Calculate how efficiently your fish convert feed into body weight - the most critical metric in fish farming profitability.
FCR on industry scale (1.0 – 4.0)
Feed Conversion Ratio - abbreviated as FCR - is the single most important performance metric in commercial aquaculture. It quantifies how efficiently a fish farm converts feed into harvestable fish biomass. A FCR of 1.5 means that 1.5 kilograms of feed are required to produce 1 kilogram of fish weight gain. Lower FCR values indicate better feed efficiency, lower production costs, and stronger profitability.
Feed is the largest variable cost in fish farming, typically representing 50–65% of total operating expenses. Even a seemingly small difference in FCR - say 1.6 vs 1.9 - can translate into hundreds of thousands of dollars in savings at commercial scale. Understanding, measuring, and improving FCR is therefore central to the economic sustainability of any aquaculture operation.
The standard FCR formula is:
FCR = Feed Fed (kg) ÷ Net Weight Gain (kg)
Where net weight gain accounts for mortality:
Net Weight Gain = (Final Biomass − Initial Biomass) + Weight of Fish That Died
The mortality correction is essential and frequently overlooked by novice fish farmers. If fish die during the cycle, you've already fed them - that feed investment must be counted in the denominator as productive weight gain that was lost. Failing to account for dead fish weight artificially inflates (worsens) your apparent FCR, making your operation look less efficient than it truly is.
Example: You fed 2,500 kg of feed. Starting biomass was 500 kg; ending biomass is 1,800 kg. 40 fish died averaging 200 g each (8 kg total).
Net weight gain = (1,800 − 500) + 8 = 1,308 kg. FCR = 2,500 ÷ 1,308 = 1.91.
FCR is strongly species-dependent due to differences in metabolism, feed digestibility, and natural feeding behaviour. Key benchmarks from industry data:
High-quality, species-appropriate feed with correct protein levels, energy content, and digestibility coefficients dramatically lowers FCR. Cheap feed with low digestibility means more waste - both from uneaten feed and from undigested excretion. Extruded (floating) pellets typically achieve better FCR than sinking pellets because farmers can observe feeding activity and avoid overfeeding.
Each species has an optimal temperature range for growth and digestion. Outside this range, metabolic rate drops, appetite decreases, and FCR worsens. Tilapia FCR degrades significantly below 22°C; trout and salmon FCR worsens above 18°C. Seasonal temperature management - including shading ponds in summer and greenhouse systems in winter - is a key FCR lever.
Overcrowded fish experience chronic stress, which suppresses appetite and increases energy expenditure on stress responses rather than growth. This directly worsens FCR. However, too-low density underutilises the facility. Optimal stocking density for FCR is typically 70–85% of the system's maximum safe carrying capacity.
Multiple small meals per day achieve better FCR than one or two large meals. Fish can only digest so much feed at once - overfeeding leads to uneaten feed sinking to the pond bottom, where it decays and degrades water quality, creating a double loss (wasted feed + water quality stress). Demand feeders - devices that release feed when fish trigger a pendulum - consistently reduce FCR by 10–15% versus timed manual feeding.
Low dissolved oxygen reduces appetite and increases energy expenditure on respiration. High ammonia causes chronic stress. Both worsen FCR. Good water quality management - aeration, partial water exchange, biofilter performance - is a prerequisite for achieving benchmark FCR values.
Diseased or parasitised fish divert energy from growth to immune responses. Subclinical disease - where fish appear healthy but are under immunological stress - is a common cause of unexpectedly poor FCR. Regular health monitoring, sampling, and microscopic examination of gills are essential in high-value operations.
Consider a farm producing 100 tonnes of fish per year with feed costing $0.90/kg:
The difference between FCR 1.5 and FCR 2.1 is $67,500 per year - for a 100-tonne farm. At 500 tonnes/year, that difference exceeds $300,000. Investing in better feed quality, feeding management, and water quality systems often pays for itself many times over through FCR improvements.
Practical steps to reduce FCR in order of typical cost-effectiveness: