1. MSC 132/134 Fishing Gear Technology I & II
Appendix: Netting Theory and Tapers
Excerpts from:
FAO Cataloque of Small Scale Fishing Gear, Edited by C. Nedelec, Fishing News Books Ltd. & Whitefriars Press Ltd., London, England. 1975
Fisherman’s Workbook,compiled by J. Prado, Fishing News Books, Oxford:1990
Shrimp Trawl Design & Performance, D. Harrington, J. Watson, L. Parker, J. Rivers, C. Taylor, Georgia Sea Grant Program, Marine Extension Service, University of Georgia, Athens, Georgia. 1988

2. Meshes: Types and Measurement Methods
Knotted Netting
Knotless Netting
Hexagonal Mesh
Bar or Square
Bar or Square
Bar
Mesh Opening
OM = Mesh Opening
a = Stretched Mesh
OM = Mesh Opening
a = Stretched Mesh
a = Stretched Mesh

3. Primary Hanging Ratio “Horizontal Orientation of Netting”
E1 = L ÷ Lo
E1 is the Primary or Horizontal Hanging Ratio. L is the “hung” length of the netting or the length of rope on which a net panel is mounted. Lo is the length of netting when fully extended. (stretched netting before hanging)
Therefore L = E1 x Lo
and
Lo = L ÷ E1

4. Secondary Hanging Ratio “Vertical Orientation of Netting”
E2 = H ÷ Ho
E2 is the Secondary or Vertical Hanging Ratio. H is the “hung” height or depth of the netting or the fully mounted net.
Ho is the height of the netting when fully extended. (stretched netting before hanging)
Therefore H = E2 x Ho
and
Ho = H ÷ E2

5. Geometric Determination of Hanging Ratios
E2 = 1 – E1²
E1 = 1 – E2²
and

6. Common Hanging Ratios
Gillnets
Entanglement
Gear
Hydrodynamic
Gear

7. Hanging Ratio Tables

8. Surface Covered at Different Hanging Ratios

9. (A-2)

10. Sample Plans: Gill Net Bottom set, Germany

11. Sample Plans: Gill Net Bottom set, Australia

12. Sample Plans: Entangling Net Bottom Set, Japan

13. Sample Plans: Entangling Net (Trammel Net) Bottom Set, France

14. Sample Plans: Seine Net Nigeria

15. (A-8)

16. Sample Plans: Four-Seam Flat Trawl Shrimp, Gulf & South Atlantic, USA

17. Standard Net Plan Layout: Cutaway View

18. Net Plan with Hidden Lines: Uncommon

19. Full Net Plan Layout: More Detail but not commonly used.

20. 3P2B

21. (A-10)
Sample Plans: Two-Seam Balloon Trawl Shrimp, Gulf & South Atlantic, USA

22. Plans: Four-Seam Semi-Balloon Trawl Shrimp, Gulf & South Atlantic, USA

23. Plans: Western-Jib 4-Seam Trawl Shrimp, Gulf & South Atlantic, USA

24. (A-13)

25. (A-14)

26. Sample Plans: Bottom Trawl Cod, Germany

28. Sample Plans: Pot Snapper, Venezuela