The contact drag of towed demersal fishing gear components

Finbarr G. O'Neill, K. J. Summerbell, Ana Ivanovic

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7 Citations (Scopus)
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The contact demersal towed fishing gears make with the seabed can lead to penetration of the substrate, lateral displacement of the sediment and a pressure field transmitted through the sediment. It will also contribute to the overall drag of the fishing gear. Consequently, there can be environmental effects such as habitat alteration and benthic mortality, and impacts to the fuel efficiency of the fishing operation which will affect emissions of nitrogen oxides, sulphur oxides and greenhouse gases such as CO2. Here we present the results of experimental trials that measure the contact drag of a range of elements that represent some of the components of towed demersal gears that are in contact with the seabed.

We show that the contact drag of the gear components depends on their weight, geometry, the type of sediment on which they are towed and whether they are rolling or not. As expected, the contact drag of each gear component increases as its weight increases and the drag of fixed elements is greater than that of the rolling ones. The dependence on aspect ratio is more complex and the drag (per unit area) of narrow cylinders is less than that of wider ones when they roll on the finer sediment or are fixed (not permitted to roll) on the coarser sediment. When they roll on the coarse sediment there is no dependence on aspect ratio. Our results also suggest that fixed components may penetrate the seabed to a lesser depth when they are towed at higher speeds but when they roll there is no such relationship.
Original languageEnglish
Pages (from-to)39-52
Number of pages14
JournalJournal of Marine Systems
Early online date1 Sept 2017
Publication statusPublished - Jan 2018

Bibliographical note

This study was funded in part by Fisheries Innovation Scotland, project FIS02, and by the FP7 project BENTHIS (312088). It does not necessarily reflect the views of the European Commission and does not anticipate the Commission's future policy in this area.


  • Trawl fishing gears
  • Environmental impact of fishing
  • Contact drag
  • Benthic impact of fishing


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