Scanmar of Norway are working on a prototype for bottom sensing which they believe is so good that patents are being applied for. Part of their work has been on board Norway''s flagship research vessel the G.O. Sars and Scanmar say the scientists refused to let them take the trial sensors away -- too good to lose.
"Researchers have been asking us for 20 years to produce a bottom contact sensor that warns when the bottom gear is lifting...[but]... we have never come up with anything that satisfied the researchers' needs, nor ours, for precision.
The new type of door sensor measures the roll and pitch angles and also shows the doors' stability. During the research trials, "It was also very obvious when the doors hit bottom: the angles changed and instability increased," a company statement said.
Once the doors had settled, the angles changed and stability increased again." Under tow, change in the door distance could be seen immediately...[and] the door distance never varied by more than 2-3 metres, but you could still see a clear correlation between the doors' angle and stability and the distance between the doors." While the prototype is primarily a sensor for marine research Scanmar say they believe both trawlers and Scottish seiners could make good use of it.
Revolutionising trawling
It means you can see "immediately" "when the trawl gear has reached bottom and normal towing can begin, and see if the trawl gear is losing bottom contact or whether fluctuations shown by Scanmar's Trawleye are due to an uneven bottom (especially when registered by the narrow beam Trawleye). It also registers how hard the bottom gear is pressing on the bottom.
The new sensors that show the depth of the trawl doors and the waterflow in the tunnel mean that the angle/bottom contact on the trawl doors, and bottom contact on the trawl gear, might well turn out to be two of the most important sensors for trawling in the future (and the bottom contact sensor also for Scottish seining). They are hoping to produce a "total package that will revolutionise trawling".
