Fish Mortality Rate Calculation

Fish Mortality Rate Calculator

Calculate survival percentage, total loss, and mortality rates for aquaculture or aquariums.

function calculateFishMortality() { var initial = document.getElementById('initialStock').value; var current = document.getElementById('currentStock').value; var days = document.getElementById('timeElapsed').value; var resultBox = document.getElementById('fmrResult'); var dailyRow = document.getElementById('dailyRateRow'); // Input Validation if (initial === "" || current === "") { alert("Please enter both Initial Stock and Current Stock counts."); return; } var n0 = parseFloat(initial); var nt = parseFloat(current); var t = parseFloat(days); if (isNaN(n0) || isNaN(nt)) { alert("Please enter valid numbers for stock counts."); return; } if (n0 n0) { alert("Current stock cannot be higher than initial stock for mortality calculations."); return; } // Core Calculations var lost = n0 – nt; var survivalRate = (nt / n0) * 100; var mortalityRate = (lost / n0) * 100; // Display Basic Results document.getElementById('resLost').innerHTML = lost.toLocaleString(); document.getElementById('resSurvival').innerHTML = survivalRate.toFixed(2) + "%"; document.getElementById('resMortality').innerHTML = mortalityRate.toFixed(2) + "%"; // Daily Rate Calculation (if days provided) if (!isNaN(t) && t > 0) { // Calculate simple daily percentage loss relative to initial stock var dailyAvg = mortalityRate / t; document.getElementById('resDaily').innerHTML = dailyAvg.toFixed(3) + "% / day"; dailyRow.style.display = "flex"; } else { dailyRow.style.display = "none"; } // Show results container resultBox.style.display = "block"; }

Understanding Fish Mortality Calculations

In aquaculture, fisheries management, and even hobbyist aquarium keeping, monitoring the Mortality Rate is the primary metric for assessing the health of a fish population. It represents the percentage of fish that have died over a specific period relative to the initial population.

Accurate calculation helps in diagnosing water quality issues, disease outbreaks, or feed management problems. Keeping the survival rate high is directly correlated with the profitability of commercial farms and the sustainability of conservation efforts.

The Formulas Used

This calculator determines three key metrics based on your input:

• Total Fish Lost: Simply the difference between your stocking count and harvest count.
  Formula: Initial Stock – Current Stock
• Survival Rate (%): The percentage of fish that are still alive.
  Formula: (Current Stock / Initial Stock) × 100
• Cumulative Mortality Rate (%): The percentage of the population lost.
  Formula: ((Initial Stock – Current Stock) / Initial Stock) × 100

Example Calculation

Imagine a tilapia farm stocks a pond with 5,000 fingerlings. After a grow-out period of 120 days, the farmer harvests 4,650 fish.

• Fish Lost: 5,000 – 4,650 = 350 fish
• Survival Rate: (4,650 / 5,000) × 100 = 93%
• Mortality Rate: (350 / 5,000) × 100 = 7%
• Daily Mortality: 7% / 120 days = 0.058% per day

Why Monitoring Daily Mortality Matters

While the cumulative rate tells you the final outcome, the Daily Mortality Rate is an early warning system. In commercial aquaculture, a sudden spike in daily mortality (often exceeding 0.1% to 0.5% depending on species) indicates an acute problem such as low dissolved oxygen or a bacterial infection that requires immediate intervention.