Historical development
Around 1983, Danish fishermen developed a twinrig system in cooperation with the Danish Fisheries Institute.

At the same time as the Danes developed the twinrig method, interest in this method of fishing was growing among small fisheries on the coast of England and Scotland. The concept of twinrigging was applied to catch lobster and sole in areas where the bottom is unsuitable for beam trawlers. It soon became clear that twinrigging is an excellent option for vessels with relatively low power.

Dutch interest in twinrigging has been reluctant and has only been roused since 1999. Dutch shipowners with cutters that have relatively low engine power compared to large beam trawlers find twinrigging worthwhile.

Fishing technique
In the twinrigging or twin-trawling fishing technique, two trawl nets are pulled/used simultaneously behind the vessel. The two nets are linked together during fishing. The two nets are towed by means of three fishing lines. The two outer fishing lines end at a shearboard. The middle line ends at the centre weight which is a kind of large cone. The shearboard and the centre weight drag along the ground, creating clouds of dust that startle the fish.

From the shearboard, two cables run to the ends of the bottom and the top of each net, totalling four cables. The dust clouds cause the fish to swim towards the centre and the cables cause the startled fish to swim towards the correct position and into the nets.

1. Shearboard causing dust clouds when dragging over the bottom.
2. Fishing line to the centre weight
3. Centre weight causing dust clouds when dragging over bottom.
4. Two cables to bottom and top of net.

Speed and weather conditions
The best catches take place in daylight and clear water. When the water is murky, the dust clouds created by the gear are not effective enough to startle the fish and make them swim into the nets. So twinrig fishing can mainly only be done under favourable weather conditions or in areas of the sea where turbulence in the water is little or nonexistent. Speed is also an important aspect with twinrigging. Twinrigging at a low speed is effective because when fishing at too high a speed, there is a risk that the fish may avoid the net and cables and shoot under or over them.

Sustainability
Twinrigging is of interest to owners of cutters with low engine power. The so-called Euro cutters. A modern Euro cutter already has a net roll on the stern and the cost of adaptation is still manageable compared to a large beam trawler that has to be adapted to twinrig. Twinrig fishing is well publicised because it is sustainable. Twinrigging requires significantly less fuel because less propulsion power is needed. The lower speed also ensures that the fish end up in the nets less stressed and mostly still have its mucus layer when hauled on board and show less to no damaged spots on the skin. Bycatch and undersized fish (discards) are low. Twinrig fishing offers good quality fish which is rewarded at the auctions with a good price.

Photo: © Ecomare, Oscar Bos