Trout farming was introduced to the UK in the 1950s by a DanIsh entrepreneur. Since then the industry has grown to its current size of almost 290 trout farms.
Rainbow trout (onchorynchus mykiss), although native to North West America has been introduced to regions throughout the world. It is the most popular trout to farm in the UK, as it copes best with the climate and farming system. Other farmed varieties include Brown Trout (salmo trutta) which is indigenous to Britain and other European Countries, also Golden Trout (ancorhynchis mykiss aguabonita) and Blue Trout, albeit in smaller quantities.
Around 17,000 tonnes of Rainbow trout are produced in Britain each year, with around 75% of this farmed by table producers. The majority being farmed in freshwater tanks, ponds, raceways, pens and marine pens.
Fish farms usually concentrate on different aspects of the life cycle. Hatcheries produce ova from brood stock and fingerlings. The fingerlings are then sold on to producers for growing into restocking or table trout. Table producers in turn provide fish to Processors, while Re-stockers will supply Fisheries. Some farms may undertake several of these business activities and in addition may have a shop, a smokery / processing unit, or a Fishery (where anglers can fish in artificially stocked lakes) that is often open to the public.
Trout is farmed widely in the UK, but particularly in central and southern Scotland, south England and North Yorkshire. The main facility required is a clean river for adequate water supply, in an accessible location. Trout are cold blooded and are greatly affected by water temperature. The warmer the water, the fewer the fish that can be stocked and the greater the water flow needs to be; this is because the solubility of oxygen in water decreases with temperature. Ideally, oxygen level. should be 8mg/l or greater. The flow of the water source will in part determine the stocking level. While oxygenation can be used to increase oxygen levels, a sufficient water flow is still required for the health and wellbeing of the trout. The total volume of water available on any one site will be the determining factor in the expansion of a trout farming business.
A farm on a river will consist of ponds, tanks or raceways with the water supplied by gravity. Often a location with a weir is utilised. Pen farming is an altemative method involving the siting of pens in the marine environment or freshwater. The Scottish lochs provide the best location for this method of trout farming.
Screens are installed at the inlet channel, to keep out debris and migratory fish. Water is treated before being discharged back into the river and further screens installed at the outlet. All discharge is strictly monitored and regularly tested by the appropriate Environment Agency.
Trout can be grown to different sizes. Fresh water, flow through sites typically grow trout to a harvesting size from 400g-3k; 400g taking approximately eight months and 3k approximately two years. The trout build muscle by swimming against the current of the water as it passes through the farm.
Once harvested, the trout will be processed for use. Some larger farms have processing facilities nearby, which contain machinery designed to gut, fillet, smoke and pack the fish, depending on what is required. The trout may then be sold direct to customers at farm shops, or sent to wholesale markets, caterers or retailers.
Prior to the 20th century most trout eaten in Europe were caught direct from the wild and the few large-scale trout hatcheries that existed were used to re-stock rivers for fishing. Until the end of the Second World War the UK’s trout industry consisted of less than 20 such re-stocking farms.Find out more