• Energy Research

At the North Sea seafloor, numerous submarine cables are positioned that connect telecommunication networks between countries. Worldwide, human activities cause most of the cable disruptions with fisheries accounting for nearly half of all reported faults. Due to a recent increase of submarine cable disruptions in the central North Sea area, Global Marine Systems Ltd. requested IMARES to investigate a possible link between these occurrences and the recent gear switch of the Dutch –demersal beam-trawlfishing fleet.

At the North Sea seafloor, numerous submarine cables are positioned that connect telecommunication networks between countries. Worldwide, human activities cause most of the cable disruptions with fisheries accounting for nearly half of all reported faults. Due to a recent increase of submarine cable disruptions in the central North Sea area, Global Marine Systems Ltd. requested IMARES to investigate a possible link between these occurrences and the recent gear switch of the Dutch –demersal beam-trawlfishing fleet.

Under the current Long Term Management Plan of North Sea herring the stakeholders are concerned that the inter-annual TAC constraint is preventing the stock from being exploited at the maximum sustainable yield. Therefore, ICES was requested by the EU and Norway to evaluate, by 31 October 2011, the impact on the performance of the plan in relation to the objectives of providing sustainable fisheries with stable yield in conformity with the precautionary approach under different harvest control rules

Under the current Long Term Management Plan of North Sea herring the stakeholders are concerned that the inter-annual TAC constraint is preventing the stock from being exploited at the maximum sustainable yield. Therefore, ICES was requested by the EU and Norway to evaluate, by 31 October 2011, the impact on the performance of the plan in relation to the objectives of providing sustainable fisheries with stable yield in conformity with the precautionary approach under different harvest control rules

In 2006, the first Dutch offshore wind farm was built 10-18 km from the shore of Egmond aan Zee by a joint venture of Nuon and Shell Windenergy. A Monitoring and Evaluation Program accompanied the plans for the construction and exploitation of this farm. The program contained plans for the monitoring and evaluation of potential ecological consequences in the Dutch coastal zone related to the wind farm and was divided in six topics, of which the topics on fish are presented in this report. Potential ecological consequences for fish were hypothesized to be linked to the introduction of new habitat, i.e. the monopiles and the scour protection surrounding them, disturbance by the operation of the wind farm (e.g. noise) and the exclusion of fisheries in the wind farm and its surrounding safety zone. To monitor and evaluate these hypothesized effects, five sub-projects performed focussing on different parts of the fish community, their spatial and temporal distribution and their behavioural aspects.

In 2006, the first Dutch offshore wind farm was built 10-18 km from the shore of Egmond aan Zee by a joint venture of Nuon and Shell Windenergy. A Monitoring and Evaluation Program accompanied the plans for the construction and exploitation of this farm. The program contained plans for the monitoring and evaluation of potential ecological consequences in the Dutch coastal zone related to the wind farm and was divided in six topics, of which the topics on fish are presented in this report. Potential ecological consequences for fish were hypothesized to be linked to the introduction of new habitat, i.e. the monopiles and the scour protection surrounding them, disturbance by the operation of the wind farm (e.g. noise) and the exclusion of fisheries in the wind farm and its surrounding safety zone. To monitor and evaluate these hypothesized effects, five sub-projects performed focussing on different parts of the fish community, their spatial and temporal distribution and their behavioural aspects.

Ecosystem effects of bottom trawl fisheries are of major concern. Although it is prohibited to catch fish using electricity in European Union waters, a number of beam trawlers obtained a derogation and switched to pulse trawling to explore the potential to reduce impacts. Here we analyse whether using electrical rather than mechanical stimulation results in an overall reduction in physical disturbance of the seafloor in the beam-trawl fishery for soleSolea solea. We extend and apply a recently developed assessment framework to the Dutch beam-trawl fleet and show that the switch to pulse trawling substantially reduced benthic impacts when exploiting the total allowable catch of sole in the North Sea. Using Vessel Monitoring by Satellite and logbook data from 2009 to 2017, we estimate that the trawling footprint decreased by 23%, the precautionary impact indicator of the benthic community decreased by 39%, the impact on median longevity of the benthic community decreased by 20%, the impact on benthic biomass decreased by 61%, and the amount of sediment mobilised decreased by 39%. The decrease in impact is due to the replacement of tickler chains by electrode arrays, a lower towing speed and higher catch efficiency for sole. The effort and benthic physical disturbance of the beam-trawl fishery targeting plaicePleuronectes platessain the central North Sea increased with the recovery of the plaice stock. Our study illustrates the utility of a standardized methodological framework to assess the differences in time trends and physical disturbance between gears.

Ecosystem effects of bottom trawl fisheries are of major concern. Although it is prohibited to catch fish using electricity in European Union waters, a number of beam trawlers obtained a derogation and switched to pulse trawling to explore the potential to reduce impacts. Here we analyse whether using electrical rather than mechanical stimulation results in an overall reduction in physical disturbance of the seafloor in the beam-trawl fishery for soleSolea solea. We extend and apply a recently developed assessment framework to the Dutch beam-trawl fleet and show that the switch to pulse trawling substantially reduced benthic impacts when exploiting the total allowable catch of sole in the North Sea. Using Vessel Monitoring by Satellite and logbook data from 2009 to 2017, we estimate that the trawling footprint decreased by 23%, the precautionary impact indicator of the benthic community decreased by 39%, the impact on median longevity of the benthic community decreased by 20%, the impact on benthic biomass decreased by 61%, and the amount of sediment mobilised decreased by 39%. The decrease in impact is due to the replacement of tickler chains by electrode arrays, a lower towing speed and higher catch efficiency for sole. The effort and benthic physical disturbance of the beam-trawl fishery targeting plaicePleuronectes platessain the central North Sea increased with the recovery of the plaice stock. Our study illustrates the utility of a standardized methodological framework to assess the differences in time trends and physical disturbance between gears.