Shellfish aquaculture has been practiced for over a century in Lough Foyle and Carlingford Lough, however it is only in the last 20-30 years that aquaculture has really begun to grow markedly as an industry in these sea loughs.
Aquaculture of species such as blue mussels, native oysters, pacific oysters and manila clams has been trialled in both loughs however nowadays generally most fish farmers grow either pacific oysters or blue mussels. These two species are grown in different ways and in different areas so there is no direct competition between the two.
Mussels and oysters are bivalve shellfish. This type of shellfish filters seawater across its gills to capture food items such as plankton. Plankton is made up of small plants and animals that are present in seawater. This means that large amounts of shellfish can filter enormous amounts of water every hour and every day. This can have a good effect on the water quality of the sea loughs in which the shellfish are living. Too much plankton can have a negative affect on the oxygen levels in the sea loughs and this can lead to the deaths of fish, shellfish and bird life that depend on good water quality to live. When shellfish filter this plankton out of the water it can help to decrease the chances of the plankton being present in large amounts, which might have dangerous consequences.
Fish farmers need to find a suitable area on the seabed or on the seashore to grow their shellfish. Once they have found a location they must ensure that their shellfish farm will not have any negative impacts on the environment in that location. The fish farmer usually has to get a scientific report written to show that the shellfish farming he is intending to do will not have any harmful side effects on the environment. Once this report has been written and given to the licensing authority a decision is made about whether or not a license should be given to the fish farmer. This process can take years to complete and objections from members of the public can occur, which delays the decision making process. This system allows only environmentally sustainable fish farms to be licensed by the authorities.
Once the farmer has got his fish farm location he has to either buy young mussels or oysters or go and catch them himself. Usually the young oysters are bought from hatcheries in England and transported to the farms for growing to market size. The young mussels on the other hand are captured using dredges on the seabed and these are relaid onto the fish farm. Once they have eaten enough plankton and grown to the right size the fish farmer collects them and sells them to a processor who in turn sends them to shops and restaurants.