bed is the largest single owned oyster bed in Europe and contains around 8 million oysters. Each one has to be brought ashore twice a year for sorting, cleaning and thinning until after three years they are ready for market.
Today, the company operates two hatchery and nursery systems, one at Reculver, eight miles East of Whitstable, and the other on Walney Island in Cumbria in the North West of England. This is a good defence against natural or man made disasters. Production now covers oyster and clam seed and other species of bivalve mollusc to order.
A completely different aspect of the business is concerned with the sale of technological advances. Continuous harvest microalgal systems and customised hatchery designs have been installed at both fish and shellfish farms in 14 countries. The training programmes, consultancy and after-sales back up service is unique because it is supported by an exclusive hands-on operation. The Company sees a good future in assisting others in the industry to achieve full and economic production potential by drawing upon their experience.
Benefits from eating fresh oysters
- Oysters are low in calories and saturated fats and good for our diet.
- Oysters are high in beneficial polyunsaturated fats. These assist the circulation and the nervous system. Omega 3 can lower cholesterol levels and Taurine can lower blood pressure.
- Oysters are rich in vitamins and trace minerals.
- Oysters contain no additives.
For further information, please contact:
Seasalter Shellfish(Whitstable)Ltd.
The Harbour
Whitstable
Kent
CT5 1AB
United Kingdom
Tel: +44 (0) 1227 262003/272003
Fax: +44 (0) 1227 264829
E-mail: seasalter@compuserve.com
Website: http://www.seasaltershellfish.co.uk/ |
Shellfish Association of Great Britain
Fishmongers' Hall
London Bridge
London
EC4R 9EL
United Kingdom
Tel: +44 (0)20 7283 8305
Fax: +44 (0)20 7929 1389
E-mail: sagb@shellfish.org.uk
Website: http://www.shellfish.org.uk/ |
Guernsey Sea Farms Ltd.
Parc Lane
Vale
Guernsey
Channel Islands
Tel: +44 (0) 1481 47480 |
Much useful advice on oyster growing is contained in the booklet 'Cultivation of Pacific Oysters' by B.E.Spencer, available from CEFAS at Lowestoft.
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Intermediate Technology Development Group would like to thank Seasalter Shellfish (Whitstable) Limited and the Shellfish Association of Great Britain for providing the original material on oyster production.
This document is an output from a project funded by the UK Department for International Development (DFID) for the benefit of developing countries. The views expressed are not necessarily those of the DFID.
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