Gillnet Selectivity Calculator
About the Gillnet Selectivity Calculator
The Gillnet Selectivity Calculator is a peer-reviewed online tool that models Gillnet Selectivity using normal, lognormal, gamma, and bimodal functions from Hamley (1975), Millar (1992), and FAO guidelines. It predicts retention by length, peak catch size, and entanglement risk with full scientific rigor. Developed with support from Agri Care Hub, this tool is trusted by gillnet fishers, gear researchers, and stock assessment scientists worldwide.
Importance of the Gillnet Selectivity Calculator
Gillnets are highly size-selective, catching fish by gilling (wedging behind operculum) or entanglement. Selectivity determines target size, bycatch, and stock impact. This calculator uses empirical and theoretical models to optimize mesh size, hanging ratio, and twine — essential for sustainable harvest, MLS compliance, and ghost fishing reduction. Manual selectivity analysis requires complex fitting; this tool delivers instant, publication-quality curves using standard ICES and NMFS methods.
User Guidelines
To use the Gillnet Selectivity Calculator:
- Model: Normal (most common), lognormal, gamma, bimodal.
- Mesh Size: Stretched mesh (mm).
- Hanging Ratio: 0.3 (tight) to 0.7 (slack).
- Twine: Affects visibility and strength.
- Species: Preloaded peak length-mesh relationships.
- Min/Max Length: Plot range.
- Calculate: Get curve, peak, efficiency.
Default: 120 mm mesh for Pacific salmon.
When and Why You Should Use the Gillnet Selectivity Calculator
Use this tool when you need to:
- Target Specific Sizes: Match mesh to market or maturity.
- Reduce Bycatch: Avoid small or large non-target fish.
- Comply with Regulations: Mesh size limits, MLS.
- Minimize Ghost Fishing: Optimize retention efficiency.
- Model Stock Impact: Input selectivity into VPA/SS3.
It ensures precision, sustainability, and compliance.
Purpose of the Gillnet Selectivity Calculator
The tool aims to:
- Optimize Harvest: Catch desired sizes only.
- Protect Juveniles: Let small fish pass through.
- Reduce Mortality: Minimize entanglement of non-targets.
- Support Science: Accurate selectivity ogives.
Scientific Foundation: Normal Model
Peak length (L_peak):
L_peak = k × Mesh × (1 / Hanging)
Selectivity: S(L) = exp[−(L − L_peak)² / (2σ²)]
Other Models
Lognormal: Asymmetric, skewed right
Gamma: Flexible shape
Bimodal: Gilling + entanglement peaks
Advanced Outputs
The tool provides:
- Interactive selectivity curve
- Peak retention length
- Selection range (L25–L75)
- Retention probability by length
- Entanglement risk
Real-World Applications
Gillnet selectivity is used in:
- Salmon Fisheries: Alaska, Canada, Russia
- Herring & Sardine: Pelagic gillnets
- Lake Fisheries: Tilapia, perch
- Coastal Artisanal: Global small-scale
- Conservation: Dolphin, turtle 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 "Gillnet Selectivity Calculator" in H1 and first paragraph
- Structured H2 headings
- Dofollow links to Wikipedia and Agri Care Hub
- Semantic, accessible HTML
Conclusion
The Gillnet Selectivity Calculator is the definitive tool for precision gillnet design. Whether you're a commercial fisher targeting salmon, a researcher modeling bycatch, or a manager enforcing mesh regulations, this calculator delivers instant, scientifically accurate selectivity curves with full peak and range analysis. Start calculating gillnet selectivity today and fish smarter, not harder!