The future is in controllable trawl doors, according to Torben Søndergaard at MLD, which has been developing its high tech systems in the Danish port of Esbjerg, initially for pelagic fisheries, and now also for groundfish.
‘There are now thirty vessels using our doors and the experience we have built up now totals around 5000 fishing days,’ he said, commenting that their market has so far been primarily around the North Atlantic, although there are now MLD doors in use in the US.
‘We also have a Danish user now, which took a while. Asbjørn is now using our doors, and we keep adding new customers. We also have a pair on Svend C in Greenland that they are using mainly for catching their mackerel quota – and the skipper told us that after using these he would never go back to regular doors. It looks like we are doing something right – and steerable doors are clearly what the fishing industry wants,’ he said.
The fact that the doors are adjustable during a tow allows them to be optimised for the gear and fishing conditions, although this doesn’t mean that MLD’s doors are an off the shelf product. There’s a process of matching each set of doors to the fishing vessel, taking into account the size, towing power and the fishing gear, and each set is adapted to fit the stern section of the trawler using them.
There are standardised components and structures, and this enables MLD to customise doors around this basic framework, which means doors can be delivered within just four weeks, and this comes with all the guidance a new user needs.
‘In Scotland we have doors on the new Altaire, which they are looking forward to making full use of on the mackerel fishery this year when the fish are high in the water, and we supplied pair of doors to Grateful last year, which they started using in the autumn.’
Although the preference on board Grateful was for a highly stable parallel rig, this also required the full force of the flaps.
‘We recommend a V- or an M-rig, as this is more responsive, and William Whyte switched to the M-rig. Then he found that the doors were still stable, but were also much more responsive and only 15% flap adjustment was needed to control the doors during a tow.’
Going for groundfish
MLD is taking part in this year’s Scottish Skipper Expo, and as well as its success with pelagic trawl doors, the company is also promoting the work it has been doing to develop steerable systems for smaller vessels fishing on groundfish – for which there’s a sizable market with the Scottish fleet.
The 7 square metre demersal doors that MLD has been trialling on board Norwegian trawler Molnes have shown that the technology does what is expected of it, with the doors kept at a consistently steady distance of 5 metres above the seabed.
‘This was fishing for saithe, with 19 tows totalling 65 hours for these trials. The skipper said that his catch rate was the same as he would expect with his standard trawl doors, but the doors also had practically zero ground contact (99.90% off the bottom) and this has implications for fuel consumption. This is very relevant for the Scottish fleet, and we are expecting to scale down these doors to smaller sizes that are suitable for medium-sized whitefish trawlers,’ Torben Søndergaard said.
