Electric fields in marine fishing

Electric fields can scare, attract or stun fish. By incorporating electric fields in fishing gears these reactions can be used to increase catching power. The results are presented of a trawling experiment in which an electric stimulus was used to increase the capture rate of Nephrops norvegicus, a mud-dwelling crustacean which spends a large proportion of its time in deep burrows, safe from capture. Several engineering problems were encountered in producing a robust electrical system to develop the necessary electric fields. A power transmission cable supplied energy from the towing vessel to a net-mounted, high-current, pulse generator feeding an electrode array. The high conductivity of sea water required a high, instantaneous, power output from the pulse generator to develop an effective field between the electrodes. Equipment on fishing gear is subjected to severe mechanical stresses, and the choice of fishing gear suitable for electrical fishing, design of electrode array and pulse generator, and handling of the power cable are discussed.