Working Group on Electrical Trawling (WGELECTRA)
The Working Group on Electrical Trawling (WGELECTRA) works on improving knowledge of the effects of electrical or pulse fishing on the marine environment. At the 2020 meeting, the working group considered the Scottish Ensis fishery, ongoing work on shrimp pulse fishery study and analysed the possible contribution of pulse trawling to reducing or increasing the ecosystem/environmental impacts of the North Sea sole fishery and its fuel consumption.
Substantial efforts were invested during the last 10 years to examine the effect of pulsed currents at the individual level on a range of species, species groups and life stages. Exposure to the pulsed bipolar current (PBC), used in pulse trawling for sole, does not result in direct mortality in fish and invertebrates, but may cause spinal injuries in fish. Pulse induced injury rate is low (<=1%) in the twelve fish species studied and population level effect will be negligible. Injury probability in cod is 36% and seems to decrease in small cod. The population level consequences are considered negligible. Adverse effect on electroreceptive species is unlikely because they are sensitive for low frequency direct current and not to high frequency PBC. Non-lethal effects are considered unlikely due to low exposure. No adverse effects (mortality or lesions) were found for the benthic invertebrate species exposed to the sole pulse, and animals returned to normal behaviour less than one hour after exposure. This made any long-term ecological effect unlikely. The low exposure probability and short duration implies no chronic exposure to pulse stimuli.
Pulse trawling has less mechanical impact on the benthic ecosystem than conventional beam trawling. The lower towing speed of pulse trawls led to reduced mobilization of sediments, and resulted in a smaller footprint and a reduced surface area swept when exploiting the sole quota. The replacement of tickler chains by electrodes reduced the depth of disturbance of the trawl and likely reduced the average mortality imposed on benthic invertebrates.
Although no specific experiments have been carried out on Natura 2000 species, the available knowledge suggests that the probability of exposure is likely to be (very) low. Natura 2000 habitats will have been exposed less by pulse trawls compared to conventional beam trawls.
CO2 emissions of pulse trawlers are lower than those of conventional beam trawlers due to an estimated reduction in fuel consumption by ~50% per unit of sole quota and ~20% per unit of total landings.
Pulse trawls catch, per hour, more sole and less plaice and other species and can contribute to a reduction in the bycatch of undersized fish (discards) and benthic invertebrates. Pulse trawling does not impose a risk to the sustainable exploitation of sole if the stock is well managed, although an increase in local fishing pressure was observed in the southern North Sea following introduction of the pulse trawl.
Published under the auspices of the following ICES Steering Group or Committee