Production Record-Keeping and Data Analysis

Why Production Records Matter

In commercial aquaculture, decisions about feeding rates, stocking density, and harvest timing are only as good as the data behind them. A facility that relies on memory or informal notes will miss early warning signs — a gradual rise in daily mortality, a feed conversion ratio (FCR) creeping upward, or a dissolved oxygen level that dips on the same day each week. Systematic record-keeping transforms daily observations into a body of evidence that managers can act on. It also satisfies regulatory requirements, supports biosecurity audits, and provides the paper trail that fish health professionals need if a disease event occurs.

As an aquaculture technician, maintaining accurate logs is a core professional responsibility, not a clerical task.

The Standard Production Log

A production log captures the state of each tank or pond unit on a given day. At minimum, each daily entry should include:

• Date and tank/unit ID — unambiguous identification is essential when a facility runs dozens of tanks
• Feeding amount — grams or kilograms fed per tank, and feed brand/lot if it changes
• Mortality count — number of dead fish or shellfish removed, along with any notable condition (lesions, hemorrhage, unusual behavior)
• Water-quality readings — temperature, dissolved oxygen (DO), pH, salinity, ammonia (total ammonia nitrogen), and nitrite at minimum; record the time of measurement
• Observations — anything unusual: equipment alarms, power interruptions, abnormal fish behavior, new personnel

Leave no field blank. If a reading was not taken, write the reason (e.g., "probe malfunction — replacement ordered"). An unexplained blank is indistinguishable from data that was simply forgotten.

Paper Log and Digital Spreadsheet — Using Both

Most production facilities use a dual system. The paper log is filled out at the tank side, where spills, wet hands, and time pressure make simplicity essential. The digital spreadsheet is updated at the end of each shift from the paper log. The spreadsheet enables sorting, graphing, and formula-based calculations that paper cannot.

When entering data into the spreadsheet, transfer every value exactly as written on the paper log. If you notice a discrepancy while entering data — for example, a DO reading that is implausibly low — flag it with a note in the spreadsheet and initial the paper log. Do not silently correct data; always document the reason for any change.

Keep paper logs in a dedicated binder organized by date. Back up digital files at least daily, either to a shared network drive or a cloud service.

Feed Conversion Ratio (FCR)

FCR is the most widely used efficiency metric in fish culture. It tells you how many kilograms of feed were required to produce one kilogram of fish biomass.

FCR = Total feed fed (kg) ÷ Biomass gained (kg)

A lower FCR is better. A species-typical FCR for Atlantic salmon in intensive recirculating systems is roughly 1.1–1.3; for tilapia it is often 1.5–2.0. These benchmarks vary by species, life stage, feed quality, and management. Tracking FCR over time lets you detect feeding inefficiency before it becomes costly.

Mortality Rate

Daily mortality rate expresses the number of deaths as a percentage of the population at risk.

Daily mortality rate (%) = (Mortalities that day ÷ Estimated population) × 100

A sudden spike or a slow upward trend both warrant investigation. When graphed over ten days, even a modest trend is visible in a way it is not when reading raw numbers day by day.

Creating and Interpreting a Trend Graph

Select a single variable — FCR or daily mortality rate — and plot it on the y-axis against day number on the x-axis. Label both axes with units. Give the graph a descriptive title (e.g., "Tank 4 — Daily Mortality Rate, Days 1–10"). Add a simple trend line if your spreadsheet software supports it.

When interpreting the graph, address three things: (1) What is the overall direction of the trend? (2) Are there any obvious outliers or step changes, and what might explain them? (3) What does the trend suggest about current management?

Writing the Management Memo

A management memo is a brief, professional document that moves from observation to recommendation. Use this structure:

1. To / From / Date / Subject header

2. Background — one or two sentences on the data set (tank ID, dates, species)

3. Findings — describe the trend you observed and cite at least one specific data point

4. Recommendation — one clear, actionable change (e.g., reduce feeding rate by 10%, increase water-exchange frequency) with a data-based reason

5. Follow-up — how and when the effect of the change will be measured

Keep the memo to one page. Avoid vague language such as "fish seem stressed." Write instead: "Daily mortality rate rose from 0.1% on Day 1 to 0.6% on Day 9, suggesting a deteriorating condition that warrants investigation."

Safety Notes

Wet floors around tanks are a persistent slip hazard; wear non-slip boots whenever you are on the production floor. When handling dead animals for mortality counts, wear waterproof gloves and dispose of mortalities according to your facility's biosecurity protocol. If you handle water-quality reagents or probes that require calibration chemicals, consult the Safety Data Sheet (SDS) for each chemical and wear appropriate PPE — at minimum, chemical-splash goggles and nitrile gloves. Never lean over a tank unassisted when recording readings from probes at depth.