| Following the trials conducted in 1958/59 by German trawlers, the I.S.T.P.M. tested for the first time, in 1960, on the Roselys, a 120 CV oceanographic research vessel, a pelagic trawl using a boat equipped with a headrope sounder. The trawl was a double panel trawl with an opening perimeter of 500 80 mm meshes. The lateral opening was made through hydrodynamic Süberkrüb doors of 1,7 sq. meters and 130 kg. Finally, an Atlas Werke netzsonde whose oscillator was set on a platform towed behind a headrope, was transmitting information about the opening and sinkage depth of the trawl to the bridge. The cable only had one conductor and the answer was transmitted through the water. Since then, new cables with two coaxial conductors have been used and results are... |
