MLD off-bottom trawl doors

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Preliminary assessment of MLD off-bottom trawl doors in the Irish Nephrops fishery


Key Findings
  • Doors remained off the seabed for 89% of haul times
    Wingend spread was reduced but no reduction in swept area
    Further work needed on optimisation of off-bottom doors with different trawl configurations

Bord Iascaigh Mhara, Ireland’s Seafood development Agency, has been working with the Irish fishing industry to develop more energy efficient fishing gears.

As outlined in BIM’s recent carbon footprint report, fuel use and carbon emissions are relatively low in the seafood sector, but the Nephrops fishery is on the higher end of the scale in terms of energy use.

BIM says that work is ongoing on the development of more hydrodynamic trawls and modified rigging ahead of the nets which improve energy efficiency. BIM is also testing off-bottom doors. Doors are typically responsible for around 30% of gear drag and lifting them off the seabed has major potential to significantly reduce drag and energy use.

The model tested by BIM researchers was provided by MLD from Denmark. MLD develop high-aspect trawl doors which can be controlled from the wheelhouse primarily for the pelagic industry but have recently developed a 1.75 m2 prototype off-bottom version for the demersal sector. Here, we conducted preliminary trials on MLD doors in the Irish nephrops fishery.

The Doors were tested over five-days onboard the MFV ‘Emerald Shore’, a 16.89-metre vessel targeting nephrops in the western Irish Sea in October and December 2022. The ‘Emerald Shore’ was toeing Pepe Half Quad Trawls whichhad a  headine length of 37-metres and an estimated headline height of approximately one-metre.

MLD off-bottom trawl doors

The result of the research found that the MLD doors remained off the seabed for around 90percent of deployment periods and fuel consumption was down 8 percent compared with conventional doors, even though the skipper increased his towing speed from 2.5 kts up to 3 kts to keep the KLG trawl doors off the bottom. Recent trials of the MLD doors in Denmark showed an 18% reduction in fuel compared with standard doors in a demersal trawl fishery when both sets of doors were towed at 3 kts.

The report found that, despite some challenges around optimising the MLD system and gear performance over a short time period, the trial demonstrated that off-bottom doors have potential to improve energy efficiency in the Nephrops fishery. Given the potential benefits, a number of door manufacturers are stepping up research in this area and BIM plans to continue working with the fishing industry on testing and developing options in the Irish Nephrops fishery.

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