Atlantic salmon (Salmo salar) is an anadromous species that hatches and grows in freshwater before migrating to the ocean, where it spends most of its grow-out phase. Atlantic salmon is the dominant aquaculture species in Norway, Scotland, the Faroe Islands, Iceland, Canada and Chile, accounting for the majority of global farmed salmon production. Traditionally produced in sea cages, the industry is increasingly adopting land-based systems for smolt production, post-smolt rearing and, in some cases, full grow-out to harvest size.
Atlantic salmon performs best in cool, well-oxygenated water. Growth rates are strongly influenced by temperature, with optimal growth typically occurring between approximately 10 and 16 °C. Elevated temperatures increase metabolism, oxygen demand and disease risks, while prolonged exposure to warm water can lead to reduced feed intake, stress and mortality. Temperature control is therefore a critical design consideration in both freshwater and seawater RAS.
Water quality and RAS
Modern RAS salmon production requires strict management of water quality. Key parameters include dissolved oxygen (DO), carbon dioxide (CO₂), ammonia (TAN), nitrite, alkalinity, pH, salinity and suspended solids. Atlantic salmon are particularly sensitive to elevated CO₂ concentrations, making degassing systems an essential component of recirculating facilities. Efficient oxygenation and robust biofiltration are required to support high biomass densities while maintaining fish welfare and growth performance.
Biosecurity
Biosecurity is a major driver behind land-based salmon farming. Closed systems can reduce exposure to sea lice, pathogens, harmful algal blooms and environmental fluctuations that affect open-net pen production. However, this requires rigorous disinfection protocols, quarantine procedures, water treatment systems and continuous monitoring to prevent disease outbreaks within the facility.
Typical production stages
- Broodstock
- Egg incubation
- Freshwater fry and parr
- Smolt production
- Post-smolt grow-out
- Harvest-size production
Atlantic salmon remains the benchmark species for large-scale recirculating aquaculture technology and has been a major driver of innovation in biofiltration, oxygenation, water treatment, automation, fish health monitoring and backup life-support systems. Today, salmon RAS facilities range from small freshwater hatcheries producing a few million smolts annually to industrial-scale land-based farms targeting tens of thousands of tonnes of harvest-size fish per year.
Production timeline and growth (orientation)
Atlantic salmon has one of the longest production cycles in aquaculture. Exact duration depends on strain, temperature, feeding, photoperiod and whether production is in traditional sea cages or RAS. The tables below are typical ranges under favourable conditions — not guaranteed protocols.
| Stage | Size / weight | Typical duration |
|---|---|---|
| Egg incubation | Fertilised egg → hatch | ~2–3 months (depends on °D and temp) |
| Alevin (yolk sac) | Newly hatched | Weeks to swim-up |
| First-feeding fry | ~0.2–1 g | Weeks–months |
| Fingerling / parr | ~5–80 g | Months in freshwater |
| Smolt | ~80–200 g (classic) | ~8–18 months from egg |
| Large smolt / post-smolt | ~0.3–1 kg | ~16–22 months from egg |
| Seawater grow-out or grow-out RAS | to 3–7 kg | +12–24 months after smolt |
| Harvest fish | ~3–5 kg typical | ~24–36 months from egg |
| Large premium harvest | ~5–7 kg | ~30–36+ months from egg |
Ranges under favourable conditions. Strain, temperature, density and health change the timeline.
Example growth progression
Approximate progression under favourable conditions (orientation):
| Time from fertilisation | Approximate size |
|---|---|
| Day 0 | Fertilised egg |
| 2–3 months | Hatch |
| 4–5 months | First-feeding fry |
| 7–9 months | 5–10 g parr |
| 10–14 months | 30–80 g parr |
| 12–18 months | 80–200 g smolt |
| 16–22 months | 0.5–1.0 kg post-smolt |
| 24–30 months | 3–5 kg harvest fish |
| 30–36 months | 5–7 kg premium harvest |
Modern post-smolt RAS often delivers 300–1,000 g before sea transfer; classic hatcheries often deliver 80–150 g smolt. Fully land-based food fish omits the marine phase.
- Rule of thumb: about 8–18 months egg → smolt
- About 16–24 months smolt → harvest (3–6 kg)
- About 24–36 months total egg → 4–6 kg harvest
This long production cycle is one reason salmon farmers place strong emphasis on biosecurity, backup power, oxygen supply and water quality management, as losses at any stage can represent years of biological investment.
Calculator: time-to-weight & production chain
The tool estimates time from start phase/weight to target weight (based on the orientation growth curve above) and proposes a simplified tank/stage chain toward an annual production target. Density, survival and number of tank sizes are adjustable. Orientation — not bankable facility design.
Calculator: Atlantic salmon — time-to-weight & production chain
1. Time from start to target weight
Approximate growth (orientation)
Curve uses the same orientation data as the time calculator; tempo scales the x-axis. Logarithmic weight axis. Orientation — not a feed-control growth model.
2. Production chain toward annual target
H/W = water depth ÷ diameter (round) or flat–flat span (octagon). Optimal default 0.30 ≈ Ø:depth 3.3:1 (typical circular RAS tanks). Lower = flatter/larger footprint; higher = deeper/narrower.
Density (kg/m³) by fish size — adjust to strategy. More stages ⇒ shorter time per tank and sizing to exit weight ⇒ lower total volume.
Stages in the chain
| Stage | Weight (g) | Months | Fish in stage (avg) | Biomass (t) | kg/m³ | Volume (m³) |
|---|
Suggested tank plan
| Tank class | Stage | Days in tank | Unit volume | Depth | Area / tank | Diameter / span | Units | Class volume |
|---|
3. Layout generator (to scale, area = CAPEX) (Experimental)
Packing biased to the golden ratio (φ≈1.618): D+1.0 m cells, grid/shelf and a segment meta-grid so the hall is not one long thin strip.
Packing runs as JS in the browser (grid + shelf). Shared service D+1.0 m. Dashed circle = 0.5 m service zone. Orientation — not construction documentation.
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See also
Sources/overview (selection): established industrial practice for Salmo salar (cages, smolt, post-smolt, land-based RAS); Timmons & Ebeling and others on RAS; public industry statistics (Norway etc.). Growth and density figures are orientation — strain, temperature, feed and health govern real time and volume.