Fixed mesh constructions are required to reduce variability in codend size selectivity

Zita Bak-Jensen*, Bent Herrmann, Juan Santos, Valentina Melli, Jordan P. Feekings, Daniel Stepputtis

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review

Abstract

In demersal trawls the most commonly used codends are diamond-mesh. However, diamond-mesh codends is discovered to vary in mesh geometry which lead to a less well-defined size selection process. One alternative often adopted to reduce variability in mesh geometry, and thereby obtain a sharper size selection, is to force the meshes to adopt a square geometry by turning the codend netting 45 degrees (T45 standard square-mesh). Therefore, we tested the size selectivity of a standard square-mesh and a standard diamond-mesh codend and a fixed diamond-mesh codend whose mesh geometry was optimally defined to suite the morphology of cod. Using Atlantic cod (Gadus morhua) as a case study, we found no evidence that the square-mesh codend had lower variability in size selection than a standard diamond-mesh codend with same mesh size. Moreover, we demonstrated that the square-mesh codend had significantly larger variability in size selection compared to what was obtained with a codend where the mesh geometry was kept fixed during the fishing process. These results demonstrate that the use of square-mesh codends is not a sufficient strategy to reduce the variability in codend size selection. On the contrary, this would need a codend construction where the mesh geometry is kept constant during fishing, thus providing a new engineering challenge for the development of commercial trawl gears.
Original languageEnglish
Title of host publicationProceedings of the Fifteenth International Workshop on Methods for the Development and Evaluation of Maritime Technologies
EditorsSascha Kosleck, Karsten Breddermann
Number of pages10
Place of PublicationOstseebad Kühlungsborn, Germany
PublisherMenzel-Verlag
Publication date2023
Pages61-70
ISBN (Electronic)978-3-946694-06-9
Publication statusPublished - 2023
Event15th international Workshop on Methods for the Development and Evaluation of Maritime Technologies - Rostock, Germany
Duration: 13 Sept 202215 Sept 2022
Conference number: 15

Workshop

Workshop15th international Workshop on Methods for the Development and Evaluation of Maritime Technologies
Number15
Country/TerritoryGermany
CityRostock
Period13/09/202215/09/2022

Keywords

  • Codend size selectivity
  • Fixed mesh openness
  • Diamond-mesh
  • Square-mesh
  • Mesh opening angle

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