Cost per Kilogram of Farmed Fish: How to Calculate It Properly

"What does a kilo of fish cost us to produce?" It sounds like a question every farm should be able to answer instantly. In practice, many answer it by dividing the annual cost by the annual harvest. That figure is easy to calculate and almost useless for decisions, because it mixes cohorts stocked in different years, under different conditions, with different survival and feed conversion.

This guide explains how to calculate cost per kilogram by cohort, works through a complete example, and shows which levers move the number most.

Why annual averages mislead

A typical Mediterranean grow-out cycle runs well over a year. In any calendar year, the harvest comes from fish stocked one or two years earlier, while this year's feed bill is partly feeding fish that will only be harvested next year.

Dividing this year's costs by this year's harvest therefore:

• Charges the current harvest with feed eaten by fish still in the water
• Hides the difference between a good cohort and a bad one
• Makes it impossible to see the effect of a management change, such as a new feed or a different stocking month, on the fish it actually affected

Cohort costing fixes this by following one group of fish, typically one stocking batch in one or more units, from stocking to harvest and allocating costs to it.

What goes into the cost

Group costs into categories that you can allocate consistently.

Direct biological costs - Juveniles: purchase price or internal transfer cost from your own hatchery, plus transport. - Feed: quantity fed to the cohort × actual price per lot, including freight. - Health: vaccines, veterinary visits, diagnostics, prescribed treatments.

Direct operating costs - Labour: staff time on feeding, sampling, net changes, grading, mortality removal. Allocate by unit-days or by biomass-days. - Vessels and fuel: service boats, feed barges. - Nets and maintenance: net changes, cleaning, repairs.

Capital and fixed costs (allocated) - Depreciation of cages, moorings, nets, boats and feeding systems. - Insurance, licences, site fees. - Overheads: management, office, monitoring systems.

Harvest and post-harvest (keep separate so you can compare farm-gate cost with delivered cost) - Harvesting, slaughter, ice, packing, boxes, labels.

The allocation key matters less than using it consistently. Biomass-days, the sum of standing biomass for each day the cohort is on the site, is a robust key for shared costs, because it reflects how much of the farm's capacity the cohort actually used.

Feed conversion: biological vs economic

Feed is usually the largest single cost, so the way you measure feed efficiency determines how well you can explain your cost per kilogram.

• Biological FCR (bFCR) = feed fed ÷ (biomass gain + weight of fish that died). It measures how efficiently the fish converted feed into body weight, including fish that later died.
• Economic FCR (eFCR) = feed fed ÷ net biomass gain (harvested biomass − stocked biomass). It measures how much feed it took to produce the kilograms you actually sold.

Mortality, escapes and unrecorded losses all widen the gap between the two. For costing, eFCR is the number that matters, because you pay for all the feed but sell only the surviving fish. Calculate both with the FCR calculator; a large gap between them points to losses rather than to feed quality.

A worked example

The numbers below are illustrative. They are chosen to make the arithmetic clear, not to represent any particular farm, species or market. Replace them with your own.

The cohort - 100,000 juveniles stocked at 10 g (stocked biomass 1,000 kg) - Juvenile cost: €0.25 each - Survival to harvest: 85 % (85,000 fish) - Harvest weight: 400 g average - eFCR: 1.8 - Feed price: €1.40/kg delivered

Biomass - Harvested biomass: 85,000 × 0.40 kg = 34,000 kg - Net biomass gain: 34,000 − 1,000 = 33,000 kg

Feed - Feed used: 33,000 × 1.8 = 59,400 kg - Feed cost: 59,400 × €1.40 = €83,160

Full cost to farm gate

Cost per kilogram at farm gate: €185,160 ÷ 34,000 kg = €5.45/kg

Feed accounts for 44.9 % of the total. Adding harvest and packing at an illustrative €0.60/kg (€20,400) gives a delivered-to-dispatch cost of €6.05/kg.

You can run the feed part of this calculation for your own figures with the fish feed cost calculator.

Sensitivity: which lever moves the number most?

Change one assumption at a time and see what happens to the farm-gate cost.

Three lessons stand out.

Survival is the strongest lever. Losing ten percentage points of survival costs more than either a significant FCR deterioration or a 10 % feed price increase. Fewer fish means fewer kilograms to spread fixed costs across, and fish that die mid-cycle have already eaten feed. Track it carefully with the mortality calculator.

