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Fishery techniques   Beam-trawl fisheries   Pulse trawling   

Pulse trawling

Flatfish are often halfway buried in the sea bottom. That means that fishermen need to scare the flatfish in order to get it into its net. The normal way is to use chains or mats with chainwork, which are pulled through the sea floor in front of the net. This process costs lots of energy and damages benthic life. With pulse trawling, the tickler chains are replaced by drag wires through which electric impulses are sent. The fish caught are not killed or paralyzed by the electriciy, but are only shaken up. Fuel consumption is 20 to 40% lower than with tickler chains and there is less disturbance of the bottom, fewer by-catch and a greater yield.

  • Pioneers
    Pulskor, Ecomare, Pamela Lindeboom

    The system was invented by Piet Jan Verburg from Colijnsplaat (Zeeland) in 1992 and was purchased by the ministry for Fisheries in 1998. However, a European ban on electric fishing hampered any importation of this new system. Experimenting was allowed. Between 2005 and 2007, the UK 153 was equipped with two pulse nets to test the system in the field. In 2006, the UK153 fished with two pulse trawls to test the system in practice. The TX 68 then took over the pioneering role.

  • Progress in the pulse fishing project

    The European ban on pulse fisheries is eased. In September 2010, the Dutch Minister for Fisheries decided that no more than 5% of the Dutch fleet is allowed to fish with pulse wires. Despite the limitation, that meant quadrupling the pulse trawling fleet, since only a few licenses had been issued till then. The new pulse trawlers catch primarily flatfish, often with the pulse wires attached to a sumwing instead of a beam trawl. The sumwing is a drifting wing with nets. Furthermore, three shrimp fishermen also want to replace their chains with pulse wires.

  • Results

    The test with the pulse trawl was reasonably successful. Ships used less fuel since they didn't have to pulled heavy chains through the sea floor. It was possible to save more than 40%. According to the fishermen, sole reacted well to the electric pulses. 15-20% more were caught than with the traditional beam trawl. Turbot was also easy to catch with the pulse trawl. However, plaice reacted worse. In total, less fish was caught using the new method. However because the fish often left the net less damaged and were therefore better quality, they eventually produced a slightly higher price at the market.

  • Customize: less bycatch

    The pulse trawl fishermen can control what sort of fish they catch using a button. The amount of tension in the wires influences the size of the fish caught. Greater tension catches larger fish. Therefore, there is less bycatch of undersized fish. And what still is unintentionally caught usually survives the ordeal, which was often not the case with the traditional beam trawl with tickler chains. In addition, 50% fewer benthic animals, such as crabs and starfish, and 20% fewer buried shellfish are caught. When fishing with tickler chains, for every kilogram of commercial fish caught, 1 or more kilograms of other fish and marine fauna are thrown dead overboard.