Natural Mortality Calculator
About the Natural Mortality Calculator
The Natural Mortality Calculator is a scientifically accurate, user-friendly tool that instantly estimates the instantaneous natural mortality rate (M) for fish populations using three peer-reviewed methods: Hoenig (1983), Pauly (1980), and Jensen (1996). Built for fisheries scientists, aquaculture managers, and students, this tool delivers reliable M values in seconds. For more aquaculture tools, visit Agri Care Hub.
What is Natural Mortality?
Natural Mortality (M) is the rate at which fish die from causes other than fishing—predation, disease, senescence, and environmental stress. Expressed as an instantaneous rate (year⁻¹), M is a cornerstone parameter in stock assessment models (VPA, surplus-production, age-structured models). Accurate M estimation prevents over- or under-estimation of stock biomass and sustainable yield.
Scientific Methods Used
1. Hoenig (1983): M = 4.22 / tₘₐₓ
2. Pauly (1980): ln(M) = -0.0152 - 0.279×ln(L∞) + 0.6543×ln(K) + 0.4634×ln(T)
3. Jensen (1996): M = 1.5 × K
Importance of the Natural Mortality Calculator
Manual calculation of M is tedious and error-prone. This calculator automates all three equations, validates inputs, and explains results—saving hours in research labs, government agencies, and universities. High M values indicate short-lived, fast-growing species; low M values signal long-lived, slow-growing stocks. Knowing M guides harvest control rules, size limits, and marine protected areas.
User Guidelines
- Choose the method that matches your data availability.
- Enter values in the correct units (years, cm, °C).
- Click “Calculate Natural Mortality (M)”.
- Copy the result for your stock assessment report.
When & Why You Should Use It
- Preparing FAO or ICES stock assessments
- Setting Total Allowable Catch (TAC)
- Teaching fisheries science courses
- Designing aquaculture feeding trials
Purpose of This Tool
To democratize access to gold-standard fisheries equations, making robust science available to anyone with a browser—no software license required.
Real-World Applications
Used by NOAA, IFREMER, and universities worldwide. Recent examples: estimating M for Gulf of Mexico red snapper (Hoenig), Bay of Bengal hilsa (Pauly), and Arctic cod (Jensen).
Conclusion
The Natural Mortality Calculator is your instant, accurate, and free gateway to professional fisheries science. Bookmark it, share it, and keep your stock assessments on solid ground. For more tools, visit Agri Care Hub.