Trout, Rainbow

Oncorhynchus mykiss

Method of production — Farmed
Production country — UK
Production method — Open net pen
Picture of Trout, Rainbow

Sustainability rating three info

Sustainability overview

Trout farming was introduced into the UK in the 1950’s, and now there are over 300 trout farms. Rainbow trout is the most popular farmed species of trout, with most of production occurring in a variety of enclosures in freshwater. In Scotland trout can be farmed in open net pens in marine waters. It takes approximately 7-8 months for trout to reach harvesting size. Trout are carnivorous fish whose feed relies on wild fisheries. Rainbow trout farmed in freshwater is a good choice.

Feed Resources

Criterion Score: 0 

Trout is a feed species that relies on commercial pelleted feed. The ingredients used to make the feed are traceable and responsibly, if not sustainably sourced. Feed formulations have changed and continue to do so resulting in less wild fish being included in feeds. These marine proteins and oils are being replaced with vegetable alternatives such as soy and rapeseed oil. The amount varies between countries and feed formulations but the average feed still includes a significant amount of fishmeal and fish oil, MCS would like to see this fisheries supplying the feed being certified as sustainably managed.


Environmental Impacts

“Criterion Score:0

As trout farms in this assessment are located in seawater freshwater depletion is not an issue. There is no mention within the Quality Trout standard of habitat protection prior to net pen construction, therefore there is uncertainty regarding habitat impacts. There is no data regarding chemical use impacts in the wider environment, however the use of chemicals is controlled by the criteria within the Quality trout standards as well as by SEPA. The same applies for discharges, although discharges occur they are both regulated and covered by the production standards. Trout eggs are all sourced from hatcheries and commercial broodstock. Sea lice are an issue for rainbow trout farmed in seawater but there is no data to indicate the extent of the problem or the wider impacts in may have. Although farmed trout can be affected by a number of diseases there is no evidence to suggest that such diseases affect the viable of a production region. Escapes are possible, although mitigation measures are in place as a requirement of the production standards, escape numbers are recorded and made public in Scotland but not so in England and Wales where data is lacking. In 2019 an escape of 33,000 trout occurred in Loch Etive. Predators, such as seals, are common in marine waters and non-lethal control is advocated but lethal control is permissible. “


Fish Health and Welfare

Criterion Score: 1

Quality Trout standards cover both fish welfare and slaughter. A Veterinary Health Plan is required which covers transport and staff are required to be trained in welfare practices.



Criterion Score:4

There are regulations or standards criteria in place for a range of environmental issues, namely: Environmental Impact Assessments; Identification and protection of valuable habitats & species; Use of land and water resources; Use of chemicals including licensing; Discharges including effluents and their impacts; Bio-security & disease management and species introduction, although publicly available data on both the scope, responsibility and metrics relating to these could be improved.


Production method

Open net pen

Farming trout in open net pens allows discharges of organic waste and nutrients directly into the environment. Production is such systems can also lead to escapes.


Based on method of production, fish type, and consumer rating: only fish rated 2 and below are included as an alternative in the list below. Click on a name to show the sustainable options available.

Anchovy, anchovies
Arctic char
Herring or sild
Salmon, Atlantic (Farmed)
Salmon, Chum, Keta, Calico or Dog salmon
Salmon, Pink, Spring , humpback
Salmon, Sockeye , Red Salmon, Bluebacks, Redfish
Trout, Rainbow
Tuna, albacore
Tuna, skipjack
Tuna, yellowfin


A member of the salmonid family, rainbow trout are native to western North America and range from Alaska to Mexico. They can grow up to 120cm in length and live to an average age of 11 years. They prefer freshwater and require fast flowing water to breed


"FAO Cultured Rainbow trout factsheet. Available online at: Accessed 18/06/2019

Quality Trout. UK standard issue. 5.6 1 11 2017. Available online at: Accessed 18/06/2019

Pauly, Daniel and Watson, Reg (2009)?""Spatial Dynamics of Marine Fisheries"" In:?Simon A. Levin (ed.)?The Princeton Guide to Ecology. Pages 501-509

Medicines and Chemicals. SEPA. Available online at: Accessed 25/06/2019

Small scale trout farming. FAO. Available online at: Accessed 18/06/2019

Tacon. A, G, J & Metian, M. 2008. Global overview on the use of fish meal and fish oil in industrially compounded aquafeeds: Trends and future prospects. Aquaculture Volume 285, Issues 1-4, 7 December 2008, Pages 146-158

FAO. Aquaculture Feed and Fertilizer Resources Information System. Available online at: Accessed 18/06/2016

O'Donohoe, P. Kane, F. McDermott, T. Jackson, D. 2016. Sea reared rainbow trout, Oncorhynchus mykiss need fewer sea lice treatments that Atlantic salmon, Salmo salar. Bulletin European Association of Fish Pathology 36(5).201 Scottish Fish Farm Production Survey. Scottish Government.2017. Available online at: Accessed 20/06/2019

UK's Dawnfresh suffers escape of 33,000 trout. Undercurrent News. 01/7/2019, Available online at:

Scotland National Marine Plan. Scottish Government. Available online at: Accessed 25/06/2019 COUNCIL DIRECTIVE 92/43/EEC (1) of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora. Council Directive 2006/66/EC . EUR Lex. Available online at : Accessed 24/06/2019

Council Regulation (EC) No 708/2007 of 11?June 2007 concerning use of alien and locally absent species in aquaculture. EUR Lex. Available online at: Accessed 24/06/2019 "