The shellfish species that are currently produced in our waters include:

• Mussels
• Oysters
• Clams
• Scallops
• Queenies

Recently, there has been interest in abalone culture developing in the south west of England, Wales and Northern Ireland.

The main marine finfish species being farmed at the moment are:

• Cod
• Halibut
• Turbot

The cultivation of haddock and Dover sole are still at the research or semi-commercial level but the prospects are very encouraging. Farmed sea bass is also now appearing in UK supermarkets.

For more information on Aquaculture download The Seafish Guide to Aquaculture.

How shellfish are grown:

Various methods are used for the production of fish and shellfish. Mussels for example, are grown on the seabed and this is the main technique used in England, Wales and Northern Ireland. They can also be grown in suspended culture on ropes hung from longlines or rafts, which is the technique used in the Scottish lochs.

Scallops are grown in suspended culture until they are large enough to be safe from predators when they can be transferred to the seabed. Pacific oysters are usually grown in trays or mesh bags held on trestles on the foreshore, although they can also be grown directly on the seabed. The methods used depend on what is most suitable for the species, the size of the shellfish, the local conditions at the site, and economics.

Native oyster seed, collected from cultch or produced in a hatchery, is relayed in suitable plots on the foreshore where it grows to market size.

How fin fish are farmed:
Juvenile fish are produced in land-based hatcheries and then transferred to sea cages for growing on to market size. This is occurring in Scotland where the infrastructure for producing salmon is well established and some of the producers are diversifying into other, novel species. Norway is another country where this is also occurring. Land-based systems, such as raceways and tanks can be used for species such as turbot and halibut. Re-circulation systems are gaining interest, especially in areas where there are no sheltered sites for the mooring of cages. Although the initial costs of setting up may be higher, the potential advantages of these systems are that the rearing conditions can be carefully controlled.  Whatever the system used, careful appraisal of production costs is essential before setting up any new business.    

What makes a suitable site?
The selection of a suitable site is crucial to the success or failure of any aquaculture business. Growth and survival of the stock, whether fish or shellfish, are influenced by a range of physical and biological factors, including sea water temperature and salinity, exposure of the site, dissolved oxygen and pollutants. Sites near large urban and industrial developments are generally unsuitable for cultivation because of potential pollutants in the water. More specifically for shellfish, growth and survival are also affected by water flow rates, food (phytoplankton) in the water, substrate type, predators, competitors and fouling organisms. Starfish and crabs are abundant in estuaries and coastal waters where they are probably the most significant of all the shellfish predators.

As well as the factors that affect the species being reared, there are a number of other considerations to be taken into account when finding a suitable site. For example, many areas of the coastal zone have been designated for their conservation value so it is also advisable for any potential new business to contact the appropriate conservation agency. There are a number of legal and regulatory points to consider, eg water abstraction and discharge (for fish), water classifications (for shellfish).

Farmed fish on the menu:
Increasingly, farmed fish and shellfish are appearing on retailers’ shelves. The seafood species produced by the aquaculture industry are very healthy, being low in cholesterol and rich in essential nutrients such as polyunsaturated fats (eg in cod liver oil). Shellfish can also be a valuable source of zinc. All can be enjoyed in a variety of recipes prepared at home or when eating out. Taste trials with farmed cod, halibut and turbot have shown them to have a firm and tasty flesh quality. Sea bass and sea bream have proven popular with UK consumers. These species are imported from Mediterranean countries such as Greece and Italy where they are produced in sea cages. Much of the shellfish we produce in the UK goes for export but mussels, oysters, clams and scallops are available from various outlets either fresh or increasingly nowadays in added value products. Contrary to popular belief, shellfish are safe to eat because all products harvested and placed on UK and European markets have to meet strict health and hygiene regulations before they can be sold.

Lobster restocking:
The European lobster is a valuable shellfish species caught all around the UK in baited traps, often called ‘pots’ or ‘creels’, set by small fishing vessels operating in inshore waters. In some areas around the coast, the animals are no longer plentiful and the fishing industry is interested in replenishing stocks by using juvenile lobsters reared in a hatchery and transferred on to the seabed. At first, they construct burrows in the sediment before moving into the rocky habitats favoured by the adults. It can take from four to seven years for them to grow naturally to the minimum size for capture. Once above the legal minimum size, fishermen can capture and sell them. Many of the lobsters caught in the UK are exported to Europe.