Comparison of mechanical disturbance in soft sediments due to tickler-chain SumWing trawl vs. electro-fitted PulseWing trawl

Jochen Depestele*, Koen Degrendele, Moosa Esmaeili, Ana Ivanović, Silke Kröger, Finbarr G. O’neill, Ruth Parker, Hans Polet, Marc Roche, Lorna R. Teal, Bart Vanelslander, Adriaan D. Rijnsdorp

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

28 Citations (Scopus)

Abstract

Tickler-chain SumWing and electrode-fitted PulseWing trawls were compared to assess seabed impacts. Multi-beam echo sounder (MBES) bathymetry confirmed that the SumWing trawl tracks were consistently and uniformly deepened to 1.5 cm depth in contrast to 0.7 cm following PulseWing trawling. MBES backscatter strength analysis showed that SumWing trawls (3.11 dB) flattened seabed roughness significantly more than PulseWing trawls (2.37 dB). Sediment Profile Imagery (SPI) showed that SumWing trawls (mean, SD) homogenised the sediment
deeper (3.4 cm, 0.9 cm) and removed more of the oxidised layer than PulseWing trawls (1 cm, 0.8 cm). The reduced PulseWing trawling impacts allowed a faster re-establishment of the oxidised layer and micro-topography. Particle size analysis suggested that SumWing trawls injected finer particles into the deeper sediment layers (4 cm depth), while PulseWing trawling only caused coarsening of the top layers (winnowing effect). Total penetration depth (mean, SD) of the SumWing trawls (4.1 cm, 0.9 cm) and PulseWing trawls (1.8 cm, 0.8 cm) was
estimated by the depth of the disturbance layer and the layer of mobilized sediment (SumWing ¼ 0.7 cm; PulseWing trawl ¼ 0.8 cm). PulseWing trawls reduced most of the mechanical seabed impacts compared to SumWing trawls for this substrate and area characteristics.
Original languageEnglish
Pages (from-to)312-329
JournalICES Journal of Marine Science
Volume76
Issue number1
DOIs
Publication statusPublished - 2019

Keywords

  • beam trawl
  • biogeochemistry
  • habitat impacts
  • Particle size distribution
  • penetration depth
  • pulse trawl
  • seafloor integrity
  • sediment resuspension

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