Multi Rig Trawl - more than four nets

Summary

A method of towing several otter trawls side by side. As many as 12 trawls has been experimented with by some fishermen in Denmark. The idea of multiple nets is to target a wide area of seabed with no increase in gear drag. This method is used to target bottom living species and nephrops.

Environmental impact

Any of the selective measures for a single trawl can be included in a quad rig trawl to improve its selectivity and reduce discards. Although this fishing method may appear dramatic it can be quite environmentally friendly. Several scientific trials of quad rig have evidenced that it catches much less round fish bycatch than a single or twin rig on the same fishing grounds. Used properly it should use less fuel for the same financial returns. Despite having many more nets the overall swept area and interaction with the seabed is usually less than or similar to that of a comparable twin rig vessel. the net used in this rig are very small with a very low headline height that restricts the number of round fish entering the trawl making them a good choice to target bottom living species without much by catch of round fish.

Other information

Multi rig trawling in its many forms is used throughout the world to target bottom living demersal fish and shell fish. If used properly when compared to the alternative fishing methods multi rig trawling should be;

A – More efficient in species selection due to the lower headline height of trawls.

B – It should use less fuel due to decreased drag of gear.

C – It should cut round fish discard rates

D – In a fishery with effective management multi rig can prove to be a very efficient method of trawling.

The whole concept of multi rig trawling is to get the gear to cover a wide area of seabed with less drag (less fuel usage). It is usually used to target bottom living fish and shellfish that do not react well to being herded into the trawl by the sweeps and bridles, for this reason the length of sweeps and bridles between the trawl doors and the nets is much less than in a single or twin rig set up. The overall spread of the multi rig gear is not any more than that of an equivalent twin rig but it will be more efficient for catching nephrops etc.

As the number of trawls increases the size of each is scaled down considerably. Compared to one single trawl, in a rig with four or more nets the trawls used would be scaled down to about 30% of a typical single trawl towed by the same vessel. This results in each trawl being lighter on the seabed and the headline height of the trawl being much less therefore it does not catch many of the higher swimming species such as haddock and whiting and can be classed as extremely species selective in operation in relation to higher swimming species.

The use of more than four nets has not grown at the same rate that twin rig did in the 90s or more recently quad rig.

Although the Danish fleet have experimented with as many as twelve nets side by side, there are only a few vessels now rigged to use six or more nets.

In certain areas there are restrictions on the use of multi rig or anything with more than two nets.

Gear classification

Main target species (UK)

  • Monkfish
  • Nephrops

Possible bycatch

  • Juveniles of the target species
  • Benthos