Can pulse trawling reduce the mechanical impact on the benthic ecosystem in the bottom trawl fishery for sole?

In the beam trawl fishery for sole in the North Sea, the twin beam trawl has dominated the fishery since the 1960s. Beam trawlers used heavy gear with tickler chains to chase sole out of the sea bed. The fishery is criticised for the mortality imposed on benthic invertebrates, the adverse effects on the sediment structure and on the high energy consumption. Since 2010, a number of vessels has switched to the economic more profitable pulse trawling technique which uses electrical stimuli to immobilise the target species. Because electric fishing is illegal in the EU, the pulse trawlers operate under a temporary derogation. In this paper we present the results of the recent studies to the effects of pulse trawl and tickler chain beam trawls on the benthic ecosystem carried out in the FP7-project BENTHIS. We compared changes in infauna in two controlled fishing experiments with a commercial tickler chain and pulse trawl, measured the penetration depth of the gear using multi-beam and sediment profile imaging. The empirical results are compared to model estimates of the penetration and sediment re-suspension. Finally, the results are integrated in a recently developed quantitative framework to assess the impact of bottom trawls on the benthic ecosystem.