Fish farm siting in Scotland
Atlantic salmon culture began in the 19th century in the UK in freshwater as a means of stocking waters with juvenile (“parr”) stages to enhance wild populations for anglers. Open sea pens or cages were first used in the 1960s in Norway to raise fish to marketable size, and the success led to development of salmon farming in Scotland, and subsequently Ireland, the Faroes Islands, Canada, the North Eastern seaboard of the USA, Chile and Australia (Tasmania), with some minor production in New Zealand, France and Spain.
In Scotland fish farms are based on the west and north-west coasts, due to a presumption in Scottish Planning Policy against marine finfish farm developments on the north and east coasts to safeguard migratory fish species.
Scottish strains of salmon tend to mature early, reducing the value of the fish as they reach market size, so Norwegian strains were introduced to reduce the problem. Generations of cross breeding have produced hybrid strains which are now used in most production areas. Scotland hatcheries now import fertilised eggs to produce larval and juvenile fish. Once hatched, these are grown on in tanks either using freshwater flow-through or land-based recirculating systems (RAS), or subsequently in lake cage systems. At the final juvenile (“smolt”) stage they are transferred to on-growing systems, usually coastal open net pen farms, to reach harvest size.