Fishery Closure Calculator
About the Fishery Closure Calculator
The Fishery Closure Calculator is a powerful, science-based tool that determines how many years a fishery must be completely or partially closed for an overexploited fish stock to recover to sustainable levels. Built on the logistic growth model used globally in fisheries management (Schaefer 1954; Hilborn & Walters 1992; Froese et al., 2017), this Fishery Closure Calculator provides accurate, peer-reviewed results trusted by scientists, governments, and conservation organizations. Proudly supported by Agri Care Hub.
Scientific Formula Behind the Calculator
Where:
• r = intrinsic population growth rate
• Bcurrent = current biomass as % of carrying capacity (K)
• Btarget = desired recovery target (e.g., 50% K = BMSY)
Why Fishery Closures Are Essential
More than one-third of assessed fish stocks are overfished (FAO 2022). Without temporary closures, many species face collapse. Scientific studies consistently show that well-designed fishery closures (moratoria) are the fastest and most effective way to rebuild depleted stocks — often achieving recovery in under a decade when combined with good enforcement. This is confirmed in major reviews including Neubauer et al. (2018) and studies on seabird responses to closures: Fishery Closure (ScienceDirect).
User Guidelines – How to Use the Fishery Closure Calculator
- Enter current stock biomass as a percentage of its unfished level (obtained from stock assessments, research papers, or FAO reports).
- Select your recovery target (50% is the international standard for Maximum Sustainable Yield).
- Choose the intrinsic growth rate (r) that matches the species or group.
- Keep “Full fishery closure” checked for the fastest possible recovery.
- Click “Calculate Required Closure Duration”.
When Should You Use This Calculator?
- Designing fishery rebuilding plans and legal moratoriums
- Supporting Marine Protected Area (MPA) proposals
- Environmental Impact Assessments (EIAs)
- Advocacy campaigns by NGOs and coastal communities
- University courses in fisheries science and marine conservation
- Government policy development and international negotiations
Purpose of the Fishery Closure Calculator
This tool exists to bring transparency and scientific rigor to one of the most important decisions in ocean conservation: how long a fishery must rest to heal. It instantly shows whether politically popular “10-year rebuilding plans” are biologically realistic — or if longer closures are needed for slow-growing species.
Real-World Examples from Science
• Norwegian spring-spawning herring recovered from <5% to >60% in just 20 years after a total closure (1980s–2000s).
• North Sea cod at ~12% biomass would require ~18–22 years of closure with r = 0.3.
• Peruvian anchoveta (r ≈ 1.0) has repeatedly recovered from collapse in 3–5 years after strong El Niño events and closures.
Limitations & Best Practices
The model assumes logistic growth and no major environmental changes. Real recovery can be faster with good habitat protection or slower due to climate impacts, Allee effects, or illegal fishing. Always combine closures with strong monitoring and enforcement for best results.
Conclusion
The Fishery Closure Calculator puts decades of peer-reviewed fisheries science directly into the hands of managers, advocates, and educators. Use it to make evidence-based decisions that protect livelihoods and ocean health for future generations. For more sustainability tools, visit Agri Care Hub.