Track cumulative mortality, calculate daily and weekly loss rates, project survival to harvest, and identify warning thresholds based on species-specific benchmarks.
Track cumulative deaths week by week. The weekly mortality rate is auto-calculated. Data is stored in your browser session only.
| Week End Date | Cumulative Deaths | Weekly Deaths | Weekly Mort. Rate | Remove |
|---|---|---|---|---|
| - | - |
Weekly mortality rate = weekly deaths ÷ fish alive at start of week. Requires initial stocking number to be entered in the calculator above.
In aquaculture, mortality is not just a welfare concern - it is a direct economic loss. Each dead fish represents lost feed, lost capital, lost revenue, and potentially a harbinger of a larger problem about to emerge. Systematic mortality recording, analysis, and response is therefore one of the most fundamental management practices in any professional fish farming operation. Operators who monitor mortality daily and investigate anomalies promptly consistently outperform those who address problems only when they become visually obvious.
Some level of mortality is unavoidable in any aquaculture operation. Background or "base" mortality - from random accidents, subclinical disease, dominance hierarchies, and natural senescence - is expected in all systems. The question is whether the observed mortality rate falls within the acceptable range for the species, system, and production stage. Fingerling and early grow-out stages typically carry the highest mortality risk, while mortality rates generally decline as fish approach market size. Cold-water species like salmon and trout tend to have lower acceptable daily mortality rates than tropical warm-water species.
As a general guide, daily mortality rates above 0.1–0.2% for most species warrant investigation. Weekly mortality rates above 1% are a red flag requiring immediate action. These thresholds are encoded in the species-specific benchmark data in this tool.
Dissolved oxygen (DO) crashes are the single most common cause of acute mass mortality in aquaculture. They can occur when algal blooms die and decompose overnight (consuming oxygen), when power fails (stopping aeration pumps), during hot still days (reduced oxygen solubility), or when stocking density exceeds the system's oxygen delivery capacity. Early warning signs include fish crowding at inlets, surface gasping, and reduced feeding response. DO monitoring equipment with alarms is an essential investment.
Disease-related mortality typically begins as scattered individual deaths and escalates to a recognisable mortality spike over several days to weeks. The pattern of mortality (which size classes are affected, where in the pond or tank deaths are occurring, whether there are external lesions) provides crucial diagnostic information. Disease outbreaks in aquaculture are almost always secondary to a primary stressor - typically water quality deterioration, handling stress, or nutritional deficiency.
Handling - netting, grading, transferring - causes acute physical and physiological stress. Post-handling mortality typically peaks 24–72 hours after the event. Minimising handling frequency, using anaesthesia (clove oil or MS-222) for sensitive operations, and conducting handling in cool morning temperatures significantly reduces stress mortality. Salt addition (1–3 g/L) during and after handling helps osmoregulation.
Ammonia spikes (from equipment failure, overfeeding, or excess organic load), pH crashes (from CO₂ accumulation or loss of alkalinity buffering), and nitrite accumulation can each cause significant mortality. These events are diagnosable through water testing and typically respond quickly to corrective action if caught early.
When mortality exceeds the expected background rate, follow a systematic investigation protocol: 1) Measure water quality immediately - DO, temperature, pH, ammonia, nitrite. 2) Examine dead fish externally and internally for lesions, haemorrhages, parasites, or abnormalities. 3) Review recent management events - feeding changes, handling, new stock introductions, weather events. 4) Consult a veterinarian for bacteriology or virology if the cause is unclear after the initial assessment. 5) Document everything - date, number dead, water quality readings, clinical observations, and action taken.
Comprehensive mortality records are essential for aquaculture insurance claims, regulatory compliance, and production performance benchmarking. Records should include daily mortality counts per unit (pond, cage, or tank), cumulative totals, species-specific survival rates at key production stages, and documented responses to mortality events. Many jurisdictions also require reporting of notifiable diseases regardless of mortality level. Modern farm management software automates much of this record-keeping, but even a simple spreadsheet maintained consistently provides enormous value for retrospective analysis and future planning.