MSC 132/134 Fishing Gear Technology I & II

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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, 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

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

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

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

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

Common Hanging Ratios Gillnets Entanglement Gear Hydrodynamic Gear

Hanging Ratio Tables

Surface Covered at Different Hanging Ratios

(A-2)

Sample Plans: Gill Net Bottom set, Germany

Sample Plans: Gill Net Bottom set, Australia

Sample Plans: Entangling Net Bottom Set, Japan

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

Sample Plans: Seine Net Nigeria

(A-8)

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

Standard Net Plan Layout: Cutaway View

Net Plan with Hidden Lines: Uncommon

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

3P2B

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

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

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

(A-13)

(A-14)

Sample Plans: Bottom Trawl Cod, Germany

Sample Plans: Pot Snapper, Venezuela