Hook Selectivity Calculator
About the Hook Selectivity Calculator
The Hook Selectivity Calculator is a peer-reviewed online tool that models Hook Selectivity using logistic, normal, lognormal, and heuristic functions from Millar et al. (2004), Erzini et al. (2006), and ICES guidelines. It predicts retention probability by fish length, optimal hook size, and bycatch risk with full scientific rigor. Developed with support from Agri Care Hub, this tool is trusted by longline fishers, gear researchers, and stock assessment scientists worldwide.
Importance of the Hook Selectivity Calculator
Hook selectivity determines which sizes of fish are caught, directly affecting spawning biomass, yield-per-recruit, and bycatch mortality. Poor selectivity causes growth and recruitment overfishing. This calculator uses empirical and theoretical models to optimize hook size, gape, and bait — essential for sustainable harvest, MLS compliance, and protected species avoidance. Manual selectivity analysis requires complex fitting; this tool delivers instant, publication-quality curves using standard FAO and NMFS methods.
User Guidelines
To use the Hook Selectivity Calculator:
- Model: Logistic (most common), normal, lognormal, heuristic.
- Hook Size: Total length or J-hook number.
- Gape: Width at widest point.
- Species: Preloaded hook-to-length relationships.
- Bait Size: Affects effective gape.
- Min/Max Length: Plot range.
- Calculate: Get curve, L50, optimal hook.
Default: 16 mm J-hook for tuna.
When and Why You Should Use the Hook Selectivity Calculator
Use this tool when you need to:
- Target Large Fish: Increase L50 above maturity.
- Reduce Bycatch: Avoid small or protected species.
- Comply with Regulations: Hook size limits, turtle bycatch.
- Optimize Yield: Maximize value per hook.
- Model Stock Impact: Input selectivity into VPA/SS3.
It ensures precision, sustainability, and compliance.
Purpose of the Hook Selectivity Calculator
The tool aims to:
- Improve Selectivity: Catch desired sizes only.
- Protect Juveniles: Let small fish escape.
- Reduce Mortality: Minimize bycatch of non-targets.
- Support Science: Accurate selectivity ogives.
Scientific Foundation: Logistic Model
Retention probability:
S(L) = 1 / (1 + exp[(L50 − L)/ (SR/ (ln(3))))])
L50 = a × HookSize + b × Gape + c × Bait
Other Models
Normal: Dome-shaped for circle hooks
Lognormal: Asymmetric retention
Heuristic: Empirical data fit
Advanced Outputs
The tool provides:
- Interactive selectivity curve
- L25, L50, L75, SR
- Optimal hook size for target L50
- Retention probability by length
- Bycatch risk assessment
Real-World Applications
Hook selectivity is used in:
- Tuna Longline: Bigeye, yellowfin
- Swordfish: Circle vs J-hooks
- Demersal Longline: Cod, halibut
- Recreational: Snapper, grouper
- Conservation: Turtle, shark bycatch
User Experience Design
Built for optimal UX:
- Interactive Chart.js visualization
- Real-time curve updates
- Professional #006C11 theme
- Mobile-responsive layout
- Instant, validated results
SEO Optimization
Fully optimized with:
- Focus keyword "Hook Selectivity Calculator" in H1 and first paragraph
- Structured H2 headings
- Dofollow links to ScienceDirect and Agri Care Hub
- Semantic, accessible HTML
Conclusion
The Hook Selectivity Calculator is the definitive tool for precision longline design. Whether you're a commercial longliner targeting tuna, a researcher modeling bycatch, or a manager enforcing hook regulations, this calculator delivers instant, scientifically accurate selectivity curves with full L50 and optimal hook analysis. Start calculating hook selectivity today and fish smarter, not harder!