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Pulse trawling versus traditional beam trawling

Published on: June 12, 2018

In recent years, the North Sea beam trawl fishers targeting sole have successfully shifted to electrical stimulation using pulse trawls. The electrical stimulus invokes a cramp response which immobilise the fish. In collaboration with the fishing industry BENTHIS conducted two field experiments to measure the penetration of the gear in the seafloor and direct mortality induced by the traditional tickler chain beam trawl compared to the novel pulse trawl.

The results show that the pulse trawls are lighter and are towed at a slower speed (5 knots or less) than the traditional tickler chain beam trawls (towing speed between 6 and 7 knots). As a consequence, the pulse trawl has a smaller annual footprint (km² fished per year). Pulse trawls furthermore show a reduced penetration into the sediment and a reduction in the bycatch of benthos.

And what about the mortality of benthos in the trawl path? For now, no significant differences could be found, due to low sample sizes. That means that more comparisons are needed on a larger scale to be able to detect any differences. An important point is that pulse trawlers may be used in other habitats compared to traditional tickler chain beam trawls. This means that the change in fishery effort distribution over the habitats needs to be taken into account when estimating the change in impact of fishery for sole when the beam trawl is replaced by the pulse trawl. The effects of pulse on the ecosystem is currently being investigated in other studies.

Electrical stimulation may also be successfully applied in the fishery for brown shrimp to improve the selectivity and reduce the bycatch and the contact with the seafloor.

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