Grid Sensor
The aim was to fish for shrimp in fields with many small fish, without taking the latter as by-catch. In many countries there are regulations on trawling, and in some areas it is mandatory to use a grid in the cod end.
Use of the GridSensor
The Scanmar GridSensor was developed to show the precise water flow through the grid, and the grid’s angle. The angle gives a good indication of the filling in the cod end, and of whether the trawl has twisted.
Water flow
Water flow through the sorting grid is the most important observation. Quite often the grid becomes blocked by skate, seals, sharks, stones and more. In some seasons, big swarms of jellyfish seal the meshes in the cod end and prevent water from flowing out. In these cases it is necessary to end the haul.
Grid angle
Changes to the angle give a good indication of the catch volume at any time, and the logging curve also shows where the influx was greatest.
With shrimp, and fish without a swim bladder, the cod end sinks as it fills up. It is therefore usual to start with an angle above 50 degrees and to finish towing when the angle approaches 37 or 38 degrees.
