Rainbow Trout

Oncorhynchus mykiss

Governance and Outlook


As a pioneering species, many of the technical challenges to face finfish aquaculture (such as feeds, reproduction management, disease control) first emerged with rainbow trout. Rainbow trout farming has also exposed many of the environmental sustainability issues that confront finfish farming. Mitigation methods have developed as the industry and governance have evolved.

Governance systems play an important part in ensuring environmental sustainability, and whilst these have evolved rapidly with the growth of the industry, there are differences between regions and countries. Poor governance can result in industry stagnation, the spread of preventable diseases, environmental damage and opposition to aquaculture activities by local communities and groups such as non-governmental organisations (NGOs). Key governance responsibilities are ensuring environmental assessment and decision-making processes are in place for sensitive and coastal ecosystems, which help deliver sustainable aquaculture whilst managing possible adverse impacts. Other regulatory and governance aspects should cover aspects such as water abstraction and discharge, health monitoring, and so forth.

Four principles – accountability, effectiveness and efficiency of governments, equity, and predictability of the rule of law – are necessary for effective aquaculture governance. These principles should guide the administration, legislative and regulatory framework of aquaculture. In addition to governments, stakeholders such as communities, non-governmental organizations (NGOs) and producers should also be involved industry governance1.

Rainbow trout supplying the UK market is predominantly farmed in the European Union (EU) and in economically advanced countries with highly evolved governance structures in place2. In the EU there are regulations and investment instruments intended to develop environmentally, socially and economically sustainable aquaculture3. In non-EU member states (such as Norway4) there are largely equivalent policies.

In most rainbow trout producing regions, the relevant authorities will have licensing regimes for freshwater production facilities. In the UK for instance, resources where information can be accessed, e.g.:

  • England – Regulatory Toolbox5
  • Scotland – Fish Farm Consents6

Licencing regimes address water abstraction, discharge, treatments, containment and notifiable disease control. Abstraction may be limited by either volume per unit time, or as a percentage of flow to account for seasonal changes. Discharge relates to many parameters and may cover dissolved oxygen levels, pH, suspended solids, nitrogenous and phosphorous wastes, and biological oxygen demand. Treatment licencing will cover the discharge of medicines and chemicals used for bath treatments. Containment will set requirements to prevent the escape of farmed stocks.

Seawater net-pen farms will typically need a site licence which will require an environmental impact assessment and modelling of the potential impact of wastes (faeces and uneaten feed) and chemicals that may be discharged from the farm. Once operational, seawater farms are typically licenced for a maximum biomass, as well as chemical discharges. Certification schemes are playing an increasing role in guiding aquaculture by setting additional voluntary standards that practitioners must adhere to. These are outlined later in the profile.


Due to its suitability for farming, freshwater rainbow trout aquaculture has expanded in areas that are not traditionally associated with salmonid farming, e.g. Iran, Turkey, China. The import of cheaper trout into the EU from Turkey has proved somewhat controversial with tariffs being imposed to balance the subsidies Turkish producers receive11.

Production of rainbow trout from freshwater in the UK has declined over the last 2 decades8, 9, possibly due to decreasing consumer demand for portion-sized fish. In Scotland10 there is a trend for more rainbow trout to be grown-out in seawater to a larger size, using technology similar to that used in Atlantic salmon farming. This provides a diversification for the salmonid marine net-pen industry and increases the variety of rainbow trout products available to the consumer.

Companies operating freshwater rainbow trout farms tend to be smaller than the large multinational, vertically integrated salmon companies, and focus on a particular stage in the production cycle. Good and/or improving farming governance structures will help to ensure the long-term sustainability of trout farming. The diverse range of systems used to farm rainbow trout, and the retrospective fitting of recirculation technology, should enable farms to meet increasingly strict environmental regulation.

Rainbow trout farming in freshwater is a long-standing sector of the aquaculture industry in many countries. Although reported production has decreased since 2012, it is expected to remain stable into the future. Global production is sufficient to justify the development of certification schemes for the species. The sector is large enough for feed companies to produce and market a range of rainbow trout feeds. Specialist broodstock sites supply eggs internationally, and global interest is sufficient to support research in strain development7.


  1. FAO
  2. FAO
  3. EC
  4. Norwegian Directorate of Fisheries
  5. Seafish
  6. Scottish Government
  7. Leeds TD et al. (2010). Response to selection for bacterial cold water disease resistance in rainbow trout. J. Anim. Sci. 88:1936-1946.
  8. CEFAS
  10. Marine Scotland Science 2018.
  11. Fishupdate