Twin Rig Trawl - Sole twin rig

Alternative names

  • twin trawl, sole twin rig,

Summary

This is a method used by smaller vessels to target Dover sole. It involves towing two small trawl side by side. The rig is spread using a set of trawl doors on the outside wings and a single steel frame attached to the two inside wings. The trawls are very close behind the trawl doors as it is known that sweeps and bridles have very little effect on herding Dover sole

Environmental impact

Sole nets have a very low headline height, usually less than 750mm thereby minimising the chance of round fish bycatch. They also have a relatively narrow swept area as this gear is operated with no sweeps and brides, reducing herding of unwanted roundfish. They help to make this rig good for species selectivity only really targeting the non herding demersal species that live very close to the seabed such as Dover sole. This gear has relatively little seabed impact as it does not cover a wide area of seabed (no sweeps or bridles), the trawl doors and centre skid used are small and lightweight resulting in minimal seabed penetration and abrasion. The gear is generally used in shallow water with muddy substrates where there is frequent natural disturbance of the seabed from wave and current interaction.

Other information

In this version of multi rig trawling two (twin rig) or three (triple rig) standard sole nets were rigged to be towed side by side. The two trawl doors are fitted to the outer wings of the trawls with the inner wings being supported by a triangular frame that is a similar height to the trawl doors. In the triple rig arrangement two of these frames are used each side of the centre net and on the inner wing ends of the two outer nets. The headlines of the trawls are attached to the top of the trawl door or skid and the footrope attached to the bottom of the trawl door or skid. As there are no floats on the headline, the height of the trawl is set by the maximum height of the trawl doors and skids. Only very short bridles are used between the nets and trawl doors and skids as the main target species, Dover sole does not react to the herding effect of sweeps and bridles.

These two rigs are towed using a standard two barrelled trawl winch with two warps that split into four split warps approximately 20 to 25 metres ahead of the trawl doors. The vessels using this type of rig in UK are usually less than 14 metres in length using two or three trawls, each one being between 12 and 20metres in length with a height of less than 0.8 metres. Many fishermen still prefer to use the older style of flat wooden trawl doors with this rig but some are using the more modern foil style of trawl doors. Despite the gear set up appearing to be complicated many of the vessels are operated single handed or with only a skipper and crewman onboard.

Documents

Gear classification

Main target species (UK)

  • Dover Sole
  • Rays
  • Skates

Possible bycatch

  • Immature round fish
  • Juveniles of the target species