Use a pulse trawl instead of a beam trawl
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
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Background information and definitions
Trawling is a method of fishing that involves pulling a fishing net (trawl) through the water behind one or more boats. A beam trawl is a type of trawl where the mouth of the net is held open by a wooden or metal beam, which can be up to 14 m long. Beam trawls can negatively impact subtidal benthic invertebrates through direct physical damage, bycatch, and alterations to the seabed (Bergman & Van Santbrink 2000). Other types of fishing methods may be less damaging to the seabed and its invertebrates. Pulse trawling is an adaptation of beam trawling which replaces tickler chains (metal chains which drag along the seabed in front of the net) with electrical drag wires that sends electric pulses into the seabed. Pulse trawls are alternative fishing methods which may potentially cause less damage to the seabed and benthic invertebrates (Despestele et al. 2018; Van Marlen et al. 2014). However, it should be noted that the use of pulse trawls is banned in many fisheries. Evidence for other interventions related to using different fishing gear is summarised under “Threat: Biological resource use”.
Bergman M.J.N. & Van Santbrink J.W. (2000) Mortality in megafaunal benthic populations caused by trawl fisheries on the Dutch continental shelf in the North Sea in 1994. ICES Journal of Marine Science, 57, 1321–1331.
Depestele J., Degrendele K., Esmaeili M., Ivanović A., Kröger S., O’neill F.G., Parker R., Polet H., Roche M., Teal, L.R. & Vanelslander B. (2018) Comparison of mechanical disturbance in soft sediments due to tickler-chain SumWing trawl vs. electro-fitted PulseWing trawl. ICES Journal of Marine Science, 76, 312–329.
Van Marlen B., Wiegerinck J.A.M., van Os-Koomen E. & van Barneveld E. (2014) Catch comparison of flatfish pulse trawls and a tickler chain beam trawl. Fisheries Research, 151, 57–69.
Supporting evidence from individual studies
A replicated, controlled study in 2011 in sandy areas in the North Sea, Netherlands (Van Marlen et al. 2014) found that pulse trawls caught fewer unwanted invertebrates compared to traditional beam trawls, but the effects varied with species. Fewer unwanted invertebrates were caught when using pulse trawls compared to using beam trawls (pulse: 142 vs beam: 177 individuals/ha). However, when sorted by groups, pulse trawls caught fewer invertebrates living on the sediments (131 vs 175) but more living inside the sediment (11 vs 2), compared to beam trawls. In particular, pulse trawls caught fewer echinoderms (82 vs 113) and gastropods (sea snails; 0.0 vs 0.1), compared to the beam trawl, similar numbers of anthozoan (0.0 vs 0.1), bivalves (0.1 vs 0.2), cephalopods (0.1 vs 0.2), and crustaceans (60 vs 64). Pulse trawls also caught 57% less total discards (non-commercial unwanted catch of invertebrates and fish) by volume (0.25 vs 0.29 basket/ha). The pulse trawl reduced the volume of commercial catch by 19% compared to the traditional trawl (0.08 vs 0.1 basket/ha). Pulse (electrical) trawling was prohibited in European fisheries in 1998, but a system of derogations set up in 2006 has allowed the practice to continue, including experimental trials. Comparison trials were conducted in May 2011 with three vessels fishing side-by-side (two boats using pulse trawls, one using traditional flat-fish tickler chain beam trawls). Catches from 33 trawls/vessel were assessed. The total discard volume was measured. Invertebrate discards were identified and counted from one subsample of total catch/trawl (35 kg basket). As of 2019, the practice has been fully banned in European waters.Study and other actions tested
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This Action forms part of the Action Synopsis:Subtidal Benthic Invertebrate Conservation