Scanmar is one of a number of companies which have tried for several decades to offer a system which could tell a skipper if his gear was loosing contact with the seabed.
One solution was a weight at the end of a wire carrying a customised catch volume sensor. Unfortunately the sensor was activated underneath the bottom gear - after the fish had escaped. The weight could also hit someone on deck when hauled in!
The commonest reason for the bottom gear losing contact has been one or both trawl doors losing bottom contact. Scanmar, building on its Trawleye (trawl sounder), has now attacked the problem in an entirely new way, by developing the Angle Sensor. This shows instantaneously if the doors have lost, or are about to lose, bottom contact. In practice, if the trawl is correctly rigged, there will be good bottom contact as long as the doors are working correctly.
In conjunction with a Trawl Speed Sensor (which also shows symmetry) or a symmetry sensor, an Angle Sensor on the doors provides a solution that offers the best possible guarantee that fish are not escaping underneath the trawl.
So in future, the focus needs to be on the trawl doors - when they have bottom contact, the trawl has bottom contact!
