I. Abstract

In 2026, thanks to land-based recirculating aquaculture systems (RAS), rainbow trout farming is expanding from mountainous regions rich in cold springs to locations across the globe — whether in the deserts of the Middle East, the tropical cities of South-East Asia, or industrial parks in inland China, rainbow trout can now be farmed year-round. This technology places water temperature, water quality and pathogens entirely under artificial control, making the notion that ‘cold-water fish can only be farmed in cold-water regions’ a thing of the past.

II. Why what was impossible in the past is possible now

2.1. The past: Rainbow trout farming was constrained by ‘cold-water resources’

Rainbow trout are a typical cold-water fish species, thriving at water temperatures of 12-18 °C and requiring dissolved oxygen levels above 7 mg/L; they cease feeding when the water temperature exceeds 20 °C and suffer mass mortality at temperatures above 25 °C. Traditional flow-through pond farming must be situated near mountains and springs; consequently, the world’s main production areas are concentrated in Norway, Chile, North America, and the cold-water-rich regions of south-western and north-western China.

This has led to three long-standing challenges: firstly, geographical constraints, meaning that countries and regions lacking cold-water resources are forced to rely on imports; secondly, seasonal constraints, as farmers dare not stock fry or rear large-sized fish during the high-temperature summer months; and thirdly, scale constraints, as the number of high-quality cold spring sites is limited, making it extremely difficult to expand production capacity.

2.2. Present: Three technological breakthroughs enable rainbow trout to be farmed ‘anywhere’

2.2.1. Temperature control breakthrough – unrestricted by climate zones

Recirculating aquaculture systems (RAS), equipped with chillers, heat pumps or waste heat recovery, maintain water temperatures within the optimal growth range of 12-16°C year-round. In tropical regions, where outdoor temperatures reach 40°C in summer, the facility remains at a constant temperature; in cold regions, where temperatures drop below zero in winter, growth continues uninterrupted. Aquaculture is no longer constrained by latitude, altitude or season.

2.2.2. Water Recirculation Breakthrough — Unrestricted by Water Sources

RAS systems achieve a water recirculation rate of over 95%, transforming the reliance on cold spring water from ‘large-scale, continuous extraction’ to ‘minimal top-ups’. Underground cold water, desalinated seawater and treated municipal wastewater can all be utilised following appropriate regulation, meaning that even water-scarce arid regions and industrial estates far from rivers are suitable for farm construction.

2.2.3. Breakthrough in biosecurity — Unrestricted by the external environment

Multi-stage filtration combined with UV and ozone disinfection achieves a pathogen removal rate of over 99.9%, effectively isolating parasites and viruses (such as Ichthyophthirius multifiliis and the IHN virus) introduced via external water sources. Regardless of the conditions in the surrounding waters, aquaculture conditions within the enclosed facility remain consistently controllable.

III. Practical implementation around the world

Recirculating aquaculture systems for rainbow trout have been successfully demonstrated in various climatic regions around the world:

Arid regions of the Middle East and North Africa: utilising low-cost energy in conjunction with seawater desalination and temperature-control systems to establish cold-water fish farming facilities deep within the desert;

Tropical countries in South-East Asia: relying on chillers to regulate temperature in high-temperature, high-humidity environments, with produce supplied to local high-end restaurants and supermarkets, replacing imports;

Inland regions of China: From Nanchang in Jiangxi and the coastal areas of Jiangsu to the Inner Mongolia Plateau, several 10,000-metric-tonne land-based cold-water fish farms have been established and are now in operation, with ‘domestic salmon’ supplied directly to local markets;

High-altitude and high-latitude regions: By utilising natural cold-water resources in conjunction with recirculating aquaculture systems, energy consumption is lower and costs are more favourable.

The common factor is that, provided there is a stable electricity supply and basic site conditions, rainbow trout farming can be established without the need to ‘wait’ for a cold spring.

IV. Key considerations for implementing recirculating aquaculture systems for rainbow trout in different regions

Table 1: Details of Rainbow Trout Farming Projects in Different Regions

V. Why is now the right time to expand rainbow trout farming globally?

1. Demand side: Global salmon consumption continues to grow, with strong demand for chilled, sashimi-grade fillets and caviar; rainbow trout (particularly triploid rainbow trout) is an ideal substitute and complementary species;

2. Supply side: Traditional net-cage and flow-through aquaculture are facing increasingly stringent constraints due to environmental, disease and climatic factors, making land-based, controlled aquaculture the primary direction for new production capacity;

3. Costs: The costs of refrigeration, pure oxygen and automated equipment continue to fall, whilst the combination of ‘cold spring water/waste heat + RAS + photovoltaic energy storage’ makes operating costs more manageable;

4. Policy: Many countries have included land-based recirculating aquaculture systems within the scope of support for agricultural modernisation and food security, with a favourable environment for project approvals and subsidies.

VI. Frequently Asked Questions (FAQ)

Q1: Is it really possible to farm rainbow trout in tropical countries?

A: Yes. Rainbow trout require a specific ‘water temperature’ rather than a specific ‘ambient temperature’. Recirculating aquaculture systems (RAS) use chillers to maintain a stable water temperature of 12-16 °C. There have already been numerous successful examples of commercial farming in tropical regions, with the produce supplying local high-end markets and replacing imports.

Q2: Is it possible to farm rainbow trout without access to cold spring water?

A: Yes. RAS systems achieve a water recirculation rate of over 95%, requiring only a small amount of make-up water. Groundwater, desalinated seawater and even treated reclaimed water can be utilised, meaning site selection is no longer dependent on mountain springs or rivers.

Q3: What are the site and electricity requirements for rainbow trout recirculating aquaculture systems?

A: The key requirements are a stable electricity supply (for cooling, aeration and circulation pumps) and sufficient land for facility construction. Modular RAS designs allow for phased construction based on production capacity, with projects scalable from several hundred tonnes to ten thousand tonnes.

Q4: Will the costs be high for rearing rainbow trout in non-traditional production areas?

A: Cooling is the primary energy consumption item in tropical regions, but unit costs can be reduced through the utilisation of waste heat, photovoltaic energy storage and high-density, high-yield farming. Compared to importing rainbow trout by air, local aquaculture offers clear advantages in terms of freshness, customs duties and supply chain stability.

Q5: How can one assess whether a particular region is suitable for a rainbow trout RAS project?

A: Four key factors are assessed: climate and energy costs, water source conditions, target market capacity, and the availability of fry and technical support teams. Wolize can provide site selection assessments, process design and return on investment calculations.

VII. Contact us and join Wolize in bringing rainbow trout farming to any location

From tropical deserts to high-altitude plateaus, Wolize’s one-stop RAS equipment and engineering services have helped clients across diverse climatic zones to establish localised rainbow trout farming operations — providing end-to-end support covering process design, equipment selection, installation and commissioning, and post-sales training. Please feel free to contact our team for a free site assessment and production capacity planning proposal.

Figure 1: Recirculating aquaculture system for rainbow trout (Oncorhynchus mykiss)