Recirculating Aquaculture System (RAS) — definition
Land-based fish farming system that filters and reuses the majority of its water through mechanical, biological and often disinfection stages, minimising freshwater intake compared with flow-through systems.
Recirculating aquaculture systems combine solids removal, biofiltration for ammonia conversion, degassing and oxygenation stages to maintain water quality for high-density fish stocking. They allow farming in locations without direct access to large water bodies but require significant capital investment in pumps, filtration and backup power and aeration systems.
Why it matters to industrial buyers
RAS enables aquaculture production independent of coastal or river-adjacent sites, though its higher capital and energy cost relative to flow-through or pond systems must be justified in the feasibility study.
Key reference points
Typical water reuse
Well-designed systems commonly reuse over 90 percent of system water, though figures vary by species and design.
Critical risk
Power or aeration failure can cause rapid water quality decline, requiring backup power and alarm systems.
Commonly confused with
Flow-through aquaculture
Flow-through systems use water once before discharge; RAS treats and reuses water continuously, reducing water demand but increasing system complexity.
How it is used in practice
The feasibility study compared capital and operating costs of a recirculating aquaculture system against a traditional pond-based farm for the same production target.
Frequently asked questions
Does RAS reduce disease risk?
Biosecurity can be improved through controlled water exchange, but disease can spread rapidly within a shared recirculating system if not managed carefully.
What species are commonly farmed in RAS?
Salmon smolt, tilapia, trout and various shellfish and finfish species are commonly farmed in recirculating systems, particularly at hatchery and grow-out stages.
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Related terms
Hatchery Systems
Equipment and facility systems used to incubate eggs and rear early-stage animals, such as poultry chicks or fish fry, under controlled temperature, humidity and, in aquaculture, water quality conditions.
Fish Processing Line
Sequence of processing stations that transform whole harvested fish into graded, filleted, packed or frozen products, typically including reception, sorting, filleting, freezing and packaging steps.
Feasibility Study
Structured assessment of the technical, commercial, financial and operational viability of a proposed industrial project before significant capital commitment is made.
Industrial Sustainability
Management of a facility's environmental, resource and social impact, covering energy, water, waste and emissions, alongside conventional cost and output performance objectives.
Feed Mill
Industrial facility that grinds, mixes and processes raw agricultural ingredients into formulated compound feed for livestock, poultry or aquaculture species, typically finished through a pelleting line.
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Reference content only. Global B2B Group is independent of equipment manufacturers and financing institutions; definitions are provided for education and do not constitute engineering, financial or legal advice.