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  • Two functions: TrawlSpeed and Symmetry

  • The TrawlSpeed function measures the speed of the waterflow into the trawl opening

  • The Symmetry function measures the side currents into the opening

  • The sensor is used to assure optimal towing speed and trawl symmetry to reduce fuel costs and loss of catch

Flow Sensor

Flow Sensor (Speed/Symmetry)

Scanmar has delivered TrawlSpeed / Symmetry sensors for 20 years and they are absolutely indispensable for those who have begun to use them. More and more open their eyes to how important this combination is for efficient fishing, giving full control over the trawl geometry while simultaneously assuring optimal towing speed.

Flow Sensor on the headline

All trawls have an optimal water flow rate. This varies according to design, mesh size, thickness of purse line, knots, age of materials, etc. Because of underwater currents, the trawl speed will deviate from the vessel’s GPS speed and must be compensated. If the trawl moves too fast through the sea, a “bucket effect” will be created in the trawl, forming an area of pressure ahead of it. If towing is too slow, this will give fish an opportunity to escape, especially large ones, with their greater swimming power and endurance

Trawl Speed


The Trawl Speed function helps you adjust to changes in water flow and maintain the correct towing speed.

The Symmetry function shows if there is a side current into the opening leading to a skewed trawl, which is very ineffective. Side currents can be caused by wrong warp lengths, underwater currents and towing in hillsides. Unless this is corrected with differing warp lengths, the trawl will not be symmetrical to the water flow. This will in turn lead to the meshes being closed on one side and wide open on the other, allowing current and fish to pass through the side panel.