1. Comparable fish
Match species, life stage, starting size, stocking period and production system.
Benchmark aquaculture production data by comparing similar cohorts over the same period, using consistent calculations and checking record quality first. A low FCR or fast growth rate is a signal to understand—not proof that a cage is performing better.
2. Comparable records
Align dates, units, feed definitions, mortality and fish movements.
3. Explain the difference
Review sampling, environment and management before attributing an anomaly to fish losses.
Start with a minimum dataset
For each cage, assemble dated stock numbers and weights, weight samples, feed quantities, mortalities, transfers and harvests. Add temperature, dissolved oxygen, feed type and health or treatment events where available. Record missing information explicitly.
Keep original records alongside corrections. Note who changed a value and why; an unexplained correction can make a comparison look better without making it more reliable.
Compare growth, feed conversion and stock records together
| Indicator | What to compare | Main caution |
|---|---|---|
| Growth | Weight gain and SGR over matching periods | Sample quality, starting size and temperature differ. |
| Feed conversion | Feed supplied relative to consistently defined biomass production | Stock errors affect the denominator; delivered feed is not necessarily consumed feed. |
| Stock reconciliation | Stocking + transfers in − transfers out − recorded deaths − harvested fish | This is a record balance, not an independent count. |
Calculation definitions to agree before comparing
Estimated biomass (kg) = recorded fish number × average fish weight (g) ÷ 1,000. Both inputs have uncertainty.
SGR (% per day) = 100 × [ln(final mean weight) − ln(initial mean weight)] ÷ elapsed days. Use positive weights in the same units. SGR alone does not adjust for temperature or life stage.
FCR = feed supplied (kg) ÷ biomass production (kg), over the same interval. State whether your definition accounts for mortality biomass, harvests and transfers. Compare biological FCR only with the same biological FCR convention; do not mix it with an economic FCR that uses a different production basis. An interval with zero or negative calculated production needs investigation rather than a routine FCR comparison.
A simple example: the stock assumption matters
Hypothetical arithmetic example—not a PFD result.
Assume 100,000 fish, weights increasing from 200 g to 300 g, 16,000 kg of feed, and no mortality, transfers or harvests during the interval.
- Calculated starting biomass: 20,000 kg.
- Calculated ending biomass: 30,000 kg.
- Calculated biomass gain: 10,000 kg.
- FCR: 16,000 ÷ 10,000 = 1.60.
The arithmetic is consistent with those assumptions. It does not establish that 100,000 fish are present or that either weight sample represents the whole cage. Changing the stock assumption changes the calculated FCR without changing the feed record.
Investigate an outlier before changing management
- Check sample dates, size distribution and whether capture methods could bias average weight.
- Reconcile stocking, mortality, harvest and transfer records; check feed units and duplicate entries.
- Review temperature, oxygen, appetite, pathology, feeding interruptions and compensatory growth.
- Test whether the biological model is suitable for the species, size and farm conditions.
- Seek reliable, separately reconciled counting or harvest evidence before changing official fish numbers.
Where aquaculture AI can help—and where it cannot
PFD compares existing production records with biological models to flag potential stock discrepancies. AI-assisted interpretation can help explain patterns and questions to investigate. Biological calculations should remain auditable; AI explanations do not replace source records, model checks or farm expertise.
Several indicators may share the same weight, feed or stock inputs. Their agreement can support an investigation, but it is not independent validation. PFD does not directly count fish.
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FAO training materials explain the importance of sampling and production records, define feed conversion, and describe biological and management explanations for poor feed performance. They support the general principles here; they are not validation of PFD.
- FAO: feeding and feed conversion
- FAO: production records and stock checks
- FAO: biomass assessment and feeding
This guide provides a practical comparison framework, not universal performance targets. Benchmark suitability depends on your species, system and operating conditions.