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Effect of sweep length on herding when semi-pelagic trawling

Two full scale tests were carried out in spring and autum 2013 to assess the effect of sweep length on herding of fish during semi-pelagic trawling for cod and haddock. The results showed that sweep length can have a significant effect on the catches.

Fixing the 450-kg chain weights right in front of the ground gear captured in up to 50% less cod and up to 60% haddock (of all sizes) than when the chain weights were fixed 45 m in front of the ground gear. These results demonstrate that at least under the conditions encountered in these trials, the sweeps have a major role on the fish herding process of the gear.

A concept for remote control of existing trawl doors, which is based on manipulating the moment balance of the trawl doors, has been designed by SINTEF. This is achieved using control lines between points on the trawl door and external lines (warps or bridles). By tensioning such lines, the orientation of the trawl door is controlled, which again is used to control the hydrodynamic forces created by the trawl door. The energy consumption of this concept is greatly reduced by changing the rigging of the trawl door to reduce its stability. A pair of 0.6 m2 Injector XF9 semi-pelagic doors are currently being instrumeted with actuators and will be tested in Hirtshals' flume tank in early 2014.

Project Information

Project duration:

02/01/2012 - 31/12/2014