FCR and feed price are roughly equal in effect at these values. A 0.2-point FCR deterioration costs about the same as a 10 % price rise. Since the farm controls FCR far more than it controls feed prices, that is where management attention pays. Model the value of an improvement with the FCR savings calculator and the impact of a price change with the feed price increase calculator. Practical ways to improve FCR are covered in how to improve FCR.

Fixed costs punish small harvests. Labour, depreciation and overheads do not shrink when a cohort underperforms. A farm running below capacity carries a higher cost per kilogram even if its biology is excellent.

Common errors that distort cost per kilogram

Using theoretical feed instead of feed actually fed. Feed tables give a plan. Costing needs the actual quantity, from feeding records or reconciled stock movements, including waste and spillage.

Ignoring feed price per lot. Feed bought at different times has different prices. Weighted averages by lot are more accurate than a single annual price. More on feed economics in our fish feed cost guide.

Not reconciling biomass. Estimated biomass in the cages drifts from reality as the cycle goes on. When the harvest comes in, reconcile actual harvested weight against the estimate and correct mortality and growth records. Large unexplained gaps usually mean unrecorded mortality or escapes.

Mixing cohorts in shared units. When fish from different batches are graded together, costs must be split by count or biomass at the time of mixing. Otherwise one batch silently subsidises the other.

Forgetting the cost of time. A cohort that takes four extra months to reach market size uses four more months of labour, depreciation and capacity. Slow growth is expensive even if FCR looks fine.

Cost per kilogram and financial reporting

Management costing and financial reporting answer different questions, but they should be reconcilable.

Under IFRS, IAS 41 Agriculture requires biological assets, such as live fish in cages, to be measured at fair value less costs to sell where fair value can be measured reliably. That means the balance sheet value of fish in the water reflects market-based value, not accumulated cost. Changes in that fair value go through profit or loss.

Cohort cost per kilogram is still essential under IAS 41: it is what management uses to price contracts, evaluate investment and judge performance. Farms reporting under other frameworks, including national GAAP, typically value stock at cost, which makes cohort costing directly relevant to the accounts. Your accountant will know which applies to you.

Building the routine

To make cohort costing routine rather than a year-end exercise:

1. Give every cohort an ID at stocking and keep it through grading, splitting and transfer.
2. Record feed daily by unit, and link each delivery to its lot and price.
3. Record mortality daily by unit and reconcile counts at every grading and harvest.
4. Allocate shared costs monthly using the same key (for example biomass-days).
5. Reconcile at harvest: actual harvested weight and count against estimates.
6. Close the cohort: final cost per kilogram, eFCR, survival and days on site, compared with budget and with previous cohorts.

Done by hand across dozens of units, this is a lot of bookkeeping, and errors creep in at every transfer. Production software that ties feeding, mortality, sampling and stock movements to cohort IDs produces cost per kilogram as a by-product of daily operations. See how this works in the farm operations demo.

Frequently asked questions

What share of fish farming costs is feed?

Feed is usually the largest single cost in grow-out and often accounts for roughly half of production costs, though the share varies with species, feed prices, FCR and the scale of other costs. In the illustrative example above, it is about 45 %.

What is the difference between biological and economic FCR?

Biological FCR divides feed by total biomass produced, including fish that died. Economic FCR divides feed by the net biomass actually harvested. Economic FCR is higher whenever there are losses, and it is the figure that matters for cost per kilogram.

Why is my cost per kilogram higher than my feed cost suggests?

Because feed is only part of the cost. Juveniles, labour, health, vessels, depreciation and overheads typically make up the other half or more. Low survival and slow growth also spread those costs over fewer kilograms.

How do I allocate shared costs between cages?

Use a consistent key that reflects resource use. Biomass-days, the sum of daily standing biomass for each unit, is widely used because it accounts for both how much fish a unit holds and how long it holds them.

Does IAS 41 change how I calculate production cost?

No. IAS 41 changes how fish in the water are valued in financial statements, at fair value less costs to sell where measurable. Cohort production cost remains the key management figure for pricing, budgeting and performance analysis.

Key takeaways

• Calculate cost per kilogram by cohort, not by dividing annual costs by annual harvest.
• Use economic FCR for costing; the gap to biological FCR shows your losses.
• In the illustrative example, a ten-point drop in survival raised cost per kilogram about twice as much as either a 0.2 FCR deterioration or a 10 % feed price increase.
• Reconcile biomass at every harvest and track feed by lot price.
• Make costing a by-product of daily records by tying feed, mortality and stock movements to cohort IDs.