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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,

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Presentation on theme: "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,"— Presentation transcript:

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 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 NettingKnotless NettingHexagonal Mesh Bar or Square Bar OM = Mesh Opening a = Stretched Mesh OM = Mesh Opening a = Stretched Mesh Mesh Opening

3 Primary Hanging Ratio “Horizontal Orientation of Netting” E 1 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. L o is the length of netting when fully extended. (stretched netting before hanging) E 1 = L ÷ Lo Therefore L = E 1 x Lo and Lo = L ÷ E 1

4 Secondary Hanging Ratio “Vertical Orientation of Netting” E 2 is the Secondary or Vertical Hanging Ratio. H is the “hung” height or depth of the netting or the fully mounted net. H o is the height of the netting when fully extended. (stretched netting before hanging) E 2 = H ÷ Ho Therefore H = E 2 x Ho and Ho = H ÷ E 2

5 Geometric Determination of Hanging Ratios 1 - E² E 2 = 1 – E 1 ²E 1 = 1 – E 2 ² and

6 Common Hanging Ratios Hydrodynamic Gear Gillnets Entanglement Gear

7 Hanging Ratio Tables

8 Surface Covered at Different Hanging Ratios

9 (A-2)

10 Sample Plans: Gill Net Bottom set, Germany (A-3)

11 Sample Plans: Gill Net Bottom set, Australia (A-4)

12 Sample Plans: Entangling Net Bottom Set, Japan (A-5)

13 Sample Plans: Entangling Net (Trammel Net) Bottom Set, France (A-6)

14 Sample Plans: Seine Net Nigeria (A-7)

15 (A-8)

16 Sample Plans: Four-Seam Flat Trawl Shrimp, Gulf & South Atlantic, USA (A-9)

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

22 Plans: Four-Seam Semi-Balloon Trawl Shrimp, Gulf & South Atlantic, USA (A-11)

23 Plans: Western-Jib 4-Seam Trawl Shrimp, Gulf & South Atlantic, USA (A-12)

24 (A-13)

25 (A-14)

26 Sample Plans: Bottom Trawl Cod, Germany (A-15)

27

28 Sample Plans: Pot Snapper, Venezuela (A-17)

29


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